early cambrian trilobites from angorichina, flinders ranges ... - BioOne

J. Paleont., 81(1), 2007, pp. 116–142 Copyright 䉷 2007, The Paleontological Society 0022-3360/07/0081-116$03.00

EARLY CAMBRIAN TRILOBITES FROM ANGORICHINA, FLINDERS RANGES, SOUTH AUSTRALIA, WITH A NEW ASSEMBLAGE FROM THE PARARAIA BUNYEROOENSIS ZONE JOHN R. PATERSON

AND

GLENN A. BROCK

Centre for Ecostratigraphy and Palaeobiology, Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia, ⬍agnostid@hotmail.com⬎, ⬍gbrock@els.mq.edu.au⬎ ABSTRACT—Trilobites from the Lower Cambrian succession at Angorichina in the eastern Flinders Ranges, South Australia, are described. Silicified material from the Mernmerna Formation reveals the presence of a new assemblage from the Pararaia bunyerooensis Zone, including the eponymous species, Yorkella aff. australis, Eoredlichia sp., Redlichia sp., and the new species Wutingaspis euryoptilos and Yunnanocephalus macromelos. Trilobites of the Pararaia bunyerooensis Zone show a strong affinity with those from the Yu’anshan Member of the Heilinpu Formation in Chengjiang and Jinning Counties, Yunnan Province, southwest China. The Pararaia bunyerooensis Zone is correlated with the Yunnanocephalus Assemblage subzone (upper Eoredlichia–Wutingaspis Zone) of the Chiungchussuan (⫽Qiongzhusian) Stage of China. Additional trilobites from Angorichina include Elicicola calva from the Wilkawillina Limestone, Estaingia occipitospina (Jell) new combination from the Oraparinna Shale, and Redlichia guizhouensis Zhou from the Wirrealpa Limestone. Australian Early Cambrian trilobite biozonation is reviewed, with discussion of distinct assemblages within the Pararaia janeae Zone that have the potential for zonal subdivision, and evidence to support the placement of the northern Australian Ordian/Early Templetonian Stage within the late Early Cambrian. A possible paedomorphic lineage between Pararaia bunyerooensis and P. janeae is proposed. Adult specimens of P. janeae retain juvenile characteristics of the progenitor P. bunyerooensis. Retardation in onset of maturity in P. janeae resulted in the attainment of a larger adult size than in P. bunyerooensis, indicating the former species evolved via neoteny.

INTRODUCTION

trilobites were first described from the Flinders Ranges over a century ago (Etheridge, 1905), yet there remains a dearth of literature on the abundant and diverse faunas of this region. Early taxonomic works include those of Etheridge (1905, 1919) and Walcott (in Howchin, 1920). Daily (1956) provided the first significant biostratigraphic scheme for the Cambrian succession in South Australia when he established 12 informal ‘‘faunal assemblages’’ that have subsequently been used for intra- and intercontinental correlations for many years. Unfortunately, Daily provided no formal taxonomic treatment of the largely unpublished faunas, nor did he include any precise stratigraphic ranges of the diagnostic taxa. More recently, Jell (in Bengtson et al., 1990) provided the most comprehensive study to date on the Early Cambrian trilobites of South Australia. Jell recorded 18 genera and 32 species, many of which were left under open nomenclature, and erected four trilobite zones: Abadiella huoi (base), Pararaia tatei, Pararaia bunyerooensis, and Pararaia janeae. Other taxonomic studies of Early Cambrian trilobites from the Flinders Ranges include Pocock (1970), Jell et al. (1992), Zhang et al. (2001), and Paterson and Edgecombe (2006). In erecting the family, genera, and species of the Emuellidae, Pocock (1970) described Balcoracania flindersi Pocock, 1970 from the lower Billy Creek Formation, the type locality of which occurs at Angorichina Station. In a systematic revision of the Emuellidae, Paterson and Edgecombe (2006) regarded Balcoracania flindersi to be a junior subjective synonym of B. dailyi Pocock, 1970. Jell et al. (1992) described the conocoryphid Atops rupertensis Jell, Jago, and Gehling, 1992 from the upper Mernmerna Formation and basal Oraparinna Shale at various localities in the Flinders Ranges; this species was previously referred to as Atops sp. nov. by Jell (in Bengtson et al., 1990). In revising Chinese, Moroccan, and Australian species of Parabadiella Chang, 1966 and Abadiella Hupe´, 1953, Zhang et al. (2001) considered that specimens of Abadiella huoi (Chang, 1966) illustrated by Jell (in Bengtson et al., 1990) belong to a new species of Wutingaspis Kobayashi, 1944, W. jelli Zhang et al., 2001, and thus proposed that the Australian Abadiella huoi Zone be changed to the Wutingaspis

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jelli Zone. However, Jago et al. (2002a) subsequently contested the conclusions of Zhang et al. (2001) and advocated that the Australian species belongs to Abadiella huoi as originally assigned by Jell (in Bengtson et al., 1990). In recent years there have been several studies on the biostratigraphy, correlation, and paleobiogeography of the Early Cambrian trilobites of the Flinders Ranges and other areas of Australia, including Brock et al. (2000), Gravestock and Shergold (2001), Zang et al. (2001), Jenkins et al. (2002), and Jago et al. (2002b). This study focuses on the taxonomy and biostratigraphy of the trilobite faunas from the Lower Cambrian succession at Angorichina Station in the eastern Flinders Ranges, South Australia. Silicified material from the Mernmerna Formation reveals the presence of a new assemblage from the Pararaia bunyerooensis Zone, including the new species Wutingaspis euryoptilos and Yunnanocephalus macromelos. LOCALITY AND STRATIGRAPHY

Trilobites were collected from the Wilkawillina Limestone, Mernmerna Formation, Oraparinna Shale and Wirrealpa Limestone outcropping at Angorichina Station in the Wirrealpa area of the eastern Flinders Ranges, South Australia. Angorichina Station is situated approximately 11 km east of Blinman and borders with Wirrealpa Station to the east and the Flinders Ranges National Park to the south. The Cambrian carbonate and clastic sediments in this area represent part of the Arrowie Basin in the Adelaide Geosyncline (Priess, 1999); a detailed sequence stratigraphic framework has been developed for the Cambrian of the Arrowie Basin (see Gravestock and Hibburt, 1991; Gravestock and Cowley, 1995; Boucher, 1997; Gravestock and Shergold, 2001; Zang, 2003; Zang et al., 2004) (Fig. 1). Specimens were sampled from measured stratigraphic sections through the Wilkawillina Limestone and Mernmerna Formation (section MMF), Oraparinna Shale (section OS), and Wirrealpa Limestone (section WL). The 60 m thick Mernmerna Formation at section MMF (including one sampled horizon in the underlying Wilkawillina Limestone, MMF/0.0) (base of section coordinates: 31⬚11⬘38.4⬙S, 138⬚52⬘28.7⬙E; map datum: WGS84), is located on the eastern side of The Bunkers, approximately 1 km south of

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PATERSON AND BROCK—EARLY CAMBRIAN TRILOBITES FROM SOUTH AUSTRALIA

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FIGURE 1—Cambrian stratigraphy and sequence stratigraphic framework of the Arrowie Basin, South Australia (modified from Zang, 2003, fig. 7). Abbreviations: SB–sequence boundary; A–Precambrian/Cambrian boundary by Daily (1972); B–Precambrian/Cambrian boundary by Mount (1993).

Balcoracana Creek (Figs. 2, 3). The Oraparinna Shale section OS (coordinates: 31⬚12⬘26.7⬙S, 138⬚52⬘38.9⬙E; map datum: WGS84) is also located on the eastern side of The Bunkers, approximately 2.5 km south of Balcoracana Creek and 1.5 km south of section MMF (Fig. 2). The Wirrealpa Limestone section WL (base of section coordinates: 31⬚09⬘21.8⬙S, 138⬚53⬘23.7⬙E; map datum: WGS84), coincides with Section 1 of Youngs (1977, 1978) at Balcoracana Creek (Figs. 2, 3).

The stratigraphy and sedimentology of the Mernmerna Formation at section MMF have been recently documented by Brock and Paterson (2004). They correlated section MMF with the Third Plain Creek Member of the middle Mernmerna Formation at Wilkawillina Gorge (type section in the Bunkers Graben) based on similar lithologies, sedimentary structures, and the occurrence of the trilobite Pararaia bunyerooensis Jell in Bengtson et al., 1990, and concluded that the middle Mernmerna Formation at section

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FIGURE 2—Geological map, showing the location of the study area and position of the MMF, OS, and WL sections.

MMF unconformably overlies the Wilkawillina Limestone and is disconformably overlain by the Bunkers Sandstone (Clarke, 1986a, 1989, 1990; Gravestock and Cowley, 1995). Further evidence to support the unconformity between the Wilkawillina Limestone and Mernmerna Formation at the MMF section includes the presence of a thin red microstromatolite horizon at the contact of these units, representing the Flinders Unconformity

(James and Gravestock, 1990; Gravestock and Cowley, 1995), in addition to the co-occurrence of the trilobite Elicicola calva Jell (in Bengtson et al., 1990) and brachiopod Askepasma Laurie, 1986 in horizon MMF/0.0 (discussed below). This indicates that a considerable hiatus exists at the MMF section with the absence - 1.2 transgressive deposits of Gravestock and Cowof sequence C ley (1995, p. 23), i.e., Second Plain Creek Member of the


FIGURE 3—Enlarged geological maps (from Fig. 2; see for key) of areas around the measured stratigraphic sections WL (1) and MMF (2); BCF–Billy Creek Formation.

Wilkawillina Limestone (Clarke, 1986b) and the Six Mile Bore and Linns Springs members of the lower Mernmerna Formation (Clarke, 1986a, 1990). The Mernmerna Formation at section MMF is dominated by interbedded black turbiditic wackestonepackstone and laminated lime silt and mud with rare sandstone beds (Fig. 4). Grain flow deposits are common and contain intraclasts, ooids, and peloids. Irregular and nodular bedding is

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relatively common and slump structures are also evident. Based on Clarke’s (1990) depositional model, the Third Plain Creek Member of the Mernmerna Formation was deposited in anaerobic - 1.2 highand dysaerobic zones of the lower slope (⫽Sequence C stand deposits of Gravestock and Cowley, 1995). The MMF section contains an abundance of silicified and phosphatic macroand microfossils, including a variety of trilobites (documented herein), the helcionellid mollusc Tannuella elinorae Brock and Paterson, 2004, in addition to other molluscs, brachiopods, archaeocyaths, chancelloriids, sponge spicules, and other enigmatic small shelly fossils which will be described in future studies. The 42 m thick exposure of Oraparinna Shale at section OS (Figs. 2, 4) is relatively thin compared to the thickness of ⬃200 m at Wilkawillina Gorge; however, little or no outcrop of this unit is typical along the eastern side of The Bunkers (P. S. Moore, 1979; Gravestock and Cowley, 1995). The Oraparinna Shale at section OS conformably overlies the Bunkers Sandstone, with the lower 38 m (true thickness) representing fissile green-, gray- and buff-colored shales with common limestone concretions containing rare trilobite and brachiopod fragments. The remaining 4 m consists of buff-colored siltstones containing abundant specimens of the trilobite Estaingia occipitospina (Jell in Bengtson et al., 1990) along with various centimeter-sized molluscs. The Edeowie Limestone Member overlies the Oraparinna Shale at section OS; the relationship between these units has been the source of much debate over the last 40 years. Dalgarno and Johnson (1962, 1965) defined the dolomitic Edeowie Limestone Member as the basal unit of the Billy Creek Formation. P. S. Moore (1979) later reassigned the member to the Oraparinna Shale. Priess (1999) reinstated the Edeowie Limestone Member as the basal member of the Billy Creek Formation based on P. S. Moore’s (1979, fig. 6) mapping, which showed that the member overlies a low-angle truncation surface in the Hawker Group. This suggests that the Edeowie Limestone Member unconformably overlies the Oraparinna Shale at the OS section. The stratigraphy and sedimentology of the Wirrealpa Limestone have been documented in great detail by Youngs (1977, 1978). The Wirrealpa Limestone is relatively consistent in thickness (105–140 m) in the Flinders Ranges, conformably overlying red beds of the Billy Creek Formation, and is conformably overlain by the micaceous shales, siltstones, and sandstones of the Moodlatana Formation (Youngs, 1977, 1978; Brock and Cooper, 1993; Gravestock and Cowley, 1995). The unit represents a transgressive-regressive carbonate sequence displaying lagoonal and ooid bank megafacies. The lagoonal facies association is characterized by lime mudstone and wavy-bedded to nodular limestone in a calcareous silty matrix, with subordinate skeletal, peloidal and oolitic beds, calcimicrobe build-ups, and stromatolite and columnar thrombolite bioherms. The ooid bank facies association predominantly consists of oolitic and oncolitic lithologies (Youngs, 1977, 1978). Section WL (Figs. 2–4) is equivalent with Section 1 of Youngs (1977, 1978) at Balcoracana Creek. This section was chosen because of its completeness, representing a ‘typical section’ of the Wirrealpa Limestone (Youngs, 1978, p. 68); it also contains an abundance of fossils, including trilobites, brachiopods, small shelly fossils, hyoliths, and stromatolites. As noted by Youngs (1978), this section shows an upward progression from mostly fine-grained carbonates, nodules, and calcareous siltstones to stromatolite bioherms and the first oolitic beds, followed by predominantly allochemical rocks with stromatolites and minor micrite beds. The upper part of the section consists of alternating thin oosparites with thicker beds of nodules in silts, and the uppermost beds are represented by calcareous green-gray siltstones that grade into the red beds of the Moodlatana Formation. Although fossils have not been formally described from this section, a few studies have documented faunas of the Wirrealpa Limestone

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FIGURE 4—Stratigraphic sections of the Wilkawillina Limestone and Mernmerna Formation (MMF section), Oraparinna Shale (OS section), and Wirrealpa Limestone (WL section) at Angorichina, showing all sampled horizons and ranges of trilobites.


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FIGURE 5—Correlation chart for the Lower Cambrian stages and trilobite zones of Siberia, China, and South Australia. Key references used for correlation: Zhang et al. (1980); Zhou and Yuan (1980); Yuan and Zhang (1981); Sokolov and Zhuravleva (1983); Rozonov and Sokolov (1984); Zhang (1985); Bengtson et al. (1990); Zhuravlev and Gravestock (1994); Zhuravlev (1995); Shergold (1997); Geyer and Shergold (2000); Zhuravlev and Riding (2001); Gravestock et al. (2001); Zhang (2003).

from surrounding areas, e.g., the trilobite Redlichia guizhouensis Zhou (in Lu et al., 1974; Jell in Bengtson et al., 1990), cyanobacterial-archaeocyathan-radiocyathan bioherms (Kruse, 1991b), and a variety of shelly fossils (Brock and Cooper, 1993). BIOSTRATIGRAPHY AND CORRELATION

Review of Early Cambrian trilobite biozonation in South Australia.⎯The Early Cambrian trilobite zones established by Jell (in Bengtson et al., 1990) were introduced as a preliminary biozonation in an effort to provide a basis for future biostratigraphic studies. Jell (in Bengtson et al., 1990, p. 14) hoped ‘‘that future work will refine this zonation, fill in the obvious gaps and test its applicability to other areas.’’ These zones have now been widely accepted and utilized in global syntheses on the Cambrian timescale (e.g., Zhuravlev, 1995; Shergold, 1997; Geyer and Shergold, 2000; Zhuravlev and Riding, 2001; Zhang, 2003), although these syntheses show considerable disparity in the correlation of the South Australian zones with other regions. Early Cambrian intercontinental correlation has been a major problem for decades; complicating factors include the high endemicity of Early Cambrian trilobite faunas related to biofacies control, paucity of biostratigraphically useful faunas in key regions, substantial hiatuses in the stratigraphic record, and inconsistencies in taxonomic nomenclature (Palmer, 1998b; Geyer, 2001). The Early Cambrian trilobite faunas from South Australia have closest affinities with those of South China, with 10 congeneric and six conspecific occurrences (Jell in Bengtson et al., 1990; described herein). Correlation of the Early Cambrian stages and trilobite zones of Siberia, China, and South Australia is presented in Figure 5.

The Abadiella huoi Zone represents the oldest zone in South Australia and contains the following species: Abadiella huoi, Elicicola calva, Yorkella australis (Woodward, 1884), Alanisia guillermoi (Richter and Richter, 1940), and Eoredlichia sp. Taxa from this zone have been recorded from the Parara Limestone at Curramulka, Horse Gully (Ardrossan), and Kulpara in the Stansbury Basin on Yorke Peninsula, from the Ajax Limestone (Mt Scott Range) and Wilkawillina Limestone (Wilkawillina Gorge, Wirrealpa Mine, and Yalkalpo-2 drillhole) in the Arrowie Basin (Jell in Bengtson et al., 1990; Zang et al., 2001; Gravestock et al., 2001). Elicicola calva also occurs in the Wilkawillina Limestone immediately below the red microstromatolite horizon of the Flinders Unconformity, which marks the contact with the Mernmerna Formation at the MMF section (Figs. 2–4). Although the biostratigraphic ranges of most species of the Abadiella huoi Zone (excluding Eoredlichia sp.) extend up into the younger Pararaia tatei Zone (Jell in Bengtson et al., 1990), the occurrence of E. calva at the base of the MMF section is taken to represent the A. huoi Zone. This is further supported by the co-occurrence of the paterinid brachiopod Askepasma in the same horizon (i.e., MMF/ 0.0). The last appearance datum (LAD) of Askepasma in the Stansbury Basin occurs at the top of the Pelagiella subangulata mollusc assemblage, which correlates with the A. huoi Zone (Gravestock et al., 2001). This confirms the suggestion by Brock and Paterson (2004, p. 136) that the Mernmerna Formation unconformably overlies the Wilkawillina Limestone at the MMF section. The South Australian A. huoi Zone correlates with the Chinese Parabadiella Zone based on the occurrence of A. huoi in both

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regions (Zhang, 1985, 2003; Jell in Bengtson et al., 1990; Steiner et al., 2001; Zhang et al., 2001). These zones correlate with the latest Atdabanian–earliest Botoman of Siberia, based on correlation of South Australian and Siberian archaeocyathan faunas (Zhuravlev and Gravestock, 1994; Zhuravlev, 1995). The Pararaia tatei Zone comprises 10 species, including four overlapping species from the older Abadiella huoi Zone (Jell in Bengtson et al., 1990). The base of the P. tatei Zone corresponds to the first appearance datum (FAD) of the eponymous species. This zone occurs in the Parara Limestone at Curramulka, Horse Gully (Ardrossan), and Kulpara in the Stansbury Basin, and in the Ajax Limestone (Mt Scott Range), Mernmerna Formation (Willochra, Wilkawillina Gorge and Yalkalpo-1 drillhole), and Wilkawillina Limestone (Wirrealpa Mine and west of Wirrealpa Springs) in the Arrowie Basin (Jell in Bengtson et al., 1990; Zang et al., 2001; Gravestock et al., 2001). Jell (in Bengtson et al., 1990, p. 16) correlated the P. tatei Zone with the Chinese Eoredlichia–Wutingaspis Zone based on the occurrence of Eoredlichia shensiensis (Chang, 1966) in both regions. These zones appear to correlate with the early Botoman (Bergeroniellus micmacciformis–Erbiella Zone) of Siberia based on the correlation of older (Abadiella huoi Zone equivalent) archaeocyathan faunas (discussed above). However, Jell (in Bengtson et al., 1990, p. 17) considered that the Pararaia tatei Zone should be considered Atdabanian based on the genera Prouktaspis Repina (in Khomentovskii and Repina, 1965), Egyngolia Korobov, 1980, and Pararaia Kobayashi, 1942 (⫽Tannuolaspis Zadorozhnaya in Zhuravleva et al., 1967, fide Jell in Bengtson et al., 1990). According to Korobov (1989) and Zhuravlev (1995), Egyngolia from Mongolia occurs together with Botoman archaeocyaths and the trilobites Binodaspis Lermontova, 1951, Erbiopsis Lermontova, 1940, Inouyina Poletaeva, 1936, Jakutus Lermontova, 1951, Kadyella Pokrovskaya, 1959, and Proerbia Lermontova, 1940, thus supporting an early Botoman age for the P. tatei Zone. The Pararaia bunyerooensis Zone has been the most poorly understood of the Early Cambrian trilobite zones of South Australia. This was largely due to its supposed low diversity, consisting of the eponym and an indeterminate redlichiid, and its limited occurrence in the Flinders Ranges. This zone has only been previously recorded from the Mernmerna Formation at Bunyeroo Creek, and from the Third Plain Creek Member of the middle Mernmerna Formation at Wilkawillina Gorge (Jell in Bengtson et al., 1990; Gravestock and Cowley, 1995). A new assemblage from the P. bunyerooensis Zone consisting of six species has now been discovered at Angorichina and is described below. The Pararaia janeae Zone has the highest diversity of all of the South Australian trilobite zones, containing 19 species (Jell in Bengtson et al., 1990). Jell (in Bengtson et al., 1990) based this zone primarily on the faunule at Bunyeroo Creek, containing the species Pararaia janeae Jell (in Bengtson et al., 1990), Hebediscina yuqingensis (Zhang in Zhang et al., 1980), Serrodiscus gravestocki Jell (in Bengtson et al., 1990), Atops rupertensis, Kootenia diutina Fritz, 1972, Estaingia bilobata Pocock, 1964, and Paleofossus? sp. For convenience, Jell extended this zone beyond this assemblage to incorporate the stratigraphic ranges of Estaingia species, i.e., E. bilobata and E. occipitospina. This included the trilobite faunas of the White Point Conglomerate and Emu Bay Shale on Kangaroo Island (Pocock, 1964, 1970; Jell in Bengtson et al., 1990; Nedin, 1995). Jell also suspected that the emuellid Balcoracania dailyi from the White Point Conglomerate was synonymous with B. flindersi from the Warragee Member of the lower Billy Creek Formation at Balcoracana Creek, Angorichina—this has now been confirmed by Paterson and Edgecombe (2006)—and thus incorporated these species into the P. janeae

Zone. This implies that the trilobites Estaingia bilobata and Balcoracania dailyi have considerable stratigraphic ranges and may be of limited biostratigraphic utility if the P. janeae Zone were to be further subdivided. The trilobite fauna from the Cymbric Vale Formation in western New South Wales, originally described ¨ pik (1975b), is considered to be of P. janeae Zone age (Jago by O et al., 1997; Paterson, 2005). There is, in fact, evidence to suggest further refinement of the Pararaia janeae Zone. A trilobite assemblage containing the species Estaingia occipitospina and Korobovia ocellata Jell (in Bengtson et al., 1990) from the upper Oraparinna Shale apparently does not overlap with the Pararaia janeae assemblage (Jell in Bengtson et al., 1990). This has also been observed in continuous stratigraphic sections through the Mernmerna Formation and Oraparinna Shale sampled by the authors in the Elder Range (personal data). Further detailed biostratigraphic work of these assemblages is needed before any future subdivision is attempted. Jell (in Bengtson et al., 1990) also documented an additional assemblage containing the trilobites Xela drena Jell (in Bengtson et al., 1990), Micmaccopsis separata Jell (in Bengtson et al., 1990), Micmaccopsis alba Jell (in Bengtson et al., 1990), Redlichia endoi Lu, 1950, and Yorkella sp. nov., referred to herein as the ‘Micmaccopsis assemblage,’ from an archaeocyathid bioherm within the upper Wilkawillina Limestone at Wirrealpa Mine, which he tentatively assigned to the P. janeae Zone. Three lines of evidence indicate the temporal separation of the Pararaia janeae assemblage and the Micmaccopsis assemblage. Firstly, the occurrence of Hebediscina yuqingensis in the Pararaia janeae assemblage permits correlation with the early Tsanglangpuan of China, based on the occurrence of H. yuqingensis in the Jiumengchong (⫽Niutitang) Formation in eastern Guizhou (Zhang et al., 1980; Peng and Babcock, 2001); the occurrence of Atops Emmons, 1844 (⫽Ivshiniellus Korobov, 1966, fide Jell et al., 1992) from the latest Aldanian (⫽early Botoman, sensu Rozonov and Sokolov, 1984) in Siberia also supports this correlation (Korobov, 1966, 1973). Secondly, the occurrence of Redlichia endoi in the Micmaccopsis assemblage allows correlation with the Chinese Palaeolenus Zone (Zhang et al., 1980; Zhou and Yuan, 1980); the Palaeolenus Zone equates with the latest Botoman Bergeroniaspis ornata Zone of Siberia based on correlation of archaeocyathan faunas (Yuan and Zhang, 1981; Zhuravlev, 1995; Zhang, 2003). Thirdly, Xela Jell (in Bengtson et al., 1990) has been described from the Lesser Himalaya in India by Jell and Hughes (1997) and is considered to be of late Tsanglangpuan (Palaeolenus Zone) age (Hughes and Jell, 1999; Hughes et al., 2005). Trilobites from younger horizons in the Early Cambrian of South Australia are rare, but include Redlichia guizhouensis from the Wirrealpa Limestone, and Onaraspis rubra Jell (in Bengtson et al., 1990) from the Moodlatana Formation. Previously, the stratigraphic range of R. guizhouensis in South Australia was poorly understood, since it had been recorded from only a single horizon in the Wirrealpa Limestone by Jell (in Bengtson et al., 1990). However, specimens are now known from a new locality (WL section) at Angorichina, which demonstrates that R. guizhouensis ranges throughout the majority of the Wirrealpa Limestone (Fig. 4). Redlichia guizhouensis occurs in the latest Lungwangmiaoan Stage in South China (Zhou in Lu et al., 1974; Yin and Li, 1978; Zhou and Yuan, 1980; Peng and Babcock, 2001), suggesting that the Wirrealpa Limestone is of similar age. Zhang (1985, 2003) and Jell (in Bengtson et al., 1990) both considered that R. guizhouensis may be a synonym of R. nobilis Walcott, 1905, suggesting that the R. guizhouensis Zone is equivalent to the R. nobilis Zone of China. Jell (in Bengtson et al., 1990) described Onaraspis rubra from the Moodlatana Formation at Wilkawillina Gorge and a locality northwest of Wirrealpa (NMVPL89). He tentatively correlated the

PATERSON AND BROCK—EARLY CAMBRIAN TRILOBITES FROM SOUTH AUSTRALIA rocks containing O. rubra with the northern Australian Ordian Stage—now regarded as part of the Ordian/Early Templetonian Stage (see Kruse et al., 2004, p. 18–19 for detailed discussion)— ¨ pik, 1968 based on the occurrence of congeners O. somniurna O ¨ pik, 1968 from central and Western Australia, and O. adusta O ¨ pik, 1968). respectively (O Previously, the Australian Ordian/Early Templetonian Stage (⫽Xystridura templetonensis/Redlichia chinensis Zone) was considered to be early Middle Cambrian (e.g., Shergold, 1996; references therein), but mounting evidence suggests that this stage should be regarded as latest Early Cambrian, based on correlation ¨ pik (1970) with the Lungwangmiaoan Stage of China. Firstly, O described Redlichia chinensis Walcott, 1905 from the Ordian of northern Australia, which allows correlation with the chinensis Zone of the mid-Lungwangmiaoan in China (Zhang, 2003). How¨ pik’s (1970) ever, Kruse et al. (2004, p. 19) have questioned O assignment to this species, since he illustrated only three specimens. Therefore, correlation of the Redlichia chinensis Zone between Australia and China remains tentative. More convincing evidence comes from the occurrence of the lingulate brachiopods Karathele napuru (Kruse, 1990) and Vandalotreta djagoran (Kruse, 1990) in the Wirrealpa and Ramsay Limestones of South Australia (Brock and Cooper, 1993; Gravestock et al., 2001) as well as several Ordian/Early Templetonian successions in northern Australia, including the Tindall Limestone in the Daly Basin, Montejinni Limestone in the Wiso Basin, and the Top Springs Limestone and Gum Ridge Formation in the Georgina Basin (Kruse, 1990, 1991a, 1998). This permits direct correlation with the Redlichia guizhouensis Zone (latest Lungwangmiaoan) of China (discussed above). These species and other associated lingulate brachiopods co-occur with trilobites such as Redlichia forresti (Etheridge in Foord, 1890), Redlichia gumridgensis Laurie (in ¨ pik, 1975a, and X. verKruse et al., 2004), Xystridura negrina O ¨ pik, 1975a (Kruse, 1990, 1991a, 1998; Kruse et al., 2004) ticosa O that are considered characteristic of the Ordian/Early Templetonian Stage. An unidentified species of Redlichia Cossmann, 1902 from the Tindall Limestone in the Northern Territory (Kruse, 1990, pl. 1) may be conspecific with Redlichia guizhouensis, but the limited number and fragmentary nature of the specimens from the Tindall Limestone precludes confirmation. The occurrence of Bathynotus holopygus (Hall, 1859) in the Ordian/Early Templetonian of central Australia (Shergold and Whittington, 2000) and the Kaili Formation of Guizhou, South China (Yuan et al., 2002), provides additional evidence to support the correlation of the Ordian/Early Templetonian with the Lungwangmiaoan. Yuan et al. (2002) record B. holopygus from the Ovatoryctocara granulata– Bathynotus holopygus Zone, which they correlate with the late Lungwangmiaoan. This species is also considered to be of late Early Cambrian (Olenellus Zone) age in Laurentia (Palmer, 1998a; Shergold and Whittington, 2000). However, until the Early-Middle Cambrian boundary is selected and ratified, correlation of the Ordian/Early Templetonian Stage with other intercontinental Early Cambrian stages remains tentative. The Pararaia bunyerooensis Zone.⎯A new silicified assemblage of this zone is described from the Third Plain Creek Member of the Mernmerna Formation at the MMF section, located on the eastern side of The Bunkers, approximately 1 km south of Balcoracana Creek on Angorichina Station (Figs. 2–4). The assemblage contains the following species, in order of appearance: Pararaia bunyerooensis Jell (in Bengtson et al., 1990), Yunnanocephalus macromelos n. sp., Yorkella aff. australis, Redlichia sp., Wutingaspis euryoptilos n. sp., and Eoredlichia sp. The base of this zone corresponds to the FAD of the eponymous species. At the MMF section, the FAD of P. bunyerooensis corresponds to horizon MMF/8.8, 5.1 m (true thickness) above the base of the section (Fig. 4).

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The trilobites from the MMF section are interpreted as being an allochthonous assemblage deposited by turbiditic conditions in a lower slope environment, following Clarke’s (1990) depositional model of the Mernmerna Formation at Wilkawillina Gorge. Taphonomic data are limited; but trilobites from the MMF section commonly occur in highly concentrated silicified ‘trash bands’ and larger sclerites (⬎10 mm) are often fragmentary. Syndepositional breakage is also evident in crushed specimens of the large helcionellid mollusc Tannuella elinorae that are preserved in silicified crusts. Thin sections reveal the presence of graded beds containing randomly oriented trilobite cuticle. Thin (⬍15 mm) mud layers contain concentrations of small, unbroken trilobite cuticle showing both convex-up and convex-down orientations parallel to bedding, indicating deposition by hemipelagic fallout from turbidity currents. This probably explains why smaller species from the MMF section (e.g., Pararaia bunyerooensis and Yunnanocephalus macromelos) are better preserved (i.e., less fragmentary). Clarke (1990) noted that most fossils from the Mernmerna Formation at Wilkawillina Gorge are severely abraded and appear to have been reworked to some extent. Clarke (1990) concluded that the vast majority of skeletal and nonskeletal allochems within the Mernmerna Formation have been transported by turbidity currents and debris flows, most of which can be identified as being platform derived. A similar taphonomic/depositional model has been proposed by Hohensee and Stitt (1989) for the Late Cambrian trilobites from the Collier Shale, Ouachita Mountains, Arkansas. Trilobites of the Pararaia bunyerooensis Zone show a strong affinity with those of the Chiungchussuan (⫽Qiongzhusian) Stage of China, especially taxa from the Yu’anshan Member of the Heilinpu Formation in Chengjiang and Jinning Counties, Yunnan (Zhang, 1987; Shu et al., 1995; Babcock and Zhang, 2001; Steiner et al., 2001; Zhang et al., 2001). The association of the genera Eoredlichia Chang (in Lu and Dong, 1952), Wutingaspis Kobayashi, 1944 and Yunnanocephalus Kobayashi, 1936 is considered to be an important age-diagnostic assemblage of the Eoredlichia–Wutingaspis Zone in South China (Zhang, 1985, 2003; Steiner et al., 2001; Zhang et al., 2001). The genus Wutingaspis ranges throughout the Eoredlichia– Wutingaspis Zone; however, Steiner et al. (2001) and Zhang et al. (2001) have observed that this zone can be subdivided into distinct lower and upper generic assemblages. Zhang et al. (2001) subdivided the Eoredlichia–Wutingaspis Zone into two subzones: the lower ‘Tsunydiscus Assemblage-subzone’; and the upper ‘Chengjiangaspis Assemblage-subzone.’ Subsequently, Steiner et al. (2001) also subdivided the Eoredlichia–Wutingaspis Zone into two subzones: the lower ‘Tsunydiscus Taxon-range Subzone’; and the upper ‘Yunnanocephalus Assemblage subzone.’ The two subzones of Zhang et al. (2001) and Steiner et al. (2001) appear to represent the same assemblages of the Yu’anshan Member, but the use of the name ‘Yunnanocephalus Assemblage subzone’ for the upper assemblage seems more appropriate due to the rare occurrence of Chenjiangaspis Zhang and Lin (in Zhang et al., 1980) in eastern Yunnan (Steiner et al., 2001). Therefore, the co-occurrence of Eoredlichia, Wutingaspis, and Yunnanocephalus in the South Australian Pararaia bunyerooensis Zone permits correlation with the Yunnanocephalus Assemblage subzone (upper Eoredlichia–Wutingaspis Zone) of South China. Jell (in Bengtson et al., 1990) considered cranidia referred to ¨ pik (1975b) to be synonymous with as Dolerolenus? sp. nov. by O Abadiella huoi. These cranidia are herein assigned to Wutingaspis euryoptilos from the Pararaia bunyerooensis Zone at Angorichina. Unfortunately, the precise stratigraphic horizon of the specimens from the Parara Limestone at Kulpara is unknown. Jell (in Bengtson et al., 1990) believed them to have come from a part of the Kulpara section containing taxa of the Abadiella huoi and Pararaia tatei zones, but it is possible that the specimens came

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from higher in the section, above the range of Pararaia tatei (Woodward, 1884). SYSTEMATIC PALEONTOLOGY

The morphological terminology employed follows Whittington and Kelly (1997). Registered specimens are housed in the paleontological collections of the South Australian Museum, Adelaide (prefix SAMP). Order REDLICHIIDA Richter, 1932 Suborder REDLICHIINA Richter, 1932 Superfamily REDLICHIOIDEA Poulsen, 1927 Family REDLICHIIDAE Poulsen, 1927 Genus REDLICHIA Cossmann, 1902 Type species.⎯Hoeferia noetlingi Redlich, 1899, Early Cambrian, Khussak Group, Salt Range, Pakistan. REDLICHIA

Zhou in Lu et al., 1974 Figure 6

GUIZHOUENSIS

Redlichia guizhouensis ZHOU IN LU, CHANG, CHIEN, CHU, LIN, ZHOU, QIAN, ZHANG, AND YUAN, 1974, p. 85, pl. 31, fig. 10; YIN AND LI, 1978, p. 400, pl. 147, fig. 1; LU, 1981, pl. 1, fig. 20; JELL IN BENGTSON, CONWAY MORRIS, COOPER, JELL, AND RUNNEGAR, 1990, p. 267, fig. 179. Olenellus sp. ETHERIDGE, 1905, p. 247, pl. 25, fig. 1. Olenellus? sp. ETHERIDGE, 1919, p. 382, pl. 39, fig. 1.

Figured material.⎯Four fragmentary cranidia, SAMP40581– 40584 (Fig. 6.1–6.5); three librigenae, SAMP40585–40587 (Fig. 6.6–6.11); one rostral plate, SAMP40588 (Fig. 6.12, 6.13); one fragmentary thoracic pleura, SAMP40589 (Fig. 6.14). Occurrence.⎯Wirrealpa Limestone, WL section horizons: WL/ 4, WL/12, WL/13, WL/17, WL/48, WL/52.3, WL/53.6, WL/56.2, WL/57.4, WL/63.1, WL/65.2, WL/74.8, WL/83, WL/103.6, WL/ 147; 2.8–103.9 m (true thickness) above the base of the section (Fig. 4). Discussion.⎯The occurrence of this species in the Wirrealpa Limestone has been adequately documented by Jell (in Bengtson et al., 1990). Large, well-preserved silicified librigenae from the WL section display a wider (tr.) genal field compared to the small, fragmentary librigena described and illustrated by Jell (in Bengtson et al., 1990, fig. 179d). REDLICHIA sp. Figure 7 Redlichiid indet. 1 JELL IN BENGTSON, CONWAY MORRIS, COOPER, JELL, AND RUNNEGAR, 1990, p. 273, fig. 182b–d.

Figured material.⎯Four fragmentary cranidia, SAMP40590– 40593 (Fig. 7.1–7.4); three librigenae, SAMP40594–40596 (Fig. 7.5–7.9); three pygidia, SAMP40597–40599 (Fig. 7.10–7.13). Occurrence.⎯Pararaia bunyerooensis Zone, Third Plain Creek Member, Mernmerna Formation, MMF section horizons: MMF/ 44.5, MMF/54.6, MMF/58.3, MMF/64.5, MMF/93, MMF/103; 25.5–59.1 m (true thickness) above the base of the section (Fig. 4). Discussion.⎯This species shows affinities with Redlichia takooensis Lu, 1950, and other indeterminate redlichiid fragments described and illustrated by Jell (in Bengtson et al., 1990). Shared characteristics with R. takooensis include: narrow (tr.) palpebral area; angle of divergence and shape of anterior branches of facial suture; length (exsag.) and width (tr.) of preocular field; length (sag., exsag.) of anterior cranidial border; librigena with broad (tr.) genal field and straight, wide (tr.) posterior margin; pygidium with broad axis not reaching posterior margin and displaying a bilobed terminal piece; and a single pair of pygidial pleurae terminating as short marginal spines. However, R. takooensis is easily distinguished in having a well-developed occipital spine and two pygidial axial rings.

Specimens referred to as ‘Redlichiid indet. 1’ by Jell (in Bengtson et al., 1990) are most certainly attributed to the species from the MMF section based on the material illustrated by Jell (in Bengtson et al., 1990, fig. 182b–d) and its association with Pararaia bunyerooensis in the Mernmerna Formation at Bunyeroo Creek. The two fragmentary cranidia of ‘Redlichiid indet. 1’ differ only in having a slightly narrower (tr.) palpebral area. Pygidia of ‘Redlichiid indet. 3’ documented by Jell (in Bengtson et al., 1990, fig. 182j, l, m) from the Ajax Limestone at Mt Scott Range also bear striking similarity to pygidia from the MMF section, based on characteristics mentioned above. Genus EOREDLICHIA Chang in Lu and Dong, 1952 Type species.⎯Redlichia intermediata Lu, 1940, Early Cambrian, Chiungchussu Formation, Yunnan, China. EOREDLICHIA sp. Figure 8.1–8.7 Figured material.⎯One fragmentary cranidium, SAMP40600 (Fig. 8.1, 8.2); one fragmentary thoracic pleura, SAMP40601 (Fig. 8.7); four fragmentary pygidia, SAMP40602–40605 (Fig. 8.3–8.6). Occurrence.⎯Pararaia bunyerooensis Zone, Third Plain Creek Member, Mernmerna Formation, MMF section horizons: MMF/ 54.6, MMF/58.3, MMF/64.5, MMF/75.2, MMF/93; 31.3–53.3 m (true thickness) above the base of the section (Fig. 4). Discussion.⎯Fragmentary silicified material from the Mernmerna Formation makes species identification difficult, although specimens show similarities with Eoredlichia shensiensis and E. intermediata (Lu, 1940). Jell (in Bengtson et al., 1990, p. 281) considered Pachyredlichia (⫽Eoredlichia) zhangshanensis Lin and Yao (in Zhang et al., 1980) to be a junior subjective synonym of E. shensiensis; this synonymy is followed herein. Palpebral lobe morphology (e.g., shape and exsagittal length) and pustulose ornament of the Angorichina material closely resembles that of E. shensiensis (e.g., Zhang et al., 1980, pl. 38, figs. 9, 12, 14; Jell in Bengtson et al., 1990, fig. 185a–g). However, cranidia of E. shensiensis from China (Chang, 1966, pl. 1, figs. 5, 6; Zhang et al., 1980, pl. 38, figs. 9–14; pl. 39, figs. 1, 2, 4) and South Australia (Jell in Bengtson et al., 1990, fig. 185a–e, g) do not appear to display a stout occipital spine. The fragmentary pygidia from the Mernmerna Formation (Fig. 8.3–8.6) bear close resemblance to pygidia of Eoredlichia intermediata from Chengjiang, South China (Shu et al., 1995, figs. 4f, 7b). Similarities include: pygidial outline; sagittal length of axis; and the presence of two axial rings and a semicircular terminal piece that is slightly narrower (tr.) than the axial rings. Genus WUTINGASPIS Kobayashi, 1944 Wutingaspis KOBAYASHI, 1944, p. 130; HARRINGTON IN R. C. MOORE, 1959, p. 205; LU, 1961, p. 301; LI, 1978, p. 189; YIN IN YIN AND LI, 1978, p. 406; LI, 1980, p. 45; ZHANG AND LIN IN ZHANG, LU, ZHU, QIAN, LIN, ZHOU, ZHANG, AND YUAN, 1980, p. 159 (for additional synonymy); LUO, 1981, p. 335; ZHOU, LI, AND QU, 1982, p. 223; LI AND ZHANG IN LI, KANG, AND ZHANG, 1990, p. 44; LUO IN LUO, JIANG, AND TANG, 1994, p. 124; ZHANG, 1997, p. 441.

Type species.⎯Wutingaspis tingi Kobayashi, 1944, Early Cambrian, Chiungchussu Formation, Yunnan, China. Discussion.⎯The close morphological similarity between the genera Abadiella, Parabadiella, and Wutingaspis has been the source of considerable debate in recent years (Jell in Bengtson et al., 1990; Steiner et al., 2001; Zhang et al., 2001; Jago et al., 2002a). Jell (in Bengtson et al., 1990) and Jago et al. (2002a) have been advocates of synonymizing Abadiella and Parabadiella, while Steiner et al. (2001) and Zhang et al. (2001) consider them to be separate genera. Steiner et al. (2001, p. 70) also commented on the similarity in the cranidial and pygidial morphology


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FIGURE 6—Redlichia guizhouensis Zhou in Lu et al., 1974. Silicified specimens from WL/12, Wirrealpa Limestone (WL section), unless otherwise stated. 1, Fragmentary cranidium (SAMP40581), dorsal view, ⫻2.5; 2, fragmentary cranidium (SAMP40582), dorsal view, ⫻2.5; 3, 4, fragmentary cranidium (SAMP40583), ⫻2, 3, dorsal view, 4, ventral view; 5, fragmentary cranidium (SAMP40584), dorsal view, ⫻3; 6, 7, right librigena (SAMP40585) from WL/4, ⫻2.5, 6, dorsal view, 7, ventral view; 8, 9, right librigena (SAMP40586), ⫻2.5, 8, dorsal view, 9, ventral view; 10, 11, left librigena (SAMP40587), ⫻2, 10, dorsal view, 11, ventral view; 12, 13, rostral plate (SAMP40588), ⫻2.5, 12, dorsal view, 13, ventral view; 14, right thoracic pleura (SAMP40589), dorsal view, ⫻3.

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FIGURE 7—Redlichia sp. Silicified specimens from MMF/64.5, Mernmerna Formation (MMF section), unless otherwise stated. 1, Fragmentary cranidium (SAMP40590), dorsal view, ⫻4; 2, fragmentary cranidium (SAMP40591), dorsal view, ⫻4; 3, fragmentary cranidium (SAMP40592), dorsal view, ⫻6; 4, fragmentary cranidium (SAMP40593), dorsal view, ⫻4; 5, right librigena (SAMP40594), dorsal view, ⫻6.5; 6, 7, left librigena (SAMP40595) from MMF/103, ⫻7.5, 6, dorsal view, 7, ventral view; 8, 9, left librigena (SAMP40596) from MMF/93, ⫻7.5, 8, dorsal view, 9, ventral view; 10, 11, fragmentary pygidium (SAMP40597), ⫻9.5, 10, dorsal view, 11, ventral view showing outline of bilobate terminus; 12, fragmentary pygidium (SAMP40598), dorsal view, ⫻11.5; 13, fragmentary pygidium (SAMP40599) from MMF/54.6, dorsal view, ⫻4.5.

of Parabadiella and Wutingaspis, listing three discriminating criteria to separate them: 1) shape of the preglabellar ridge (⫽plectrum); 2) exsagittal length of the palpebral lobes; and 3) posterolateral projection of the fixigenae. The first two criteria are unreliable diagnostic characters at the generic level because they show interspecific variation. For example, Wutingaspis euryoptilos n. sp. has a very narrow (tr.) plectrum and the length (exsag.) of the palpebral lobes is 30%–35% glabellar length (sag.), whereas W. tingi has a broad (tr.) plectrum and the length (exsag.) of the palpebral lobes is 35%–45% glabellar length (sag.). There

appears to be a consistent difference in the width (tr.) of the posterolateral projection of the fixigena between both genera. Species of Abadiella (⫽Parabadiella) have a very narrow (tr.) posterolateral projection, whereas species of Wutingaspis possess a considerably wider (tr.) posterolateral projection. Whether this character should be given generic or species level significance is uncertain. It is possible that Abadiella (⫽Parabadiella) and Wutingaspis are synonymous, but this interpretation can only be resolved by conducting a comprehensive revision of these genera, which is beyond the scope of this study.

PATERSON AND BROCK—EARLY CAMBRIAN TRILOBITES FROM SOUTH AUSTRALIA We agree with the arguments of Jell (in Bengtson et al., 1990) and Jago et al. (2002a) regarding the synonymy of Abadiella and Parabadiella. Furthermore, specimens described and illustrated as Abadiella huoi by Jell (in Bengtson et al., 1990) should be maintained as that species and not assigned to a new species of Wutingaspis, W. jelli, as described by Zhang (in Zhang et al., 2001). WUTINGASPIS EURYOPTILOS new species Figures 8.8–8.17, 9.1–9.7 ¨ PIK, 1975B, p. 41, pl. 7, fig. 2. Dolerolenus? sp. nov. O

Diagnosis.⎯Wutingaspis with anterior sections of facial suture diverging anteriorly at 90⬚–100⬚ between ␥ and ␤; glabella moderately tapering, anterior width (tr.) at midlength of frontal lobe 60%–65% occipital ring width (tr.); palpebral lobe length (exsag.) 30%–35% glabellar length (sag.); palpebral area width (tr.) at ⑀ 70%–80% adjacent glabellar width; small intergenal spine developed at distal extremity of posterior border. Librigenal field width (tr.) approximately 70%–75% adjacent librigenal width. Pygidium with three axial rings and a short (sag.), rounded terminal piece; second and third axial rings with medial depression. Description.⎯Cranidium of moderate size, up to 19 mm in length (sag.); trapezoidal in outline; low convexity (sag., tr.). Anterior margin moderately curved; posterior margin (excluding occipital ring) straight, directed posterolaterally. Anterior sections of facial suture curved, diverging anteriorly at 90⬚–100⬚ between ␥ and ␤, then strongly convergent anteriorly between ␤ and ␣; posterior sections of facial suture long, curved anteriorly, widely divergent posteriorly, with well-developed sutural ridge. Glabella moderately tapering, anterior width (tr.) at midlength of frontal lobe 60%–65% occipital ring width (tr.); frontal lobe rounded; moderate convexity (tr.), weak convexity (sag.); sagittal length (including LO) approximately 75% cranidial length. Axial furrow shallow, narrow (tr.); preglabellar furrow shallow, narrow (sag., exsag.). Glabellar furrows well developed; S1 strongly impressed, deepening abaxially, proximal portion straight, becoming strongly convex anteriorly at distal extremity, directed anterolaterally abaxially, width (tr.) approximately 30%–35% adjacent glabellar width (tr.); S2 and S3 same as for S1. Occipital ring of moderate convexity (tr.), flattened sagittally; length (sag.) 15%–20% glabellar length; short, stout posteromedial occipital spine directed slightly posteriorly; posterior margin moderately convex posteriorly. SO shallow and transverse medially, then directed anterolaterally and deepened into apodemal pits abaxially, wide (sag., exsag.). Preglabellar field flat, length (sag.) approximately 10% cranidial length; plectrum well developed, narrow (tr.). Preocular field gently downsloping, flat to weakly convex (exsag.), maximum length (exsag.) 25% cranidial length (sag.). Anterior border weakly convex, length (sag.) 10% cranidial length; anterior border furrow moderately curved, shallow, narrow (sag., exsag.). Palpebral lobe well developed, strongly convex (tr.), length (exsag.) 30%–35% glabellar length (sag.), width (tr.) 25%–30% lobe length, anterior tip situated opposite L3, posterior tip situated opposite midlength of L1; palpebral furrow shallow, narrow (tr.). Eye ridge well developed, forming a continuation of the palpebral lobe, strongly convex (exsag.), gently curved anteriorly, ridges diverge posteriorly at 120⬚–130⬚, proximal end merges with lateral margin of frontal lobe with anteroproximal margin of eye ridge continuing onto anterior margin of frontal lobe to form narrow (sag., exsag.) parafrontal band of low relief. Palpebral area weakly convex, width (tr.) at ⑀ 70%–80% adjacent glabellar width. Postocular area short (exsag.), of subequal length (exsag.) to sagittal length of occipital ring. Posterolateral projection of fixigena very wide, width (tr.) 20%–25% ⑀–⑀, gently downsloping, strongly tapering abaxially. Posterior border strongly convex

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(exsag.), slightly expanding abaxially; small intergenal spine developed at distal extremity of posterior border (Fig. 8.16); posterior border furrow deep, very wide (exsag.), expanding abaxially. Rostral plate and hypostome unknown. Librigena of moderate size, up to 22 mm in length (including genal spine); width (tr.) approximately 40%–50% length (including genal spine); lateral margin moderately curved to base of genal spine, then becoming straight and slightly deflected abaxially; posterior margin straight before strongly curving onto genal spine. Genal field of low convexity, width (tr.) approximately 70%–75% adjacent librigenal width. Eye socle of low dorsal elevation. Lateral border moderately convex, raised above genal field, widening (tr.) posteriorly, becoming widest at genal angle, anteriormost dorsal portion of border sharply tapers to a point; lateral and posterior border furrows more of a change in slope than distinct furrows. Posterior border weakly convex, short (tr.), narrow (exsag.), of uniform width (exsag.). Genal spine long, length approximately 30%–35% librigenal length (including spine); narrow base (tr.), strongly tapering posteriorly; straight. Librigenal doublure width (tr.) mimics dorsal surface of lateral and posterior librigenal border; sharp ridge developed on lateral margin of doublure, terminating at base of genal spine, representing a change in slope from rounded lateral margin to wide (tr.), slightly concave adaxial portion. Thorax unknown. Pygidium moderately small, up to 6 mm in length (sag.), weakly convex (sag., tr.). Axis with curved lateral margins, reaching maximum width (tr.) at second axial ring; three axial rings and a short (sag.), rounded terminal piece; first and second axial rings separated by well-developed axial furrow that is wide (sag.) medially, becoming narrower (exsag.) and deeper abaxially; second axial ring with medial depression; third axial ring with medial depression that is wider (tr.) than depression in second axial ring; articulating half ring poorly preserved. Pleural regions with at least one pair of distinct pleurae; pleural furrow narrow and of moderate depth. Borders and margins obscure. Entire dorsal surface of exoskeleton densely covered in granules. Preglabellar, preocular and librigenal fields covered in genal caeca. Etymology.⎯Greek eurys, broad, widespread, and optilos, eye; referring to the wide (tr.) palpebral area of the fixigenae. Type material.⎯Holotype: fragmentary cranidium, SAMP40606 (Fig. 8.8). Paratypes: six fragmentary cranidia, SAMP40607–40612 (Figs. 8.9–8.12, 8.16, 8.17, 9.1); five librigenae, SAMP40613–40617 (Figs. 8.13–8.15, 9.2–9.5); two fragmentary pygidia, SAMP40618– 40619 (Fig. 9.6, 9.7). Type locality.⎯Mernmerna Formation (MMF section), Hawker Group; base of section coordinates: 31⬚11⬘38.4⬙S, 138⬚52⬘28.7⬙E; map datum: WGS84, on the eastern side of The Bunkers, approximately 1 km south of Balcoracana Creek on Angorichina Station, Flinders Ranges, South Australia (see Figs. 2, 3). Type stratum.⎯Third Plain Creek Member of the Mernmerna Formation, MMF section, horizon MMF/93; 53.3 m (true thickness) above the base of the section (Fig. 4). Occurrence.⎯Pararaia bunyerooensis Zone, Third Plain Creek Member, Mernmerna Formation, MMF section horizons: MMF/ 54.6, MMF/58.3, MMF/64.5, MMF/75.2, MMF/93; 31.3–53.3 m (true thickness) above the base of the section (Fig. 4). Discussion.⎯Wutingaspis euryoptilos is remarkably similar to the type species of Wutingaspis, W. tingi Kobayashi, 1944. Cranidial features of W. tingi that are shared with W. euryoptilos include: well-developed sutural ridge on posterior section of facial suture (Chang, 1962, pl. 1, fig. 4a; Zhang et al., 1980, pl. 42, figs. 2, 4); short, stout posteromedial occipital spine; eye ridges diverge

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PATERSON AND BROCK—EARLY CAMBRIAN TRILOBITES FROM SOUTH AUSTRALIA posteriorly at 120⬚–130⬚; anteroproximal margin of eye ridge continues around frontal lobe to form narrow (sag., exsag.) parafrontal band (Zhang et al., 1980, pl. 42, fig. 2); very wide (tr.) posterolateral projection of fixigenae, width (tr.) 20%–25% ⑀–⑀; small intergenal spine developed at distal extremity of posterior border (Zhang et al., 1980, pl. 42, fig. 6; Shu et al., 1995, fig. 2f). Glabellar furrow morphology of these species is also very similar, although some cranidia of W. tingi display a medial connection of S1 (e.g., Chang, 1962, pl. 1, fig. 4a; Zhang et al., 1980, pl. 42, fig. 4; Shu et al., 1995, fig. 2f; Steiner et al., 2001, pl. 2, fig. 6). However, it is important to note that these specimens of W. tingi are preserved as internal molds. The pygidium of W. tingi also bears close similarity to that of W. euryoptilos in possessing three axial rings and a short (sag.), rounded terminal piece, with the second and third axial rings showing a medial depression (Zhang et al., 1980, pl. 41, fig. 10; pl. 42, fig. 3; Steiner et al., 2001, pl. 2, fig. 7). Wutingaspis tingi can be distinguished from W. euryoptilos, however, by the following features: anterior sections of facial suture diverge anteriorly at 60⬚–70⬚ (90⬚–100⬚ in W. euryoptilos); glabella gently tapers, anterior width (tr.) at midlength of frontal lobe 75%–80% occipital ring width (tr.) (60%–65% in W. euryoptilos); palpebral lobe length (exsag.) 35%–45% glabellar length (sag.) (30%–35% in W. euryoptilos); and palpebral area width (tr.) at ⑀ 55%–65% adjacent glabellar width (tr.) (70%–80% in W. euryoptilos). The majority of Wutingaspis species described from China are poorly known, in most cases represented by no more than two or three cranidia, thus making species comparison difficult. The better known species that are represented by different sclerite types, and in some cases partially articulated exoskeletons, e.g., W. conditus Kobayashi, 1944 (Chang, 1966, pl. 2, fig. 1), W. malungensis Lu, 1961 (Zhang et al., 1980, pl. 40, fig. 7), W. sichuanensis Li, 1978 (pl. 91, fig. 9), can be easily differentiated from W. euryoptilos by having a narrower (tr.) palpebral area, no intergenal spine, narrower (tr.) librigenal field, and two pygidial axial rings. ¨ pik (1975b, Dolerolenus? sp. nov. described and illustrated by O p. 41, pl. 7, fig. 2) is considered herein to be synonymous with Wutingaspis euryoptilos. The cranidia are almost indistinguishable, although the cranidium of Dolerolenus? sp. nov. displays stronger genal caeca on the preocular field; this difference may be attributed to different styles of preservation. Particular characteristics of Dolerolenus? sp. nov. such as glabellar shape and furrows, width (tr.) of the palpebral area, and the granulose ornamentation strongly support this synonymy. Jell (in Bengtson et al., 1990) and Zhang et al. (2001) considered Dolerolenus? sp. nov. to be a synonym of Abadiella (⫽Parabadiella) huoi. The cranidia of Dolerolenus? sp. nov. and Abadiella huoi are similar in many respects, but those of A. huoi differ in having a narrower (tr.) palpebral area (e.g., Chang, 1966, pl. 1, figs. 1, 2; Zhang et al., 1980, pl. 46, figs. 1–4, 6; Jell in Bengtson et al., 1990, figs. 183a, c, d, j, 184s–u, w, x, z, ab). Unfortunately, the posterolateral

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projection of the fixigena is not preserved in cranidia of Dolerolenus? sp. nov., making it impossible to determine whether it has a wide (tr.) projection like Wutingaspis euryoptilos or narrow (tr.) projection like Abadiella huoi. Genus YORKELLA Kobayashi, 1942 Yorkella KOBAYASHI, 1942, p. 492; JELL IN BENGTSON, CONWAY MORRIS, COOPER, JELL, AND RUNNEGAR, 1990, p. 288; ZHANG, 1997, p. 444.

Type species.⎯Conocephalites australis Woodward, 1884, Early Cambrian, Parara Limestone, Yorke Peninsula, South Australia. YORKELLA aff.

AUSTRALIS (Woodward, 1884) Figure 9.8–9.20 Figured material.⎯Two fragmentary cranidia, SAMP40620– 40621 (Fig. 9.8, 9.9); four librigenae, SAMP40622–40625 (Fig. 9.10–9.14); four pygidia, SAMP40626–40629 (Fig. 9.15–9.20). Occurrence.⎯Pararaia bunyerooensis Zone, Third Plain Creek Member, Mernmerna Formation, MMF section horizons: MMF/ 44.5, MMF/52.4, MMF/54.6, MMF/64.5, MMF/82.6, MMF/93, MMF/103; 25.5–59.1 m (true thickness) above the base of the section (Fig. 4). Discussion.⎯The species of Yorkella from the MMF section bears close resemblance to the type species Y. australis (Woodward, 1884), which has been well described and illustrated by Jell (in Bengtson et al., 1990, figs. 189, 190). Although only two fragmentary cranidia are known from the MMF section (Fig. 9.8, 9.9), they are indistinguishable from the cranidia of Y. australis illustrated by Jell (in Bengtson et al., 1990, figs. 189l–q, 190a, b, l–t). The librigenae of Y. australis differ only in having a narrower (tr.) lateral border and wider (tr.) genal field (Jell in Bengtson et al., 1990, figs. 189s, t, 190k). The smallest illustrated librigena of Yorkella from the MMF section (Fig. 9.14) is similar to those of Y. australis; however, larger librigenae (Fig. 9.10, 9.11) show that the lateral border widens and the genal field becomes narrower throughout ontogeny. The only major morphological difference between pygidia from the MMF section and Y. australis is the ratio of sagittal length to width (tr.), i.e., sagittal length 45% and 60% maximum width (tr.), respectively. Specimens from the MMF section most likely represent a new species. However, until additional well-preserved cranidia are found, this species is left under open nomenclature.

Superfamily ELLIPSOCEPHALOIDEA Matthew, 1887 ¨ pik, 1975a Family ESTAINGIIDAE O ¨ pik, 1975a was reDiscussion.⎯The subfamily Estaingiinae O cently elevated to family level by Jell (in Jell and Adrain, 2003, p. 334, n6) based on the discovery of a nomenclatural error between the synonymous genera Estaingia Pocock, 1964 and Hsuaspis Chang in Lu et al., 1965. Westrop and Landing (2000, p. 863) have recently discussed

← FIGURE 8—1–7, Eoredlichia sp. from the Mernmerna Formation (MMF section); all silicified specimens. 1, 2, Fragmentary cranidium (SAMP40600) from MMF/64.5, ⫻2.5, 1, dorsal view, 2, lateral view; 3, fragmentary pygidium (SAMP40602) from MMF/58.3, dorsal view, ⫻5; 4, fragmentary pygidium (SAMP40603) from MMF/54.6, dorsal view, ⫻3; 5, fragmentary pygidium (SAMP40604) from MMF/54.6, dorsal view, ⫻4; 6, fragmentary pygidium (SAMP40605) from MMF/64.5, dorsal view, ⫻7; 7, fragmentary right thoracic pleura (SAMP40601) from MMF/64.5, dorsal view, ⫻3.5. 8–17, Wutingaspis euryoptilos n. sp. from the Mernmerna Formation (MMF section); all silicified specimens; 8, holotype cranidium (SAMP40606) from MMF/93, dorsal view, stereo pair, ⫻5.5; 9, fragmentary cranidium (SAMP40607) from MMF/64.5, dorsal view, ⫻4; 10, 11, fragmentary cranidium (SAMP40608) from MMF/93, 10, dorsal view, ⫻5, 11, enlargement showing parafrontal band, plectrum, and granulose ornament, ⫻7; 12, fragmentary cranidium (SAMP40609) from MMF/58.3, dorsal view, ⫻7.5; 13, 14, left librigena (SAMP40613) from MMF/ 64.5, ⫻5, 13, dorsal view, 14, ventral view; 15, left librigena (SAMP40614) from MMF/64.5, dorsal view, ⫻4; 16, fragmentary cranidium (SAMP40610) from MMF/93 showing sutural ridge on posterolateral projection and small intergenal spine on distal end of posterior border, dorsal view, ⫻5; 17, fragmentary cranidium (SAMP40611) from MMF/93, dorsal view, ⫻11.5.

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PATERSON AND BROCK—EARLY CAMBRIAN TRILOBITES FROM SOUTH AUSTRALIA the differing classifications of ellipsocephaloid families, in partic¨ pik (1975b), Zhang et al. (1980), Jell (in Bengtson ular those of O et al., 1990), and Geyer (1990). Westrop and Landing (2000) noted that the majority of these classifications relied upon glabellar outline to diagnose ellipsocephaloid families and subfamilies. For example, Jell (in Bengtson et al., 1990) assigned Hsuaspis (⫽Estaingia) to the Ichangiidae (⫽Estaingiidae, fide Jell in Jell and Adrain, 2003) and Pararaia to the Protolenidae on the basis of glabellar outline. Westrop and Landing (2000) commented that there are limits to the utility of glabellar outline in the suprageneric classification of ellipsocephaloids. They observed that Hsuaspis (⫽Estaingia) and Pararaia have strong similarities in cephalic and pygidial morphology, as previously noted by Palmer (in Palmer and Rowell, 1995, p. 16), but that these characters were absent or differed greatly in Protolenus Matthew, 1892 and related genera. Hence, Westrop and Landing (2000) concluded that similarities in glabellar outline between ‘‘protolenids’’ and some species of Pararaia are homoplastic, and that both Hsuaspis (⫽Estaingia) and Pararaia should be assigned to the Ichangiidae (⫽Estaingiidae). Genus ESTAINGIA Pocock, 1964 ¨ PIK, 1975b, p. 10; PATERSON, 2005, Estaingia POCOCK, 1964, p. 462; O p. 89. Hsuaspis CHANG IN LU, CHANG, ZHU, QIAN, AND XIANG, 1965, p. 85; SUN IN ZHOU, LIU, MENG, AND SUN, 1977, p. 123; LI IN YIN AND LI, 1978, p. 427; ZHANG AND ZHU, 1979, p. 516; ZHU IN ZHANG, LU, ZHU, QIAN, LIN, ZHOU, ZHANG, AND YUAN, 1980, p. 244; LI IN ZHOU, LI, AND QU, 1982, p. 227; ZHANG IN QIU, LU, ZHU, BI, LIN, ZHOU, ZHANG, QIAN, JU, HAN, AND WEI, 1983, p. 52; SUN, 1984, p. 347; JELL IN BENGTSON, CONWAY MORRIS, COOPER, JELL, AND RUNNEGAR, 1990, p. 310; PALMER IN PALMER AND ROWELL, 1995, p. 16; NEDIN, 1995, p. 36; JAGO, LIN, DAVIDSON, STEVENS, AND BENTLEY, 1997, p. 69. Pseudichangia CHU AND ZHOU IN LU, CHANG, CHIEN, CHU, LIN, ZHOU, QIAN, ZHANG, AND YUAN, 1974, p. 93; ZHU IN ZHANG, LU, ZHU, QIAN, LIN, ZHOU, ZHANG, AND YUAN, 1980, p. 239; SUN, 1984, p. 346. ¨ PIK, 1975b, p. 13. Strenax O Zhuxiella ZHANG AND ZHU IN ZHANG, LU, ZHU, QIAN, LIN, ZHOU, ZHANG, AND YUAN, 1980, p. 247; SUN, 1984, p. 348.

Type species.⎯Estaingia bilobata Pocock, 1964, Early Cambrian, Emu Bay Shale, Kangaroo Island, South Australia. Discussion.⎯The synonymy of Estaingia, Hsuaspis, Pseudichangia, Strenax, and Zhuxiella has been discussed by Jell (in Bengtson et al., 1990, p. 310), Jago et al. (1997, p. 69–71), and Paterson (2005, p. 89). ESTAINGIA

(Jell in Bengtson et al., 1990) new combination Figure 10

OCCIPITOSPINA

Hsuaspis occipitospina JELL IN BENGTSON, CONWAY MORRIS, COOPER, JELL, AND RUNNEGAR, 1990, p. 312, fig. 200.

Figured material.⎯Eight cranidia, SAMP40630–40637 (Fig.

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10.1–10.8); one partial librigena, SAMP40638 (Fig. 10.10); two partial thoraces, SAMP40639–40640 (Fig. 10.11, 10.14); one partial thoracic segment, SAMP40641 (Fig. 10.9); two pygidia, SAMP40642–40643 (Fig. 10.12, 10.13). Occurrence.⎯Pararaia janeae Zone, Oraparinna Shale, OS section horizon: OS/76; 38 m (true thickness) above the base of the section (Fig. 4). Discussion.⎯This species was originally described and referred to as Hsuaspis occipitospina by Jell (in Bengtson et al., 1990). However, regarding the synonymy of Hsuaspis and Estaingia (see Jell in Jell and Adrain, 2003, p. 334), it should now be referred to as Estaingia occipitospina (Jell). Specimens of Estaingia from the OS section undoubtedly belong to E. occipitospina based on Jell’s (in Bengtson et al., 1990, p. 312) diagnosis and description, although most cranidia illustrated herein (Fig. 10.1–10.6, 10.8) do not display the weakly impressed axial furrows otherwise characteristic of this species. This is likely due to preservation, since specimens from the OS section are preserved as exfoliated internal molds in siltstone; this is further supported by the variation in the axial furrows between the internal mold and latex cast of the holotype of E. occipitospina (Jell in Bengtson et al., 1990, fig. 200e, f). This would also explain the apparent absence of the occipital spine in many of the specimens. Jago et al. (1997) and Paterson (2005) have also observed the same preservational bias of the occipital spine in specimens of Estaingia ¨ pik, 1975b) from the Cymbric Vale Formation, westcerastes (O ern New South Wales. Two cranidia from the OS section (Fig. 10.7, 10.8) also demonstrate that the occipital spine in E. occipitospina is considerably longer and more vertically inclined than those illustrated by Jell (in Bengtson et al., 1990, fig. 200f, o–r). Genus PARARAIA Kobayashi, 1942 Pararaia KOBAYASHI, 1942, p. 492; JELL IN BENGTSON, CONWAY MORRIS, COOPER, JELL, AND RUNNEGAR, 1990, p. 302. Proichangia ZHANG AND ZHU IN ZHANG, LU, ZHU, QIAN, LIN, ZHOU, ZHANG, AND YUAN, 1980, p. 241.

Type species.⎯Dolichometopus tatei Woodward, 1884, Early Cambrian, Parara Limestone, Horse Gully, Ardrossan, Yorke Peninsula, South Australia. PARARAIA

Jell in Bengtson et al., 1990 Figure 11

BUNYEROOENSIS

Pararaia bunyerooensis JELL IN BENGTSON, CONWAY MORRIS, COOPER, JELL, AND RUNNEGAR, 1990, p. 306, fig. 196.

Description.⎯Cranidium moderately small, up to 10 mm in length (sag.); subquadrate in outline; low convexity (sag., tr.). Anterior margin strongly curved, width (tr.) equal to ␦–␦; posterior margin (excluding occipital ring) straight, directed slightly posterolaterally abaxially to fulcrum, then directed anterolaterally. Anterior sections of facial suture curved, diverging anteriorly at 50⬚–60⬚ between ␥ and ␤, then converging between ␤ and ␣; posterior sections of facial suture very short. Glabella gently tapering, anterior width (tr.) at midlength of frontal lobe 70%–80%

← FIGURE 9—1–7, Wutingaspis euryoptilos n. sp. from MMF/64.5, Mernmerna Formation (MMF section), unless otherwise stated; all silicified specimens. 1, Fragmentary cranidium (SAMP40612), dorsal view, ⫻3.5; 2, 3, fragmentary left librigena (SAMP40615), ⫻8.5, 2, dorsal view, 3, ventral view; 4, fragmentary left librigena (SAMP40616), dorsal view, ⫻3; 5, fragmentary left librigena (SAMP40617), ventral view, ⫻3.5; 6, fragmentary pygidium (SAMP40618) from MMF/54.6, dorsal view, ⫻5.5; 7, fragmentary pygidium (SAMP40619), dorsal view, ⫻8.5. 8–20, Yorkella aff. australis (Woodward, 1884) from the Mernmerna Formation (MMF section); all silicified specimens; 8, fragmentary cranidium (SAMP40620) from MMF/64.5, dorsal view, ⫻6.5; 9, fragmentary cranidium (SAMP40621) from MMF/64.5, dorsal view, ⫻7.5; 10, right librigena (SAMP40622) from MMF/82.6, dorsal view, ⫻5.5; 11, fragmentary right librigena (SAMP40623) from MMF/54.6, dorsal view, ⫻3.5; 12, 13, small right librigena (SAMP40624) from MMF/44.5, ⫻5, 12, dorsal view, 13, ventral view; 14, small left librigena (SAMP40625) from MMF/103, dorsal view, ⫻8; 15, fragmentary pygidium (SAMP40626) from MMF/54.6, dorsal view, stereo pair, ⫻6; 16, 17, pygidium (SAMP40627) from MMF/93, ⫻10.5, 16, dorsal view, 17, ventral view; 18, fragmentary pygidium (SAMP40628) from MMF/54.6, dorsal view, stereo pair, ⫻7; 19, 20, pygidium (SAMP40629) from MMF/52.4, ⫻6, 19, dorsal view, 20, ventral view.

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FIGURE 10—Estaingia occipitospina (Jell in Bengtson et al., 1990). Internal molds from the Oraparinna Shale (OS section). 1, Cranidium (SAMP40630), dorsal view, ⫻3; 2, cranidium (SAMP40631), dorsal view, ⫻4; 3, cranidium (SAMP40632), dorsal view, ⫻4; 4, cranidium (SAMP40633), dorsal view, ⫻5; 5, cranidium (SAMP40634), dorsal view, ⫻5.5; 6, cranidium (SAMP40635), dorsal view, ⫻6; 7, cranidium (SAMP40636) showing large occipital spine, oblique anterolateral view, ⫻3; 8, cranidium (SAMP40637) showing external mold of occipital spine, dorsal view, ⫻6.5; 9, partial thoracic segment (SAMP40641), dorsal view, ⫻4.5; 10, partial left librigena (SAMP40638), dorsal view, ⫻4.5; 11, partial thorax (SAMP40639), dorsal view, ⫻3; 12, pygidium (SAMP40642), dorsal view, ⫻7; 13, pygidium (SAMP40643) with articulated thoracic segment, dorsal view, ⫻7; 14, partial thorax (SAMP40640), dorsal view, ⫻11.

PATERSON AND BROCK—EARLY CAMBRIAN TRILOBITES FROM SOUTH AUSTRALIA occipital ring width (tr.); frontal lobe rounded; moderate convexity (tr.), low convexity (sag.); sagittal length (including LO) 70%– 80% cranidial length. Axial furrow shallow, narrow (tr.), straight; preglabellar furrow shallow (exsag.), very shallow sagittally due to plectrum, narrow (sag., exsag.). S1 weakly to moderately impressed, straight, directed anterolaterally abaxially (diverging anteriorly from each other at 130⬚), width (tr.) approximately 25% adjacent glabellar width (tr.), narrow (exsag.); S2 weakly to moderately impressed, straight, transverse, width (tr.) same as S1, narrow (exsag.); S3 obscure to moderately impressed, straight, transverse to directed posterolaterally abaxially, width (tr.) same as S1, narrow (exsag.). Occipital ring of moderate convexity (tr.), flattened sagittally; length (sag.) 20%–25% glabellar length; small posteromedial occipital node weakly developed; posterior margin strongly bowed. SO straight, narrow (sag., exsag.), of moderate depth medially and becoming deeper abaxially. Preglabellar field moderately downsloping, weakly convex (sag.), length (sag.) 10%–20% cranidial length; plectrum well developed and of low relief, subtriangular in outline, expanding anteriorly, encroaching onto anterior border. Preocular field moderately downsloping, weakly convex (exsag.), length (exsag.) approximately 25% cranidial length (sag.). Anterior border flat to weakly convex, length (sag.) 10%–15% cranidial length, slightly expanding (exsag.) abaxially; anterior border furrow strongly curved, more of a change in slope than distinct furrow, interrupted sagittally by plectrum. Palpebral lobe well developed, moderately convex (tr.), length (exsag.) 30%–35% cranidial length (sag.), width (tr.) 25%– 30% lobe length, anterior tip situated opposite S3, posterior tip situated opposite SO or slightly anterior of SO; palpebral furrow shallow, narrow (tr.). Eye ridge well developed, forming a continuation of the palpebral lobe, flat to weakly convex (exsag.), gently curved anteriorly, ridges diverge posteriorly at 140⬚, proximal end situated adjacent to posterior portion of frontal lobe, separated from glabella by axial furrow; eye ridge divided into inner and outer bands by very weakly developed ocular furrow. Palpebral area flat to weakly convex, width at ⑀ (tr.) 70%–85% adjacent glabellar width. Posterolateral projection of fixigena extremely short (tr.), gently downsloping, broadly rounded distally. Posterior border moderately convex (exsag.), slightly expanding abaxially to fulcrum that displays a rounded bulge, then sharply tapers to distal end of border; posterior border furrow deep, wide (exsag.), expanding abaxially. Rostral plate strongly curved, following same curvature as anterior margin of cranidium, strongly convex dorsoventrally; uniform length (sag., exsag.), length approximately 15% width (tr.); rostral suture evenly curved; connective sutures straight, divergent anteriorly; posterior margin smooth. Dorsal surface with shallow, very narrow (sag., exsag.) furrow developed around midlength (sag., exsag.), extending across entire width (tr.). Ventral surface with ridge extending along midlength, representing change in slope. Hypostome unknown. Librigena moderately small, up to 14 mm in length (including genal spine); width (tr.) approximately 25%–30% length (including genal spine); lateral margin gently curved, continuing evenly onto genal spine; posterior margin gently curved before strongly curving onto genal spine. Genal field of low convexity and low relief, width (tr.) approximately 40%–50% adjacent librigenal width. Lateral border flat to weakly convex, raised above genal field, widening (tr.) posteriorly, becoming widest at genal angle, anteriormost dorsal portion of border sharply tapers to a point; epiborder furrow weakly developed near lateral margin and continues posteriorly onto entire length of genal spine, epiborder furrow also developed on proximal margin of genal spine; lateral and posterior border furrows more of a change in slope than distinct furrows. Posterior border flat to weakly convex, raised above

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genal field, short (tr.), narrow (exsag.), moderately expanding in width (exsag.) abaxially. Genal spine long, length 50%–60% librigenal length (including spine) [at least 65% in smaller librigenae (Fig. 11.17, 11.18)]; broad base (tr.), strongly tapering posteriorly, slight adaxial curvature. Librigenal doublure width (tr.) mimics dorsal surface of lateral and posterior librigenal border and anterior cranidial border; sharp ridge developed on lateral portion of doublure terminating at base of genal spine (forming continuation of ridge on ventral surface of rostral plate), representing a change in slope from rounded lateral margin to wide (tr.), slightly concave adaxial portion. Thoracic segments with axis of strong convexity. Axial ring width (tr.) approximately 80% width of pleura, slightly convex anteriorly with lateral portions directed anterolaterally; small medial axial node weakly developed; articulating half ring of subequal length (sag.) to axial ring, strongly tapering abaxially, slightly narrower (tr.) than axial ring; articulating furrow concave anteriorly, shallow medially, becoming deeper abaxially. Pleura horizontal to fulcrum, then moderately downsloping to distal end; anterior pleural band rapidly expands abaxially with well developed facet; posterior pleural band rapidly tapers abaxially; pleural furrow deep, extends diagonally across pleura from anterolateral corner of axial ring to posterolateral corner of pleural tip. Pygidium very small, up to 2.5 mm in length (sag.), strongly convex (sag., tr.), sagittal length 35%–45% maximum width (tr.). Axis gently tapers posteriorly, almost reaching posterior margin, anterior width (tr.) 30%–40% maximum pygidial width; two axial rings and a broadly rounded terminal piece, anterior and posterior axial rings separated by well developed pseudo-articulating half ring; axial ring furrow separating posterior axial ring and terminal piece very shallow medially and deepened laterally; articulating half ring of uniform length (sag., exsag.), of subequal length to, and slightly narrower (tr.) than, anterior axial ring (Jell in Bengtson et al., 1990, fig. 196k). Pleural regions well defined with three distinct pleurae, each terminating in short posteriorly directed marginal spines; pleurae separated by well developed interpleural furrows; anterior pleura considerably wider (tr.) than posterior pleura; anterior band of anterior pleura rapidly expands abaxially, posterior band of anterior pleura of uniform length (exsag.) and narrower (exsag.) than anterior band; anterior and posterior bands of posterior pleura subequal in length (exsag.); anterior and posterior bands of pleurae separated by deep pleural furrows that terminate before marginal spines. Third pair of marginal spines situated on posterior margin. Pygidial doublure narrow laterally, obscure medially. Entire dorsal surface of exoskeleton smooth. Preglabellar and preocular fields covered in genal caeca. Figured material.⎯Six cranidia, SAMP40644–40649 (Fig. 11.1, 11.2, 11.5–11.10); six librigenae, SAMP40650–40655 (Fig. 11.3, 11.4, 11.15–11.18, 11.22–11.24); one rostral plate, SAMP40656 (Fig. 11.11, 11.12); one fragmentary thoracic segment, SAMP40657 (Fig. 11.13, 11.14); two pygidia, SAMP40658–40659 (Fig. 11.19–11.21). Occurrence.⎯Pararaia bunyerooensis Zone, Third Plain Creek Member, Mernmerna Formation, MMF section horizons: MMF/ 8.8, MMF/15.5, MMF/19, MMF/25.2, MMF/44.5, MMF/51.9, MMF/52.4, MMF/54.6, MMF/56.4, MMF/64.5, MMF/75.2, MMF/82.6, MMF/85.8, MMF/91.8, MMF/93, MMF/103; 5.1– 59.1 m (true thickness) above the base of the section (Fig. 4). Discussion.⎯New silicified material of Pararaia bunyerooensis has enabled better understanding of the morphology of this species, especially ventral structures, hence the revised description herein. Zang et al. (2001) tentatively assigned three fragmentary cranidia from the Yalkalpo-2 drillcore in the Arrowie Basin to Pararaia bunyerooensis. Unfortunately, the specimens of Pararaia? bunyerooensis from Yalkalpo-2 illustrated by Zang

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PATERSON AND BROCK—EARLY CAMBRIAN TRILOBITES FROM SOUTH AUSTRALIA et al. (2001, pl. 1, figs. g, h, k; reillustrated in Gravestock et al., 2001, pl. 1, figs. 7, 8, 11) are too incomplete, and the paucity of other sclerites renders species identification impossible. A possible paedomorphic lineage may exist between Pararaia bunyerooensis and P. janeae based on new evidence from small specimens of P. bunyerooensis from the MMF section. These species are considered to be sister taxa based on the following shared derived characters that are lacking in other congeners: lateral border and genal spine of librigena with distinct epiborder furrow, and three pairs of pygidial marginal spines. Cranidial characteristics in smaller specimens of P. bunyerooensis (e.g., Fig. 11.10) such as the longer (sag.) preglabellar field, wider (tr.) palpebral area, and narrower (tr.) glabella are typical in large cranidia of P. janeae (Jell in Bengtson et al., 1990, fig. 197a, b, p, q). Smaller librigenae of P. bunyerooensis (e.g., Fig. 11.17, 11.18) possess a considerably longer, narrow based (tr.) genal spine and narrower (tr.) lateral border, characteristic of P. janeae librigenae (Jell in Bengtson et al., 1990, fig. 197l, m). Smaller pygidia of P. bunyerooensis (e.g., Fig. 11.19, 11.20) appear to have a similar sagittal length to transverse width ratio as pygidia of P. janeae (Jell in Bengtson et al., 1990, fig. 197f, g). Furthermore, there is a considerable difference in the known maximum size ranges of these species, i.e., up to 10 mm cranidial length (sag.) in P. bunyerooensis and up to 15 mm cranidial length (sag.) in P. janeae (Jell in Bengtson et al., 1990, fig. 197q). This indicates that retardation in the onset of maturity in P. janeae resulted in the attainment of a larger adult size than in P. bunyerooensis. The above evidence suggests that P. janeae evolved from the ancestral P. bunyerooensis via neoteny (s. McNamara, 1986). Family YUNNANOCEPHALIDAE Hupe´, 1953 Genus YUNNANOCEPHALUS Kobayashi, 1936 Yunnanocephalus KOBAYASHI, 1936, p. 101; HENNINGSMOEN IN R. C. MOORE, 1959, p. 212; LI, 1978, p. 196; ZHANG, 1987, p. 228 (for additional synonymy); LUO IN LUO, JIANG, AND TANG, 1994, p. 137; SHU, GEYER, CHEN, AND ZHANG, 1995, p. 222 (for comprehensive synonymy); PALMER IN PALMER AND ROWELL, 1995, p. 17.

Type species.⎯Ptychoparia yunnanensis Mansuy, 1912, Early Cambrian, Chiungchussu Formation, Yunnan, China. YUNNANOCEPHALUS MACROMELOS new species Figure 12 Diagnosis.⎯See Table 1 for summary of diagnostic characters. Description.⎯Cranidium moderately small, up to 8 mm in length (sag.); trapezoidal in outline; strongly convex (sag., tr.). Anterior margin moderately curved, width (tr.) 85%–95% ␦–␦; posterior margin (excluding occipital ring) straight and transverse to fulcrum, then directed posterolaterally. Anterior sections of facial suture short, subparallel to slightly divergent anteriorly between ␥ and ␤, then strongly convergent anteriorly between ␤ and ␣; posterior sections of facial suture long, curved anteriorly, widely divergent posteriorly. Glabella gently tapering, anterior width (tr.) at midlength of frontal lobe 70%–75% occipital ring

135

width (tr.); frontal lobe truncate; strong convexity (sag., tr.); sagittal length (including LO) 80%–85% cranidial length. Axial furrow deep, wide (tr.), straight; preglabellar furrow more of a change in slope than distinct furrow. Glabellar furrows well developed; S1 moderately impressed, convex anteriorly, directed anterolaterally abaxially, width (tr.) approximately 30%–35% adjacent glabellar width (tr.), narrow (exsag.); S2 moderately impressed, straight, transverse, width (tr.) same as S1, narrow (exsag.); S3 weakly impressed, straight, directed posterolaterally abaxially, width (tr.) approximately 25%–30% adjacent glabellar width (tr.), narrow (exsag.). Occipital ring of strong convexity (tr.), flattened sagittally; length (sag.) 15%–20% glabellar length; small posteromedial occipital node weakly developed; posterior margin weakly convex posteriorly. SO transverse medially, directed anteriorly laterally, wide (sag., exsag.), of moderate depth medially and becoming deeper abaxially. Preglabellar field absent. Preocular field subtriangular in outline, strongly downsloping, weakly convex (exsag.), maximum length (exsag.) 10%–15% cranidial length (sag.). Anterior border strongly convex, length (sag.) 15%–20% cranidial length, slightly expands (exsag.) abaxially to midway between sagittal line and lateral margin, then tapers abaxially; anterior border furrow of moderate depth, lateral sections weakly convex anteriorly, medial section in front of glabella strongly convex anteriorly. Palpebral lobe well developed, moderately convex (tr.), length (exsag.) 25%–30% cranidial length (sag.), width (tr.) 30%–35% lobe length, anterior tip situated opposite L3, posterior tip situated opposite midlength of L1; palpebral furrow shallow, narrow (tr.). Eye ridge well developed, forming a continuation of the palpebral lobe, moderately convex (exsag.), gently curved anteriorly, ridges diverge posteriorly at 120⬚–130⬚, proximal end situated adjacent to frontal lobe, separated from glabella by axial furrow, although anteroproximal edge of eye ridge merges onto anterior margin of frontal lobe. Palpebral area moderately convex, width (tr.) at ⑀ approximately 50% adjacent glabellar width. Postocular area short (exsag.), of subequal length (exsag.) to sagittal length of occipital ring. Posterolateral projection of fixigena very wide, width (tr.) approximately 25% ⑀–⑀, strongly downsloping, strongly tapers abaxially. Posterior border strongly convex (exsag.), slightly expanding abaxially to fulcrum, then rapidly expands to distal end of border; small posterolaterally directed intergenal spine developed at distal extremity of posterior border; posterior border furrow deep, expanding abaxially, connecting with axial furrow at the posteroproximal portion of fixigena forming an L shape. Rostral plate moderately curved, following same curvature as anterior margin of cranidium, strongly convex dorsoventrally; uniform length (sag., exsag.), length approximately 25% width (tr.); rostral suture evenly curved; connective sutures concave abaxially; posterior margin smooth. Ventral surface with ridge extending along midlength, representing change in slope. Hypostome unknown. Librigena small, up to 7 mm in length; width (tr.) approximately 40% length; lateral margin strongly curved; lateral margin

← FIGURE 11—Pararaia bunyerooensis Jell in Bengtson et al., 1990. Silicified specimens from MMF/54.6, Mernmerna Formation (MMF section), unless otherwise stated. 1, Fragmentary cranidium (SAMP40644), dorsal view, stereo pair, ⫻7; 2, cranidium (SAMP40645), dorsal view, ⫻5.5; 3, right librigena (SAMP40650), dorsal view, ⫻6; 4, left librigena (SAMP40651), dorsal view, ⫻5.5; 5–7, cranidium (SAMP40646), ⫻8.5, 5, dorsal view, 6, anterior view, 7, lateral view; 8, fragmentary cranidium (SAMP40647) from MMF/93, dorsal view, ⫻6; 9, cranidium (SAMP40648) from MMF/93, dorsal view, ⫻7; 10, small cranidium (SAMP40649) from MMF/93, dorsal view, ⫻12.5; 11, 12, rostral plate (SAMP40656), ⫻6, 11, dorsal view, 12, ventral view; 13, 14, fragmentary thoracic segment (SAMP40657) from MMF/93, ⫻6, 13, dorsal view, 14, posterior view; 15, 16, right librigena (SAMP40652) from MMF/93, ⫻6, 15, dorsal view, 16, ventral view; 17, 18, small right librigena (SAMP40653), ⫻10, 17, dorsal view, 18, ventral view; 19, 20, pygidium (SAMP40658) from MMF/93, ⫻11, 19, dorsal view, stereo pair, 20, ventral view; 21, fragmentary pygidium (SAMP40659), dorsal view, ⫻13; 22, small left librigena (SAMP40654) from MMF/93, dorsal view, ⫻3.5; 23, 24, left librigena (SAMP40655), ⫻5, 23, dorsal view, 24, ventral view.

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TABLE 1—Comparison of diagnostic cranidial characters between species of Yunnanocephalus. Y. macromelos n. sp. Cranidial outline Anterior margin Glabellar length (sag) S2

trapezoidal width (tr.) 85%–95% ␦-␦ 80%–85% cranidial length (sag.) straight, transverse

Occipital ring

length (sag.) 15%–20% glabellar length; posterior margin weakly convex posteriorly absent lateral sections weakly convex anteriorly, medial section in front of glabella strongly convex anteriorly length (exsag.) 25%–30% cranidial length (sag.); anterior tip opposite L3; posterior tip opposite midlength of L1 diverge posteriorly at 120⬚–130⬚ width (tr.) at ␧ 50% adjacent glabellar width very wide, width (tr.) 25% ␧-␧

Preglabellar field Anterior border furrow Palpebral lobe

Eye ridges Palpebral area Posterolateral projection of fixigena Intergenal spine

present

Y. yunnanensis (Mansuy)

Y. longioccipitalis Palmer

subquadrate width (tr.) 85%–90% ␦-␦ 70% cranidial length (sag.) convex anteriorly, directed antero-laterally abaxially length (sag.) 20%–25% glabellar length; posterior margin weakly convex posteriorly 15%–20% cranidial length (sag.) moderately convex anteriorly across entire width (tr.)

trapezoidal width (tr.) 75%–85% ␦-␦ 80% cranidial length (sag.) convex anteriorly, directed antero-laterally abaxially length (sag.) 25%–30% glabellar length; posterior margin strongly convex posteriorly absent moderately convex anteriorly across entire width (tr.)

length (exsag.) 25%–30% cranidial length (sag.); anterior tip opposite S3; posterior tip opposite S1

length (exsag.) 30%–35% cranidial length (sag.); anterior tip opposite L3; posterior tip opposite S1

diverge posteriorly at 150⬚–160⬚ width (tr.) at ␧ 75%–85% adjacent glabellar width very narrow (tr.), extending slightly beyond palpebral lobe present

diverge posteriorly at 90⬚–100⬚ width (tr.) at ␧ 35%–45% adjacent glabellar width narrow, width (tr.) 10%–15% ␧-␧

and posterior section of facial suture converge at genal angle. Genal field of low convexity, width (tr.) 55%–65% librigenal width. Lateral border strongly convex, slightly tapers (tr.) posteriorly, anteriormost dorsal portion of border sharply tapers to a point; lateral border furrow shallow, narrow (tr.). Posterior border and posterior border furrow absent. Genal spine absent. Librigenal doublure width (tr.) mimics dorsal surface of lateral librigenal border and anterior cranidial border; sharp ridge developed on lateral margin of doublure (forming continuation of ridge on ventral surface of rostral plate), representing a change in slope from rounded lateral margin to wide (tr.), slightly concave adaxial portion. Thoracic segments with axis of strong convexity. Axial ring of uniform width (sag., exsag.), posterior margin slightly convex anteriorly; small posteromedial axial node well developed; articulating half ring of subequal length (sag.) to axial ring, tapering abaxially; articulating furrow straight, wide (sag., exsag.), equal depth across entire width. Pleura horizontal to fulcrum, then strongly downsloping to distal end; anterior pleural band expands abaxially, anterior pleural margin with projection at anterolateral corner; posterior pleural band expands abaxially; pleural furrow deep, terminating adjacent to projection at anterolateral corner of anterior pleural margin. Doublure of thoracic pleura developed at pleural tip and tapers adaxially along posterior margin. Pygidium unknown. Entire dorsal surface of exoskeleton densely covered in tiny granules. Morphogenesis.⎯Small cranidia of Yunnanocephalus macromelos (e.g., Fig. 12.15) show that there is considerable morphological variation during ontogeny and display the following characteristics: anterior sections of facial suture slightly converge

absent

anteriorly; narrower (tr.) anterior margin; glabella parallel-sided with rounded frontal lobe; S1 transglabellar, convex posteriorly; longer (exsag.) palpebral lobe; eye ridges more widely divergent posteriorly, proximal ends continue around frontal lobe to form prominent parafrontal band. Etymology.⎯Greek makros, long, and melos, limb; referring to the wide (tr.) posterolateral projections of the fixigenae. Type material.⎯Holotype: cranidium, SAMP40660 (Fig. 12.1– 12.5). Paratypes: four cranidia, SAMP40661–40664 (Fig. 12.12– 12.15, 12.26); three librigenae, SAMP40665–40667 (Fig. 12.6– 12.11); one articulated librigena and rostral plate, SAMP40668 (Fig. 12.25); one rostral plate, SAMP40669 (Fig. 12.16, 12.17); one thoracic axial ring, SAMP40670 (Fig. 12.20, 12.21); two thoracic pleurae, SAMP40671–40672 (Fig. 12.18, 12.19, 12.22– 12.24). Type locality.⎯Mernmerna Formation (MMF section), Hawker Group; base of section coordinates: 31⬚11⬘38.4⬙S, 138⬚52⬘28.7⬙E; map datum: WGS84, on the eastern side of The Bunkers, approximately 1 km south of Balcoracana Creek on Angorichina Station, Flinders Ranges, South Australia (see Figs. 2, 3). Type stratum.⎯Third Plain Creek Member of the Mernmerna Formation, MMF section, horizon MMF/64.5; 37 m (true thickness) above the base of the section (Fig. 4). Occurrence.⎯Pararaia bunyerooensis Zone, Third Plain Creek Member, Mernmerna Formation, MMF section horizons: MMF/ 44.5, MMF/52.4, MMF/58.3, MMF/64.5, MMF/68.7, MMF/75.2, MMF/81.5, MMF/82.6, MMF/103; 25.5–59.1 m (true thickness) above the base of the section (Fig. 4). Discussion.⎯There are currently three valid species of Yunnanocephalus: the type species Y. yunnanensis (Mansuy, 1912) from China; Y. longioccipitalis Palmer (in Palmer and Rowell, →

FIGURE 12—Yunnanocephalus macromelos n. sp. Silicified specimens from MMF/64.5, Mernmerna Formation (MMF section), unless otherwise stated. 1–5, Holotype cranidium (SAMP40660), ⫻6, 1, dorsal view, stereo pair, 2, posterior view, 3, lateral view, 4, ventral view, 5, oblique anterolateral view; 6, 7, right librigena (SAMP40665), ⫻8, 6, dorsal view, 7, ventral view; 8, 9, left librigena (SAMP40666), ⫻6.5, 8, dorsal view, 9, ventral view; 10, 11, left librigena (SAMP40667), ⫻7, 10, dorsal view, 11, ventral view; 12, 13, fragmentary cranidium (SAMP40661), ⫻6, 12, dorsal view, stereo pair, 13, anterior view; 14, small fragmentary cranidium (SAMP40662), dorsal view, ⫻10; 15, small cranidium (SAMP40663) from MMF/103, dorsal view, stereo pair, ⫻9; 16, 17, rostral plate (SAMP40669), ⫻8, 16, dorsal view, 17, ventral view; 18, 19, left thoracic pleura (SAMP40671), ⫻9.5, 18, dorsal view, 19, ventral view; 20, 21, fragmentary thoracic axial ring (SAMP40670), ⫻8, 20, dorsal view, 21, posterior view; 22–24, right thoracic pleura (SAMP40672), ⫻7, 22, dorsal view, 23, ventral view, 24, posterior view; 25, articulated left librigena and rostral plate (SAMP40668), dorsal view, ⫻8; 26, cranidium (SAMP40664), dorsal view, ⫻8.


137

138


FIGURE 13—Elicicola calva Jell in Bengtson et al., 1990. Testate cranidia from MMF/0.0, Wilkawillina Limestone (MMF section). 1, SAMP40673, dorsal view, stereo pair, ⫻5; 2, SAMP40674, dorsal view, ⫻4.5; 3, SAMP40675, dorsal view, ⫻4; 4, SAMP40676, dorsal view, ⫻5.5; 5, SAMP40677, dorsal view, ⫻9; 6–8, SAMP40678, 6, dorsal view, ⫻5, 7, lateral view, ⫻7, 8, oblique anterolateral view, ⫻5.

1995) from Antarctica; and Y. macromelos described herein. Several other species have also been described from China, but they are considered to be junior subjective synonyms of Y. yunnanensis (see Zhang, 1987, p. 229 and Shu et al., 1995, p. 222 for comprehensive synonymy lists). Comparison of diagnostic cranidial characters between species of Yunnanocephalus are outlined in Table 1. The librigenae of Y. macromelos (Fig. 12.6–12.11) and Y. longioccipitalis (Palmer in Palmer and Rowell, 1995, fig. 14.8, 14.9) are indistinguishable, but can be differentiated from the librigena of Y. yunnanensis (e.g., Zhang, 1987, pl. 1, figs. 1, 2, 4; Shu et al., 1995, figs. 17a, 19a–e) in displaying a wider (tr.) genal field. Genus ELICICOLA Jell in Bengtson et al., 1990 Type species.⎯Elicicola calva Jell in Bengtson et al., 1990, Early Cambrian, Parara Limestone, Kulpara, South Australia.

ELICICOLA

CALVA

Jell in Bengtson et al., 1990 Figure 13

Elicicola calva JELL IN BENGTSON, CONWAY MORRIS, COOPER, JELL, AND RUNNEGAR, 1990, p. 300, figs. 192j–m, 193.

Figured material.⎯Six cranidia, SAMP40673–40678 (Fig. 13.1–13.8). Occurrence.⎯Abadiella huoi Zone, Wilkawillina Limestone, MMF section horizon: MMF/0.0 (Fig. 4). Discussion.⎯This monotypic species has been well described and illustrated by Jell (in Bengtson et al., 1990) from the Parara Limestone at Kulpara (type locality) and the Wilkawillina Limestone at Wirrealpa Mine and west of Wirrealpa Springs in the Flinders Ranges, and requires no further discussion herein. ACKNOWLEDGMENTS

Sincere thanks to E. Alexander (PIRSA) for assistance and guidance in the field in September 2002 and for her continual

PATERSON AND BROCK—EARLY CAMBRIAN TRILOBITES FROM SOUTH AUSTRALIA support of our research on the Cambrian faunas of South Australia. T. Wright (PIRSA) also provided technical and logistical support during the September 2002 field season. We are indebted to MUCEP members P. Bell, H. Caldon, P. Cockle, B. Jonak, R. Morgan, B. Pyemont, D. Smith, L. Strotz, and N. Wilson for their assistance during the 2003 and 2004 field seasons. L. Strotz and P. Bell assisted with acid processing and picking of residues. Thanks also to the Fargher family (owners of Angorichina Station) for access to the field area. Discussions with J. Jago, J. Laurie, and P. Jell on various aspects of this paper were extremely beneficial. G. Edgecombe kindly read and commented on an early draft of the manuscript. N. Hughes and A. Rushton provided helpful reviews. D. Oliver drafted Figures 1–4. Funding for this study came from a Macquarie University Postgraduate Research Fund grant to JRP and a Macquarie University Research Development Grant to GAB. REFERENCES

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