Biostratigraphy and palaeobiogeography of the Cambrian genus ...

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nicharion hispanicum n. sp. represents the first Cambrian ostracod .... The material comes from locality AT2/4 at stream. Tamujar (Arroyo ... Stage by LIIqAN et al.
Pal~iontologische Zeitschrifl

76 (1)

65-74

5 Abb.

Stuttgart, A p r i l 2002

Biostratigraphy and palaeobiogeography of the Cambrian genus Hipponicharion (Ostracoda) RODOLFO GOZALO & INGELORE HINZ-SCHALLREUTER with 5 figures

Abstract: The bradoriid genus Hipponicharion MATTHEW, 1886 is one of the oldest known Cambrian ostracods. Until now, five species have been documented and another three taxa have been tentatively assigned to one or another species. Hipponicharion has been recorded from Poland, Germany, Morocco as well as from Canada and Great Britain. Hipponicharion hispanicum n. sp. represents the first Cambrian ostracod documented from Spain. Hipponicharion taidaltensis n. sp., formerly H. aft. geyeri HINZ-SCHALLREUTER,1993 and H. elickii n. sp., formerly H. cf. cos sensu ELICKI, 1994 have also been restudied in this paper. Hipponicharion seems to be restricted to the Acadobaltic Province sensu SDzuv (1972). The systematic relationships of the Bradoriida, which is controverse, is briefly outlined, emphasizing close affinities to the Ostracoda. Key words: Ostracoda, Cambrian, taxonomy, systematic relationships, biostratigraphy, palaeobiogeography Kurzfassung: Die Gattung Hipponicharion MATTHEW, 1886 geh6rt zu den altesten kambrischen Ostrakoden. Bisher wurden ftinf Arten nachgewiesen und drei weitere Taxa aus anderen Gattungen wurden der einen oder anderen Hipponicharion-Art zugewiesen. Die Gattung selbst ist sowohl aus Polen, Deutschland und Marokko als auch aus Nordamerika und Grol3britannien bekannt. Mit Hipponicharion hispanicum wurden erstmals kambrische Ostrakoden in Spanien nachgewiesen. Hipponicharion taidaltensis n. sp., vorher H. aft. geyeri HINZ-SCHALLREUTER,1993 und H. elickii n. sp., vormals H. cf. eos sensu ELICI,:I, 1994 wurden im Rahmen dieser Arbeit revidiert. Die gegenw~irtig sehr kontrovers diskutierten Verwandtschaftsbeziehungen der Bradoriida werden kurz erlautert, wobei die engen Beziehungen zu den Ostracoda betont werden. Schliisselw6rter: Ostracoda, Kambrium, Taxonomie, Verwandtschaftsbeziehungen, Biostratigraphie, Pal~iobiogeographie

Introduction H i p p o n i c h a r i o n i d a e SYLVESTER-BRADLEY, 1961 are a group o f C a m b r i a n o s t r a c o d s that are characterized b y c o m a r g i n a l lobation. T h e y b e l o n g to the oldest repre-

sentatives o f b r a d o r i i d ostracods. H i p p o n i c h a r i o n i d s are r e c o r d e d with 28 species out o f 8 g e n e r a from all over the world. C o n t r a r y to other f a m i l y m e m b e r s , the carap a c e o f the t y p e genus Hipponicharion MATTHEW, 1886 has a w e l l - d e v e l o p e d c o m a r g i n a l anterior and posterior lobe that are not fused ventrally. The oldest representative is H. elickii n. sp. f r o m the L o w e r C a m b r i a n of eastern G e r m a n y . H. cos and its j u n i o r s y n o n y m s H. cavatum andH. minus (see SIVETER & WILLIAMS 1997) c a m e from the H a n f o r d B r o o k F o r m a t i o n o f N e w B r u n s w i c k (Canada) w h i c h is B r a n c h i a n series in age (LANDING & WESTROP 1998; WESTROP • LANDING 2000). H. geyeri HINz-SCHALLREUTER, 1993 f r o m the l o w e r M i d d l e C a m b r i a n o f M o r o c c o and H. cf. eos sensu BEDNARCYZK, 1984 from the Eccaparadoxides insularis Z o n e o f Poland are the y o u n g e s t species. Hipponicharion has been docum e n t e d so far from N e w B r u n s w i c k , M o r o c c o , Poland, E n g l a n d and the D o b e r l u g - T o r g a u S y n c l i n o r i u m in Germany. The species r e c o r d e d f r o m A n t a r c t i c a (GA~DZICKI & WaONA 1987), is not identical to the t y p e - g e n u s concerning c a r a p a c e m o r p h o l o g y and p r o b a b l y belongs to the h i p p o n i c h a r i o n i d genus Albrunnicola MARTINSSON, 1979. T h e t y p e - g e n u s Hipponicharion w a s e s t a b l i s h e d b y MATTHEW (1886) who d e s c r i b e d v a r i o u s E a r l y and M i d dle C a m b r i a n b r a d o r i i d s p e c i m e n s f r o m Canada. A l m o s t s i m u l t a n e o u s l y WIMAN (1903) p u b l i s h e d representative s o f this genus which he had d i s c o v e r e d in the vicinity o f S t o c k h o l m . ULRICH & B ASSLER (1931) i n c r e a s e d the existing k n o w l e d g e on C a m b r i a n o s t r a c o d s with a detailed d e s c r i p t i o n o f N o r t h A m e r i c a n faunas. SIVETER & WILLIAMS ( 1 9 9 7 ) d e s c r i b e d Hipponicharion cos and two other h i p p o n i c h a r i o n i d s , Septadella plicatum (ULRICH & BASSLER, 1931) and Wimanicharion? confluens (ULRICH & BASSLER, 1931) in their d o c u m e n t a t i o n o f North A m e r i c a n b r a d o r i i d and p h o s p h a t o c o p i d arthropods. F r o m E u r o p e only few h i p p o n i c h a r i o n i d s are known, i.e. Neokunmingella sp., Hipponicharion cf. cos, H. sp. cf.

Addresses of the authors: Rodolfo GOZALO, Departamento de Geologfa, Universitat de Valencia, C/Dr. Moliner 50, E-46100 Burjassot, Spain; e-mail - Ingelore HINZ-SCHALLREUTER,Institut fiir Geologische Wissenschaften der Ernst-Moritz-Amdt-Universitat, Friedrich-Ludwig-Jahn Str. 17a, D-17487 Greifswald, Germany; e-mail 0031-0220/02/0076-0065

$ 2.50

9 2002 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart

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RODOLFO GOZALO & INGELORE HINZ-SCHALLREUTER

eos and Hipponicharion sp. indet. (BEDNARCYZK 1984; WILLIAMS & SIVETER 1998) as well as the two new taxa desribed herein, H. hispanicum n. sp. and H. elickii n. sp. Other representatives, H. geyeri HINZ-SCHALLREUTER, 1993 and H. taidaltensis n. sp. come from Morocco. Further records of hipponicharionids refer to South China and South Australia (see Huo & SHU 1985; BENGTSONet al. 1990) but they belong to other genera than the generotype. Until recently this genus was unknown from the Spanish Cambrian, although the latter is well-known for its diverse and continuous fossil record. However, occurrences of crustaceans are scarce and their assignment rather questionable. For example, Leperditia sp. was recorded from the Middle Cambrian of both the Cantabrian Mountains (MALLADA1875: 39; MALLADA & BUITRAGO 1878: 192) and Iberian Chains (PALACIOS 1893: 11). However, it is likely that these fossils may turn out to be small lingulate brachiopods which are very abundant at the horizons in question (see MERGL & LISAN 1986: 161). Another record of crustaceans is that of RICHTER & RICHTER (1927), who described the phyllocarid lsoxys carbonelli from the Lower Cambrian of C6rdoba. In addition, LISAN (1974, 1978) recorded Ovetian ostracods from the Pedroche Formation of Sierra de C6rdoba, but they remain unpublished. The single valve of Hipponicharion hispanicum from the Upper Marianian of the Ossa Morena Zone, described herein, confirms the general rarity of such material. Nevertheless, this paper presents the first evidence for the existence of Cambrian ostracods in Spain.

Material and methods The material comes from locality AT2/4 at stream Tamujar (Arroyo Tamujar), about 5 km south of Guadalcanal village in Sevilla Province (Fig. 1). Most probably this locality is identical with LOTZE'S (1961 ) and SDZUY'S (1962a) "Fundpunkt 1 bei Guadalcanal". At least, the sample horizon represents the same stratigraphic level. The specimens studied in this paper were discovered on the surface of a green shale rock slab by Prof. E. LNAN (Universidad de Zaragoza). Accompanying faunal elements are the trilobites Andalusiana cornuta and Termierella sevillana. The ostracod material consists of an incomplete internal mould and a fragmentary external mould of a right valve with a length of approximately 3.6 mm. The latter has been examined using scanning electronic microscopy (SEM). For this purpose the specimen was mounted as a sawn block of rock to a stub, with high vacuum wax, and coated with a gold-palladium alloy. The specimen is housed at the Museo Paleontol6gico de la Universidad de Zaragoza, number MPZ 98/1. Specimens studied herein from Morocco are housed at the Natural History Museum of Berlin, numbers MB.O. 327 and 328. The specimen studied from Germany is housed at the Geologisches Institut der TU Freiberg, number FG 410/1-1.

Regional setting and stratigraphy The Cambrian rocks of Arroyo Tamujar are part of the C6rdoba-Alanfs Domain (DELGADO et al. 1977), equivalent to the Zafra-Monesterio Domain (APALATEGUIet al. 1990) of the Ossa-Morena Zone (Fig. 1). Within the entire sequence, APALATEGUIet al. (1985) distinguished the following stratigraphical units in ascending order: Malcocinado Formation, Torrezirboles Formation, Calizas del Agua Beds, Benalija Beds and Arroyo Tamujar Beds. Of these stratigraphical units, the Benalija Beds represent the fossiliferous part of the sequence. They have been described by FRICKE (1941), LOTZE (1961) and APALATEGUIet al. (1985) and are more or less equivalent to the Alanfs Beds of SIMON (1951). They are composed of green shales that partly show reddish levels and with a few interbedded sandstones. Rare carbonates and carbonate nodules are intercalated. The lower part of the Benalija Beds correlates with the La Hoya Member of the Alconera Formation (LI~AN & PEREJON 1981); the top of the unit is equivalent to the Las Vegas Member of the La Lapa Formation (LIIqAN & PEREJON 1981).

Fossil assemblages and age In the Guadalcanal-Alanfs-Cazalla de la Sierra region, fossils from the Benalija Beds are known from several localities. Description of the fossils commenced with RICHTER & RICHTER (1940), who were the first to document the Saukianda fauna, which was subsequently studied by HENNINGSMOEN(1958) and SDZUY (1961, 1962a, b). Other localities were recognized by LOTZE (1961), with their fossil content described by SDZUY. The age of the Benalija Beds was determined as Marianian (Early Cambrian) by both SDZUY (1971) and LI~AN et al. (1993). However, according to APALATEGUI et al. (1985) the respective beds include three different fossil levels which may correspond to the three trilobite assemblages that had been proposed for the Marianian Stage by LIIqAN et al. (1993: 824). The assemblage recorded by SDZUY (1961, 1962a) for "Fundpunkt 1 bei Guadalcanal" comprises Andalusiana cornuta SozuY, 1961, Termierella sevillana SDZUY, 1961, Termierella sp. A, Termierella sp. B, Triangulaspisfusca SDZUY, 1962, as well as gen. et sp. indet. A and B. From "Fundpunkt 2", which is close to "Fundpunkt 1 bei Guadalcanal" he mentioned Serrodiscus speciosus silesius RICHTER & RICHTER, 1941. Both trilobite associations suggest that the stratigraphic level of the sample correlates with the third assemblage of LINAN et al. (1993), also it is Late Marianian in age because the FAD of the genus Serrodiscus is considered by LItqAN & GAMEz-VINTANED (1993) as indicative of this subage. The faunal association discovered at Arroyo Tamujar also points to a placement within the third LIIqAN assemblage (LIIqAN& PALACIOS 1983). The fauna consists of Serrodiscus sp. indet., Delgadella cf. souzai (DELGADO,

Biostratigraphy and palaeobiogeography of the Cambrian genus Hipponicharion (Ostracoda)

67

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Fig. 1. Distribution of Cambrian occurrences in the Ossa Morena Zone (modified from LINAN& QUESADA1990). * = studied area. 1904), Andalusiana cornuta SDZUY, 1961, Termiella sevillana SDZUY, 1961, Protaldonaia morenica SDZUY, 1961, Chancelloria sp., hyolithids, and inarticulate brachiopods. The locality investigated for this paper yielded an assemblage containing the following major fossil components: Serrodiscus speciosus silesius RICHTER & RICHTER, 1941, Delgadella cf. souzai (DELGADO,1904), Triangulaspis ziravii fusca SDZUY, 1962, Andalusiana cornuta SDZUY, 1961, Termierella sevillana SDZUY, 1961, Protaldonaia morenica SDZUY,1961 and Hipponicharion hispanicum n. sp. The trilobites are typical of the Late Marianian (LI~ANet al. 1993; LI~AN & GAMEZ-VINTANED 1993).

Biogeographic implications Bradoriids include cosmopolitan taxa such as the presumably pelagic Eremos MOBERG r SEGERBERG, 1906 and endemic representatives like the Oepikalutidae that are restricted to South China and Australia (HINZSCHALLREUTER 1999). Examples of provincialism outside the Hipponicharionidae refer to the genus Kunmingella Huo, 1956 which has been reported with certainty only from South China. The Siberian find of Konicekion k u n d a e n s i s MELNIKOVA,1987 illustrated by MELNIKOVA et al. (1997: pl. 1 fig. 7) is a poorly preserved right valve whose generic assignment remains questionable. Other representatives of the Sinian Province are the interdorsum-bearing phosphatocope Ulopsidae that are confined to Australia, whereas hesslandonids prevail in

Baltoscandia (HINz-SCHALLREUTER 1993). Although Hipponicharionidae as a whole are generally cosmopolitan, some hipponicharionids are confined to the Southe m Chinese-Australian region, whilst the genus Hipponicharion occurs in Avalonia as well as in Baltica and western Gondwana. According to HINZ-SCHALLREUTER(1993) and SIVETER WILLIAMS (1997), the genus Hipponicharion comprises H. e o s MATTHEW, 1886 and H. geyeri HINZSCHALLREUTER, 1993. Both, Hipponicharion cavatum MATTHEW, 1894 and Hipponicharion minus MATTHEW, 1894 were regarded as synonymous with H. eos by SIVETER & WILLIAMS (1997: 45). Further representatives of the genus are H. elickii n. sp., H. hispanicum n. sp. and H. taidaltensis n. sp. Their regional and biostratigraphic occurrences are given in Figs. 2 and 3. The oldest representative Hipponicharion is H. elickii n. sp. which comes from a core drill of the Doberlug area, eastern Germany. The taxon comes from the Upper Zwetau Carbonate M e m b e r which is Ovetian (Lower Cambrian) sensu ELICKI (1997, 1999) (see Fig. 3). Hipponicharion eos is distinctly younger, though still of Early Cambrian age. It occurs in the latest Early C a m brian Protolenus elegans Zone (see SIVETER& WILLIAMS 1997 and WESTROP& LANDING2000). H. taidaltensis n. sp. occurs in the upper Lower Cambrian of Morocco. The question of whether or not it is closely related to H. geyeri from the lower Middle Cambrian of the same region, cannot yet be answered, due to lack of sufficient material. Representatives of the family Hipponicharionidae are cosmopolitan, but the genus Hipponicharion is appar-

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RODOLFOGOZALO& INGELOREHINz-SCHALLREUTER

Fig. 2. Palaeogeographic distribution of Hipponicharion species (reconstruction span sensu MCKERROWet al. 1992). It = presence of Hipponicharion species.

ently confined to the Acadobaltic Province (sensu SDZUY 1972). Material from Antarctica which has been assigned to this genus (GA~'DZICKI• WRONA 1987; WRONA 1995) shows some differences with typical Hipponicharion species, particularly in the development of anterior and posterior lobes which are rather short compared to the long comarginal lobes of Hipponicharion. The record from Antarctica is a single fragment of a left valve with a short but prominent anterior lobe that somewhat resembles the anterior lobe in Albrunnicola MARTINSSON, 1979. However, the published figure does not permit a more precise determination. The geographic distribution of Hipponicharion (Fig. 2) compared with the known trilobite assemblages suggests strong palaeobiogeographic relations. Among Cambrian ostracods, the bradoriid Hipponicharion is thus considered to be a typical representative of the Acadobaltic Province.

Systematic palaeontology Class Ostracoda LATREILLE, 1806 Order Bradoriida RAYMOND, 1935 (nomen transl. & corr. IVANOVA1960) R e m a r k s : According to H o u et al. (1996), WILLIAMS&

SIVETER (1998) and SHU et al. (1999) bradoriids are small arthropods that superficially resemble ostracods but do not even belong to crustaceans. H o u et al. (1996) based their statement on the discovery of five specimens of Kunmingella maotianshanensis H u o & SHU, 1985 with partially preserved soft integument from the Early Cambrian Chengiang lagerst~itte of South China. They discussed differences of both hard-part and soft-part morphology between Kunmingella and extant ostracods.

However, as explained by MCKENZIE et al. (1999) such differences can be observed in various extant ostracod groups, e.g., punciids, halocypridids, podocopids and myodocopids. With that background, an exclusion of bradoriids from crustaceans and, thus, from the Ostracoda does not seem to be justified. Moreover, as bradoriids display many characters of typical ostracods, such as the longitudinal reduction of the body (HINz 1993; VANNIER & ABE 1995), the development of true hinges (JONES & MCKENZIE 1980; HINZ 1993) as well as sexual dimorphism and cytoidal reticulation (HtNZSCHALLREUTER 1999). MCKENZIE (pers. comm. 1998) noted: " I f the Bradoriida and Phosphatocopida are not primitive ostracodes, where do we look for the ancestral Ostracoda? The most obvious response is that these Cambrian taxa are primitive Ostracoda; this is also the simplest solution. And I believe more than ever that it is the best and most likely correct solution." Family Hipponicharionidae S YLVESTER-BRADLEY,1961 Genus Hipponicharion MATTHEW, 1886 Type species: Hipponicharion eos MATTHEW,1886. Further species: Hipponicharion elickii n. sp., Hipponicharion geyeri HINZ-SCHALLREUTER, 1993, Hipponicharion hispanicum n. sp., Hipponicharion taidaltensis n. sp.

Hipponicharion elickii n. sp. Figs. 4E, 5E 1994 Hipponicharion cf. eos.- ELICKI:fig. 7:5. Derivation of name: After O. ELICKI,Freiberg. Holotype: Right valve, damaged by preparation, FG 410/1-1

(Fig. 4E). Material: Only the figured specimen.

Biostratigraphy and palaeobiogeography of the Cambrian genus Hipponicharion (Ostracoda)

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Fig. 3. Correlation chart of the Lower and Middle Cambrian of the Acadobaltic Province. H = presence of Hipponicharion species (modified from GEYER 1990; LIIqANet al. 1993; GEYER & PALMER 1995; ELICKI 1997; SDZUY et al. 1999; RUSHTON 1999 and GEYER & SHERGOLD2000).

Type locality: Doberlug-Torgau Synclinorium, Germany. Type horizon: Upper Zwetau Carbonate Member (Early Ovetian, Lower Cambrian). D i a g n o s i s : M a x i m u m length 0.77 mm. Anterior and posterior lobes r e l a t i v e l y short and inflated, b e c o m i n g clublike ventrally. D i s t a n c e b e t w e e n ventral ends of lobes rather wide. D o r s a l p o r t i o n o f lobes gently tapering. A n t e r o d o r s a l node w e a k or missing. R e m a r k s : T h e s p e c i m e n f r o m the Z w e t a u Carbonate M e m b e r is p r e s e r v e d as a steinkern like all other previously r e c o r d e d r e p r e s e n t a t i v e s o f H i p p o n i c h a r i o n . During its original p r e p a r a t i o n a n d mounting on a S E M stub, the specimen sank in glue; its r e m o v a l was not undertaken b e c a u s e o f the h i g h risk o f fragmentation. Nevertheless, the typical and distinctive features of the lobation are clearly seen. C o m p a r i s o n : H. elickii n. sp. differs from the type species by its shorter and m o r e club-like lobes, that are ventrally m o r e distant to e a c h other than is the case in H. eos. F u r t h e r m o r e , the a n t e r o d o r s a l node, distinctly visible in H. eos, is o n l y w e a k l y d e v e l o p e d to lacking in H. elickii and d o e s not b r o a d e n ventrally. Differences with H. h i s p a n i c u m are g i v e n under that species.

H i p p o n i c h a r i o n h i s p a n i c u m n. sp. Figs. 4B, 5D

Derivation of name: After its occurrence in Spain. I-lolotype: Anterodorsally incomplete steinkern of a right valve, embedded in rock, MPZ 98/1 (Fig. 4B). Material: Only the figured specimen. Type locality: Arroyo Tamujar, loc. AT2/4, 5 km south of Guadalcanal village, Sevilla Province, Spain. Type horizon: Late Marianian (Lower Cambrian). D i a g n o s i s : Dorsal margin a p p r o x i m a t e l y straight. Lobes rather b r o a d but with r i d g e - l i k e crest. L o b e s b e c o m i n g increasingly subdued towards dorsal and ventral ends, the latter s t r o n g l y approach but do not reach each other. D e s c r i p t i o n : Carapace large, 3.6 m m long, outline subs e m i c i r c u l a r and postplete. M a x i m u m length of valve at about mid-height, m a x i m u m c o n v e x i t y is l o c a t e d midposteriorly. Dorsal rim broken, but in a c c o r d a n c e with other h i p p o n i c h a r i o n i d t a x a it is p r e s u m a b l y straight. F r e e m a r g i n e v e n l y d e v e l o p e d with narrow, w e l l - d e f i n e d m a r g i n a l rim. The latter is set off f r o m the rest o f the v a l v e b y a narrow, distinct c o m a r g i n a l furrow. L o b a t i o n consists o f two ridge-like lobes and a s u b d o r s a l node in slightly anterior-median position. A n t e r i o r lobe has broad curvature, r o u g h l y paralleling the anterior margin. The

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RODOLFO GOZALO & INGELORE HINZ-SCHALLREUTER

Fig. 4. Hipponicharion species. - A: Hipponicharion eos MATTHEW, 1886, lectotype, R O M Cat. no. 267 CM; carapace, right lateral view; length = 5.7 ram; Hanford Brook, New Brunswick, Lower Cambrian. - B: Hipponicharion hispanicum n. sp., M P Z 98/1; i n c o m p l e t e right valve; length = 3.63 ram; Arroyo Tamujar, AT2/4, L o w e r C a m b r i a n (Late Marianian). - C-D: Hipponicharion taidaltensis n. sp., Taidalt, western Anti-Atlas, Morocco, Issafen Formation, ?Sectigena Zone (Lower Cambrian). C. H o l o t y p e , MB.O. 327, right valve; length = 1.7 ram; D. Paratype, MB.O. 328, right valve; length --- 1.59 ram. - E: Hipponicharion elickii n. sp., h o l o t y p e , F G 410/1-1; right valve; length = 0.77 m m ; Doberlug-Torgau Sycnlinorium, U p p e r Z w e t a u Carbonate M e m b e r (Lower Cambrian).

Biostratigraphy and palaeobiogeography of the Cambrian genus Hipponicharion (Ostracoda)

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Fig. 5. Representatives of the genus Hipponicharion. - A: H. taidaltensis n. sp. B: H. geyeri HINZ-SCHALLREUTER,1993. C: H. eos MATTHEW,1886. D: H. hispanicum n. sp. E: H. elickii n. sp.

posterior lobe is only faintly curved and appears almost straight. Both lobes widen gently and steepen ventrally. Comparison: Hipponicharion hispanicum n. sp. is very similar to H. taidaltensis n. sp., but differs in the closer approach of the ventral ends of the lobes, and the latter are less ridge-like and extend more obliquely towards the straight dorsal margin. H. hispanicum n. sp. is distinguished from H. eos by its more rounded rather than a triangular to semi-elliptical outline. Furthermore, the lobes are lower and more ridge-like, with the furrow paralleling the free margin being narrower and thus more distinct than in H. eos. It differs from H. elickii n. sp. particularly in shape and curvature of the lobes. The latter are slender in H. hispanicum n. sp. contrary to the inflated lobes in H. elickii n. sp. In H. geyeri two approximately equal lobes are developed with inflated proximal parts that decrease considerably until they terminate below mid-height of the valve.

Hipponicharion taidaltensis n. sp. Figs. 4C-D, 5A 1993 Hipponieharion aft. geyeri n. sp. HINZ-SCHALLREUTER: 420. Derivation of name: After the type locality. Holotype: Carapace, MB.O.327 (Fig. 4C). Material: 5 specimens. Type locality: Taidalt, western Anti-Atlas, Morocco. Type horizon: Issafen Formation, ?Sectigena Zone (Lower Cambrian). Occurrence: Only at the type locality in the type horizon. Diagnosis: Maximum length 1.65 mm. Lobes narrow

and ridge-like, extending almost perpendicular towards the straight dorsal margin. Both dorsal and ventral ends of lobes gradually decreasing in height; ventral ends situated at some distance from each other. Anterodorsal node weak or lacking. Remarks: The specimens illustrated on Figs. 4C, D were originally referred to as Hipponicharion cf. geyeri (HINZSCHALLREUTE~ 1993: 420). However, closer inspection of the specimens suggests erection of a new species, H. taidaltensis n.sp., rather than an assignment to H. aft. geyeri. H. geyeri HINz-SCHALLREUTER,1993 has dorsally thickened comarginal lobes with the anterior lobe being distinctly longer than the posterior one. These particular features could not be recognized in the material herein referred to H. taidaltensis n. sp. By contrast, the specimens of H. taidaltensis have lobes that are fairly similar to H. eos. The posterior lobe extends almost straight, the anterior lobe is more curved in accordance to the anterior margin. A subdorsal node, however, could not be observed, which might be due to preservation since the specimens appear very much recrystallized. This fact also prevents any comparison of the outer surface structure with H. geyeri. The assignment to H. taidaltensis n. sp. is also more in accord with the stratigraphical occurrence of the species. H. geyeri is the youngest yet recorded hipponicharionid from the lower Middle Cambrian, while H. hispanicum n. sp. andH. taidaltensis n. sp. from Spain and Morocco represent a late Early Cambrian age. By contrast, H. elickii n. sp. from Doberlug, Germany, is the oldest representative assigned to Hipponicharion being of middle Early Cambrian age.

72

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Conclusions

Ausdruck in der Geh~iusemorphologie findet (HINz 1993; HINZ-SCHALLREUTER1999).

Apart from c o s m o p o l i t a n bradoriids such as the pelagic

Eremos MOBERG & SEGERBERG, 1906 there are obviously strictly endemic bradoriid taxa like the Oepikalutidae that are restricted to South C h i n a and Australia. Although the Hipponicharionidae in total is a cosmopolitan taxon, the type genus seems to be restricted to the Acadobaltic Province (sensu SDZUY 1972). Other hipponicharionids clearly occur to the Sinian Province. With the determination of three n e w species, the genus Hipponicharion is now represented by five species which can be used as a biostratigraphic tool to determine an Early or early Middle C a m b r i a n age. In addition, the restriction of the genus to the Acadobaltic Province may be helpful for palaeogeographic reconstructions, particularly in the location of terranes.

Acknowledgements We wish to thank Prof. E. LI~AN (Zaragoza) for his help in field work and useful suggestions in the course of manuscript revision. We are also deeply indebted to Dr. R. SCHALLREUTER (Hamburg) for his critical comments and help in SEM. Thanks are due to Dr. R JONES, Canberra, and Dr. M. WILLIAMS, Keyworth, for critically reading the manuscript, as well as to Dr. G. GEYER, Wtirzburg, and Dr. D.J. SIVETER, Leicester, for their valuable comments. R. GOZALO acknowledges support from the Direcci6n General de Investigaci6n Project BTE20001145-C02 01, I. H1Nz-SCHALLREUTER from the German Research Council (DFG). This paper is a contribution to the I.G.C.P. Project 351 "Early Paleozoic Evolution in NW Gondwana".

Literature Zusammenfassung Die Hipponicharionidae bilden eine Gruppe kambrischer Ostrakoden, die sich durch randparallele Lobation auszeichnet. Hipponicharioniden sind bisher weltweit mit 28 Arten aus 8 Gattungen aus dem Unter- und Mittelkambrium nachgewiesen. Die Typusgattung der Familie, Hipponicharion MATTHEW, 1886, hat im Gegensatz zu anderen hipponicharioniden Gattungen je eine deutlich ausgebildete randparallele vordere und hintere Rippe, die sich aber ventral nicht vereinigen. Hipponicharion ist gegenw~irtig mit sechs Arten beschrieben. Der ~ilteste Vertreter ist H. elickii n. sp. aus dem unteren Kambrium Deutschlands. H. eos und die nach SIVETER& WILLIAMS(1997) mit ihm synonymen H. cavatum und H. minus stammen aus der Hartford Brook Formation Avalonias, die nach LANDING& WESTROP(1998) in das hrhere Unterkambrium geh6rt und dem Intervall Botom-Toyon in Sibirien bzw. den Branchian Series im stidrstlichen Neufundland zugeordnet werden k6nnen. H. geyeri aus dem tiefen Mittelkambrium Marokkos ist die jtingste Art. Basierend auf pal~iogeographischen Daten scheint die Gattung hinsichtlich ihrer Verbreitung auf den Gondwanabereich beschr~inkt zu sein. Das jetzt erstmals aus Spanien beschriebene Hipponicharion hispanicum n. sp. ftigt sich hervorragend in das Verbreitungsschema ein. Lediglich das aus der Antarktis nachgewiesene Hipponicharion (GA~'DZICKI & WRONA 1987) fallt aus diesem Verbreitungskreis heraus. Bei n~iherer Betrachtung ist jedoch offensichtlich, dab sich die Geh~iusemerkmale nicht mit denen von Hipponicharion s.str. decken. Die antarktische Form besitzt lediglich einen vorderen und hinteren Nodus, nicht aber deutlich ausgebildete, randparallele Rippen. Insofern dtirfte es sich um eine andere Gattung innerhalb der Hipponicharionidae handeln. Die Hipponicharionidengeh6ren zur Gruppe der Bradoriida, die neben den Phosphatocopa als eine eigene Ordnung kambrischer Ostrakoden angesehen wird. Basierend auf der kambrischen Kunmingella maotianshanensis Huo & SHU, 1985 aus der stidchinesischen Chenjiang-Fauna wurden die Bradoriida nicht nur aus den Ostrakoden, sondern sogar aus der Gruppe der Crustacea ausgeschlossen (Hou et al. 1996). Die von den Autoren angeftihrten Abweichungen sowohl hinsichtlich der Hartteil-, als auch der Weichk6rperanatomie sind samtlich nicht als Ausschlusskriterien geeignet, da sie auch bei sog. ,,echten" Ostrakoden rezent nachzuweisen sind (McKENZIE et al. 1999). Dartiber hinaus zeigen gerade die Bradoriida sehr viele Gemeinsamkeiten mit ,,echten" Ostrakoden, wie z.B. die Ausbildung von Schlrssern, sekund~tre Geschlechtsmerkmale, zytoide Retikulation und nicht zuletzt auch ihre graduelle k6rperliche L~ingenreduktion, die ihren

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Eingang des Manuskriptes am 5. April 2000; Annahme durch die Schriftleitung am 15. August 2001.