lower devonian - BioOne

Journal of Vertebrate Paleontology 21(4):639–650, December 2001 q 2001 by the Society of Vertebrate Paleontology

NEW CORVASPIDS FROM THE LOCHKOVIAN (LOWER DEVONIAN) OF SEVERNAYA ZEMLYA, RUSSIA (VERTEBRATA: PTERASPIDOMORPHI: HETEROSTRACI) ¯ TE ˙ -TALIMAA2 ALAIN R. M. BLIECK1 and VALENTINA N. KARATAJU U.S.T.L., Sciences de la Terre, UPRESA 8014 et FR 1818 du CNRS, F-59655 Villeneuve d’Ascq cedex, France, [email protected]; 2 Geologijos Institutas, Sˇevc˘enkos g. 13, LT-2600 Vilnius, Lithuania, [email protected]

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ABSTRACT—The new genus and species Corveolepis elgae is described from the Lochkovian, Severnaya Zemlya formation of October Revolution Island, Severnaya Zemlya. It is ascribed to the family Corvaspididae whose diagnosis is corrected. Corvaspis arctica Loeffler and Dineley is designated as the type species of Corveolepis. Previously described taxa such as ‘‘Corvaspis kingi’’ auct. and Corvaspis graticulata Dineley from Spitsbergen are included with doubt in Corveolepis. Other new material includes Corveolepis? sp. cf. C.? graticulata from the Lochkovian, Pod’emnaya formation of October Revolution Island. This material is used as supporting evidence for a correlation of Lower Devonian vertebrate-bearing strata between Severnaya Zemlya and Spitsbergen.

INTRODUCTION The sediments of Severnaya Zemlya (Kara-Tajmyr paleocontinent) are key to an understanding of the paleogeographical relationships of the Old Red Sandstone Continent and Siberia in Mid-Paleozoic times. Its Upper Silurian and Devonian sedimentary sequence bears a rich fauna of heterostracan vertebrates which enables biostratigraphical correlations with Spitsbergen (on the Barentsian paleocontinent), the Canadian Arctic (on the Old Red Sandstone Continent), and Central Tajmyr-NW Siberia (Siberian paleocontinent). This fauna is composed of various assemblages from the Ludlow (Upper Silurian) to the Frasnian (Upper Devonian), with the richest assemblages in the upper Lochkovian and a gap in the Emsian (Lower Devonian). Among these assemblages, corvaspid material has been collected in the Lochkovian, Severnaya Zemlya, and Pod’emnaya formations. This paper focuses on this material. Corvaspids are a poorly-known group, generally being represented in collections by disarticulated and incomplete elements of the cephalic carapace and the trunk. However, some partly-articulated specimens have now been found in the Severnaya Zemlya formation of Sovetskaya Bay and the Pod’emnaya River, on October Revolution Island in the Severnaya Zemlya archipelago (Fig. 1). These new specimens are attributed to the new genus and species Corveolepis elgae and enable a re-interpretation of the external morphology of corvaspids. Comparisons are made with material from the Canadian Arctic (e.g., Corvaspis arctica Loeffler and Dineley, 1976, re-assigned to Corveolepis, gen. nov.), Spitsbergen (e.g., ‘‘Corvaspis kingi’’ and ‘‘C.’’ graticulata auct.), and Britain (the type species Corvaspis kingi Woodward, 1934). MATERIALS AND METHODS The corvaspid remains presented in this paper were collected on October Revolution Island in 1978 (V. N. Karataju¯te˙-Talimaa and J. J. Valiukevicˇius) and in 1979 (E. Mark-Kurik) in the two lowermost formations of the Lower Devonian. The most productive level for vertebrate remains was found in the uppermost part of the Severnaya Zemlya formation in a layer of argillites This is a contribution to IGCP project n8 406 ‘‘Circum-Arctic Lower– Middle Palaeozoic Vertebrate Palaeontology and Biostratigraphy’’

with thin interbeds of limestones and numerous nodular calcareous concretions of different size and form (12–15 cm long and 2–3 cm wide). More rarely, remains of vertebrates are found preserved in thin interbeds of dark grey limestone. This level of the Severnaya Zemlya formation, with approximately the same lithological composition, was found in all the studied sections on the island (rivers Matusevich, Ushakov, Pod’emnaya, and Spokojnaya) and in the district of Sovetskaya Bay. The best preserved remains of corvaspids were found in the western part of October Revolution Island in the Pod’emnaya section (n8 4, Figs. 1, 2), and in the bank of a small stream, in the outcrop 28, northeast of Sovetskaya Bay near the Al’banov Glacier (n8 5, Fig. 1). No vertebrate remains have been mentioned in the equivalent deposits of the Severnaya Zemlya formation on the other islands of the archipelago (Komsomolets and Pioneer islands) (Khapilin, 1982). Fragments of corvaspid armour were also found in red argillites of the Pod’emnaya formation in the bank of the Matusevich River (n8 1, Figs. 1, 2: outcrop 4, bed 11). Their ornamentation is similar to that of Corvaspis graticulata from Spitsbergen. In the bank of Ushakov River (Figs. 1, 2: n8 2), intact plates of Phialaspis, fragments of plates and scales of amphiaspids, but rarely corvaspid scales were sampled. In the bank of Spokojnaya River (n8 3, Figs. 1, 2), a rather large fragment of plate (2 cm long by 1.5 cm wide) also similar to C. graticulata was found. The specific composition of the heterostracan assemblages of the Severnaya Zemlya and Pod’emnaya formations is quite different (Blieck and Karataju¯te˙-Talimaa, in press), which seems to be linked to different conditions of deposition and environment (Matukhin and Menner, 1999; Ma¨nnik et al., in press). The specimens are preserved in non-calcareous siliciclastic rocks and have been prepared by mechanical means (needles) under a binocular microscope. All specimens are incomplete so that the measurements for both the dorsal and ventral shields of the cephalic carapace are partly estimated. Nevertheless, we have compared these to the measurements defined for corvaspids by Loeffler and Dineley (1976). The specimens are deposited in the Lithuanian Institute of Geology, Vilnius, Lithuania (prefixed LIG). STRATIGRAPHY Detail of the stratigraphy of the corvaspid localities is described in two recent papers (Matukhin and Menner, 1999;

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Ma¨nnik et al., in press). We have used here the series of stratigraphical logs published by Matukhin and Menner (1999:fig. 8) to plot the corvaspid-bearing beds of the different sections (Fig. 2), except for the Sovetskaya Bay log which is not described by Matukhin and Menner (1999). The numbers of the logs refer to the corresponding numbers in Blieck and Karataju¯te˙-Talimaa (in press:fig. 2) who describe the different heterostracan assemblages encountered through the Lochkovian Severnaya Zemlya and Pod’emnaya formations, and give the general trend of evolution of the fauna (see also Karataju¯te˙-Talimaa and Blieck, 1999). The age of the Severnaya Zemlya Formation is early Lochkovian, based upon its co-occurring vertebrate (heterostracans, acanthodians) and invertebrate (ostracodes) fauna. The age of the overlying Pod’emnaya Formation (which has yielded the richest vertebrate fauna of the Devonian of Severnaya Zemlya) is late Lochkovian based on its co-occurring ostracodes, heterostracans, and acanthodians (Matukhin and Menner, 1999; Ma¨nnik et al., in press). SYSTEMATIC PALEONTOLOGY Class PTERASPIDOMORPHI Goodrich, 1909 Subclass HETEROSTRACI Lankester, 1868 Order CORVASPIDIFORMES Stensio¨, 1964 Family CORVASPIDIDAE Dineley, 1955 Corrected Diagnosis The dorsal shield comprises either a single plate enclosing the orbits (and the branchial openings?) or an assemblage of nine separate plates: unpaired rostral, pineal and median dorsal plates; paired orbital, dorsolateral, and branchial plates (no rostral plate has ever been convincingly published, but such a plate and a pattern with nine plates is known on new, unpublished species of the Canadian Arctic [R. Thorsteinsson, pers. comm., 1987]). A possible pineal plate is figured on Corvaspis kingi by Tarlo (1965:pl. III:5; ‘‘lateral plate, showing haphazard arrangement of ornamentation’’ in Tarlo, 1960:pl. 37:5). No pineal opening (a single specimen of Corveolepis arctica [Loeffler and Dineley, 1976:fig. 2C, pl. 114:1] shows an opening in the center of the pineal region, which was interpreted as an abraded pineal macula). Median dorsal plate narrow and symmetrical. Orbits rounded and dorsolaterally placed. The dorsolateral plates (variously interpreted as either fragmentary median plates or postorbital plates by, e.g., Tarlo, 1960) are asymmetrical and arcuate. The branchial plates of Corvaspis kingi (ridge plates of Dineley, 1955:pl. II: 2) are incompletely known, narrow, longitudinally arcuate, and transversely arched at an angle of about 1658. The ventral shield comprises at least a median ventral plate (5ventral disc). Numerous isolated, asymmetrical small plates, often referred to as tesserae, may in fact correspond to elements of the anterior part of the ventral shield (oral, postoral, and/or orolateral platelets). The ornamentation is arranged in superficial tesseriform units, which are interpreted as separate tesserae when broken off the carapace. Each unit bears external longitudinal, smooth and rather wide dentine ridges. These units and the edges of the plates may be bounded by areas of small closely packed tubercles. The ornamentation of the median dorsal, dorsolateral, and ventral plates is less fragmented into tesseriform units, and arranged in more continuous, longitudinal ridges. However, it is organized in scale-like units along the posterior margin of the dorsal shield. The trunk scales are rhombic with a flat-topped crown and a wide anterior overlap area above a thick, anteriorly protruding, anchoring process. Their crown bears wide longitudinal ridges with one or several rows of anterior tubercles. Sensory line system poorly known. This family may prove not to be monophyletic. Type Genus Corvaspis Woodward, 1934.

FIGURE 1. Map of the Russian Arctic regions (below) with enlargement of the northern Severnaya Zemlya archipelago (top). Numbers 1– 4 refer to the stratigraphical logs described in Figure 2, and number 5 indicates Sovetskaya Bay.

CORVEOLEPIS, gen. nov. Corveolepis, Halstead 1993:574 (nomen nudum). Preliminary Comment This genus name was introduced by Halstead (1993:574) for Corvaspis arctica Loeffler and Dineley (1976), but with no comment on this assignment, no diagnosis for the genus, and no type species designated. So it must be considered as a nomen nudum (ICZN, 1999:article 13). However, we validate this name here because: (1) it has not been used for another concept to our knowledge (ICZN, 1999: 111); and (2) C. arctica does correspond to a genus different from Corvaspis, as explained here below. Diagnosis Dorsal shield fused (with no separate plates), long (90 mm to more than 125 mm), and narrow (maximum width 40 to 80 mm). The ornamentation is variable: closely spaced dentine ridges, commonly less than 3 mm long, locally grouped into small tesseriform units, separated by grooves or by rows of tubercles. Anterior units with peripheral ridges curved around median ridge, posterior units scale-like, and intermediate units with parallel ridges, more or less continuous

¯ TE˙ -TALIMAA—LOWER DEVONIAN CORVASPIDS BLIECK AND KARATAJU

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FIGURE 2. Stratigraphical logs of the Severnaya Zemlya and Pod’emnaya formations on October Revolution Island, Severnaya Zemlya (after Matukhin and Menner, 1999:fig. 8). Logs 1 to 4 refer to localities 1–4 of Blieck and Karataju¯te˙-Talimaa (in press): 1, Matusevich River; 2, Ushakov River; 3, Spokojnaya River; 4, Pod’emnaya River. Each corvaspid-bearing bed is referenced by the number of the outcrop section along one of the rivers of October Revolution Island [d], and the number of the bed in the section [c] (Matukhin and Menner, 1999:fig. 2; Ma¨nnik et al., in press). Key: a, lithostratigraphic log; b, colour of rock; c, beds, with corvaspid-bearing beds indicated by symbols; d, section; e, formation; f, subformation; 1, limestones; 2, dolomitic marls; 3, sandstones with conglomerates; 4, sandstones; 5, siltstones; 6, shales; 7, grey; 8, red and variegated; 9, erosional surface; 10, Corveolepis elgae, gen. et sp. nov.; 11, Corveolepis? sp. cf. C.? graticulata; 12, Corvaspididae gen. et sp. indet.

in the central part of the shield. The ridges of the central part of the shield may be sinuous. Ridges 0.2–0.5 mm wide (2–5 per mm). The anterior part of the shield encloses the two dorsolaterally located orbits. The dorsal shield of C. arctica laterally comprises two ventrolateral laminae which may be homologous to branchial fields, but the external branchial openings have not been observed on either species. Apparently no roof-shaped ridge scales on the trunk. Sensory line system poorly known. Type Species Corvaspis arctica Loeffler and Dineley, 1976. Referred Species Corveolepis arctica (Loeffler and Dineley, 1976), C. elgae, sp. nov. and perhaps ‘‘Corvaspis kingi’’ auct. and ‘‘Corvaspis’’ graticulata Dineley 1955 from Spitsbergen. CORVEOLEPIS ELGAE, sp. nov. (Figs. 3–7) Corvaspis, Kurik et al., 1982:69. Corvaspis cf. kingi Woodw. [sic], Karataju¯te˙-Talimaa, 1983:22. Corvaspis sp. nov., Karataju¯te˙-Talimaa et al., 1986:255.

Corvaspis sp. cf. kingi, Karataju¯te˙-Talimaa and Blieck, 1999: 129, table 20. Corvaspis sp. cf. C. kingi, Blieck and Karataju¯te˙-Talimaa, in press, fig. 4. Etymology Dedicated to Dr. Elga Mark-Kurik of the Tallinn Technical University, Estonia who has worked extensively on Devonian vertebrates from the Arctic regions, and has collected the best-preserved specimen of this new species. Holotype LIG 35-333, a partly-articulated dorsal shield and trunk. Type Locality Locality 28-1, NE of Sovetskaya Bay, along a small stream near to the Al’banov Glacier (ca. 600 m from the glacier when it was sampled); west coast of October Revolution Island, Severnaya Zemlya archipelago (Fig. 1: n8 5). Stratigraphic Horizon Severnaya Zemlya Formation, bed equivalent to the upper part of the Severnaya Zemlya Formation, lower Lochkovian, Lower Devonian. Referred Specimens LIG 35-330 and slide n8 1296 (paratype), a fragmentary head carapace with parts of both the dorsal and ventral shields; LIG 35-431 and 35-432 (syntypes), natural external molds of dorsal shields; LIG 35-417 (syntype),

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FIGURE 3. Corveolepis elgae, gen. et sp. nov. Holotype LIG 35-333. Anterior to the top. A, dorsal view of left and posterior part of the dorsal shield, and anterior part of the trunk; the white arrows indicate the boundaries between the median region of bigger scales and the lateral regions

¯ TE˙ -TALIMAA—LOWER DEVONIAN CORVASPIDS BLIECK AND KARATAJU fragment of trunk squamation; LIG 35-544 (syntype), internal mold of a probable dorsal shield (C. elgae?); from locality 6712 (Fig. 2: n8 4), along a left tributary of Pod’emnaya River, western part of October Revolution Island, Severnaya Zemlya (LIG 35-330, 35-431, and 35-544); and locality 1-21 (Fig. 2: n8 1), along the left bank of Matusevich River, central part of October Revolution Island, Severnaya Zemlya (LIG 35-432 and 35-417); all from uppermost part of the Severnaya Zemlya Formation, lower Lochkovian, Lower Devonian. Diagnosis A bigger species than C. arctica, with a dorsal shield longer than 125 mm and ca. 80 mm wide. Orbits enclosed in the dorsal shield. Superficial ornamentation of the dorsal shield highly variable. This ornamentation is made of closely spaced dentine ridges grouped into tesseriform units, generally separated by grooves and locally by rows of small tubercles on the lateral parts of the shield; it is made of closely spaced longer, continuous dentine ridges on the central part of the dorsal shield. These ridges may have a sinuous pattern, and are arranged in a fan-shaped design towards the front part of the shield. The ridges are rather wide, with 3–4 ridges per mm on various parts of the dorsal shield. The ornamentation of the ventral disc is more homogeneous and made of tesseriform units with a regular antero-posterior pattern, and without intermediate rows of tubercles. These tesseriform units are smaller than the dorsal ones; they are narrower on the lateral parts of the ventral disc and wider on the central part of the disc. Their dentine ridges are as wide (3–4 ridges per mm) as on the dorsal shield. The dentine ridges of both the dorsal and ventral shields have finely crenulated lateral margins. The squamation of the trunk, behind the dorsal shield, consists of three longitudinal zones. This squamation does not seem to contain a median dorsal row of roof-shaped ridge scales. Description None of the described specimens is complete, but each of them provides complementary information on different parts of the body of Corveolepis elgae, gen. et sp. nov. Several parts are still unknown, including the rostral region of the dorsal shield, the anterior region of the ventral shield, the ventral part of the trunk, and the tail. No branchial notches or openings have been observed. Specimen LIG 35-333 is a flattened, fragmentary portion of the left and posterior part of the dorsal shield and probably the anterior two thirds of the trunk (crushed dorsal face). It is preserved as dark-grey bone on lighter grey matrix. These preserved elements correspond to a length of about 210 mm, thus to an animal approximately 300 mm long (Fig. 3). The posterior part of the dorsal shield is poorly-preserved as a worn, internal mold (Fig. 3A). The left lateral part of the dorsal shield shows more well-preserved bone although fragmented in several parts. This part of the shield is superficially divided into short dentine ridges grouped into tesseriform units. Each unit is 1.5–2 mm wide and 2–3 mm long. The dentine ridges are rather wide (3–4 per mm). The tesseriform units are separated from each other mostly by grooves, and sometimes by intermediate rows of small tubercles (Fig. 3B). A series of external pores of the lateral line system (sensory canal system) forms a line 1 cm from the left lateral edge of the shield and parallel to it. It corresponds to the left lateral dorsal line of the sensory canal system (Fig. 3B). The rear part of the specimen probably corresponds to the anterior two thirds of the trunk, and is flattened dorsally (Fig. 3A). This area is covered by small densely packed, rhombic scales which have mostly been displaced and rotated, due to compaction and/or a very short post-

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mortem episode of decay (Fig. 3C). However, in some places, patches of scales are still imbricated. This squamation shows a unique pattern for heterostracans: it is composed of three longitudinal zones, one median zone of bigger scales (1.5–2.5 mm wide, 2–2.5 mm long) and two lateral zones (one left, one right) of smaller scales (1–1.5 mm wide, 1.5 mm long). No median dorsal row of roof-shaped ridge scales can be observed. Depending on their size, most crowns of the scales bear 5–7 longitudinal dentine ridges and sometimes up to 11–12 ridges. These ridges are as wide as those on the dorsal shield (4 ridges per mm). On the best-preserved scales these ridges have finelycrenulated lateral margins, as on the dorsal shield. Specimen LIG 35-330 is a very fragmentary specimen with part of the dorsal shield and part of the ventral shield in contact. It is preserved as yellowish brown bone in a nodule-like concretion. A series of natural external molds of the squamation is also visible at the left posterior corner of the preserved part of the dorsal shield (Fig. 4B). The dorsal shield, as preserved, is about 125 mm long and 70 mm wide, and is thus similar in size to the holotype LIG 35-333. Based on the location of the mid-line of the shield (which is seen by the faint impression of the brain on the internal mold, Fig. 4B) the maximum width of the dorsal shield is about 80 mm. At the right anterior corner of the dorsal shield, part of the orbital region is preserved as a broken piece of bone, with its ventral rim on the other side of the specimen. It does not seem to correspond to a separate orbital plate but to the orbital field of the dorsal shield with its orbit enclosed (Fig. 4C). However, in the absence of other wellpreserved specimens in our sample, the evidence for this feature is weak. The ornamentation of LIG 35-330 is also made of tesseriform units with closely packed, rather wide dentine ridges (4 per mm). These units are 1.5–2 mm wide and about 2 mm long, with 3–7 ridges on each unit. They usually show no intermediate rows of tubercles (Fig. 4D). Towards the center of the dorsal shield, these tesseriform units become bigger with more continuous, longitudinal ridges which sometimes have a sinuous pattern. The dentine ridges have a fan-shaped pattern at the anterior edge of the preserved part of the dorsal shield: they diverge symmetrically from the mid-line of the shield (Fig. 4B). A series of pores of the right lateral dorsal line has been observed on the posterior right portion of the shield (Fig. 4D). No pores of the median dorsal lines are observed on this specimen or on LIG 35-333. The other side of LIG 35-330 corresponds to part of the ventral shield which is very crushed and fragmentary on its anterior and right portions. A few fragments of the dorsal shield, with its typical tesseriform ornamentation are seen on the right anterior corner. The anterior part of the ventral shield is so crushed that it looks like a pavement of isolated tesserae with sometimes only one or two longitudinal dentine ridges (Fig. 5). This region may correspond to either the oral cover, in front of the ventral disc, or the anterior part of the ventral disc (after compaction and distortion). Behind this disturbed region is a large fragment of the ventral disc. It is made of closely packed, regularly arranged tesseriform units without intermediate rows of tubercles. The general pattern is strictly longitudinal (antero–posterior). No sinuous pattern is observed here. The dentine ridges are as wide as on the dorsal shield (3–4 ridges per mm) (Fig. 4A), and with finely crenulated lateral margins. However, the tesseriform units are not uniform all over the disc, they are wider on its central part (1– 1.2 mm wide, 2 mm long; on right part of Fig. 4A), and narrower on its lateral parts (0.7–0.8 mm wide, 2 mm long; on left

← of smaller scales; B, detail of the left lateral margin of the dorsal shield; C, detail of the squamation of the posterior part of the preserved trunk (same scale bar for B, C).

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FIGURE 4. Corveolepis elgae, gen. et sp. nov. Paratype LIG 35-330. Anterior to the top. A, detail of ornamentation of the ventral disc; B, dorsal view of the fragmentary dorsal shield; C, detail of the right orbital region of B; D, detail of ornamentation of the right posterior part of


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FIGURE 6. Corveolepis elgae, gen. et sp. nov. Syntype LIG 35-432. Anterior to the top. Detail of the pattern of dentine ridges of the pineal region.

FIGURE 5. Corveolepis elgae, gen. et sp. nov. Paratype LIG 35-330. Anterior to the top. External face of the ventral shield, with its dislocated front part (same specimen as Fig. 4A).

part of Fig. 4A which corresponds to the right lateral part of the ventral disc). No pores of the sensory canal system are seen on this ventral disc. Two other specimens of the type series, LIG 35-431 and 35432, are natural external molds of parts of dorsal shields preserved within concretions. Their superficial ornamentation is made of tesseriform units of the same kind as LIG 35-333 and 35-330. However, on LIG 35-431, these units have a more sinuous and convoluted pattern. The anterior part of LIG 35-432 shows the pineal region with the pineal macula and the fanshaped pattern of the dentine ridges (Fig. 6). Histology The most complete account of the histology of corvaspid scales was provided by Gross (1961:fig. 9; Corvaspis sp. indet. from the Beyrichienkalk erratics of northern Germany). The inner structure of the shield of Corvaspis kingi was described by Bystrov (1955:figs. 20–21). A vertical section showing the structure of the superficial layer of the shield of

← B, with location of external pores of the right lateral dorsal line (arrows).

the same species from Earnstrey Hall (Shropshire, England) was illustrated by Tarlo (1964:pl. IX, 2), with details of the pulp canals and dentine tubules. The inner structure of the shield of Corveolepis elgae, gen. et sp. nov. is similar to that of Corvaspis kingi. The superficial layer of the shield consists of dentine ridges (Fig. 7A:a). The dentine tubules arise in clusters from small pockets protruding from the pulp canal or canals. The clusters are often connected with transverse arcade canals (‘‘Arkadenkanal’’ of Gross, 1961) (Fig. 7B:arc). The dentine tubules in the upper layer of the ridges are very regularly arranged. There are usually one or two rows of pulp canals in each dentine ridge (Fig. 7B:pc). The middle and basal layers consist of spongy aspidin bone. As in all corvaspids, the gross structure of the middle layer is determined largely by a complex meshwork of canals. The middle layer of the shields of C. kingi and C. elgae consists of two different levels, that is, an upper (Fig. 7A:b1) more compact reticular level, and a lower (b2) cancellous level. In the reticular level there are numerous narrow canals leading to the pulp canals and intercostal grooves. The cancellous level is about twice as thick as the reticular one. The meshwork of canals (chambers) of the cancellous level is more regular than in the reticular level. Some chambers are larger and honeycomb in shape. The aspidin trabeculae between the chambers are relatively thin with a very fine fibrous structure. The spindle-shaped spaces within the aspidin (canaliculi of aspidinoblasts) are thin and rare. The basal layer of the bone is thin and penetrated by rare vertical ascending vascular canals (Fig. 7A:c). Its horizontal lamination is not clearly expressed. Discussion These specimens have head carapaces with a superficial ornamentation which is very similar to that described in corvaspids, that is Corvaspis kingi Woodward 1934 and the various isolated fragments attributed to Corvaspis (e.g., Dineley, 1955; Tarlo, 1965; Dineley and Loeffler, 1976; Loeffler and Dineley, 1976; Blieck, 1982, 1983). This ornamentation

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FIGURE 7. Corveolepis elgae, gen. et sp. nov. Paratype LIG 35-330. Slide VNKT n8 1296. A, vertical section across an isolated tesseriform unit (‘‘tessera’’) of the ventral shield; B, enlarged part of the superficial layer. Key: a, superficial layer; b1, middle layer with a reticular structure; b2, middle layer with a cancellous structure; c, basal layer; arc, arcade canal; pc, pulp canal.

is typically made of close units composed of rather wide longitudinal dentine ridges with a convex top and crenulated lateral margins. However, these units are not separated from the underlying layers of bone (aspidin), but are fused together by its basal lamellar layer. So, they do not correspond to true tesserae (i.e., separated elements of a mosaic), but to superficial units which mimic tesserae, thus they are called tesseriform units here (the ‘‘local groupings of dentine ridges’’ of Loeffler and Dineley, 1976). No convincing isolated tesserae of Corvaspis have ever been described. The general pattern of the dorsal shield of LIG 35-333 and 35-330 is that of a fused shield with enclosed orbits, as already described in Corvaspis arctica Loeffler and Dineley 1976. This pattern seems to be different from that of the type species C. kingi Woodward 1934, whose dorsal head carapace may be composed of separate plates as described by Dineley (1955) and Tarlo (1965). However, as no complete articulated specimen of C. kingi and the other species referred to the genus (viz., C. graticulata Dineley, 1955, C. karatajuteae Tarlo, 1965, Corvaspis sp. indet. Dineley and Loeffler 1976, and various Corvaspis sp. auct.) has ever been collected and described, the pattern of their dorsal and ventral shields are still unknown. All published specimens correspond to incomplete plates or fragments of plates, and their topographic arrangement has probably to be completely re-assessed as hypothesized by R. Thorsteins-

son in the light of still-unpublished, fully-articulated specimens from the Canadian Arctic (pers. comm. to A. B., Calgary, 1987). So, we propose here that the genus name Corvaspis should be kept for its type species C. kingi from England, and that a new genus name should be created for those taxa with a fused dorsal shield, that is, C. arctica Loeffler and Dineley and the new species described here as Corveolepis elgae, gen. et sp. nov. Several elements of comparison are still missing for the latter two, including the ventral shield of C. arctica, the front part of the dorsal shield of C. elgae, the trunk and tail of C. arctica, and the tail of C. elgae. We know neither the general pattern of their sensory line systems nor the location of their paired external branchial opening. We extend these proposals to re-assign the fossil material described as Corvaspis kingi from the Lower Devonian of Spitsbergen by Dineley (1955) and Blieck (1983). This material is made of fragmentary elements variously interpreted as ‘‘almost complete large plates,’’ ‘‘dorsal plates,’’ ‘‘ridge plates,’’ or just as ‘‘fragments of carapace.’’ It shows the same kind of tesseriform units with a sinuous pattern as is seen in Corveolepis elgae, gen. et sp. nov. Another point worth discussing is the structure of the trunk. We could not find any ridge scales on Corveolepis elgae in the middle of the median zone of trunk scales (Fig. 3A, C). This is unique among heterostracans, and it is also notable that no convincing isolated ridge scales of corvaspids seem to have ever been published. Most corvaspid scales have a very flat crown with longitudinal dentine ridges (Fig. 3C) and a very thick protruding base (Dineley, 1955:fig. 10–11; Blieck, 1983: pl. II, 2–5; pl. III, 4–5). A few scales only have been interpreted as possible ridge scales (Dineley, 1955:fig. 14: ‘‘Corvaspis kingi’’ from Fraenkelryggen, Spitsbergen; Gross, 1961:fig. 8A–D; Blieck, 1983:pl. IV, 3: ‘‘Corvaspis sp. indet’’ from the polaris horizon on Fraenkelryggen, Spitsbergen). The latter are not really typical for corvaspids and show similarities with Strosipherus (Pander, 1856:pl. 4, 8; synonym Oniscolepis Pander, 1856:pl. 6, 33–35 [but not Oniscolepis magnus Pander, 1856: pl. 6, 32, a synonym of Tolypelepis undulata after Denison, 1964]; see Obruchev, 1964:55–56; also Gross, 1961:fig. 10, Oniscolepis). However, a revision of this material is beyond the scope of the present paper. The trunk of LIG 35-333 (Fig. 3) is dorso-ventrally flattened. This may be due to a taphonomic feature related to the lack of ridge scales. It is quite different from the general condition in heterostracans in which the trunk is generally laterally flattened, with a dorsal and ventral row of ridge scales. Alternatively the dorsoventral flattening of LIG 35-333 may be due to compaction as the dorsal shield is evidently crushed and flattened. We may even hypothesize that, in the absence of ridge scales, the cross-sectional shape of the trunk was circular, giving it a cigarshaped, fusiform appearance. CORVEOLEPIS? sp. cf. C.? GRATICULATA (Dineley, 1955) (Figs. 8, 9) Corvaspis, Kurik et al., 1982:69. Corvaspis graticulata Dineley, Karataju¯te˙-Talimaa, 1983:23. Corvaspis sp., Karataju¯te˙-Talimaa et al., 1986:256. Corvaspis sp. cf. graticulata, Karataju¯te˙-Talimaa and Blieck, 1999:129, table 20. Corvaspis sp. cf. C. graticulata, Blieck and Karataju¯te˙-Talimaa, in press, fig. 4. Referred Specimens LIG 35-405, 35-954, 35-955, 35-543, and slides n8 1292, 1299, fragments of shields; LIG 35-404, small fragment of an orbital region (doubtfully attributed to Corveolepis? sp. cf. C.? graticulata); from locality 4-11, along the left bank of Matusevich River, central October Revolution Island, Severnaya Zemlya (Fig. 2: n8 1). LIG 35-956, fragment


FIGURE 8.

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Corveolepis? sp. cf. C.? graticulata. Fragments of shields. A, LIG 35-405; B, LIG 35-543 (same scale bar for A, B).

of shield, from locality 40-24, along a right tributary of Spokojnaya River, central October Revolution Island (Fig. 2: n8 3). All from the upper part of the Pod’emnaya Formation, upper Lochkovian, Lower Devonian. Description All of these specimens correspond to fragments of shields. Their size never exceeds 9 cm in length. They are flattened and preserved in a red argillaceous siltstone. They all bear a superficial ornamentation of tesseriform units, most often but not always with intermediate rows of tubercles. On LIG 35-405, the tesseriform units are very regular and hexagonal. Each unit is intercalated between the posterior expansions of two units of the more anterior row and between the anterior expansions of two units of the more posterior row (Fig. 8A). They are about 2.5 mm wide and 4 mm long. Their central part is made of six longitudinal dentine ridges and is surrounded by a double row of short or elongate tubercles. The dentine ridges have a flat surface and are rather wide (4 per mm). On LIG 35543, the tesseriform units are much less regular and smaller than on LIG 35-405 (mostly 1.5–2 mm wide, sometimes 2.5 mm wide; 2.5–3 mm long) (Fig. 8B). On several other specimens (LIG 35-954, 35-956), we find two types of morphological regions: the first where the tesseriform units are separated by rows of tubercles (as on LIG 35-405 and 35-543), the second where the units are closely spaced and without intermediate tubercles. However, on both regions, the dentine ridges are rather flat, and their size is similar to the other specimens (6 per mm on LIG 35-954, 4 per mm on LIG 35-956). Histology The shield of Corveolepis? sp. cf. C.? graticulata is thinner than the shield of C. elgae. The structure of its superficial layer is very similar to that of all other corvaspids (Fig. 9A:a). The middle layer, with an irregular canal meshwork, consists of two different layers as on C. elgae (b1 and b2, Fig. 9A–C); however, the boundary between the layers is not clear. The chambers are larger in the lower layer. The as-

pidin has a globular structure in the whole middle layer. In this respect the inner structure of the shield in C.? sp. cf. C.? graticulata differs from that of Corveolepis elgae and Corvaspis kingi. The cancellous layer of C.? sp. cf. C.? graticulata consists of relatively larger chambers but they are very irregular in outline. Its basal layer is thin and without a clearly expressed lamination (Fig. 9A, C:c). Discussion As already noted, this material is fragmentary, so that we do not know whether it corresponds to fragments of separate plates or fragments of fused shields. So it is unclear if it should be included in the new genus Corveolepis. The superficial ornamentation is quite similar to that of Corvaspis graticulata Dineley which is defined by ‘‘plates somewhat thinner than those of C. kingi’’ and ‘‘ornamentation of poor relief, ribbing divided into polygonal areas by a distinct and persistent chain-like network of fine lines,’’ that is, the rows of intermediate tubercles between the tesseriform units (Dineley, 1955: 179 and pl. II, 3–4). Both features are met with on LIG 35-405 and 35-543. However, several specimens from the same bed as LIG 35-405 and 35-543 show individual variations in which intermediate rows of tubercles are present or absent. We do not know if this corresponds to a simple intraspecific variability or to a specific difference, thus our doubt as to the determination of our new material. It seems probable that it is due to intraspecific variability because it is also encountered on Corveolepis elgae, gen. et sp. nov. (Fig. 3B). On C. elgae, most tesseriform units have no intermediate tubercles although on C. graticulata Dineley most tesseriform units do have intermediate tubercles. Corveolepis? graticulata (Dineley) is geographically restricted to Spitsbergen. So it is paleogeographically endemic to the Arctic province of the Old Red Sandstone Continent (Innuitian Province sensu Dineley, 1973:fig. 12; also Blieck, 1984:fig. 80) as are Corveolepis arctica (Loeffler and Dineley) from the Ca-

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FIGURE 9. Corveolepis? sp. cf. C.? graticulata. Fragments of ventral? discs. A, slide VNKT n8 1292, vertical section across the bone; B, enlarged part of the superficial layer of A; C, slide VNKT n8 1299, vertical longitudinal section across the bone. Key: a, superficial layer; b1, upper, more compact level of the middle layer; b2, lower level of the middle layer, with large irregular chambers; c, basal layer; pc, pulp canal.

nadian Arctic, Corveolepis elgae, gen. et sp. nov. from Severnaya Zemlya, and ‘‘Corvaspis kingi’’ auct. from Spitsbergen. This is another reason why we provisionally refer C. graticulata Dineley to Corveolepis.

ditional data on the intraspecific variability of Corveolepis elgae, and in absence of data on the squamation of Corveolepis? graticulata (Dineley), we are unable to attribute this dissociated material to either species.

CORVASPIDIDAE, gen. et sp. indet.

CONCLUSION

Corvaspis sp., Karataju¯te˙-Talimaa and Blieck, 1999:table 20. Corvaspis sp. and Corvaspis? sp., Blieck and Karataju¯te˙-Talimaa, in press:fig. 4. Comments Numerous other Lower Devonian localities on Severnaya Zemlya have yielded isolated elements (Fig. 2). These are represented by single scales or small fragments of shields; no roof-shaped ridge scales have been observed. All scales are flat-topped with a thick protruding base. Without ad-

Based on new, partly-articulated material from the Lochkovian, Severnaya Zemlya and Pod’emnaya formations of the Severnaya Zemlya archipelago, we propose a new classification of Corvaspididae: Family CORVASPIDIDAE Dineley, 1955 Type genus CORVASPIS Woodward, 1934 Type species Corvaspis kingi Woodward, 1934

¯ TE˙ -TALIMAA—LOWER DEVONIAN CORVASPIDS BLIECK AND KARATAJU Possible other species: Corvaspis karatajuteae Tarlo, 1965 Genus CORVEOLEPIS, gen. nov. (non Corveolepis Halstead, 1993) Type species Corveolepis arctica (Loeffler and Dineley, 1976) Other species: C. elgae, gen. et sp. nov. Possible other species: C.? graticulata (Dineley, 1955); and ‘‘Corvaspis kingi’’ auct. from Spitsbergen. In Severnaya Zemlya, Corveolepis elgae, gen. et sp. nov. is restricted to the uppermost part of the Severnaya Zemlya Formation (lower Lochkovian), and C.? sp. cf. C.? graticulata to the upper part of the Pod’emnaya Formation (upper Lochkovian). In Spitsbergen, ‘‘Corvaspis kingi’’ is restricted to the Fraenkelryggen Formation (lower Lochkovian: Blieck, 1983: fig. 4; Blieck et al., 1987:fig. 9), and C. graticulata (here renamed Corveolepis? graticulata) to the upper part of the Ben Nevis Formation (upper Lochkovian, Blieck et al., 1987). The similar superposition of these taxa thus strengthens the biostratigraphical correlation between Severnaya Zemlya and Spitsbergen (Blieck and Karataju¯te˙-Talimaa, in press:fig. 5). ACKNOWLEDGMENTS V. Karataju¯te˙-Talimaa thanks Drs. R. G. Matukhin (Novosibirsk, Russia) and V. V. Menner (Moscow, Russia) for organization of field work in Severnaya Zemlya in 1978, and J. J. Valiukevicˇius (Vilnius) for companionship in the field. Financial support from IGCP project 406 (Drs. M. V. H. Wilson and T. Ma¨rss co-leaders), the French IGCP National Committee, and the Cultural Center of the French Embassy in Vilnius allowed A. Blieck to go to Vilnius to study the material in July 1997, October 1999, and October 2000. Mr. P. Donabedian of the French Cultural Center is particularly acknowledged for his help. We warmly thank Dr. E. Mark-Kurik (Tallinn, Estonia) for collection and donation of material to the Lithuanian Institute of Geology. The photographic illustrations are the work of Mr. B. S. Pogrebov, St. Petersburg University, Russia. Pr. D. K. Elliott (N.A.U., Flagstaff) and an anonymous referee are thanked for their fruitful reviews of the original manuscript. This is a contribution to IGCP project n8 406, Circum-Arctic Lower-Middle Palaeozoic Vertebrate Palaeontology and Biostratigraphy. LITERATURE CITED Blieck, A. 1982. Les He´te´rostrace´s (Verte´bre´s Agnathes) de l’horizon Vogti (Groupe de Red Bay, De´vonien infe´rieur du Spitsberg). Cahiers de Paleóntologie, Editions du CNRS, Paris, 51 pp. [French with English abstract] ——— 1983. Biostratigraphie du De´vonien infe´rieur du Spitsberg: donneés comple´mentaires sur les He´te´rostrace´s (Verte´bre´s, Agnathes) du Groupe de Red Bay. Bulletin du Museúm National d’Histoire Naturelle, 4e se´rie, 5, C(1):75–111. [French with English abstract] ——— 1984. Les He´te´rostrace´s Pte´raspidiformes, Agnathes du Silurien-De´vonien du Continent nord-atlantique et des blocs avoisinants: re´vision syste´matique, phylogeńie, biostratigraphie, biogeógraphie. Cahiers de Paleóntologie (Verte´bre´s), Editions du CNRS, Paris, 199 pp. [French with English abstract] ———, D. Goujet, and P. Janvier. 1987. The vertebrate stratigraphy of the Lower Devonian (Red Bay Group and Wood Bay Formation) of Spitsbergen. Modern Geology 11(3):197–217. ———, and V. N. Karataju¯te˙-Talimaa. In press. Upper Silurian and Devonian heterostracan pteraspidomorphs (Vertebrata) from Severnaya Zemlya (Russia): a preliminary report with biogeographical and biostratigraphical implications; in D. Goujet (ed.), Palaeontology and Stratigraphy of the Silurian–Devonian of Severnaya Zemlya, Russia (IGCP 406 volume). Geodiversitas. Bystrov, A. P. 1955. Mikrostructura pantsyria bestcheliustnykh pozvonotchnykh silura i devona [Microstructure of the carapace of jawless

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vertebrates of the Silurian and Devonian]; pp. 472–523 in Sbornik rabot ‘‘Pamiati L. S. Berga’’ [L. S. Berg Memorial Volume]. Izvestia Akademia Nauk SSSR 1955. [Russian] Denison, R. H. 1964. The Cyathaspididae, a family of Silurian and Devonian jawless vertebrates. Fieldiana: Geology 13(5):311–473. Dineley, D. L. 1955. Notes on the genus Corvaspis. Proceedings of the Royal Society of Edinburgh, section B, 65(2) [1953–1954]:166– 181. ——— 1973. The fortunes of the early vertebrates. Geology 5:2–20. ———, and E. J. Loeffler. 1976. Ostracoderm faunas of the Delorme and associated Siluro-Devonian formations, North West Territories, Canada. Special Papers in Palaeontology 18:1–214. Gross, W. 1961. Aufbau des Panzers obersilurischer Heterostraci und Osteostraci Norddeutschlands (Geschiebe) und Oesels. Acta Zoologica 42:73–150. [German] Halstead, L. B. 1993. Agnatha; pp. 573–581 in M. J. Benton (ed.), The Fossil Record 2. Chapman and Hall, London. ICZN (International Commission on Zoological Nomenclature). 1999. International Code of Zoological Nomenclature. Fourth edition. The International Trust for Zoological Nomenclature/The Natural History Museum, London, 306 pp. [English and French] Karataju¯te˙-Talimaa, V. N. 1983. Geterostraki nizhnego devona Severnoj Zemli i ikh korreliatsionnoje znatchenie [Lower Devonian heterostracans of Severnaya Zemlya and their importance for correlations]; pp. 22–28 in L. I. Novitskaya (ed.), Problemy sovremennoj paleoichtiologii [Recent problems of paleoichthyology]. Nauka, Moskva. [Russian] ———, and A. Blieck. 1999. Geterostraki [Heterostraci]; pp. 127–131 in R. G. Matukhin and V. V. Menner (eds.), Stratigrafiya silura i devona arkhipelaga Severnaya Zemlya [Stratigraphy of the Silurian and Devonian of the Severnaya Zemlya archipelago]. Ministerstvo prirodnykh resursov Rossijskoi Federatsii, Rossijskaya Akademiya Nauk (SNIIGGiMS), Novosibirsk. [Russian] ———, E. J. Mark-Kurik, V. M. Kurshs, R. G. Matukhin, and V. V. Menner. 1986. Facial’naja priurochennost’ i tipy zachoronenija pozvonochnych v verchnem silure i nizhnem devone Severnoj Zemli [Facies relations and embedding types of vertebrates in the Upper Silurian and Lower Devonian of Severnaya Zemlya]; pp. 251–258 in D. L. Kaljo and E. R. Klaamann (eds.), Teorija i opyt ekostratigrafii [Theory and practice of ecostratigraphy]. Valgus, Tallinn. [Russian] Khapilin, A. F. 1982. Stratigraphiya devonskikh otlozhenij Severnoj Zemli [Stratigraphy of Devonian deposits of Severnaya Zemlya]; pp. 103–119 in V. J. Kaban’kov and N. P. Lazarenko (eds.), Geologiya arkhipelaga Severnaya Zemlya [Geology of Severnaya Zemlya archipelago]. PGO ‘‘Sevmorgeologiya’’ Ministerstva Geologii SSSR, Leningrad. [Russian] Kurik, E., V. M. Kurshs, V. A. Markovskij, R. G. Matukhin, V. V. Menner, T. L. Modzalevskaya, D. K. Patrunov, Y. G. Samoilovich, M. A. Smirnova, V. N. Talimaa, A. F. Khapilin, S. V. Cherkesova, and A. F. Abushik. 1982. K stratigrafii silura i devona Severnoj Zemli [On the Silurian and Devonian stratigraphy of Severnaya Zemlya]; pp. 65–73 in Stratigrafiya i paleontologiya devona i karbona [Devonian and Carboniferous stratigraphy and paleontology]. Nauka, Novosibirsk. [Russian] Loeffler, E. J., and D. L. Dineley. 1976. A new species of Corvaspis (Agnatha, Heterostraci) from the upper Silurian to lower or middle Devonian of the North-west Territories, Canada. Palaeontology 19(4):757–766. Ma¨nnik, P., V. V. Menner, R. G. Matukhin, and V. Kurshs. In press. Silurian and Devonian strata on Severnaya Zemlya; in D. Goujet (ed.), Palaeontology and stratigraphy of the Silurian-Devonian of Severnaya Zemlya, Russia (IGCP 406 volume). Geodiversitas. Matukhin, R. G., and V. V. Menner (eds.). 1999. Stratigrafiya silura i devona arkhipelaga Severnaya Zemlya [Stratigraphy of the Silurian and Devonian of the Severnaya Zemlya archipelago]. Ministerstvo prirodnykh resursov Rossijskoi Federatsii, Rossijskaya Akademiya Nauk (SNIIGGiMS), Novosibirsk, 174 pp. [Russian] Obruchev, D. V. 1964. Bescheliustnye, Ryby [Agnathans, Fishes]. Nauka, Moskva, 522 pp. [Russian; English translation, 1967, Israel Program for Scientific Translation, Jerusalem] Pander, C. H. 1856. Monographie der fossilen Fische des silurischen Systems der russisch-baltischen Gouvernements. Buchdruckerei der kaiserlichen Akademie der Wissenschaften, St. Petersburg, 91 pp. [German]

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Tarlo, L. B. Halstead. 1960. The Downtonian Ostracoderm Corvaspis kingi Woodward, with notes on the development of dermal plates in the Heterostraci. Palaeontology 3(2):217–226. ——— 1964. Psammosteiformes (Agnatha)—A review with descriptions of new material from the Lower Devonian of Poland. I. General part. Palaeontologia Polonica 13:1–135. ——— 1965. Psammosteiformes (Agnatha)—A review with descriptions of new material from the Lower Devonian of Poland. II. Systematic part. Palaeontologia Polonica 15:1–168. Woodward, A. S. 1934. Note on a new Cyathaspidian fish from the Upper Downtonian of Corvedale. Quarterly Journal of the Geological Society of London 90:566–567. Received 18 January 2001; accepted 3 August 2001.

APPENDIX 1 Localities and faunal lists from the Severnaya Zemlya and Pod’emnaya formations. Most localities are described in Matukhin and Menner (1999:37–46 and fig. 8) (see Fig. 2). Severnaya Zemlya Formation 1. Along the left bank of the Matusevich River. Locality 1-21: Corveolepis elgae, gen. et sp. nov. (specimens LIG 35-432, 35-417), Corvaspididae gen. et sp. indet., Tesseraspis mosaica, Tesseraspis sp. 2. Along the left bank of the Ushakov River, east of the Vavilov Glacier. Locality 21-9: Corvaspididae gen. et sp. indet., Tesseraspis sp. 3. Along the left bank of the Spokojnaya River, towards Krasnaya Bay. Locality 41-12: Corvaspididae gen. et sp. indet. (specimens LIG 35950 to 35-953), Tesseraspis sp. (this section is not described in Matukhin and Menner, 1999). 4. Along a left tributary of the Pod’emnaya River, NW of the Vavilov Glacier. Locality 67-12: Corveolepis elgae, gen. et sp. nov. (specimens LIG 35-330, 35-431, 35-544 and slide n8 1296), Corvaspididae gen. et sp. indet., Tesseraspis sp. 5. Along a small stream NE of Sovetskaya Bay, near to the Al’banov Glacier. Locality 28-1: Corveolepis elgae, gen. et sp. nov. (specimen LIG 35-333, holotype) (this section is not described in Matukhin and Menner, 1999). Other taxa collected in this part of the Severnaya Zemlya Formation

are Osteostraci, Anaspida, Acanthodii, ?Elasmobranchii, arthropods (chelloniellids, chasmataspids, phyllocarids, ostracodes, and rhinocarid crustaceans), and charophytes. Pod’emnaya Formation 1. Along the left bank of the Matusevich River. Locality 4-3: Corvaspididae gen. et sp. indet., Phialaspis sp., Ctenaspis, sp. nov., Protopteraspis sp., Irregulareaspis sp., Poraspididae, Pteraspididae. Locality 4-11: Corveolepis? sp. cf. C.? graticulata (specimens LIG 35404, 35-405, 35-543, 35-954, and slides n8 1292, 1299), Corvaspididae gen. et sp. indet., Phialaspis sp., Ctenaspis, sp. nov., Irregulareaspis sp., Homalaspidella sp., Poraspis sp. cf. P. polaris, Traquairaspidiformes, Unarkaspis? sp., Protopteraspis? sp., Pteraspidiformes. 2. Along the left bank of the Ushakov River, east of the Vavilov Glacier. Locality 23-2: Corvaspididae gen. et sp. indet., Phialaspis sp., Poraspididae. Locality 23-15, 16: Corvaspididae gen. et sp. indet., Phialaspis sp., Poraspis sp., Irregulareaspis sp., Putoranaspis? sp., Amphiaspidiformes. Localities 23-20, 22, 23, 25: Corvaspididae gen. et sp. indet., Ctenaspis sp. nov., Poraspis sp., Irregulareaspis sp., Poraspididae, Pteraspidiformes. 3. Along a right tributary of the Spokojnaya River, NW of Krasnaya Bay. Localities 40-13, 15, 17: Corvaspididae gen. et sp. indet., Poraspis sp., Poraspididae. Localities 40-20 to 27: Corveolepis? sp. cf. C.? graticulata (only at 40-24; specimen LIG 35-956), Corvaspididae gen. et sp. indet., Phialaspis sp., Poraspis? sp., Irregulareaspis? sp., Poraspididae. 4. Along a right tributary of the Pod’emnaya River. Localities 69-4, 5, 8: Corvaspididae gen. et sp. indet., Anglaspis, sp. nov., Phialaspis? sp., Poraspididae. Localities 69-17, 24: Corvaspididae gen. et sp. indet., Phialaspis sp., Poraspis sp. cf. P. polaris, Poraspis sp., Irregulareaspis? sp., Pteraspidiformes. Localities 69-28, 31: Corvaspididae gen. et sp. indet., Traquairaspidiformes, Poraspididae, Pteraspidiformes. Localities 60-3, 4, 10, 12 (not described in Matukhin and Menner, 1999, but equivalent to the upper part of section 69): Corvaspididae gen. et sp. indet., Phialaspis sp., Poraspis sp., Irregulareaspis? sp., Pteraspidiformes. Other taxa sampled in the Pod’emnaya Formation include Thelodonti, Osteostraci, Acanthodii, Tylodus, pelecypods, lingulids, ostracodes, and Trochiliscus.