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From Severnaya Zemlya (Russia) Silurian and Lower Devonian anaspids (Agnatha) from Severnaya Zemlya (Russia) Tiiu MÄRSS Institute of Geology, Tallinn Technical University, 7 Estonia Avenue, 10143 Tallinn (Estonia) [email protected] Märss T. 2002. — Silurian and Lower Devonian anaspids (Agnatha) from Severnaya Zemlya 406 (Russia). Geodiversitas 24 (1) : 123-137. ABSTRACT In the Severnaya Zemlya Archipelago, Silurian anaspids are represented by scales of at least six different types of sculpture, and some subtypes, called Birkeniida sp. C, Birkeniida sp. C1, Birkeniida sp. C?, Birkeniida sp. D, KEY WORDS Agnatha, Birkeniida sp. F, Birkeniida sp. F?, Birkeniida sp. G., Birkeniida sp. H and Anaspida, Birkeniida sp. J. In addition, Birkenia? sp. was recognized. A new taxon was Silurian, Lower Devonian, erected on the basis of the material from the Severnaya Zemlya Formation, Severnaya Zemlya Archipelago, Lower Devonian. In the specimen, the trunk squamation is rather well pre- Russia, served, but the head and the caudal fin are lacking. Characteristic are very scale sculpture, new genus, big dorsal ridge scales. The stratigraphical range of anaspids on Severnaya new species. Zemlya is from Wenlock to Lochkov. RÉSUMÉ Anaspides (Agnatha) du Silurien et du Dévonien inférieur de Severnaya Zemlya (Russie). Dans l’archipel de Severnaya Zemlya, les anaspides siluriens sont représentés par des écailles appartenant à au moins six types (avec quelques sous-types) d’ornementation différents nommés Birkeniida sp. C, Birkeniida sp. C1, Birkeniida sp. C ?, Birkeniida sp. D, Birkeniida sp. F, Birkeniida sp. F ?, MOTS CLÉS Agnatha, Birkeniida sp. G., Birkeniida sp. H et Birkeniida sp. J. De plus, Birkenia ? sp. Anaspida, a été identifié. Un nouveau taxon a été créé à partir du matériel de la Silurien, Dévonien inférieur, Formation Severnaya Zemlya, Dévonien inférieur. Sur le spécimen, l’écaillu- archipel de Severnaya Zemlya, re du tronc est assez bien conservée mais la tête et la nageoire caudale lui font Russie, défaut. De fortes écailles faîtières dorsales sont caractéristiques de ce taxon. ornementation d’écailles, nouveau genre, Stratigraphiquement, les anaspides de Severnaya Zemlya ont une extension nouvelle espèce. verticale du Wenlock au Lochkovien. GEODIVERSITAS • 2002 • 24 (1) © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris. www.mnhn.fr/publication/ 123 Märss T. INTRODUCTION be clearly identified as anaspid ones under the names Coccopeltus asmusi Pander, 1856 (taf. 5, Samples with vertebrate remains were collected fig. 1), Rytidolepis queenstedtii Pander, 1856 during the expeditions to Severnaya Zemlya by (taf. 5, fig. 2) and Schidiosteus mustelensis A. F. Khapilin and E. N. Lenkin in 1974, B. A. Pander, 1856 (taf. 5, fig. 13). Later, Rohon (1893: Klubov and E. I. Kachanov in 1976, V. V. 11-13) believed they represent invertebrate Menner and V. N. Talimaa in 1978, and groups like worms or crustaceans, and he did P. Männik and E. Kurik in 1978. The samples not include above-cited species in his work as were dissolved by V. N. Talimaa, Vilnius, and vertebrates. Later on, Pander’s taxa have not P. Männik, Tallinn, and the scales as well as the been used by subsequent authors. well-preserved anaspid specimen were given to The sculpture, its variability and microstructure the author for description. Anaspids are rather of scales of completely preserved Norwegian rare in the Silurian and Lower Devonian of the anaspids should be described, since no Silurian Severnaya Zemlya Archipelago. Their scale frag- (Wenlock, Ludlow) taxon can be erected on the ments have been found in the Samojlovich, Ust’ species, genus, or even the family level without Spokojnaya and Krasnaya Bukhta formations, knowing these characteristics. Only after that Silurian; in the Matusevich, Ushakov and can the comparison and identification of frag- Spokojnaya river sections of October Revo- mentary material, collected during more than lution Island, and in the coeval strata of half a century from different parts of the north- Komsomolets and Pioneer islands where forma- ern hemisphere (Severnaya Zemlya, Canadian tions are not yet established. Arctic, Britain, Baltic), be realized. For such Data on the geology of the region, as well as de- research the articulated exoskeleton of a specimen tailed descriptions of the sections, can be found in must be dissolved to reveal the sculpture which Klubov et al. (1980), and in Matukhin & Menner nearly always remains in the rock, and latex-casts (1999). Thus, they are not repeated here. made from the sculpture moulds. The sculpture The taxonomy of anaspids is based on charac- of fragmentary material can be compared with teristics of the overall body form, head and mid- that of latex-casts, and proper generic and species dorsal ridge scales, number of branchial names given. Until then, following Märss (1986) openings, and lateral and anal fins of articulated and Fredholm (1988, 1990), it seems reasonable specimens, mainly from Scotland and Norway. to establish on Severnaya Zemlya new forms They have been studied for over a century by in open nomenclature: Birkeniida sp. C1, Traquair (1898, 1899, 1905), Kiaer (1911, 1924), Birkeniida sp. F, Birkeniida sp. G, Birkeniida sp. Stetson (1928), Berg (1940, 1955), Smith (1956, H, and Birkeniida sp. J. Three forms, Birkeniida 1957), Stensiö (1958, 1964), Obruchev (1964), sp. C, Birkeniida sp. C? and Birkeniida sp. D, are Ritchie (1964, 1980), and others. Besides articu- known from two regions – Severnaya Zemlya lated specimens, the fragments of Silurian and the Baltic (see Märss 1986). Birkeniida sp. A, anaspid scales have gained some attention. Their Birkeniida sp. B and Birkeniida sp. E, described sculpture and/or microstructure, the only fea- from the Baltic (Märss 1986), were not found tures preserved in the material from the acetic on Severnaya Zemlya. Birkenia? sp. and acid preparation residues, have been described Vilkitskilepis valentinae n. gen., n. sp. are identi- from Baltic bedrock and boulders of the North fied and described in the present paper. German Lowland (Gross 1938, 1958, 1968; Märss 1986; Fredholm 1988, 1990). Only one taxon, Saarolepis oeselensis (Robertson, 1941), BIOSTRATIGRAPHICAL REMARKS has been identified by Gross (1958). Still, Pander (1856), writing a pioneer work, About 20 samples from the upper Wenlock to described the fragments of vertebrates that can Přidoli interval contained fragments of anaspid 124 GEODIVERSITAS • 2002 • 24 (1) Silurian and Devonian anaspids from Severnaya Zemlya ? sp. SERIES SAMPLES Birkenia n. gen., sp. FORMATION Birkeniida sp. J Birkeniida sp. F Birkeniida sp. D Birkeniida sp. C Birkeniida sp. H Birkeniida sp. G Birkeniida sp. F? Birkeniida sp. C1 Birkeniida sp. C? Vikitskilepis valentinae Vikitskilepis Severnaya Zemlya 67-12 + . Krasnaya ř P Bukhta MF 157-2 + MF 157-3 2055zh u. + Ust’ 2-3 2803; 20568 + m. 2-12; 2-14 + Spokojnaya 30; 30-1; 47-14 + + + + ++ l. 2-21; MF 157-4 5m + + + + + + SILURIAN DEV. SYSTEM 31-208 8g-1; 8g + + + + Samojlovich MF 46-23 5d +++ + LI. W. Ludlow Loch. FIG. 1. — Distribution of the anaspids in the sections of the Severnaya Zemlya Archipelago. Sample numbers from October Revolution Island on the left side, sample numbers from Pioneer and Komsomolets islands on the right. Abbreviations: Dev., Devonian; Ll., Llandovery; Loch., Lochkov; Př., Přidoli; W., Wenlock. scales, and a limestone nodule from the lower part of the Ust’ Spokojnaya Formation, upper Lochkov, Lower Devonian, yielded a trunk Ludlow (samples 2-3 and MF 157-3 on October squamation. Three main anaspid assemblages Revolution Island, 2055 zh and 2803 on Pioneer can be recognized in the Silurian sequence Island, and 20568 on Komsomolets Island) the (Fig. 1). The first assemblage characterizes the third assemblage was identified. It does not Samojlovich Formation, Wenlock, on October contain any forms from the lower assemblages; Revolution Island (samples 31-208 and MF 46- a new form, Birkeniida sp. J, appears and ranges 23) and its equivalents on Pioneer Island (sam- into the lower part of Přidoli (sample MF 157- ples 5d, 8g-1 and 8g). The assemblage comprises 2). In the Severnaya Zemlya Formation, lower Birkenia? sp., Birkeniida sp. C, Birkeniida sp. Lochkov, Lower Devonian, a new anaspid, F, Birkeniida sp. F? and Birkeniida sp. G. The Vilkitskilepis valentinae n. gen., n. sp., occurs second assemblage was established in the lower (sample 67-12). part of the Ust’ Spokojnaya Formation (sam- Birkeniida sp. C, Birkeniida sp. C? and ples 30, 30-1, 47-14, 2-21 and MF 157-4), Birkeniida sp. D from the Samojlovich and Ust’ Ludlow, and coeval strata on Pioneer Island Spokojnaya formations, Wenlock and Ludlow, (sample 5m). On that level the abundance of are identical to the Baltic forms and the beds can scales and the variability of the sculpture are be correlated with the Rootsiküla and Paadla largest. In addition to the Wenlock forms, stages of the East Baltic, and the Halla and Birkeniida sp. C1, Birkeniida sp. C?, Birkeniida Hemse beds of Gotland, Sweden (Märss 1986; sp. D and Birkeniida sp. H appear, but Fredholm 1988, 1990). Anaspid forms from the Birkeniida sp. G disappears. In the middle part Krasnaya Bukhta Formation, Přidoli, and high- of the Ust’ Spokojnaya Formation, middle part er have no similarities with the Baltic ones, and of Ludlow, the diversity of forms decreases no anaspid-based correlation can be made at the markedly (samples 2-12, 2-14). In the upper present stage of study. GEODIVERSITAS • 2002 • 24 (1) 125 Märss T. SYSTEMATICS REMARKS Scales have rounded or just slightly elongated, Scales with collection numbers prefixed by Pi triangular keel-like tubercles (Fig. 2A-C). The are deposited in the palaeontological collection anterior margin of the scales is smooth or cov- of the Institute of Geology, Tallinn Technical ered with low, rounded tubercles. In the basal University; those prefixed by LIG 35 are kept in part of broken tubercles (Fig. 2D), microscopic the Institute of Geology, Vilnius. holes, vascular canals (= Gefässkanal by Gross 1958) can be seen.
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