A New Narrow-Armored Chroniosuchian (Amphibia, Anthracosauromorpha) from the Upper Permian of Eastern Europe V

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Paleontological Journal, Vol. 33, No. 2, 1999, pp. 166Ð173. Translated from Paleontologicheskii Zhurnal, No. 2, 1999, pp. 43Ð50. Original Russian Text Copyright © 1999 by Golubev. English Translation Copyright © 1999 by åÄàä “ç‡ÛÍ‡ /Interperiodica” (Russia).

A New Narrow-Armored Chroniosuchian (Amphibia, Anthracosauromorpha) from the Upper Permian of Eastern Europe V. K. Golubev Paleontological Institute, Russian Academy of Sciences, ul. Profsoyuznaya 123, Moscow, 117647 Russia Received October 2, 1997

Abstract—A new narrow-armored chroniosuchid Suchonica vladimiri is described based on skeletal elements discovered in the lower part of the North-Dvinian Regional Stage of the Upper Tatarian Substage of the Sukhona River. The Late Tatarian faunal vertebrate assemblages are characterized. Assignment of the genus Suchonica to the Kotelnich assemblage is supported here. Correlation of the Tatarian of the Sukhona River and Kotelnich sections is discussed.

INTRODUCTION genera Chroniosuchus, Uralerpeton Golubev and In 1994 V.L. Mashin, a student of the Paleontology Jarilinus by a pectinate type of dermal sculpturing of Department of the Geological faculty of Moscow State the scutes; from the genera Chroniosuchus and Jarili- University, found the remains of a narrow-armored nus by the absence of longitudinal swollen cristae from chroniosuchian, described below as Suchonica the scute dorsal surface; from the genus Uralerpeton in vladimiri gen. et sp. nov., on the left bank of the that the scutes do not fuse to the neural spines. Sukhona River opposite the eastern edge of the village of Poldarsa and 0.5 km upstream from the village of Suchonica vladimiri Golubev, sp. nov. Nikulino (Vologda Region, Velikii Ustyug District; Etymology. In honor of paleoichthyologist Fig. 1). The skeletal fragments were recovered from Vladimir Mashin, who found the specimen. light-green marls from the basal part of the Upper Tatarian Substage (the top of the Nyuksenitsa Member Holotype. PIN, no. 4611/1, the anterior (? cervi- of the Sukhona Formation). The scutes and vertebrae of cal) armor scute; Vologda Region, Velikii Ustyug Dis- the present form are constructed typically for members trict, village of Poldarsa; Upper Permian, Upper Tatar- of the family Chroniosuchidae (Golubev, 1998a), sug- ian Substage, North-Dvinian Regional Stage, the top of gesting its assignment to this taxon. the Nyuksenitsa Member of the Sukhona Formation.

SYSTEMATIC PALEONTOLOGY 40° 45° 50° CLASS AMPHIBIA 65° 1 Order Anthracosauromorpha Arkhangelsk Suborder Chroniosuchia Family Chroniosuchidae Vjuschkov, 1957 Genus Suchonica Golubev, gen. nov. Etymology. From the Sukhona River. Type species: Suchonica vladimiri sp. nov. Diagnosis. Trunk scutes belong to narrow type 2 (scute wings length exceeds their width). Ventral scute 60° process does not fuse to neural spine. Scute dorsal sur- 60° face ornamented by pectinate sculpturing. Longitudinal 1 3 swollen cristae absent from the dorsal scute surface. Kirov Species composition. Type species. Comparison. Differs from the genera Jarilinus Golubev, Chroniosaurus Tverdochlebova and Chronio- Fig. 1. Map of the Late Permian localities of the Kotelnich suchus Vjuschkov by narrow trunk scutes; from the tetrapod assemblage in the territory of European Russia. (1) Ust’-Yelva, (2) Poldarsa, (3) Kotelnich and Port Kotelnich. 1 For dermal ornamentation type terminology see Golubev (1998b). Scale 1 : 10000000.

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A NEW NARROW-ARMORED CHRONIOSUCHIAN 167

‡b 1 Òm

Fig. 2. Suchonica vladimiri sp. nov., scutes of the dorsal armor from above: (a) holotype PIN, no. 4611/1; (b) specimen PIN, 4611/10; (c) specimen PIN, no. 4611/8; (d) specimen PIN, no. 4611/12.

Description (Fig. 2). Medium-sized chronio- Vjuschkov (Golubev, 1998a). The neural arch of the suchid, estimated skull length no more than 25 cm. The vertebra fuses to the centrum without any sutural mark- armor scutes pertain to the narrow type. The armor ing. The neural spine is shaped as a triangle, elongated probably overlapped only the axial part of the dorsal dorsally in lateral view. Its anterior and posterior edges surface of the animal’s body. The dermal scute sculp- bear distinct shallow notches that correspondingly turing belongs to the pectinate type and is formed by housed the anterior and posterior projections of the short, 5Ð9 mm long, vermiform swollen ridges. Up to ventral scute process. The ventral process and the neu- ﬁve variously expressed pustules, sometimes shaped as ral spine did not fuse and probably made contact by the distinct tubercles, may be placed along the swollen connective tissue only. The neural spine structure ridges (pectens). The pectens are aligned predomi- described above and the character of its articulation to nantly transversely. The pectens become even shorter the ventral process is also a distinctive feature of mem- on the scute wings, frequently disintegrating into iso- bers of the family Chroniosuchidae. lated tubercles. In these zones the dermal sculpture may The intercentra, as in the other chroniosuchids, are become pectinate-pustular. A couple of well expressed amphicoelous and rounded in cross section. longitudinal crests thicken the scute, extend along its upper surface along the boundary between the body of Occurrence. Lower part of the North-Dvinian the scute and the wings. The dermal ornament pectens Regional Stage of the Upper Tatarian Substage, of these crests become aligned predominantly longitu- Vologda Region. dinally and frequently form enclosed rings. Remarks. The absence of longitudinal swollen The ventral scute process is not preserved. Taking crests on the scutes and presence of replacement crests into account the imprint at the ventral surface of the that thicken the scutes are shared by Suchonica scute (specimen PIN, no. 4611/1), it was thin and long, vladimiri and the most primitive wide-armored chro- with pointed anterior and posterior edges and had com- niosuchid, Chroniosaurus dongusensis Tverdochle- pletely occupied the median part of the scute. A similar bova. Presence of narrow scute wings suggests that construction of the ventral process is typical of mem- Suchonica is the morphological predecessor of this bers of the family Chroniosuchidae and distinguishes chroniosaur. This conclusion coincides with the data on them from members of the family Bystrowianidae the stratigraphic distribution of these two taxa. The

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168 GOLUBEV

Provincial zones on tetra- Sukhona River Vyatka River, Kotelnich pods

Member Lithology Lithology Color Color; zone Magneto- System Subsystem Stage Substage Zone Section Bed number in meters Thickness Bed number Thickness in meters Regional Stage Subzone Formation

Kalikino 19–22 N2P

15–18 60Maryushkina Mys Byk Kichuga Sluda-C 14 and Mutovino Ï12–9 Ï15–13 22 21

Purtovino Opoki 20 40 Sokolya Gora Mikulino and Agafonovo 15–19

Proelginia permiana R P 6 37–46 2 30 Isady 7 ? Port POLDARSA 33– 36 Kotelnich

UPPER UPPER Ustye

PERMIAN 25– 32 Strel’ny 5

TATARIAN 20 20 Chroniosaurus dongusensis Chroniosaurus levis Strel’na 19–24 3 17, 18 Nikulino NORTH-DVINIAN 12–16 10 Mikulino 8–11 Kotelnich vjatkensis 4–7 1 Sukhona Deltavjatia Nyuksenitsa Poldarsa 1–3 0 0

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Fig. 3. Correlation of the Upper Tatarian deposits of the Sukhona River area (from the village of Poldarsa to the mouth of the Nizh- nyaya Yerga River) and the Vyatka River (Kotelnich). Designations: (1) limestones, (2) marls, (3) clays, (4) aleurolites, (5) sandstones, (6) redbeds, (7) graywacks, (8) redbeds and graywacks intercalation, (9) direct polarity magnetozone, (10) reverse polarity magnetozone, (11) tetrapod localities. bones of Suchonica vladimiri from the Sukhona River the Kotelnich, the Sokolki (including the Il’inskoye and originate from the top of the Nyuksenitsa Member of the Sokolki subassemblages) and the Vyazniki (Ivach- the Sukhona Formation (Fig. 3), and Chroniosaurus nenko, 1990, 1992; Golubev, 1996, 1998b). remains occur here in the section for the ﬁrst time 18 m The most primitive members of all the main groups above it, in the upper part of the Strel’na Member of the of the theriodont fauna are known from the Kotelnich Poldarsa Formation (Ust’ye Strel’ny locality). How- assemblage (the Deltavjatia vjatkensis fauna). This ever, Suchonica is characterized by a more progressive suggests, that the Kotelnich fauna is the earliest among pectinate dermal ornament of the armor scutes. This all theriodont faunas. The Kotelnich assemblage is well makes it impossible to consider this form as a direct known mainly from a single base (type), the Kotelnich ancestor of Chroniosaurus dongusensis, which con- locality situated on the right bank of the Vyatka River trasts with it in the primitive pustular sculpture. downstream from the town of Kotelnich (Kirov Material. Apart from the holotype from the type Region). Rich material became available from this site locality, specimens PIN nos. 4611/2Ð5, vertebrae; during the past several years as a result of annual exca- 4611/6, intercentrum; 4611/7, sacral rib; 4611/8Ð14, vations previously conducted by D.L. Sumin and pres- scutes and scute fragments. ently by A.Yu. Khlyupin. The dominant part of the Kotelnich assemblage of DISCUSSION terrestrial vertebrates (Fig. 4) is composed of relatively small and primitive herbivorous bradysaurid pareia- Chroniosuchids are characteristic of the aquatic saurs Deltavjatia vjatkensis (HartmannÐWeinberg) and branch of the theriodont superassemblage (Late Tatar- the dicynodonts Tropidostoma sp. The predators ian) of the Permian terrestrial vertebrates in Eastern include the therocephalians (the moschowhaitsiid Viat- Europe. Three faunal assemblages are currently known kosuchus sumini Tatarinov) and medium sized gor- within the structure of this superassemblage (Fig. 4): gonopids. The characteristic members of the subdomi-

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A NEW NARROW-ARMORED CHRONIOSUCHIAN 169

Superassemblage Theriodont Assemblage Kotel- Sokolki Vyaz- nich- Il’in- Subassemblage skoye Sokolki niki Microsauria f.i. Dvinosauridae Chroniosuchidae Bystrowianidae Nycteroleteridae Leptorophidae Kaspinskiosauridae Rhipeosauridae Elginiidae Bradysauridae Pareiasauridae Procolophonidae Burnetiidae Galeopidae Dicynodontidae Gorgonopidae Ictidosuchidae Inostranceviidae Whaitsiidae Moschowhaitsiidae Scylacosauridae Annatherapsididae Theromorpha Parareptilia Amphibia Nanictidopidae Cynodontia f.i. Dviniidae Galesauridae Procynosuchidae Diap- Protorosauridae sida Proterosuchidae ‡ c b d

Fig. 4. Terrestrial tetrapod families occurring within the Late Tatarian faunal assemblages of Eastern Europe: (a) abundant, (b) fre- quent, (c) rare, (d) unique. nant block are numerous small-sized therocephalians tory of the Permian assemblages of terrestrial verte- (the ictidosuchids, Karenites ornamentatus Tatarinov brates in Eastern Europe (Golubev, 1995). and Perplexisaurus foveatus Tatarinov), the galeopids The Kotelnich assemblage of terrestrial vertebrates Suminia getmanovi Ivachnenko and the relic nycterole- is replaced by the Sokolki assemblage (Fig. 4). The lat- terids Emeroleter levis Ivachnenko. The remains of the ter is the best known among all theriodont assemblages. aquatic tetrapods were not found in Kotelnich. Proba- It is currently known from more than 50 localities. bly, as in the other theriodont assemblages, the aquatic block of the Kotelnich fauna was formed by the chro- The early Sokolki fauna is speciﬁed as the niosuchids, primitive leptorophid parareptiles and the Il’inskoye subassemblage (Proelginia permiana colosteiform labyrinthodonts, dvinosaurids. fauna). The base locality is Syomin Ovrag (village of Il’inskoye, Tatarstan). The dominant block of the The Kotelnich assemblage is preceded by the Il’inskoye community (Fig. 4) is formed of the herbiv- Isheyevo dinocephalian assemblage (Ivachnenko, orous pareiasaurids, Proelginia permiana (HartmannÐ 1990, 1992, 1995, 1996). However, these faunas do not Weinberg), probably the descendants of the Kotelnich share a single common family. Such a sharp faunal con- bradysaurids, and the dicynodonts, Oudenodon sp. The trast probably resulted from the alteration of the predators are exempliﬁed by abundant gorgonopids Isheyevo assemblage by the Kotelnich during the local Sauroctonus progressus (HartmannÐWeinberg) and ecological crisis that was one of the largest in the his- burnetiids (Proburnetia vjatkensis Tatarinov and Niuk-

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170 GOLUBEV senitia sukhonensis Tatarinov). The subdominant block chroniosuchians Bystrowiana permira Vjuschkov, includes a variety of forms: the galeopsids Suminia cf. mainly characteristic of the Triassic, appear in the sub- S. getmanovi characteristic only of the early Il’inskoye dominant block. Microsaurs become abundant. The fauna (Chroniosaurus dongusensis fauna), as well as relic subdominants Nycteroleterinae Elginia sp., are much less abundant procolophonids Microphon exig- more rare. The significant changes which occur in the uus Ivachnenko, the therocephalians (scylacosaurids dominant and subdominant blocks do not touch the Scylacosuchus orenburgensis Tatarinov), protorosaurid aquatic block. The narrow-armored chroniosuchids diapsids (the protorosaurid Eorasaurus olsoni Senni- Uralerpeton tverdochlebovae Golubev, the leptor- kov) and problematic cynodonts. The aquatic block ophids, the karpinskiosaurids Kotlassia grandis Tver- includes the wide-armored chroniosuchids Chronio- dochlebova et Ivachnenko and the dvinosaurids Dvino- saurus dongusensis and C. levis Golubev; primitive saurus egregius Shishkin and D. purlensis Shishkin, parareptiles (the leptorophids Raphanodon tverdochle- still dominate here. bovae Ivachnenko) and the colosteiform labyrinth- The faunal assemblages discussed above character- odonts (the dvinosaurid, Dvinosaurus primus Amal- ize certain evolutionary stages of the terrestrial tetrapod itzky). community of the Late Permian of Eastern Europe. The Late Sokolki fauna is specified as the Sokolki They replaced each other during the Late Tatarian in the subassemblage (Scutosaurus karpinskii fauna). The same sequence that was described above: the Kotelnich base locality of this subassemblage is the Sokolki site assemblage—the Il’inskoye subassemblage—the well known from the V.P. Amalitsky excavations at the Sokolki subassemblage—the Vyazniki assemblage. Malaya Severnaya Dvina River (Arkhangelsk Region). This assumption is based upon the evolutionary levels The dominant block of the Sokolki subassemblage of the faunas considered and is also supported by strati- (Fig. 4) includes the large phytophagous pareiasaurs graphic data. Thus, the layers around the town of Scutosaurus karpinskii (Amalitzky), S. tuberculatus Kotelnich containing the tetrapod remains of the (Amalitzky) and S. itilensis Ivachnenko et Lebedev, the Kotelnich assemblage (Kotelnich locality), are situated dicynodonts Dicynodon trautscholdi Amalitzky and the about 30Ð35 m below the beds containing the predators: the inostranceviid gorgonopians Inostrance- Il’inskoye fauna (Proelginia cf. P. permiana, Chronio- via alexandri Amalitzky, I. latifrons Pravoslavlev, saurus levis, Dvinosaurus primus, and Proburnetia I. uralensis Tatarinov and Pravoslavlevia parva (Pra- viatkensis in the Agafonovo and Sokolya Gora locali- voslavlev); the annatherapsidids Annatherapsidus petri ties). The localities of the Il’inskoye subassemblage in (Amalitzky) and Chthonosaurus velocidens Vjuschkov. the basin of the Sukhona River, the Malaya Severnaya Diverse cynodonts (the dviniid Dvinia prima Amal- Dvina River and the Severnaya Dvina River are itzky, the galesaurid Nanocynodon seductus Tatarinov restricted to the Poldarsa Formation and those of the and the procynosuchid Uralocynodon tverdokhlebovae Sokolki subassemblage to the above Salaryovo Forma- Tatarinov), rare procolophons (Suchonosaurus mini- tion (Golubev, 1998b), and the Vyazniki assemblage to mus Tverdochlebova et Ivachnenko) and problematic the uppermost part of the Salaryovo Formation, which rhipaeosaurids are characteristic of the subdominant underlies the Triassic (Rasha locality). All known sites block. The aquatic block, as well as the Il’inskoye of the Vyazniki fauna are situated on the boundary of fauna, includes the wide-armored chroniosuchids, the Vyatkian Regional Stage (Upper Permian) and Jarilinus mirabilis (Vjuschkov), Chroniosuchus para- Vokhmian Regional Stage (Lower Triassic) (Golubev, doxus Vjuschkov and C. licharevi (Riabinin), primitive 1998a). parareptiles (the leptorophids Raphanodon cf. R. tverdochlebovae and R. ultimus (Tchudinov et Vjuschkov), The Late Tatarian faunal assemblages of the terres- the karpinskiosaurids Karpinskiosaurus secundus trial tetrapos described may be successfully used for (Amalitzky) and Kotlassia prima Amalitzky, and the stratigraphic purposes. Four complex provincial bios- colosteiform labyrinthodonts (the dvinosaurid Dvino- tratigraphical zones are currently recognized at their saurus primus). base in the composition of the Upper Tatarian Substage (Golubev, 1998b, Table 1): the Deltavjatia vjatkensis The Vyazniki assemblage, or the Archosaurus rossi- Zone (the lower part of the North-Dvinian Regional cus fauna (base locality Vyazniki-2, Vladimir Region), Stage), the Proelginia permiana Zone (the upper part of typifies the closing stage of the evolution of the theri- the North-Dvinian Regional Stage), the Scutosaurus odont assemblage of the terrestrial tetrapods (Ivachnenko, karpinskii Zone (the lower part of the Vyatkian 1990; Golubev, 1998a, 1998c). The pareiasaurs and the Regional Stage) and the Archosaurus rossicus Zone gorgonopians disappear from the dominant block (Fig. 4). (the upper part of the Vyatkian Regional Stage). The herbivorous dicynodonts, Dicynodon sp. become widespread. The predators are represented by the thero- The incorporation of Suchonica vladimiri in the cephalians (a large moschowhaitsiid Moschowhaitsia composition of one of the faunal assemblages vjuschkovi Tatarinov, a nanictidopid Hexacynodon described above creates serious problems. This new purlinensis Tatarinov, and large problematic whaitsi- narrow-armored chroniosuchid is unfortunately known ids) and the first large thecodonts (the proterosuchid only from the type Poldarsa locality, that contains no Archosaurus rossicus Tatarinov). The bystrowianid other terrestrial tetrapod skeletal parts. The localities of

PALEONTOLOGICAL JOURNAL Vol. 33 No. 2 1999 A NEW NARROW-ARMORED CHRONIOSUCHIAN 171 the Il’inskoye subassemblage: Ustye Strel’ny, C. dongusensis. Only the presence of distinct swollen Mikulino, Mutovino and Maryushkina Sluda-C are situ- longitudinal crests on the dorsal surface makes possible ated in the Tatarian section of the Sukhona River strati- the identification of this fragment with C. levis. Assum- graphically higher than the Poldarsa locality (Fig. 3). ing the gradual evolution of chroniosuchid scutes and a Hence, Suchonica may be included either in the com- constant sedimentation rate in the Sukhona River area position of the Il’inskoye subassemblage of the Sokolki during the Poldarsa period, it is possible to suggest, that assemblage, or in the earlier Kotelnich assemblage. In Sokolya Gora and Agafonovo are stratigraphic ana- so far as the typical Il’inskoye fauna is characterized logues of the upper part of the Purtovino Member of the everywhere by wide-armored chroniosaurs, it is possi- Sukhona River section. ble to assume, that Suchonica is a member of the Thus, based on the terrestrial tetrapod data, the lay- aquatic block of the Kotelnich community of the terres- ers of the Kotelnich can be confidently correlated with trial tetrapods. It seems to be impossible to confirm this the lower part of the Poldarsa Formation (Mikulino, suggestion more accurately since it is based principally Strel’na, Isady and Purtovino Members). This conclu- upon the information obtained from the terrestrial tetra- sion is also supported by paleomagnetic information. pods. Nevertheless, this problem may be regarded from The interval of the Sukhona River section considered another point of view. The question on the faunal posi- refers to the paleomagnetic zone of reversed polarity tion of Suchonica is conceptually analogous to the fol- R2P (Opornyi razrez …, 1981). The upper boundary of lowing one: does the Poldarsa locality belong to the this magnetozone is situated within the Kalikino Mem- Deltavjatia vjatkensis Zone or to the Proelginia permi- ber and the lower one within the middle of the Nyuks- ana Zone? Thus, the solution to the problem becomes enitsa Member (Fig. 3). The Kotelnich section is also dependent on detailed comparison of the Sukhona characterized by rocks of reversed polarity (Burov et al., River and the Kotelnich sections. 1996). The summary section of the Upper Tatarian outcrop- Apart from the terrestrial tetrapods the plant ping on the right bank of the Vyatka River downstream remains of Algites sp., Phyllotheca cf. P. turnaensis from the town of Kotelnich is presented in Fig. 3 (the Gorelova, Paracalamites sp., Pecopteris sp., Pel- section description is kindly provided by V.M. Ivach- taspermopsis (?) sp., Permotheca sardykense Zalessky, nenko). The skeletal parts of the Kotelnich assemblage Alicospermum sp., Tatarina conspica Meyen, Purson- terrestrial tetrapods, Deltavjatia vjatkensis, Emeroleter gia beloussovae (Radczenko) Gomankov et Meyen, levis, Viatkosuchus sumini, Karenites ornamentatus, Phylladoderma (Aquistomia) ex gr. P. annulata and Perplexisaurus foveatus, Suminia getmanovi, and Gor- Geinitzia sp. were found in the Kotelnich section gonopidae gen. indet., are found here at the base of the (determinations by A.V. Gomankov). These fossils section in the red marls and aleurolites of layer 1 originate from the lens of light-brown, polymictic, (Kotelnich locality). According to unverified informa- loose sandstones and gray clays (Bed 5) situated on the tion from various researchers, numerous remains of the Chizhi farm. In Gomankov’s opinion (1996), this primitive denticulated dicynodonts, similar to Tropi- assemblage is the closest to the plant assemblage from dostoma, and an incomplete skeleton of Deltavjatia the Sukhona River locality, Ust’ye Strel’ny (the upper- vjatkensis were found at the base of Bed 6 (town of most part of the Strel’na Member). Kotelnich, southern edge, Port Kotelnich locality). The sandy lenses of Sokolya Gora and Agafonovo higher up The Chizhi lens (Bed 5) also yielded the scales of the section (Bed 7) yielded the remains of the fishes, Platysomus biarmicus Eichwald, Toyemia tver- Il’inskoye tetrapod subassemblage, Chroniosaurus dochlebovae Minich, Amblypterina sp., Watsonichthys levis, Proelginia cf. P. permiana, Proburnetia viatken- sp. and Crossopterigii fam. indet. (Esin, 1995; Esin and sis and Dvinosaurus primus. Mashin, 1996). The genus Platysomus is an index of the The composite tetrapod assemblage from the vicin- Platysomus assemblage, characterizing the Ufimian ities of the town of Kotelnich is most similar to that of and Kazanian Stages and the Lower Tatarian Substage the lower part of the Poldarsa Formation of the (Esin, 1995; Esin and Mashin, 1996). Four subassem- Sukhona River section that includes Chroniosaurus blages are recognized within the structure of this dongusensis, Raphanodon tverdochlebovae, Dvinosau- assemblage, the latest of which, the Amblypterina cos- rus sp., Suminia cf. S. getmanovi, Niuksenitia sukhon- tata subassemblage, characterizes mainly the Lower ensis, Sauroctonus cf. S. progressus, Proelginia cf. Tatarian deposits, being associated until recently exclu- P. permiana (Poteryakha-1 and Poteryakha-2, Kochev- sively with the Isheyevo terrestrial tetrapod assem- ala-1 and Kochevala-2, Navoloki, Ust’ye Strel’ny and blage. Mikulino localities). Chroniosaurus levis from Sokolya The genus Toyemia is an index of the Toyemia Gora is more primitive, than the type C. levis from the assemblage characterizing the Upper Tatarian Substage Mutovino and occupies an intermediate position (Esin, 1995; Esin and Mashin, 1996). Three subassem- between the latter and C. dongusensis from the blages are recognized within the structure of this Mikulino locality (Fig. 3). The scutes of Chroniosaurus assemblage, the earliest of which, the Amblypterina from the Sokolya Gora are ornamented by pectinate- pectinata subassemblage, correlates only with the pustular sculpturing that is more characteristic of Il’inskoye tetrapod subassemblage. The Kotelnich ich-

PALEONTOLOGICAL JOURNAL Vol. 33 No. 2 1999 172 GOLUBEV thyoassemblage is probably transitional between the prising its aquatic block, which is missing from the Amblypterina costata and Amblypterina pectinata ich- Kotelnich locality due to taphonomic reasons. thyoassemblages (Esin, 1995; Esin and Mashin, 1998). In conclusion it should be noted that the Deltavjatia In the Sukhona section, Platysomus biarmicus is vjatkensis Zone is an interval of the Tatarian section found in association with the typical Amblypterina cos- characterized by a mixed vertebrate assemblage: the tata ichthyoassemblage: Amblypterina costata (Eich- typically “Late Tatarian” tetrapods of the theriodont wald), Xenosynechodus egloni Glückman, Lapkosubia superassemblage are associated with the “Early Tatar- barbolepis Minich, Paramblypterus sp., Varialepis sp. ian” fishes of the Platysomus assemblage. This sug- and Acropholis sp. in the Mikulino Member sandstones gests, that the largest events in the Late Permian history of Bed 10 of the Nikulino section (Nikulino-1 locality), of tetrapods and fishes in Eastern Europe were asyn- as well as in the stratigraphically lower deposits. Apart chronous and that a significant change in the terrestrial from the Suchonica remains, the Poldarsa locality pro- tetrapod community occurs earlier than in the ichthyo- duced the scales and teeth of fishes, Platysomus fauna. Even the aquatic block of the terrestrial tetrapod biarmicus, Kargalichthys efremovi Minich, Reticulole- community, most closely bound to the fish community pis insolita Mashin et Esin, Amblypterina costata, and trophically, is quite independent in relation to the latter. Xenosynechodus egloni.2 The first occurrence of the Apart from the Kotelnich and Poldarsa localities, genus Toyemia (T. tverdochlebovi Minich) is recorded the Ust’-Yelva locality (the upper part of the Mezen simultaneously with other typical Amblypterina pecti- River, Komi Republic; Fig. 1) is distinguished by a nata subassemblage members: Amblypterina pectinata mixed vertebrate assemblage. In 1994 V.V. Bulanov Esin, Varialepis minichorum Mashin, Varialepis cf. discovered here the skull roof of Raphanodon cf. V. orientalis (Eichwald.), Elonichthys sp. and Acropho- R. tverdochlebovae and scales and teeth of fishes, lis sp. in the upper part of the Strel’na Member (Ust’ye Platysomus biarmicus, Kargalichthys efremovi, Reticu- Strel’ny). Thus, it may be suggested, with a certain lolepis insolata, Xenosynechodus egloni, and Param- degree of confidence that the layers containing the blypterus kucenkoi Esin. In D.N. Esin’s opinion (pers. Kotelnich ichthyoassemblage in the Sukhona River comm.), this ichthyoassemblage is the closest to that of section are situated within the 15 meter interval limited the Poldarsa locality. Hence, the Ust’-Yelva tetrapod by the fossiliferous layers of the sites Nikulino-1 and fauna may also be included in the Kotelnich assem- Ust’ye Strel’ny (the upper part of the Mikulino Mem- blage. ber and the lower part of the Strel’na Member). Hence, Thus, the aquatic block of the Kotelnich terrestrial the layers containing the tetrapod fauna of the tetrapod community of Eastern Europe is formed of the Kotelnich assemblage, which are older than those of the groups typical of the theriodont superassemblage: the Kotelnich ichthyoassemblage, may occur less fre- chroniosuchids and the leptorophids. quently within the Sukhona River section above the upper part of the Strel’na Member. This may also be supported by the fact, that the Il’inskoye tetrapod fauna ACKNOWLEDGMENTS is always found in association only with the Amblypte- The work was supported by the Russian Foundation rina pectinata subassemblage fishes anywhere within for Basic Research, project no. 96-15-98069. the limits of the East-European platform. Therefore the lower boundary of the Proelginia permiana Zone at the Sukhona River cannot be situated below the middle part REFERENCES of the Mikulino Member (the base of layer 11 of the Burov, B.V., Zharkov, I.Ya., Nurgaliyev, D.K., Bala- section Nikulino; Fig. 3), in so far as the underlying banov, Yu.P., Borisov, A.S., and Yasonov, P.G., Magneto- deposits, as was mentioned above, are characterized by stratigraphic Characteristics of Upper Permian Sections in the Amblypterina costata subassemblage. Volga and Kama Areas, in Stratotypes and Reference Sec- tions of the Upper Permian in the Regions of the Volga and Thus, the data on the terrestrial tetrapod, fishes, Kama Rivers, Moscow: Geos, 1998, pp. 236Ð262. plants, and paleomagnetism suggest that the layers in Golubev, V.K., Crucial Events in the Evolution of Tetrapod the Kotelnich locality correlate with the lower part of Community in the Permian of Eastern Europe, in Ecosystem the Strel’na Member and immediately underlying Evolution Abstracts of Intern. Symp., Moscow: Paleontol. deposits of the Sukhona River. Moreover, the boundary Inst. Ross. Akad. Nauk, 1995, p. 28. of the Deltavjatia vjatkensis and the Proelginia permi- Golubev, V.K., Narrow-Armored Chroniosuchians (Amphibia, ana zones runs here between the layers 10 and 30 in the Anthracosauromorpha) from the Late Permian of Eastern Nikulino section. It is here tentatively traced at the base Europe, Paleontol. Zh., 1998a, no. 3, pp. 64Ð73. of layer 19 (Fig. 3). Thus, the Poldarsa locality is dated Golubev, V.K., Revision of the Late Permian Chroniosu- by the Deltavjatia vjatkensis Zone. Hence, Suchonica chians (Amphibia, Anthracosauromorpha) from Eastern may be included within the Kotelnich assemblage com- Europe, Paleontol. Zh., 1998b, no. 4, pp. 68Ð77. Golubev, V.K., Terrestrial Vertebrates, in Stratotypes and 2 Here and further on the fish remains identifications were carried Reference Sections of the Upper Permian in the Regions of out by D.N. Esin and V.L. Mashin. Some identifications may be the Volga and Kama Rivers, Moscow: Geos, 1998c, pp. 227Ð found in Esin and Mashin (1996). 235.

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Gomankov, A.V., The Palynological and Floristic Character- Triassic Continental Deposits Conference), Moscow, Decem- istics of the Tatarian, in Stratotypes and Reference Sections ber 14Ð15, 1992, Abstracts of Papers, Moscow: Paleontolog- of the Upper Permian in the Regions of the Volga and Kama ical Inst. Ross. Akad. Nauk, 1992, pp. 6Ð7. Rivers, Moscow: Geos., 1998, pp. 222Ð227. Ivachnenko, M.F., Primitive Titanosuchian Dinocephalians Esin, D.N., Late Permian Palaeoniscids of the European Part from the Late Permian of Eastern Europe, Paleontol. Zh., of Russia, Cand. Sci. (Geol.ÐMin.) Dissertation, Moscow: 1995, no. 3, pp. 98Ð105. Mosk. Gos. Univ., 1995, pp. 1Ð23. Ivachnenko, M.F., Primitive Anomodonts, Venjukovia, from Esin, D.N. and Mashin, V.L., Ichthyoliths, in Stratotypes and the Late Permian of Eastern Europe, Paleontol. Zh., 1996, Reference Sections of the Upper Permian in the Regions of no. 4, pp. 77Ð84. the Volga and Kama Rivers, Moscow: Geos, 1998, pp. 176Ð 188. Ivachnenko, M.F. and Tverdochlebova, G.I., Sistematika, Ivachnenko, M.F., Faunal Tetrapod Assemblages of the Late morfologiya i stratigraﬁcheskoe znachenie verkhneperm- Permian of Eastern Europe, Byull. Mosk. OÐva Ispyt. Prir., skikh khroniozukhov vostoka Evropeiskoi chasti SSSR (Sys- Otd. Geol., 1990, no. 6, pp. 55Ð60. tematics, Morphology and Stratigraphical Importance of the Ivachnenko, M.F., Late Permian Tetrapod Faunistic Assem- Upper Permian Chroniosuchians of the East of the European blages of Eastern Europe and Their South Gondwana Ana- Part of USSR), Saratov: Saratov. Univ., 1980. logues, Soveshchanie: Paleontologiya i stratigraﬁya konti- Opornyi razrez tatarskogo yarusa reki Sukhony (Reference nentalnykh otlozhenii permi i triasa Severnoi Evrazii (Pale- Section of the Tatarian of the Sukhona River), Saratov: Sara- ontology and Stratigraphy of the North Eurasin Permian and tov. Univ., 1981.

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