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24EARTH SCIENCES
NEW MIDDLE-LATE DEVONIAN PLICATHYRIDINAE (ATHYRIDIDA, BRACHIOPODA) FROM WESTERN GERMANY AND EAST-EUROPEAN PLATFORM (RUSSIA)
Grunt T.
Dr. of Biology
Autonomous Noncommercial Organization: Laboratory-Studio "Live Earth " Moscow, Russia DOI: 10.24412/2701-8377-2021-4-1-8-21
Abstract
Two new genera: Tumidinathyris from the Middle Devonian of the Eifel Hills (Germany) and Anathyroides from the Late Devonian of the West and East-European basins established. Intanathyris orlovi gen. et sp. nov. originates from the Late Devonian (Famennian Stage) of the Subpolar Urals. Classification of Superfamily Athy-ridoidea and distribution of Subfamily Plicathyridinae in the Middle-Late Devonian deposits of Germany and East-European Platform discussed.
Keywords: Brachiopoda, Athyridida, Middle Devonian, Eifelian Stage, Germany, Eifel Hills, Late Devonian, East-European Platform, Frasnian Stage, Famennian Stage.
Introduction. This study keeps on the investigation of brachiopods from the Subfamily Plicathyrididinae (Athyrididae, Athyridida) of the Eifel Hills and environs of Aachen in Germany as well as in the Middle-Late Devonian of the East-European Platform. In the Middle Devonian (Givetian Stage) of the Eifel Hills Plicathyrididinae has been ascertained now for the first time and presented by a new genus Tumidinathyris. In the Late Devonian (Frasnian Stage) it is presented by a single new genus Anathyroides. In the Middle Devonian (Eifelian Stage) of the East-European Platform only solitary specimens of ?Anathyroides Grunt, gen. nov. reported from the Timan Mountain-ridge. In the Late Devonian of the East European Platform and its framework Plicathyrididinae are more diverse. Anathyroides helmerseni (Buch, 1840) wide-spread within the Middle Frasnian deposits of the Main Devonian Field and Central Devonian Field. Six more species could be provisionally attributed to Anathyroides basing their markedly distinguishing external characteristics. Intan-athyris Grunt, gen. nov. established in the Famennian Stage of the Tschernyschew Ridge (Subpolar Urals).
Geological Setting. The Middle Devonian sequence of the Eifel Hills is subdivided into several formations, subformations and members, which are separated by both lithological and faunal criteria. The reference profile is the so called "Type Eifelian Profile" within the Hillesheim Syncline investigated precisely by W. Struve [1], who was the leading expert in the Devonian sections and faunas of the Eifel region. In 2008 Struve and his co-authors [2] presented a detailed review of the stratigraphy of this territory. Detailed Main limestone synclines within the "Limestone synclino-rium" examined in [3].
Athyrididae are distributed nearly throughout the complete Middle Devonian of Eifel Hills (Fig. 1) from the Lauch Fm. to the Kerpen Fm. Their maximum is found in the Eifelian (Lauch, Nohn, Ahrdorf, and Junkerberg Fms.). The distribution of the main taxa was considered by Alvarez and co-authors [4, text-fig. 6]. Between these, a single new genus Tumidinathyris and T. tumida (Kayser, 1871) regarded here as its type species attributed to subfamily Plicathyridinae Alvarez, 1990 occurs only in the Early Givetian of the Soetenish Syncline (Eifel Hills).
Figure 1. Position of the Eifel Hills and Aahen in the territory of Germany.
Middle-Late Devonian biostratigraphy and palaeontology well known from the initial works of D.V. Nalivkin [5, 6], A.I. Ljaschenko [7, 8. 9, 10] and many more authors. In present publication used a palaeogeo-graphic chart of Devonian basin of the East-European Platform (Fig. 2) elaborated by P.V. Fokin [11, 12].
Material and methods. The studied fossils (in total more than 100 specimens) are deposited mainly in the Museum of Natural History in Berlin (MB.B.) and in the Research Institution Senckenberg (Museum of Natural History) in Frankfurt am Main (SMF). Several specimens from the Eifel Hills with precisely determined modern stratigraphical data were donated by amateur collectors: the late Volker Ebbighausen. and the
late Gerd Trost. Some minor material on Anathyroides calestiennensis (Mottequin et al., 2016) provided by P. Sartanaer comes from the Late Devonian of the environs of Aachen.
Collection of Anathyroides helmerseni (Buch, 1840) provided by E. Sokiran from All-Russian Research Geological Institute, St.-Petersburg (VSEGEI) originates from the type locality of the Frasnian Stage of the north-western part of the East-European Platform). Intanathyris orlovi Grunt, gen. et sp. nov. collected by the author in 1985 originates from the Famennian of Subpolar Urals in Russia (Fig. 2).
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Figure 2. Late Devonian palaeogeography of the East-European Platform [11, modified]. Legend: Main Devonian basins: I-Moscow Syneclise; II-Cysbaltic Syneclise (Main Devonian Field); III-Volga-Uralian Region; IV-Lvov Depression; V-Pripyat-Dnepr-Donetsk Rift System; VI-Ciscaspian Depression; VII-Timan-Pechora Region. Sediments: 1-continental, mainly clastic; 2-off-shore marine and deltaic clastic and mainly clastic; 3-shallow marine and lagoonal, with significant clastic component; 4-marine, mainly carbonates, and lagoonal evaporates; 5-eroded land; 6-localities of athyridids; 7-boundaries of the Platform; 8-continental slope; 9-oceanic crust; 10 - numbers, showing position of the main Devonian basins. .
The available, often tope collections allowed first intensive studies of the internal shell structures for several species and genera which were mainly diagnosed in the past using only external features. Investigation of the interior structures was done by conventional methods: preparation of specimens using steel needles, examination with Nikon SMZ-JOA binocular microscope, preparation of serial acetate peels, scanning of acquired replicas with Epson Perfection 2400 Photo scanner (depth resolution about 1 cm). Illustrations of shell interiors used the Jack Paint Shop Pro 8 program (http//www.jack.com). All specimens figured in present publication with prefix MB.B. are housed in the Berlin Museum of Natural History. Classification of the Order Athyridida Dagys, 1974 with special reference to the Superfamily Athyridoi-dea Davidson, 1881.
A.S. Dagys [13] for the first time substantiated an order rank for athyridids regarded for a long time as a group of obscure systematic position. The authorship of the order for a long time was injustice wrong attributed to A. Boucot et al. [14]; [for details see: 3]. Dagys [13] included in this order two suborders: Athyrididina Boucot, Johnson et Staton, 1964 and Retziidina Boucot, Johnson et Staton, 1964. Following Dagys athyridids were accepted as a separate order subdivided in two suborders (Athyrididina and Retziidina) by all following authors [for example see: 15, 16, 17]. Later suborder Koninckinidina Harper, 1993 was also attributed to the order Athyridida [18] and then by Alvarez et al. [19]. Radical revision of the order Athyridida by Alvarez et al. [19] and then by Alvarez and Rong [20] was done based only on a mechanic cladystic analysis of 37 external and internal characters of athyridids. Phyloge-netic trends were completely ignored. In particular the attribution of Koninckinidina to the order Athyridida is extremely doubtful. In present publication subdivision of Athyridida accepted into two suborders. Suborder Athyrididina involves non-punctate shells, smooth or covered by concentric lamellae, sometimes imbricated or spinose. Radial ornament in Athyrididina not observed. Suborder Retziidina characterized by "rhyn-chonelliform" plicate or ribbed sculpture and punctate or non-punctate structure of the wall. It divided into two superfamilies: Retzioidea Waagen, 1883, includes punctate shells; Athyrisinoidea Grabau, 1931, characterized by non-punctate shell. Atyrisinoidea subdivided into two families: Athyrisinidae Grabau, 1931 and Retziellidae Rzhonsnitskaya, 1974. Dorsal valve of Retziellidae characterized by disjunct hinge plate composed of a pair exterior hinge plates and median septum forming septalium similar to septalium of Meristelloi-dea. Family Athyrisinidae characterized by conjunct hinge plate.
Origin of suborder Retziidina (and the order Ath-yridida in general) is likely connected with the silicifi-cation of soft spiral supports by a small group of rhyn-chonellids characterized by radial external sculpture, non-punctate wall and well developed septalium formed by linking of exterior hinge plates and middle septum within the dorsal valve. The development of Retziidina originated in two directions: Athyrisinoidea maintained non-punctate wall of the shell, while Retzi-oidea gathered a punctate structure.
The representatives of the suborder Athyrididina completely lost radial sculpture in the process of histor-
ical development. Superfamily Meristelloidea characterized by a smooth shell and the presence of septalium, the same as septalium characteristic for Retzielloidea in dorsal valve. Genus Triathyris Boucot, Johnson, Staton, 1965 was selected as a type genus for established in [19] monotypic subfamily Triathyridinae Alvarez et al., 1998, which in turn became a type for the family Triathyrididae Alvarez et al., 1998. Genus Sep-tathyris Boucot, Johnson, Staton, 1964 was selected by the same authors as a type genus for monotypic subfamily Septathyridinae Alvarez et al., 1998 within the family Triathyrididae Alvarez et al., 1998 of superfamily Meristelloidea Waagen, 1883. Before now these two genera (Triathyris and Septathyris) according to [19] characterized by a presence of septalium in dorsal valve, were attributed to subfamily Plicathyridinae.
Historically, the subsequent superfamily Athy-ridoidea was formed by fetalisation of meristelloid sep-talium and formation on its basis of conjunct hinge plate. This conclusion is confirmed by the presence of distinct meristelloid septalium observed at the earliest ontogenetic stages in many genera of athyridoids. Sporadic appearance of thin radial striae both in the outer surface and in the inner layers of the shell in several genera of superfamily Athyridoidea, also indicates that the ancestrals for this group were likely to be "rhyncho-nelloid" forms. Thus, the development of the order most likely evolved in two directions: on the one hand, by preserving "rhynchonelloid" shell in representatives of Retziidina and its loss in Athyrididina [17].
Contrary to present classification, in the variant proposed in [20] Retziellidae are considered to be a separate superfamily within suborder Athyrididina. Athy-risinidae attributed to the family Athyrididae in the rank of subfamily. In the frames of this classification "rhyn-chonelliform" representatives of Athyridida must belong to three different groups, which demonstrate independent generation of radial sculpture several times along the development of the order. However, it does not confirm the main trends of evolution of articulate brachiopods.
Suborder Athyrididina according to the classification accepted in this publication includes three super-families: Meristelloidea Waagen, 1883; Athyridoidea Davidson, 1881 and Nucleospiroidea Davidson, 1881. The representatives of Meristelloidea characterized by smooth shell and disjunct hinge plates united with median septum forming septalium within brachial valve. Superfamily Athyridoidea characterized by a smooth shell or existence of external concentric sculpture consisting of growth lines or lamellae, sometimes projecting anteriorly as flat solid spines. Hinge plate solid, conjunct, visceral foramen open, sometimes infilled. Dorsal median septum usually short or average, not merged with the hinge plate. Occasionally inner hinge plate may be supported by a dorsal median septum.
Athyridoidea differs from Meristelloidea by the absence of septalium in brachial valve; from Nucleo-spiroidea-by very diverse sculpture and otherwise type of hinge plate in dorsal valve.
The classification of superfamily Athyridoidea according to [21], includes three families: Hyattididae Sheehan, 1977, Athyrididae Davidson, 1881 and Diplo-spirellidae Schuchert, 1894. Attribution of monotypic family Hyattididae to Athyridoidea in [21] contradicts to the new investigations of P. Copper and J. Jin [22]. Starting from the classical monograph of D. Hall and
D. Clark [23] all the other researchers [24, 16, 17] and many others attribute genus Hyattidina Schuchert, 1913 to the family Meristellidae. Likewise, Copper and Jin [22] consider Hyattidinae to be a junior synonym of Hindellinae Schuchert, 1894. Therefore, in present classification Hyattidinae definitely attributed to the family Meristellidae of superfamily Meristelloidea.
Family Athyrididae according to the system proposed in «Treatise on invertebrate paleontology......"
[21] includes 11 subfamilies (Didymothyridinae, Athy-ridinae, Cleiothyridininae, Lochengiinae, Athyrisini-nae, Spirigerellinae, Comelicaniinae, Pradoiinae, Plicathyridinae, Helenathyridinae) combining more than 70 genera, namely around a half of all known genera and more than 2/3 of all known species nowadays included in the order Athyridida. Evidently that in this variant family Athyrididae includes morphologically heterogeneous genera never related historically.
Contrary to the classification elaborated in [20] the present classification of superfamily Athyridoidea subdivided into 5 families: Athyrididae Davidson, 1881; Didymothyrididae Modzalevskaja, 1979; Lochengiidae Ching and Yang, 1977; Comelicaniidae Merla, 1934 and Diplospirellidae Schuchert, 1894. Subfamily Ath-yrisininae Grabau, 1931 in present classification considered in the rank of family within superfamily Retzi-elloidea of suborder Retziidina. Alvarez and Rong [20] erroneously declared Flexathyris Grunt, 1980 to be a junior subjective synonym of Lochengia Yoh, 1929, and therefore the Flexathyridinae Grunt, 1984 to be a synonym of Lochengiinae Ching and Yang, 1977. In this publication Flexathyridinae classified as Athyridi-dae quite unrelated to exotic Chinese family Lochengi-idae. The validity of both the subfamily Flexathyridinae and the family Lochengiidae discussed in details in [3]. Both Alvarezites Struve, 1992 and Bruntonites Struve, 1992, which are quite similar to each other in the aspect of external and internal structures, surely are connected in phylogenetic aspect with the Lower Carboniferous (Visean) genus Flexathyris Grunt, 1980-in terms of smooth posterior shell surface, similar outline, and internal structures and definitely belong to Flexathyridinae. Subfamily Didymothyrididae in present publication considered in family rank. Comelicaniinae and Compositinae, attributed in [20] to Athyrididae, in present publication united within family Comelicaniidae.
Systematic palaeontology Order Athyridida Dagys, 1974 Suborder Athyrididina Boucot, Johnson et Staton, 1964
Superfamily Athyridoidea Davidson, 1881 Family Athyrididae Davidson, 1881
Diagnosis. Shell of various dimensions and outline; median sulcus in ventral and fold in dorsal valves present; additional radial folds in lateral slopes sometimes overseen. Concentric sculpture developed in a varying degree. Hinge plate subquadrate or subtriangu-lar in outline. Visceral foramen present, sometimes infilled. Hinge process poor developed or absent.
Included subfamilies. Six subfamilies: Athyridi-nae Davidson, 1881; Flexathyridinae Grunt, 1984; Plicathyridinae Alvarez, 1990; Cleiothyridininae Alvarez, Rong et Boucot. 1998; Helenathyridinae Dagys, 1974; Pradoiinae Garcia-Alkalde, 1986.
Comparison. From the rest families differs by well developed concentric sculpture.
Occurrence. Lower Devonian-Late Permian, cos-mopolitian.
Subfamily Plicathyridinae Alvarez, 1990
Diagnosis. Shell of medium to large size, moderately to strongly biconvex; ventral interarea moderate to extensive, almost straight, equal to or slightly shorter than maximum width; folding mixed; anterior margin emarginated. External sculpture consists of numerous concentric, fine imbricate lamellae projecting outwards. Ventral dental plates thin subparallel or converging dorsally slightly concave. Dorsal hinge plate rather wide, concave and commonly with the median part projecting in anteriorly-ventral direction; outer hinge plates reduced; hinge process moderately developed or absent.
Comparison. From the rest subfamilies of the family Athyrididae differs by its peculiar "spiriferoid" outline of the shell and well developed ventral interarea.
Remarks. F. Alvarez [25] erected a new subfamily Plicathyridinae comprising Plicathyris Khalfin, 1946; Anathyris Peetz, 1901 and a new genus Hexarhytis within family Athyrididae. M.A. Rzhonsnitskaya and T.L. Modzalevskaya [26] established three groups of species within genus Anathyris: "An. phalaena", "An. helmersenf and "An. tschernyschewi" considered as phylogenetic lineages. Alvarez et al. [19] following [26] additionally attributed genus Anathyrella Khalfin, 1960 to subfamily Plicathyridinae.
Included genera. Anathyris Peetz, 1901; Anathyrella Khalfin, 1960; Plicathyris Khalfin, 1946; Sulcathyris Durkoop, 1970; Hexathyris Alvarez, 1990; Anathyroides Grunt, gen. nov.; Tumidinathyris Grunt, gen. nov. and Intanathyris Grunt, gen. nov.
Occurrence. Lower Devonian (Lochkovian Stage)-Late Devonian (Famennian Stage) predominately from Eurasia.
Genus Anathyroides Grunt, gen. nov.
Etymology: by external similarity to Anathyris Peetz, 1901.
Type species: Terebratula Helmersenii Buch, 1840; Late Devonian, Frasnian Stage; East-European Platform, Novgorod Region, Russia.
Diagnosis. Shell small to medium size, subtrape-zoidal to fusiform in outline, equally or ventribiconvex; hinge line slightly incurved. Maximum width confined to the posterior part of the shell. Interarea low long poor developed. Distinctive sulcus present in both ventral and dorsal valves. Sculpture represented by thin, regular, dense concentric growth lamellae. Valves thickened. Ventral dental plates thin divergent, well differentiated. Dorsal hinge plate thin quadrangular in outline. Hinge process not pronounced. Visceral foramen occupies the apex of dorsal valve and hinge plate. Number of wroles in spiralia reaches 10-12.
Other species. Besides type species several species coming from Middle-Late Devonian of the East-European Platform and its framework could be provisionally attributed to this genus basing their markedly distinguishing external characteristics despite the internal details of these species are still unknown. Namely they are: ?Anathyroides angustus (Nefedova, 1955) from the Eifelian sediments of South Timan; ?Anathyroides monzevi (Nalivkin, 1941); ?Anathyroides svinordensis (Nalivkin, 1941);and ?Anathyroides petinensis (Ljaschenko, 1959) from the Frasnian Stage of East-European Platform. Anathyroides calestiennensis (Mottequin et al., 2016) occurring in the Late Devonian
of Dinant Sinclinorium in the borderland territories of North France, South Belgium and West Germany definitely belongs to a new genus.
Comparison. Markedly differs from Anathyris Peetz, 1901 in other external outline, incurved hinge line, indistinctive low interarea and vast foramen. Internally it differs by thin hinge plate and absence of cardinal process. From Intanathvris Grunt, gen. nov..
Anathyroides differs by well developed sulcus in ventral and dorsal valves, vast foramen, regular dense distinctive concentric lamellae and absence of external radial sculpture. From Tumidinathyris Grunt, gen. nov. Anathyroides differs in transverse outline of the shell, fine concentric sculpture and the absence of median septum merging with hinge plate within dorsal valve.
Figure. 3.
1. Anathyroides helmerseni (Buch, 1840): lectotypeMB.B.197.1, complete shell, in dorsal, ventral, posterior and anterior views. Russia, East-European Platform, Novgorod Region, near Ilmen Lake, environs of the village Bu-
regi; Late Devonian, middle part of the Frasnian Stage, Buregi Layers (coll.G. Helmersen). 2-4. Anathyroides calestiennensis (Mottequin et al., 2016): 2-sp. MB.B. 1789, complete shell in dorsal, ventral, posterior, anterior and lateral views; 3-sp. MB.B.1791, 3a-3f complete shell in dorsal, ventral, lateral, anterior and posterior views; 3g-exterior sculpture; 4-sp. MB.B. 1790, 4a-4d complete shell in dorsal, ventral, anterior and posterior views; 4e - exterior sculpture; Germany, Stolberg near Aachen, Veidre; Late Devonian, Lower Frasnian, Grenzichiefer Formation (coll. P. Sartanaer).
Remarks. Until recently, information regarded the internal structure of the type species of Anathyris (Spi-rifera) phalaena Phillips, 1841, basing the type material from the Eifelian of Great Britain absent. A detailed description of the type species, including its internal structures, given in [25] basing the abundant material originating from the lower Devonian of the Cantabrian Mountains (Spain). Rzhonsnitskaya and Modzalevskaya [26] for the first time pointed out differences between typical Anathyris (An. phalaena) and two other groups of species (close to An. helmerseni and An. tschernyschewi) regarded as separate phyloge-netic lineages, essentially different from the "Anathyris phalaena" group. "An. helmersenf' group in present publication considered as a separate new genus Anathy-roides.
Occurrence. Middle Devonian (rare)-Late Devonian (usually) of East-European Platform and its north-
ern framing. One species originates from the Late Devonian of southern Belgium, northern France (Dinant Synclinorium), Western Germany.
Anathyroides helmerseni (Buch, 1840) Figs. 3.1; 4 Terbratula Helmerseni sp. n—[27, S. 59] Anathyris helmerseni— [15, p. 59 (see synonymy), Pl. I, figs. 1-7]
Lectotype-MB.B.197.1, complete slightly destroyed shell; housed in Berlin Museum of Natural History (Germany); East-European Platform, Novgorod Region, near Lake Ilmen, environs of the village Buregi (Russia); Late Devonian, Frasnian Stage (middle part), Semilukian Horizon, Buregi Layers; (coll. G. Helmersen). Selected by D. Weyer, figured in [15, p. 59, Pl. I, fig. 7).
Material. 15 complete shells from the type locality (coll. E. Sokiran, VSEGEI). .
Figure 4. Anathyroides helmerseni (Buch, 1840): sp. MB.B.1788 (total length 11.3 mm); transverse serial sections showing the structure of cardinalium; Russia, East-European Platform, Novgorod Region, near Ilmen Lake, environs of the village Buregi; Late Devonian, middle part of the Frasnian Stage, Buregi Layers (coll. E.
Sokiran).
Description. Shell of small size (up to 16.2 mm long, up to 28.8 mm wide and 11.2 mm thick), fusiform to alar-trapezoidal in outline, moderately and equally biconvex; maximum width confined to the hinge line; the width considerably exceeding its length (W/D up to 1.84). Shell sharply constricting towards the front margin. Maximum thickness confined to its posterior part. Hinge line long, slightly incurved; ears acuminate. Lateral commissures straight; front commissure parasul-cate. Ventral valve subpentagonal in outline, evenly bent in lateral profile, rounded in transverse profile. Sulcus
distinct, triangular, originating at the umbo and expanding sharply towards the front margin; it flanked by two symmetrical well defined rounded folds, starting from the umbo and expanding towards the front margin. The beak is slightly incurved over the interarea. Apical angle 115—1270. Foramen vast, rounded. Dorsal valve fusiform in outline, flattened. The beak not defined. In the middle part of the valve two distinct folds, half-round in cross-section, beginning near umbo and widening towards the front margin and divided by a distinct sulcus, turning into a narrow tongue. Sculpture consists of numerous regularly spaced concentric fine lamellae, covering the entire shell, but especially numerous and dense in the front region (Fig. 3.1)Valves thickened. Ventral dental plates short, thin slightly concave in median part and converge dorsally They developed at about 0.7 mm from ventral umbo and separate a wide pedicle cavity of sub-rectangular section, from a pair of smaller lateral apical cavities of subtriangular section (Fig. 4). They extend up to 4 mm from the apex and occupy half the height of the ventral cavity in the articulation plane. In that plane teeth are big, subtrian-gular to rectangular. In the corresponding position the dorsal valve has rather deep dental sockets, bordered laterally by prominent inner socket ridges and lower outer socket ridges. Within dorsal valve the hinge plate thin rectangular, concave. Hinge process not pronounced. Visceral foramen occupies the apex of the dorsal valve and hinge plate. In its slopes there are two
symmetrically located pits, apparently serving for a more certain articulation of the valves. Visceral foramen sometimes overgrown, and additional pits are absent. Median ridge low poor developed (Fig. 4).
Comparison. The present species differs from An. calestiennensis (Mottequin et al., 2016) definitely attributed to Anathyroides by its smaller dimensions, sub-trapezoidal in outline and acuminate cardinal extremities. An. helmerseni (Buch, 1840) externally most allied to a group of Frasnian species from the East-European platform. It differs from ?An. svinordensis (Nalivkin, 1941) by a more distinctive sulcus and lateral folds of the ventral valve, as well as by more pronounced folding of front margin; from ?An. monzevi (Nalivkin, 1941) it distinguished by larger size of the shell; from ?An. petinensis (Ljaschenko, 1959) is differs by smaller dimensions of the shell, its smaller transverse extension and rare growth lamellae.
Remarks. The study of specimens identified by a number of researchers as An. helmerseni (Buch) from the Upper Devonian of the Kuznetsk Depression gives evidence, that the latter characterized by another type of internal structure [26]. Among them the presence of the cardinal process, which is absent in the type specimens of this species from the East-European Platform, more massive short dental plates and somewhat other position of visceral foramen [15, fig. 19]. The observed differences correspond to the generic level.
Occurrence. Late Devonian of the East-European Platform (Russia): Frasnian Stage, Buregi Layers (usually), Svinordski Layers (rare) of the Main Devonian Field and Central Devonian Field. Anathyroides calestiennensis (Mottequin et al., 2016) Figs. 3.2-4; 5a, b Anathyris calestiennensis sp. n.—[28, p. 383 (see synonymy), figs. 4, 5, 6 (1-10)]
Holotype-IRScNBa13023, complete shell well preserved; figured in [28, fig. 4.1-5); Late Devonian of northern France (Dinant Synclinorium). Housed in the Royal Institute of Natural History (Brussels, Belgium).
Figure 5a. Anathyroides calestiennensis (Mottequin et al., 2016): sp. MB.B. 1789 (total length 16,9 mm; thickness 9,0); transverse serial sections showing the structure of cardinalium; Germany, Stolberg near Aachen, Veidre; Late Devonian, Lower Frasnian, Grenzichiefer Formation (coll. P. Sartanaer).
Figure 5b. Anathyroides calestiennensis (Mottequin et al., 2016): sp. MB.B. 1789 (total length 16,9 mm; thickness 9,0);b-serial longitudinal sections; numbers indicate the distance (in mm) from the top convexity of the brachial valve; Germany, Stolberg near Aachen, Veidre; Late Devonian, Lower Frasnian, Grenzichiefer Formation (coll. P. Sartanaer).
Material. 5 complete specimens from Stolberg near Aachen; Veidre, Germany; Late Devonian, Lower Frasnian, Grenzichiefer Formation (coll. P. Sartanaer).
Description. [see 28, p. 383].
Comparison. See An. helmerseni (Buch, 1840).
Occurrence. Southern Belgium, northern France (Dinant Synclinorium) and western Germany; Late Devonian, Frasnian Stage.
Род Tumidinathyris Grunt, gen. nov.
Etymology: after the name of the species "tumidd' suggested by Kayser [29].
Type species. Athyris concentrica var. tumida Kayser, 1871; Germany, Rhenish Massif, Eifel Hills, Soetenish Syncline, "Scheidberg" (probably the abandoned "Schulz Quarry"); Middle Devonian, Early
Givetian (probably the Scheid Member of the Cuerten Formation).
Diagnosis. Shell of medium size, subpentagonal in outline, strongly and equally biconvex. Sulcus and fold well developed. Front commissure strongly parasul-cate. Sculpture represented by several coarse concentric wrinkles. Up to 4-5 thin concentric growth lamellae disposed between wrinkles. Shell thick. Ventral dental plates short convergent dorsally. Dorsal hinge plate massive sub-rectangular, supported by high well developed median septum. Hinge process well developed bilobate, low. Spiralia consists of more than 15 wroles.
Comparison. Differs from Anathyroides Grunt, gen. nov. in isometric subpentagonal outline, coarse concentric sculpture, thick valves, short dental plates
within ventral valve and high median septum merging with hinge plate within dorsal valve.
Remarks. Internal structures of "Athyris" tumida were investigated in details by Alvarez et al. [4]. The species was attributed to Athyris (?n. sg. aff. Al-varezites) tumida Kayser, 1871. However it differs essentially from the internal structures of Alvarezites wol-farti (Struve, 1992) by the other type of dental plates within ventral valve and presence of high dorsal septum merged with the inner hinge plate within dorsal valve. Evidently species under discussion could not be attributed to.4thvris or.4lvarezites [for details see: 3, figs.
4, 8, 9]. Thus, it is possible to agree with the opinion expressed in [4]. The authors assumed the possibility to attribute this species to the taxon of supraspecific rank. However, the possibility of its attribution to a new subgenus of Athyris excluded even when compared the external structure of the species under consideration with typical representatives of Athyris. From the latter it differs essentially by strongly swollen shell, distinct sul-cus and fold, and some other concentric sculpture. Basing these characteristics, it certainly must be attributed to subfamily Plicathyridinae Alvarez, 1990.
Figure 6.
1-3. Intanathyris orlovi Grunt, gen. et sp. nov.: 1-holotype MB.B. 1461, complete shell with partly destroyed left part of hinge area in ventral, dorsal and posterior views; 2-sp. MB.B. 1491, complete shell partly destroyed in dorsal, ventral and posterior views; 3-sp. MB.B.1536, complete shell partly destroyed, in dorsal, ventral and posterior views. Russia, East European Platform, Tschernyshew Ridge, river Sharju, middle stream, left bank, 2.5 km below "Lower Gates"; Late Devonian, Frasnian Stage, Lebedyanian Layers, Palmatolepis marginifera Zone. 4-5. Tumidinathyris tumida (Kayser, 1871): 4-sp. MB.B.1597; complete shell in ventral and dorsal views; 4c-exterior sculpture (coll. Koller 1913). 5-sp. MB.B.1579, complete shell in dorsal, ventral, posterior and anterior views. Germany, Eifel Hills, loc. Soetenish, Pielstein, Scheid limestone quarry, (Soetenish Syncline), Scheid Member, Cuerten Fm. (type locality); Middle Devonian, Givetian Stage (coll. V. Ebbighausen, sp. No. VE 2A3/2).
Other species. Besides the type species, ITumidi-nathyris pentagonalis (Kayser, 1871) from the Junkerberg Formation of Eifel Hills provisory could be assigned to a new genus although the internal structures of the discussed species not studied.
Occurrence. Germany, Rhenish Massif; Middle Devonian, Early Givetian
Tumidinathyris tumida (Kayser, 1871) Figs. 6.4-5; 7 Athyris concentrica var. tumida sp. n-[29, p. 549].
Athyris (Alvarezites) tumida-[4, Pl. 2, figs. 7-9; Pl. 3, figs.11-12].
Athyris (Alvarezites) tumida-[30, S. 84, Taf. 22, fig. 14]
Neotype: complete shell, SMF 54822; Germany, Rheinish Massif, Soetenish Syncline, "Scheidberg" (probably from the abandoned "Schulz Quarry"); Middle Devonian, Early Givetian (probably, the Scheid Member of the Cuerten Formation). Selected in [4, Pl. 8, fig. 44].
Material. 7 complete shells from the type locality (coll. S. Koeller, 1913 and V. Ebbighausen). Description. Shell of medium size, subpentagonal in outline, sub equally biconvex in lateral profile; hinge line short sharp arched, widest at shell midlength. Lateral commissures abruptly incurved. Front commissure parasul-cate. Ventral valve subpentagonal in outline, umbo thick, blunt, perforated by vast round foramen. Apical angle about 115 degrees. Sulcus originates near the beak, shallow, rapidly widening and deepening anteriorly; broad front tongue, occupying about one-third of
shell width. Dorsal valve rounded pentagonal in outline; maximum convexity at midlength. Umbo low thick, rounded. Fold low wide triangular bounded by a pair of distinct troughs in the anterior third of the valve. A narrow median groove observed in the anterior third of the fold (Figs. 16.4-5). Sculpture consists of several very coarse concentric wrinkles. Up to 4-5 thin growth lamellae disposed between wrinkles (Fig. 16 4c).
Ventral dental plates short, divergent extend anteriorly up to 4 mm from ventral umbo, low-grade arched reaching a half of ventral walls. Pedicle cavity broad. Lateral apical cavities almost completely filled by secondary shelly material. Teeth large, sub-ovate. Dorsal hinge plate thick, sub-rectangular. Hinge process bilo-bate, moderately developed, stout, deeply projecting into delthyrial cavity of ventral valve, noticed at 3.24.1 mm from the apex of ventral valve; visceral foramen small. Dorsal median septum high, merged with the inner hinge plate. Number of wroles in spiralia reaches fifteen (Fig. 7).
■10 mm
Figure 7. Tumidinathyris tumida (Kayser, 1871): sp. SFM50016; transverse serial sections showing the structure of cardinalium; Germany, Eifel Hills; loc. Scheidberg, (Soetenish Syncline); Middle Devonian, Givetian Stage (most likely, lower part, presumably Cuerten Formation, ScheidMember (after 4, fig. 13, modified).
Remarks. The internal structure for Athyrs tumida plate within dorsal valve overseen in the earlier ontoge-
were studied in [4, text-fig. 13); it differs strongly from netic stages, and the presence of well developed bilo-
that of Alarezites wolfarti (Struve, 1992) by the pres- bate cardinal process. It was determined by Alvarez et
ence of a high median ridge merged with inner hinge al. (1996) as: Athyris (?n. sg. aff. Alvarezites) tumida
Kayser, 1871. Evidently that this species does not belong either to Alvarezites or Athyris [3, p. 626, figs. 3, 5, for discussion]. Athyrs tumida regarded here as a type species for a new genus belonging to the subfamily Plicathyridinae Alvarez, 1990.
Occurrence. Germany, Rhenish Massif, Soetenish Syncline, "Scheidberg" (probably from the abandoned "Schulz Quarry"); Middle Devonian, Early Givetian (probably, the Scheid Member of the Cuerten Formation).
Род Intanathyris Grunt, gen. nov.
Etymology: from the town of Inta in the north of the Republic Komi (north of the East-European Platform, Russia).
Type species: Intanathyris orlovi Grunt, sp. nov. Russia, Polar Urals, north of East-European Platform, Tschernyschew Ridge, river Sharju, middle stream, left bank, 2.5 km below "Lower Gates"; Late Devonian, Famennian Stage, Lebedyanian Layers, Palmatolepis marginifera Zone.
Diagnosis. Shell of large size for the subfamily, transverse winged, sub-triangular in outline, moderately and equally biconvex. Front commissure sharply sulcate. Ventral valve transverse flattened, sulcus not prominent. Beak low, sharpened, pierced by small, round foramen. Dorsal valve transverse semi-circular
in outline. Fold sharp not limited by lateral depressions. The apexes of both valves are approximately of the same height, slightly protruding beyond the hinge line. Sculpture represented by poor expressed, thin indistinctive concentric growth lamellae. An additional slight radial striation and a more distinct radial ribbing present in the anterior part of the shell. Valves thin. Ventral dental plates and teeth not observed. Hinge plate within dorsal valve thin rectangular. At its lateral margins low trigonal appendixes not reaching the articulation plane available.
Remarks. The present new genus markedly differs from all known genera belonging to Plicathyridinae by the absence of sinus in flattened ventral valve, acute-angular transverse profile of dorsal valve and presence of distinctive external radial sculpture in the frontal part of the shell and another type of inner structures. Internally it distinguished by the very weakly developed cardinal structures in articulation plane.
Other species. Type species.
Occurrence. Subpolar Urals; Late Devonian, Famennian Stage.
Intanathyris orlovi Grunt, sp. nov.
Figs. 6. 1-3; 8
Etymology: in memory of paleontologist Ale-ksandr Orlov.
Figure 8. Intanathyris orlovi Grunt, gen. et sp. nov.: sp. MB.B.1787 (total length 26,8 mm); transverse serial sections showing the structure of cardinalium; Russia, East-European Platform, Tschernyschew Ridge, river Sharju, middle stream, left bank, 2,5 km below "Lower Gates"; Late Devonian, Frasnian Stage, Lebedyanian
Layers, Palmatolepis marginifera Zone.
Holotype: MB.B.1461, complete shell with partly destroyed left apical region; Russia, Subpolar Urals, Tschernyschew Ridge, river Sharju, middle stream, left bank, 2,5 km below "Lower Gates"; Late Devonian, Famennian Stage, Lebedyanian Layers, Palmatolepis marginifera Zone. Housed in Berlin Museum of Natural History,Germany (Fig.6.1).
Material. Four partly destroyed and strongly re-crystallized specimens.
Description. Shell of large size (up to 26.5 mm long, up to 65 mm wide and up to 19.5 mm thick), moderately biconvex, approximately equally biconvex, transversely subtriangular in outline. Maximum width confined to the straightened hinge line. The lateral commissures slightly depressed; front commissure sharply sulcate. Ventral valve transverse-trigonal in outline, inflated or slightly convex. Sulcus not developed. Tongue narrow triangular. Umbo low, sharpened. Beak pierced by very small circular foramen. Umbonal shoulders are not pronounced. Interarea triangonal low. Its length is approximately half the length of the hinge line. Apical angle 78 degrees. Dorsal valve transverse subtriangular in outline, roof-shaped in transverse profile. Sharp fold not limited by lateral depressions. Beak low, sharpened. The apexes of both valves are approximately of the same height, slightly protruding beyond the hinge line. Sculpture poor expressed, concentric growth lamellae very thin dense. On the surface of the shell, there is an additional slight radial striation and a more distinct radial ribbing well observed in the anterior part of the ventral valve. Beak low, sharpened (Fig. 6.1-3). Valves thin. Ventral dental plates and teeth not observed. Only short poor developed delthyrial keels noticed at 2.1-3.3 mm from the apex of ventral valve. Hinge plate within dorsal valve thin quadrangular. At its lateral margins low trigonal appendixes present. Those do not reach the articulation plane. In the middle part of hinge plate low swelling of quadrangular outline disposed (Fig. 8).
Remarks. Actually this species characterized by the nearly absent cardinal structures in the plane of articulation of the shell. Apparently this morphological habitude could be interpreted as a nearly complete reduction of cardinal structures at the finalizing stage of development of the group contemporized with the end of the Devonian period.
Occurrence. Russia, Subpolar Urals, Tschernys-chew Ridge, river Sharju, middle stream, left bank, 2,5 km below "Lower Gates"; Late Devonian, Famennian Stage, Lebedyanian Layers, Palmatolepis marginifera Zone.
Conclusion. From the Eifel Hills subfamily Plicathyridinae Alvarez, 1990 reporte4d by two new genera: Tumidinathyris and Anathyroides. Tumidinath-yris tumida (Kayser, 1871) known from the Cuerten Formation (lower part) of Scheid Member (Givetian Stage, Middle Devonian). In the Late Devonian of Germany Plicathyridinae are very rare. Only one species Anathyroides calestiennensis (Mottequin et al., 2016) known from the Frasnian of the Rhenish Massif, Belgium and France.
In the Middle Devonian of the East-European Platform and its framework solitary specimens of ?Anathyroides angustatus Nefedova, 1955 reported from the Eifelian Stage (Soiva Horizon) of Timan [31]. A supposedly new species of this genus from the Late Give-tian (Chib'usskaja Formation) of the same region also pointed in this publication.
In the Late Devonian of the East European Platform and its framework Plicathyridinae are more diverse. In the middle part of Frasnian Stage Anathyroides helmerseni (Buch, 1840) wide-spread within the deposits of the Main Devonian Field, Central Devonian Field, Saratov Region and South Timan. Six more species could be provisionally attributed to Anathyroides basing their markedly distinguishing external characteristics despite the internal details of these species are not jet studied. Namely they are: ?An. monzevi (Nalivkin, 1941) and ?An. svinordensis (Nalivkin, 1941) from the Middle Frasnian of the Main Devonian Field ; ?An. petinensis (Ljaschenko, 1959) from the Semilukski Horizon of the Central Devonian field; ?An. tarchanensis (Ljaschenko, 1964) of the Volga-Uralian Region; ?An. timanicus (Ljaschenko, 1959) and An. solnzevi (Ljaschenko, 1973) from the Middle Frasnian of South Timan. Intanathyris orlovi Grunt, gen. et sp. nov. originates from the Famennian Stage (Lebe-dyanian Layers, Palmatolepis marginifera Zone) of the Tschernyschew Ridge (Subpolar Urals).
Acknowledgements. I greatly thank the staff of the Berlin Museum for putting the materials in my disposal. I thank D. Weyer, M. Aberhan, D. Korn and the late E. Pietrzeniuk for constant help and kind assistance. I thank the Administration of the Senckenberg Museum and his late director W. Zieger for the financial support. I am indebted to the late Prof. W. Struve, who showed me his Middle Devonian athyridid collections; the discussions with him were very helpful. I am grateful to the late Dr. Sartanaer, G. Trost, the late V. Ebbighausen and E. Sokiran, who provided me their Devonian athyridids. I also thank the late V.T An-tonova (Paleontological Institute, Russian Academy of Sciences) for performing of photographs and A. Zhe-gallo (Institute of Psychology, Russian Academy of Sciences) for the help in compiling computer illustrations.
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