A new assessment of the Late Devonian antiarchan fish Bothriolepis leptocheira from South Timan (Russia) and the biotic crisis near the Frasnian-Famennian boundary Author Lukševičs, Ervīns Author Beznosov, Pavel Author Stūris, Valdemārs text Acta Palaeontologica Polonica 2017 2017-02-20 62 1 97 119 http://dx.doi.org/10.4202/app.00265.2016 journal article 10.4202/app.00265.2016 1732-2421 10980819 Bothriolepis leptocheira Traquair, 1893 1869 Pterichthys major ; Geikie 1869 (after Miles 1968 ): 12–13. 1888 Bothriolepis major Agassiz ; Traquair 1888 (after Miles 1968 ): 510. 1893 Bothriolepis leptocheirus sp. nov. ; Traquair 1893: 285–286 . 1900 Bothriolepis jeremejevi sp. nov. ; Rohon 1900: 30 , fig. 18, 19. 1917 Bothriolepis leptocheira Traquair, 1893 ; Evans 1917 (after Miles 1968): 112. 1932 Bothriolepis jeremejewi Rohon, 1900 ; Gross 1932: 34 . 1942 Bothriolepis curonica sp. nov. ; Gross 1942: 420 , 421, abb. 10. 1948 Bothriolepis curonica Gross, 1942 ; Stensiö 1948: 615 . For a full list of synonyms before 1965 see Miles (1968) . Lectotype : RSM 1859.33.19A, AVL plate selected by Gross (1932: 26) , illustrated by Traquair (1906 : pl. 29: 3). Type locality : Bracken Bay, Ayrshire (Heads of Ayr), Scotland ; Type horizon : Upper Old Red Sandstone, Upper Devonian. Emended diagnosis .— Differs from all other Bothriolepis in possessing long supraoccipital groove extending to the Pn plates, sometimes fused with a long middle pit-line, and rather slender proximal segment of the pectoral appendage, which is more than 5 times as long as it is broad. Characterised by a rather large size with a median dorsal armour length of at least 240 mm . Preorbital recess of trifid type . The orbital fenestra is relatively small and narrow. Prm broad, orbital margin is much shorter than rostral margin. Nu with rather short orbital facets. AMD relatively narrow, B/L index about 0.8 (N = 22), with a relatively short anterior margin. PMD broad with narrow anterior margin. Median dorsal ridge poorly developed in posterior part of PMD . Dorso-lateral and ventro-lateral ridges are wellmarked. Both AVL and PVL are elongated. Cv 4 and Cd 5 plates are present in the pectoral fin armour. Ornamentation is fine and basically of reticular type . Fig. 3. Antiarchan fish Bothriolepis leptocheira jeremejevi ( Rohon, 1900 ) , Sosnogorsk locality, Sosnogorsk Formation, lowermost Famennian, separate plates and parts of articulated head shields. A . Articulated Nu, left Pn and left La plates IG KSC 155/90 in dorsal view. B . Disarticulated plates of the head shield IG KSC 155/150 in dorsal view. C . Part of articulated head shield IG KSC 155/162 in dorsal view. D . Imprint of the ventral wall of trunk armour and some skeletal elements of the head armour IG KSC 155/10-3 in ventral view showing suborbital and infragnathal bones. Abbreviations: AVL, anterior ventro-lateral plate; cir, semicircular pit-line groove; csl, central sensory line groove; d.end, opening of canal for endolymphatic duct; ifc 1 , principal section of infraorbital sensory line; IG, inferognathal; La, lateral plate; Nu, nuchal plate; mp, middle pit-line groove; Pn, paranuchal plate; Pp, postpineal plate; Prm, premedian plate; SO, suborbital plate; socc, supraoccipital cross-commissural pit-line groove. Stratigraphic and geographic range .—This species has also been reported from western Latvia , where the material has been collected in the right bank of the river Imula, near Bienes hamlet, and in the left bank of the river Amula, 1 km upstream from water-mill Kalnamuiža; Purviņi Member of the Eleja Formation, lowermost Famennian ( Lukševičs 2001 ). A possible new subspecies of B. leptocheira occurs in the Malyutka Formation of Severnaya Zemlya, outcrops along the Matusevich River ( Lukševičs 1999a , b). The material described in this paper comes from the geological monument “Sosnovskiy” (Sosnogorsk locality) at the right bank of the river Izhma opposite Sosnogorsk, Komi Republic , Russia ; Sosnogorsk Formation, lowermost Famennian.