Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ...
Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ... Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ...
82 ADVANCES IN PALAEOICHTHYOLOGY The following vertebrate remains are preliminarily identified from the Zadonskian deposits of the Gornostayevka locality: abundant cranial and postcranial remains of antiarchs “Bothriolepis” zadonica H. Obrucheva, 1983, Bothriolepis sosnensis Moloshnikov, 2003, B. cf. leptocheira Traquair, 1893 and Remigolepis ? sp. (Moloshnikov 2001, 2003); numerous acanthodian fin spines of Devononchus cf. laevis (Gross, 1933); rare isolated bones of the ptyctodontid Chelyophorus sp. and pachyosteomorph arthrodires; abundant scales and bones of the porolepiform Holoptychius cf. nobilissimus Agassiz, 1839, osteolepiforms Megapomus markovskyi Vorobyeva, 1977 and Glyptopomus sp.; numerous tooth plates and rare cranial and postcranial bones of dipnoans Conchodus sp., Holodipterus sp. and Dipterus sp. Material and methods All skeletal fragments were found disarticulated, some of them were broken, while others, thin and fragile, are complete. The internal (visceral) surface is generally well preserved. Cranial materials include: the interorbital part of the skull roof, including the frontals, anterior part of the parietals and almost complete postfrontals preserved in natural contact (PIN 2657/346) and an incomplete angular (PIN 2657/347). Postcranial materials consist of the right cleithrum with partly preserved scapulocoracoid fused to it (holotype PIN 2657/343) and the distal part of the femur (PIN 2657/344). Specimen PIN 2657/346 is chosen as holotype, all the remaining cranial and postcranial materials are referred to it, as there is no certainty in whether all remains belong to the same taxon. The posterior part of the skull roof PIN 2657/348 is questionably assigned to Jakubsonia livnensis gen. and sp. nov. The material is stored in the collection 2657 of the Palaeontological Institute of the Russian Academy of Sciences (PIN). All specimens were prepared manually with mounted needles. Systematic palaeontology Superclass TETRAPODA Goodrich, 1930 Family undesignated Genus Jakubsonia Lebedev, gen. nov. Derivation of name – to honour O.L. Jakubson, the member of the Livny town Natural history and Local Lore museum, who enthusiastically helped excavations. Type species - Jakubsonia livnensis Lebedev, sp. nov. Diagnosis. An early Famennian tetrapod characterised by short snout (estimated by frontals which are only 2.4 times longer than wide) and large orbits. The lateral side of the prefrontal adjoins the lateral margins of the frontal and postfrontal together, the dorsal process of the postorbital abuts the posterolateral part of the postfrontal, rather than wedges between it and the parietal.
O.A. Lebedev. A new tetrapod from Russia 83 Fig. 2. Jakubsonia livnensis gen. and sp. nov., interorbital fragment of the skull roof, PIN 2657/ 346. A, dorsal view; B, ventral view. Jakubsonia livnensis Lebedev, sp. nov. Etymology. After the town of Livny. Holotype. PIN 2657/346, the interorbital part of the skull roof, including the frontals, anterior part of the parietals and almost complete postfrontals preserved in natural contact. Diagnosis. As for the genus. Locality and horizon. Gornostayevka quarry, SW of the Livny Town, Oryol Region, Central Russia, ? triangularis-crepida Zone of the Standard conodont scale, Zadonskian Regional Stage, Lower Famennian, Upper Devonian. Description and comparisons. Skull. The holotype PIN 2657/346, a fragment of the interorbital part of the skull roof (Fig. 2) includes the frontals, anterior part of the parietals and completely preserved postfrontal from the left side and its anterior half from the right side preserved in natural contact. The dorsal side of this fragment is ornamented with pit-and-ridges sculpturing characteristic of all known Devonian tetrapods. The pits are more uniform in size and isometric at the parietals and the postfrontals; in the central part of the frontals they are much deeper, and their outline is irregular. In the anterior part of the frontals these pits even partly merge forming a short deep groove. The anterior, frontal part of the holotype slopes ventrally with respect to the parietal part at an angle of approximately 20º. The frontals and parietals are fused without any
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O.A. Lebedev. A new tetrapod from Russia<br />
83<br />
Fig. 2. Jakubsonia livnensis gen. <strong>and</strong> sp. nov., interorbital fragment of the skull roof, PIN 2657/<br />
346. A, dorsal view; B, ventral view.<br />
Jakubsonia livnensis Lebedev, sp. nov.<br />
Etymology. After the town of Livny.<br />
Holotype. PIN 2657/346, the interorbital part of the skull roof, including the frontals,<br />
anterior part of the parietals <strong>and</strong> almost complete postfrontals preserved in natural<br />
contact.<br />
Diagnosis. As for the genus.<br />
Locality <strong>and</strong> horizon. Gornostayevka quarry, SW of the Livny Town, Oryol Region,<br />
Central Russia, ? triangularis-crepida Zone of the St<strong>and</strong>ard conodont scale, Zadonskian<br />
Regional Stage, Lower Famennian, Upper Devonian.<br />
Description <strong>and</strong> comparisons. Skull. The holotype PIN 2657/346, a fragment of the<br />
interorbital part of the skull roof (Fig. 2) includes the frontals, anterior part of the<br />
parietals <strong>and</strong> completely preserved postfrontal from the left side <strong>and</strong> its anterior half<br />
from the right side preserved in natural contact. The dorsal side of this fragment is<br />
ornamented with pit-<strong>and</strong>-ridges sculpturing characteristic of all known Devonian<br />
tetrapods. The pits are more <strong>un</strong>iform in size <strong>and</strong> isometric at the parietals <strong>and</strong> the<br />
postfrontals; in the central part of the frontals they are much deeper, <strong>and</strong> their outline is<br />
irregular. In the anterior part of the frontals these pits even partly merge forming a short<br />
deep groove.<br />
The anterior, frontal part of the holotype slopes ventrally with respect to the parietal<br />
part at an angle of approximately 20º. The frontals <strong>and</strong> parietals are fused without any
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