А New Species of the Genus Lekiskochiton (Mollusca, Polyplacophora) from the Lower Permian Reef Limestones of Shakhtau (Southern Cisuralia)

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Abstract

A new Early Permian Shakhtau reef dwelling lepidopleurid chiton is described as Lekiskochiton crassus sp. nov. This is one of the few Late Paleozoic chitons described in Russia and the first from the Cisuralia. The new species is represented by the tail valve and four intermedial valves belonging to one large animals, which was found in the reef carbonates of the Asselian Stage. Other scattered valves of a new species were found in younger sediments of this reef massif, in the Sakmara Stage. All of them are preserved as imprints. The shape of the valves has been partially reconstructed. The morphological differences in the intermedial plates of one individual of the genus are shown for the first time. L. crassus sp. nov. is the second species of the genus, which was previously reliably known only from the Middle Permian of Texas by the type species only. The discovery of a new species increases the time range of existence of the genus approximately on 19 million years. In the Shakhtau polyplacophoran assemblage, in addition to the genus Lekiskochiton, the following genera have been previously identified: Gryphochiton, Ochmazochiton and Pterochiton, which indicates stable biogeographical connections of the Early Permian Ural Strait with the sea basins of North America.

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About the authors

A. V. Mazaev

Borissiak Paleontological Institute, Russian Academy of Sciences

Author for correspondence.
Email: mazaev.av@mail.ru
Russian Federation, Moscow, 117647

References

  1. Барсков И.С., Морозов П.Е. Хитон (Mollusca, Polyplacophora) из верхнего карбона Подмосковья // Палеонтол. журн. 1996. № 4. С. 3–6.
  2. Бяков А.С., Мазаев А.В. Первые находки древнейших устрицеподобных двустворчатых моллюсков рода Prospondylus Zimmermann (Pectinida, Prospondylidae) в нижней перми Южного Приуралья (Россия) // Палеонтол. журн. 2023. № 3. С. 42–51.
  3. Королюк И.К. Методы и результаты изучения пермского рифогенного массива Шахтау (Башкирское Приуралье). М.: Наука, 1985. 111 с.
  4. Eichwald E. d’. Lethaea Rossica ou Paleontologie de la Russie. V. 1. Sec. 3. Stuttgart, 1860. 1093 p.
  5. Hoare R.D., Plas L.P., Yancey T.E. Permian Polyplacophra (Mollusca) from Nevada, Utah, and Arizona // J. Paleontol. 2002. V. 76. № 2. Р. 256–264.
  6. Hoare R.D., Smith A.G. Permian Polyplacophora (Mollusca) from West Texas // J. Paleontol. 1984. V. 58. № 1. P. 82–103.
  7. Kirkby J.W. On the Permian Chitonidae // Quart. J. Geol. Soc. London. 1859. V. 15. P. 607–626.
  8. Kjrkby J.W., Young J. Notes on some remains of Chiton and Chitonellus from the Carboniferous strata of Yorkshire and the west of Scotland // Geol. Mag. 1867. V. 4. № 38. P. 340–343.
  9. Mazaev A.V. Lower Permian gastropods of Shakhtau (Asselian–Sakmarian boundary beds, southern Cisuralia) // Paleontol. J. 2019. V. 53. № 12. P. 1237–1345.
  10. Schwabe E. Illustrated summary of chiton terminology (Mollusca, Polyplacophora) // Spixiana. 2010. V. 33. № 2. P. 171–194.
  11. Sirenko B. New outlook on the system of chitons (Mollusca: Polyplacophora) // Venus. 2006. V. 65. № 1–2. p. 27–49.
  12. Smith A.G. Hoare R.D. Paleozoic Polyplacophora: a checklist and bibliography // Occas. Pap. California Acad. Sci. 1987. № 146. 71 p.

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2. Fig. 1. Lekiskochiton crassus sp. nov., PIN paratype, No. 5538/7-293, ×2.5, thin lines show the reconstructed outlines of the shields: a – shield IV: a1–a4 – latex impression of the dorsal surface: a1 – oblique front view, a2 – rear view, a3 – right view, a4 – top view; a5, a6 – ventral surface imprint: a5 – top view, a6 – right view (reconstructed using FIG. a3); a7, a8 – latex impression of the ventral surface: bottom view, front view; a9–a11 – tomography: a9 – dorsal view, a10 – front view, a11 – view from the ventral side; b – one of the fragments, prints of the ventral surfaces of shields IV, V and VI are visible (to demonstrate the position of shield V, the ventral surface of shield IV is shown fragmentally); c – a fragment of tomography of the PIN paratype, No. 5538/7-293, the image is inverted; Bashkortostan, Shakhtau quarry, location No. 5538/7; Assel tier. The scale is 5 mm.

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3. Fig. 2. Lekiskochiton crassus sp. nov., ×2.5, thin lines show the reconstructed outlines of the shields: a – PIN paratype, No. 5538/7-293, shield V: a1–a4 – ventral surface imprint: a1 – front view, a2 – top view, a3 – rear view, a4 – view on the left, a thin line shows the position of the dorsal surface (reconstructed using FIG. a7); a5, a6 – latex impression of the ventral surface: bottom view, rear view; a7–a9 – latex impression of the dorsal surface: a7 – right view, a8 – front view, a9 – top view; a10–a13 tomography: a10 – front view, a11 – rear view, a12 – dorsal view, a13 – ventral view; b – ex. PIN, No. 5538/7-292, intermediate shield II: b1 –latex impression of the ventral surface; b2, b3 – ventral surface imprint: rear view, top view; b4 – latex impression of the dorsal surface; Bashkortostan, Shakhtau quarry, location No. 5538/7; Asselsky tier. The scale is 5 mm.

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4. Fig. 3. Lekiskochiton crassus sp. nov., ×2.5, the reconstructed outlines of the shields are shown in thin lines: a – PIN paratype, No. 5538/7-293, shield VI: a1–a3 – latex impression of the dorsal surface: a1 – front view, a2 – right view, a3 – top view; a4, a5 – tomography: a4 – front view, a5 – ventral view; b – holotype PIN, No. 5538/7-294, shield VIII: b1–b4 – latex impression of the dorsal surface: b1 – top view, b2 – right view, b3 – rear view, b4 – left view; b5 – latex impression of the ventral surface; b6–b9 – ventral surface imprint: b6 – top view, b7 – right view, b8 – rear view, b9 – left view; Bashkortostan, Shakhtau quarry, location No. 5538/7; Asselsky tier. The scale is 5 mm.

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5. Fig. 4. Lekiskochiton crassus sp. nov.: a – copy. PIN, No. 5538/10-396, shield VII, ×2.5: a1, a2 – ventral surface imprint: left view, top view; a3 – latex impression of a fragment of the lateral surface, the position of the fragment is shown by arrows in FIG. a2; a4 – latex impression of the ventral surface; a5 – reconstruction of the outline of the flap, view from the ventral side; b – ex. PIN, No. 5538/10-551, shield VIII, ×6: b1–b3 latex impression of a fragment of the dorsal surface: b1 – left view, b2 – rear view, b3 – top view; b4–b6 – ventral surface imprint: b4 – top view, b5 – right view, b6 – rear view; b7 – latex impression of the ventral surface; Bashkortostan, Shakhtau quarry, location No. 5538/10; Sakmarsky tier, Sterlitamak horizon. The scale is 5 mm.

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6. Fig. 5. Numbering of the shields of Lekiskochiton crassus sp. nov., the reconstructed outlines of the shields are shown, ×1.5: a – copies. No. 5538/10-506, shield VI; b – copy. PIN, No. 5538/10-396, shield VII; in – copies. PIN, No. 5538/7-292, shield II; g1–g3 – PIN paratype, No. 5538/7-293: g1 – shield IV, g2 – shield V, g3 – shield VI; d – holotype PIN, No. 5538/7-294, shield VIII.

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7. Fig. 6. Lekiskochiton crassus sp. nov., ex. PIN, No. 5538/10-506, form of preservation of the intermediate shield: a – latex impression of transverse cleavage from the dorsal surface: top view, right view, rear view; ×2.5, scale of 5 mm; b1 – transverse cleavage from the dorsal surface, ×2.5, shows areas of calcite biomorphosis according to the tegmentum, enlarged by Fig. c–e; b2 – transverse cleavage from the ventral surface with calcite biomorphosis according to the tegmentum, × 2.5; c–e – enlarged fragments of calcite biomorphosis according to the tegmentum on the imprint of the dorsal surface, × 20, scale 1 mm: c – a thin sculpture on the edge of the lateral field, translucent through the calcite crust; d – columnar structure on the transverse cleavage of calcite biomorphosis along the tegmentum at the border of the lateral field and the imprint of the articulamentum; d – columnar structure on the longitudinal cleavage of calcite biomorphosis along the tegmentum in the anterior part of the jugal region; e – columnar structure on the transverse cleavage of calcite biomorphosis along the tegmen

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