Enigmatic Listracanthus (Chondrichthyes, incertae sedis) from the Lopingian (Permian) of Hunan Province, China

doi:10.19615/j.cnki.2096-9899.260615

Abstract

Abstract:

The Permo-Triassic mass extinction (PTME) was the most severe biotic crisis of the Phanerozoic and had profound effects on aquatic vertebrates. However, the sparse vertebrate fossil record of the late epoch of Permian has limited further assessment of the ecological impact of the crisis. This study reports the Shaoyang Fauna from central Hunan Province, South China, for which biostratigraphic evidence indicates a late Wuchiapingian age, approximately 5 million years before the PTME. The Shaoyang Fauna includes listracanthids, an enigmatic group represented by chondrichthyan dermal denticles and commonly found in Late Paleozoic marine strata. The new material closely resembles the Early Triassic listracanthids, which are the youngest known record of the group. However, differences in the anterior fulcra justify the establishment of a new species, Listracanthus shaoyangensis sp. nov. We also used micro-X-ray fluorescence (micro-XRF) imaging to investigate elemental distributions on the fossil surfaces and found that specimens of different colors show distinct preservation modes. Together with co-existing osteichthyan fossils (e.g., saurichthyiform fishes), the Shaoyang Fauna provides a snapshot of a marine ecosystem shortly before the PTME and offers new insight into fish diversity prior to the Mesozoic Marine Revolution.

Key words: Listracanthus, Chondrichthyes, PTME, XRF, paleobiogeography

摘要：

二叠-三叠纪大灭绝(PTME)是显生宙最严重的生物危机事件，对水生脊椎动物的演化产生了深远影响。然而，二叠纪晚期化石记录的稀缺限制了我们对该事件生物学效应的进一步研究。报道了产于湖南湘中地区的邵阳动物群，生物地层学证据表明其时代为二叠纪乐平世吴家坪期晚期，约早于PTME 5 myr。邵阳动物群中包含神秘的棘鳞鲨类(Listracanthidae), 它被认为是某种未知软骨鱼的皮齿(dermal denticles), 常见于晚古生代的海相地层。新发现的材料在形态上与早三叠世的棘鳞鲨类十分相似，后者也是该类群已知最晚的化石记录。新材料前缘棘刺的特征支持建立一新种：邵阳棘鳞鲨(Listracanthus shaoyangensis sp. nov.)。此外，化石表面的微区X射线荧光(micro-XRF)成像显示，邵阳产地深色和浅色的围岩具有不同的元素分布，这可能受到了后埋藏改造过程的影响。连同共存的硬骨鱼化石(如龙鱼类), 邵阳动物群提供了PTME前海洋生态系统的记录，同时也让我们对中生代海洋革命(Mesozoic Marine Revolution)之前的鱼类面貌有了更多了解。

关键词: 软骨鱼类，棘鳞鲨类, 二叠-三叠纪大灭绝, 微区X射线荧光成像, 古生物地理学

CLC Number:

Q915.862

FANG Geng-Yu, MU Lin, JI Cheng, LI Hang, YANG Tao, YANG Shuang, YANG Chen-Guang, WU Fei-Xiang. Enigmatic Listracanthus (Chondrichthyes, incertae sedis) from the Lopingian (Permian) of Hunan Province, China. Vertebrata Palasiatica, 2026, 64(4): 333-347.

房庚雨, 牟林, 季承, 李航, 杨涛, 杨爽, 杨晨光, 吴飞翔. 2026, 64(4): 333-347, 湖南二叠纪乐平世棘鳞鲨Listracanthus (软骨鱼类)的发现. 古脊椎动物学报.

Figures/Tables 5

Fig. 1 Geographical settings of the localities that yielded Shaoyang Fauna and associated ammonoids of Longtan Formation in Shaoyang, Hunan Province A. map showing the fossil locality of the Shaoyang Fauna; B. outcrop at Zhoujiawa; C-E. associated ammonoids in lateral view: Otocerataceae (Anderssonoceratidae or Araxoceratidae) (C, D), and Pseudogastrioceras sp. (E). Red star indicates the outcrop that yielded listracanthids, black stars indicate other Shaoyang Fauna outcrops. Scale bars equal 5 mm. Map approved number: 湘S(2012)12

Fig. 2 Specimens and enlarged details of Listracanthus shaoyangensis sp. nov. from the Permian (Lopingian) of Shaoyang, Hunan Province A. holotype, IVPP V34643; B, C. paratypes, V34644, V34645; D-H. enlarged details of the specimens, showing the anterior fulcra (D), posterior comb-like processes (E, F), posterior extension of the base (G), and apex (H). White dashed boxes indicate the positions of the enlargements White solid triangles in D and H indicate fulcra, white open triangles in E-H indicate comb-like processes, blue triangles in E indicate lateral ridges, and white arrowhead in F indicates the basal prominence of the comb-like process. Note that all of these structures are preserved as impressions. Scale bars equal 5 mm

Fig. 3 Comparative specimens of other listracanthid species A-D. Listracanthus hystrix (NHMUK PV P62273), showing the complete specimen (A) and enlarged details of the apex (B), middle shaft (C), and root (D); E-G. death assemblage of Acanthorhachis (formerly Listracanthus wardi), preserved as compressed (A. wardi, NHMUK PV P10004) (E), three dimensions (A. spinatus, NHMUK PV P73205a) (F), and in cross section (A. spinatus, NHMUK PV P73207) (G) White solid triangles indicate fulcra, white open triangles indicate comb-like processes, and white arrows with blue fill indicate the cross sections of denticles Scale bars in A, E, and F equal 1 cm; scale bar in G equals 2 mm

Fig. 4 Micro-XRF elemental maps of Listracanthus shaoyangensis sp. nov. from the Permian (Lopingian) of Shaoyang, Hunan Province From left to right: optical image, and elemental maps of silicon (Si), sulfur (S), potassium (K), calcium (Ca), titanium (Ti), vanadium (V), chromium (Cr), and iron (Fe). Scale bars equal 5 mm

Fig. 5 Paleobiogeographic distribution of listracanthids Reconstructed paleogeographic distribution of fossil localities in the Carboniferous, Permian, Triassic, and distribution of all fossil localities on the modern map The red star indicates the location of the Shaoyang Fauna. NC. North China; SC. South China

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