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New fish assemblages from the Carboniferous deep-water sections of South China and Western Kazakhstan

Published online by Cambridge University Press:  28 August 2025

Alexander O. IvanovOpen the ORCID record for Alexander O. Ivanov[Opens in a new window] and
Keyi HuOpen the ORCID record for Keyi Hu[Opens in a new window]
Alexander O. Ivanov*
Affiliation:
Department of Sedimentary Geology, Institute of Earth Sciences, St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russia
Keyi Hu*
Affiliation:
State Key Laboratory of Critical Earth Material Cycling and Mineral Deposits, School of Earth Sciences and Engineering, Nanjing University , 163 Xianlin Ave., 210023 Nanjing, PR China
*
Corresponding authors: Alexander O. Ivanov and Keyi Hu; Emails: IvanovA-Paleo@yandex.ru; kyhu@nju.edu.cn
Corresponding authors: Alexander O. Ivanov and Keyi Hu; Emails: IvanovA-Paleo@yandex.ru; kyhu@nju.edu.cn
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Abstract

Numerous fish microremains, including diverse chondrichthyans, have been recovered for the first time in the Carboniferous–lower Permian of the Naqing, Narao, and Shanglong deep-water sections from Guizhou Province, South China, as well as in the Serpukhovian–lower Bashkirian of the Sholaksay section from Kazakhstan. The richest assemblage was found in the Bashkirian strata of the three South China sections. These findings are the first reliable record of Pennsylvanian fishes in China. The fish assemblage from the Sholaksay section and the Bashkirian of China closely resemble those from the same interval in the Aksu section, Uzbekistan. All studied fish faunas from these three Asian regions are associated with the Paleotethys. Notably, while Bashkirian chondrichthyan faunas generally exhibit low taxonomical diversity in many regions of the world, the deep-water fish assemblages from South China, Kazakhstan, and Uzbekistan are characterized by high taxonomical diversity. The fish fauna includes widely distributed chondrichthyan taxa; however, Gissarodus occurs only in these three Asian regions.

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Journal of Paleontology , Volume 99 , Issue 4 , July 2025, pp. 958 - 974
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© The Author(s), 2025. Published by Cambridge University Press on behalf of Paleontological Society

Non-technical Summary

Fishes, one of the most diverse taxa in the modern water ecosystem, underwent various morphological evolutions during the Phanerozoic. Cartilaginous and bony fishes are the two major groups of fishes. The microremians (teeth, scales, and spines) were the key to understanding the evolution process of fishes. However, the microremians of cartilaginous and bony fishes of the Carboniferous time are less known compared with other fossil groups of invertebrates, especially in China. Here we report Carboniferous deep-water fish assemblages from South China and Western Kazakhstan for the first time. A high diversity of fish fauna was found from the Bashkirian strata in both areas, while low diversity existed in most of other areas during the Early Pennsylvanian time. These findings will increase our understanding of the Carboniferous fishes.

Introduction

The study of Carboniferous fishes, particularly chondrichthyans, in China remains sparse and is one of the least explored areas in Paleozoic fish research in the region (e.g., Zhu et al., Reference Zhu, Wang and Wang2000; Wang, Reference Wang2006). Only a few Mississippian localities have been reported in China, including the Tournaisian of Guizhou (Wang and Turner, Reference Wang and Turner1995; Ginter and Sun, Reference Ginter and Sun2007) and Guangxi (Ji and Ziegler, Reference Ji and Ziegler1992) provinces, and the Tournaisian–Serpukhovian of Gansu Province (Wang et al., Reference Wang, Jin and Wang2004). However, records of Pennsylvanian fishes in China are extremely rare. The hybodontiform tooth described as Protacrodus orientalis Li, Reference Li1988 was reported from the possible middle Carboniferous of the Huangpu borehole in Jiangsu Province (Li, Reference Li1988). Wang (Reference Wang2006) established the assemblages of fish microremains from the Carboniferous Tournaisian to the Permian Sakmarian in China on the basis of material from Gansu and Inner Mongolia and mentioned several chondrichthyan taxa, including two new species of Bransonella and Denaea from the Bashkirian, Moscovian–Kasimovian, and Gzhelian. However, these microremains were neither described nor illustrated, and subsequent studies adopted or confirmed these findings.

Recently, various fish microremains have been discovered for the first time in the Naqing, Narao, and Shanglong sections in Guizhou Province, South China, represented by deep-water carbonate facies. The age of these fish microremains can be determined by the well-defined conodont biostratigraphic framework established earlier (e.g., Qi et al., Reference Qi, Barrick, Hogancamp, Chen, Hu, Wang and Wang2020; Hu et al., Reference Hu, Wang and Qi2023). A new fish assemblage was recorded also in the upper Serpukhovian–lower Bashkirian of the Sholaksay section, South Urals, Aktobe Region, Western Kazakhstan (Fig. 1.2). This study presents a description of the newly discovered material from the Carboniferous of China and Kazakhstan, providing important insights into the diversity and distribution of Carboniferous fishes in these regions.

Figure 1.

(1) Locations of the studied areas in China (shaded rectangle marked 3) and Kazakhstan (shaded rectangle marked 2). (2) Location map of the Sholaksay section in Kazakhstan: 1. Sholaksay section. (3) Location map of the Naqing, Shanglong and Narao sections in Guizhou, South China: 1. Naqing section; 2. Shanglong section; 3. Narao section. Legend: 1 = city; 2 = section; 3 = railway; 4 = highway; 5 = country boundary; 6 = provincial boundary.

Geological setting

The material from China for this study comes from the Naqing, Narao, and Shanglong sections of Guizhou Province, South China (Fig. 1.3).

The Naqing section (25°15′04′′N, 106°29′07′′E) is a road-cut along the S312 highway, ~45 km southwest of Luodian, ~7 km southwest of Luosu, and ~2 km southwest of the Naqing Village. It is a carbonate succession that is composed of middle- to thin-bedded microcrystalline limestone intercalated with thick-bedded packstone to grainstone and cherts deposited at the platform margin to slope facies, ranging from the Middle Mississippian (upper Viséan) to the lower Permian. Fish microremains were collected from multiple stratigraphic levels, including five samples from the Viséan, two from the Serpukhovian, 11 from the Bashkirian, two from the Moscovian, one from the Kasimovian, four from the Gzhelian, and three from the Asselian (Fig. 2).

Figure 2.

Range chart of the fish microremains in the Naqing section, southern Guizhou, South China; chronostratigraphic subdivision is based on conodont data from Hu et al. (Reference Hu, Qi, Qie and Wang2020, Reference Hu, Qi and Wang2021) and Qi et al. (Reference Qi, Barrick, Hogancamp, Chen, Hu, Wang and Wang2020). Legend: 1 = limestone; 2 = chert. Abbreviations: M = lime mudstone–wackestone; P = packstone; G = grainstone.

The Narao section (25°24′48″N, 106°36′13″E) is exposed along the country road from Fengting to Narao, beside the Lianjiang Riverbank, ~22 km from the Naqing section, and ~15 km from Luodian. It was deposited on the slope of the carbonate platform, composed mainly of thin- to medium-bedded packstone, wackestone, and chert intercalated with thick-bedded grainstone and thin shale. The exposed rocks of the Narao section range from the Middle Mississippian (upper Viséan) to the lower Permian. Fish microremains were recorded in one sample from the Viséan, one from the Serpukhovian, three from the Bashkirian, one from the Moscovian, five from the Gzhelian, and three from the Asselian (Fig. 3).

Figure 3.

Range chart of the fish microremains in the Narao section, southern Guizhou, South China; chronostratigraphic subdivision is based on conodont data from Qi et al. (Reference Qi, Barrick, Hogancamp, Chen, Hu, Wang and Wang2020) and this study; dashed line indicates a boundary is not well defined by detailed conodont study. Legend: 1 = limestone; 2 = chert. Abbreviations: M = lime mudstone–wackestone; P = packstone; G = grainstone.

The Shanglong section (25°20′50′′N, 106°30′07′′E) is ~11 km north of the Naqing section, ~12.5 km southwest of the Narao section, and ~27 km west of Luodian, exposed on the country road from Luosu to Fengting. The lithology of the Shanglong section is composed mainly of thin-bedded lime mudstones, wackestone, and packstone intercalated with massive grainstone, representing platform margin to upper slope environments. The section ranges from the Lower Pennsylvanian (lower Bashkirian) to the lower Permian. Fish microremains of the Shanglong section were collected in nine samples from the Bashkirian, two from the Moscovian, one from the Gzhelian, and one from the Asselian (Fig. 4).

Figure 4.

Range chart of the fish microremains in the Shanglong section, southern Guizhou, South China; chronostratigraphic subdivision is based on conodont data from Hu et al. (Reference Hu, Wang and Qi2023) and this study; dashed line indicates a boundary is not well defined by detailed conodont study. Legend: 1 = limestone; 2 = chert. Abbreviations: M = lime mudstone; W = wackestone; P = packstone; G = grainstone.

The carbonate successions of the three sections were all deposited in deep-water environments. During the Carboniferous, the Narao and Shanglong sections were probably located in slightly shallower settings compared with the Naqing section, suggested by more beds of massive grainstone and a higher abundance of benthic fossils (fusulinids and corals) presented in the former two sections. The Naqing section has been well studied in conodont biostratigraphy, and over 30 Carboniferous zones have been established (e.g., Hu et al., Reference Hu, Qi, Qie and Wang2020). By contrast, detailed conodont biostratigraphy for the Narao and Shanglong sections was focused mainly on the Middle–Upper Pennsylvanian (e.g., Qi et al., Reference Qi, Barrick, Hogancamp, Chen, Hu, Wang and Wang2020; Hu et al., Reference Hu, Wang and Qi2023). Unpublished data, however, define the stage boundaries in the two sections roughly.

Numerous fish microremains have also been found in the upper Serpukhovian–lower Bashkirian of the Sholaksay section (50°15′27.6′′N, 57°50′46′′E), South Urals, Aktobe Region, Western Kazakhstan (Fig. 1.2). This section is located in the Zhaman–Kargaly River Basin, on the right bank of the Sholaksay ravine (Ruzhentsev and Bogoslovskaya, Reference Ruzhentsev and Bogoslovskaya1971). The deposits of the section belong to the Serpukhovian Protvian and Staroutkinskian regional stages, the Gnathodus bollandensis conodont Zone, and the Bashkirian Bogdanovkian Regional Stage, the Declinognathodus noduliferus conodont Zone (Kulagina et al., Reference Kulagina, Rumjanzeva, Pazukhin and Kochetova1992). Fish microremains have been found in 12 samples: nine from the Serpukhovian and three from the Bashkirian (Fig. 5).

Figure 5.

Distribution of fish taxa in the Sholaksay section, Kazakhstan. Modified from Kulagina et al. (Reference Kulagina, Rumjanzeva, Pazukhin and Kochetova1992). Legend: 1 = pelitomorphic and granular limestones; 2 = detrital limestone; 3 = mudstone; 4 = crinoid; 5 = ammonoid; 6 = brachiopod. Abbreviation: R = regional.

The Serpukhovian deposits of the Protvian Regional Stage include light gray limestones, dense, pelithomorphic, fine-grained, and medium-layered, with intercalations of crinoid limestones and brownish clays in the upper part (Ruzhentsev and Bogoslovskaya, Reference Ruzhentsev and Bogoslovskaya1971). The limestones contain rare ammonoid, ostracod, brachiopod, conodont, fish, and algae remains. The thickness of these beds is 5.7 m. The deposits of the Staroutkinskian (or Yuldybaevian) Regional Stage comprise light gray limestones, dense, thin- and medium-layered, fine-grained, pelithomorphic, and granular, with remains of ostracods, trilobites, ammonoids, brachiopods, crinoids, conodonts, and fishes (Kulagina et al., Reference Kulagina, Rumjanzeva, Pazukhin and Kochetova1992). The thickness of these beds is 3.45 m.

The Bashkirian Bogdanovkian Regional Stage is composed of dark-gray, brownish-gray, and gray limestones, thin-layered, fine-grained, dense, with thin layers of black clay shales, mudstones, and detrital limestones with numerous ammonoid shells, some brachiopod, conodont, and fish remains (Ruzhentsev and Bogoslovskaya, Reference Ruzhentsev and Bogoslovskaya1971). Thickness is 2.85 m.

Materials and methods

A total of 317 limestone samples from the Naqing section, 272 from the Narao section, and 178 from the Shanglong section, each weighing ~8–10 kg, were collected throughout the South China sections. These samples were treated with buffered acetic acid and further separated with a solution of lithium heteropolytungstate. Among them, ~95% of the samples produce conodonts. Abundant conodont elements, ~150 per sample on average, have been recovered from those samples. Fish microremains were found from part of the conodont samples (~10%) but as a small component. Selected fish microremains were microphotographed using the scanning electron microscopes Zeiss Gemini SEM 360.

Microremains from the Sholaksay section, Kazakhstan, described here were extracted from conodont residues donated by V.N. Pazukhin and E.I. Kulagina (Institute of Geology, Ufa, Russia). Microremains were microphotographed using the scanning electron microscopes Hitachi S-3400N and Tescan VEGA-II XMU. The internal structure of Gissarodus teeth was reconstructed non-destructively with a NeoScan-80 micro-CT device (Center for X-ray Diffraction Studies, Research Park of St. Petersburg State University, Russia). Micro-CT scanning of the specimens was utilized with an average rotation angle step of 0.2°, with electric parameters of 58 kV and 200 mA, and with an aluminum filter. The virtual cross sections were generated from three-dimensional reconstructions using DataViewer, CTVox, and CTAn software. The transparent mode of skeletal tissues was used for the reconstruction of the system of the vascular canal.

Repositories and institutional abbreviations

The specimens described and illustrated herein are housed in the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (abbreviation NIGP PZ), and in the Palaeontological Museum of the St. Petersburg State University (abbreviation PMSPU).

Systematic paleontology

Class Chondrichthyes Huxley, Reference Huxley1880

Subclass Elasmobranchii Bonaparte, Reference Bonaparte1838

Superorder Cladodontomorphi Ginter, Hampe, and Duffin, Reference Ginter, Hampe, Duffin and Schultze2010

Order Symmoriiformes Zangerl, Reference Zangerl and Schultze1981

Family Falcatidae Zangerl, Reference Zangerl1990

Genus Denaea Pruvost, Reference Pruvost1922

Type species

Denaea fournieri Pruvost, Reference Pruvost1922.

Denaea cf. D. williamsi Ginter and Hansen, Reference Ginter, Hansen and Nowakowski2010

Figures 6.15–6.17, 7.1–7.9

Figure 6.

Chondrichthyan teeth from the Carboniferous of South China: Viséan (29) and Bashkirian (10, 16–18, 20, 23, 24) of the Naqing section; from the Bashkirian (7–9, 11, 12, 21, 22, 28) and Moscovian (30) of the Narao section; and from the Bashkirian (1, 4–6, 13–15, 25, 26, 27), Moscovian (2, 3), and Gzhelian (19) of the Shanglong section. (1–14) Gissarodus flabellatus Ivanov, Reference Ivanov2013: (1) NIGP PZ 203986, sample SL 1.9, occlusal view; (2, 3) NIGP PZ 203987, sample SL 124.6, lingual (2) and occlusal (3) views; (4, 5) NIGP PZ 203988, sample SL 1.9, oblique lingual (4) and occlusal (5) views; (6) NIGP PZ 203989, sample SL 4.2, occlusal view; (7, 8) NIGP PZ 203990, sample NR 104.7, oblique lingual (7) and occlusal (8) views; (9) NIGP PZ 203991, sample NR 102, occlusal view; (10) NIGP PZ 203992, sample NQ 103.5, occlusal view; (11, 12) NIGP PZ 203993, sample NR 102, occlusal (11) and labial (12) views; (13) NIGP PZ 203994, sample SL 1.9, lingual view; (14) NIGP PZ 203995, sample SL 1.9, labial view. (15–17) Denaea cf. D. williamsi Ginter and Hansen, Reference Ginter, Hansen and Nowakowski2010: (15) NIGP PZ 203996, sample SL 4.2, labial view; (16) NIGP PZ 203997, sample NQ 99.8, labial view; (17) NIGP PZ 203998, sample NQ 103.5, occlusal view. (18–20) Denaea sp.: (18) NIGP PZ 203999, sample NQ 103.5, occlusal view; (19) NIGP PZ 204000, sample SL 220.4, occlusal view; (20) NIGP PZ 204001, sample NQ 105.4, labial view. (21) Cladodontomorphi indet., cusp with traces of bioerosion, NIGP PZ 204002, sample NR 102.9, lateral view. (22–25) Stethacanthulus meccaensis (Williams, Reference Williams1985): (22) NIGP PZ 204003, sample NR 102.9, occlusal view; (23) NIGP PZ 204004, sample NQ 96.7, occlusal view; (24) NIGP PZ 204005, sample NQ 96.7, occlusal view; (25) NIGP PZ 204006, sample SL 1.9, labial view. (26, 27) Stethacanthulus decorus (Ivanov, Reference Ivanov1999): (26) NIGP PZ 204007, sample SL 1.9, oblique labial view; (27) NIGP PZ 204008, sample SL 1.9, occlusal view. (28) Stethacanthus sp., NIGP PZ 204009, sample NR 102.9, labial view. (29) Phoebodontiformes indet., NIGP PZ 204010, sample NQ 16.3, labial view. (30) Jalodontiformes indet., cusp, NIGP PZ 204011, sample NR 177.8, labial view. Scale bars = 100 μm.

Figure 7.

Cladodontomorph teeth from the Carboniferous of Sholaksay section, Kazakhstan: from the Serpukhovian (8, 10, 12, 13, 16, 17, 19–25) and Bashkirian (1–7, 9, 11, 14, 15, 18). (1–9) Denaea cf. D. williamsi Ginter and Hansen, Reference Ginter, Hansen and Nowakowski2010: (1, 2) PMSPU 114-1, sample 47, occlusal (1) and oblique labial (2) views; (3) PMSPU 114-2, sample 46i, oblique basal view; (4) PMSPU 114-3, sample 46i, lingual view; (5) PMSPU 114-4, sample 46i, oblique lateral view; (6) PMSPU 114-5, sample 46i, labial view; (7) PMSPU 114-6, sample 46i, occlusal view; (8) PMSPU 114-7, sample 43b, occlusal view; (9) tooth file, PMSPU 114-8, sample 46i, oblique labial view. (10–16) Stethacanthulus meccaensis (Williams, Reference Williams1985): (10) PMSPU 114-9, sample 45a, occlusal view; (11) PMSPU 114-10, sample 47, occlusal view; (12) PMSPU 114-11, sample 44b, occlusal view; (13) PMSPU 114-12, sample 44b, oblique lateral view; (14) PMSPU 114-13, sample 46i, occlusal view; (15) PMSPU 114-14, sample 47, basal view; (16) PMSPU 114-15, sample 44b, labial view. (17–19) Stethacanthulus decorus (Ivanov, Reference Ivanov1999): (17) PMSPU 114-16, sample 46b, occlusal view; (18) PMSPU 114-17, sample 47, oblique lingual view; (19) PMSPU 114-18, sample 46a, occlusal view. (20–23) Squatinactis cf. S. caudispinatus Lund and Zangerl, Reference Lund and Zangerl1974: (20, 21) PMSPU 114-19, sample 45b, occlusal (20) and labial (21) views; (22) PMSPU 114-20, sample 45a, occlusal view; (23) PMSPU 114-21, sample 44b, occlusal view. (24, 25) Cladodontomorphi indet.: (24) PMSPU 114-22, sample 46a, occlusal view; (25) PMSPU 114-23, sample 45a, occlusal view. Scale bars = 100 μm.

Description

The small teeth possess a five-cusped cladodont crown. The central cusp is considerably higher and thicker than lateral ones. The lateral cusps are higher than intermediate cusps. The lateral and intermediate cusps are quite divergent from the central cusp. All cusps are oval in cross section, slightly compressed labiolingually, recurved lingually, sharply pointed, and separated by deep notches. The central cusp is slightly compressed at the base on the labial face, inclined often mesially or distally from the asymmetrical crown. The labial and lingual faces of the cusps bear the distinct cristae. The cristae are slightly curved or wavy or rarely straight, sometimes bifurcate toward the tooth base. Two long cristae merge before the cusp apex and form a lanceolate, inverted “V”-nested structure on the labial face. Other shorter cristae are located in the middle part of the cusp below the lanceolate cristae.

The tooth base is trapezoidal, quite wide, and lingually extended, with convex occlusal and concave basal faces. The apical button is prominent and wide, rectangular or oval in shape, placed at the lingual rim and occupies a considerable part of the occlusal face. The button bears the large foramen of the main vascular canal, sometimes forming the median notch that subdivided the button into two portions. The numerous small foramina surround the button. The distinct labio-basal tubercle is slightly wider than the base of the central cusp.

One tooth file (Fig. 7.9) contains four crowns and fused bases in spiral. Crowns consistently increase in height. The smallest crown bears a low central cusp.

Material

Two teeth from the samples NQ 99.8 and NQ 103.5, Bashkirian of the Naqing section; one tooth from the sample SL 4.2, Bashkirian of the Shanglong section; 19 teeth from the samples 43b, 44b, 44v, 45a, 45b, 46, 46a, and 46b, Serpukhovian, and 92 teeth from the samples 46zh, 47, and 46i, Bashkirian of the Sholaksay section.

Remarks

The teeth described here differ from the teeth of Denaea williamsi from the Norgorod Region, Russia (Savitskiy et al., Reference Savitskiy, Ivanov and Orlov2000) and from Illinois, USA (Ginter and Hansen, Reference Ginter, Hansen and Nowakowski2010) in the wider apical button and labio-basal tubercle, in the rectangular or oval button, in the stronger divergent lateral and intermediate cusps, in the considerable inclination of central cusp, and in the slightly curved, long cristae on the cusp lingual face. The ornamentation on the lingual face in the teeth of D. williamsi consists of one long crista in the middle and several cristae converged at different heights. The teeth of Denaea cf. D. williamsi from Uzbekistan (Ivanov, Reference Ivanov2013) are distinguished from those described here by the narrow apical button and labio-basal tubercle. The teeth described as Stethacanthus gansuensis Wang, Jin, and Wang, Reference Wang, Jin and Wang2004 and Stethacanthus cf. S. altonensis (St. John and Worthen, Reference St. John and Worthen1875) from the Serpukhovian of China (Wang et al., Reference Wang, Jin and Wang2004) are very similar to the teeth from the Sholaksay section but differ in the thicker apical button.

Family Symmoriidae Dean, Reference Dean1909

Genus Stethacanthulus Zangerl, Reference Zangerl1990

Type species

Denaea meccaensis Williams, Reference Williams1985.

Remarks

Stethacanthulus longipeniculus Zangerl, Reference Zangerl1990 was originally erected as type species of the genus Stethacanthulus (Zangerl, Reference Zangerl1990). Later this species was regarded as a junior synonym of Denaea meccaensis (Maisey, Reference Maisey2007).

Stethacanthulus decorus (Ivanov, Reference Ivanov1999)

Figures 6.26, 6.27, 7.17–7.19

Holotype

PMSPU 6-74, tooth, Sterlitamak Regional Stage, Sakmarian, Cisuralian, Permian; road cutting on the Ufa–Chelyabinsk road, South Urals, Russia (Ivanov, Reference Ivanov1999, pl. 8, fig. 2).

Occurrence

Carboniferous, Viséan–Permian, Roadian; Russia (Nearpolar and South Urals), Kazakhstan, Uzbekistan, China, USA (Texas).

Description

These small teeth have a cladodont crown with five to seven cusps. The central cusp is high and wide, slightly displaced labially. The lateral cusps in the five-cusped crown and outer intermediate cusps in the seven-cusped cladodont crown are considerably higher than the inner intermediate cusps. All cusps are round in cross sections, inclined lingually, sigmoidal incurved, with tiny lateral carina, ornamented with distinct cristae, which formed the lanceolate structure on the labial face. The tooth base is trapezoidal, considerably extended lingually, bears a median triangular depression on the occlusal face and the transversal prominence on the basal side. This large foramen of the main vascular canal opens in the deeper part of occlusal depression.

Material

Two teeth from the sample SL 1.9, Bashkirian of the Shanglong section; 53 teeth from the samples 43b, 44b, 44v, 45a, 45b, 46a, and 46b, Serpukhovian, and 46 teeth from the samples 46zh, 47, and 46i, Bashkirian of the Sholaksay section.

Remarks

Three morphotypes of Stethacanthulus teeth are known (Ivanov et al., Reference Ivanov, Bakaev, Nestell and Nestell2021b). The first morphotype possesses the narrow crown consisting of three to five smooth and thin cusps, the spoon-like base with narrow labial and wide lingual parts and with divergent or parallel lateral edges. The second morphotype is characterized by a crown with three to five ornamented cusps and base rounded or rectangular in shape, with almost the same width as the crown, and with slightly divergent lateral edges. The third morphotype has the wide crown with five to seven ornamented cusps, the trapezoid base with wide labial and narrow lingual parts, and with concave lateral edges considerably divergent to the center of the lingual edge. The labial surface of cusps in the second and third morphotypes bears the distinct lanceolate ornamentation. The teeth of Stethacanthulus decorus described here belong to third morphotype.

Stethacanthulus meccaensis (Williams, Reference Williams1985)

Figures 6.22–6.25, 7.10–7.16

Holotype

PF 6767-LQXR 37, Staunton Formation, Pennsylvanian, Carboniferous; Logan Quarry, Indiana, USA (Williams, Reference Williams1985, text-fig. 8).

Occurrence

Carboniferous, Serpukhovian–Permian, Capitanian; Kazakhstan, Uzbekistan, China, USA (Indiana, Iowa, Oklahoma, and Texas).

Description

These small teeth possess the cladodont crown with five to seven cusps. The cusps are smooth or ornamented with straight parallel cristae on both labial and lingual faces. The tooth base bears a shallow median triangular depression on the occlusal face and the poorly developed transversal prominence on the basal side.

Material

Two teeth from the sample NQ 96.7, Bashkirian of the Naqing section; one tooth from the sample NR 102.9, Bashkirian of the Narao section; one tooth from the sample SL 1.9, Bashkirian of the Shanglong section; 89 teeth from the samples 44b, 44v, 45a, 45b, 46, 46a, and 46b, Serpukhovian, and 81 teeth from the samples 46zh, 47, and 46i, Bashkirian of the Sholaksay section.

Remarks

The teeth described here are represented by all three morphotypes known for Stethacanthulus teeth. The teeth of the first morphotype have five cusps in the crown (Fig. 7.10). The teeth of the second morphotype possess a six- or seven-cusped crown with smooth (Fig. 7.14) or ornamented (Fig. 7.12, 7.13) cusps. The tooth base of the third tooth morphotype is trapezoidal with an extended lingual part (Fig. 7.11, 7.15, 7.16).

Order Squatinactiformes Zangerl, Reference Zangerl and Schultze1981

Family Squatinactidae Cappetta, Duffin, and Zidek, Reference Cappetta, Duffin, Zidek and Benton1993

Genus Squatinactis Lund and Zangerl, Reference Lund and Zangerl1974

Type species

Squatinactis caudispinatus Lund and Zangerl, Reference Lund and Zangerl1974.

Squatinactis cf. S. caudispinatus Lund and Zangerl, Reference Lund and Zangerl1974

Figure 7.20–7.23

Description

The small asymmetrical teeth possess a cladodont multicuspid crown consisting of 8 to 12 cusps and cusplets. The inner intermediate cusps are smaller than the outer intermediate and lateral cusps. The cusps and cusplets are smooth, acuminated, quite thin, inclined mesially or distally, with slightly flattened labial and convex lingual faces, with asymmetrical cross section at the base, and bear the lateral carina. The lingual face is covered with a few delicate, straight cristae. Some cusplets are displaced labially.

The tooth base is considerably wide, triangular in shape, with a rather short lingual part. Two apical buttons are indistinct and widely spaced on the occlusal face. The narrow median depression on the labial face is developed under the central cusp and flanked by two low labio-basal projections.

Material

Three teeth from the samples 44b, 45a, 45b, Serpukhovian of the Sholaksay section, Kazakhstan.

Remarks

The teeth of Squatinactis caudispinatus differ from those described here in the higher central cusp, the ornamented labial face of the cusp and cusplets, the wider labial depression, and the more prominent apical buttons and labio-basal projections (Ivanov, Reference Ivanov, Strogen, Somerville and Jones1996, fig. 5, labeled as Symmorium sp.; Ginter et al., Reference Ginter, Hampe, Duffin and Schultze2010). The teeth of Squatinactis multicuspidatus Ivanov in Ivanov et al., Reference Ivanov, Alekseev and Nikolaeva2024 are distinguished from the teeth from the Sholaksay section by the presence of labial accessory cusplets, the large number of cusps and cusplets in the multicuspid crown, the wider apical buttons closely placed, and the wider labial depression (Ivanov et al., Reference Ivanov, Alekseev and Nikolaeva2024). The teeth of Squatinactis glabrum (Ginter, Reference Ginter1999) differ from those described here in the lower number of cusps and cusplets, the more extended lingual part of the tooth base, the quite small apical buttons widely spaced, the deeper labial depression, and the narrow labio-basal projection (Ginter, Reference Ginter1999, pl. 4, figs. 6–11, described as “Symmorium” glabrum; Ginter et al., Reference Ginter, Hairapetian and Klug2002, pl. 9, pl. 11, fig. D, labeled as “Symmorium” glabrum).

The tooth described as Denaea sp. from the Serpukhovian of the Aksu section (Ivanov Reference Ivanov2013; Fig. 2F) is very similar to the teeth from the Sholaksay section; it possesses seven cusps and cusplets in the slightly asymmetrical crown and the triangular tooth base with narrow and wide median depression on the labial face, and it should be attributed also to Squatinactis cf. S. caudispinatus.

Cohort Euselachii Hay, Reference Hay1902

Order and family incertae sedis

Genus Gissarodus Ivanov, Reference Ivanov2013

Type species

Gissarodus flabellatus Ivanov, Reference Ivanov2013.

Gissarodus flabellatus Ivanov, Reference Ivanov2013

Figures 6.1–6.14, 8

Figure 8.

Teeth of Gissarodus flabellatus Ivanov, Reference Ivanov2013 from the Serpukhovian (1–3, 6–16) and Bashkirian (4, 5) of Sholaksay section, Kazakhstan: (1) PMSPU 114-24, sample 45b, occlusal view; (2) PMSPU 114-25, sample 43b, labial view; (3) PMSPU 114-26, sample 43b, occlusal view; (4) PMSPU 114-27, sample 47, oblique basal view; (5) PMSPU 114-28, sample 46i, occlusal view; (6) PMSPU 114-29, sample 43b, oblique occlusal view; (7) PMSPU 114-30, sample 46a, oblique lingual view; (8) PMSPU 114-31, sample 43b, labial view; (9) PMSPU 114-32, sample 44v, basal view; (10) PMSPU 114-33, sample 44v, lingual view; (11–16) PMSPU 114-34, sample 43b, microtomographic images: (11) oblique lateral view, (12) labial view, (13, 15) sagittal virtual sections in opaque (13) and transparent (15) models, (14) transversal virtual section in transparent model, (16) frontal virtual section of tooth base in transparent model. Abbreviations: ac = ascending vascular canal; ccp = central cusp; hc = horizontal vascular canal; icp = inner intermediate cusp; ict = intermediate cusplet; lc = longitudinal vascular canal; lcp = lateral cusp; lct = lateral cusplet; ocp = outer intermediate cusp. Scale bars = 100 μm.

Holotype

PMSPU 66-21, tooth, Khodzhir–Bulak Formation, Bashkirian, Pennsylvanian, Carboniferous; Aksu section 1, Gissar Mountains, Uzbekistan (Ivanov, Reference Ivanov2013, fig. 5A–C).

Occurrence

Carboniferous, Serpukhovian–Moscovian; Kazakhstan, Uzbekistan, China.

Description

These small teeth are elongate mesiodistally, have a multicuspid crown and short base. The crown is flattened labiolingually, inclined lingually, commonly symmetrical or rarely slightly asymmetrical, includes from 5 to 11 cusps and cusplets. The cusps are triangular, separated from each other by deep notches. The central cusp is considerably wider than the other cusps. The lateral cusps in the five-cusped crown are the same height as or higher than the central cusp and considerably larger than the intermediate cusps. The outer intermediate cusps in the crown with more than seven cusps are narrower but sometimes higher than the central cusp and always larger than the inner intermediate and lateral cusps. The inner intermediate and lateral cusps are often equal in size. The intermediate cusplets are presented irregularly, between inner and outer intermediate cusps (Fig. 8.6), or between central and inner intermediate cusps (Fig. 8.7), or on one side of the central cusp (Fig. 6.7, 6.8). The lateral cusplets are located symmetrically on both mesial and distal parts of the crown. The cusps in the multicuspid crown diverge from the crown center, forming a fan-like structure. A lateral carina is distinct and separates the labial and lingual cusp faces. The labial ornamentation of the cusps includes two long cristae forming a lanceolate, inverted “V”-nested structure and short cristae placed below this structure. The small cusps and cusplets are covered by only short cristae. The lingual face of the large cusps bears the delicate cristae not reaching the cusp apex.

The tooth base is elongated oval to rectangular in shape, lingually extended, arched. The base occlusal surface is convex, with occlusal thickening and longitudinal groove at the crown/base boundary. The shallow labial depression is sometimes presented beneath the central cusp. The labio-basal projection is short and wide, extended along the labial margin. The basal face of the base is concave, with a narrow depression separating the projection from the other surface.

The lingual rim in the middle part is perforated by one or two larger foramina of the vascular canal. Several large foramina open centrally on the basal surface of the base. The system of vascular canals is simple and consists of the longitudinal, horizontal, and ascending canals (Fig. 8.12–8.16). One or two parallel horizontal canals run across the tooth base. The very short ascending canals penetrate from the basal surface of the base to the longitudinal canal. The longitudinal canal connects the horizontal and ascending canals.

Material

There are 28 teeth from the samples NQ 103.5, NQ 105.4, NQ 108.4, NQ 118.5, and NQ 128, Bashkirian of the Naqing section; one tooth from the sample NR 51.5, Serpukhovian, nine teeth from the samples NR 102, NR 102.9, and NR 104.7, Bashkirian of the Narao section; 30 teeth from the samples SL 1.9, SL 4.2, and SL 32.3, Bashkirian, and one tooth from the sample SL 124.6, Moscovian of the Shanglong section; 178 teeth from the samples 43, 44b, 44v, 45a, 45b, 46a, and 46b, Serpukhovian and 46 teeth from the samples 46zh, 47, and 46i, Bashkirian of the Sholaksay section.

Remarks

The teeth described here are represented by all three morphotypes known for Stethacanthulus teeth. The teeth of the first morphotype have five cusps in the crown (Fig. 8.10). The teeth of the second morphotype possess a six- or seven-cusped crown with smooth (Fig. 7.14) or ornamented (Fig. 7.12, 7.13) cusps. The tooth base of the third tooth morphotype is trapezoidal with an extended lingual part (Fig. 7.11, 7.15, 7.16).

The described teeth vary in symmetry of the crown, number of the cusps and cusplets, height and width of the cusps, cusp curvature and inclination, shape and curvature degree of the base, and length and width of the labio-basal projection.

Two teeth with separated crown and fused bases (Fig. 8.1) occur in the Serpukhovian of the Sholaksay section. Such tooth file was reported earlier from the Aksu section of Uzbekistan (Ivanov, Reference Ivanov2013, fig. 5O). This file includes three tricuspid crowns and partly fused bases. The collection of Gissarodus teeth from China and Kazakhstan includes several pathological specimens with strongly asymmetrical crowns and considerably arched bases (Figs. 6.14, 8.10).

Other chondrichthyan microremains

One tooth fragment of Phoebodontiformes (Fig. 6.29) from the Viséan of Naqing section possesses the tricuspid phoebodont crown with large lateral and low central smooth cusps. This fragment resembles the Thrinacodus teeth with symmetrical crown (Ginter et al., Reference Ginter, Hampe, Duffin and Schultze2010).

One incomplete cladodont tooth from the Bashkirian of the Narao section (Fig. 6.28) belongs to Stethacanthus sp. The tooth possesses a crown with large central cusps. The outer and inner intermediate cusps are higher than the lateral one. The cusps are covered by a few widely spaced, straight cristae. The tooth base bears a wide apical button and labio-basal projection. This tooth is small compared with the typical teeth of Stethacanthus (Ginter et al., Reference Ginter, Hampe, Duffin and Schultze2010), which usually possess a very high central cusp with numerous closely spaced cristae.

Five incomplete teeth of Denaea sp. occur in the Viséan–Gzhelian of the Naqing section, and three teeth occur in the Bashkirian–Asselian of the Shanglong section. These incomplete and poorly preserved teeth have three to five cusps ornamented with straight cristae (Fig. 6.18–6.20).

Two teeth of Cladodontomorphi (Fig. 7.24, 7.25) have been found in the Serpukhovian of the Sholaksay section. They possess the asymmetrical cladodont crown with seven cusps. The cusps are smooth, are rounded in cross section, consistently increase in height, and bear the distinct lateral carina. The tooth base is horseshoe-shaped, has a short lingual part and wide labial depression. These teeth are distinguished from all known cladodont teeth. Several cusps (Fig. 6.21) and tooth fragments from the Carboniferous of China were determined as Cladodontomorphi indet.

The isolated cusps of Jalodontiformes indet. (Fig. 6.30) from the Bashkirian–Asselian of the Naqing section and the Moscovian of the Narao and Shanglong sections are wide, flattened labiolingually, and bear the distinct lanceolate cristae on the labial side. These cusps are very similar to the cusps in the Adamantina teeth (Ivanov et al., Reference Ivanov, DUFFIN and Richter2021a).

Some morphotypes of symmoriiform denticles occur in the Carboniferous of China (Fig. 9.1, 9.2) and Kazakhstan (Fig. 10.1–10.3). The monocuspid denticles with spine-like crown (Fig. 10.1) belong to denticles from the cranial cap or spine-brush complex of symmoriiforms such as Stethacanthus (Coates and Sequeira, Reference Coates and Sequeira2001), Orestiacanthus (Lund, Reference Lund1984), Falcatus (Lund, Reference Lund1985), and Damocles (Lund, Reference Lund1986). The multicuspid denticles include the buccopharyngeal denticles of “Stemmatias”-type (Figs. 9.2, 10.2), the denticles with narrow, tricuspid crown (Fig. 9.1), and the denticles with wide and flat base (Fig. 10.3). The buccopharyngeal denticles bear a single- or double-rowed crown with recurved cusps consecutively overlapping each other and increasing in length posteriorly. The denticles with a tricuspid crown have a large central and two small lateral cusps. Such denticles were described in Stethacanthulus meccaensis (Williams, Reference Williams1985, text-fig. 7). The denticles with a flat base possess the triangular cusps of different height, inclined posteriorly, possessing distinct lateral carina and a few short cristae.

Figure 9.

Fish microremains from the Carboniferous–lower Permian of South China: from the Viséan (11), Serpukhovian (6), Bashkirian (9), and Gzhelian (1, 5) of the Naqing section; from the Gzhelian (3, 4, 7) and Asselian (10) of the Narao section; and from the Moscovian (8) and Gzhelian (2) of the Shanglong section. (1, 2) Symmoriiform denticles: (1) NIGP PZ 204012, sample NR 238.5, crown view; (2) NIGP PZ 204013, sample SL 220.4, lateral view. (3, 4) Hybodontid type of chondrichthyan scales: (3) NIGP PZ 204014, sample NR 269.4, crown view; (4) NIGP PZ 204015, sample NR 269.4, crown view. (5–8) Euselachian type of chondrichthyan scales: (5) NIGP PZ 204016, sample NQ 231.7, crown view; (6) NIGP PZ 204017, sample NQ 39.5, crown view; (7) NIGP PZ 204018, sample NR 255.3, basal view; (8) NIGP PZ 204019, sample SL 128.4, lateral view. (9) Actinopterygian tooth, NIGP PZ 204020, sample NQ 108.4, lateral view. (10, 11) Actinopterygian scales: (10) NIGP PZ 204021, sample NR 278.8, crown view; (11) NIGP PZ 204022, sample NQ 3.9, crown view. Scale bars = 100 μm.

Figure 10.

Fish microremains from the Serpukhovian (3–6) and Bashkirian (1, 2, 7) of Sholaksay section, Kazakhstan. (1–3) Symmoriiform monocuspid (1) and multicuspid (2, 3) denticles: (1) PMSPU 114-35, sample 47, lateral view; (2) PMSPU 114-36, sample 46i, oblique anterior view; (3) PMSPU 114-37, sample 45b, oblique crown view. Chondrichthyan scales: (4) euselachian type, PMSPU 114-38, crown view; (5, 6) hybodontid type: (5) PMSPU 114-39, oblique lateral view, (6) PMSPU 114-40, crown view. (7) Acanthodiform scale, PMSPU 114-41, oblique crown view. Scale bars = 100 μm.

The microremains collection from the Carboniferous of China and Kazakhstan includes the chondrichthyan scales of hybodontid and euselachian types. The various scales of hybodontid type (Figs. 9.3, 9.4, 10.5, 10.6) possess the high or low conical crown, inclined posteriorly, and the base with undulated edges. The crown bears one to three serrated ridges. The scales of euselachian type (Figs. 9.5–9.8, 10.4) have a flat, rhomboid crown, narrow neck, and small base. The crown bears one long or four short ridges.

Other fish microremains

The rare microremains of other fishes are represented by acanthodian isolated scales and actinopterygian teeth and scales. The acanthodian scales (Figs. 10.7) belong to acanthodiforms and possess the flat, smooth, rhomboid crown, well-developed neck, and prominent, hemispherical base. The actinopterygian teeth (Figs. 9.9) are high conical, round in cross section, with short acrodin cap. The rhomboidal flank scales of actinopterygians bear a very narrow overlapping area and the elongate ganoine ridges (Figs. 9.10) or ganoine-covered field with short ridges (Figs. 9.11).

Discussion

Distribution and occurrence of fish taxa

Denaea williamsi is known from the Viséan–Serpukhovian, Carboniferous: the Viséan of Poland and Novgorod Region, Russia; the Serpukhovian of Arizona and Illinois, USA, and the Upper Mississippian of Scotland (Ivanov et al., Reference Ivanov, Alekseev and Nikolaeva2024). Denaea cf. D. williamsi, apart from the upper Serpukhovian–lower Bashkirian of Kazakhstan and the Bashkirian of China, occurs in the upper Serpukhovian–lower Bashkirian of Uzbekistan (Ivanov, Reference Ivanov2013).

Stethacanthulus decorus, in addition to the upper Serpukhovian–lower Bashkirian of Kazakhstan and the Bashkirian of China, has been found in the Viséan–Serpukhovian of the South Urals (Ivanov et al., Reference Ivanov, Alekseev and Nikolaeva2024); the Serpukhovian of the Nearpolar Urals, Russia; the Serpukhovian–Bashkirian of the Gissar Mountains, Uzbekistan; the Asselian–Kungurian, Permian of the Middle and South Urals, Russia; and the Roadian of Texas, USA (Ivanov et al., Reference Ivanov, Bakaev, Nestell and Nestell2021b).

The widely distributed species Stethacanthulus meccaensis, aside from its presence in the upper Serpukhovian–lower Bashkirian of Kazakhstan and the Bashkirian of China, has been recorded in the Serpukhovian–Bashkirian of the Gissar Mountains, Uzbekistan; the Middle Pennsylvanian (Moscovian) of Indiana, Iowa, and Oklahoma, USA; and the Kungurian–Capitanian, Permian of the Apache and Guadalupe Mountains, Texas, USA (Ivanov et al., Reference Ivanov, Nestell, Nestell and Bell2020). The occurrences of S. meccaensis in the upper Serpukhovian of the Sholaksay and Aksu sections represent the oldest known record of this species in the world.

Squatinactis caudispinatus has been reported from various localities and time intervals, including the Famennian of France (Riemann et al., Reference Riemann, Schülke and Thies2002, table 5, figs. 10, 11, 15, 18, labelled as Symmorium sp.); the Famennian–Tournaisian of the South Urals (Ivanov, Reference Ivanov, Strogen, Somerville and Jones1996, fig. 5, described as Symmorium sp.); the Tournaisian of Illinois, USA (Ginter et al., Reference Ginter, Hampe, Duffin and Schultze2010) and France (Derycke et al., Reference Derycke, Blieck and Turner1995, pl. 3, fig. D, pl. 4, fig. B, C, labelled as Symmorium sp.); the Viséan of England (Ginter et al., Reference Ginter, Duffin, Dean and Korn2015, fig. 8B); and the Serpukhovian of Montana, USA (Lund and Zangerl, Reference Lund and Zangerl1974). Squatinactis cf. S. caudispinatus occurs in the Serpukhovian of Uzbekistan (Ivanov, Reference Ivanov2013, fig. 2F, described as Denaea sp.) and Kazakhstan. Species of Squatinactis are known exclusively from the Famennian and Mississippian.

Gissarodus flabellatus, initially described from the upper Serpukhovian–lower Bashkirian of the Aksu section, Gissar Mountains, Uzbekistan (Ivanov, Reference Ivanov2013), has now also been discovered in the Serpukhovian–Bashkirian of Kazakhstan and the Serpukhovian–Moscovian of China (Fig. 11).

Figure 11.

Comparative distribution of three chondrichthyan species: Gissarodus flabellatus, Denaea williamsi, Squatinactis caudispinatus. Abbreviations: NQ = Naqing section; NR = Narao section; SL = Shanglong section.

Fish assemblages

Fish microremains in the Naqing section occur in the Viséan, Carboniferous–Asselian, Permian interval (Fig. 2). The Viséan assemblage is represented by chondrichthyan teeth of symmoriiforms Denaea sp. and Stethacanthulus sp., a phoebodontid tooth fragment, symmoriiform denticles, and an actinopterygian tooth and scale. Rare remains from the Serpukhovian include the undetermined chondrichthyan denticles and actinopterygians tooth. The diverse Bashkirian assemblage contains teeth of symmoriiforms Stethacanthulus meccaensis, Denaea cf. D. williamsi and D. sp., Cladodontomorphi indet. and euselachians Gissarodus flabellatus and Gissarodus sp., isolated cusps of Jalodontiformes indet., symmoriiform denticles, chondrichthyan scales of hybodontid type, and actinopterygian teeth and scales. The jalodontiform isolated cusps and chondrichthyan scales of euselachian type were found in the Moscovian deposits. Rare fish remains from the Kasimovian include fragments of cladodontomorph teeth and actinopterygian teeth. The assemblage from the Gzhelian contains the tooth of symmoriiform Denaea sp., symmoriiform denticles, chondrichthyan scales of hybodontid and euselachian types, and actinopterygian teeth. Fish remains from the Asselian are represented by isolated jalodontiform cusps, chondrichthyan scales of hybodontid and euselachian types, and chondrichthyan denticles.

Fish microremains from the Narao section were recorded in the Viséan–Gzhelian interval (Fig. 3). The single actinopterygians tooth was collected from the Viséan. The tooth of Gissarodus flabellatus occurs in the Serpukhovian. The diverse assemblage from the Bashkirian includes the teeth of symmoriiforms Stethacanthus sp. and Stethacanthulus meccaensis and euselachian Gissarodus flabellatus, Cladodontomorphi indet. and euselachian Gissarodus flabellatus, scales of euselachian types, symmoriiform denticles, and an actinopterygians tooth. The isolated cusp of Jalodontiformes indet. has been found in the Moscovian. The Gzhelian assemblage contains the scales of euselachian types, a symmoriiform denticle, and actinopterygian teeth and scales. Fish remains from the Asselian include the tooth of Gissarodus sp., chondrichthyan scales of hybodontid and euselachian types, and actinopterygian teeth and scales.

Fish microremains from the Shanglong section were discovered from the Bashkirian, Moscovian, Gzhelian, and Asselian (Fig. 4). The Bashkirian assemblage contains the teeth of symmoriiforms Denaea cf. D. williamsi, D. sp., Stethacanthulus decorus, S. meccaensis, euselachian Gissarodus flabellatus, scales and denticles of undetermined chondrichthyans, and actinopterygian teeth. Microremains from the Moscovian include the tooth of Gissarodus flabellatus, a jalodontiform isolated cusp, scales of hybodontid and euselachian types, and an actinopterygian tooth. The teeth of Gissarodus sp. occur in the Gzhelian. The Asselian assemblage includes the teeth of symmoriiform Denaea sp., Cladodontomorphi indet., a symmoriiform denticle, a scale of euselachian type, and an actinopterygian tooth.

Numerous fish microremains occur in the Serpukhovian–Bashkirian interval of the Sholaksay section of Kazakhstan (Fig. 5). The assemblage from the Serpukhovian includes the chondrichthyan teeth of symmoriiforms Stethacanthulus decorus, S. meccaensis, Denaea cf. D. williamsi, sqatinactiform Squatinactis cf. S. caudispinatus, euselachian Gissarodus flabellatus, and Cladodontomorphi indet., a symmoriiform denticle, scales of hybodontid and euselachian types, and actinopterygian teeth. The Bashkirian assemblage contains the teeth of symmoriiforms Stethacanthulus decorus, S. meccaensis, and Denaea cf. D. williamsi and euselachian Gissarodus flabellatus, a symmoriiform denticle, and acanthodiform scales.

The assemblage from the Sholaksay section is remarkably similar to that of the Serpukhovian–Bashkirian interval in the Aksu sections, Gissar Mountains, Uzbekistan. The Aksu assemblage contains the symmoriiforms Denaea cf. D. williamsi, Stethacanthulus decorus, and S. meccaensis, a euselachian Gissarodus flabellatus, and a sqatinactiform Squatinactis cf. S. caudispinatus described as Denaea sp. (Ivanov, Reference Ivanov2013). The co-occurrence of Stethacanthulus decorus and S. meccaensis in the upper Serpukhovian–lower Bashkirian has been documented only in the Aksu and Sholaksay sections.

The most taxonomically diverse Bashkirian chondrichthyans of three South China sections closely resemble those from the upper Serpukhovian–lower Bashkirian of Kazakhstan and Uzbekistan (Fig. 11). The teeth of euselachian Gissarodus flabellatus are predominant among other fish remains in the assemblages from the Serpukhovian-Bashkirian of Kazakhstan and Uzbekistan and from the Bashkirian of China.

Conclusions

The fish assemblages included the diverse symmoriiform and euselachian chondrichthyans, and rare actinopterygians have been found for the first time in the deep-water Carboniferous deposits of three sections of South China. The richest assemblage occurs in the Bashkirian. Fish microremains from the more deep-water Naqing section are more abundant and taxonomically diverse than these from the Narao and Shanglong sections located in slightly shallower settings. These microremains are present in the numerous samples from the Viséan to the Asselian. These findings are the first reliable record of Pennsylvanian fishes in China. The Carboniferous fish microremains in China are less studied than those from other regions of the world, and these discoveries significantly improve our understanding of the distribution and diversity of Paleozoic chondrichthyans.

For the first time, an assemblage of diverse fishes with numerous microremains is also reported from the upper Serpukhovian–lower Bashkirian of the Sholaksay section, Kazakhstan. The fish assemblage from the Sholaksay section closely resembles the assemblage from the same interval of the Aksu section, Gissar Mountains, Uzbekistan, sharing similar taxa Denaea cf. D. williamsi, Stethacanthulus decorus, S. meccaensis, Squatinactis cf. S. caudispinatus, and Gissarodus flabellatus. In both assemblages, the euselachian Gissarodus is the predominant taxon. Sections with diverse fish remains from the Serpukhovian–Bashkirian interval are extremely rare worldwide, making these findings significant for understanding faunal exchange in the Mississippian–Pennsylvanian boundary time interval.

The Gissarodus assemblage from more deep-water Bashkirian deposits of South China differs from those of the Sholaksay and Aksu sections. It contains fewer fish remains and fewer taxa, with abundant teeth of single euselachian Gissarodus and scarce remains of taxonomically diverse symmoriiforms. The studied fish faunas from these three Asian regions are all located in the Paleotethys area. Interestingly, Gissarodus is not known outside of this area.

The Bashkirian chondrichthyan fauna is characterized by low taxonomical diversity compared with faunas from other Carboniferous stages in many regions of the world (Feichtinger et al., Reference Feichtinger, Ivanov, Winkler, Dojen, Kindlimann, Kriwet, Pfaff, Schraut and Stumpf2021; Schnetz et al., Reference Schnetz, Dunne, Feichtinger, Butler, Coates and Sansom2024). However, the deep-water fish assemblages from South China, Kazakhstan, and Uzbekistan show a high taxonomical diversity and contain widely distributed chondrichthyan taxa. Notably, Gissarodus is unique to these three Asian regions, emphasizing its paleobiogeographic significance.

Acknowledgments

We are grateful to V.N. Pazukhin and E.I. Kulagina (Institute of Geology, Ufa, Russia) for providing specimens from the Sholaksay section and useful stratigraphic information. We also thank N.S. Vlasenko (Research Park, St. Petersburg State University, St. Petersburg, Russia), R.A. Rakitov (Borissiak Paleontological Institute of the Russian Academy of Sciences, Moscow, Russia), and L. Zhang (Nanjing University) for assistance with SEM imaging, as well as S.P. Nilov (Institute of the Earth Sciences, St. Petersburg State University, St. Petersburg) for preparing the microtomographic sections and reconstruction, and an anonymous reviewer for useful comments. The research was performed at the Center for Geo-Environmental Research and Modeling (GEOMODEL), the Center for X-ray Diffraction Studies, and the Centre for Microscopy and Microanalysis of Research Park of St. Petersburg State University.

This paper has been supported by the National Natural Science Foundation of China (42172002). A.O.I. acknowledges the Saint-Petersburg State University for a research project 124032000029-9.

Competing interests

The authors declare none.

Footnotes

Handling Editor: Kerin Claeson

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Figure 0

Figure 1.(1) Locations of the studied areas in China (shaded rectangle marked 3) and Kazakhstan (shaded rectangle marked 2). (2) Location map of the Sholaksay section in Kazakhstan: 1. Sholaksay section. (3) Location map of the Naqing, Shanglong and Narao sections in Guizhou, South China: 1. Naqing section; 2. Shanglong section; 3. Narao section. Legend: 1 = city; 2 = section; 3 = railway; 4 = highway; 5 = country boundary; 6 = provincial boundary.

Figure 1

Figure 2.Range chart of the fish microremains in the Naqing section, southern Guizhou, South China; chronostratigraphic subdivision is based on conodont data from Hu et al. (2020, 2021) and Qi et al. (2020). Legend: 1 = limestone; 2 = chert. Abbreviations: M = lime mudstone–wackestone; P = packstone; G = grainstone.

Figure 2

Figure 3.Range chart of the fish microremains in the Narao section, southern Guizhou, South China; chronostratigraphic subdivision is based on conodont data from Qi et al. (2020) and this study; dashed line indicates a boundary is not well defined by detailed conodont study. Legend: 1 = limestone; 2 = chert. Abbreviations: M = lime mudstone–wackestone; P = packstone; G = grainstone.

Figure 3

Figure 4.Range chart of the fish microremains in the Shanglong section, southern Guizhou, South China; chronostratigraphic subdivision is based on conodont data from Hu et al. (2023) and this study; dashed line indicates a boundary is not well defined by detailed conodont study. Legend: 1 = limestone; 2 = chert. Abbreviations: M = lime mudstone; W = wackestone; P = packstone; G = grainstone.

Figure 4

Figure 5.Distribution of fish taxa in the Sholaksay section, Kazakhstan. Modified from Kulagina et al. (1992). Legend: 1 = pelitomorphic and granular limestones; 2 = detrital limestone; 3 = mudstone; 4 = crinoid; 5 = ammonoid; 6 = brachiopod. Abbreviation: R = regional.

Figure 5

Figure 6.Chondrichthyan teeth from the Carboniferous of South China: Viséan (29) and Bashkirian (10, 16–18, 20, 23, 24) of the Naqing section; from the Bashkirian (7–9, 11, 12, 21, 22, 28) and Moscovian (30) of the Narao section; and from the Bashkirian (1, 4–6, 13–15, 25, 26, 27), Moscovian (2, 3), and Gzhelian (19) of the Shanglong section. (1–14) Gissarodus flabellatus Ivanov, 2013: (1) NIGP PZ 203986, sample SL 1.9, occlusal view; (2, 3) NIGP PZ 203987, sample SL 124.6, lingual (2) and occlusal (3) views; (4, 5) NIGP PZ 203988, sample SL 1.9, oblique lingual (4) and occlusal (5) views; (6) NIGP PZ 203989, sample SL 4.2, occlusal view; (7, 8) NIGP PZ 203990, sample NR 104.7, oblique lingual (7) and occlusal (8) views; (9) NIGP PZ 203991, sample NR 102, occlusal view; (10) NIGP PZ 203992, sample NQ 103.5, occlusal view; (11, 12) NIGP PZ 203993, sample NR 102, occlusal (11) and labial (12) views; (13) NIGP PZ 203994, sample SL 1.9, lingual view; (14) NIGP PZ 203995, sample SL 1.9, labial view. (15–17) Denaea cf. D. williamsi Ginter and Hansen, 2010: (15) NIGP PZ 203996, sample SL 4.2, labial view; (16) NIGP PZ 203997, sample NQ 99.8, labial view; (17) NIGP PZ 203998, sample NQ 103.5, occlusal view. (18–20) Denaea sp.: (18) NIGP PZ 203999, sample NQ 103.5, occlusal view; (19) NIGP PZ 204000, sample SL 220.4, occlusal view; (20) NIGP PZ 204001, sample NQ 105.4, labial view. (21) Cladodontomorphi indet., cusp with traces of bioerosion, NIGP PZ 204002, sample NR 102.9, lateral view. (22–25) Stethacanthulus meccaensis (Williams, 1985): (22) NIGP PZ 204003, sample NR 102.9, occlusal view; (23) NIGP PZ 204004, sample NQ 96.7, occlusal view; (24) NIGP PZ 204005, sample NQ 96.7, occlusal view; (25) NIGP PZ 204006, sample SL 1.9, labial view. (26, 27) Stethacanthulus decorus (Ivanov, 1999): (26) NIGP PZ 204007, sample SL 1.9, oblique labial view; (27) NIGP PZ 204008, sample SL 1.9, occlusal view. (28) Stethacanthus sp., NIGP PZ 204009, sample NR 102.9, labial view. (29) Phoebodontiformes indet., NIGP PZ 204010, sample NQ 16.3, labial view. (30) Jalodontiformes indet., cusp, NIGP PZ 204011, sample NR 177.8, labial view. Scale bars = 100 μm.

Figure 6

Figure 7.Cladodontomorph teeth from the Carboniferous of Sholaksay section, Kazakhstan: from the Serpukhovian (8, 10, 12, 13, 16, 17, 19–25) and Bashkirian (1–7, 9, 11, 14, 15, 18). (1–9) Denaea cf. D. williamsi Ginter and Hansen, 2010: (1, 2) PMSPU 114-1, sample 47, occlusal (1) and oblique labial (2) views; (3) PMSPU 114-2, sample 46i, oblique basal view; (4) PMSPU 114-3, sample 46i, lingual view; (5) PMSPU 114-4, sample 46i, oblique lateral view; (6) PMSPU 114-5, sample 46i, labial view; (7) PMSPU 114-6, sample 46i, occlusal view; (8) PMSPU 114-7, sample 43b, occlusal view; (9) tooth file, PMSPU 114-8, sample 46i, oblique labial view. (10–16) Stethacanthulus meccaensis (Williams, 1985): (10) PMSPU 114-9, sample 45a, occlusal view; (11) PMSPU 114-10, sample 47, occlusal view; (12) PMSPU 114-11, sample 44b, occlusal view; (13) PMSPU 114-12, sample 44b, oblique lateral view; (14) PMSPU 114-13, sample 46i, occlusal view; (15) PMSPU 114-14, sample 47, basal view; (16) PMSPU 114-15, sample 44b, labial view. (17–19) Stethacanthulus decorus (Ivanov, 1999): (17) PMSPU 114-16, sample 46b, occlusal view; (18) PMSPU 114-17, sample 47, oblique lingual view; (19) PMSPU 114-18, sample 46a, occlusal view. (20–23) Squatinactis cf. S. caudispinatus Lund and Zangerl, 1974: (20, 21) PMSPU 114-19, sample 45b, occlusal (20) and labial (21) views; (22) PMSPU 114-20, sample 45a, occlusal view; (23) PMSPU 114-21, sample 44b, occlusal view. (24, 25) Cladodontomorphi indet.: (24) PMSPU 114-22, sample 46a, occlusal view; (25) PMSPU 114-23, sample 45a, occlusal view. Scale bars = 100 μm.

Figure 7

Figure 8.Teeth of Gissarodus flabellatus Ivanov, 2013 from the Serpukhovian (1–3, 6–16) and Bashkirian (4, 5) of Sholaksay section, Kazakhstan: (1) PMSPU 114-24, sample 45b, occlusal view; (2) PMSPU 114-25, sample 43b, labial view; (3) PMSPU 114-26, sample 43b, occlusal view; (4) PMSPU 114-27, sample 47, oblique basal view; (5) PMSPU 114-28, sample 46i, occlusal view; (6) PMSPU 114-29, sample 43b, oblique occlusal view; (7) PMSPU 114-30, sample 46a, oblique lingual view; (8) PMSPU 114-31, sample 43b, labial view; (9) PMSPU 114-32, sample 44v, basal view; (10) PMSPU 114-33, sample 44v, lingual view; (11–16) PMSPU 114-34, sample 43b, microtomographic images: (11) oblique lateral view, (12) labial view, (13, 15) sagittal virtual sections in opaque (13) and transparent (15) models, (14) transversal virtual section in transparent model, (16) frontal virtual section of tooth base in transparent model. Abbreviations: ac = ascending vascular canal; ccp = central cusp; hc = horizontal vascular canal; icp = inner intermediate cusp; ict = intermediate cusplet; lc = longitudinal vascular canal; lcp = lateral cusp; lct = lateral cusplet; ocp = outer intermediate cusp. Scale bars = 100 μm.

Figure 8

Figure 9.Fish microremains from the Carboniferous–lower Permian of South China: from the Viséan (11), Serpukhovian (6), Bashkirian (9), and Gzhelian (1, 5) of the Naqing section; from the Gzhelian (3, 4, 7) and Asselian (10) of the Narao section; and from the Moscovian (8) and Gzhelian (2) of the Shanglong section. (1, 2) Symmoriiform denticles: (1) NIGP PZ 204012, sample NR 238.5, crown view; (2) NIGP PZ 204013, sample SL 220.4, lateral view. (3, 4) Hybodontid type of chondrichthyan scales: (3) NIGP PZ 204014, sample NR 269.4, crown view; (4) NIGP PZ 204015, sample NR 269.4, crown view. (5–8) Euselachian type of chondrichthyan scales: (5) NIGP PZ 204016, sample NQ 231.7, crown view; (6) NIGP PZ 204017, sample NQ 39.5, crown view; (7) NIGP PZ 204018, sample NR 255.3, basal view; (8) NIGP PZ 204019, sample SL 128.4, lateral view. (9) Actinopterygian tooth, NIGP PZ 204020, sample NQ 108.4, lateral view. (10, 11) Actinopterygian scales: (10) NIGP PZ 204021, sample NR 278.8, crown view; (11) NIGP PZ 204022, sample NQ 3.9, crown view. Scale bars = 100 μm.

Figure 9

Figure 10.Fish microremains from the Serpukhovian (3–6) and Bashkirian (1, 2, 7) of Sholaksay section, Kazakhstan. (1–3) Symmoriiform monocuspid (1) and multicuspid (2, 3) denticles: (1) PMSPU 114-35, sample 47, lateral view; (2) PMSPU 114-36, sample 46i, oblique anterior view; (3) PMSPU 114-37, sample 45b, oblique crown view. Chondrichthyan scales: (4) euselachian type, PMSPU 114-38, crown view; (5, 6) hybodontid type: (5) PMSPU 114-39, oblique lateral view, (6) PMSPU 114-40, crown view. (7) Acanthodiform scale, PMSPU 114-41, oblique crown view. Scale bars = 100 μm.

Figure 10

Figure 11.Comparative distribution of three chondrichthyan species: Gissarodus flabellatus, Denaea williamsi, Squatinactis caudispinatus. Abbreviations: NQ = Naqing section; NR = Narao section; SL = Shanglong section.