Volume 64,Issue 2,2025 Table of Contents

1 New advances in the study of Cambrian invertebrates and ecosystems in South China—Preface

OU Qiang

2025, 64(2):127-131. DOI: 10.19800/j.cnki.aps.2025825

[Abstract](148) [HTML](0) [PDF 496.90 K](196)

Abstract:
This special issue presents recent progress in the study of Cambrian invertebrates and marine ecosystems of South China by domestic scholars. It compromises nine articles contributed by 40 authors from 18 institutions. Six articles in this issue cover diverse research areas such as invertebrate morphology, biostratigraphy, taphonomy, chronology, and paleoecology. Collectively, these studies provide new insights into the radiation of the Cambrian invertebrates and new evidence for the evolution of modern-type marine ecosystems in Earth’s history.

2 Discovery of Watsonella crosbyi and Aldanella attleborensis from the Cambrian Kuanchuanpu Formation in northern Sichuan and stratigraphic implications

QIANG Ya-qin , GUO Jun-feng , LI Guo-xiang , SONG Zu-chen , PENG Jia-xin , ZHAO Xiao-fang , ZHANG Bo-yao , LV Hua-li

2025(2):132-145. DOI: 10.19800/j.cnki.aps.2025014

[Abstract](119) [HTML](0) [PDF 18.92 M](198)

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The sudden appearance of Small Shelly Fossils (SSFs) in the early Cambrian represents a crucial episode of the Cambrian radiation. The abundant and diverse SSFs also mark the origin of biomineralization of metazoans. SSFs are distributed globally in the lower Cambrian strata and several SSF assemblages have been established for the subdivision and correlation of pre-trilobitic Cambrian sequences. Currently, the Global Stratotype Section and Point (GSSP) of Cambrian Stage 2 (Terreneuvian Series) has not yet been formally defined. The first appearance data (FAD) of the widely distributed Watsonella crosbyi and Aldanella attleborensis, important components of the Watsonella crosbyi Assemblage (SSF Ⅲ), has been proposed as a potential biostratigraphic marker for defining the base of Cambrian Stage 2. Watsonella crosbyi and A. attleborensis are common mollusks in Cambrian strata of South China, particularly in eastern Yunnan, western and southern Sichuan, western Hubei, and southern Shaanxi. However, these two fossils have not been discovered previously in northern Sichuan, making it difficult to subdivide the Cambrian Terreneuvian strata in this region. Recently, we collected abundant SSFs, including W. crosbyi and A. attleborensis, from the uppermost Kuanchuanpu Formation at the Changtanhe section in northern Sichuan. Based on these SSFs, we establish the Watsonella crosbyi Assemblage in the uppermost Kuanchuanpu Formation of northern Sichuan, enabling biostratigraphic correlations with the Dahai Member of the Zhujiaqing Formation in eastern Yunnan, the uppermost Maidiping Formation in western and southern Sichuan, the Tianzhushan Member of the Dengying Formation and Member 5 of the Yanjiahe Formation in western Hubei, and the uppermost Kuanchuanpu Formation in southern Shaanxi. Moreover, the occurrence of W. crosbyi and A. attleborensis in northern Sichuan can be correlated with similar faunas in Siberia, Avalonia, Mongolia and Australia, indicating the significant role of the Watsonella crosbyi assemblage zone for global subdivision and correlation of Cambrian Stage 2 strata.

3 New evidence on geometric morphometrics and stratigraphic attribution of trilobite fossils from the Xihaoping Member and basal Shuijingtuo Formation (Cambrian Series 2, Stage 3) in Zhenba, southern Shaanxi, China

HOU Yang , HUA Hong , REN Jin-jie , LUO Jin-zhou , GONG Meng , WANG Xin-zi , BAI Lin , WU Zi-hui , WANG Xue-ting , ZHANG Song

2025, 64(2):146-164.

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Abstract:
The Zhenba area, situated on the northwestern margin of the Yangtze Platform, hosts an approximately 8.5-meter-thick phosphatic bioclastic carbonate unit at the base of the Cambrian. This unit, characterized by parallel unconformities with overlying and underlying strata and sparse sponge spicules and brachiopod fossils, has been the subject of stratigraphic debate: (1) assignment to the uppermost Dengying Formation; (2) designation as an independent Xihaoping Member; or (3) inclusion in the basal Shuijingtuo Formation. This study focuses on a layer rich in small shelly fossils at the base of the Shuijingtuo Formation and underlying Xihaoping Member, systematically collecting eodiscoid trilobite cranidia, and integrating previously reported specimens of Parabadiella cf. huoi from the disputed Xihaoping Member. Geometric morphometric analyses (PCA, CVA, and NMDS) of 30 well-preserved eodiscoid trilobites from the Shuijingtuo Formation, along with previously documented Parabadiella (Abadiella) specimens, were conducted. Our key findings include: (1) The newly collected specimens are assignable to Tsunyidiscus yanjiazhaiensis, with cranidial contour morphology closely matching that of the holotype; (2) The continuous morphospace distribution between Parabadiella and Abadiella supports their synonymization at the genus level; and (3) Based on parallel unconformities and the first appearance datum (FAD) of Abadiella and Tsunyidiscus, we propose that the Xihaoping Member represents an independent lithostratigraphic unit, constrained to the lower Cambrian Stage 3. This study provides quantitative morphological evidence for refining trilobite taxonomy and enhancing biostratigraphic correlations of the lower Cambrian strata in South China.

4 A brachiopod assemblage from the Cambrian ‘Tsinghsutung Formation’ of Jianhe, Guizhou and its significance

WANG Shou-juan , YANG Xing-lian , WEI Bu-qing , LI Hong-mei , MAO Yong-qin

2025, 64(2):165-181. DOI: 10.19800/j.cnki.aps.2025005

[Abstract](115) [HTML](0) [PDF 12.79 M](193)

Abstract:
The ‘Tsinghsutung Formation’ (Cambrian Series 2 Stage 4) in Jianhe County, Guizhou is mainly composed of a lithological assemblage featuring carbonate rocks at the lower and top parts, with interbedded mudstones and argilla-ceous limestones with various thickness at the middle and upper sections. The carbonate layers of the Cambrian ‘Tsinghsutung Formation’ at the Songshan section were systematically sampled and processed using acid etching method, allowing for the study of the highly abundant and diverse micro-brachiopods. Five genera and six species of micro-brachiopods from the ‘Tsinghsutung Formation’ are identified, including Eohadrotreta zhenbaensis and Hadrotreta primaea of the Acrotretoidea; Schizopholis napuru and Schizopholis yorkensis of the superfamily Acrotretacea; and Palaeobolus sp. and Eoobolus sp. of the superfamily Linguloidea. Eohadrotreta zhenbaensis is dominant, accounting for approximately 80% of the assemblage. Notably, E. zhenbaensis and S. yorkensis are discovered for the first time in the study area. A comparison of characters of the micro-brachiopod assemblage from the carbonate rocks of the ‘Tsinghsutung Formation’ with those of macro-brachiopods in clastic rocks, as reported by previous researchers from Jianhe, reveals a micro-brachiopod fauna dominated by Eohadrotreta in the carbonate rocks. In contrast, a large number of macro-brachiopod Nisusia, along with smaller amounts of Diandongia and Kutorgina, are uniquely preserved in the clastic rocks. This difference between these assemblages may be resulted from variations in burial conditions or changes in relative sea level and environmental substrates. This study not only enriches our understanding of the characteristics of the brachiopod assemblage from the ‘Tsinghsutung Formation’, but also provides more information for a comprehensive understanding of the brachiopod composition in Cambrian Stage 4 and their evolutionary adaptations to environmental changes.

5 Preliminary study on the taphonomy of brachiopod shell concentrations from the Cambrian Jindingshan Formation in Xifeng, Guizhou

LI Hong-mei , YANG Xing-lian , YUAN Yuan , WANG Shou-juan , ZHOU Si-xuan

2025, 64(2):182-198. DOI: 10.19800/j.cnki.aps.2025006

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Brachiopods are key components of the Cambrian marine benthic ecosystems. Through the efficient filter-feeding and attachment functions, they contributed to the stabilization of the benthic environments. Brachiopod shell concentrations played a significant role in shaping the ecological tiering and community structures during the Cambrian explosion. Numerous brachiopod shell concentrations have been discovered from the middle part of the Jindingshan Formation (Cambrian Stage 4) in Xifeng, Guizhou Province, China. Comprehensive investigations reveal that these brachiopod shell concentrations predominantly exhibit two distinct burial types: (1) The concentrations are mainly composed of a single species, Westonia sp., with shells preserved in black; and (2) The concentrations are dominated by Westonia sp., but with grayish-white shells, co-occurring with a few specimens of Eoobolus malongensis, trilobites, chancelloriids, and hyoliths. The shells in both types of concentrations are oriented nearly parallel to the bedding plane. The shell sizes vary considerably, and no obvious preferred orientation is observed. Examination of polished, longitudinal surfaces of rock slabs and thin sections reveals only faint horizontal bedding, with no evidence of strong hydrodynamic forces or traces of bioturbation. These observations suggest that the brachiopod communities were buried in situ in a relatively stable environment, without significant disturbance from currents or transportation Energy-dispersive spectroscopy (EDS) analyses show that the brachiopod shells from this area are enriched in iron-aluminum silicates. During burial, mineral replacement occurred: Pyrite in the shell resulted from early diagensis was altered, and iron-aluminum-rich silicates were subsequently deposited as secondary minerals, playing an important role in diagenesis. These findings not only provide new insights into the brachiopod assemblages of the Jindingshan Formation but also offer crucial evidence for reconstructing the paleoenvironmental conditions and sedimentary events during the Cambrian explosion.

6 Sponge spicule fossils from Member 3 of the Cambrian Qingxi Formation in the Sanjiang area, Guangxi

JIA Qi-ying , SHEN Yang , LI Yu-kun , SUN Li-xin , JING Xiu-chun , YU Zi-dong , ZHANG Man , LIU Tian-jia , TANG Hui-xin

2025, 64(2):199-210. DOI: 10.19800/j.cnki.aps.2025017

[Abstract](152) [HTML](0) [PDF 12.64 M](152)

Abstract:
Sponges (Porifera) are among the oldest metazoan groups, and their fossilized spicules are of great importance in sponge research. In this study, numerous sponge spicule fossils were discovered in a limestone layer of Member 3 of the Cambrian Qingxi Formation in the Sanjiang area, Guangxi, China. A systematic analysis was conducted to document the morphological characteristics of different types of these sponge spicules. The results indicate that the sponge spicules from Member 3 of the Qingxi Formation are abundant and diverse, with diaxonic tetractine spicules dominating and accounting for over 85% of the total. In addition, more complex forms, such as pentactines and orthotetraenes, were identified. Scanning electron microscopy (SEM) revealed the internal cross-sectional structures of axial canals within these spicules. Energy-dispersive X-ray spectroscopy (EDS) analysis showed that their elemental composition consists primarily of Si and O. Based on comparisons of morphological variations of these spicules, this study suggests that the sponges from Member 3 of the Cambrian Qingxi Formation in the Sanjiang area of Guangxi may have primarily formed grid-like structures composed of cross-shaped and X-shaped sponge spicules. These findings provide new data for the classification and evolutionary study of Cambrian sponge spicule fossils.

7 Community composition and ecospace occupation of the Cambrian Kaili Biota in Danzhai County, Guizhou Province

ZHANG Pei , MA Wen-yu , LIU Jing , OU Xiu-cheng , SU Zi-yi , YANG Yu-ning

2025, 64(2):211-225. DOI: 10.19800/j.cnki.aps.2025004

[Abstract](127) [HTML](0) [PDF 17.55 M](177)

Abstract:
Cambrian Konservat-Lagerst?tten provide detailed insights into the ecological structures of marine communities and offer critical data for community ecology research. However, quantitative ecological analyses of the Cambrian Kaili Biota (Wuliuan, Miaolingian) in eastern Guizhou remain limited. Such analyses are essential for understanding high biodiversity and individual abundance within the biota. In this study, we used multivariate statistical analyses to analyze data on the Kaili Biota from the Sanwan section in Nangao County, eastern Guizhou. The fossil assemblage comprises 57 species in 46 genera, representing eight phyla (Arthropoda, Brachiopoda, Echinodermata, Priapulida, Hyolitha, Chancelloriids, Cnidaria, and Porifera) and 12 ecological types. Among these, arthropods exhibit the highest taxonomic diversity at the species level (60.9%) and individual abundance (80.4%). In terms of ecospace occupation, vagrant benthos dominate the community, followed by active swimming predators. This pattern reflects the unique ecospace occupation of the community on the Jiangnan Slope of the Yangtze Platform during the Cambrian Period.

8 Rhuddanian (Silurian) graptolite-bearing strata and their sedimentary environments in the Xike’er area of Jiashi, Xinjiang

LIU Chu-yuan , CHEN Qing , ZHANG Yuan-yuan , SUN Zong-yuan , ZHANG Lin-na , TANG Peng

2025, 64(2):226-241. DOI: 10.19800/j.cnki.aps.2025016

[Abstract](76) [HTML](0) [PDF 21.69 M](164)

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At the beginning of the Silurian, black shales were widely deposited across various latitudes, likely driven by large-scale global marine transgressions and extensive anoxic events. However, in contrast to the widespread black shales of the Lungmachi Formation in South China, the early Silurian Kalpintag Formation on the northwestern margin of the Tarim Basin consists predominantly of green-yellow silty mudstone, muddy siltstone, and siltstone. Although the formation is well developed and well exposed, it remains poorly documented. This study focuses on the basal part of the Kalpintag Formation at the Xike’er North section, approximately 1.5 km north of the Xike’erkule Town, Jiashi County, Kashi (Kashgar) Prefecture, Xinjiang. The basal part of the Kalpintag Formation at this section is characterized by greenish grey mudstone and yields a graptolite fauna with a total of eight species in four genera, including Korenograptus lungmaensis (Sun), K. jerini (Koren’ and Melchin), Metabolograptus parvulus (Lapworth), M. wangjiawanensis (Mu and Lin), Normalograptus skeliphrus Koren’ and Melchin, N. mirnyensis (Obut and Sobolevskaya), N. cf. ajjeri (Legrand), and Akidograptus? sp. This fauna indicates an early Rhuddanian age (Silurian), corresponding to the Akidograptus ascensus-Parakidograptus acuminatus Zone. In addition, we investigate the early Silurian sedimentary environments through integrated lithofacies, biofacies, and geochemical analyses, and further explore the dominant factors controlling the development of environmental phases based on stratigraphic correlation to the contemporaneous strata in South China.

9 Review and prospects on fossil Tipulidae (Insecta: Diptera)

WANG Chu-ping , LIU Yu-shuang

2025, 64(2):242-249. DOI: 10.19800/j.cnki.aps.2024036

[Abstract](122) [HTML](0) [PDF 3.52 M](171)

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Tipulidae is one of the groups with high diversity in Diptera, Nematocera. To date, more than 4,000 species of extant and fossil species have been recorded, distributed on all continents except Antarctica. Among them, nine genera and 139 fossil species have been reported, with their geological age ranging from the Late Jurassic to the Miocene. In this paper, the venation patterns of representative genera and subgenera of fossil Tipulidae are redrawn, the research history and the distribution of fossil Tipulidae in different geological periods are summarized, and research challenges and future prospects are discussed.

10 Application of transfer-learning-based convolutional neural network in fossil image classification

XU Hui-qing , WANG He-yang , SHI Yu-kun

2025, 64(2):250-260. DOI: 10.19800/j.cnki.aps.2025022

[Abstract](95) [HTML](0) [PDF 4.17 M](162)

Abstract:
Taxonomic identification of fossil is fundamental in paleontology research. However, traditional taxonomic methods rely heavily on expert experience and are inherently time-consuming. The development of deep learning architectures has made image-based fossil identification increasingly feasible. In this study, we apply an integrated framework that combines convolutional neural networks (CNN) with transfer learning to develop well-designed and trained machine-learning models for paleontological research. A fossil image dataset comprising 3, 358 images in five invertebrate classes and subclasses is compiled to train a VGG16 classifier. This dataset presents challenges due to its limited dataset size, high-dimensional data features, and inter-class/subclass sample imbalances. To address these issues, data augmentation and a two-phase transfer learning strategy are employed in the training process. In the first phase, only the final fully connected layer is randomly initialized and trained, while other layers are frozen with pretrained ImageNet weights. In the second phase, the whole model is fine-tuned with a reduced learning rate. The optimized model achieves an accuracy of 97.33%, a precision of 97.26%, a recall of 97.07%, and an F1-score of 97.16% on the test set. An ablation study is also conducted to test the effectiveness of transfer learning. A VGG16 classifier trained with random initialization achieves an accuracy of 74.89% on the test set. These results demonstrate that the constrained scientific datasets can be effectively utilized through (1) transfer-learning-enhanced CNN architectures; (2) strategic data augmentation protocols and (3) a progressive fine-tuning process. Notably, the model successfully accommodates heterogeneous input conditions of the fossil images, including varying imaging equipment, taxonomic diversity, complex image backgrounds, and environmental noises. This highlights the potential of the proposed framework for developing high-precision classifiers capable of fine-grained taxonomic discrimination at genus or species level, while maintaining computational efficiency. The achieved performance benchmarks suggest promising applications for automated fossil identification systems in paleontological research.

Volume 64,Issue 2,2025 Table of Contents

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