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Article

New Discovery of Bradoriids from the Lower Cambrian Shuijingtuo Formation in the Eastern Three Gorges Area, South China

by
Feiyang Chen
1,2,*,
Yucheng Lian
1,2 and
Yi Wang
1,2,3
1
Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process, Ministry of Education, China University of Mining and Technology, Xuzhou 221008, China
2
School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China
3
Sdeg Geothermal New Energy Corporation Co., Ltd., Jinan 250104, China
*
Author to whom correspondence should be addressed.
Diversity 2025, 17(10), 719; https://doi.org/10.3390/d17100719
Submission received: 16 September 2025 / Revised: 9 October 2025 / Accepted: 9 October 2025 / Published: 15 October 2025
(This article belongs to the Section Phylogeny and Evolution)
Browse Figures
Versions Notes

Abstract

The early Cambrian complex ecosystem was dominated by lophotrochozoans and ecdysozoans, with arthropods constituting the most prominent animal group during the Cambrian Explosion. Bradoriids, an extinct lineage of small bivalved arthropods, first appeared slightly earlier than the oldest known trilobites, in the early Cambrian Abadiella Trilobite Biozone (Series 2, Stage 3) of both South China and South Australia. They subsequently achieved a global distribution and reached particularly high diversity and abundance in the early Cambrian of South China. Here we systematically describe two bradoriid species from the upper Shuijingtuo Formation in western Hubei: Houlongdongella disulcata Lee, 1975 and Houlongdongella elevata Cui, 1989. This study represents the first record of both species in the eastern Three Gorges Area, Hubei Province, thereby extending their known geographic ranges. Biostratigraphic correlation based on the occurrence of H. disulcata and H. elevata, alongside with previously reported trilobites and small shelly fossils, indicates that the middle–upper Shuijingtuo Formation in western Hubei corresponds to the late Chiungchussuan to Tsanglangpuan ages (upper Stage 3–Stage 4). Therefore, bradoriids would be a useful proxy for resolving biostratigraphic issues of regional or global correlation within the Cambrian.

1. Introduction

Arthropoda represents the most evolutionarily and ecologically successful phylum in the animal kingdom, comprising approximately 80% of all extant animal species [1,2]. They occupy diverse ecological niches—including predators, decomposers, pollinators, and parasites—and play critical roles in modern ecosystems [3,4]. The origin and early diversification of arthropods dates back to the Cambrian period [5,6,7]. The oldest arthropod trace fossils are recorded in Terreneuvian strata [8], while body fossils first appear in Cambrian Stage 3, followed by rapid evolutionary radiation [7,9,10,11]. Bradoriids are the earliest total-group arthropod body fossils, which emerged slightly earlier than trilobites of the Abadiella Trilobite Biozone (Epoch 2, Age 3; ca. 521 Ma) in both South China and South Australia [12,13,14,15]. They diversified rapidly during the “Cambrian Arthropod Radiation Event,” becoming a significant component of the Cambrian Evolutionary Fauna [15,16], before eventually going extinct in the Early Ordovician [17].
Bradoriids are a group of small sized bivalved arthropods whose carapace varies from 2 to 18 mm in length and with sulcal and lobal features. Previous study of Bradoriida begun in late nineteenth century and early twentieth century [18,19,20]. Based on bivalved carapace, general morphology and overall size range, bradoriids were traditionally regarded as ostracod crustaceans [18,21,22,23,24]. Later, well-preserved soft part anatomy of typical bradoriids, like the Kunmingella and Kunyangella from the Chengjiang Biota, suggests they are stem-group crustaceans [12,25]. Bradoriids were also recovered as sister to total-group mandibulates by Legg et al. [26]. The present-day alternatives are to classify them as stem-group arthropods [27].
Bradoriids are commonly found in mudstone, sandstone, and carbonate rocks deposited in well-oxygenated shelf marine environments, ranging from nearshore to more offshore settings [12,16,28,29]. Most bradoriids are interpreted to have had a benthic or nekto-benthic mode of life [16,17,28,30,31]. They played a significant role in early Cambrian ecosystems as motile epibenthic dwellers, functioning as detritus feeders, micro-scavengers, or micro-predators of non-mineralized animals. In addition, they contributed to the recycling of organic material on the seafloor and served as a food source for other organisms [17,32,33].
Bradoriids achieved a global distribution during the Cambrian and are well documented from several palaeocontinents, including Laurentia [30], Siberia [34], Baltica [35,36,37], Avalonia [29], Gondwana [14,38,39,40,41], and South China [12,13,42]. They occur in all major Cambrian Lagerstätten, such as the Chengjiang, Buen Formation, and Burgess Shale, where they are preserved as body fossils with some soft tissues [12,28,30,43,44]. Additionally, bradoriids are frequently preserved as phosphatized small shelly fossils in carbonate sequences [41,45].
To date, at least seven families of bradoriids are considered to form a monophyletic group sensu stricto: Cambriidae, Kunmingellidae, Comptalutidae, Bradoriidae, Hipponicharionidae, Beyrichonidae, and Svealutidae [17]. Three additional families—Duibianellidae, Monasteriidae, and possibly Zhexiellidae—have also been proposed [46]. Previous taxonomic studies on Chinese bradoriids have been subject to long-standing debate, with initial diversity estimates (approximately 80 genera and nearly 300 species) considered greatly overestimated [12]. Subsequent revisions have recognized a total of 17 valid genera [12,17], which are documented mainly from the provinces of Yunnan, Sichuan, Hunan, Hubei, Henan, Shaanxi, and Qinghai, reflecting a distinct regional endemism.
Bradoriids were highly diverse and abundant in both South China and eastern Gondwana (particularly South Australia) during the early Cambrian [12,13,14,17,25,33,41,47,48]. A synthesis of the global distribution of early Cambrian bradoriids by Topper et al. [14] revealed strong biogeographic connections between South China and Australia at the genus level, especially within the families Comptalutidae and Hipponicharionidae [12,13]. Among these, Comptalutidae is notably diverse, with 12 genera reported from South China—the highest global diversity recorded for this family [14]. It represents one of the dominant components of bradoriids in the region [12]. Palaeogeographic studies indicate that comptalutids preferred warm tropical to subtropical waters, distributed along an arc between approximately 30° N and 15° S [17]. Despite this broad distribution, the comptalutid Houlongdongella is previously known only from South China and is considered endemic to the region [13,14,42]. But the description of Houlongdongella from the Atdabanian of Kazakhstan probably is the only occurrence data of this taxon outside China [49]. To date, nine species of Houlongdongella have been reported: H. disulcata, H. elevata, H. hubeiensis, H. shennongjiaensis, H. sulcata, H. brevidorsa, H. inflata, H. sphaerica, and H. xichuanensis [12,13,42,50,51,52,53,54].
In this study, we report the first occurrence of one genus and two species of bradoriids—Houlongdongella disulcata Lee, 1975 [50] and H. elevata Cui, 1989 [55] from the Shuijingtuo Formation in the Three Gorges Area, Hubei Province, South China. Their presence extends the known geographic range of these species and offers new biostratigraphic insights for correlation between Hubei, Shaanxi, and Yunnan provinces. The morphological terminology used in this study follows Öpik [56], Hinz-Schallreuter [38], Siveter and Williams [30] and Zhang [13].

2. Geological Setting, Materials and Methods

The Three Gorges Area is situated on the northern margin of the Yangtze Platform (Figure 1A). Well-developed and extensively outcropped late Neoproterozoic to early Cambrian sedimentary successions have long been the focus of stratigraphic research [57,58,59,60,61,62,63,64,65]. The succession comprises, in ascending order, the Dengying, Yanjiahe, Shuijingtuo, Shipai, Tianheban, and Shilongdong formations (Figure 1B–D).
The Ediacaran Dengying Formation consists primarily of carbonate rocks, with a thickness of approximately 300 m. It is disconformably overlain by the lowermost Cambrian Yanjiahe Formation, which is about 40 m thick and dominated by thin to moderately banded argillaceous limestone rhythmically intercalated with thin-bedded muddy siltstone. This unit yields abundant pre-trilobite small shelly fossils as well as exquisitely preserved macroscopic organisms [67,68,69,70,71]. A disconformity also marks the contact between the Yanjiahe and the overlying Shuijingtuo Formation. The latter is composed of approximately 70 m of calcareous black shale interbedded with variably banded bioclastic and muddy limestones. The lower Shuijingtuo Formation is characterized by condensed black shale intercalated with carbonate concretions, while the upper part contains abundant and diverse shelly fossils, including hyoliths, lobopodians, mollusks, sponges, and chancelloriids, with particularly significant occurrences of brachiopods and the oldest eodiscoid trilobites in South China [54,57,62,65,72,73,74]. The contacts between the Shuijingtuo, Shipai, Tianheban, and Shilongdong formations are conformable. The Shipai Formation is dominated by siltstone and silty mudstone with intercalated limestone layers and has previously yielded diverse and abundant fossils such as trilobites, brachiopods, hyolithids, and bradoriids [57]. The Tianheban Formation consists mainly of banded argillaceous limestone, whereas the Shilongdong Formation is predominantly composed of dolomite.
The bradoriid fossils examined in this study were collected from the upper part of the Shuijingtuo Formation at the Aijiahe (AJH) and Wangjiaping (WJP) sections, located in the Zigui County, Yichang, Hubei Province (Figure 1D). Detailed stratigraphic information regarding the fossil localities refers to Zhang et al. [66]. To date, three individual valves of H. disulcata and nine individual valves of H. elevata have been obtained. All specimens were recovered through maceration of limestone samples using acetic acid (5–10%). Bradoriid remains were manually picked under a ZEISS Stemi 305 stereomicroscope. Selected specimens were gold-coated and imaged using a Scanning Electron Microscope (SEM) at the State Key Laboratory of Continental Dynamics, Northwest University (Xi’an, China), and a Zeiss Supra 35 VP Field Emission at the Evolutionary Biology Centre of Uppsala University (Uppsala, Sweden). All specimens are deposited in the Early Life Institute collections at Northwest University (AJH-SJT and WJP-SJT), Xi’an, China.

3. Systematic Palaeontology

Phylum Arthropoda Siebold and Stannius, 1845
Subphylum and Class uncertain
Order Bradoriida Raymond, 1935 [75]
Family Comptalutidae Öpik, 1968 [56]
Genus Houlongdongella Lee, 1975 [50]
Type species. Houlongdongella disulcata Lee, 1975 [50]; from the lower Cambrian Canglangpu Formation in Kunming, eastern Yunnan, China.
Diagnosis (Modified from Zhang [13]). Comptalutids with medium-sized, postplete valves, characterized by evenly concave frontal and posterodorsal margins. Anterior lobe elongate, conjoined ventrally with a prominently inflated central valve portion. Sulcus deep, containing a muscle spot. Marginal rim broad and convex, delineated by a broad marginal groove. Valve surface ornamented with fine tubercles arranged in a reticulate pattern.
Occurrence. Yunnan, Henan, Hubei, Shaanxi and Chongqing of South China, Cambrian Series 2, and Cambrian Atdabanian of Kazakhstan.
Houlongdongella disulcata Lee, 1975 (Figure 2) [50]
1975 Houlongdongella disulcata, Lee, p. 50, plate 1, Figures 18–20 [50].
1985 Houlongdongella disulcata, Huo and Shu, p. 90, plate 21, Figure 13 [42].
1990 Zepaera primitiva, Shu, p. 49, plate 8, Figures 1–4 and 8 [76].
1990 Alutella duplicata, Shu, p. 50, plate 8, Figures 9–12 [76].
1990 Houlongdongella disulcata, Melnikova, p. 42, plate 1, Figure 12 [49].
1991 Houlongdongella elevata, Huo et al., p. 92, plate 8, Figures 3 and 5–8 [77].
2007 Houlongdongella disulcata, Zhang, p. 132–133, plate 13, Figures 1–6. Text-Figure 3L [13].
Holotype. CIGMR no. YO3 (left valve), Lee, 1975, plate 1, Figure 19, from the Cambrian (Series 2) Canglangpu Formation at Qiongzhusi section, Kunming, Yunnan Province, South China [50].
Diagnosis (Modified from Zhang [13]). Small, postplete valves with straight dorsal margin. Anterior lobe elongate and inflated, conjoined ventrally with the central part of the valve. A V-shaped sulcus situated underneath the anterodorsal border; a subrounded subdorsal node present dorsally. Broad, prominent marginal rim runs along the free margin, demarcated from the valve by a broad marginal groove.
Material. Three isolated specimens—comprising two left valves and one fragmented valve—collected from the upper Shuijingtuo Formation at the Aijiahe section, Hubei Province, South China.
Description. Valves slightly to moderately postplete, reaching up to 630 µm in height and 800 µm in width. Dorsal margin slightly arched and somewhat shorter than the valve width. Frontal and posterodorsal margins nearly straight; anteroventral, ventral, and posteroventral margins moderately curved. Anterior extremity gently rounded. A deep V-shaped sulcus presents beneath the anterodorsal margin. A shuttle-shaped, gently inflated anterior lobe extends posteroventrally and merges with the highly inflated central valve. Subdorsal node not observed. A subrounded muscle spot with a smooth surface is situated posterior to the anterior lobe. A prominent, convex marginal rim is demarcated from the inflated valve by a broad marginal groove. Valve surface ornamented with a concave, irregular network of pentagonal and hexagonal patterns defined by fine ridges. Polygons average 17 μm in diameter.
Remarks. The specimens of H. disulcata from the Aijiahe section are smaller than those documented from Shaanxi Province by Zhang [13]. The slightly postplete valve, absence of a subdorsal swelling, and the morphology of the subdorsal node and anterior lobe suggest these individuals represent a pre-adult stage, likely corresponding to instar 3–4 as proposed by Zhang [13]. The external polygons on the valves of H. disulcata are slightly larger than those reported in Zhang [13] and resemble the epithelial cell moulds observed in acrotretid brachiopods from the Shuijingtuo Formation at the Aijiahe section [66], as well as the cuticle remains of some Cambrian small shelly fossils [78].
Houlongdongella elevata Cui, 1989 (Figure 3) [55]
1989 Houlongdongella elevata Cui–Huo and Cui, p. 78, plate 2, Figures 1–5 [55].
1990 Zepaera primitiva, Shu, p. 49, plate 8, Figure 7 [76].
1991 Houlongdongella elevata, Huo et al., p. 94, plate 9, Figures 1–5 [77].
2007 Houlongdongella elevata, Zhang, p. 133–134, plate 13, Figures 7–17. Text-Figure 3M, N [13].
Holotype. NWUX S 84026 (left valve), Huo and Cui, 1989 [55], plate 2, Figure 1, from the Cambrian (Series 2) Shuijingtuo Formation at Longquanxi section, Pengshui, Chongqing, South China.
Diagnosis (After Huo and Cui [55]). Small, postplete valves with straight dorsal margin. Elongated, bulbous anterior lobe conjoined ventrally with the highly inflated central valve. A deep U-shaped sulcus situated beneath the anterodorsal border. Rounded subdorsal node present dorsally. Anterior free margin bordered by a narrow marginal rim; rim broadest along posteroventral margin, demarcated from valve by a broad marginal groove.
Material. Nine isolated specimens, comprising four left valves, one right valve, and four fragmented valves, collected from the upper part of the Shuijingtuo Formation at the Aijiahe and Wangjiaping sections, Hubei Province, South China.
Description. Valves postplete, reaching up to 1050 µm in height and 1050 µm in width. Dorsal margin straight, slightly shorter than the valve width. Frontal margin nearly straight; anteroventral margin slightly concave; ventral margin gently convex. Anterior and posterior extremities not observed or weakly projecting. A deep U-shaped sulcus lies beneath the anterodorsal margin, containing a subrounded subdorsal node and a rounded, smooth muscle spot. Anterior lobe elongated, bulb-like, extending posteroventrally and connecting to the highly inflated central valve. Marginal rim convex, broadening ventrally and posteriorly, and separated from the inflated valve by a broad marginal groove. Valve surface ornamented with a concave, irregular reticulated network composed of tetragonal, pentagonal, and hexagonal patterns defined by fine ridges. Polygons range from 11 to 21 μm in diameter, averaging 16 μm.
Remarks. The specimens of H. elevata from the eastern Three Gorges Area are slightly smaller than those reported from Shaanxi Province and Chongqing in Zhang [13]. The postplete valve, straight dorsal margin, U-shaped sulcus, and bulb-like anterior lobe are indicative of an adult stage (instar 5), as described by Zhang [13]. In contrast to the linearly arranged minute tubercles on the reticulated network reported by Zhang [13], the ornamentation in the present specimens consists of irregular reticulated networks defined by fine ridges. The external polygons of H. elevata resemble those of H. disulcata, but with slightly weakly raised edges.

4. Discussion

4.1. First Occurrence of Houlongdongella from the Shuijingtuo Formation in Hubei

Although previous studies have indicated a global distribution of bradoriids [12,13,14,17], most species and/or genera exhibit high degrees of endemism [14,17,41], likely constrained by climatic factors and a preference for palaeo-tropical/subtropical environments [17]. To date, Cambrian comptalutids Houlongdongella, comprising nine species, has a restricted geographical distribution limited to South China and Kazakhstan [13,14,49]. H. disulcata has been documented from the Shuijingtuo Formation in Shaanxi Province and the Canglangpu Formation in Yunnan Province [13], while H. elevata has been reported from the Shuijingtuo Formation in both Shaanxi Province and Chongqing [13]. Although diverse small shelly fossils from the Shuijingtuo Formation in Hubei Province have recently received increasing attention [62,78], bradoriids have remained poorly documented. The new material of H. disulcata and H. elevata presented in this study represents the first detailed systematic report of these taxa from the Shuijingtuo Formation in Hubei Province. This discovery extends the known geological distribution of both species within South China.

4.2. Early Cambrian Stratigraphic Correlation

Traditionally, the chronostratigraphic framework for early Cambrian in China is defined by units established in eastern Yunnan, which include, in ascending order, the Meishucunian, Chiungchussuan, Tsanglangpuan, and Lungwangmiaoan stages [79,80]. However, disconformities and hiatuses within the lower Cambrian successions of western Hubei and southern Shaanxi have complicated precise stratigraphic correlation among these regions and eastern Yunnan. The Xihaoping Member of the Dengying Formation in southern Shaanxi was initially correlated with the pre-trilobitic Meishucunian Stage (Terreneuvian Series, Stage 2) of eastern Yunnan [81,82]. Subsequent discoveries of small shelly fossils and polymerid trilobite remains, however, suggest an early to middle Chiungchussuan age (Cambrian Stage 3) for this unit [54,73,83,84,85,86]. More recently, Zhang et al. [87] reported the oldest-known trilobite–brachiopod association (Parabadiella cf. huoi–Eoobolus incipiens) from the Xihaoping Member, alongside typical small shelly taxa such as Cambroclavus and Ninella, further supporting an early Chiungchussuan age (Stage 3). Consequently, the disconformably overlying Shuijingtuo Formation in southern Shaanxi is considered equivalent to the late Chiungchussuan to Tsanglangpuan (late Stage 3–Stage 4) in eastern Yunnan [87].
A newly described specimen of the bivalved arthropod Caudicaella aff. bispinata from the lower Heatherdale Shale in South Australia [88] closely resembles Caudicaella bispinata from the basal Shuijingtuo Formation in western Hubei, which occurs just below the first appearance of the trilobite Tsunyidiscus [89,90]. The Australian specimen was found stratigraphically above global positive δ13C Excursion III [91,92]. Integrated biostratigraphic, chemostratigraphic, and lithological evidence supports an early Chiungchussuan age (Stage 3) for the base of the Shuijingtuo Formation in Hubei [41,65,87,88,90,91,93,94]. Thus, the middle and upper parts of the formation in Hubei likely span the late Chiungchussuan to Tsanglangpuan (late Stage 3–Stage 4) [65,87].
Furthermore, recent studies highlight the biostratigraphic utility of bradoriids [41,45,95]. H. disulcata has been documented from the Tsanglangpuan-aged Canglangpu Stage in Yunnan and the Shuijingtuo Formation in Hubei [13], while H. elevata was reported from the Shuijingtuo Formation within the Eoredlichia–Wutingaspis Zone in Shaanxi [13]. In this study, both species are recorded from the upper Shuijingtuo Formation in Hubei, corroborating a late Chiungchussuan to Tsanglangpuan age (late Stage 3–Stage 4) for the middle–upper Shuijingtuo Formation in this region [65,87].

5. Conclusions

This study presents the first detailed systematic description of the bradoriids Houlongdongella disulcata and Houlongdongella elevata from the Shuijingtuo Formation in Hubei Province, South China. The discovery of these species not only enriches the biodiversity recorded within the Shuijingtuo Formation but also significantly extends their known geological distribution from Kazakhstan, southern Shaanxi and eastern Yunnan to western Hubei. Integrated biostratigraphic evidence, supported by previous palaeontological, geochemical, and lithological data, indicates that the occurrence of H. disulcata and H. elevata in the upper part of the Shuijingtuo Formation corroborates a late Chiungchussuan to Tsanglangpuan age (late Stage 3–Stage 4) for the middle–upper Shuijingtuo Formation in western Hubei. These findings enhance our understanding of regional stratigraphic correlations and the palaeobiogeography of early Cambrian bradoriid arthropods in South China.

Author Contributions

Conceptualization, F.C.; formal analysis, F.C.; funding acquisition F.C.; project administration, F.C.; resources, F.C.; investigation, F.C., Y.W. and Y.L.; writing—original draft preparation, F.C.; writing—review and editing, F.C., Y.W. and Y.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by National Natural Science Foundation of China, grant number 42202005; the Natural Science Foundation of Jiangsu Province, grant number BK20221151.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author(s).

Acknowledgments

We thank Z. F. Zhang, Z. L. Zhang and J. P. Zhai for their help in field work and sample collecting. We thank the two anonymous reviewers for their detailed and constructive suggestions and comments. F.Y.C is grateful to the Northwest University palaeontology research group for previous guidance and support.

Conflicts of Interest

Author Yi Wang was employed by the company Sdeg Geothermal New Energy Corporation Co., Ltd., Jinan 250104, China. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Figure 1. Simplified geological map of China—fossil locality and stratigraphic column of the lower Cambrian in the Three Gorges area, South China (modified from reference [66]). (A) Simplified geographical map showing the position of the Three Gorges area. (B) Sketch map of studies area in Yichang, western Hubei. The fossil locality investigated in this paper is indicated by grey stars. (C) Geological map of the study area with the position of the Aijiahe section. (D) Stratigraphic column of lower Cambrian at the Aijiahe section. Horizon yielding bradoriids is indicated by fossil symbol.
Figure 1. Simplified geological map of China—fossil locality and stratigraphic column of the lower Cambrian in the Three Gorges area, South China (modified from reference [66]). (A) Simplified geographical map showing the position of the Three Gorges area. (B) Sketch map of studies area in Yichang, western Hubei. The fossil locality investigated in this paper is indicated by grey stars. (C) Geological map of the study area with the position of the Aijiahe section. (D) Stratigraphic column of lower Cambrian at the Aijiahe section. Horizon yielding bradoriids is indicated by fossil symbol.
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Figure 2. Houlongdongella disulcata Lee, 1975 [50] from the Shuijingtuo Formation at the Aijiahe section, Yichang County, Hubei Province, South China. (A–C) AJH SJT S05 BE-009, exterior view of left valve. (D) Enlarged exterior view of white block in A, showing the muscle spot and irregular polygons on valve surface. (E–G) AJH SJT S05 BE-005 exterior view of left valve. (H,I) AJH SJT S05 BE-005, enlarged exterior view of irregular polygons on valve surface in (E).
Figure 2. Houlongdongella disulcata Lee, 1975 [50] from the Shuijingtuo Formation at the Aijiahe section, Yichang County, Hubei Province, South China. (A–C) AJH SJT S05 BE-009, exterior view of left valve. (D) Enlarged exterior view of white block in A, showing the muscle spot and irregular polygons on valve surface. (E–G) AJH SJT S05 BE-005 exterior view of left valve. (H,I) AJH SJT S05 BE-005, enlarged exterior view of irregular polygons on valve surface in (E).
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Figure 3. Houlongdongella elevata Cui, 1989 [55] from the Shuijingtuo Formation at the Aijiahe and Wangjiaping sections, Yichang County, Hubei Province, South China. (A) AJH SJT 8-2-3 BK-013, lateral view of right valve, showing subdorsal node, U-shaped sulcus and bulb-like anterior lobe. (B) AJH SJT 8-2-3 BK-013, posteroventral view of right valve. (C) AJH SJT 8-2-3 BK-013, dorsal view of right valve. (D) AJH SJT 8-2-3 BK-013, anteroventral view of right valve. (E) Enlarged polygons with fine ridges on valve surface in A (white frame). (F) AJH SJT S05 BE-016, lateral view of left valve. (G) AJH SJT S05 BE-016, dorsal view of left valve, showing subdorsal node. (H) AJH SJT S05 BE-016, ventral view of left valve. (I) AJH SJT S05 BE-017, enlarged exterior view of irregular polygons. (J) WJP SJT 7 BL-001, anteroventral view of right valve, showing subdorsal node, U-shaped sulcus and bulb-like anterior lobe. (K,L) AJH SJT S05 G017, enlarged exterior view of irregular polygons.
Figure 3. Houlongdongella elevata Cui, 1989 [55] from the Shuijingtuo Formation at the Aijiahe and Wangjiaping sections, Yichang County, Hubei Province, South China. (A) AJH SJT 8-2-3 BK-013, lateral view of right valve, showing subdorsal node, U-shaped sulcus and bulb-like anterior lobe. (B) AJH SJT 8-2-3 BK-013, posteroventral view of right valve. (C) AJH SJT 8-2-3 BK-013, dorsal view of right valve. (D) AJH SJT 8-2-3 BK-013, anteroventral view of right valve. (E) Enlarged polygons with fine ridges on valve surface in A (white frame). (F) AJH SJT S05 BE-016, lateral view of left valve. (G) AJH SJT S05 BE-016, dorsal view of left valve, showing subdorsal node. (H) AJH SJT S05 BE-016, ventral view of left valve. (I) AJH SJT S05 BE-017, enlarged exterior view of irregular polygons. (J) WJP SJT 7 BL-001, anteroventral view of right valve, showing subdorsal node, U-shaped sulcus and bulb-like anterior lobe. (K,L) AJH SJT S05 G017, enlarged exterior view of irregular polygons.
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Chen, F.; Lian, Y.; Wang, Y. New Discovery of Bradoriids from the Lower Cambrian Shuijingtuo Formation in the Eastern Three Gorges Area, South China. Diversity 2025, 17, 719. https://doi.org/10.3390/d17100719

AMA Style

Chen F, Lian Y, Wang Y. New Discovery of Bradoriids from the Lower Cambrian Shuijingtuo Formation in the Eastern Three Gorges Area, South China. Diversity. 2025; 17(10):719. https://doi.org/10.3390/d17100719

Chicago/Turabian Style

Chen, Feiyang, Yucheng Lian, and Yi Wang. 2025. "New Discovery of Bradoriids from the Lower Cambrian Shuijingtuo Formation in the Eastern Three Gorges Area, South China" Diversity 17, no. 10: 719. https://doi.org/10.3390/d17100719

APA Style

Chen, F., Lian, Y., & Wang, Y. (2025). New Discovery of Bradoriids from the Lower Cambrian Shuijingtuo Formation in the Eastern Three Gorges Area, South China. Diversity, 17(10), 719. https://doi.org/10.3390/d17100719

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