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| Lihuacaris ferox Jiao, Pates, Lerosey-Aubri, Ortega-Hernández, Yang, Lan & Zhang, 2021 |
Abstract
Stem-group euarthropods are important for understanding the early evolutionary and ecological history of the most species-rich animal phylum on Earth. Of particular interest are fossil taxa that occupy a phylogenetic position immediately crownwards of radiodonts, for this part of the euarthropod tree is associated with the appearance of several morphological features that characterize extant members of the group. Here, we report two new euarthropods from the Cambrian Stage 4 Guanshan Biota of South China. The fuxianhuiid Alacaris? sp. is represented by isolated appendages composed of a gnathobasic protopodite and an endite-bearing endopod of at least 20 podomeres. This material represents the youngest occurrence of the family Chengjiangocarididae, and its first record outside the Chengjiang and Xiaoshiba biotas. We also describe Lihuacaris ferox gen. et sp. nov. based on well-preserved and robust isolated appendages. Lihuacaris ferox exhibits an atypical combination of characters including an enlarged rectangular base, 11 endite-bearing podomeres and a hypertrophied distal element bearing 8–10 curved spines. Alacaris? sp. appendages display adaptations for macrophagy. Lihuacaris ferox appendages resemble the frontal appendages of radiodonts, as well as the post-oral endopods of chengjiangocaridid fuxianhuids and other deuteropods with well-documented raptorial/predatory habits. Lihuacaris ferox contributes towards the record of endemic biodiversity in the Guanshan Biota.
Keywords: Deuteropoda, Euarthropoda, Fuxianhuiida, Lihuacaris ferox, Radiodonta, Chengjiango, carididae
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| Figure 2. Locality maps showing occurrences of known Guanshan biotas in South China, and stratigraphic succession of the Cambrian (Stage 4) Lihuazhuang section in Yiliang, Yunnan. (a) Studied area in South China. (b) Location of 13 sites where fossil assemblages assigned to the Guanshan Biota have been recovered. (c) Enlarged area from (b), showing the location of the Lihuazhuang section in Yiliang. (d) Stratigraphic column showing the occurrence of fossils reported in this study. Figure reproduced from [Jiao, et al., 2021]: figure 1, licensed under CC BY 4.0. |
Systematic palaeontology
SUPERPHYLUM Panarthropoda Nielsen [1995]
ORDER Fuxianhuiida Bousfield [1995]
FAMILY Chengjiangocarididae Hou and Bergström [1997]
Type genus. Chengjiangocaris Hou & Bergström [1991]
Other genera included. Alacaris Yang, Ortega-Hernández, Legg, Lan, Hou & Zhang [2018]
Alacaris Yang, Ortega-Hernández, Legg, Lan, Hou & Zhang [2018]
Alacaris? sp.
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| Figure 6. Lihuacaris ferox nov. gen et sp. from the Cambrian (Stage 4) Guanshan Biota, Yunnan, China. YKLP 12438, holotype, an isolated appendage preserved laterally compressed. (a) Overview of slab showing appendage and associated with euarthropod tergites. (b, c) Details of appendage. (d, e) Details of rectangular structure which is overlain by the large base of the appendage. Abbreviations: ba, large rectangular base; de, distal element; em?, possible extensor muscle; en, endite; gn, gnathobase; pd, podomere; te, tergite; 1–8 indicate spines on distal element, numbered from proximal to distal. |
Incertae sedis
GENUS Lihuacaris gen. nov.
Type species. Lihuacaris ferox gen. et sp. nov.
Diagnosis. Arthropodized elongate appendage composed of a rectangular base, proximal relative to 11 tall rectangular podomeres and a long subtriangular distal element; podomeres increase in length distally, alternate with triangular articulating membranes and bear small triangular endites (one pair per podomere) that insert at the midpoint of ventral margin; distal element bears 8–10 robust curved ventral spines that increase in size towards the distal end of the appendage.
Etymology. Concatenation of the first part of the name of the section where the fossils were found (Lihuazhuang), and the Latin ‘caris’ (or Greek ‘καρις’), meaning ‘crab’ or ‘shrimp’, a suffix commonly used for euarthropods.
Type material. Holotype: YKLP 12438 (figure 6), a complete appendage preserved as a lateral compression; Paratype: YKLP 12439 (figure 7a), an incomplete appendage missing the base and proximalmost six podomeres, preserved as a lateral compression.
Additional material. Four partial specimens YKLP 12440–12443 (figure 7b–e).
Type locality and horizon: Lihuazhuang section, locality ca 2.5 km southeast of the Lihuazhuang village (figure 2). Lower part of Wulongqing Formation, Cambrian Stage 4, Palaeolenus biozone [Hu, et al., 2010].
Lihuacaris ferox sp. nov.
Etymology. From ferox (Latin = ferocious) in reference to the inferred predatory habits of this animal.
Conclusion:
The endemic taxa Alacaris? sp. and Lihuacaris ferox increase the known diversity of euarthropods in the Guanshan Biota. Alacaris? sp., the second fuxianhuiid reported from this exceptional biota, represents both the first occurrence of the Chengjiangocarididae in these beds and the youngest record of this fuxianhuiid family to date. The exact affinities of the new taxon Lihuacaris ferox are uncertain, but it most likely falls close to radiodonts in the euarthropod stem-lineage, or possibly fuxianhuiids as early members of Deuteropoda. Additional material of Lihuacaris ferox is critical for clarification of its relationships with other stem-group euarthropods and may potentially inform on the sequence of evolution of fundamental euarthropod characters.
Appendages of Lihuacaris ferox appear adapted for capturing non-biomineralized prey. This allows predatory habits to be inferred for this enigmatic taxon and suggests that radiodonts were not the only large predators in the Guanshan Biota. The appendages of Alacaris? sp. feature gnathobasic protopodite indicative of macrophagous feeding habits. The endemism of all these taxa probably reflects the relatively proximal shelf depositional settings of the Guanshan Konservat-Lagerstätte [Jiao, et al., 2021].
De-Guang Jiao, Stephen Pates, Rudy Lerosey-Aubri, Javier Ortega-Hernández, Jie Yang, Tian Lan and Xi-guang Zhang. 2021. New Multipodomerous Appendages of Stem-group Euarthropods from the Cambrian (Stage 4) Guanshan Konservat-Lagerstätte. Royal Society Open Science. DOI: 10.1098/rsos.211134
