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| Nailiana elegans Ou & Shu, in Ou, Shu, Zhang, Han, ... et Mayer, 2022. |
Public summary:
• Polypoid animal from early Cambrian of China is a stem-group anthozoan cnidarian
• Anthozoan ancestor inferred to be soft-bodied, solitary polyp of octoradial symmetry
• The new anthozoan provides the oldest direct evidence of macrophagous predation
• Macrophagous predation may have triggered complex food webs in early Cambrian
Cnidarians diverged very early in animal evolution; therefore, investigations of the morphology and trophic levels of early fossil cnidarians may provide critical insights into the evolution of metazoans and the origin of modern marine food webs. However, there has been a lack of unambiguous anthozoan cnidarians from Ediacaran assemblages, and undoubted anthozoans from the Cambrian radiation of metazoans are very rare and lacking in ecological evidence. Here, we report a new polypoid cnidarian, Nailiana elegans gen. et sp. nov., represented by multiple solitary specimens from the early Cambrian Chengjiang biota (∼520 Ma) of South China. These specimens show eight unbranched tentacles surrounding a single opening into the gastric cavity, which may have born multiple mesenteries. Thus, N. elegans displays a level of organization similar to that of extant cnidarians. Phylogenetic analyses place N. elegans in the stem lineage of Anthozoa and suggest that the ancestral anthozoan was a soft-bodied, solitary polyp showing octoradial symmetry. Moreover, one specimen of the new polyp preserves evidence of predation on an epifaunal lingulid brachiopod. This case provides the oldest direct evidence of macrophagous predation, the advent of which may have triggered the emergence of complex trophic/ecological relationships in Cambrian marine communities and spurred the explosive radiation of animal body plans.
Key words: cnidarian phylogeny, stem-group anthozoan, metazoan evolution, macrophagous predation, Cambrian animal food webs
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| Figure 1. Early Cambrian Nailiana elegans gen. et sp. nov. (A) Two specimens preserved on the same slab and designated, respectively, as the holotype (ELEL-SJ080824-1) and paratype (ELEL-SJ080824-2). (B) Counterpart of the holotype (lateral view), showing eight slender, prehensile tentacles (numbered) and the column with fine longitudinal grooves. (C) Interpretive drawing of the holotype. (D) Close-up of the paratype (oblique oral view), showing the elevated mouth region (arrowheads), oral disc, and eight tentacles. (E) Close-up of the holotype. co, column; fg, fine longitudinal grooves; od, oral disc; te, oral tentacles. Scale bars, 5 mm in (A–C, E) and 2 mm in (D). |
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| Figure 3. Interpretive reconstruction and inferred phylogenetic position of Nailiana elegans gen. et sp. nov. (A) Reconstruction of N. elegans capturing a lingulid brachiopod (artwork by Xi Liu). (B) Summary of metazoan phylogeny derived from Bayesian analyses of 126 characters and 42 taxa under Mkv + Γ model (see Figure S6 and Text S4 for details). Numbers at nodes indicate posterior probabilities. N. elegans is resolved as a stem-group anthozoan. Cambrian problematica Xianguangia, Daihua, and Dinomischus are basal among the Cnidaria. Neuralia, Bilateria, Nephrozoa, Protostomia, and Deuterostomia are monophyletic. Animal silhouettes by courtesy of PhyloPic (www.phylopic.org). |
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| Reconstruction of Nailiana elegans gen. et sp. nov. capturing a lingulid brachiopod (artwork by Xi Liu). |
Phylum Cnidaria Verrill, 1865
Class Anthozoa Ehrenberg, 1834
Nailiana elegans Ou et Shu gen. et sp. nov.
Etymology. The generic name honors the first author's grandmother, Nailian Fu (1912–2009), in memory of her benignity and elegance. In addition, “nailian,” lotus-like in Chinese, alludes to the overall appearance of the new taxon. The gender is feminine. The specific name refers to the graceful body shape of the new taxon.
Referred material. A total of 15 specimens (Table S1) housed in the Early Life Evolution Laboratory, China University of Geosciences, Beijing, China. Two individuals (ELEL-EJ080482-1, 2) preserved on the same slab are herein designated as the holotype and paratype specimens, respectively.
Horizon and locality. All specimens were collected from the Eoredlichia-Wutingaspis Biozone in the Yu'anshan Member of the Heilinpu Formation (Cambrian series 2, stage 3) in the Huaguoshan section at Erjie, Yunnan, southern China.
Diagnosis. Polypoid body entirely soft. Oral end exhibits a central mouth and circular oral disc surrounded by a whorl of eight long, unbranched, flexible tentacles. Columnar trunk highly extensible, exhibiting closely spaced, fine longitudinal grooves and stripes on the surface. Aboral end blunt or pointed.
Qiang Ou, Degan Shu, Zhifei Zhang, Jian Han, Heyo Van Iten, Meirong Cheng, Jie Sun, Xiaoyong Yao, Rong Wang and Georg Mayer. 2022. Dawn of Complex Animal Food Webs: A New Predatory Anthozoan (Cnidaria) from Cambrian. The Innovation. 3(1); 100195. DOI: 10.1016/j.xinn.2021.100195
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