Hyolithid-like hyoliths without helens from the early Cambrian of South China, and their implications for the evolution of hyoliths

Autor: Fan Liu, Christian B. Skovsted, Timothy P. Topper, Zhifei Zhang
Jazyk: angličtina
Rok vydání: 2022
Předmět:
Zdroj: BMC Ecology and Evolution, Vol 22, Iss 1, Pp 1-15 (2022)
Druh dokumentu: article
ISSN: 2730-7182
DOI: 10.1186/s12862-022-02022-9
Popis: Abstract Background A small hyolith, with a triangular operculum and a conical-pyramidal conch with a sharp apex, originally documented as Ambrolinevitus ventricosus, is revised based on new material from the Chengjiang biota. The operculum of ‘Ambrolinevitus’ ventricosus displays strong morphological similarities with the operculum of Paramicrocornus from the Shuijingtuo Formation (Cambrian Series 2), indicating that the species should be reassigned to Paramicrocornus. Results Based on the unusual morphology of Paramicrocornus, we herein propose a new family Paramicrocornidae fam. nov. A cladistic analysis of Cambrian and Ordovician hyoliths clearly delineates hyolithids as a monophyletic group which evolved from the paraphyletic orthothecids in the early Cambrian and with Paramicrocornidae as its closest relative. Conclusions The phylogenetic analysis, together with the distribution of hyoliths from the Cambrian to the Ordovician, reveals the presumptive evolution model of both the skeleton and soft-part anatomy of hyoliths. The Family Paramicrocornidae plays an intermediate role in hyolith evolution, representing the transitional stage in the evolution from orthothecids to hyolithids.
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