New occurrence of fossil loveniid echinoids from Taiwan with both internal and external moulds

Abstract

Taphonomy plays a crucial role in shaping the fossil record and thereby influencing broader interpretations of evolution, biodiversity and palaeoecology. However, its effects on echinoderm taxonomy are seldom considered. Here, we report new fossil loveniid echinoids from the Late Miocene of Taiwan, represented by both external and internal moulds that exhibit markedly different morphologies. The external moulds display the typical diagnostic features of the genus Breynia, whereas the internal moulds lack the inner fasciole and possess pore pairs fully developed to the apical system, making them resemble Spatangomorpha, a fossil genus currently treated as in need of re-description. However, by comparing the fossil internal moulds with the internal surface of skeletons of modern Breynia species, we found that their morphologies closely resemble each other, indicating that the fossils are indeed Breynia species but reflect the preservation of the internal surface of the skeletons. Our results demonstrated that taxonomically important traits of echinoids such as fascioles and pore pairs may be different in internal mould preservation. This case study highlights that relying solely on preserved internal moulds or steinkerns can lead to taxonomic misidentification of fossil echinoids, which may be generally applicable to other biomineralised fossils.