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Paleontological Research
Abstract
Abstract.
The fossil record of brittle stars, one of the five extant classes of echinoderms, is still rather poorly known. In particular for the Triassic Period, occurrences published to date are strongly biased toward Europe, with only two exhaustively described taxa recorded from the East Asian part of the Tethys Ocean. Here, we record new ophiuroids from the Carnian (Upper Triassic) of the Me area in Ninh Binh Province, Vietnam. The fossils comprise articulated disks and arm fragments preserved as external molds, all original calcite dissolved. We introduce a new genus and species, Triadoleucella meensis, for these specimens that represent the oldest known member of the order Ophioleucida. The ophiuroids were found in mudstones deposited in outer shelf environments below storm wave base. The intact articulation, combined with random orientation and intense fragmentation of individuals suggest effective burial by downslope mudflow prior to or soon after death.
We wish to thank Hung Ba Nguyen (Vietnam National Museum of Nature, Hanoi) for his assistance in the geological survey. John W. M. Jagt (Natuurhistorisch Museum, Maastricht, the Netherlands) and Andreas Kroh (Natural History Museum Vienna, Austria) greatly improved an earlier draft of this manuscript. This study was financially supported by Grants-in-Aid for Scientific Research (KAKENHI) from the Japan Society for the Promotion of Science (19K04059 to T. K.) and Sakura Science Exchange Program, JST (S2019F0531337 to T. K., H. T. T. and Y. I., and by the Project for Collecting Paleontological Specimens in Vietnam (BSTMV.28/15-18 to H. T. T. and H. D. D.).
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