Eriptychius: Middle Ordovician placoderm pre-gnathostome enters the LRT
Very few fish are known from the Middle Orodovician, 450 mya.
Eryptichius (Walcott 1892, Bryant 1946) is one known from scattered bones, here put together for the first time in a tentative reconstruction (Fig 1) based on the bauplan of Early Silurian Xiushanosteus and Late Silurian Bianchengichthys. In the large reptile tree (LRT, 2174 taxa) Given present data, Eryptichius nests between these two – just prior to the advent of jaws.
Digital Graphic Segregation
can also work on diagrams like this (Fig 1). You many not color all items correctly the first time, but patterns will emerge from the apparent chaos and you’ll get it.
Bryant 1936 wrote:
“The discovery of a vertebrate fauna in the Harding Sandstone, of Middle Ordovician age, was announced by Walcott more than forty years ago. Yet they have never been adequately studied and their systematic position has always been uncertain. Eryptichius is closely, and Astraspis more distantly, related to the Drepanaspidae. The body form of these animals is still unknown. One reason for this lies in the fragmentary condition of the fossils.”
References
Bryant WL 1936. A Study of the Oldest Known Vertebrates, Astraspis and Eriptychius. Proceedings of the American Philosophical Society 76 (4): 409-427.American Philosophical Society.
Walcott CD 1892. Preliminary notes on the discovery of a vertebrate fauna in Silurian (Ordovician) strata. Geological Society of America Bulletin 3:153-172.
Source: https://pterosaurheresies.wordpress.com/2022/12/07/eriptychius-middle-ordovician-placoderm-pre-gnathostome-enters-the-lrt/
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