A Late Triassic chimaeroid egg capsule from New Zealand: early evidence of chimaeroid reproductive mode from the eastern margin of Gondwana

Abstract

A Late Triassic chimaeroid egg capsule from the South Island of New Zealand is described as Chimaerotheca reperepe, a new ichnospecies. The fossil egg capsule is preserved as a positive impression on a block of very fine sandstone from the Murihiku Terrane of the South Island, which is dated as Warepan or Otapirian in the local New Zealand stage system, equivalent to late Norian or Rhaetian internationally. The egg capsule impression is spindle-shaped and consists of a narrow flask-like central embryo chamber surrounded by a ribbed membrane, or collarette. Morphologically, the fossil is strikingly similar to egg capsules of the extant chimaeroid Callorhinchus, with which it shares several features in the context of a recent phylogenetic analysis of chondrichthyan egg capsules. The specimen represents the oldest formally described record of a chondrichthyan from New Zealand, and extends the southern Gondwanan fossil record of chimaeroids by approximately 100 million years. In terms of chimaeroid palaeobiology, this fossil occurrence provides clear evidence that Callorhinchus-like chimaeroids have employed a highly conserved reproductive mode throughout at least the last 200-plus million years of the group's history, and further demonstrates that Callorhinchus or a Callorhinchus-like chimaeroid was present by the Late Triassic along the eastern margin of Gondwana.

http://zoobank.org/urn:lsid:zoobank.org:pub:00EC6AB6-263F-4842-AD59-6ECD1E70CD25

Keywords:

• chimaeroid
• egg capsule
• reproduction
• Gondwana
• Triassic
• New Zealand

Acknowledgements

We thank G. Asher, who very kindly brought the specimen to the attention of REF at the University of Otago, and S. Clearwater who found the specimen and passed it to Asher. The late A. Grebneff provided helpful information and insights on the fossil invertebrate fauna from the type locality. F. G. Marx and G. Aguirre read and critiqued the manuscript, which was also improved by helpful comments from J. Kriwet and three anonymous reviewers. MDG conducted research in New Zealand through the generous hospitality of the Department of Geology at the University of Otago, and with travel funding from the College of Natural Science at Michigan State University.