Otoliths in situ in the stem teleost Cavenderichthys talbragarensis (Woodward, 1895), otoliths in coprolites, and isolated otoliths from the Upper Jurassic of Talbragar, New South Wales, Australia

ABSTRACT

Cavenderichthys talbragarensis (Woodward, 1895) is a common signature freshwater stem teleost in the Upper Jurassic of Australia. Our discovery of numerous otoliths in the Talbragar Fish Bed establishes Cavenderichthys as only the second known Jurassic teleost and the third known stem teleost with otoliths in situ and provides an important calibration point for the interpretation of isolated Mesozoic otoliths. It corroborates the low degree of morphological diversification of stem teleost otoliths. The abundance of otoliths (isolated, in coprolites and in situ) allows the mapping of ontogenetic effects and of intraspecific variability for the first time in attributable stem teleost otoliths. Here, we describe 284 otoliths, mostly from Cavenderichthys. Otoliths in situ in Cavenderichthys document the presence of sagitta, lapillus, and asteriscus. Three other, much rarer otolith types were also found that have a teleost otolith pattern more primitive than that of Leptolepidiformes; the origin of these is unknown, but it is likely that they stem from pholidophoriform fishes of the family Archaeomenidae. If confirmed, this otolith pattern would provide a further highly diagnostic and synapomorphic character to define teleosts at the level of the Leptolepidiformes and above. Different mineral replacement processes in fossils from the Talbragar Fish Bed aided us in finding many otoliths, particularly otoliths in situ. Given their abundance and distinct preservation, it is surprising that otoliths in the Talbragar Fish Bed have not been recognized before.

ACKNOWLEDGMENTS

We thank N. McGrath (landholder) and M. Sharp (Head Ranger, National Parks and Wildlife Services, Mudgee, New South Wales) for access to the site; R. Beattie for organizing field work; R. Pogson, M. McCurry (both Australian Museum, Sydney, New South Wales), and Y.-Y. Zhen (Geological Survey of New South Wales, Londonderry, New South Wales) for providing access to specimens in their care and help with the registration and export of newly discovered specimens (M. McCurry also discovered an interesting in situ otolith); S. McClusky (Australian National University, Canberra, Australian Capital Territory) for aerial maps of the site; J. Long (Flinders University, Adelaide, South Australia) for helpful comments and encouragement; R. Oberprieler (Commonwealth Scientific and Industrial Research Organisation, Canberra, Australian Capital Territory) for helpful discussions and a critical reading of the manuscript; and K. Mills (University of Canberra, Canberra, Australian Capital Territory) for finding many of the otoliths that are featured in this publication. We thank A. Tintori (University of Milan, Milan, Italy) and an anonymous reviewer for their constructive criticism on an earlier version of the manuscript.

ORCID

Werner W. Schwarzhans http://orcid.org/0000-0003-4842-7989

Timothy D. Murphy http://orcid.org/0000-0002-4539-3667

Michael Frese http://orcid.org/0000-0002-1059-2375