The ‘Gulliver’ fish fauna of an early Miocene freshwater system of New Zealand; new insights from otoliths from the Bannockburn Formation

ABSTRACT

The early Miocene palaeolake Manuherikia in Central Otago, South Island, New Zealand is a prime source for reconstructing the terrestrial and freshwater biota of past Zealandia. Otoliths of fishes that once lived in this lake system were first described in 2012. Here we report the results of extensive additional sampling resulting in a total of 16,500 fish otoliths from a wide set of stratigraphic levels and environmental settings within the Bannockburn Formation near St Bathans. Six new species are described: Galaxias crassus, Galaxias naviculus, Galaxias nitidus, Galaxias polei, Galaxias tholus, Mataichthys asymmetricus. The entire freshwater otolith-based fish fauna of the Bannockburn Formation now encompasses 17 species, 10 in Galaxiidae, 2 in Prototroctidae and 5 in Eleotridae; all families present in the freshwater systems of New Zealand today.

Correlation with putative related extant taxa reveal that the fishes from the Bannockburn Formation were relatively large, often at the upper margin of the extant sizes of fishes in the respective groups or even larger. This ‘Gulliver’ fish fauna is consistent with other fossil and extant ‘gulliverisms’ observed in various Zealandian biota. Environmental and putative evolutionary explanations, aspects of the taphocoenosis and possible stratigraphic implications of the otolith assemblages are discussed.

KEYWORDS:

• Fossil otoliths
• Galaxiidae
• Eleotridae
• Prototroctidae
• Bannockburn Formation
• palaeolake Manuherikia

Acknowledgements

We thank Euan and Ann Johnstone of Home Hills Station for ongoing logistical support, and them and Tony and Jack Enright of Dunstanburn Station, Southern Lakes Holdings Ltd for access to their land to investigate the fossil deposits from which the otolith faunas derive. We are grateful to many people who helped with the excavations over the years, but the following deserve particular mention: Mike Archer, Suzanne Hand, Aaron Camens, Vanesa De Pietri, Steve Salisbury, Rick Arena, Al Mannering, Jamie Wood, Dave (Pom) Allen and Leigh Love. We thank Jean-Claude Stahl (Museum of New Zealand Te Papa Tongarewa [Te Papa]) for photos of recent otoliths. We further thank our colleagues Andrew Stewart and Carl Struthers from Te Papa and Gerald Allen and Sue Morrison from WAM (Perth) for their support in obtaining relevant extant otoliths for comparison.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Conceptualisation, T.H.W and W.S.; field work, J.P.W., T.H.W., A.J.D.T., R.P.S.; sorting otoliths from matrix—J.P.W. and T.H.W; otolith identification, W.S.; formal analysis, W.S.; methodology, W.S. and T.H.W.; interpretation, W.S., T.H.W., A.J.D.T., R.P.S.; writing—original draft, W.S., T.H.W.; writing—review and editing, W.S., T.H.W., A.J.D.T., R.P.S. All authors have read and agreed to the published version of the manuscript.

Data availability statement

All materials studied, described and figured in this manuscript has been registered and deposited in public institutional scientific collections in New Zealand. All data are contained in the text of the paper with the exception of that for figures 8 and 10 that are in two Supplementary files, which are available in zenodo at https://d oi.org/10.5281/zenodo.7360751

Additional information

Funding

This work was initially supported by the Public Good Science Fund of the New Zealand Foundation for Research, Science and Technology, contract TWOX0201 to T.H.W. and Te Papa’s Collection Development Fund. Subsequently, it was primarily supported by the Australian Research Council Discovery Projects DP0770660 (to Suzanne Hand, Michael Archer) and DP120100486 (to T.H. Worthy, S. Hand, S. Salisbury, R.P. Scofield, and A.J.D. Tennyson) and by the New Zealand Marsden Fund Council from Government funding, managed by the Royal Society Te Apārangi (CTM1601, V. De Pietri, R.P. Scofield). In addition, Te Papa, Canterbury Museum, Flinders University, the University of New South Wales, the University of Queensland, and multiple individual volunteers contributed financial and in-kind support over nearly two decades to the fieldwork leading to this research.