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31 March 2011 Fish Remains, Mostly Otoliths, from the Non-Marine Early Miocene of Otago, New Zealand
Werner Schwarzhans, R. Paul Scofield, Alan J.D. Tennyson, Jennifer P. Worthy, Trevor H. Worthy
Author Affiliations +
Abstract

Fish remains described from the early Miocene lacustrine Bannockburn Formation of Central Otago, New Zealand, consist of several thousand otoliths and one skeleton plus another disintegrated skull. One species, Mataichthys bictenatus Schwarzhans, Scofield, Tennyson, and T. Worthy gen. et sp. nov., an eleotrid, is established on a skeleton with otoliths in situ. The soft embedding rock and delicate, three-dimensionally preserved fish bones were studied by CT-scanning technology rather than physical preparation, except where needed to extract the otolith. Fourteen species of fishes are described, 12 new to science and two in open nomenclature, representing the families Galaxiidae (Galaxias angustiventris, G. bobmcdowalli, G. brevicauda, G. papilionis, G. parvirostris, G. tabidus), Retropinnidae (Prototroctes modestus, P. vertex), and Eleotridae (Mataichthys bictenatus, M. procerus, M. rhinoceros, M. taurinus). These findings prove that most of the current endemic New Zealand/southern Australia freshwater fish fauna was firmly established in New Zealand as early as 19–16 Ma ago. Most fish species indicate the presence of large fishes, in some cases larger than Recent species of related taxa, for instance in the eleotrid genus Mataichthys when compared to the extant Gobiomorphus. The finding of a few otoliths from marine fishes corroborates the age determination of the Bannockburn Formation as the Altonian stage of the New Zealand marine Tertiary stratigraphy.

Introduction

New Zealand is the emergent part of a continental fragment termed Zealandia that is separated from Australia to the west by at least 1600 km of ocean. The Tertiary fossil record of the terrestrial and freshwater biota of Zealandia is depauperate, with the first and only window to the terrestrial biota being afforded by the St Bathans Fauna from late early—middle Miocene Manuherikia Group in Central Otago, New Zealand (Fig. 1; Worthy et al. 2007). Vertebrates were first noticed in these strata by Douglas et al. (1981) and the fauna is now known to contain a diverse terrestrial biota that includes crocodilians, lizards, more than 35 taxa of birds, and mammals (Molnar and Pole 1997; Worthy et al. 2006, 2007, 2008, 2009, 2010a, b; Hand et al. 2007; Jones et al. 2009; Lee et al. 2009; Scofield et al. 2010; Tennyson et al. 2010). Although the St Bathans Fauna was deposited in a lacustrine setting, work to date has concentrated on the terrestrial fauna. Among the vertebrates, the fossil assemblage is dominated by fish remains, including numerous disarticulated bones and otoliths, mostly sagittae. Identification of the diversity and identity of these fishes has significance for understanding the overall palaeoecological setting in which the St Bathans Fauna was deposited. In this paper, a first attempt at this is made by surveying the diversity of otoliths in the fauna and an articulated otolith-bearing fish is described.

Institutional abbreviations.—AMS, Australian Museum, Sydney, New South Wales, Australia; BMNH, Natural History Museum, London, United Kingdom; NIWA, National Institute of Water and Atmosphere, New Zealand; NMNZ, Museum of New Zealand Te Papa Tongarewa (formerly National Museum of New Zealand), Wellington, New Zealand; SAMA, South Australian Museum, Adelaide, South Australia, Australia; SMF, Senckenberg Museum, Frankfurt/Main, Germany; WAM, Western Australian Museum, Perth, West Australia, Australia; ZMH, Zoological Museum, Hamburg, Germany; ZMUC, Zoological Museum, Copenhagen, Denmark.

Fig. 1.

Location maps with a palaeogeographic reconstruction of Zealandia in the early Miocene to show the location of Lake Manuherikia. A. Location map of New Zealand. B. Location of Lauder Site and the St Bathans area in Otago with the location sites indicated. C. Detailed map of the St Bathans area. The location map is derived from Worthy et al. (2007) and the palaeogeographic reconstruction is modified from that given for 20 Ma by Bunce et al. (2009).

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Other abbreviations.-CaL, cauda length; OH, otolith height; OL, otolith length; OsL, ostium length; OT, otolith thickness; SL, standard length, SuL, sulcus length; TL, total length. Roman numbers in fin ray counts refer to spinous rays, Arabic numbers to soft rays.

Geological setting

Sedimentology

The Lake Manuherikia freshwater fish fossils reported here derive from the Miocene Bannockburn Formation sediments deposited into the palaeolake Manuherikia. This lake covered an area of about 5600 km