St Bathans fauna

The St Bathans fauna is found in the lower Bannockburn Formation of the Manuherikia Group of Central Otago, in the South Island of New Zealand.

It comprises a suite of fossilised prehistoric animals from the late Early Miocene (Altonian) period, with an age range of 19–16 million years ago.

The fossiliferous layer has been exposed at places along the Manuherikia River and at other sites in the vicinity of the historic gold mining town of St Bathans.

The fauna consists of a variety of vertebrates, including fish, a crocodilian, a rhynchocephalian (a relative of tuatara),[3] geckos,[4] skinks,[4] a primitive mammal,[5] several species of bats,[6] and several kinds of birds, especially waterbirds.

The Miocene ecosystem was recovering from the ‘Oligocene drowning’ a few million years earlier, when up to 80% of the current land area of New Zealand was submerged.

The wildlife that lived in, on, and around the palaeolake Manuherikia was uniquely New Zealand, which strongly suggesting that some emergent land remained during this near drowning event.

[9] Marked global cooling and drying during the Miocene, Pliocene and the Pleistocene Ice Ages resulted in the extinction of the 'subtropical' elements of the St Bathans fauna.

Those that survived adapted to the dynamic geological and climatic changes, and would form part of the enigmatic fauna that characterised New Zealand when humans arrived in the late 13th century.

[11] In 2016 Vanesa De Pietri was awarded a Royal Society of New Zealand Marsden Fast Start grant to study the shorebird fossils.

[15] The latter is represented by several bones and egg shells of currently unnamed species, but already identifiable as true moa, being large sized and flightless.

[21] Charadriiformes, including gulls, terns, noddies, snipes, dotterels, plovers, jacanas, oystercatchers, sheathbills and the plains-wanderer, are a large group of birds that are mostly found in marine or semi-marine environments.

[26] The vast majority of the bones excavated from St Bathans are those of freshwater fish such as the ancient relatives of today's bullies, galaxiids, and the extinct New Zealand grayling.

[28] Notable examples of absent taxa include marsupials, snakes, agamid and varanid lizards, lungfish, eels, cockatoos, and all but one lineage (bellbirds and tūī) of the 80 species of Australian honeyeaters.