St Bathans fauna

Palaeontologists sieving St Bathans fossils in the Manuherikia River

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 layer in which the fossils are found derives from littoral zone sediments deposited in a shallow, freshwater lake, with an area of 5600 km2 from present day Central Otago to Bannockburn and the Nevis Valley in the west; to Naseby in the east; and from the Waitaki Valley in the north to Ranfurly in the south. The lake was bordered by an extensive floodplain containing herbaceous and grassy wetland habitats with peat-forming swamp–woodland.[1] At that time the climate was warm with a distinctly subtropical Australian climate[2] and the surrounding vegetation was characterised by casuarinas, eucalypts and palms as well as podocarps, araucarias and southern beeches.

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.[7] Of tree-dwelling birds, parrots outnumber pigeons thirty to one.[8] Proapteryx, a basal form of kiwi, is known from there. 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.[10]

  1. ^ Worthy, Trevor H.; Tennyson, Alan J. D.; Jones, C.; McNamara, J. A.; Douglas, B. J. (2007). "Miocene waterfowl and other birds from central Otago, New Zealand". Journal of Systematic Palaeontology. 5 (1): 1–39. Bibcode:2007JSPal...5....1W. doi:10.1017/S1477201906001957. hdl:2440/43360. ISSN 1477-2019. S2CID 85230857.
  2. ^ Worthy, Trevor (Jan–Feb 2011). "Deep secrets". New Zealand Geographic. Retrieved 2019-11-15.
  3. ^ Jones MEH; Tennyson AJD; Worthy JP; Evans SE; Worthy TH (2009). "A sphenodontine (Rhynchocephalia) from the Miocene of New Zealand and palaeobiogeography of the tuatara (Sphenodon)". Proceedings of the Royal Society B. 276 (1660): 1385–1390. doi:10.1098/rspb.2008.1785. PMC 2660973. PMID 19203920.
  4. ^ a b Lee Michael S. Y.; Hutchinson Mark N.; Worthy Trevor H.; Archer Michael; Tennyson Alan J. D.; Worthy Jennifer P.; Scofield R. Paul (2009-12-23). "Miocene skinks and geckos reveal long-term conservatism of New Zealand's lizard fauna". Biology Letters. 5 (6): 833–837. doi:10.1098/rsbl.2009.0440. PMC 2827994. PMID 19656857.
  5. ^ Cite error: The named reference :10 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference :11 was invoked but never defined (see the help page).
  7. ^ Scofield, R. Paul; Worthy, Trevor H. & Tennyson, Alan J.D. (2010). "A heron (Aves: Ardeidae) from the Early Miocene St Bathans Fauna of southern New Zealand". In W.E. Boles & T.H. Worthy. (eds.). Proceedings of the VII International Meeting of the Society of Avian Paleontology and Evolution. Vol. 62. pp. 89–104. doi:10.3853/j.0067-1975.62.2010.1542. {{cite book}}: |journal= ignored (help)
  8. ^ Cite error: The named reference dove was invoked but never defined (see the help page).
  9. ^ Worthy, Trevor H.; Pietri, Vanesa L. De; Scofield, R. Paul (2017-07-03). "Recent advances in avian palaeobiology in New Zealand with implications for understanding New Zealand's geological, climatic and evolutionary histories". New Zealand Journal of Zoology. 44 (3): 177–211. doi:10.1080/03014223.2017.1307235. ISSN 0301-4223. S2CID 90635192.
  10. ^ Cite error: The named reference :7 was invoked but never defined (see the help page).