15 Crikey! Lake crocodilian from Central Otago
Sauropsida, Crocodilia
The first fossil crocodilian to be described from Aotearoa New Zealand is a small dark fragment of jaw from Early Miocene lake sediments in Central Otago. The specimen was found by Mike Pole near St Bathans during a study of fossil plants from Central Otago, and was described by Ralph Molnar and Mike Pole in 1997. While the fossil has been described, the genus and species to which it is belongs have not yet been formally identified.
Bone from the lower jaw of an unidentified species of crocodilian (specimen OU 22228). Image credit: RE Fordyce. |
The St Bathans fossil fragment is a little less than 7 cm long and is from the right lower jaw of a small crocodile. Given the proportions of the jaw in modern crocodiles, the original lower jaw was perhaps 20 cm long and the animal probably had a skull of a similar length. A Pleistocene fossil crocodilian from Fiji Volia athollandersoni was around two to three metres long and may have been a similar size to the specimen from St Bathans.
The crocodilian lower jaw came from the Bannockburn Formation. Fossils from Bannockburn Formation include freshwater mussels (Hyridella), abundant fish remains including isolated bones and otoliths (See: Robinson’s pilchard: the importance of earbones), bones of many species of ducks, shelducks and geese, and broken eggshell. Plant fossils are abundant in places and algal stromatolites or oncolites are known (See: Small boulders of fossil bacteria). The strata were deposited in an extensive shallow “Lake Manuherikia” which occupied much of what is now Central Otago.
The animal to which the jaw fragment belonged was possibly a member of the Mekosuchinae group of crocodilians. Mekosuchines are a distinct and extinct group of crocodiles first recognised in Australia and now known from other localities including Fiji (e.g. Volia athollandersoni), New Caledonia and Vanuatu. Mekosuchines originated at least 53 million years ago during the early Eocene and lived through to the Holocene. At least one mekosuchine crocodile from Vanuatu apparently co-existed with humans only a few thousand years ago.
Mekosuchines dispersed across oceans through the southwest Pacific. Judging from the known distribution of other mekosuchines in space and time, these animals could have lived in New Zealand either intermittently or continuously; an open question in New Zealand paleontology.
The St Bathans crocodilian jaw is currently on loan to Tūhura Otago Museum in Ōtepoti Dunedin where it can be seen in the Southern Land, Southern People gallery, along with many other specimens from the University of Otago Geology Museum.
—Written by R. Ewan Fordyce, with additional contributions by Daniel B Thomas
| Specimen number: OU 22228 | Age: 19 to 16 million years old (early Miocene, Altonian Stage) |
| Locality: St Bathans, Central Otago | Rock Formation: Bannockburn Formation |
| Collected by: M Pole | |
| Citation: Molnar RE, Pole M. 1997. A Miocene crocodilian from New Zealand. Alcheringa 21:65–70. doi.org/10.1080/03115519708619185 | |
Evidence of life from a past geological age. Remains like bones, shells or wood, or an impression like a footprint, or some other evidence of life, from something that was alive more than 11,700 years ago.
The general term for the group of reptiles that includes all living species of crocodile, alligator, caiman and gharial. Crocodilians are also all of the extinct species that are more closely related to living crocodiles, alligators, caimans and gharials than they are to any other group.
23.03 million to 15.97 million years ago. The Early Miocene is a sub-epoch that spans the international Aquitanian and Burdigalian stages.
The taxonomic rank that groups together closely related species. The genus forms the first part of the binomial species name.
One or more populations of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring. In paleontology, a species is often considered a lineage of organisms that maintains its identity over time and space.
2.58 to 0.0117 million years ago.
Poorly bedded, light green to brown siltstones and mudstones.
Sometimes called 'earbones', but more correctly termed 'ear stones', these are accumulations of calcium carbonate minerals in the base of the skull of many vertebrates that help to provide a sense of movement and maintain balance.
56.0 to 48.07 million years ago. The late Eocene is more formally known as the international Ypresian Stage.
11,700 years ago to present.
See: Tūhura Otago Museum, Southern Land, Southern People.
