Genyornis

Genyornis Temporal range: Late Pleistocene
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	†Gastornithiformes
Family:	†Dromornithidae
Genus:	†Genyornis
Species:	†G. newtoni
Binomial name
†Genyornis newtoni Stirling & A. H. C. Zietz, 1896[1]

Genyornis newtoni, also known as thunder bird and mihirung paringmal (meaning "giant bird"), was a large, flightless bird that lived in Australia around 50,000 years ago, along with other species of megafauna.^[2] Over two metres in height, they were likely either omnivorous or herbivorous. They became extinct between 30,000 and 5,000 years ago.^[3] Many other species became extinct in Australia around that time, coinciding with the arrival of humans. Their closest living relatives are fowl.

Taxonomy[]

The species was first described in 1896 by Edward Charles Stirling and A. H. C. Zietz, the authors giving the epithet newtoni for the Cambridge professor Alfred Newton. The name of the genus is derived from ancient Greek terms referring to the lower jaw and a bird. The type specimen is a left femur.^[1][4] The type locality is Lake Callabonna in South Australia. The excavation was undertaken and described by Zietz. A description of the excavation was reported in Nature^[5][6] which had also unearthed material recognised as marsupials. Numerous fragments of avian fossils were noticed in the clay surrounding the removal of diprotodont fossils, then largely complete specimens including crucial evidence of the crania emerged from the site. The paper reviewed previously described fossil remains of "struthious [ostrich-like] birds in Australia", which had either been assigned to the ancient emus of Dromaius or the only described species of Dromornis, D. australis Owen.^[1]

A letter from George Hurst concerning the discovery of a partial skeleton of the species alerted Stirling to its existence in 1893.^[4]

The placement of this dromornithid species may be summarised as:

Dromornithidae (8 species in 4 genera)^[7]

• Dromornis
• Barawertornis
• Ilbandornis P. Rich, 1979
• Genyornis

• Genyornis newtoni Stirling & A. H. C. Zietz, 1896

Description[]

Genyornis newtoni was a medium size dromornithid with a robust body. While larger than Ilbandornis species, it did not attain the height and weight of Dromornis stirtoni or Dromornis planei. The fossils of the species have been found remaining in articulation; no other dromornithid species has been discovered in this state. The remains of eggs have also been attributed to this species. Gastroliths belonging to these animals have been found alongside their remains, a feature that has revealed the sometimes shallow site of fossils.^[4]

Distribution[]

This mihirung has been found at sites in South Australia, New South Wales, Queensland and Western Australia. The temporal distribution is during the Pleistocene. Genyornis newtoni is the only species to have been identified as extant in this later period, 1.4 mya to about 10000 years ago, several other dromornithids appear in records from the earlier Pliocene period.^[4]

Decline[]

Two main theories propose a cause for megafauna extinction - human impact and changing climate. A study has been performed in which more than 700 Genyornis eggshell fragments were dated.^[8] Through this, it was determined that Genyornis declined and became extinct over a short period—too short for it to be plausibly explained by climate variability. The authors considered this to be a very good indication that the entire mass extinction event in Australia was due to human activity, rather than climate change. A 2015 study collected egg shell fragments of Genyornis from around 200 sites that show burn marks.^[9] Analysis of amino acids in the egg shells showed a thermal gradient consistent with the egg being placed on an ember fire. The egg shells were dated to between 53.9 and 43.4 thousand years before present, suggesting that humans were collecting and cooking Genyornis eggs in the thousands of years before their extinction. A later study, however, suggests that the eggs actually belonged to the giant malleefowl, a species of extinct megapode.^[10][11]

In May 2010, archaeologists announced the rediscovery of an Aboriginal rock art painting, possibly 40,000 years old, at the Nawarla Gabarnmung rock art site in the Northern Territory, that depicts two of the birds in detail.^[12] Late survival of Genyornis in temperate south west Victoria has also recently been suggested, based on dateable Aboriginal traditions.^[13]

Fossil evidence suggests that the population of Genyornis at Lake Callabonna died out as the lake dried up as the climate changed and became drier. The birds recovered from the site also seemed to have been particularly prone to osteomyelitis as a result of getting stuck in the mud of the drying lake bed as the water receded. Eventually, when the lake dried, the population was left without their main source of water and subsequently died out.^[14]

References[]