Il blog dedicato ai Paleontologi !!!!

2008-12 – L’antenato nano dei Koala (Koala dwarf ancestor)

Koala expert shoots down dwarf theory

By Dani Cooper for ABC Science Online

Posted December 16, 2008 08:39:00
Updated December 16, 2008 08:57:00

Australia’s iconic koala is not a dwarf and the finding has major implications for theories on what happened to the continent’s prehistoric megafauna, a Queensland palaeontologist says.

Dr Gilbert Price, of the University of Queensland’s Centre for Microscopy and Microanalysis says there has been a long-held view that modern koalas were a dwarf version of the giant prehistoric koala that lived between 30,000 and 700,000 years ago.


However, in a paper published in Quaternary Science Reviews, Dr Price says modern koalas are a separate species that at times co-existed with the late Pleistocene giant Phascolarctos stirtoni, which weighed between 20 and 30 kilograms.

Dr Gilbert used improved dating techniques to analyse fossils and found that between 300,000 and 500,000 years ago the two koala species were both living in Australian trees.

“It’s fascinating that up until fairly recently in geological terms we did have two types of koalas kicking around,” he said.

“The fossil records do suggest that they lived in the same place at the same time; [perhaps] there is something about their sizes that allowed them to fill a slightly different ecological niche.

“The big question is why one koala species survived past 50,000 years ago and the other didn’t make it.”


Unknown ancestor


Dr Gilbert says understanding this may help prevent the modern-day koala from becoming extinct.

However, he says a lack of well-dated fossil records makes it difficult to determine the true ancestor of the modern koala.

He says his finding also suggests that the debate about why Australia’s megafauna became extinct need to be revisited.

“My work shows we’ve got to sort out this dwarfing hypothesis first,” he said.

The “dwarfing hypothesis” was originally developed to explain the body-size relationship between extinct Pleistocene mammalian megafauna and smaller-sized, similar-looking, modern-day animals, Dr Gilbert said.

It has been applied to other present-day Australian mammals including the grey kangaroo, tasmanian devil and the koala.

Dr Gilbert says the dwarfing phenomena has been used to support opposing megafauna extinction theories.

He says on one side, dwarfing is viewed as the result of a physiological response to climate-induced changes in habitat and food supplies, while the opposite view holds that it was human induced through targeting of larger animals in hunting.

However, Dr Gilbert says his study shows that dwarfing itself “has not been fully tested”.

“A combination of more intensive physical dating, better stratigraphic control in regard to collecting methodologies, and up-to-date taxonomic information is critical for testing such hypotheses,” he writes.

“Until such information becomes available an understanding of the fate of many late Pleistocene forms, and the origins of many extant taxa, will remain elusive.”



dicembre 31, 2008 - Posted by | - Marsupiali, 1, P - Evoluzione, Paleontology / Paleontologia | ,

Non c'è ancora nessun commento.


Inserisci i tuoi dati qui sotto o clicca su un'icona per effettuare l'accesso:


Stai commentando usando il tuo account Chiudi sessione /  Modifica )

Google+ photo

Stai commentando usando il tuo account Google+. Chiudi sessione /  Modifica )

Foto Twitter

Stai commentando usando il tuo account Twitter. Chiudi sessione /  Modifica )

Foto di Facebook

Stai commentando usando il tuo account Facebook. Chiudi sessione /  Modifica )


Connessione a %s...

%d blogger hanno fatto clic su Mi Piace per questo: