Joined: Nov. 2006
|Quote (Wesley R. Elsberry @ July 28 2007,06:19)|
It is really very curious - (speaking about Australian/Tasmanian/NZ versus Europian/American fauna) that natural selection could lead to striking similarity of placental and marsupial wolf (convergence).
The convergence seems only to have influenced the gross morphology needed in common for running terrestrial predators, and we know via biophysics why that sort of thing happens. It is not curious at all that the dictates of physics has an influence on what happens via natural selection.
Beyond that, placental wolf and thylacine differ in the coloration, as Patrick pointed out; in cranial morphology; in dental formula; and in behavior; as well as the obvious difference in reproductive systems.
I would say that convergence influnced at most the shape of skulls. Placental and marsupial sabre-toothed tigers had very similar skulls. The same is valid for thylacinus/placental wolf. According Dawkins it is not easy to tell them apart. You have to know their dental formulas or to know that there are two holes in the palate bone. At least students at Oxford found it not so easy to tell them apart, I quote Dawkins The Ancestor tale:
Zoology students at Oxford had to identify 100 zoological specimens as part of the final exam. Word soon got around that, if ever a 'dog' skull was given, it was safe to identify it as Thylacinus on the grounds that anything as obvious as a dog skull had to be a catch. Then one year the examiners, to their credit, double bluffed and put in a real dog skull. The easiest way to tell the difference is by the two prominent holes in the palate bone, which are characteristic of marsupials generally.
The question is if such similarities are caused by natural selection or by other (pre-programmed) forces.
I could not answer, but should maintain my ground.-