aun es un misterio… mas de 100 años de biologia moderna no han podido solucionar esta interrogante… me avisan por interno que unos de los tantos nuevos fondecyt del rayo sera sobre este tema
A male Paradise Tanager (Tangara chilensis) flaunts it, San Diego Zoo, CA, USA
(photo: Nathan Rupert)
Oh look everybody… it’s a Crown Jellyfish (Netrostoma sp.)
see more jellies here:
* Western Africa, up to 14 inches in length (males larger than females). omnivorous, but primarily insectivorous.
Procoptodon - The giant short faced kangaroo
Mounted skeleton on display at Victoria Fossil Cave, Naracoorte Caves National Park, South Australia
Reconstruction by Peter Trusler.
When: Pleistocene (~ 2 million to 15,000 years ago)
Where: Throughout Australia
What: Procoptodon is a giant fossil kangaroo. Exactly how ‘giant’ it is has been a bit exaggerated, heights of up to 10 feet (~3 meters) have been reported, but this would have been its maximum height when it reared up fully on its hind legs, with its arms reaching up for high branches. Procoptodon was capable of this posture, but (like living kangaroos) it did not stand fully upright most of the time. In its normal feeding (and most everything else) poster it would have stood about 6.5 feet (~ 2 meters) tall; about the same height as the largest of the modern red kangaroos. Procoptodon was not the same size as these animals though, it was much more massive and would have been over twice the weight of a red kangaroo of equivalent height.
Procoptodon was very well adapted for the semiarid conditions that characterized much of Australia during the Pleistocene, but fossil remains have also been found in the more hospitable regions of prehistorical Australia. The marsupials of Australia are well known for their convergence evolution upon forms from other continents (such as the tasmanian tiger and the marsupial mole), but the kangaroo does not look like any placental mammal known. However, in terms of its lifestyle, the ecological niche that it inhabits, the group is convergent upon hoofed animals, such as deers! Procoptodon overlapped with human habitation of Australia, and it is thought some Aboriginal folktales are about this massive kangaroo.
Procoptodon is a member of the group Sthenurinae - the shortfaced kangaroos. As you probably guessed these kangaroos had much shorter snouts than the modern species of kangaroos. This group is completely extinct. It is one of the subgroups of the Macropodidae, the clade of marsupials that contains all kangaroos and wallabies, as well as a few other groups. It has been proposed that within the Macropodidae the closest living relative of Procoptodon is the Banded hare-wallaby, though this is not universally accepted.
In the prehistoric outback Procoptodon would have co-exsited with the largest marsupial of all time Diprodoton and was a hunted by the marsupial lion Thylacoleo. And the second link you can see this marsupial predator hunting a close relative of Procoptodon!
Fossil specimen on display at the American Museum of Natural History
Reconstruction by Hirokazu Tokugawa
When: Permian (~299 to 265 million years ago)
Where: North America
What: Cotylorhynchus is a member of one of the most basal groups of synapsids, the Caseidae. Cotylorhynchus was a herbivore, and reached lengths of up to 20 feet (~6 meters) long, with a massive barrel chest, putting weight estimates at around 2 tons. This animal is very large for its time… well at least its body is. Cotylorhynchus has one of the most extreme cases of ‘tiny head’ I have ever seen. Even more so than the sail-backed Edaphaosaurus! Which is closer to modern mammals than Cotylorhynchus is. It is one of the most primitive animals known that unambiguously falls on the synapsid lineage. It is so basal that it does not even have any differentiation seen in its dentition, though there are less teeth than found in the non synapsid contemporaries of this wee-headed creature.