And I'm not even including the ones that show exceptional preservation, like the ichthyosaur fossils I mentioned in a post a couple of days ago, that were so well preserved that they could even determine features like countershading. Ordinary fossils contain a wealth of information about the organisms they came from -- if you know where to look, and how to interpret it.
Take, for example, the paper by a team from the University of Bristol and the University of Uppsala that appeared last week in the journal Alcheringa: An Australasian Journal of Paleontology. Conducted by Christine Janis, Adrian O'Driscoll, and Benjamin Kear, the study analyzed the bones of prehistoric kangaroos, and reached a rather startling conclusion: a good many ancient kangaroo species didn't have the group's signature hop.
The determination came from looking at the strength and articulation of the leg bones, as well as the animal's overall size. In particular, the short-faced kangaroos, or sthenurines, may have preferred to walk on all fours -- or might even have had a bipedal stride like a human.
The skeleton of Simosthenurus occidentalis, which I find vaguely terrifying. [Image licensed under the Creative Commons Ghedoghedo, Simosthenurus occidentalis, CC BY-SA 3.0]
You can see why they're called short-faced kangaroos in the artist's recreation of Procoptodon goliah below, in which I notice two things:
- These creatures looked like a cross between a bunny rabbit and Godzilla.
- The woman posing next to it has a stance like a Glamour magazine model, which is an odd thing to do if you're confronted with an eight-foot-tall kangaroo with giant claws. Me, I'd be running like hell, if I didn't just wet my pants and then faint.
The striding kangaroos seem to have split off from the hopping kind about fifteen million years ago, during the Miocene Epoch, when Australia was a lot wetter than it currently is. The climate back then would have favored large herbivores like the sthenurines (thank heaven these things weren't carnivorous), and they simply became too heavy to jump efficiently. Even smaller sthenurines, though, had a different leg articulation -- they all appear to have been walkers rather than hoppers.
The last of the striding kangaroos went extinct during the last Ice Age, when the climate took a turn toward more arid conditions. Aridity meant fewer plants, and slower growth for the ones that survived, and the largest marsupials in Australia died out.
Just as well. Even the kangaroos that are left can kick you into the middle of next week; every year people, mostly stupid tourists, are injured by kangaroos. Australians also have to contend with the various venomous snakes, spiders, and jellyfish, a relative of the nettle (the gympie-gympie) whose spines inject a neurotoxin that causes intense pain for years, and a highly-aggressive bird called the cassowary that looks like the bastard child of a turkey and a velociraptor. The last thing those poor people need is giant kangaroo-bunnies striding around like they own the place.
Because the kangaroo-bunnies probably were vicious. Down there, it's kind of an inevitability.