Mammal family tree in disarray too?
|August 8, 2013||Posted by News under Tree of life, News|
Were we mentioning that the fabled Darwinian tree of life is now widely thought to be like a contentious wiki page?
Well, the fur is flying among mammals too. The Scientist now tells us, “Fossils Snarl Mammalian Roots: Two newly discovered Jurassic-era fossils suggest drastically different mammalian origins”:
Because of their rodent-like teeth, some researchers have linked haramiyids to multituberculates, a group of ancient mammals. Describing Arboroharamiya, a short-faced, tree-dwelling animal, Jin Meng from the American Museum of Natural History (AMNH) and his colleagues suggest that haramiyids are indeed related to multituberculates, suggesting that mammals may have originated in the late Triassic, more than 200 million years ago.
Meanwhile, a team led by the University of Chicago’s Zhe-Xi Luo depict Megaconus, a terrestrial haramiyid with a primitive jaw and ankle that does not appear related to multituberculates. Compared with the Arboroharamiya fossil, the Megaconus specimen is consistent with a much more recent origin of mammals—around 176 million to 161 million years ago.
Here’s Nature on the same subject:
“It’s remarkable, for such an incredibly obscure group, to have two fairly complete skeletons pop up at the same time,” says Richard Cifelli, a vertebrate palaeontologist at the Oklahoma Museum of Natural History in Norman, who co-authored a related News & Views3. “These new fossils change everything.”
Makes one wonder whether it would be more or less confusing if we knew more. Things can go either way.
But there’s another possibility, says Guillermo Rougier, a vertebrate palaeontologist at the University of Louisville in Kentucky. Megaconus and Arboroharamiya “have been assigned to the same group, but they’re very different creatures,” he says. Indeed, he adds, Arboroharamiya, the more advanced of the two species in terms of its jawbone and other features, may actually belong in a long-successful but now-extinct group of mammals called multituberculates — a realignment that would explain the disparity between family trees drawn up by these individual studies.
What does “more advanced” mean in the context? We thought evolutionary biologists weren’t supposed to talk in terms like that. It implies goals of evolution, and you can only have advances if you have goals.
It’s revealing that people in a mess like this continue to coerce agreement from the public and suppress dissent among peers.