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WHILE MANY NICHES are ever-present in vertebrate-dominated ecosystems, sometimes we find an extinct group that was unique in some way. At various times in the past carnivores have evolved saber-teeth, but currently there are no saber-toothed predators (although the clouded leopard may be working on it). In a previous post I mentioned Simocyon, a cursorial generalized carnivore that retained arboriality in order to escape from larger predators, including the saber-toothed cats. Today I will write about Thylacoleo carnifex, the so-called marsupial lion.
SCIENCE MAGAZINE has a busy day today. Appearing in the current issue are two important articles.
I PREVIOUSLY POSTED on this topic but the author of the article objected, feeling that his copyright had been violated. Unfortunately he has been unforthcoming about his specific objections and how I could correct the post, so I decided to write a second version. It is possible that my first post may have violated copyright by covering too much information. As I was writing my goal was to do the paper justice. It was the culmination of years of research, and is preceded by multiple other articles. It may be that in trying to be correct and thorough I included too much information. In this rewrite I have omitted a good deal of information and brought in a variety of other sources to cover the geography of the region.
WILL BAIRD of Dragon’s Tales posted Wednesday on the topic of dicynodonts, complete with artistic renditions. He mentions the last dicynodont fossil known showed up in the early Cretaceous, and speculates some might have survived to the end of the Cretaceous. Too bad they couldn’t make it to the present day! Since these creatures were a branch on the line to mammalian evolution, retain features of our therapsid ancestors, and are long extinct I think there are a lot of paleontologists and evolutionary biologists out there who would sacrifice various body parts if it would enable us to find a living example. I’m not even a paleontologist and I’d consider giving up a little toe.
THERE ARE certain niches that seem to be filled by one species or another at any time period. In my recent post on mammalian evolution, for instance, I mentioned Castorocauda, a Jurassic mammaliform that seems to have fit into the niche now occupied by beavers or otters. But occasionally we run across an animal that seems to be adapted for a unique role in its ecosystem. One of these animals is Simocyon. This is a puma-sized caniform that lived about 14 million years ago, and died out by four million years ago. Simocyon has a variety of unusual adaptations.
ALL SABER-TOOTH and big cat fans should step over to Tetrapod Zoology, where Darren Naish reports on the Big Cats in Britain conference. The first part of this two-part survey discusses the possible late survival of Homotherium latidens, a saber-toothed cat, as well as extinct leopards and lions. The second talks about extinct pumas in Europe and cheetahs in America, geographical distributions that we are not accustomed to for these cats.
ORIGINALLY PEOPLE thought that the long canines of saber-toothed cats were intended to pierce the thick skin of mammoths and were used to inflict gaping wounds. However, recent modeling suggests that repeated biting of struggling prey would result in breaking the saber-cats’ teeth, and that the fangs were used in a single neck bite on pinned prey, severing major blood vessels and quickly resulting in death.1 As the other two major groups of saber-tooth carnivores, Nimravidae and Barbourofelidae, have been extinct for millions of years, we will probably have to determine their diet based upon deduction. Fortunately the saber-toothed felids have been extinct for only tens of thousands of years, which is practically yesterday! We have some evidence of their diet in a cave that served as den for Homotherium and in the bones of Smilodon preserved in the La Brea tar pits.
I MENTIONED in a recent post that 75% of all of the types of mammals that have ever lived are now extinct. We have a tendency to think of extant organisms as all there is. We know dinosaurs once lived and are now extinct, but you’d be hard-pressed to get the average person to name one major extinct non-dinosaurian group. Yet we don’t have to look very far into our own past to find many of them.
YESTERDAY I posted about the evolution of mammals from synapsids, which definitely were not “mammal-like reptiles”! Long before the mammals appeared the therapsids descended from basal synapsids. These animals were highly successful during the Permian, and if they had not been almost eradicated by the Permian-Triassic extinction the dinosaurs might never have had their chance at preeminence. Blogger Will Baird, who dropped by to read that article, has published on his blog an excellent overview of the gorgonopsids, a group of robust carnivorous therapsids.
You can read more about the gorgonopsids and other therapsids in Gorgon: Paleontology, Obsession, and the Greatest Catastrophe in Earth’s History. While Ward unfortunately does spend more time talking about himself than I’d like, he also devotes a lot of time to these carnivores, the alien ecosystem they inhabited, and the catastrophe that brought about their extinction.
TODAY I WAS poking about at Bone Clones (their slogan is “Only Mother Nature Does it Better”, but I think it should be “Because Everyone Should Have a Replica of the Skull of a Conquistador Who Took an Axe to the Brain“) and found a beautiful replica of a nimravid skull, namely Dinictis.
Nimravid's Weblog 