Creodonta
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 Hyaenodon gigas
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The creodonts are an extinct order of mammals that lived from the Paleocene to the Pliocene epoch.
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[edit] Evolution and Taxonomy
Creodonts were previously considered ancestral to the carnivores, Carnivora, but are now considered to have shared a common ancestor further back. Some researchers argue that the creodonts represent a group of mammals of diverse biological ancestry that resemble one another via convergent evolution, rather than being the descendants of a single common ancestor. Their origins lie at least as far back as the late Cretaceous, though they did not radiate much until the Cenozoic. (Lambert, 162)
Creodonts were the dominant carnivorous mammals from 55 to 35 MYA, peaking in diversity and prevalence during the Eocene. (Lambert, 162) They share with the Carnivora the carnassial shear, scissor teeth that evolved to slice meat and gave both orders the tools to dominate the niche.
[edit] Habitat
The creodonts ranged across North America, Eurasia and Africa, in forms that resemble those of modern carnivores. Amongst their number was Megistotherium, which some argue was the largest mammalian land predator of all time, the size of a bison and with a skull twice as big as a tiger's. Megistotherium may have rivaled Andrewsarchus mongoliensis in size. Their dominance over the early Carnivora, known as miacids, began to wane after 35 MYA. The creodonts survived until 8 million years ago; the last form, Dissopsalis, lived in Pakistan. Bears, cats, mustelids, canids such as wolves and other Carnivora now occupy the former creodont niches.
[edit] Why did creodonts become extinct?
It is not known exactly why the Creodonts were replaced by Carnivora. The Creodonts' smaller brains and plantigrade locomotion[citation needed] somewhat less energy-efficient especially while running, may have given the Carnivora a subtle advantage that over millions of years allowed them to take over. In addition, the arrangement of the teeth was somewhat different. In the miacids (and thus in the modern Carnivora), the last upper premolar and the first lower molar are the carnassials, allowing grinding teeth to be retained behind for feeding on non-meat foods (the Canidae are the closest modern analog to miacid dentition). In creodonts, the carnassials were further back - either first upper and second lower molars, or second upper and third lower molars. This committed them to eating meat almost exclusively.
Note that in the Felidae, the most strictly carnivorous of modern Carnivora, the second and third molars have disappeared completely, and the first upper molars behind the carnassials have become vestigial. Modern cats thus eat plant food only incidentally.
[edit] References
- The Velvet Claw: A Natural History of the Carnivores, David Macdonald, BBC Books, ISBN 0-563-20844-9
- David Lambert and the Diagram Group. The Field Guide to Prehistoric Life. New York: Facts on File Publications, 1985. ISBN 0-8160-1125-7
