Creodonta

Creodonta
Creodonta
Temporal range: Late Paleocene to Late Miocene, 63.3–11.1 Ma
Sarkastodon
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Eutheria
Superorder: Laurasiatheria
Order: Creodonta
(Cope, 1875)
Families

Hyaenodontidae
Oxyaenidae

The creodonts are an extinct order of mammals that lived from the Paleocene to the Miocene epochs. They shared a common ancestor with the Carnivora.

Creodonts were an important group of carnivorous mammals from 55 to 35 million years ago in the ecosystems of Africa, Eurasia and North America. In Oligocene Africa, they were the dominant predatory group. They competed with the Mesonychids and the Entelodonts and ultimately outlasted them by the start of the Oligocene and by the middle of the Miocene respectively, but lost ground to the carnivorans. The last genus went extinct 8 million years ago, and carnivorans now occupy their ecological niches.

Contents

Evolution and taxonomy

Creodonts were traditionally considered ancestors to Carnivora, but are now considered to have shared a common ancestor further back - possibly a Cimolesta such as Cimolestes. They share with the Carnivora the carnassial shear, a modification of teeth that evolved to slice meat in a manner like scissors and gave both orders the tools to dominate the niche. 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.[1] Creodonts were the dominant carnivorous mammals from 55 to 35 million years ago, peaking in diversity and prevalence during the Eocene.[1] By the mid Oligocene, Creodonts supplanted both the Mesonychids, and giant flightless predatory birds entirely in North America, Eurasia and Africa, and in turn, competed with their own relatives, the Carnivorans. The last genus, Dissopsalis, went extinct about 8 million years ago.

Habitat

The creodonts ranged across North America, Eurasia and Africa, in forms that resemble those of some modern carnivores. Amongst their number was Sarkastodon, one of the largest mammalian land predators of all time, weighing an estimated 800 kg[2]. Their dominance over the early Carnivora, known as miacids, began to wane after 35 million years ago. The creodonts survived until 8 million years ago; the last form, Dissopsalis, died out in Pakistan. Bears, cats, mustelids, hyenas, canids such as wolves and other Carnivora now occupy the former creodont niches.

Reasons for extinction

Skull of Hyaenodon

It is not known exactly why the creodonts were replaced by Carnivora. It may be because of their smaller brains and their locomotion, which was somewhat less energy-efficient (especially while running).[3] Their limb structure limited leg movement to a vertical plane, as in horses; they were unable to turn their wrists and forearms inward to trip, slash, or grab prey as modern carnivores can. Creodonts had to depend entirely on their jaws to capture prey, which may be why most creodonts had much larger heads than carnivores of the same body size. The creodont lumbosacral spine was not arranged as efficiently for running as in Carnivora. The arrangement of the teeth was also somewhat different. In the miacids (and so 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. These limits may have created important disadvantages over millions of years.

In the most strictly carnivorous family of modern Carnivora, the Felidae, 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.

Footnotes

  1. ^ a b Lambert, 162
  2. ^ Sorkin, B. 2008: A biomechanical constraint on body mass in terrestrial mammalian predators. Lethaia, Vol. 41, pp. 333–347
  3. ^ "The Elements of Geology". Globusz. http://www.globusz.com/ebooks/Geology/00000034.htm. Retrieved March 11, 2008. 

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

Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Creodonta — Saltar a navegación, búsqueda ? Creodontos Rango fósil: Paleoceno Plioceno …   Wikipedia Español

  • creodontă — CREODÓNTĂ, creodonte, s.f. (La pl.) Subordin fosil de mamifere primitive carnivore, cu dentiţia puţin specializată, cu membrele masive, prevăzute cu gheare; (şi la sg.) mamifer din acest subordin. [pr.: cre o ] – Din fr. créodontes. Trimis de… …   Dicționar Român

  • Creodonta — Créodontes …   Wikipédia en Français

  • Creodonta — Urraubtiere Lebendrekonstruktion von Hyaenodon (Gemälde von Heinrich Harder, entstanden um 1920) Zeitraum Paläozän bis Miozän Fossilfundorte …   Deutsch Wikipedia

  • Creodonta — Hyaenodontidae Oxyaenidae Los Creodontos (orden Creodonta, literalmente dientes carniceros ) son un antiguo grupo de mamíferos extintos que en su momento de mayor explendor se convirtieron en el principal grupo de vertebrados depredadores. En su… …   Enciclopedia Universal

  • Creodonta — …   Википедия

  • Creodonta — ▪ fossil mammal order       order of extinct, primitive carnivores first found as fossils in early Tertiary deposits of Mongolia (the Tertiary Period lasted from 66.4 to 1.6 million years ago). The creodonts evolved from Late Cretaceous mammals… …   Universalium

  • Creodonta — Creodọnta,   Creodọnti|er, ältere, von E. D. Cope geprägte Bezeichnung für eine Gruppe fossiler primitiver Säugetiere mit raubtierartig differenziertem Gebiss (»Urraubtiere«), die außer den raubtierähnlichen Hyaenodonta auch Urhuftiere umfasst …   Universal-Lexikon

  • creodonta — cre·o·don·ta …   English syllables

  • creodonta — ˌkrēəˈdäntə noun plural Usage: capitalized Etymology: New Latin, from cre + odonta : a suborder of extinct primitive mammals (order Carnivora) showing relationship to the early ungulates and known from fossil remains in Eocene and Oligocene… …   Useful english dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”