Hyaenodontidae

Hyaenodontidae
Temporal range: Late Paleocene–Late Miocene
Hyaenodon gigas and H. mongoliensis
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Class: Mammalia
Order: †Hyaenodonta
Family: †Hyaenodontidae
Leidy, 1869
Genera

See text

Hyaenodontidae ("hyena teeth") is a family of extinct predatory mammals, and is the type family of the extinct mammalian order Hyaenodonta. Hyaenodontids were important mammalian predators that arose during the late Paleocene and persisted well into the Miocene.[1] They were considerably more widespread and successful than the oxyaenids, the other clade once considered part of Creodonta.[2]

General characteristics

Hyaenodontids of Hyaenodontidae are characterized by long skulls, slender jaws, slim bodies, and a plantigrade stance. They generally ranged in size from 30 to 140 cm at the shoulder.[2] While Hyaenodon gigas, the largest Hyaenodon species, was as much as 1.4 m high at the shoulder, 10 feet long and weighed about 500 kg, most were in the 5–15 kg range, equivalent to a mid-sized dog.[3] The anatomy of their skulls show that they had a particularly acute sense of smell, while their teeth were adapted for shearing, rather than crushing.[2]

Sinopa grangeri

Because of their size range, it is probable that different species hunted in different ways, which allowed them to fill many different predatory niches. Smaller ones would hunt in packs during the night like wolves, and bigger, fiercer ones would hunt alone during the daylight, using their sheer size and their mighty jaws as their principal weapon. The carnassials in a hyaenodontid are generally the second upper and third lower molars. However, some hyaenodontids possessed as many as three sequential pairs of carnassials or carnassial-like molar teeth in their jaws.[4] Hyaenodontids (like all creodonts) lacked post-carnassial crushing molar teeth (such as those found in many carnivoran families, especially the Canidae and Ursidae), and thus lacked dental versatility for processing any foods other than meat.[5]

Hyaenodontids are very unusual in regards to their tooth replacement. Studies on Hyaenodon show that juveniles took 3–4 years in the last stage of tooth eruption, implying a very long adolescent phase. In North American forms, the first upper premolar erupts before the first upper molar, while European forms show an earlier eruption of the first upper molar.[6]

At least one hyaenodontid lineage, Apterodontinae, was specialised for aquatic, otter-like habits.[7]

Range

Having evolved in Africa during the Paleocene,[7][8] hyaenodontids soon after spread into India and Europe, implying close biogeographical connections between these areas.[9] Afterwards they dispersed into Asia from either Europe or India, and finally North America.[10][11]

They were important hypercarnivores in Eurasia, Africa and North America during the Oligocene, but gradually declined, with almost the entire family becoming extinct by the close of the Oligocene. Only four genera, Megistotherium, its sister genera Hyainailouros and Dissopsalis, and the youngest species of Hyaenodon, H. weilini, survived into the Miocene, of which, only Dissopsalis survived long enough to go extinct at the close of the Miocene.[1] Traditionally this has been attributed to competition with carnivorans, but no formal examination of the correlation between the decline of hyaenodontids and the expansion of carnivorans has been reccorded, and the latter may simply have moved into vacant niches after the extinction of hyaenodontid species.

Relations

Hyaenodontids were historically classified in Creodonta, alongside other predatory mammal groups like oxyaenids. The clade has long been assumed to be a wastebasket taxon,[6][7][12][13][14][15] showing a vast variety of clades assumed to be closely related to or ancestral to Carnivora. Indeed, hyaeanodontids are not closely related to other "creodonts," that is, the oxyaenids, which are part of Laurasiatheria - a clade that also includes carnivorans, bats, ungulates and eulipotyphlans, among others.

Genera

Hyaenodon skull
Reconstruction of Hyaenodon by Heinrich Harder
Skull of Apterodon macrognathus

The Machaeroidinae are sometimes placed here, e.g. by Egi, 2001.[3]

References

  1. 1 2 Barry, J. C. (1988): Dissopsalis, a middle and late Miocene proviverrine creodont (Mammalia) from Pakistan and Kenya. Journal of Vertebrate Paleontology 48(1): 25-45.
  2. 1 2 3 Lambert, David and the Diagram Group (1985): The Field Guide to Prehistoric Life. Facts on File Publications, New York. ISBN 0-8160-1125-7
  3. 1 2 Egi, Naoko (2001): Body Mass Estimates in Extinct Mammals from Limb Bone Dimensions: the Case of North American Hyaenodontids. Palaeontology 44(3): 497-528. doi:10.1111/1475-4983.00189
  4. ↑ Wang, Xiaoming; and Tedford, Richard H. Dogs: Their Fossil Relatives and Evolutionary History. New York: Columbia University Press, 2008. p15
  5. ↑ Wang, Xiaoming; and Tedford, Richard H. Dogs: Their Fossil Relatives and Evolutionary History. New York: Columbia University Press, 2008. p15-7
  6. 1 2 Katharina Anna Bastl, First evidence of the tooth eruption sequence of the upper jaw in Hyaenodon (Hyaenodontidae, Mammalia) and new information on the ontogenetic development of its dentition, Paläontologische Zeitschrift (Impact Factor: 1.1). 10/2013; 88:481-494. DOI: 10.1007/s12542-013-0207-z
  7. 1 2 3 Laudet, V.; Grohé, C.; Morlo, M.; Chaimanee, Y.; Blondel, C.; Coster, P.; Valentin, X.; Salem, M.; Bilal, A. A.; Jaeger, J.-J.; Brunet, M. (2012-11-21). "New Apterodontinae (Hyaenodontida) from the Eocene Locality of Dur At-Talah (Libya): Systematic, Paleoecological and Phylogenetical Implications". PLoS ONE. 7 (11): e49054. doi:10.1371/journal.pone.0049054.
  8. ↑ Gheerbrant E, Iarochene M, Amaghzaz M, Bouya B. Geol Mag. 2006;143:475–489.
  9. ↑ Floréal Solé & Thierry Smith, Dispersals of placental carnivorous mammals (Carnivoramorpha, Oxyaenodonta & Hyaenodontida) near the Paleocene-Eocene boundary: a climatic and almost worldwide story, GEOLOGICA BELGICA (2013) 16/4: 254-261
  10. ↑ "HYAENODONTS AND CARNIVORANS FROM THE EARLY OLIGOCENE TO EARLY MIOCENE XIANSHUIHE FORMATION, LANZHOU BASIN, GANSU PROVINCE, CHINA"
  11. ↑ "New Remains of Hyaenodontidae (Creodonta, Mammalia) From the Oligocene of Central Mongolia"
  12. ↑ Morlo, M., Gunnell G., and P.D. Polly. 2009. What, if not nothing, is a creodont? Phylogeny and classification of Hyaenodontida and other former creodonts. Journal of Vertebrate Paleontology 29(Supplement 3): 152A.
  13. ↑ Polly, P.D. 1994. What, if anything, is a creodont? Journal of Vertebrate Paleontology 14(Supplement 3): 42A.
  14. ↑ Polly, P.D. 1996. The skeleton of Gazinocyon vulpeculus gen. et comb. nov. and the cladisitic relationships of Hyaenodontidae (Eutheria, Mammalia). Journal of Vertebrate Paleontology 16: 303–319.
  15. ↑ Grohé et al. 2012
  16. ↑ The Paleobiology Database Hyaenodontidae page
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