Hyaenodontidae

The Hyaenodontidae ("Hyaena teeth") is a family of the extinct order Creodonta, which contains several dozen genera.

The Hyaenodonts were important mammalian predators that arose during the late Paleocene and persisted well into the Miocene.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.  They were more widespread and successful than their sister family, the oxyaenids.Lambert, David and the Diagram Group 1985. The field guide to prehistoric life. Facts on File Publications, New York. 

 General characteristics 
They had long skulls, slender jaws, slim bodies, and a tendency to walk on their toes rather than flat-footed (plantigrade). They ranged in size from 30 to 140 cm at the shoulder. Hyaenodon gigas, the larger species, was as much as 1.4 m high at the shoulder, 10 feet long and weighed about 500 kg, but most were in the 5–15 kg range, equivalent to a mid-sized dog.Egi, Naoko 2001: Body mass estimates in extinct mammals from limb bone dimensions: the case of North American Hyaenodontids. Palaeontology 44 (3): 497-528.  Fossil evidence of their skulls shows that they had a particularly acute sense of smell, while their teeth were adapted for slicing, rather than crushing.

 Teeth 
Hyaenodonts were mainly meat-eaters. They did not crack main bones because they lacked
crushing teeth. This contrasts with modern hyaenas, which can crush bones of larger prey. This gives then a good source of calcium, and access to the highly nutritious bone marrow. Modern bears and dogs also have bone-crushing capability, though not to the same extent as hyaenas. Hyaenodonts thus thus lacked dental versatility  for processing any foods other than meat.

The carnassials in a hyaenodontid are generally the second upper and third lower molars. However, some hyaenodontids had as many as three pairs of carnassials or carnassial-like molar teeth in their jaws.Wang, Xiaoming; and Tedford, Richard H. 2008. Dogs: their fossil relatives and evolutionary history. New York: Columbia University Press, p15/17.

 Life-style 
Because of their size range, it is probable that different species hunted in different ways and 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.

 References 

Category:Creodonts