Leptaucheniinae

Leptaucheniinae ("Delicate Necks") was a taxon of small, goat-like oreodonts with proportionally big heads found throughout North America during the Late Oligocene. Because skeletons of Leptauchenia and Sespia have been found by the literal thousands, they are often quoted as being the most numerous fossil mammals in North America during the Late Oligocene.^[1][2] They had high-crowned, hypsodont teeth which were used to chew gritty vegetation.

Leptaucheniinae Temporal range: Late Oligocene
Leptauchenia decora
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Artiodactyla
Family:	†Merycoidodontidae
Subfamily:	†Leptaucheniinae
Genera
† Leptauchenia † Sespia

Because the eyes and nostrils were placed high on the head, it was long assumed that Leptauchenia and Sespia were aquatic, or semi-aquatic animals. However, because their fossils have never been found in floodplain deposits or river channels, and their plague-like abundance in fossil sand dunes, Donald Prothero suggests that they were desert-dwelling animals.^[3] According to Prothero's interpretation, the high-placed eyes and nostrils served to filter out sand while burrowing.

References

1. San Diego Natural History Museum "Fossil Mysteries Field Guide: Sespia californica
2. Prothero, D.R. (2006). After the Dinosaurs: The Age of Mammals. Indiana University Press. ISBN 0-253-34733-5.
3. Prothero, D. R., and F. Sanchez. 2005. Review of the leptauchenine oreodonts (Mammalia: Artiodacttyla). New Mexico Museum of Natural History and Science Bulletin.