Family Tragulidae

The Tragulidae (chevrotains; 3 Genera, 4 species) are small, reclusive, forest-dwelling, deer-like ruminants. The lesser Malay chevrotain is the smallest species in Ruminantia, which has a mass of 0.7-8.0 kg and a shoulder height of 20-35 cm.

Tragulidae belong to the headgear-less paraphyletic stemgroup "Tragulina" and the males have evolved developed canine teeth, which exposed to form tusks. Tragulidae are the most primitive of all living families and have changed little morphologically over evolutionary history; this has led them to being called "living fossils". Their primitiveness is demonstrated by their 1) very simple social behavior, 2) retention of a gallbladder and appendix, 3) lack of a true omasum, and 4) possession of many skeletal characters.

Using fossil calibrations, we estimated the emergence of Tragulidae at ~36 Mya. Most members of the Tragulidae inhabit tropical forests in southeast Asia, but a single species is found in central and western Africa. Tragulidae are exclusively browsers, which innately prefer browse such as fruits, shoots, and leaves, typically from shrubs, forbs, and trees. This family has no domestic animals.

References  

1. Hackmann T J, Spain J N. Invited review: ruminant ecology and evolution: perspectives useful to ruminant livestock research and production.[J]. Journal of Dairy Science, 2010, 93(4):1320-1334.
2. Hernández F M, Vrba E S. A complete estimate of the phylogenetic relationships in Ruminantia: a dated species-level supertree of the extant ruminants[M]. 2005.
3. Hofmann R R. Evolutionary steps of ecophysiological adaptation and diversification of ruminants: a comparative view of their digestive system[J]. Oecologia, 1989, 78(4):443-457.
4. Davis E B, Brakora K A, Lee A H. Evolution of ruminant headgear: a review[J]. Proceedings Biological Sciences, 2011, 278(1720):2857-2865.
5. http://www.ultimateungulate.com/ungulates.html

The Tragulidae Family Tree