Megaconus

Megaconus is an extinct genus of allotherian mammal from the Middle Jurassic Tiaojishan Formation of Inner Mongolia, China. The type and only species, Megaconus mammaliaformis was first described in the journal Nature in 2013. Megaconus is thought to have been a herbivore that lived on the ground, having a similar posture to modern-day armadillos and rock hyraxes. Megaconus was in its initial description found to be member of a group called Haramiyida. A phylogenetic analysis published along its description suggested that haramiyidans originated before the appearance of true mammals, but in contrast, the later description of the haramiyidan Arboroharamiya in the same issue of Nature indicated that haramyidans were true mammals. If haramiyidans are not mammals, Megaconus would be one of the most basal ("primitive") mammaliaforms to possess fur, and an indicator that fur evolved in the ancestors of mammals and not the mammals themselves. However, later studies cast doubt on the euharamiyidan interpretation, instead finding it to be a basal allotherian mammal. Based on the melanosomes preserved in its fur, Megaconus likely had a uniformly dark-brown coloration, similar to that of other early mammaliaforms including Arboroharamiya and Vilevolodon.

==Description== Megaconus is one of the few early mammaliaforms known from a complete skeleton. The skeleton includes both the jaw bones and the teeth, which are the most informative features because they allow for comparisons with other mammaliaforms known only from dental features. Megaconus has a dentition similar to those of rodents, with large incisors at the front of the jaws and broad molars in the back. One distinguishing feature of Megaconus is a pair of enlarged premolar teeth in the lower jaw. The teeth of Megaconus have many cusps, allowing them to interlock tightly when the jaws are closed. If Megaconus is a non-mammalian mammaliaform, it is one of the most basal mammaliaforms to possess such complex teeth.