Yaviichnus inyooensis: A new complex burrow system from the Oligocene of southern Mexico.
[sciencythoughts.blogspot.com]
The behavior of burrowing has probably been present in Mammals since their early origins. Soil provides physical protection; it also supports Plants and Animals that many fossorial Mammals use. Underground shelter provides two main services: protection from predators and from environmental fluctuations or extreme conditions predominating above the ground. It is assumed that subterranean Mammals exploited the underground ecotope during the global climatic transition from the middle Eocene to the early Oligocene. There are several early Oligocene localities in temperate North America, but the only reported Oligocene Mammalian locality from tropical North America is Santiago Yolomecatl in southern Mexico. It includes a few fossorial taxa, such as the Amphisbaenian, Rhineura, as well as three Rodents, the Gophers, Gregorymys veloxikua, Gregorymys sp. and a member of the extinct Florentiamyidae. Several specimens of Gregorymys veloxikua and Gregorymys sp. had been collected inside burrows, which were tentatively identified as belonging to the ichnogenus Alezichnos; however, further detailed study on these burrows suggested that these structures were much more complex than Alezichnos.