Quaternary Mexican mammals database
|Category||Paleontology and Stratigraphy|
|Location||International Geological Congress,oslo 2008|
|Author||Arroyo-Cabrales, Joaquin۱; Polaco, Oscar J.۱; Johnson, Eileen۲|
|Holding Date||03 September 2008|
A decade ago, the creation of a bibliographic-based database on the Mexican Quaternary mammals was undertaken in order to secure a comprehensive listing of all of the mammals known at the time when humans appeared in México.
Since then, a large database has been developed that includes records for more than 800 localities and nearly 2400 revised documents. An outstanding characteristic is that this database is electronically related to two major databases, the time-related FAUNMAP and the space-related Atlas Mastozoológico de México. The time range represented is Late Pleistocene to Early Holocene, and primarily Rancholabrean faunas.
Early and Middle Pleistocene sites are scarce. The database has 15,087 mammal records, representing 13 orders, 44 families, 146 genera and 286 species. A third of these taxa no longer occur in Mexican territory, either because they are extinct (almost 30%) or because their distribution no longer extends into the country (9 taxa, 3.1%).
The order Notoungulata is extinct World-wide, while Proboscidea no longer exist in the Americas and neither do the families Herpestidae and Equidae. Three families have been extirpated from North America (Camelidae, Hydrochoeridae and Megalonychidae), and five families are extinct (Gomphotheridae, Mammutidae, Glyptodontidae, Megatheriidae and Mylodontidae). Of the 146 genera, 27 are extinct (18.6%) and nine are considered extirpated (6.2%); at the species level, 84 are extinct (29.4%) and nine are extirpated from the country.
During the Late Pleistocene, changing landscapes were brought about due to repeated events of glaciation–deglaciation. Those conditions fostered the presence of mammalian megaherbivores and megacarnivores that strongly impacted the landscape. The few interactions between extinct animals and humans mostly involved mammoth. In such cases, humans may have been more scavengers than active hunters.
Based on this database, studies on particular groups (proboscideans, horses, lagomorphs, xenarthrans) have been undertaken, as well as specific searches for several particular taxa for either geographic records or dating. For example, both the Pleistocene ursines and large felids are quite diverse. For the bears, the extinction and extirpation of species may be due to several causes, including depletion or extinction of large herbivores, diminishing nutritional quality of plants during climate change, and competition by human for food resources.
For the cats, the southward shift of the jaguar is of note and its displacement most likely is a response to climate change. The most dramatic impact is the disproportionate removal of large species from the felid guild. Their demise is probably a direct result of elimination of their primary prey, the megaherbivores. Two projects have been initiated on absolute dating for several sites. Forthcoming analyses include a monographic study of the overall mammal fauna, and use of the data in GARP modeling.