| “บีเวอร์สยาม” Steneofiber siamensis|
reconstruction by Namosaurus
Today and in the Tertiary, the geographical distribution of castorids is limited throughout all of the northern continents. Fossils of the Castoridae genus Steneofiber are abundant in many localities of Eurasia from the late Oligocene to Pliocene period. Recently, Steneofiber fossils were discovered in two localities of northern Thailand, Mae Moh and Chiang Muan coal mines, in layers of late middle Miocene age. These discoveries represent the first records of castorids from Southeast Asia and correspond to their southernmost known range. The focus of this study is to describe this new Thai species of Steneofiber and to define its wear stages from the molar occlusal surfaces by using micro-CT scan analysis. The CT scan technique permits the analysis of the virtual occlusal surface changes from wear, allowing easier comparison to related species of Steneofiber cheek teeth without destroying the teeth. The new species, Steneofiber siamensis n. sp., can be distinguished from the other species of Steneofiber by several distinct characters, longer mesostriid on p4, presence of premesostria and metastria on P4, which are smaller than most of the other known species. The occurrence of this new castorid also supports a subtropical to tropical paleoclimate for these two localities of northern Thailand.
Keywords: Steneofiber, Castoridae, Micro CT scan, Late middle Miocene, Thailand
|Steneofiber siamensis fossils discovered from the late middle Miocene of Mae Moh and Chiang Muan coal mines, northern Thailand|
Class MAMMALIA Linnaeus 1758
Order RODENTIA Bowdich 1821
Family CASTORIDAE Hemprich 1820
Subfamily CASTORINAE Hemprich 1820
Genus Steneofiber Geoffroy 1833
Suraprasit, Chaimanee, Martin & Jaeger 2011
Type locality: “I”coal layer, Mae Moh coal mine, Lampang province, Thailand.
Etymology: In relation to its geographical origin, Siam being the former name of the Kingdom of Thailand
Suraprasit, K., Y. Chaimanee, T. Martin, and J. -J. Jaeger. 2011. First Castorid (Mammalia, Rodentia) from the middle Miocene of Southeast Asia. Naturwissenschaften. 98(4):315-28. DOI: dx.doi.org/10.1007/s00114-011-0769-0
by กันตภณ สุระประสิทธิ์ | http://geothai.net/gneiss/?p=3023