The specimen for this Fossil Friday is the left lower jaw (dentary) of a juvenile anthracothere Arretotherium meridionale. Anthracotheres were considered an extinct family of artiodactyls, however new phylogenetic evidence suggests that one of its subfamilies might be be related to hippopotamids, commonly called hippos, which are alive today. This specimen is a member of that subfamily, called Bothriodontinae. This specimen was found in the upper Las Cascadas formation in Panama and is likely from the late Arikareean NALMA. It is the first member of the anthracothere family to be found in Central America. The specimen can be distinguished as a juvenile because the dentary still has some of the deciduous (milk) teeth.
If you want to read more about this specimen, read the publication about it here: http://www.tandfonline.com/doi/pdf/10.1080/02724634.2013.722573.