Tombaatar sabuli is a recently-discovered multituberculate mammal from late Cretaceous sediments of Mongolia. Multituberculates (including Kryptobaatar) are a group of extinct mammals known from the Jurassic to the Eocene in North America and Asia. They are believed to have been herbivorous or omnivorous, and adaptations in their dentition is somewhat convergent upon that of rodents. Specifically, multituberculates are characterized by loss of the canines, having multi-cuspid molars, and one pair of lower incisors.
Although the exact placement of Multituberculata within Mammalia is under dispute, multituberculates are generally believed to fall outside Theria. Within multituberculates, cladistic analyses place Tombaatar as the sister taxon to Catopsbaatar within Djadochtatheria, the clade that contains all of the Mongolian late Cretaceous multituberculates except one. Tombaatar is distinguished by its large size relative to other multituberculates, a well-developed postpalatine torus, the presence of palatine teeth, and an M1 cusp formula of 4, 5, 2 (labial to lingual).
About the Species
This specimen was collected from the Upper Cretaceous Djadokhta Formation of Ukhaa Tolgod, Negmegt Basin, in the Gobi Desert of Mongolia. It was made available to the University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Guillermo Rougier of the University of Louisville and Dr. Michael Novacek of the American Museum of Natural History.
About this Specimen
The specimen was scanned by Richard Ketcham on 22 December 1997 along the coronal axis for a total of 297 slices, each slice 0.25 mm thick, with an interslice spacing of 0.2 mm (for a slice overlap of 0.05 mm).
Kielan-Jaworoska, Z., and J. H. Hurum. 1997. Djadochtatheria. A new suborder of multituberculate mammals. Acta Palaeontologica Polonica 42:201-242.
Rougier, G. W., M. J. Novacek, and D. Dashzeveg. 1997. A new multituberculate from the late Cretaceous locality Ukhaa Tolgod, Mongolia: Considerations on multituberculate interrelationships. American Museum Novitates 3191:1-26.