Tototlmimus

DiscoveryEdit

The only known species, the type Tototlmimus packardensis was named and described in 2015 by Claudia Ines Serrano Brañas, Esperanza Torres-Rodriguez Paola Carolina Reyes-moon, Ixchel Gonzalez-Gonzalez Ramirez and Carlos Leon. The genus name is derived from the Nahuatl word tototl, "bird" and the ancient Greek mimus, mimic. The species name refers to its origin from the "Packard Formation".

The fossil specimen, the holotype ERNO 8553, was found in the northeastern Mexican state of Sonora, in the Cabullona Group, in an bed of the Packard Shale which may date from the late Campanian, 72 million years ago. It consists of a partial skeleton without skull. This includes the joint of the first finger of the left hand, the first joint and the third right finger second, the lower ends of the second, third and fourth metatarsal, the first and second joint of the second toe, the second and third phalanges the third toe, the first, third and fourth phalanx of the fourth toe, the first and second phalanx of the left second toe, and a claw foot. These fossil elements, none of which are complete, were found dissarticulated in an area of a half cubic meter.

DescriptionEdit

Tototlmimus is a medium-sized ornithomimid. The descriptors could identify five distinguishing characteristics. The lower end of the second and fourth metatarsal are not joined but are contacted by the lower surface of the third metatarsal. This contact is made possible because the inside of the third metatarsal fits perfectly with the sides of the second and fourth metacarpal. The third metatarsal has just developed ginglymoid inferior articular surface. The ungual, the bone of the claw, have narrow and shallow asymmetric grooves on both sides. Claw foot has a longitudinal groove for deep flexor tendon, but has instead a deep groove in the lower inner area near the surface of the articulation.

Tototlmimus shows a foot with a typical constitution for ornithomimosaurs. The midfoot is an arctometatarsus, with a third metatarsal that becomes narrower at the top. The claws have an articulate triangular surface foot with a relatively straight bottom surface. Back bottom edge forms a "heel" with a transversely, becoming deeper.

PhylogenyEdit

Tototlmimus is included in the family Ornithomimidae, in a derived position. It is the first ornithomimid named from Mexico and one of the southernmost known in North America. According to a cladistic analysis in the scientific description, it was the sister genus of Ornithomimus.

Cladogram based in the analysis by Serrano-Brañas et al., 2015: