Researchers have described a new theropod dinosaur from the Cerro del Pueblo Formation (Coahuila, northern Mexico).  The dinosaur has been named Mexidracon longimanus.  It is the first ornithomimid to be named from fossils associated with the Cerro del Pueblo Formation. The most conspicuous characteristics of this new taxon are the exceptionally long metacarpal bones.  These are the bones that form the palm of the hand.  The hands of Mexidracon longimanus were long and slender.  Furthermore, the hands were longer than the humerus (upper arm bone).  It is not known what these slender hands were used for, although it has been speculated that they helped this toothless dinosaur forage for food.

A scale drawing of the newly described ornithomimid dinosaur from the Cerro del Pueblo Formation (Mexico). Although known from only fragmentary remains it is thought this dinosaur was feathered. It is estimated to have stood around one metre tall and measured two and half metres long. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Mexidracon longimanus – the first ornithomimid formally described from Coahuila

In 2014, Professor Claudio de León-Dávila collected postcranial ornithomimid remains from a deposit representing an estuary environment.  These fossils are currently housed in the collection of the Benemérita Escuela Normal de Coahuila (BENC), a teacher training institution in Coahuila state. Ornithomimosaur remains are relatively common in the Campanian Cerro del Pueblo Formation, although most of the material is highly fragmentary.

To date only one other ornithomimosaur has been described from the region. Paraxenisaurus normalensis was scientifically described in 2020 (Serrano-Brañas et al).  It is represented by elements from the hands, limbs, including the distal end of a femur, and caudal vertebrae.  P. normalensis is thought to be much larger than the newly described Mexidracon.  Moreover, it has been tentatively assigned to the Deinocheiridae family within the Ornithomimosauria clade. Whereas, Mexidracon longimanus has been assigned to another family, the Ornithomimidae.

A model of Deinocheirus.  The figure is from the CollectA Age of Dinosaurs Popular range.

The image (above) shows the CollectA Age of Dinosaurs Popular Deinocheirus figure.  It is thought that Paraxenisaurus normalensis may have been related to this Asian deinocheirid.

To view the CollectA Age of Dinosaurs Popular range available from Everything Dinosaur: CollectA Prehistoric Animal Models.

The Etymology of a Dinosaur Name

The genus name is derived from the prefix “Mexi”, a reference to Mexico and the suffix “dracon”.  This is from the Greek, and it means serpent or dragon.  The species or trivial name translates as “long hands”.  So, this new theropod’s name translates as “long-handed Mexican dragon.”

The researchers conclude that the discovery of the first ornithomimid in this region of Mexico suggests that during the Campanian faunal stage of the Cretaceous there was a large number of different ornithomimosaurs present.

The scientific paper: “A long-handed new ornithomimid dinosaur from the Campanian (Upper Cretaceous) Cerro del Pueblo Formation, Coahuila, Mexico” by Claudia Inés Serrano-Brañas, Belinda Espinosa-Chávez, Claudio de León-Dávila, S. Augusta Maccracken, Daniela Barrera-Guevara, Esperanza Torres-Rodríguez and Albert Prieto-Márquez published in Cretaceous Research.

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