The remains of new Ostrich-like dinosaurs with exceptionally long hands in Mexico have stunned paleontologists. This new ornithomimosaur, officially named Mexidracon longimanus, represents a brand new genus and species within Ornithomimidae, an extinct family of theropod dinosaurs.
It was discovered from the Upper Cretaceous Cerro del Pueblo Formation (CdP) of Coahuila, Mexico. The new group is differentiated by an individual preserving axial and appendicular elements.
Greater diversity of ornithomimosaurs
Published in Cretaceous Research, the details of Mexidracon Longimanus point to a greater diversity of ornithomimosaurs in southern Laramidia.
The lone specimen of Mexidracon comes from sediment laid down in an estuary where oysters and other marine molluscs were abundant. This could show that it foraged in coastal places, according to researchers.
Mexidracon is from the Campanian part of the Late Cretaceous, and thus about 73 million years old. It joins an impressive, growing list of dinosaurs from the Mexican state of Coahuila, virtually all of which are 21st-century discoveries, reported Discover Wildlife.
Extreme lengthening of the metacarpals
Paleontologists maintain that Mexidracon Longimanus is characterized by extreme lengthening of the metacarpals that are longer than the metatarsals, proximal end of metacarpal II with a narrow subtriangular outline, a pubic peduncle of the ilium with a flared, zig-zag articular margin that is wider anteriorly than posteriorly and an ischiadic peduncle that is similar in size to the pubic peduncle.
“The finding of M. longimanus adds to the increasing diversity and paleobiogeographic distribution of the group during the Campanian of southern Laramidia. The ornithomimosaur record of the Cerro del Pueblo (CdP) represents yet another instance of the coexistence of ornithomimids and deinocheirids spanning a wide range of body sizes within this clade of ‘ostrich’ dinosaurs,” said researchers in the study.
Palm alone longer than the upper arm
What makes Mexidracon surprising is the length of its metacarpals, the bones that form the palm. They show that its hands were extremely long and slender, the palm alone being longer than the upper arm. The long and slim forelimbs of ornithomimids have been compared to those of tree sloths, and one idea is that these dinosaurs reached into trees, shrubs, and bushes to pull branches and twigs toward the mouth.
It’s also being claimed that Mexidracon’s long hands could have been used to grab prey from water, perhaps fish.
A phylogenetic analysis places Mexidracon Longimanus within Ornithomimidae, forming a polytomic relationship with other members of this clade.
Ornithomimosaurs are a clade of ostrich-like theropod dinosaurs characterized by relatively small and delicate skulls with large orbits, long necks, elongated forelimbs with non-raptorial manus, and long cursorial hindlimbs.
Mexidracon Longimanus is the first ornithomimid formally described from Coahuila.
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