A strange, exciting new dinosaur belonging to the ‘ostrich mimic’ or ornithomimid family has been named from Mexico. It hints at an unexpected diversity of Mexican ostrich mimics and adds to our knowledge of diversity and biology within this group.
Published by Claudia Inés Serrano-Branas and colleagues in Cretaceous Research, the new dinosaur has been dubbed Mexidracon longimanus, meaning ‘long-handed Mexican dragon’.
It’s known from fore and hind limb bones, vertebrae, and parts of the pelvis. It was small, probably less than 3 m (10 ft) long, and its partly articulated remains were discovered by Claudio de León-Dávila in 2014.
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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.
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. They include armoured, horned and duckbilled dinosaurs, and tyrannosaurs and other predators. Dinosaur groups associated with the USA and Canada were evidently diverse in Mexico, but the Mexican species belong to lineages unknown from further north. This suggests the presence of a distinct faunal assemblage.
As suggested by their common name, ornithomimids superficially recalled ostriches when alive, though a long tail and other differences made them decidedly distinct. They were toothless, with robust, beaked jaws that suggest omnivory and an ability to clip and swallow leaves, buds, flowers and fruit. They are theropods, belonging to the great dinosaur group that includes megalosaurs and tyrannosaurs as well as birds and all bird-like forms.
Finds from Canada show that ornithomimids possessed a feathery coat, as was typical for theropods of this sort. Parallel stripes preserved on the arm bones of one specimen suggest the presence of long feathers on the arm and perhaps hand as well.
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 fore limbs 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 towards the mouth. Maybe Mexidracon was especially specialised for this lifestyle. An alternative, more speculative possibility is that its long hands were used to grab prey from water, perhaps fish.
The remains of Mexidracon published so far are fragmentary, and we hope that additional, more complete fossils are reported in time. We can also be confident that other dinosaurs will continue to be revealed from the Mexican Cretaceous, ultimately revealing a record rivalling that of other North American nations.
Main image: A speculative reconstruction imaginatively showing a coast-dwelling Mexidracon using its long, clawed hands as multi-pronged fish spears / Hodari Nundu
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