A detailed anatomical study of Pelecanimimus polyodon —the basin dinosaur that impacted paleontology in the 1990s — has revealed new insights into the evolution of ornithomimosaurs, a group of theropod dinosaurs related to modern birds that inhabited Laurasia and Africa during the Cretaceous.
Pelecanimimus it was the first non-avian dinosaur discovered in the Las Hoyas site, a wetland from 125 million years ago. Found in 1993 by Armando Díaz Romeral, it represents the first record of an ornithomimosaur in Europe and the first articulated non-avian dinosaur identified in Spain. It is the only known specimen.
Pelecanimimus was the first non-avian dinosaur discovered at the Las Hoyas site, a wetland dating back 125 million years.
“In the last decades, the number of ornithomimosaur species discovered around the world has been enormously increased, generating a great amount of information that has stimulated the need for an update and expansion of the anatomical description of their postcranial skeleton, as well as a discussion in the context of the new findings ”, declare the authors.
The results were published in the Zoological Journal of Linnean Society by paleontologists from the Autonomous University of Madrid (UAM), the National Distance Education University (UNED), the Fukui Prefecture Dinosaur Museum (Japan) and the Royal Academy of Sciences; led by paleontologist Elena Cuesta, from the Paleontological Museum of Munich (Germany) and the Prefectural University of Fukui (Japan).
3D reconstruction of the Pelecanimimus arm from the photogrammetry performed on the fossil.
Bird-mimicking lizards and long hands
Specifically, this study of the postcranial skeleton (spine and extremities) of Pelecanimimus polyodon has provided new insights into the evolution of the hand and sternum of the ornithomimosaur lineage (“bird-mimicking lizards”).
The results reveal that this lineage has a tendency to lengthen the hands, presenting longer phalanges or metacarpals than their more primitive relatives. This specialization, which is also evident in Pelecanimimus, has made it possible to recognize a new group within Ornithomimosauria, for which the name of macrocheiriformes (“Long hand shapes”).
Pelecanimimus is also the only ornithomimosaurus that retains an ossified sternum, whose morphology is similar to other maniraptoriforms such as Velociraptor, ovirraptorosaurs, and primitive birds.
It is the only one of its group that presents projections associated with the ribs of the dorsal vertebrae called uncinate processes.
It is also the only one of its group that presents projections associated with the ribs of the dorsal vertebrae called uncinate processes. These processes are also present in birds, and are areas of muscular insertion whose function is to improve the mechanical movements of the ribs and sternum during respiration, facilitating inspiration and expiration. His presence in theropod dinosaurs non-avian, as is the case of Pelecanimimus, indicates that they already had a breathing mechanism similar to that of current birds.
“Although the evolutionary history of both the sternum and the uncinate processes is difficult to establish, since they are very delicate elements and are not easily preserved in fossil skeletons, Pelecanimimus shows that these elements were already present in ornithomimosaurs and that their morphology it is very similar to that of many other theropods ”, conclude the authors.
Cuesta, E., Vidal, D., Ortega, F., Shibata, M., Sanz, JL “Pelecanimimus (Theropoda: Ornithomimosauria) postcranial anatomy and the evolution of the specialized manus in Ornithomimosaurs and sternum in maniraptoriforms”. Zoological Journal of the Linnean Society.
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