| Rativates | |
|---|---|
 | |
| Skull diagram of ROM 1790 | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | †Ornithomimosauria |
| Family: | †Ornithomimidae |
| Genus: | †Rativates McFeeterset al., 2016 |
| Type species | |
| †Rativates evadens McFeeterset al., 2016 | |
Rativates is a genus ofornithomimidtheropoddinosaur from theCampanian-aged (Late Cretaceous)Dinosaur Park Formation ofAlberta,Canada. Thetype species isRativates evadens.[1]
In 1934,Levi Sternberg discovered the skeleton of a small ornithomimid at Quarry N° 028 near theRed Deer River in the area of the presentDinosaur Provincial Park inCanada. In 1950, he considered it a specimen ofStruthiomimus.[2] In 1972,Dale Alan Russell formally referred this specimen toStruthiomimus altus; he partly based his reconstruction ofS. altus on the skull of the specimen.[3] The remainder of the skeleton was not described until 2016.[1]
In 2016, the type speciesRativates evadens was named and described by Bradley McFeeters, Michael J. Ryan, Claudia Schröder-Adams and Thomas M. Cullen. The generic name is derived from theLatinratis, "raft", in reference to the bird groupratites, andvates, "seer", as the ornithomimids seemingly foretold the future existence of the ratites they resembled. Thespecific nameevadens means "evading" in Latin, referring to the ability of the swift-running animal to evade predators and to its eighty year evasion of being recognised as a separate species.[1]
Theholotype,ROM 1790, was found in a layer of the lowerDinosaur Park Formation, dating to the lateCampanian. It consists of a partial skeleton, including the snout, the front lower jaws, the last back vertebra, six sacral vertebrae, sixteen front tail vertebrae that may or may not have formed a natural series, the complete pelvis, and the hindlimbs (minus the right toes). Many of the bones are damaged and compressed. It is part of the collection of theRoyal Ontario Museum.[1]
The known specimen ofRativates was a subadult or adult individual of at least eight years in age, as demonstrated throughlines of arrested growth in athin section of the right femur.[1] It was small for an ornithomimid, being about 50% of the size of the largest individuals ofStruthiomimus.
The authors identified fourautapomorphies, unique derived traits, that distinguishRativates from all other ornithomimids: the part of themaxilla contacting thejugal is relatively short andposteroventrally located; thetail vertebrae in front of the transition point (where the tail vertebrae become abruptly thinner and more elongated) have unusually horizontally short, mound-like neural spines; the left and right shafts of theischia are entirely fused together on their back surfaces, with no vertical cleft between them; and the flexor edge of the thirdmetatarsal is straight, not concave as in other ornithomimids.[1]
In addition, the authors also noted other traits that distinguished it from the contemporary ornithomimids it shared itshabitat with. UnlikeStruthiomimus, the anterior portion of theilium reaches as far forward as the end of thepubic shaft, and the medial (inner) edge of the third metatarsal is straighter as well. Compared toOrnithomimus, theantorbital fenestra is proportionally shorter. Finally,Rativates is smaller than the large Dinosaur Park ornithomimid (still unnamed as of 2016), and also differs in the anatomy of itsunguals (foot claws).[1]
A phylogenetic analysis was conducted based on the dataset used in the description of the Bissekty Formation ornithomimid (subsequently namedDzharacursor).[4][5] The analysis recoveredRativates in apolytomy of derived ornithomimids, consistent with a singleradiation of ornithomimids inLaramidia during theCampanian.[1]
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