''Rativates'' is a genus of

ornithomimid Ornithomimidae (meaning "bird-mimics") is a family of theropod dinosaurs which bore a superficial resemblance to modern ostriches. Ornithomimids were fast, omnivorous or herbivorous dinosaurs known mainly from the Late Cretaceous Period of Laura ...

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the

Dinosaur Park Formation The Dinosaur Park Formation is the uppermost member of the Belly River Group (also known as the Judith River Group), a major geologic unit in southern Alberta. It was deposited during the Campanian stage of the Late Cretaceous, between about 76. ...

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

is ''Rativates evadens''.

Discovery and naming

In 1934, Levi Sternberg discovered the skeleton of a small ornithomimid at Quarry N° 028 near the

Red Deer River The Red Deer River is a river in Alberta and a small portion of Saskatchewan, Canada. It is a major tributary of the South Saskatchewan River and is part of the larger Saskatchewan-Nelson system that empties into Hudson Bay. Red Deer River ...

in the area of the present

Dinosaur Provincial Park Dinosaur Provincial Park is a UNESCO World Heritage Site situated a two hour drive east of Calgary, Alberta, Canada; or , about a half-hour drive northeast of Brooks. The park is situated in the Red Deer River valley, which is noted for its strik ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

. In 1950, he considered it a specimen of ''

Struthiomimus ''Struthiomimus'' (meaning "ostrich mimic", from the Ancient Greek, Greek στρούθειος/''stroutheios'' meaning "of the ostrich" and μῖμος/''mimos'' meaning "mimic" or "imitator") is a genus of Ornithomimidae, ornithomimid dinosaurs ...

''. In 1972, Dale Alan Russell formally referred this specimen to ''Struthiomimus altus''; he partly based his reconstruction of ''S. altus'' on the skull of the specimen. The remainder of the skeleton was not described until 2016. In 2016, the type species ''Rativates evadens'' was named and described by Bradley McFeeters, Michael J. Ryan, Claudia Schröder-Adams and Thomas M. Cullen. The generic name is derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''ratis'', "raft", in reference to the bird group

ratites A ratite () is any of a diverse group of flightless, large, long-necked, and long-legged birds of the infraclass Palaeognathae. Kiwi, the exception, are much smaller and shorter-legged and are the only nocturnal extant ratites. The systematics o ...

, and ''vates'', "seer", as the ornithomimids seemingly foretold the future existence of the ratites they resembled. The specific name ''evadens'' 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. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, ROM 1790, was found in a layer of the lower

, dating to the late

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...

. 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 the

Royal Ontario Museum The Royal Ontario Museum (ROM) is a museum of art, world culture and natural history in Toronto, Ontario, Canada. It is one of the largest museums in North America and the largest in Canada. It attracts more than one million visitors every year ...

Description

The known specimen of ''Rativates'' was a subadult or adult individual of at least eight years in age, as demonstrated through

lines of arrested growth Growth arrest lines, also known as Harris lines, are lines of increased bone density that represent the position of the growth plate at the time of insult to the organism and formed on long bones due to growth arrest. They are only visible by radi ...

in a

thin section In optical mineralogy and petrography, a thin section (or petrographic thin section) is a thin slice of a rock or mineral sample, prepared in a laboratory, for use with a polarizing petrographic microscope, electron microscope and electron ...

of the right femur. It was small for an ornithomimid, being about 50% of the size of the largest individuals of ''

''. The authors identified four

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

, unique derived traits, that distinguish ''Rativates'' from all other ornithomimids: the part of the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

contacting the

jugal The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anatomy ...

is relatively short and posteroventrally located; the

tail vertebrae The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordate ...

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 the

ischia Ischia ( , , ) is a volcanic island in the Tyrrhenian Sea. It lies at the northern end of the Gulf of Naples, about from Naples. It is the largest of the Phlegrean Islands. Roughly trapezoidal in shape, it measures approximately east to west ...

are entirely fused together on their back surfaces, with no vertical cleft between them; and the flexor edge of the third

metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the med ...

is straight, not concave as in other ornithomimids. In addition, the authors also noted other traits that distinguished it from the contemporary ornithomimids it shared its

habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...

with. Unlike ''Struthiomimus'', the anterior portion of the ilium reaches as far forward as the end of the pubic shaft, and the medial (inner) edge of the third metatarsal is straighter as well. Compared to ''

Ornithomimus ''Ornithomimus'' (; "bird mimic") is a genus of ornithomimid dinosaurs from the Late Cretaceous Period of what is now North America. ''Ornithomimus'' was a swift bipedal theropod which fossil evidence indicates was covered in feathers, equippe ...

'', the

antorbital fenestra An antorbital fenestra (plural: fenestrae) is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with archosauriforms, first appearing during the Triassic Period. Among extant archosaurs, bird ...

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 its

ungual An ungual (from Latin ''unguis'', i.e. ''nail'') is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and ungulates have ungual phalanges, as did the sauropod Sauropoda (), whose members are known as sauropods (; ...

s (foot claws).

Classification

A phylogenetic analysis was conducted based on the dataset used in the description of the Bissekty ornithomimid. The analysis recovered ''Rativates'' in a

polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tr ...

of derived ornithomimids, consistent with a single

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...

of ornithomimids in

Laramidia Laramidia was an island continent that existed during the Late Cretaceous period (99.6–66 Ma), when the Western Interior Seaway split the continent of North America in two. In the Mesozoic era, Laramidia was an island land mass separated from A ...

during the

References

{{Portalbar, Dinosaurs, Cretaceous Fossils of Canada Dinosaur Park fauna Ornithomimids Late Cretaceous dinosaurs of North America Fossil taxa described in 2016 Paleontology in Alberta Campanian genus first appearances Campanian genus extinctions

Discovery and naming

Description

Classification

See also

References