Elmisaurinae

Deuterostomia

Elmisaurinae ("foot lizard," as derived from Mongolian ölmyi) is a subfamily of bird-like maniraptoran theropod dinosaurs within the clade Oviraptorosauria or Oviraptoridae. While more advanced than earlier oviraptorosaurs like Caudipteryx, elmisaurines were fairly primitive compared with their close relatives the oviraptorines, though this by no means reduces the distinct variation and unique nature of the group. Whereas oviraptorines had highly shortened snouts, elmisaurine jaws were long and shallow with an elongated dentary and extended symphysis. Indeed, the jaw of an elmisaurine is its most distinctive feature, historically, whose surface and internal structure is distinct from that of other dinosaurs, including oviraptorines.^[1] Elmisaurines are best known for their cranial anatomy, but the earliest forms are known from their postcrania alone, and include such novel features as a fused ankle (as also seen in similar and possibly related Avimimus portentosus), an extremely short tail, possibly with a pygostyle as in Nomingia gobiensis,^[2] and with exceptionally slender and long legs, giving them a gracile, long-legged appearance that may have resembled some of the smaller ratite birds, such as the emu.

Classification

The clade Elmisaurinae, together with its sister group the Oviraptorinae, comprises the family Oviraptoridae. The group has a confusing history of classification. It was traditionally seen as being more primitive than the oviraptorines, and thus placed as a distinct family, called the Caenagnathidae. However, that name is anchored on the species Caenagnathus collinsi, now recognized as a more primitive species, while the rest of the supposed group were found in later analyses to be nested within the traditional oviraptorids.

While in the past twenty years, only about two to six species were commonly recognized as belonging to the Elmisaurinae, currently that number may be much greater, with new discoveries and theories about older species that may inflate this number to up to ten. Much of this historical difference centers on the first elmisaurine to be described, Chirostenotes pergracilis. Due to the poor preservation of most elmisaurine remains and resulting misidentifications, different bones and different specimens of Chirostenotes have historically been assigned to a number of different species. For example, the feet of one species, named Macrophalangia canadensis,^[3] were known from the same region from which Chirostenotes pergracilis was recovered, but the discovery of a new specimen with both hands and feet preserved^[4] provided the support to combine them, while the later discovery of a partial skull with hands and feet.^[5]

Species

Today, Elmisaurinae usually contains six species in three genera. However, a few paleontologists consider Elmisaurus elegans to be a junior synonym of Chirostenotes sternbergi, as they both occur in the same North American locality, far from the Asian species Elmisaurus rarus.^[5] The genus Caenagnathasia martinsoni was originally placed in this family, but it is probably more primitive, lying outside Oviraptoridae within the superfamily Caenagnathoidea.^[6] Additionally, Maryańska, Osmólska, and Wołsan considered the oviraptorosaur with a pygostyle, Nomingia gobiensis, a member of this family,^[7] and Longrich and colleagues (2010) found the giant Gigantoraptor as a member.^[8]

Elmisaurinae includes -

• Avimimus portentosus, an enigmatic species often considered a more primitive oviraptorosaur. Nemegt Formation, Mongolia.^[9]
• Avimimus sp., an unnamed second species from the Iren Debasu Formation, Mongolia.^[9]
• Avimimus? sp., a possible third species from the Dinosaur Park Formation and Scollard Formation, Alberta.^[9]
• Chirostenotes pergracilis, described initially from two hands and a partial lower arm. Many subsequently named species have been referred to this species, including a single foot named Macrophalangia canadensis,^[3] adding to the known fossil material.^[5]
• Chirostenotes elegans, a smaller, more gracile Canadian species originally described as a species of Ornithomimus.^[10] It is probably a senior synonym of Chirostenotes sternberg'^[11] Some consider it a species of Elmisaurus instead, as both are smaller and more slender than Chirostenotes pergracilis. It is also possible that this species represents a different gender of the larger C. pergracilis specimens.^[12]
• Chirostenotes sp., a possible new species, has been identified from part of a lower jaw found in Montana, but not named.^[6]
• Elmisaurus rarus, the only known Asian caenagnathid (excluding Caenagnathasia martinsoni), is known only from elements of the foot.^[13]
• The "Triebold caenagnathid", a possible new species or genus collected by Triebold Paleontology of South Dakota, known from two excellently preserved partial specimens acquired by the Carnegie Museums of Pittsburgh. An apparently giant species with a well preserved skull and evidence of an oviraptorid-like crest, it is currently awaiting a published description.
• Hagryphus giganteus, discovered most recently, is a fairly large and over-assuming yet seldom mentioned species from Upper Cretaceous beds in Utah, USA (and is roughly the same age as Chirostenotes pergacilis.^[14]

References

External links

• Overview of Caenagnathidae by Jaime Headden.
• Photo of the Triebold caenagnathid, on display at the Carnegie Museum.
• Skeletal reconstruction of the Triebold specimens.