| Anserimimus | |
|---|---|
 | |
| Mounted skeleton | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | †Ornithomimosauria |
| Family: | †Ornithomimidae |
| Genus: | †Anserimimus Barsbold,1988 |
| Species: | †A. planinychus |
| Binomial name | |
| †Anserimimus planinychus Barsbold, 1988 | |
Anserimimus (/ˌænsərɪˈmaɪməs/AN-sər-im-EYE-məs; "goose mimic") is agenus ofornithomimidtheropoddinosaur, from the LateCretaceousPeriod of what is nowMongolia. It was a lanky,fast-running animal, possibly anomnivore. From whatfossils are known, it probably closely resembled other ornithomimids, except for its more powerful forelimbs.
Anserimimus was found in the Mongolianaimag, or province, ofBayankhongor during a jointSoviet-Mongolian expedition to theGobi Desert, in the late 1970s. MongolianpaleontologistRinchen Barsbold namedAnserimimus in 1988, combining theLatinanser meaning 'goose' with theGreekmimos meaning 'mimic'.Anser is the generic name of several species ofgeese. AlthoughAnserimimus does not specifically resemble a goose, ornithomimosaurs have traditionally been named after different types of birds, such asStruthiomimus ('ostrich mimic'),Gallimimus ('rooster mimic'), andPelecanimimus ('pelican mimic'). The one named species ofAnserimimus is calledAnserimimus planinychus. Thespecific name is derived from the Latinplanus meaning 'flat', and the Ancient Greek ὄνυξ,onyx, meaning 'claw', in reference to the peculiar flattened claws which characterize the genus.[1]
There is only a single specimen ofAnserimimus, itsholotype IGM 100/300. It consists of a rather complete and articulated skeleton lacking the skull and lower jaws. Limited information has been published on the anatomy ofAnserimimus, as Barsbold did not describe most of these bones, instead focusing on only those with features that setAnserimimus apart from other ornithomimids. In an unpublished thesisRobert Bronowicz in 2005 gave a detailed description of the species, also referring to additional material to it, among which a second partial skeleton, specimen ZPAL MgD-I/65.[2] However, in 2010 Bronowicz concluded this other find, though most closely related toAnserimimus planinychus, probably represented a separatetaxon.[3]
Anserimimus was a medium-sized ornithomimosaurian.Gregory S. Paul in 2010 estimated its length at 3 metres (9.8 ft), and its weight at 50 kilograms (110 lb).[4] Other studies suggested that the holotype was heavier, weighing up to 143.6–170 kilograms (317–375 lb).[5][6] The thighbone is 435 millimetres long.
There are several key differences between it and related species, though most of these are shared with ZPAL MgD-I/65. The claws on the hand are long, low at the back, and rather straight, only slightly curved, with the lower surface nearly flat. The forelimb is long and also built more powerfully than that of other ornithomimids, with large crests on thescapulocoracoid of the shoulder andhumerus (upper arm bone), which provided attachment points for large arm muscles like thebiceps. Themetacarpus of the hand is fused, adding to the strength. The foot is strongly arctometatarsalian, with the thirdmetatarsal excluded from the front surface of themetatarsus over 40% of its upper length.
Anserimimus was by Barsbold assigned to theOrnithomimidae, a group ofderivedOrnithomimosauria. This has been confirmed by moderncladistic analysis. Its closest relative may beGallimimus from the same formation albeit from a different area (Kobayashi & Lu, 2003;[7] Kobayashi & Barsbold, 2005[8]). Other studies have been unable specifically to determine its relationships or those of any other ornithomimids (Jiet al., 2003;[9] Makovickyet al., 2004[10]).
The following cladogram is based on Xuet al., 2011:[11]
| Ornithomimidae |
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The function of the powerful arm, with its straightened claws, remains unknown. It may indicate a different diet of food-gathering strategy than other ornithomimids, although its diet is difficult to determine, since the animal's skull is unknown. Scientists have longhypothesized that ornithomimids, descended fromcarnivorous theropod ancestors, were actually omnivores or evenherbivores.[12]
Anserimimus was recovered from theNemegt Formation ofMongolia. The Nemegt is thought to representalluvial plains containingmeanderingrivers. The layerAnserimimus was found, is dated from the earlyMaastrichtian stage of theLate Cretaceous, or about 70million years ago.
Aside fromGallimimus, other theropods found in the Nemegt Formation include the giganticTarbosaurus andDeinocheirus, as well as smallerdromaeosaurids,oviraptorosaurs,troodontids, andbirds.Herbivores are represented by thehadrosauridsBarsboldia andSaurolophus, theankylosauridTarchia and severaltitanosauriansauropods andpachycephalosaurians. The rockfacies of this formation suggest the presence of stream and river channels, mudflats, and shallow lakes. Sediments also indicate that there existed a rich habitat, offering diverse food in abundant amounts that could sustain massive Cretaceous dinosaurs.[13]
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