Ceratonykus
| Ceratonykus Temporal range: Late Cretaceous
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| Genus: | Ceratonykus Alifanov & Barsbold, 2009
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Ceratonykus (meaning 'horned claw') is a genus of alvarezsaurid theropod dinosaur that existed in the late Cretaceous period. The discovery of a fragmented skeleton in Mongolia in early 2009 has led scientists to question where alvarezsaurids fit taxonomically into Theropoda.
Description
Ceratonykus was a small, long-legged dinosaur that appears to have been be adapted for running in the desert. They belong to the family Alvarezsauridae, whose members ranged in size from 0.5–2 m (20–80 inches) in length, but may have been significantly larger - 2.5 m (8 ft).
Originally thought to be one of the earliest members of flightless birds, alvarezsaurids have recently been regarded as more basal theropods. Skeletal remains suggest that they had tiny but stout forelimbs and compact birdlike hands. The skeletal structure also suggests that this dinosaur possessed significant breast and arm muscles that were likely adapted for tearing and digging. They had elongate jaws with minute teeth and a tubular snout that suggests they could have been adapted to feed on insects such as termites.
Debate
Alifanov & Barsbold 2009 state that alvarezsaurids do not resemble theropods as they had large prefrontals, a long surangular process and a short angular process in the lower jaw. Theropods typically possessed just the opposite of this. Also, alvarezsaurids lacked gastralia and had a pelvic structure that is very unusual in nature.
Ceratonykus remains contain small, bony spur-like projections on the hands which Alifanov & Barsbold suggest are claws from fourth and fifth digits. The shape of the brain (based on observation of the skull) lends to the idea that the brain is an unusual shape, and not consistent with the shape of theropods.
Alvarezsaurids have had a slightly confusing taxonomic history. In 1993 the alvarezsaurids were thought to be flightless birds more closely related to modern birds than to Archaeopteryx (a basal bird that lived in the late Jurassic Period around 150–145 million years ago - shown below, right). Recent testing of larger data sets has strongly suggested that these animals are of a non-avian nature. Their exact position within Theropoda is now debated, as some scientists maintain that they are close relatives of ornithomimosaurs, while others say they are more closely related to Maniraptora.
