Byronosaurus is a genus of troodontid dinosaur from the Late Cretaceous Period of Mongolia.
Discovery and naming[]
In 1993, Michael Novacek, a member of an American Museum of Natural History expedition to the Gobi Desert, discovered the skeleton of a small theropod at Ukhaa Tolgod. This was further excavated in 1994 and 1995. The find was illustrated in a publication in 1994. On 15 July 1996, at the Bolor's Hill site, about eight kilometers (five miles) away from the original location, a second specimen was discovered, a skull.
In 2000, Mark Norell, Peter Makovicky and James Clark named and described the type species Byronosaurus jaffei. The species name as a whole honoured Byron Jaffe, "in recognition of his family's support for the Mongolian Academy of Sciences-American Museum of Natural History Paleontological Expeditions".
The holotype, IGM 100/983, was found in a layer of the Djadochta Formation dating from the late Campanian. It consists of a partial skeleton with skull. It contains a partial skull with lower jaws, three neck vertebrae, three back vertebrae, a piece of a sacral vertebra, four partial tail vertebrae, ribs, the lower end of a thighbone, the upper ends of a shinbone and calf bone, a second metatarsal and three toe phalanges. The paratype, specimen IGM 100/984, is the skull found in 1996, of which only the snout has been preserved. Both specimens are of adult individuals.
In 2003, the skeleton was described in detail.
In 2009, two front skulls and lower jaws of very young, perhaps newly hatched, individuals, specimens IGM 100/972 and IGM 100/974, were referred to Byronosaurus, after originally having been identified as Velociraptor exemplars.
Description[]
Byronosaurus is a troodontid, a group of small, bird-like, gracile maniraptorans. All known troodontids share unique features of the skull, such as closely spaced teeth in the lower jaw, and large numbers of teeth. Troodontids have sickle-claws and raptorial hands, and some of the highest non-avian encephalization quotients, meaning they were behaviourally advanced and had keen senses. Byronosaurus is one of few troodontids that have no serrations on its teeth, similar to its closest relative Xixiasaurus. Byronosaurus was 1.5 m (4.9 ft) long and 50 cm (20 in) tall. It weighed only about 4 kilograms (9 lbs). Unlike most other troodontids, its teeth seem to lack serrations. They are instead needle-like, probably best suited for catching small birds, lizards and mammals. Specifically, they resemble those of Archaeopteryx.
The holotype skull measures about twenty-three centimeters long (nine inches). The snout is pneumatised, with a sinus in each maxilla.