Byronosaurus
Byronosaurus | |
---|---|
Diagram showing known remains | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | †Troodontidae |
Subfamily: | †Troodontinae |
Genus: | †Byronosaurus Norell, Makovicky & Clark, 2000 |
Species: | †B. jaffei
|
Binomial name | |
†Byronosaurus jaffei Norell, Makovicky & Clark, 2000
|
Byronosaurus is a
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.[1] 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,
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.[2]
In 2003, the type specimen of Byronosaurus was described in detail. Makovicky and his colleagues found that Byronosaurus had a pneumatised snout with a sinus in each maxilla.[3]
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. Bever and Norell estimated that the skull length of IGM 100/972 and IGM 100/974 were about 22.6 cm (8.9 in) and 25.4 cm (10.0 in), respectively.[4]
In 2017, the researchers who described a troodontid Almas ukhaa suggested that the specimens described by Bever and Norell (2009) don't belong to Byronosaurus based on different features found in the skull such as the number of maxillary teeth in both specimens being significantly fewer than this genus. They argued that these specimens are more closely related to A. ukhaa than to B. jaffei.[5]
Description
Byronosaurus was a small dinosaur, measuring about 1.5–2 m (4.9–6.6 ft) long and 50 cm (20 in) tall; it weighed only about 4–20 kg (8.8–44.1 lb).
Classification
The following cladogram shows the position of Byronosaurus within Troodontidae according to a 2017 analysis by the palaeontologist Caizhi Shen and colleagues:[9]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Palaeobiology
Troodontids had some of the highest
Diet
Due to their large brains, possible
In 2001, the palaeontologists Philip J. Currie and Dong Zhiming rejected the idea that troodontids could have been herbivorous. They stated that troodontid anatomy was consistent with a carnivorous lifestyle, and pointed out that the structure of their serrations was not much different from those of other theropods. They noted that troodontid features such as sharply pointed serrations that curved up towards the tip of the teeth, razor sharp enamel between the serrations, and blood grooves at the bases, were not seen in herbivorous dinosaurs, which had simpler, cone shaped serrations.[12] Lü and colleagues discussed the previous studies of troodontid diet, and suggested that the loss of serrations in the teeth of Byronosaurus and some other troodontids was related to a change in their diet. Since the teeth would appear to have lost their typical ability to slice meat, at least these troodontids may therefore have been either herbivorous or omnivorous.[8] In 2015, the palaeontologist Christophe Hendrickx and colleagues suggested that basal (or "primitive") troodontids with unserrated teeth were herbivorous, whereas more derived troodontids with serrated teeth were carnivorous or omnivorous.[13]
Reproduction
The presence of tiny Byronosaurus skulls in an oviraptorid nest was considered an enigma. Hypotheses explaining how they came to be there included that they were the prey of the adult oviraptorid, that they were there to prey on oviraptorid hatchlings, or that an adult Byronosaurus may have laid eggs in a
Not only is the claim regarding nest parasitism considered dubious, but other researchers have pointed out the differences in skull morphology, suggesting that these specimens do not belong to this genus.[5] The eggs of Byronosaurus and other troodontids are not paired unlike oviraptorids like Citipati, but are "nearly vertically embedded with their round poles" up and are exposed barely above the sediment.[18]
See also
References
- JSTOR 24942946.
- ^ S2CID 51833414.
- S2CID 51824767. Archived from the original(PDF) on 2007-03-16. Retrieved 2007-02-04.
- ^ ISSN 0003-0082.
- ^ S2CID 90883541.
- ISBN 978-0195372663.
- OCLC 985402380.
- ^ .
- S2CID 129939153.
- ISBN 978-0-520-24209-8.
- ISSN 0871-5424.
- .
- from the original on 2018-06-22. Retrieved 2018-12-04.
- ^ S2CID 22333224.
- ISBN 0-520-24209-2.
- ^ a b Brougham, J. (July 8, 2011). "Troodontid skulls in other nests: the answer". Dinosaur Mail. Archived from the original on November 17, 2011.
- ^ Grellet-Tinner, G. (2005). "Chapter VII – An Egg Clutch of the Troodontid Byronosaurus jaffei from the Gobi Desert: Novel Perspectives on the Origin of the Avian Reproductive Physiology". A Phylogenetic Analysis of Oological Characters: A Case Study of Saurischian Dinosaur Relationships and Avian Evolution. pp. 105–117.
- S2CID 162574571.