Sinusonasus

Sinusonasus; Temporal range: Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Life restoration
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Clade:	Paraves
Family:	†Troodontidae
Subfamily:	†Sinovenatorinae
Genus:	†Sinusonasus; Xu & Wang, 2004
Type species
	†Sinusonasus magnodens; Xu & Wang, 2004
Synonyms
	Sinucerasaurus Xu & Norell, 2006;

Sinusonasus is a

troodontid

dinosaur.

The

junior objective synonym

.

The holotype, IVPP V 11527, was found in the Lujiatun Member of the Yixian Formation, dating from the Hauterivian. It consists of a partial skeleton including skull and lower jaw fragments and partial tail, pelvis and hindlimbs. The fossil is compressed and partially articulated.^[1]

Sinusonasus is a small troodontid. In 2010, Gregory S. Paul estimated its length at one metre, its weight at 2.5 kilogrammes.^[3] The femur is 141 millimetres long.^[1]

In 2004, several distinguishing traits were established. An interantorbital channel, connecting the

caudal vertebrae are so long, measured from the front to the back, that they connect, forming a continuous plate at the underside of the tail. The neck of the thighbone is elongated.^[1]

More generally, the head is relatively short, equalling 77% of the length of the thighbone. There are at least nineteen maxillary teeth per side. The front teeth are not serrated: those more to the rear only have denticles at the trailing edge. Five

metatarsal. The second metatarsal is distinctly shorter than the fourth. The second toe bears a retractable 'sickle claw'.^[1]

Sinusonasus was in 2004 placed in the Troodontidae. It was presumed to have had a rather derived position, despite living in the Early Cretaceous. This was by the describing authors not interpreted as an indication for a long ghost lineage, troodontids developing earlier during the Jurassic than had been thought, but explained by rapid evolutionary change after a Cretaceous origin of the group.^[1]

References

^ ^a ^b ^c ^d ^e ^f Xu X. and Wang X.-l. 2004. "A New Troodontid (Theropoda: Troodontidae) from the Lower Cretaceous Yixian Formation of Western Liaoning, China". Acta Geologica Sinica 78(1): 22-26
^ Xu X., and Norell, M., 2006, "Non-avian dinosaur fossils from the Lower Cretaceous Jehol Group of western Liaoning, China", Geological Journal, 41(3-4): 419-437
^ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 141

[Xu2004-1] ^ ^a ^b ^c ^d ^e ^f Xu X. and Wang X.-l. 2004. "A New Troodontid (Theropoda: Troodontidae) from the Lower Cretaceous Yixian Formation of Western Liaoning, China". Acta Geologica Sinica 78(1): 22-26

[2] Xu X., and Norell, M., 2006, "Non-avian dinosaur fossils from the Lower Cretaceous Jehol Group of western Liaoning, China", Geological Journal, 41(3-4): 419-437

[3] Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 141

[1]

[3]

See also

References