[D] Huaxiagnathus orientalis [Su] [sG] [T]
Hwang, Norell, Ji Q. and Gao, 2004
Saurischia Theropoda Tetanurae Coelurosauria Compsognathidae
Yixian Formation, Jehol Group, Dabangou village, Sihetun Area, near Beipiao City, Liaoning Province, China
Genus - Typespecies - Skull
The holotype specimen is nearly complete, lacking only the distal portion of the tail. It is the second largest theropod taxon discovered from Jehol Group sediments. Like all compsognathids Huaxiagnathus has short forelimbs and a relatively unspecialised coelurosaur body plan. Previously, fairly complete skeletons existed for only two small-bodied taxa of compsognathids, Compsognathus longipes from the Late Jurassic of Western Europe and Sinosauropteryx prima, also from the Yixian Formation. The phylogenetic position of Huaxiagnathus orientalis was analysed using an extensive matrix of theropod characters from many taxa.
From the same formation comes Sinocalliopteryx gigas that shares similar features with Huaxiagnathus orientalis in having a manus as long as the humerus plus radius, very large and subequally long manual unguals I and II, smaller proximal transverse width of the first metacarpal, and reduced olecranon process on the ulna.Sinocalliopteryx gigas is distinguisable from Huaxuagnathus in having the much larger size, a long maxillary antorbital fossa, the proportionally longer ulna (length ratio of humerus to ulna is 114%, compared with 160% in Huaxuagnathus)
Huaxiagnathus orientalis fell out at the base of the Compsognathidae, as it lacks the forelimb adaptations of more derived compsognathids. The addition of Huaxiagnathus and the two other compsognathid species to our data matrix resulted in the placement of Compsognathidae near the base of Maniraptora. Furthermore, Alvarezsauridae, [Paraves], and a monophyletic Therizinosauroidea + Oviraptorosauria clade fall out in an unresolved trichotomy in the strict consensus of our most parsimonious trees.
(CAGS-IG02-301) (~1.6 m; subadult) nearly complete skeleton missing caudal vertebrae past the 25th (radius 51 mm; metacarpal I 19 mm; phalanx I-1 38 mm; metacarpal II 40 mm; phalanx II-1 26 mm; phalanx II-2 35 mm; metacarpal III 26 mm; femur 163 mm; metatarsal III 102 mm) Referred- (NGMC 98-5-003; specimen of \\\\\\\"Huaxiasaurus\\\\\\\") (~1.8 m) partial skeleton including skull, forelimb, hindlimb.