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Yuanjiawaornis, new large enantiornithine bird from Lower Cretaceous of Liaoning, China

Ben Creisler

A new paper:

Dongyu Hu, Ying Liu, Jinhua Li, Xing Xu &  Lianhai Hou (2015)
Yuanjiawaornis viriosus, gen. et sp. nov., a large enantiornithine
bird from the Lower Cretaceous of western Liaoning, China.
Cretaceous Research 55: 210-219

A new large-bodied enantiornithine taxon is erected from the Early
Cretaceous Jiufotang Formation of western Liaoning, China.
This bird provides new morphological information about Enantiornithes.
A comparative analysis of sacral centra of basal birds suggests that
enantiornithines might have a uniquely shaped synsacrum.

Here we describe a new enantiornithine bird, Yuanjiawaornis viriosus
gen. et sp. nov., based on a nearly complete, mostly articulated
postcranial skeleton from the Lower Cretaceous Jiufotang Formation
(120 Ma) of western Liaoning Province, northeastern China. It is
similar in size to large bohaiornithids among the known Early
Cretaceous enantiornithines; only Pengornis houi is larger. The
semilunate carpal is incompletely fused to the metacarpals, suggesting
that the holotype specimen was not fully mature at the time of death.
The new specimen is distinguishable from other known enantiornithines
by a unique combination of features including large body size,
forelimb and hind limb subequal in length, a longitudinally grooved
ventral surface of the synsacrum, robust and long transverse processes
of the caudal-most sacral vertebra, a craniodorsally tapered acromion
process of the scapula, a straight lateral margin of the coracoid,
medially curved clavicular rami with tapered omal tips, a sternum that
is oval in outline with slightly expanded distally caudolateral
processes, a humeral head with a flat proximal surface, and a humerus
with a deltopectoral crest that gradually decreases in height
distally. A comparative analysis of some sacral features of basal
birds including this taxon suggests that enantiornithines might have a
uniquely shaped synsacrum, although more data is needed to confirm
that hypothesis.