[dinosaur] Mengciusornis, new toothed ornithuromorph from Early Cretaceous of China

Ben Creisler
[email protected]

A new paper:


Mengciusornis dentatus gen. et sp. nov.

Min Wang, Jingmai K. O’Connor, Shuang Zhou & Zhonghe Zhou (2019)
New toothed Early Cretaceous ornithuromorph bird reveals intraclade
diversity in pattern of tooth loss.
Journal of Systematic Palaeontology  (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1080_14772019.2019.1682696&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=m6CywHY0JvQElJqaVe9BA12gxzmlgQZpJyDnzC5q5gA&s=miSOVsaowznoZ2w33kk4c-RmUxlYI_91x5nHe_jSEmQ&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.tandfonline.com_doi_abs_10.1080_14772019.2019.1682696&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=m6CywHY0JvQElJqaVe9BA12gxzmlgQZpJyDnzC5q5gA&s=UWqlqmiCsyn9Ft50LbSjjdKQ9A-31fingkUXyWByb5Y&e= 


The earliest record of the Ornithuromorpha, which includes crown birds, is
currently known from the Early Cretaceous Jehol Biota in north-eastern
China. Here we describe a new ornithuromorph bird, Mengciusornis dentatus
gen. et sp. nov., from the Jiufotang Formation of this biota. Mengciusornis
preserves a suite of morphological features exclusively observed among
ornithuromorphs in the sympatric taxon Schizooura, including a robust and
‘V’-shaped furcula with a short hypocleidium, and a humerus with a large,
rectangular deltopectoral crest in which the distodorsal corner is
distinctively developed into a sharp, angular point. The results of our
phylogenetic analysis recover these two species together in a clade,
positioned stemward within the Ornithuromorpha. Mengciusornis has toothed
premaxillae, in stark contrast with the edentulous jaws of Schizooura,
demonstrating that dentition varied considerably between some closely
related species. Furthermore, all previously known Jehol ornithuromorphs
with toothed premaxillae have an edentulous rostral portion of the element,
suggesting that tooth loss in this clade proceeded from the rostral end
caudally, whereas in Mengciusornis the premaxilla lacks this edentulous
rostral tip although the maxilla and dentary are toothless, indicating that
the pattern of tooth loss, not unexpectedly, varied between lineages of
ornithuromorphs. This observation suggests a strong degree of plasticity in
the developmental mechanisms regulating tooth and beak formation, which is
supported by earlier evidence that indicates teeth have been lost multiple
times within Aves and Dinosauria. Mengciusornis preserves a ventrally
hooked scapular acromion that is convergently evolved in parallel with some
enantiornithines and neornithines, providing further evidence of the
homoplasy that characterizes avian evolution.