Sunday, April 3, 2016

[PaleoOrnithology • 2008] Pengornis houi • Insight into Diversity, Body Size and Morphological Evolution from the Largest Early Cretaceous Enantiornithine Bird

Pengornis houi
Zhou, Clarke & Zhang, 2008 DOI:  10.1111/j.1469-7580.2008.00880.x

Most of Mesozoic bird diversity comprises species that are part of one of two major lineages, namely Ornithurae, including living birds, and Enantiornithes, a major radiation traditionally referred to as ‘opposite birds’. Here we report the largest Early Cretaceous enantiornithine bird from north-east China, which provides evidence that basal members of Enantiornithes share more morphologies with ornithurine birds than previously recognized. Morphological evolution in these two groups has been thought to be largely parallel, with derived members of Enantiornithes convergent on the ‘advanced’ flight capabilities of ornithurine birds. The presence of an array of morphologies previously thought to be derived within ornithurine and enantiornithine birds in a basal enantiornithine species provides evidence of the complex character evolution in these two major lineages. The cranial morphology of the new specimen is among the best preserved for Mesozoic avians. The new species extends the size range known for Early Cretaceous Enantiornithes significantly and provides evidence of forelimb to hind limb proportions distinct from all other known members of the clade. As such, it sheds new light on avian body size evolution and diversity, and allows a re-evaluation of a previously proposed hypothesis of competitive exclusion among Early Cretaceous avian clades.

Keywords: bird evolution; China; Early Cretaceous; Enantiornithes

Aves Linnaeus, 1758 
Enantiornithes Walker, 1981 

Pengornis houi gen. et sp. nov

Holotype: IVPP (Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China). V15336 comprises a nearly complete skeleton preserved in partial articulation (Figs 1–3) lacking only sternum and pelvic bones and parts of the distalmost left forelimb.

Figure 1. Holotype of Pengornis houi gen. nov., sp. nov. (IVPP V15336). (A) Skeleton. (B) Line drawing.
Anatomical abbreviations: cav, caudal vertebra; cv, cervical vertebra; dr, dorsal rib; dv, dorsal vertebra; fu, furcula; ga, gastralia; hy, hypocleidium; lco, left coracoid; lfe, left femur; lfi, left fibula; lhu, left humerus; lil, left ilium; lpu, left pubis; lra, left radius; lsc, left scapula; lti, left tibiotarsus; ltm, left tarsometatarsus; lul, left ulna; ma, mandible; mcII, major metacarpal; mcIII, minor metacarpal; mtI, metatarsal I; phII-1, first phalanx of the major manual digit; py, pygostyle; rad, radiale; rco, right coracoid; rfe, right femur; rhu, right humerus; rpf, right pubic foot; rra, right radius; rsc, right scapula; rti, right tibiotarsus; rtm, right tarsometatarsus; rul, right ulna; sk, skull; sy, synsacrum; uln, ulnare; un, ungual.

Etymology: Peng’ refers to a Chinese mythological bird, ‘ornis’ is Greek for bird, and ‘houi’ is in honours of Lianhai Hou, a pioneering palaeo-ornithologist.

Locality and horizon: Dapingfang, Chaoyang, Liaoning China; Jiufotang Formation, Early Cretaceous (He et al. 2004).

Diagnosis: Four characters are unambiguously optimized as local autapomorphies of the new species in the phylogenetic analysis: premaxillae unfused throughout their length, hooked scapular acromion, a globose humeral head that projects further proximally than the deltopectoral crest (Characters 1:0, 105:1, 107:1, 108:1; Appendices 1 and 2).

Zhonghe Zhou, Julia Clarke and Fucheng Zhang. 2008. Insight into Diversity, Body Size and Morphological Evolution from the Largest Early Cretaceous Enantiornithine Bird. Journal of Anatomy. 212(5); 565–577. DOI:  10.1111/j.1469-7580.2008.00880.x

HU Han, ZHOU Zhong-He and Jingmai K. O’CONNOR. 2014. A subadult specimen of Pengornis and character evolution in Enantiornithes. VERTEBRATA PALASIATICA. 2014(1); 77-97