A new small enantiornithine bird from the Jehol Biota, with implications for early evolution of avian skull morphology

Abstract

2015): A new small enantiornithine bird from the Jehol Biota, with implications for early evolution of avian skull morphology, Journal of Systematic Palaeontology, Enantiornithes is the most diverse Mesozoic avian clade. Approximately half of the known global diversity of Enantiornithes is from the Early Cretaceous Jehol Biota of China. The Jehol enantiornithines are usually articulated and complete, but the bones are overlain by each other and preserved in two dimensions, severely limiting the number of cranial characters that can be recognized. Here we describe a new enantiornithine bird, Pterygornis dapingfangensis gen. et sp. nov., from the Jehol Biota. The new taxon has a unique sternal morphology with an external rostral spine and a pair of craniolateral processes. Phylogenetic analysis resolves the new taxon in a derived position within Enantiornithes. The specimen is disarticulated with several exceptionally well-preserved cranial bones, including the jugal and quadratojugal, morphologies of which remain poorly understood for enantiornithines. Our results indicate that the quadratojugal is an inverted L-shaped element, morphologically similar to that of more basal birds Archaeopteryx bavarica, Jeholornis prima, Confuciusornis sanctus and Sapeornis chaoyangensis. Our findings also illustrate that the quadratojugal underwent large modifications with the reduction of the caudoventral and squamosal processes sequentially during early avian evolution, contributing to the refinement of the cranial kinesis in early birds.http://zoobank.org/urn:lsid:zoobank.org:pub:384D11F5-1CD3-4447-B01E-58D320B42D49

Insight into the growth pattern and bone fusion of basal birds from an Early Cretaceous enantiornithine bird

“…2 C and D). In contrast, these two bones are at best only proximally fused in other Early Cretaceous birds (7,16,18). As in other enantiornithines, the minor metacarpal is only fused with the major metacarpal proximally, and it extends further distally than the major metacarpal.…”

“…The phylogenetic analysis was performed using the modified dataset of Mesozoic birds in Wang et al (7). Description and complete results of the phylogenetic analysis are provided in the SI Text and SI Appendix.…”

“…The developmental mechanism underpinning such rare bone fusion in early birds remains largely unexplored. (Table S1), can be referred to as the enantiornithine Pterygornis dapingfangensis in having the following diagnostic characteristics of this taxon: The lateral margin of the coracoid is strongly convex, making the proximal end of the coracoid medially curved; the sternum has an external rostral spine and a pair of craniolateral processes; and the lateral trabeculae of the sternum are robust, bearing large fan-shaped caudal expansions that extend as far caudally as the xiphoid process (7). Descriptions of the skull, forelimb, and the pelvic girdle are presented in the main text, and other body regions are provided in SI Text.…”

A Comparative Morphological Study of the Jugal and Quadratojugal in Early Birds and Their Dinosaurian Relatives

“…). By contrast, the jugal is unforked caudally but simply curves dorsally in some species, including Pterygornis dapingfangensis , Cathayornis yandica , and B. guoi (Wang et al, ; Figs. and ).…”

“…So far, the quadratojugal of enantiornithines can only be identified in a single specimen, the holotype of P. dapingfangensis (IVPP V20729). The specimen is disarticulated with some cranial elements well preserved, including the jugal, quadratojugal, and splenial, allowing a rare chance to reconstruct morphologies for those elements (Wang et al, ). The quadratojugal is inverted L‐shape with jugal and squamosal processes (Fig.…”