Ear, Ear
One defining feature of mammals, distinguishing them from other animals, is the separation of the middle ear from the jaw, which improves hearing sensitivity.
Ji
et al.
(p.
278
; see the Perspective by
Martin and Ruf
) describe an adult Mesozoic fossil mammal, in a lineage that led to both marsupials and placentals, in which the middle ear is still ossified to the jaw. Recent developmental studies have shown that the release of the ear is tied to multiple genes and signaling pathways during development. Together, these data suggest how gene patterning may have led to the early evolution of the mammalian ear.
Toothless pterosaurs played a key role in broadening the taxonomic, morphological and ecological diversity of Cretaceous pterosaurs. Here we report a complete, articulated skeleton of a 1.4-m-wingspan pterosaur from the Lower Cretaceous Jiufotang Formation of Liaoning Province, China which is identified as a new genus and species, Shenzhoupterus chaoyangensis gen. et sp. nov. The new taxon is edentulous, with a relatively large skull and a remarkably large, tall nasoantorbital fenestra that extends well above the main part of the braincase. Phylogenetic analysis shows that Shenzhoupterus gen. nov. belongs in a distinct clade of azhdarchoid pterosaurs, formally recognised here as a new family, Chaoyangopteridae, that also includes Chaoyangopterus, Jidapterus and Eoazhdarcho from the Jiufotang Formation and Eopteranodon from the Yixian Formation. These new data clarify recent confusion surrounding the systematics of these Lower Cretaceous taxa and provide new insights into the evolutionary history of pterosaurs.
Oviraptorids are a group of specialized non-avian theropod dinosaurs that were generally one to 8 m in body length. New specimens of baby oviraptorids from the Late Cretaceous of Henan Province are some of the smallest individuals known. They include diagnostic characters such as the relative position of the antorbital fenestra and the external naris, distinct opening in the premaxilla anteroventral to the external naris, antorbital fossa partly bordered by premaxilla posterodorsally, lacrimal process of premaxilla does not contact the anterodorsal process of the lacrimal, parietal almost as long as frontal; in dorsal view, posterior margin forms a straight line between the postzygapophyses in each of the fourth and fifth cervicals; femur longer than ilium. They also elucidate the ontogenetic processes of oviraptorids, including fusion of cranial elements and changes in relative body proportions. Hind limb proportions are constant in oviraptorids, regardless of absolute body size or ontogenetic stage. This suggests a sedentary lifestyle that did not involve the pursuit of similar-sized prey. The functional implications for bite force and therefore dietary preferences are better understood through the study of such small animals. The comparison of the measurements of 115 skeletons indicates that oviraptorids maintain their hind limb proportions regardless of ontogenetic stage or absolute size, which is a pattern seen more commonly in herbivores than in carnivores. This may weakly support the hypothesis that oviraptorids are herbivores rather than active carnivores.
A new species of Darwinopterus, D. robustodens sp. nov. is described and named. Based on the new specimen, the diagnostic characters of Darwinopterus are amended and include: rostral dentition composed of well‐spaced, spike‐like teeth; the longest teeth are confined to the anterior half of the tooth row; tooth alveoli have raised margins; nasoantorbital fenestra confluent; inclined quadrate; elongate cervical vertebrae with low neural spine and reduced or absent ribs; long tail of more than 20 caudals partially enclosed by filiform extensions of the pre‐ and postzygapophyses; short metacarpus less than 60 per cent length of humerus, fifth toe with two elongate phalanges and curved second pedal phalanx of the fifth toe with the angle between the proximal and distal segments about 130 degrees. The complete specimen of the new pterosaur D. robustodens sp. nov. provides much more osteological information. The differences in tooth morphologies between Darwinopterus modularis and D. robustodens sp. nov. suggest that they filled different ecological niches. The hard integument‐bearing Coleoptera may have been the main food source of Darwinopterus robustodens.
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