Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull

Abstract

The fossil record is a unique source of evidence for important evolutionary phenomena such as transitions between major clades. Frustratingly, relevant fossils are still comparatively rare, most transitions have yet to be documented in detail and the mechanisms that underpin such events, typified by rapid large scale changes and for which microevolutionary processes seem insufficient, are still unclear. A new pterosaur (Mesozoic flying reptile) from the Middle Jurassic of China, Darwinopterus modularis gen. et sp. nov., provides the first insights into a prominent, but poorly understood transition between basal, predominantly long-tailed pterosaurs and the more derived, exclusively short-tailed pterodactyloids. Darwinopterus exhibits a remarkable 'modular' combination of characters: the skull and neck are typically pterodactyloid, exhibiting numerous derived character states, while the remainder of the skeleton is almost completely plesiomorphic and identical to that of basal pterosaurs. This pattern supports the idea that modules, tightly integrated complexes of characters with discrete, semi-independent and temporally persistent histories, were the principal focus of natural selection and played a leading role in evolutionary transitions.

Timing of the earliest known feathered dinosaurs and transitional pterosaurs older than the Jehol Biota

“…Some authors concluded that it belongs to the Early Cretaceous (He H., 2004a(He H., , 2004b(He H., , 2005Wang et al, 2005b;Zheng et al, 2009) and others describe it as Jurassic (Zhang J, 2002;Zhang H, 2008aZhang H, , 2008bLiu et al, 2004;Liu and Liu, 2005;Duan et al, 2009;Hu et al, 2009;Lü et al, 2009;Chen et al, 2004). The timing of their earliest emergence and evolution remains to be confirmed.…”

“…Though the feathered dinosaur species (Zheng et al, 2009;Hu et al, 2009;Xu and Zhang, 2005;Xu et al, 2009Xu et al, , 2011 and transitional pterosaurs (Lü et al, 2009(Lü et al, , 2011 were discovered more recently in China, their age and that of the Daohugou Biota has been contentious. Some authors concluded that it belongs to the Early Cretaceous (He H., 2004a(He H., , 2004b(He H., , 2005Wang et al, 2005b;Zheng et al, 2009) and others describe it as Jurassic (Zhang J, 2002;Zhang H, 2008aZhang H, , 2008bLiu et al, 2004;Liu and Liu, 2005;Duan et al, 2009;Hu et al, 2009;Lü et al, 2009;Chen et al, 2004).…”

“…However, the Daohugou Biota (Zhang, 2002), which is older than the Jehol Biota and estimated to be of Jurassic age, was discovered in recent years at Ningcheng, Inner Mongolia, and in northeastern China, and has yielded spectacular fossil mammals Meng et al, 2006;Luo et al, 2007aLuo et al, , 2007bLuo et al, , 2011, pterosaurs (Ji and Yuan, 2002;Lü et al, 2009Lü et al, , 2011, and insects (Ren et al, 2009), in addition to feathered dinosaurs Xu and Zhang, 2005;Xu et al, 2009;Zheng et al, 2009;Zhang et al, 2000), which have greatly expanded our knowledge of the diversity and palaeobiology of a time before the Jehol Biota and contributed to our understanding of the origin of the Jehol Biota.…”

Cretornis hlavaci Frič, 1881 from the Upper Cretaceous of Czech Republic (Pterosauria, Azhdarchoidea)

“…4A, C (Bennett, 2001a: fig.70B), and Nyctosauridae (Bennett, 1989: 673). This foramen is notably absent in Dsungaripteridae, the likely sister group for Azhdarchoidea (Unwin, 2003;Lü et al, 2010). Thus, presence of this pneumatic foramen could be a synapomorphy for either Azhdarchoidea, under character optimization preferred parallelisms, or more inclusive clade, if reversals are preferred.…”

Origin and development of homoiothermy: A case study of avian energetics

“…Indeed, the fossils recently found in China and Mongolia suggest that feathered and, in some cases, flying animals had been formed in several different groups of theropods [77][78][79]. Certainly, these flying reptiles were not homoiotherms and their flight was a mere gliding that utilizes terrain features [22,[80][81][82][83]. As the author sees it, plumage in different reptilian groups can be explained by attempts to regulate heat dissipation induced by overheating during activity, as well as to provide thermoregulation connected with the alternation of day and night, since these animals were relatively small.…”