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The feather fossils obtained from this specimen also suggest the presence of Stage IIIa feathers, a new discovery that indicates more complex feather structures were present in pterosaurs. The study describing this specimen further clarifies the timeline of avian feather evolution and suggests that the feather-specific melanosome signaling ...
The scales and scutes of birds were thought to be homologous to those of reptiles, [4] but are now agreed to have evolved independently, being degenerate feathers. [5] [6] Carcharodontosaurid theropod dinosaur Concavenator, is known to have possessed these feather-derived tarsal scutes.
A dragonfly in its radical final moult, metamorphosing from an aquatic nymph to a winged adult.. In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at specific times of the year, or at specific points in ...
It is possible that feathers first developed in even earlier archosaurs, in light of the discovery of vaned feathers in pterosaurs. [4] [5] Fossil feathers from the dinosaur Sinosauropteryx contain traces of beta-proteins (formerly called beta-keratins), confirming that early feathers had a composition similar to that of feathers in modern ...
Synapsida [a] is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant reptiles and birds).
While reptile scales use a sophisticated naming system (see figures), there has been a certain confusion because of synonymous names. For instance, the ventral scales are often called ventrals but gastrosteges is common in the older literature. In more recent publications they are often abbreviated as VSR (for ventral scale rows) or simply V. [4]
The β-keratins in feathers, beaks and claws – and the claws, scales and shells of reptiles – are composed of protein strands hydrogen-bonded into β-pleated sheets, which are then further twisted and crosslinked by disulfide bridges into structures even tougher than the α-keratins of mammalian hair, horns and hooves.
Beta-keratin (β-keratin) is a member of a structural protein family found in the epidermis of reptiles and birds. [1] [2] Beta-keratins were named so because they are components of epidermal stratum corneum rich in stacked beta sheets, in contrast to alpha-keratins, intermediate-filament proteins also found in stratum corneum and rich in alpha helices. [3]