Tetrapoda
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The prepubes of Cosesaurus identified.
Here the coracoids are identified in blue, the scapulae in green, the interclavicle in red,
the clavicles in magenta and the sternum in yellow.
Cosesaurus pectoral area
Here all the elements in the pectoral area are identified.
Cosesaurus sister taxa
Basal fenestrasaurs:
Cosesaurus, Sharovipteryx, Longsisquama and basal pterosaurs. Click to enlarge.

The origin of the pterosaur wing began with the narrowing of the hand, the loss of the intermedium and the poor ossification of the carpus in Huehuecuetzpalli, a likely biped.

In Cosesaurus the two centralia were gone. A pteroid and preaxial carpal were present. Trailing fibers were wing membrane and aktinofibril precursors.

In Sharovipteryx and Longisquama the fingers were longer. Digit 4 was longer still in pterosaurs.

In Longisquama metatarsal 4 had rotated on its axis in order to fold the finger in the plane of the wing. The PILs were no longer continuous through digit 4 because it did not flex and extend in concert with the other three digits.

wing evolution


This GIF animation shows Sphenodon, Huehuecuetzpalli, Cosesaurus and Longisquama in sequence demonstrating the evolution of the pterosaur wing, including the migration of the centralia to the preaxial (medial) side of the wrist, the loss of the intermedium, the reduction of the space between the radius and ulna and other changes.

The origin and evolution of the prepubis in pterosaurs

The Origin and Evolution of the Prepubis
This sequence of sister taxa portrays the pelvis and prepubis of several tritosaurs, including Cosesaurus, Sharovipteryx, Longisquama and two basal pterosaurs. Note the gradual elongation of the ilium, the infilling of the thyroid fenestra (between the pubis and ischium), followed by the sudden appearance of the prepubis in Cosesaurus. Later fenestrasaurs and pterosaurs simply modified the various shapes of the elements.

Pterosaur pectoral girdle evolution

The evolution aof the pterosaur pectoral girdle as demonstrated in more primitive sister taxa, including Huehuecuetzpalli, Cosesaurus and Longisquama.

Cosesaurus is featured in The Pterosaur Heresies
Cosesaurus flapping
 
 
 
Tritosauria
Tijubina
Huehuecuetzpalli
 
Tanystropheidae
Macrocnemus
Dinocephalosaurus
Amotosaurus
Langobardisaurus
Tanytrachelos
Tanystropheus
 
Fenestrasauria
Cosesaurus
Kyrgyzsaurus
Sharovipteryx
Longisquama
MPUM6009
other pterosaurs
Squamata
 

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