Pterosaurs - uncertain ancestry The very first pterosaurs from
the Triassic are true pterosaurs, fully capable of flight, and
as such no intermediate animal, between a pterosaur and a
possible ancestor, is currently known. This means that
palaeontologists are still a little unsure as to the ancestry of
pterosaurs. Currently most scientists think that pterosaurs
belong to a group of reptiles known as archosaurs, which also
includes crocodiles, dinosaurs and birds. Pterosaurs are
probably closely related to dinosaurs, but they are not members
of the group Dinosauria. The pterosaur skeleton displays
numerous modifications that enabled them to fly. Their skeletons
were very lightly constructed and most of their bones were
hollow and enclosed an air sac system connected to the lungs, as
in birds. The bones of the arms were elongated, especially those
of the hand and one of the fingers. The bone was composed of
many microscopically thin layers stacked together like a
spirally bound plywood tube. Sometimes the bones