Angustinaripterus longicephalus (He, Yan & Su 1983) ZDM T 8001 Early Jurassic ~190 mya ~21 cm skull length, was originally considered a sister to Scaphognathus, then Unwin (2006) considered it basal to Rhamphorhynchus and Dorygnathus. Here Angustinaripterus is a very derived dorygnathid, derived from a sister to Dorygnathus purdoni and it phylogenetically preceded a tiny pterosaur inaccurately attributed to Pterodactylus? micronyx? St/Ei 1.
Distinct from D. purdoni, the skull of Angustinaripterus began to take on more and more ctenochasmatid characters. The skull was lower and longer. The naris was smaller and slit-like, yet a majority was dorsal to the antorbital fenestra. The quadrate leaned about 45 degrees. The palatal elements were more gracile. The teeth were more slender than in the R156 specimen of Dorygnathus and they diminished in size rapidly posteriorly.
See the pterosaur family tree here.
Angustinaripterus looked like a transitional taxon filling the gap between Dorygnathus and Ctenochasma and indeed it was. But first this lineage had to experience a steep phylogenetic size reduction illustrated here. It is easy to see how Angustinaripterus could have evolved into Ctenochasma, but how could a monophyletic "Pterodactyloidea" also produce the sharp-snouted germanodactylids at the same time? This was my first clue that the former Pterodactyloidea might not be monophyletic. As I added more and more previously excluded taxa it soon became apparent that the pterodactyloid grade was arrived at four separate times by convergence and that tiny pterosaurs appeared at the bases of each one of those clades. Becoming small, therefore, was a survival tactic that enabled the smaller members of several lines to survive and evolve while their larger sisters died out.
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