Taxonomy
Like the 'long scales', the skeletal features of Longisquama are equally difficult to diagnose. As a result, Longisquama has been related by scientists to many different Sauropsid groups.
Sharov determined that it was a "pseudosuchian" (a "primitive" archosaur, but as an archosaur a relatively derived reptile) on the basis of two features - a mandibular fenestra and an antorbital fenestra. Sharov's original description also includes an elongate scapula. Jones et al. see Longisquama as an archosaur, adding to Sharov's two characters a furcula. Olshevsky believes that Longisquama is an archosaur and, moreover, an early dinosaur - a possibility which could actually dispense with almost all of the debate about bird origins, were it true.
Unwin & Benton didn't think it was possible to diagnose the crucial fenestrae; the holes could simply be damage to the fossil. They agreed with Sharov that Longisquama has acrodont teeth and an interclavicle, but instead of a furcula they saw paired clavicles. These features would be more typical of a member of Lepidosauromorpha, meaning that Longisquama is not an archosaur and thus not closely related to birds. According to a cladistic study by Phil Senter in 2004, Longisquama would be an even more basal diapsid and a member of Avicephala, more closely related to Coelurosauravus.
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