I might be a little safe with this reconstruction, but it represents a further attempt to clean up and add to the number of controversial archosauromorphs for which few skeletals exist, or whose existence is owed to controversial reconstructors or miseducators seeking personal fame over accuracy.
Longisquama insignis is a little odd for many reasons, and which have led to some debate over its affinities or the nature of the integumentary structures associated with the holotype skeleton and which are known from isolated blocks. Here, however, I will merely note that the reconstruction above differs in some substantive details from my previous attempt, shown below:
Even at the time I placed this image on this blog, I’d decided that evidence didn’t favor an erect, archosaur-style posture. My reasons at the time were based on some details of the shoulder and hand, but these are not entirely consistent only with erect postures or digitigrade limbs.
For one, the shoulder suggests a lateral orientation for the humerus, the forearm presents a bowed ulna consistent with flexed elbows, and while the metacarpals are long, the carpals are small and irregular, and I am reminds of the feet of frogs and other tetrapods in which the metapodial elements contribute to digit length. Meaning, the limbs would be possibly splayed and plantigrade. Be aware this is speculation, and details of the original specimen are sparse as the preservation is terrible aside from the impressions, with the granularity of the slab extremely rough, meaning some elements are less differentiated than grains in the matrix.
Another departure involves the presence or absence of an antorbital fenestra; I’ve here opted for the latter, rather than the former. This is merely an option: the material is broken and a large apse on the side of the skull can suggest either, but does not indicate, a conclusion Buchwitz and Voight (2012) arrived at and which I can now agree with. However, depending on the phylogenetic affinities of the taxon, such a fenestra might still be inferred, albeit poorly.
Perhaps one oddity that needs resolving is the strap-like, elongated scapula, a feature seen in other non-avian tetrapods but which predominately finds itself amongst the birds. Chameleons, amongst other lizards, and the peculiar Drepanosauridae also feature such scapulae, which are held vertically and may limit excursion of the humerus in certain directions due to orientation of muscles. This shouldn’t be an issue for Longisquama, as the scapula is in an avian-like position, but it leads us to ask why, as this feature is peculiar to a quadruped without extensive head-supporting muscles (many sauropod, hadrosaur and ceratopsid dinosaurs also have strap-like scapulae and large, outsized heads or very long necks, or both).
Sharov, A. G. 1970. A peculiar reptile from the lower Triassic of Fergana. Paleontologicheskii Zhurnal 1(1): 127-130. [in Russian]
Buchwitz, M. & Voigt, S. 2012. The dorsal appendages of the Triassic reptile Longisquama insignis: reconsideration of a controversial integument type. Paläontologische Zeitschrift 86(3): 313-331.