Longisquama is a genus of extinct reptile containing only one species, L. insignis, known from a poorly preserved skeleton and several incomplete fossil impressions from the Middle to Late Triassic Madygen Formation of Kyrgyzstan. The generic name means "long scales", and the specific name insignis means "unusual", in Latin. The holotype skeleton is notable for a number of long, superficially feather-like structures growing from its back, now thought to represent a single row growing upwards from the midline. The affinities of Longisquama among reptiles have long been contentious, with some researchers controversially connecting Longisquama and its back structures to the origin of birds and feathers, a view which is largely rejected. In 2025, a close relative, Mirasaura was described from France, which shares the feather-like back structures. Phylogenetic analysis of Mirasaura suggests that it and by extension Longisquama belong to Drepanosauromorpha. It is now suggested that the back structures served for display.
History The holotype specimen, PIN 2584/4, was discovered by A.G. Sharov while he was searching for Triassic insect fossils in the Leylek District in Kyrgyzstan. The specimen was recovered from rocks of the Madygen Formation, at the Djailaucho locality. Four other specimens, each preserving 1-6 "long scales" in isolation, were designated as paratypes. These specimens are all in the collection of the Paleontological Institute of the Russian Academy of Sciences in Moscow. Three additional isolated integumentary structures, in the collections of the Geological Institute of the Freiberg University of Mining and Technology, were recovered from the locality in 2007.
Interpretation Researchers Haubold and Buffetaut believed that the structures were long, modified scales attached in pairs to the lateral walls of the body, like paired gliding membranes. They published a reconstruction of Longisquama with plumes in a pattern akin to gliding lizards like Draco species and Kuehneosaurus latus, allowing it to glide, or at least parachute. Though the reconstruction is now thought to have been inaccurate, it has nevertheless persisted in paleoart of Longisquama. Other researchers place the scales differently. Unwin and Benton interpreted them as a single, unpaired row of modified scales that run along the dorsal midline. Jones et al. interpreted them as two paired rows of structures that are anatomically very much like feathers, and which are in positions like those of birds' spinal feather tracts. Feather-development expert Richard Prum (and also Reisz and Sues) see the structures as anatomically very different from feathers, and thinks they are elongate, ribbonlike scales. Still other observers (e.g. Fraser in 2006) believe that the structures are not part of Longisquama at all, that they are simply plant fronds that were preserved along with the reptile and were misinterpreted. Buchwitz & Voigt (2012) argue that the structures of Longisquama are not plant remains, because all of the structures except for the last in the holotype PIN 2584/4 are arranged regularly, and that they are not preserved as carbon films, the usual mode of preservation for plants in the Madygen Formation. The plant from Madygen with greatest similarity to the Longisquama structures is Mesenteriophyllum kotschnevii, but its leaves do not have the distinct hockey stick shape of the structures attributed to Longisquama. The discovery of Mirasaura, a closely related diapsid genus with similar structures preserved in articulation, demonstrates that these structures were indeed integumentary.
Description
Longisquama was a small reptile, estimated to have a body about 50 millimetres (2.0 in) long. The skull of Longisquama has the superficially bird-like appearance typical of drepanosaurs, with a tapering snout and domed skull roof. Teeth are present closer to the snout tip than in its close relative Mirasaura. The neck is composed of no more than seven cervical vertebrae, which lack cervical ribs. Longisquama lacks the distinctly humped back seen in Mirasaura and some other drepanosaurs, and it also lacks an olecranon process on the ulna. Longisquama possesses a U-shaped bone that has been interpreted as a furcula, but it differs in shape from the fused clavicles seen in other drepanosaurs, making its identification uncertain.
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