Longisquama
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Longisquama Temporal range: Middle or Late Triassic, 235 Ma |
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| Cast of the type specimen | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Archosauromorpha |
| Genus: |
†Longisquama Sharov, 1970 |
| Species: | †L. insignis |
| Binomial name | |
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Longisquama insignis Sharov, 1970 |
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Longisquama is a genus of extinct reptile. There is only one species, Longisquama insignis, known from a poorly preserved skeleton and several incomplete fossil impressions from the Middle to Late Triassic Madygen Formation in Kyrgyzstan. It is known from a type fossil specimen; slab and counterslab (PIN 2548/4 and PIN 2584/5), and five referred specimens of possible integumentary appendages (PIN 2584/7 through 9). All specimens are in the collection of the Paleontological Institute of the Russian Academy of Sciences in Moscow.
Longisquama means "long scales"; the specific name insignis refers to its small size. The Longisquama holotype is notable for a number of long structures that appear to grow from its skin. The current opinion is that Longisquama is an ambiguous diapsid and has no bearing on the origin of birds.
Longisquama is characterized by distinctive integumentary structures along its back. The holotype (specimen PIN 2584/4) is the only known fossil preserving these appendages projecting from the back of an associated skeleton. It has 7 appendages radiating in a fan-like pattern, but their tips are not preserved. PIN 2584/9 preserves five complete appendages spaced close together. PIN 2584/6 preserves two long, curved appendage running side by side. Other specimens, such as PIN 2585/7 and FG 596/V/1 preserve only one appendage. These structures are long and narrow throughout most of their length, and angle backward near the tip to give the appearance of a hockey stick. The proximal straight section is divided into three longitudinal lobes: a smooth lobe on either side and a transversely ridged lobe running between them. The middle ridged lobe is made up of raised "rugae" and deep "interstices," which Sharov compared to rosary beads. The distal section is thought to be an extension of the middle and anterior lobes of the proximal section. While the anterior lobe widens in the distal section, the posterior lobe of the proximal section narrows until it ends at the base of the distal section. In addition, an "anterior flange" appears about two-thirds the way up the proximal section and continues to the tip of the distal section. Both lobes in the distal section are ridged and separated by a grooved axis. In some specimens, the rugae of either lobe in the distal section line up with each other, while in other specimens they do not. Some specimens have straight rugae projecting perpendicular to the axis, while others have rugae that curve in an S-shape. One specimen of Longisquama, PIN 2584/5, has small spines projecting from the axis of the distal section.
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