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by Vladimir ALIFANOV, Cand. Sc. (Biol.), Yevgeny KUROCHKIN, Dr. Sc. (Biol.), RAS Institute of Paleontology
Paleoentomologist A. Sharov discovered on the territory of Fergana Valley (Kyrgyzstan) in the early 1970s, in the late Triassic deposits of Madygen encampment, a front part of the skeleton with the skull of a miniature reptile. On the surface of the slab of solid clay, containing the remains, there are still visible imprints of the outer skin: in the neck area and along the back edge of the shoulder and antebrachium the prolate and overlapping scales were clearly noticeable. The most interesting were back scales of the reptile - feather-like formations, long (up to 10-12 cm) and wide at the end.
Sharov named this fossil Longisquama insignis. In his opinion, Longisquama lived on trees and could "fly", using dorsal appendages, located supposedly in a row, as a kind of parachutes. He believed that this Triassic reptile belongs to a variety ofarchosaurs (a subclass of reptiles, including tecodonts, dinosaurs, crocodiles and flying lizards), related to birds.
Lately Longisquama was mentioned very seldom. In this sense only one article published in 1987 by West European paleontologists has been of interest. It deals with an aerodynamic form of dorsal appendages and their two-row location. On this basis it was assumed that Longisquama propelled itself from tree to tree, as is usually done, for example, by a squirrel-flier or lizard- small dragon today.
Nowadays Longisquama is again much talked about in view of activization of discussions on the problem of origin of birds. In the course of these discussions the number of champions of the hypothesis on the origin of birds from dinosaurs has considerably increased, which was especially influenced by a series of discoveries in China of Early Cretaceous predatory dinosaurs with remnants of natural feathers or imprints of skin formations, very like a feather cover. And it is here that the problem of Longisquama has sprung up.
In 1999 at the Kansas University (USA), the authors of this article in cooperation with a group of American paleontologists and zoologists (J. Ruben, L. Martin, A. Feduccia, etc.), using state-of-the-art optics, as well as potentialities of digital photographing, tried to study the morphological structure of Longisquama in detail.
As a result of this cooperation there appeared an article "Non-bird Feathers of Late Triassic Archosaur", in which an attempt is made to prove that dorsal appendages of Longisquama have a fan and a hollow axial stem, whose base is narrowed and rounded. All these features underline the likeness of the dorsal appendages and a feather, which, unlike scales, is formed from the subsurface part of the skin - a follicular nipple. Thus, it can be assumed that feather-like
structures appeared 75-80 min years before the appearance of archeopterix - an ancient bird that lived 150 mln years ago, in the late Jurassic period.
The article aroused broad public interest and produced a series of commentaries in leading periodicals. Opinions of specialists greatly differed. Some were ready to agree with the aforesaid, while others were categorically against it. Still others were surprised at the fact that the article neither contained discussions of the skeleton's structure nor analyzed related ties of Longisquama, which remain unclear for a majority of specialists. Unfortunately, the foreign press did not mention the attitude nuances of Russian authors of the article, which consist in the support of arguments in favor of feather-like structure of the dorsal appendages. There were no reasons to doubt Sharov's inference on the systematic affiliation and likeness of Longisquama at the moment of the article's publication in the Science magazine.
Recently an intricate additional processing of cervical vertebrae and shoulder belt of Longisquama was carried out at the Paleontological Institute, RAS. Besides, some details of the skull structure of the ancient animal were closely studied with the help of the binocular microscope of high resolving power-we tried to reveal commissures between some bones of the crushed skull concealed by multitude of fissures. As a result it appeared that the first description of the structure of Longisquama's skull can be considerably amended (new data are to be presented later in detail). Meanwhile we can assume that the Triassic Longisquama is a representative of dinosaurs.
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