Abdominal ribs ( lat. Gastralia ) - part of the skin skeleton , elongated bone formations that are found in the tendon layers of the abdominal muscles in some modern reptiles ( crocodiles , trotters , and in a rudimentary form in some lizards ). Also, these anatomical structures are known in many groups of prehistoric extinct amphibians and reptiles. Are skin formations, remnants of the abdominal shell of labyrinthodonts . The abdominal ribs have nothing in common with real (true) ribs and are not connected with the spine [1] .
Dinosaurs
Developed abdominal ribs are characteristic of predatory dinosaurs . They are known in tyrannosaurids , terizinosaurids , dromaeosaurids , oviraptorids , ornithomimides , etc. [2] . The total number of abdominal ribs in them reached at least 12-14 pairs. Each edge consisted of two segments — the lateral (lateral) and medial (median) segments, which were connected to each other by the overlapping of the oppositely directed ends. As a rule, the abdominal ribs become thinner as you move backwards. The most thickened front ribs were spliced in pairs. At the same time, the number of such pairs among different groups was not the same, more often there was one - two pairs. The medial paired connection of the remaining abdominal ribs was movable, the left-sided overlapped the right-sided. In addition, each pair had a connection with the previous pair by attaching a rough head (medial end) of the left-side rib with an extension of the head of the right-side. As a result of this structure, plexuses of the ribs were formed, connected not only in pairs, but also with neighboring pairs. Probably, the compounds were characterized by a certain mobility, which allowed bends of the abdominal surface [3] .
Notes
- ↑ Naumov N. P., Kartashev N. N. Zoology of vertebrates. - Part 2. - Reptiles, birds, mammals: A textbook for the biologist. specialist. un-com. - M .: Higher. school, 1979. - 272
- ↑ Claessens, Leon PAM (März 2004). Dinosaur gastralia: origin, morphology, and function. Journal of Vertebrate Paleontology, Band 24 (1): Seiten 89-106
- ↑ Barsbold R. Predatory dinosaurs of the chalk of Mongolia. M .: Science, 1983, - 120 p.