The gastralial apparatus of Plateosaurus engelhardti: morphological description and soft-tissue reconstructio

Abstract

The fragmentary nature of the fossil record of the gastralial apparatus of sauropodomorph dinosaurs has considerable impact on our understanding its functional morphology and evolution in this group. With the aim of increasing our knowledge on the functional morphology of the gastralial apparatus of sauropodomorph dinosaurs, remains of the gastralial apparatus of Plateosaurus engelhardti are described. Soft-tissues and their function are reconstructed applying the Extant Phylogenetic Bracket, in this instance comprising crocodiles and birds. The gastralial apparatus of Plateosaurus consists of at least 18 gastralial rows. With exception of the 1st row, which has a chevron-shaped medial and two lateral gastralia, the gastralial rows consist of two medial and two lateral gastralia. The lateral gastralia are 2.2 –– 2.8 times longer than the associated medial gastralia. The proximal ends of the medial gastralia overlap in a latticelike arrangement, forming a mid-ventral imbricating articulation. Characteristic for Plateosaurus is the sigmoid form of the medial and lateral gastralia, the increasing angle of the gastralial rows from proximal to distal, as well as the increasing robustness of the gastralia rows from proximal to distal. According to the Extant Phylogenetic Bracket, the gastralial apparatus of Plateosaurus is embedded into M. rectus abdominis, which attaches to the caudal aspect of the sternum and indirectly to the distal end of the pubis. As in extant archosaurs, m. rectus abdominis is closely related to the other muscles of the hypaxial abdominal muscle group. The muscles of the hypaxial abdominal muscle group are active during ventilation and locomotion, which suggests that the functions of the gastralial apparatus of Plateosaurus may be more complex than previously suggested. Regina Fechner. Biomechanics Research Group, Fakultat fur Maschinenbau, Ruhr-Universitat Bochum, Universitatsstrase 150, 44801 Bochum, Germany. fechner@lmk.rub.de Rainer Gosling. Biomechanics Research Group, Fakultat fur Maschinenbau, Ruhr-Universitat Bochum, Universitatsstrase 150, 44801 Bochum, Germany. goessling@lmk.rub.de