A Three-Dimensional Skeletal Reconstruction of the Stem Amniote Orobates pabsti (Diadectidae): Analyses of Body Mass, Centre of Mass Position, and Joint Mobility.
Orobates pabsti, a basal diadectid from the lower Permian, is a key fossil for the understanding of early amniote evolution. Quantitative analysis of anatomical information suffers from fragmentation of fossil bones, plastic deformation due to diagenetic processes and fragile preservation within surrounding rock matrix, preventing further biomechanical investigation. Here we describe the steps taken to digitally reconstruct MNG 10181, the holotype specimen of Orobates pabsti, and subsequently use the digital reconstruction to assess body mass, position of the centre of mass in individual segments as well as the whole animal, and study joint mobility in the shoulder and hip joints. The shape of most fossil bone fragments could be recovered from micro-focus computed tomography scans. This also revealed structures that were hitherto hidden within the rock matrix. However, parts of the axial skeleton had to be modelled using relevant isolated bones from the same locality as templates. Based on the digital fossil, mass of MNG 10181 was estimated using a model of body shape that was varied within a plausible range to account for uncertainties of the dimension. In the mean estimate model the specimen had an estimated mass of circa 4 kg. Varying of the mass distribution amongst body segments further revealed that Orobates carried most of its weight on the hind limbs. Mostly unrestricted joint morphology further suggested that MNG 10181 was able to effectively generate propulsion with the pelvic limbs. The digital reconstruction is made available for future biomechanical studies.
AG Morphologie und Formengeschichte, Bild Wissen Gestaltung-ein interdisziplinäres Labor & Institut für Biologie, Humboldt-Universität, Berlin, Germany; Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-University, Jena, Germany.
John A
JA
Nyakatura
Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-University, Jena, Germany; Structure and Motion Laboratory, Royal Veterinary College, North Mymms, United Kingdom.
Vivian R
VR
Allen
Das Department Design, Hochschule für Angewandte Wissenschaft, Hamburg, Germany.
Jonas
J
Lauströer
Das Department Design, Hochschule für Angewandte Wissenschaft, Hamburg, Germany.
Amir
A
Andikfar
Institut für Leichtbau und Kunststofftechnik, Technical University, Dresden, Germany.
Marek
M
Danczak
Institut für Leichtbau und Kunststofftechnik, Technical University, Dresden, Germany.
Hans-Jürgen
HJ
Ullrich
Institut für Leichtbau und Kunststofftechnik, Technical University, Dresden, Germany.
Werner
W
Hufenbach
Museum der Natur, Stiftung Schloss Friedenstein, Gotha, Germany.
Thomas
T
Martens
Institut für Spezielle Zoologie und Evolutionsbiologie mit Phyletischem Museum, Friedrich-Schiller-University, Jena, Germany.
Martin S
MS
Fischer
D000818:Animals; D001835:Body Weight; D001842:Bone and Bones / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D005580:Fossils; D021621:Imaging, Three-Dimensional; D035002:Lower Extremity / Q000033:anatomy & histology* / Q000502:physiology*; D009068:Movement; D014057:Tomography, X-Ray Computed; D014714:Vertebrates / Q000033:anatomy & histology