Skip to main content

Evolution of the iliosacral joint in diapsid phylogeny

Buy Article:

$39.00 plus tax (Refund Policy)


The biomechanical advantages of the pelvic structure are inspected in terms of the relative position of the iliosacral joint with respect to the acetabulum. Disarticulated bone material from Lower Triassic karst deposits from Southern Poland provides a unique opportunity to study both sides of the ilium in several early diapsids. Extant squamate material provides a good reference source for this study, and permits the reconstruction of a scenario for iliac evolution in the two neodiapsid clades: Lepidosauromorpha and Archosauromorpha. Ancestrally, the iliosacral joint was probably dorsal and posterior to the acetabulum level. Facultative bipedality may evolve when the iliosacral joint is situated relatively close to the acetabulum, as is common in the Iguania. The more postero-dorsal position of the joint in many non-iguanians correlates with a tendency to limb reduction that develops in parallel in several subgroups. This divergence in locomotor adaptation may have been important in the divergence of the squamate clades. The ventral extension of the iliosacral joint, to overlap the medial side of the acetabulum, is considered a possible synapomorphy of the Archosauriformes, and a possible prerequisite for the obligatory bipedality that eventually evolved in crown group archosaurs. The inclusion of the last dorsal vertebra into the sacrum probably preceded this trend in archosauromorph phylogeny.


Document Type: Research Article


Publication date: 2008-09-01

More about this publication?
  • Neues Jahrbuch für Geologie und Paläontologie continuously publishes current original contributions from all fields of geology, ever since its foundation in 1807. All published contributions are in the English language.
  • Editorial Board
  • Information for Authors
  • Subscribe to this Title
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more