Macroevolutionary patterns in the pelvis, stylopodium and zeugopodium of megalosauroid theropod dinosaurs and their importance for locomotor function

Lacerda, MBS; Bittencourt, JS; Hutchinson, JR

Abstract

During the Mesozoic, non-avian theropods represented one of the most successful clades globally distributed, with a wide diversity of forms. An example is the clade Megalosauroidea, which included medium- to large-bodied forms. Here, we analyse the macroevolution of the locomotor system in early Theropoda, emphasizing the Megalosauroidea. We scored the Spinosaurus neotype in a published taxon-character matrix and described the associated modifications in character states, mapping them onto a phylogeny and using these to study disparity. In the evolution of Megalosauroidea, there was the mosaic emergence of a low swollen ridge; enlargement of the posterior brevis fossa and emergence of a posterodorsal process on the ilium in some megalosauroids; emergence of a femoral head oriented anteromedially and medially angled, and appearance of posterolaterally oriented medial femoral condyles in spinosaurids. The greatest morphological disparity is in the ilium of megalosaurids; the ischium seems to have a high degree of homoplasy; there is a clear distinction in the femoral morphospace regarding megalosauroids and other theropods; piatnitzkysaurids show considerable disparity of zeugopodial characters. These reconstructions of osteological evolution form a stronger basis on which other studies could build, such as mapping of pelvic/appendicular musculature and/or correlating skeletal traits with changes in locomotor function.

Citation

Lacerda, M., Bittencourt, J., & Hutchinson, J. (2023). Macroevolutionary patterns in the pelvis, stylopodium and zeugopodium of megalosauroid theropod dinosaurs and their importance for locomotor function. Royal Society Open Science, 10(8), https://doi.org/10.1098/rsos.230481

• Journal Article Type: Article
• Acceptance Date: Jul 27, 2023
• Online Publication Date: Aug 16, 2023
• Publication Date: 2023
• Deposit Date: Sep 6, 2023
• Publicly Available Date: Sep 6, 2023
• Print ISSN: 2054-5703
• Publisher: The Royal Society
• Peer Reviewed: Peer Reviewed
• Volume: 10
• Issue: 8
• DOI: https://doi.org/10.1098/rsos.230481
• Keywords: disparity; evolution; functional morphology; locomotion; Megalosauroidea; palaeontology; SEMIAQUATIC ADAPTATIONS; SOFT-TISSUES; EVOLUTION; MUSCULATURE; BIRDS; SKULL; LINE; TYRANNOSAURUS; SPINOSAURIDAE; INFORMATION