An integrative phylogenetic and extrapolatory approach to the reconstruction of dromaeosaur (Theropoda: Eumaniraptora) shoulder musculature

Abstract

Dromaeosauridae is the sister taxon of the Avialae; thus, an investigation of dromaeosaur shoulder girdle musculature and forelimb function provides substantial information regarding changes in the size and performance of the theropod shoulder girdle musculature leading to avian powered flight. Twenty-two shoulder girdle muscles were reconstructed for the dromaeosaurid shoulder apparatus, based on phylogenetic inference, which involves the comparison of lepidosaurian, crocodilian and avian musculature, and extrapolatory inference, which involves a secondary comparison with functional analogues of theropods. In addition to these comparative methodologies, osteological correlates of shoulder musculature preserved in eumaniraptorans are identified, and comparisons with those of extant archosaurs allow these muscles to be definitively inferred in dromaeosaurids. This muscle reconstruction provides a foundation for subsequent investigation of differences in muscular attachment and function, based on scapulocoracoid morphology, across the theropod lineage leading to birds.

Soft-tissue anatomy of the Plesiosaur pectoral girdle inferred from basal Eosauropterygia taxa and the extant phylogenetic bracket

“…As a whole this ligament prevents anterior displacement of the pectoral girdle, and it is the origin of some extrinsic limb muscles, e.g., triceps heads (Peterson, 1973). The topology of the ligament and respective attachments seen in lizards is also verified in crocodilians (see Russell and Bauer, 2008;Jasinoski et al, 2006). Scapulohumeral ligament.…”

“…The scapulosternal component of the medial scapulosternal ligament attaches in a similar manner in crocodilians (Jasinoski et al, 2006). Due to the highly derived condition in eosauropterygians the reconstruction of the attachments of this ligament (Figure 3) is difficult.…”

“…This ligament serves as an origin of the triceps to the scapular head, but also helps maintain the integrity of the glenohumeral joint (Peterson, 1973). Jasinoski et al (2006) describe this tendon in crocodilians just as in lizards, thus we can infer an equivalent topology to Eosauropterygia (Level I of inference, Figure 3). Considering Hypothesis I or II for the topological change from basal neodiapsids and eosauropterygians, which implies assuming the glenoid as a fixed point, the reconstruction suggested here corresponds topologically to that of crocodilians and squamates.…”

Three‐dimensional skeletal kinematics of the shoulder girdle and forelimb in walking Alligator

“…Given their phylogenetic position, living crocodylians help anchor the extant phylogenetic bracket for extinct archosaurs (Witmer, 1995;Allen et al 2010). For example, efforts to reconstruct aspects of limb anatomy and function in Mesozoic dinosaurs and the origin of avian flight rely heavily on crocodylian morphology (Nicholls & Russell, 1985;Jenkins, 1993;Paul & Christiansen, 2000;Jasinoski et al 2006).…”

Morphology and kinematics of feeding in hagfish: possible functional advantages of jaws

“…soft tissue and behavior) determine the degree of likelihood (level of inference) of obscure traits occurring in extinct taxa (Witmer, 1995). EPB is a wellsupported method for reconstructing unclear scenarios in a phylogenetic context (Barrett and Rayfield, 2006;Carrano, 2000;Erickson et al, 2002;Jasinoski et al, 2006;Perry and A. J. Clark and A. P. Summers…”