Brachiocephalic Muscular Arrangements in Cavioid Rodents (Caviomorpha): a Functional, Anatomical, and Evolutionary Study
- PDF / 2,137,362 Bytes
- 13 Pages / 595.276 x 790.866 pts Page_size
- 42 Downloads / 131 Views
ORIGINAL PAPER
Brachiocephalic Muscular Arrangements in Cavioid Rodents (Caviomorpha): a Functional, Anatomical, and Evolutionary Study César M. García-Esponda 1
&
Ana R. Calanoce 2 & Adriana M. Candela 3
Accepted: 28 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In cursorial mammals, reduction or loss of the clavicle is usually associated with the constitution of the m. brachiocephalicus, a continuous muscle that extends from head and neck regions to the forelimb, protracting it during locomotion. Among caviomorph rodents, the Cavioidea are characterized by many adaptations that improve running performance, such as the presence of a brachiocephalic configuration of the mm. cleidomastoideus, cleido-occipitalis, and deltoideus pars clavicularis, a feature that was interpreted as one of the main modifications for speed in running. However, a comprehensive analysis of this muscular configuration in the Cavioidea is not yet available. In this study, we analyze the morphological diversity, homologies, functions, and evolutionary changes of those shoulder muscles in cavioids that constitute the m. brachiocephalicus in cursorial mammals. We hypothesize that a brachiocephalic muscular arrangement of these muscles has evolved in this group in relation to a swift mode of locomotion. Muscular dissections on seven species of cavioids were performed while myological data on three other species were taken from the literature. Our results indicate that all cavioids have a brachiocephalic arrangement of the mm. cleidomastoideus, cleido-occipitalis, and deltoideus pars clavicularis, whereas a second brachiocephalic arrangement constituted by the mm. omotransversarius and trapezius pars cervicalis is present only in the larger cavioids. Both muscular configurations act in protracting the forelimb during the gait, but we also hypothesize that the particular disposition of the m. omotransversarius around the shoulder joint of larger cavioids could also assist in the stabilization of this joint during fast half-bounding locomotion. Keywords Myology . Brachiocephalic arrangement . Functional anatomy . Evolution . Cavioid rodents
Introduction Reduction or loss of the clavicle is common in mammals that employ the forelimb for support and locomotion only, and is usually associated with a particular rearrangement of the muscles that insert on that bone to form a continuous muscle from head and neck to forelimb, the m. brachiocephalicus (= cephalohumeralis, mastoidohumeralis) (Jenkins 1974). The constitution of a brachiocephalic muscle by fusion of infraand supraclavicular muscles is characteristic of cursorial
* César M. García-Esponda [email protected] 1
Cátedra Zoología III Vertebrados, Facultad de Ciencias Naturales y Museo, La Plata, Argentina
2
Mendoza, Argentina
3
División Paleontología Vertebrados, Museo de La Plata, La Plata, Argentina
mammals (e.g., carnivorans, ungulates), representing one of the most striking adaptations of mammalian anatomy (Jouffroy 1971). Funct
Data Loading...
