Pectoral Anatomy Research Articles

Furcula Diversity Within the Avian Flight Apparatus

A major unknown in avian biology is the morphological basis of flight style diversity. While certain aspects of avian pectoral anatomy, such as an enlarged sternum and hypertrophied pectoral muscles, clearly relate to aerial locomotion in general, the finer details of form-function correspondence are less apparent. Nevertheless, furcula shape has been used to infer flight style in extinct avians because the furcula is the cranial origin of the largest flight muscle, m. pectoralis, in most extant birds. However, previous studies, which examined the furcula in isolation, indicate only a modest correlation between furcula shape and flight style. We hypothesized that the relationship of the furcula to flight style may be heavily mediated by other aspects of pectoral anatomy, particularly furcula orientation and flight muscle morphology. We used computed tomography and digital dissection techniques to collect in situ morphological data on a large (n=108) and diverse (21 orders) sample of formalin-fixed specimens. While some specimens required the addition of Lugol's iodine to visualize soft tissue, most specimens did not require contrast enhancement to permit bone and muscle reconstruction. We found moderate correspondence between flight style and furcula shape consistent with previous studies (e.g., soaring birds have flatter, more V-shaped furculae), however the magnitude of shape differences between flight style and taxonomic categories was smaller, perhaps due to different measurement techniques. Novel measures of furcular orientation in the pectoral girdle revealed that larger, slower-flapping birds tend to have more cranially-positioned furculae, which may relate to a greater need for wing protraction via m. pectoralis. Further, the centers-of-mass of the main pectoral muscles tend to be more cranial in large birds with more laterally-bowed furculae. In most measures, hummingbirds did not group with birds of similar mass or furcula shape, likely owing to their kinematically-unique flight style. Overall, our findings recommend caution in inferring flight style from furcula shape alone. Rather, furcula shape may be better viewed as part of a larger functional unit including the sternum, coracoids, and major flight muscles.

A new species of Metoposaurus from the Late Triassic of Portugal and comments on the systematics and biogeography of metoposaurid temnospondyls

ABSTRACTMetoposaurids are a group of temnospondyl amphibians that filled crocodile-like predatory niches in fluvial and lacustrine environments during the Late Triassic. Metoposaurids are common in the Upper Triassic sediments of North Africa, Europe, India, and North America, but many questions about their systematics and phylogeny remain unresolved. We here erect Metoposaurus algarvensis, sp. nov., the first Metoposaurus species from the Iberian Peninsula, based on several new specimens from a Late Triassic bonebed in Algarve, southern Portugal. We describe the cranial and pectoral anatomy of M. algarvensis and compare it with other metoposaurids (particularly other specimens of Metoposaurus from Germany and Poland). We provide a revised diagnosis and species-level taxonomy for the genus Metoposaurus, which is currently represented with certainty by three European species (M. diagnosticus, M. krasiejowensis, M. algarvensis). We also identify cranial characters that differentiate these three species, and may have phylogenetic significance. These include features of the braincase and mandible, which indicate that metoposaurid skulls are more variable than previously thought. The new Portuguese bonebed provides further evidence that metoposaurids congregated in fluvial and lacustrine settings across their geographic range and often succumbed to mass death events. We provide an updated paleogeographic map depicting all known metoposaurid occurrences, which shows that these temnospondyls were globally distributed in low latitudes during the Late Triassic and had a similar, but not identical, paleogeographic range as phytosaurs.http://zoobank.org/urn:lsid:zoobank.org:pub:083C80C6-0AB6-49E1-A636-6A8BDBC06A47

3D geometric morphometric analysis of phenotypic plasticity in the pectoral girdle of a basal actinopterygiian fish

Polypterids are a basal group of actinopterygian fishes that represent a possible living analogue for the evolutionary transition from fish to tetrapods for number of reasons, including their ability to walk on land using robustly, muscled pectoral fins. We examined the phenotypic plasticity in the pectoral anatomy of Polypterus senegalus induced by habitual terrestrial locomotion. Fish were reared in a fully terrestrial environment where they were forced to live and locomote over land for up to two years. MicroCT scans were taken of the experimental walking group and a swimming control group. 3D reconstructions of the pectoral anatomy were described using spherical harmonics, a 3D extension of elliptic Fourier analysis. Here we present a geometric morphometric analysis of morphological differences in the pectoral anatomy between swimming and walking fish, and discuss potential small‐scale morphological changes in response to the functional demands of terrestrial locomotion during the fin‐to‐limb transition.Grant Funding Source: NSERC, Canada Research Chair, Tomlinson Postdoctoral Fellowship

Dosimetric Coverage of Level I and II Lymph Nodes by Opposed Tangent Fields in Patients Undergoing PMRT with Tissue Expanders

To define the dosimetric coverage of level I and II lymph nodes regions in patients treated with tangent fields following mastectomy and tissue expander placement. Ten patients were identified who underwent mastectomy followed by immediate tissue expander placement followed by tangent field only radiation therapy planning. 9 patients had full axillary lymph node dissection. Eight patients also received bilateral mastectomy and bilateral expander placement. Regarding subsequent reconstruction of the treated breast, 8 patients had subpectoral implants and 2 had myocutaneous latissimus dorsi flaps. All patients underwent 3D planning with opposed tangential beams designed to encompass the chestwall with tissue expander. No patients received directed supraclavicular or other nodal irradiation. The axillary levels I and II were contoured retrospectively using the RTOG atlas and dose distributions to volumes of interest were determined using tabular dose volume histograms. All defined breast volumes received ≥ 95% of the prescribed dose. The mean axillary level I and II volume was 84.9 cm3 (range, 45.3 -138.6 cm3). No patient had complete coverage of the defined axillary volume by the 95% isodose line; the mean coverage of the axilla by the 95% isodose line was 32.4% (range, 3 - 65.4%). The mean volume of the axilla covered by the 95% isodose line was 28.3 cm3 (range, 1.49 - 90.6 cm3). In this study no patient received a therapeutic dose to levels I and II of the axilla. The volume of the axilla covered by the 95% isodose line is lower than published reports of patients treated following breast conserving surgery with tangents only. This may be due to anatomic definitions of the axilla; in particular, the superior extent may be greater in the RTOG atlas than definitions used in previous studies. On inspection of the dose distribution of the 95% isodose line, the superior aspect of Level II is never covered in contrast to the inferior border which has ample coverage. Difficulty exists in delineating the caudal extent of axillary level I based on the RTOG definition of insertion of the pectoralis muscle into the ribs, due to disruptions in normal pectoral anatomy caused by the tissue expander. As the evidence supporting post-mastectomy radiotherapy (PMRT) in those with 1-3 nodes increases, more patients with minimal axillary tumor burden are undergoing PMRT, This analysis suggests that in pts undergoing PMRT with tissue expanders in place, incidental doses delivered by opposed tangents to the Level I and II regions, as defined by the RTOG atlas, do not provide adequate dosimetric coverage of these regions. This should be considered when designing PMRT treatment fields.

Pectoral anatomy of Tribodus limae (Elasmobranchii: Hybodontiformes) from the Lower Cretaceous of northeastern Brazil

ABSTRACT New, undescribed material of the hybodont shark Tribodus limae, from the Lower Cretaceous of northeastern Brazil, provides new information on the pectoral endoskeleton in this taxon. This allows for a revision of its pectoral morphology, which may be broadly applicable to other Hybodontoidei. Four new specimens of Tribodus with well-preserved pectoral girdles are described, including the first complete, three-dimensionally preserved hybodont scapulocoracoid and partial pectoral fin. These specimens permit examination of the posterior surface of the scapulocor-acoid, not visible in previously described hybodonts. Overall pectoral morphology of Tribodus is similar to that of other hybodontiforms and neoselachians. However, the new material shows that the pectoral articulation in Tribodus comprises an oblique posterior ridge on the scapulocoracoid, unlike previous reconstructions of pectoral anatomy in Tribodus and other hybodonts based on two-dimensionally preserved specimens. However, other elasmobranchs, including many neoselachians, Orthacanthus, and ctenacanths, also have an oblique posterior articulation, indicating that this feature may be primitive for elasmobranchs. The pectoral articulation of Tribodus differs noticeably from that of Cladoselache and similar Paleozoic chondrichthyans, which have an elongated, laterally positioned articular process, and from the outgroup (osteichthyans, acanthodians and placoderms). Tribodus also differs from the Paleozoic hybodontiform Ony-choselache in which the articular region comprises a laterally positioned glenoid fossa and posterior condyle. Tribodus has an additional diazonal foramen not found in other hybodonts. Other pectoral features of Tribodus are in agreement with previous phylogenetic hypotheses, supporting the position of Tribodus within Hybodontoidei.

The pectoral anatomy of selected Ostariophysi. II. The Cypriniformes and siluriformes.

The pectoral myology and osteology of the cyprinoids Notemigonus crysoleucas, the golden shiner, and Catostomus commersonnii, the common white sucker, resemble those of generalized, lower teleosts in structure and function, except in features related to the manipulation of the massive fifth ceratobranchial of cyprinoids by muscles attaching on the girdle. Catostomus is more specialized in having unique intercostal muscles to the girdle, complex subclavian arteries and lack of a superficial trapezius muscle. The bony pectoral anatomy of the siluriform, Ictalurus nebulosus, the brown bullhead, is highly specialized in relation to the presence and locking of the massive pectoral spine which is formed of fused dorsal and ventral propterygial rays; there is consolidation of the girdle through fusion of bones, presence of unique stabilizing bony structures, firm symphyseal union of bilateral girdles and the presence of friction-surfaces of girdle and spine for locking. The movements of the spine are specialized in the greater guidance offered by the girdle. Myological specializations are related mainly to ventral appendicular muscles which lock the spine. The nervous and arterial systems are generalized.

The pectoral anatomy of selected Ostariophysi. I. The Characiniformes.

The muscles and bones of the pectoral fin of Serrasalmus nattereri, the piranha, resemble those of generalized, lower teleosts with specializations related to a body shape adapted for high-speed carnivory; the pectoral fins being highly mobile with strong ligaments to the rays. The presence of two occipital nerves appears primitive, while the emergence of the subclavian artery within the branchial cavity, as in Gasteropelecus sternicla, appears specialized. The muscles and bones of the latter fish, a fresh-water flying fish, are specialized for self-propelled, aerial flight in the fusion of the right and left girdles greatly expanded for insertions of complex appendicular (flight) muscles, and in the consolidation of the rays and radials into one functional unit moving vertically in flight through contraction of vertical, massive ventral flight muscles. The bony pectoral anatomy of Electrophorus electricus, the electric eel, is specialized in having a mobile joint between the primary girdle and the cleithrum, the former being suspended vertically from the cleithrum by ligaments. The proximal radials and rays are very numerous and vertically aligned. The cleithrum is shaped to accommodate the extensive sternohyoid and pharyngocleithral muscles. The sheet-like appendicular muscles extend beyond the special joint and control its movement. The deeper muscles do not cross this joint. The arterial system is specialized in lacking a deep brachial artery.

THE PECTORAL ANATOMY OF PANTODON BUCHHOLZI PETERS (A FRESHWATER FLYING FISH) AND THE RELATED OSTEOGLOSSIDAE

Pantodon buchholzi, a small west African osteoglossid, is thought to be a freshwater flying fish. Its expanded pectoral fins and its body‐form would add credence to this supposition, whilst its pectoral musculature suggests the way in which flight could be effected.Anatomical studies on the pectoral girdle and musculature show that both are remarkably developed and are probably unique amongst the teleosts. The girdle is characterized by the hypertrophy of its mesocoracoid and correlated hyperdevelopment of certain abductor and adductor muscles. Unlike the deep abductor muscles of other fishes, those of Pantodon originate on the mesial aspect of the girdle and pass to the exterior through an enlarged coracoid foramen. The large blocks of deep abductors fill the girdle and even surround part of the pericardium. The superficial abductors are also hypertrophied and even project posteriorly away from the body‐line. The articulation of the pectoral fins is unusual since it does not allow the fins to be folded back against the body; the only fin movement possible is in the vertical plane.Apparently the pectoral musculature is highly adapted to spread and keep open the pectoral fine, at the samo time imparting a powerful dorso‐ventral motion to the fins. To this extent, Pantodon seems capable of true, flapping flight.In both its pectoral osteology and myology, and in body‐form, Pantodon differs markedly from other flying fishes. The latter, although belonging to numerous and phyletically distinct groups, all show convergent adaptations for flight.The pectoral anatomy of the related Osteoglossidæ (Heterotis niloticus and Osteoglossum bicirrhosum) is described. That of Heterotis does not differ greatly from the generalized isospondylid type, but the anatomy of Osteoglossum is intermediate between the Heterotis condition and that of Pantodon. Many characteristics of the Pantodon girdle and myology are clearly foreshadowed in Osteoglossum.The taxonomic status of P. buchholzi has long been uncertain, but the details of its pectoral anatomy and syncranial osteology clearly confirm its place in the Osteoglossidæ and suggest a relatively close relationship with Osteoglossum and Scleropages.