A furcula in the Coelophysid theropodSyntarsus
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Abstract:
We report the occurrence of a furcula (fused clavicles) in both species of the Early Jurassic coelophysid theropod dinosaur Syntarsus (Coelophysidae sensu Holtz, 1994; =Coelophysis and Syntarsus and all descendants of their most recent common ancestor). The furcula is a median pectoral element formed by ontogenetic fusion of the left and right clavicles. It articulates laterally with a facet on the acromion process of the scapula, and medially with the sternum. Study of the holotype of Syntarsus kayentakatae (MNA V2623) uncovered a furcula in articulation with the left scapulocoracoid. Re-examination of elements previously identified as hyoids of Syntarsus rhodesiensis (QG 193) show these bones are actually furculae, nearly identical in morphology to that of S. kayentakatae. These specimens mark the earliest confirmed record of furculae to date, both temporally and phylogenetically. This suggests that the fusion of clavicles into furculae occurred much earlier in theKeywords:
Theropoda
Keel
Osteology
Sternum
Pectoral girdle
The sternum is central in binding the bilateral costal structures to form the anterior wall of the thorax. The airtight subatmospheric pressure cavity of the thorax during respiration and episodes of cough produces significant dynamic forces acting perpetually on its walls, influencing functions of the contained viscera. The embryonic development of the sternum concurs with that of the heart and parts of the pectoral girdle. Any imperfection of the sternum, whether congenital or iatrogenic, can significantly compromise the normal physiology of the thoracic wall and cardio-respiratory systems. Midsagittal osteochondrotomy (division) of the sternum is a necessary step to access the mediastinum for an open cardiac procedure. To return the thorax to its normal function, it is imperative that surgeons have thorough working knowledge of the surgical anatomy of the sternum and the biomechanics of an intact and disrupted thoracic wall. Patient-based outcome measures of an index cardiac surgery can only be considered conclusive if the divided sternum heals over time to have full benefit of the surgery. Here, the essential topographical anatomy and embryology of the sternum, thoracic biomechanics, fracture biology, and surgical access to the mediastinum are reviewed to provide a better understanding of the performance and importance of the healed sternum.
Sternum
Pectoral girdle
Thorax (insect anatomy)
Thoracic wall
Biomechanics
Thoracic cavity
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Abelisaurid theropods are well-know from the Cretaceous of several parts of the Southern Hemisphere, including South America, Madagascar, and Africa, but also in India and Europe. Abelisaurids are high-diverse among other theropods with several cervicocephalic specializations reaching medium/large sizes. In the present contribution, we describe a new abelisaurid (Thanos simonattoi, gen. et sp. nov.) from the São José do Rio Preto Formation, Bauru Group, Brazil (Upper Cretaceous). Thanos differs from other theropods by having a well-developed keel becoming wider and deeper posteriorly on the ventral surface; two lateral small foramina separated by a relative wide wall on each lateral surface of the centrum, and well-developed and deep prezygapophyseal spinodiapophyseal fossae. The closed sutures between the axis and odontoid suggest that Thanos had reached a subadult/adult stage before death. Thanos is phylogenetically related to Brachyrostra abelisaurid. The keel on the ventral axial centrum in abelisauroids is here interpreted as a homoplastic condition that became more pronounced towards the phylogeny. The presence of well-developed keel in Thanos suggests that this taxon could be more derived than other abelisaurids. Finally, even though abelisaurids could reach large sizes, Thanos shared the environment with a larger theropod that was probably close to Megaraptora.
Theropoda
Keel
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Abstract Therizinosaurs are unusual theropods from the Upper Cretaceous of Asia and North America. North American representatives include Falcarius utahensis from central Utah, Nothronychus mckinleyi from west central New Mexico, and N. graffami from southern Utah. Nothronychus was quite large, with well‐developed forelimbs and pectoral girdle. In many respects, however, these structures were typical for conventional carnivorous theropods, although therizinosaurs have been hypothesized to be herbivorous using anatomical and functional inferences. There is no indication of increased range of motion within the forelimbs, as might be predicted for derived non‐avian theropods. The muscular anatomy of the pectoral girdle and forelimb of Nothronychus is reconstructed using visible muscle scars, data from extant birds and crocodilians, and models for other theropods. The osteology and inferred musculature is a mosaic of primitive and derived characters for theropods. A fossa pneumotricipitales may have been present in the proximal humerus. There was a well‐developed fossa brachialis in the distal humerus. The epicleidium of the furcula is deflected, reflecting either taphonomic deformation or possibly accommodation of M. supracoracoideus in a triosseal canal, but such a development has yet to be described in any non‐avian theropod. In many respects, the other muscular results were quite similar to those inferred for dromaeosaurs.
Theropoda
Pectoral girdle
Forelimb
Myology
Osteology
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Theropoda
Pectoral girdle
Forelimb
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The etiology of the keel chest deformity, still being a hypothetical explanation and a matter of investigation, is probably caused by secondary elongation of rib cartilages during growth spurts, which result in prominences of the rib themselves or are conjoined with a protrusion of the sternum (Figs. and 2a–c) to a variable extent and shape. Therefore, the surgical correction is aimed at shortening the affected cartilages with or without sternum osteotomies.
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Sternum
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In 1976 John Ostrom published an enlightening paper about the anatomical transformations in the shoulder girdle and forelimb elements along the origin of birds. Most of his ideas were based on comparing Archaeopteryx lithographica with the extant New World vulture Cathartes aura . Ostrom offered innovative ideas about range of movements and function of wing elements in the basal bird Archaeopteryx . Further, he explored anatomical transformations that may have occurred at early stages of the evolution of flight and established several hypothetical steps toward the acquisition of flapping flight in modern birds. Since then, however, our understanding of paravian diversity and anatomy has increased dramatically. Based on novel information derived from recent experiments, and currently available anatomical evidence of basal paravians, the present paper aims to review some important topics on pectoral girdle anatomy related to flight origins. Further, a brief analysis of pectoral girdle osteology and myology of the extant paleognath Rhea americana is also included with the aim to test whether Ostrom’s ideas still remain valid under this new context, based on available phylogenetic and anatomical frameworks.
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Theropoda
Osteology
Myology
Ecomorphology
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The present study provides description of the osteology of Skipper Frog Euphlyctis cyanophlyctis. Seven adult specimens of E. cyanophlyctis from northern Western Ghats of India were cleared and double stained for studying osteological characteristics. The baseline description of osteological characters of cranial and post-cranial elements (paired nasals, tubular sphenethmoid, well-developed vomerine teeth, arciferal pectoral girdle, fan-shaped omosternum, cartilaginous W-shaped xiphisternum, hind limb with longest cylindrical humerus, V-shaped pectoral girdle and phalangeal appendages) provided in present study will help in further taxonomic investigations of the genus Euphlyctis. Further, the baseline information on osteology of Skipper frog will serve as a reference material for investigations related to malformations, either in this or related species. We also provide first observation on sacro-pelvic malformation in one of the studied specimens.
Osteology
Pectoral girdle
Clearance
Appendage
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The sternum is part of the forelimb appendicular skeleton found in most terrestrial vertebrates and has become adapted across tetrapods for distinctive modes of locomotion. We review the regulatory mechanisms underlying sternum and forelimb development and discuss the possible gene expression modulation that could be responsible for the sternal adaptations and associated reduction in the forelimb programme found in flightless birds. In three phylogenetically divergent vertebrate lineages that all undertake powered flight, a ventral extension of the sternum, named the keel, has evolved independently, most strikingly in volant birds. In flightless birds, however, the sternal keel is absent, and the sternum is flattened. We review studies in a variety of species that have analysed adaptations in sterna morphology that are related to the animal’s mode of locomotion on land, in the sky and in water.
Sternum
Keel
Forelimb
Appendicular skeleton
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The current study was designed with the aim to study the gross morphological features of the sternum in four dead birds of Common Moorhen. The sternum gives attachment to important flight muscles in birds. The dorsal view of sternal body of Common Moorhen was roughly pyramidal. The average length of sternal body was 4.2 centimetres. Sternal keel was highly developed. The average height of sternum was 1.1 centimetres, whereas the curvature length of keel was 4.7 centimetres.
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Keel
Sterna
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Keel
Pectoral girdle
Sternum
Myology
Bird flight
Shoulder girdle
Pectoralis Muscle
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