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Integrative Organismal Biology (Oxford,... 2022During locomotion, cervical muscles must be active to stabilize the head as the body accelerates and decelerates. We hypothesized that cervical muscles are also part of...
During locomotion, cervical muscles must be active to stabilize the head as the body accelerates and decelerates. We hypothesized that cervical muscles are also part of the linked chain of axial muscles that provide core stabilization against torques applied to the hip joint by the extrinsic muscles of the legs. To test whether specific cervical muscles play a role in postural stabilization of the head and/or core stabilization of the pelvic girdle, we used surface electromyography to measure changes in muscle activity in response to force manipulations during constant speed running and maximum effort counter-movement jumps. We found that doubling the mass of the head during both running and maximum effort jumping had little or no effect on (1) acceleration of the body and (2) cervical muscle activity. Application of horizontal forward and rearward directed forces at the pelvis during running tripled mean fore and aft accelerations, thereby increasing both the pitching moments on the head and flexion and extension torques applied to the hip. These manipulations primarily resulted in increases in cervical muscle activity that is appropriate for core stabilization of the pelvis. Additionally, when subjects jumped maximally with an applied downward directed force that reduced acceleration and therefore need for cervical muscles to stabilize the head, cervical muscle activity did not decrease. These results suggest that during locomotion, rather than acting to stabilize the head against the effects of inertia, the superficial muscles of the neck monitored in this study help to stabilize the pelvis against torques imposed by the extrinsic muscles of the legs at the hip joint. We suggest that a division of labor may exist between deep cervical muscles that presumably provide postural stabilization of the head versus superficial cervical muscles that provide core stabilization against torques applied to the pelvic and pectoral girdles by the extrinsic appendicular muscles.
PubMed: 35854827
DOI: 10.1093/iob/obac021 -
PeerJ 2022Hutt et al., 2001 from the Lower Cretaceous Wessex Formation (part of the Wealden Supergroup) of the Isle of Wight, southern England, is described in detail, compared...
Hutt et al., 2001 from the Lower Cretaceous Wessex Formation (part of the Wealden Supergroup) of the Isle of Wight, southern England, is described in detail, compared with other theropods, and evaluated in a new phylogenetic analysis. is represented by a single individual that would have been c. 4.5 m long; it preserves the anterior part of the skull, a partial forelimb and pectoral girdle, various cervical, dorsal and caudal vertebrae, rib fragments, part of the ilium, and hindlimb elements excluding the femur. Lack of fusion with regard to both neurocentral and sacral sutures indicates subadult status. possesses thickened, fused, pneumatic nasals with deep lateral recesses, elongate, tridactyl forelimbs and a tyrannosaurid-like scapulocoracoid. The short preantorbital ramus of the maxilla and nasals that are approximately seven times longer than they are wide show that was not longirostrine. A posterodorsally inclined ridge on the ilium's lateral surface fails to reach the dorsal margin: a configuration seen elsewhere in . is not arctometatarsalian. Autapomorphies include the presence of curving furrows on the dentary, a block-like humeral entepicondyle, and a distoproximally aligned channel close to the distolateral border of the tibia. Within Tyrannosauroidea, is phylogenetically intermediate between Proceratosauridae and and the clade that includes , Megaraptora, and Tyrannosauridae. We do not find support for a close affinity between and . Our analysis supports the inclusion of Megaraptora within Tyrannosauroidea and thus increases Cretaceous tyrannosauroid diversity and disparity. A proposal that might belong within Megaraptora, however, is based on character states not present in the taxon. Several theropods from the Wessex Formation are based on material that overlaps with the holotype but none can be shown to be synonymous with it.
Topics: Animals; Phylogeny; Fossils; Osteology; Skull; Tibia; Dinosaurs
PubMed: 35821895
DOI: 10.7717/peerj.12727 -
Anatomy & Cell Biology Jun 2022Anatomical variation is defined as normal flexibility in the topography and morphology of body structures. Such variations are not uncommon in muscles, particularly in...
Anatomical variation is defined as normal flexibility in the topography and morphology of body structures. Such variations are not uncommon in muscles, particularly in the upper limb. Subclavius muscle (SM) has a proximal attachment to the first costochondral junction and the muscle fibers are then directed upwards and laterally to get attached distally to the subclavian groove of the clavicle. Having similar attachments as the subclavius, the costocoracoid ligament (CCL) is the thickening of the proximal part of clavipectoral fascia extending up to the coracoid process. Both SM and CCL help in the maintenance of smooth movements of the pectoral girdle and both may not always be present. Absent SM may be due to anomalous development from the muscle matrix that also forms the inferior belly of the omohyoid apart from the SMs. This anatomical variation may be associated with thickened CCLs and can be correlated to the smooth functioning of the pectoral girdle.
PubMed: 35773222
DOI: 10.5115/acb.21.246 -
Anatomical Record (Hoboken, N.J. : 2007) Oct 2022The holotype of Junggarsuchus sloani, from the Shishugou Formation (early Late Jurassic) of Xinjiang, China, consists of a nearly complete skull and the anterior half of...
The holotype of Junggarsuchus sloani, from the Shishugou Formation (early Late Jurassic) of Xinjiang, China, consists of a nearly complete skull and the anterior half of an articulated skeleton, including the pectoral girdles, nearly complete forelimbs, vertebral column, and ribs. Here, we describe its anatomy and compare it to other early diverging crocodylomorphs, based in part on CT scans of its skull and that of Dibothrosuchus elaphros from the Early Jurassic of China. Junggarsuchus shares many features with a cursorial assemblage of crocodylomorphs, informally known as "sphenosuchians," whose relationships are poorly understood. However, it also displays several derived crocodyliform features that are not found among most "sphenosuchians." Our phylogenetic analysis corroborates the hypothesis that Junggarsuchus is closer to Crocodyliformes, including living crocodylians, than are Dibothrosuchus and Sphenosuchus, but not as close to crocodyliforms as Almadasuchus and Macelognathus, and that the "Sphenosuchia" are a paraphyletic assemblage. D. elaphros and Sphenosuchus acutus are hypothesized to be more closely related to Crocodyliformes than are the remaining non-crocodyliform crocodylomorphs, which form several smaller groups but are largely unresolved.
Topics: Animals; Fossils; Head; Phylogeny; Skull; Tomography, X-Ray Computed
PubMed: 35699105
DOI: 10.1002/ar.24949 -
The Journal of Chiropractic Education Oct 2022The aim of this study is to conduct a pilot survey to determine core anatomy content for chiropractic curriculum based on the perception of chiropractors and anatomy...
OBJECTIVE
The aim of this study is to conduct a pilot survey to determine core anatomy content for chiropractic curriculum based on the perception of chiropractors and anatomy educators involved in teaching in an Australian chiropractic program.
METHODS
A survey of anatomical structures previously used in a medical survey, with similar criteria for synthesizing responses, was used and classified according to whether the respondents rated an item as essential, important, acceptable, or not required in a chiropractic program. The item was scored as core if ≥60% of respondents rated it essential, recommended if 30%-59% rated it essential, not recommended if 20%-29% rated it essential, or not core if <20% rated it essential.
RESULTS
The respondents rated 81.6% of all musculoskeletal concepts as core and 18.4% as recommended, 88.8% of the vertebral column items as core, and 11.2% of the items as recommended, 69.4% upper limb and pectoral girdle items as core, 23.7% of items as recommended, 5.5% as not recommended and 1.3% as not core items for inclusion, 85.3% of all lower limb and pelvic girdle items as core, 14.4% as recommended and 0.3% not recommended.
CONCLUSION
Chiropractors and anatomists involved in teaching in an Australian chiropractic program rated most musculoskeletal items as essential for inclusion in a chiropractic teaching program to ensure adequate preparation for safe practice and to promote alignment with the standards of anatomy education delivered into the clinical professions.
PubMed: 35561322
DOI: 10.7899/JCE-21-18 -
ELife Mar 2022The morphology of the pectoral girdle, the skeletal structure connecting the wing to the body, is a key determinant of flight capability, but in some respects is poorly...
The morphology of the pectoral girdle, the skeletal structure connecting the wing to the body, is a key determinant of flight capability, but in some respects is poorly known among stem birds. Here, the pectoral girdles of the Early Cretaceous birds and are reconstructed for the first time based on computed tomography and three-dimensional visualization, revealing key morphological details that are important for our understanding of early-flight evolution. exhibits a double articulation system (widely present in non-enantiornithine pennaraptoran theropods including crown birds), which involves, alongside the main scapula-coracoid joint, a small subsidiary joint, though variation exists with respect to the shape and size of the main and subsidiary articular contacts in non-enantiornithine pennaraptorans. This double articulation system contrasts with in which a spatially restricted scapula-coracoid joint is formed by a single set of opposing articular surfaces, a feature also present in other members of Enantiornithines, a major clade of stem birds known only from the Cretaceous. The unique single articulation system may reflect correspondingly unique flight behavior in enantiornithine birds, but this hypothesis requires further investigation from a functional perspective. Our renderings indicate that both and had a partially closed triosseal canal (a passage for muscle tendon that plays a key role in raising the wing), and our study suggests that this type of triosseal canal occurred in all known non-euornithine birds except , representing a transitional stage in flight apparatus evolution before the appearance of a fully closed bony triosseal canal as in modern birds. Our study reveals additional lineage-specific variations in pectoral girdle anatomy, as well as significant modification of the pectoral girdle along the line to crown birds. These modifications produced diverse pectoral girdle morphologies among Mesozoic birds, which allowed a commensurate range of capability levels and styles to emerge during the early evolution of flight.
Topics: Animals; Biological Evolution; Birds; Fossils; Phylogeny; Wings, Animal
PubMed: 35356889
DOI: 10.7554/eLife.76086 -
Anatomical Record (Hoboken, N.J. : 2007) Dec 2022Exquisite discoveries and new interpretations regarding an enigmatic group of cursorial avemetatarsalians led to a new phylogenetic hypothesis regarding pterosaur...
Exquisite discoveries and new interpretations regarding an enigmatic group of cursorial avemetatarsalians led to a new phylogenetic hypothesis regarding pterosaur affinities. Previously thought to be dinosaur precursors, lagerpetids are now considered to be the closest relatives to pterosaurs. This new hypothesis sheds light on a new explorable field, especially regarding the character acquisition and evolution within the pterosaur lineage. In the present study, the morphospace occupation of distinct skeletal regions of lagerpetids within the morphological spectrum of avemetatarsalians is investigated. This approach indicates which portions of the skeleton are more similar to the anatomy of pterosaurs and which portions present different homoplastic signals. The analyses demonstrate that the craniomandibular traits of lagerpetids are pterosaur-like, the pectoral girdle and forelimb are dinosauromorph-like and the axial skeleton and the pelvic girdle and hindlimb are unique and highly specialized among the analyzed sample. So, despite the close phylogenetic relationships, the postcranial skeleton of lagerpetids and pterosaurs are very different. The occurrence of two distinct and highly specialized groups of pterosauromorphs coexisting with a wide ecological range of dinosauromorphs during the Triassic suggests pressure for new niches occupation.
Topics: Animals; Fossils; Phylogeny; Biological Evolution; Dinosaurs; Bone and Bones; Occupations
PubMed: 35199946
DOI: 10.1002/ar.24904 -
Scientific Reports Jan 2022We here report on a well-preserved juvenile lizard specimen in Albian amber (ca. 110 mya) from the Hkamti site (Myanmar). This new taxon is represented by an...
We here report on a well-preserved juvenile lizard specimen in Albian amber (ca. 110 mya) from the Hkamti site (Myanmar). This new taxon is represented by an articulated skull and the anterior portion of the trunk, including the pectoral girdle and forelimbs. The scleral ossicles and eyelid are also visible, and the specimen exhibits pristine detail of the integument (of both head and body). In a combined molecular and morphological analysis, it was consistently recovered as a scincoid lizard (Scinciformata), as sister to Tepexisaurus + Xantusiidae. However, the phylogenetic position of the new taxon should be interpreted with caution as the holotype is an immature individual. We explored the possibility of miscoding ontogenetically variable characters by running alternative analyses in which these characters were scored as missing data for our taxon. With the exception of one tree, in which it was sister to Amphisbaenia, the specimen was recovered as a Pan-xantusiid. Moreover, we cannot rule out the possibility that it represents a separate lineage of uncertain phylogenetic position, as it is the case for many Jurassic and Cretaceous taxa. Nonetheless, this fossil offers a rare opportunity to glimpse the external appearance of one group of lizards during the Early Cretaceous.
Topics: Amber; Animals; Biological Evolution; Fossils; Integumentary System; Lizards; Myanmar; Phylogeny; X-Ray Microtomography
PubMed: 35102237
DOI: 10.1038/s41598-022-05735-5 -
Journal of the American Veterinary... Jan 2022To determine the prevalence of pectoral girdle fractures in wild passerines found dead following presumed window collision and evaluate the diagnostic accuracy of...
OBJECTIVE
To determine the prevalence of pectoral girdle fractures in wild passerines found dead following presumed window collision and evaluate the diagnostic accuracy of various radiographic views for diagnosis of pectoral girdle fractures.
SAMPLE
Cadavers of 103 wild passerines that presumptively died as a result of window collisions.
PROCEDURES
Seven radiographic projections (ventrodorsal, dorsoventral, lateral, and 4 oblique views) were obtained for each cadaver. A necropsy was then performed, and each bone of the pectoral girdle (coracoid, clavicle, and scapula) was evaluated for fractures. Radiographs were evaluated in a randomized order by a blinded observer, and results were compared with results of necropsy.
RESULTS
Fifty-six of the 103 (54%) cadavers had ≥ 1 pectoral girdle fracture. Overall accuracy of using individual radiographic projections to diagnose pectoral girdle fractures ranged from 63.1% to 72.8%, sensitivity ranged from 21.3% to 51.1%, and specificity ranged from 85.7% to 100.0%. The sensitivity of using various combinations of radiographic projections to diagnose pectoral girdle fractures ranged from 51.1% to 66.0%; specificity ranged from 76.8% to 96.4%.
CLINICAL RELEVANCE
Radiography alone appeared to have limited accuracy for diagnosing fractures of the bones of the pectoral girdle in wild passerines after collision with a window. Both individual radiographic projections and combinations of projections resulted in numerous false negative but few false positive results.
Topics: Animals; Fractures, Bone; Passeriformes; Radiography; Scapula
PubMed: 34986113
DOI: 10.2460/javma.20.11.0642 -
PeerJ 2021The megalichthyids are one of several clades of extinct tetrapodomorph fish that lived throughout the Devonian-Permian periods. They are advanced "osteolepidid-grade"...
BACKGROUND
The megalichthyids are one of several clades of extinct tetrapodomorph fish that lived throughout the Devonian-Permian periods. They are advanced "osteolepidid-grade" fishes that lived in freshwater swamp and lake environments, with some taxa growing to very large sizes. They bear cosmine-covered bones and a large premaxillary tusk that lies lingually to a row of small teeth. Diagnosis of the family remains controversial with various authors revising it several times in recent works. There are fewer than 10 genera known globally, and only one member definitively identified from Gondwana. Fox et al. 1995 was described from the Lower Carboniferous Raymond Formation in Queensland, Australia, on the basis of several well-preserved specimens. Despite this detailed work, several aspects of its anatomy remain undescribed.
METHODS
Two especially well-preserved 3D fossils of , including the holotype specimen, are scanned using synchrotron or micro-computed tomography (µCT), and 3D modelled using specialist segmentation and visualisation software. New anatomical detail, in particular internal anatomy, is revealed for the first time in this taxon. A novel phylogenetic matrix, adapted from other recent work on tetrapodomorphs, is used to clarify the interrelationships of the megalichthyids and confirm the phylogenetic position of .
RESULTS
Never before seen morphological details of the palate, hyoid arch, basibranchial skeleton, pectoral girdle and axial skeleton are revealed and described. Several additional features are confirmed or updated from the original description. Moreover, the first full, virtual cranial endocast of any tetrapodomorph fish is presented and described, giving insight into the early neural adaptations in this group. Phylogenetic analysis confirms the monophyly of the Megalichthyidae with seven genera included ( and ). The position of the megalichthyids as sister group to canowindrids, crownward of "osteolepidids" (e.g., and ), but below "tristichopterids" such as is confirmed, but our findings suggest further work is required to resolve megalichthyid interrelationships.
PubMed: 34966593
DOI: 10.7717/peerj.12597