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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 -
Journal of Morphology Nov 2004The pectoral fins of Acipenseriformes possess endoskeletons with elements homologous to both the fin radials of teleosts and the limb bones of tetrapods. Here we present...
The pectoral fins of Acipenseriformes possess endoskeletons with elements homologous to both the fin radials of teleosts and the limb bones of tetrapods. Here we present a study of pectoral fin development in the North American paddlefish, Polyodon spathula, and the white sturgeon, Acipenser transmontanus, which reveals that aspects of both teleost and tetrapod endoskeletal patterning mechanisms are present in Acipenseriformes. Those elements considered homologous to teleost radials, the propterygium and the mesopterygial radials, form via subdivision of an initially chondrogenic plate of mesenchymal cells called the endoskeletal disc. In Acipenseriformes, elements homologous to the sarcopterygian metapterygium develop separately from the endoskeletal disc as an outgrowth of the endoskeletal shoulder girdle that extends into the posterior margin of the finbud. As in tetrapods, the elongating metapterygium and the metapterygial radials form in a proximal to distal order as discrete condensations from initially nonchondrogenic mesenchyme. Patterns of variation seen in the Acipenseriform fin also correlate with putative homology: all variants from the "normal" fin bauplan involved the metapterygium and the metapterygial radials alone. The primary factor distinguishing Polyodon and Acipenser fin development from each other is the composition of the endoskeletal extracellular matrix. Proteoglycans (visualized with Alcian Blue) and Type II collagen (visualized by immunohistochemistry) are secreted in different places within the mesenchymal anlage of the fin elements and girdle and at different developmental times. Acipenseriform pectoral fins differ from the fins of teleosts in the relative contribution of the endoskeleton and dermal rays. The fins of Polyodon and Acipenser possess elaborate endoskeletons overlapped along their distal margins by dermal lepidotrichia. In contrast, teleost fins generally possess relatively small endoskeletal radials that articulate with the dermal fin skeleton terminally, with little or no proximodistal overlap.
Topics: Animals; Chondrogenesis; Collagen; Extremities; Fishes; Gene Expression Regulation, Developmental
PubMed: 15376275
DOI: 10.1002/jmor.10264 -
Journal of Anatomy Dec 2020There is a functional trade-off in the design of skeletal muscle. Muscle strength depends on the number of muscle fibers in parallel, while shortening velocity and...
Monitoring muscle over three orders of magnitude: Widespread positive allometry among locomotor and body support musculature in the pectoral girdle of varanid lizards (Varanidae).
There is a functional trade-off in the design of skeletal muscle. Muscle strength depends on the number of muscle fibers in parallel, while shortening velocity and operational distance depend on fascicle length, leading to a trade-off between the maximum force a muscle can produce and its ability to change length and contract rapidly. This trade-off becomes even more pronounced as animals increase in size because muscle strength scales with area (length ) while body mass scales with volume (length ). In order to understand this muscle trade-off and how animals deal with the biomechanical consequences of size, we investigated muscle properties in the pectoral girdle of varanid lizards. Varanids are an ideal group to study the scaling of muscle properties because they retain similar body proportions and posture across five orders of magnitude in body mass and are highly active, terrestrially adapted reptiles. We measured muscle mass, physiological cross-sectional area, fascicle length, proximal and distal tendon lengths, and proximal and distal moment arms for 27 pectoral girdle muscles in 13 individuals across 8 species ranging from 64 g to 40 kg. Standard and phylogenetically informed reduced major axis regression was used to investigate how muscle architecture properties scale with body size. Allometric growth was widespread for muscle mass (scaling exponent >1), physiological cross-sectional area (scaling exponent >0.66), but not tendon length (scaling exponent >0.33). Positive allometry for muscle mass was universal among muscles responsible for translating the trunk forward and flexing the elbow, and nearly universal among humeral protractors and wrist flexors. Positive allometry for PCSA was also common among trunk translators and humeral protractors, though less so than muscle mass. Positive scaling for fascicle length was not widespread, but common among humeral protractors. A higher proportion of pectoral girdle muscles scaled with positive allometry than our previous work showed for the pelvic girdle, suggesting that the center of mass may move cranially with body size in varanids, or that the pectoral girdle may assume a more dominant role in locomotion in larger species. Scaling exponents for physiological cross-sectional area among muscles primarily associated with propulsion or with a dual role were generally higher than those associated primarily with support against gravity, suggesting that locomotor demands have at least an equal influence on muscle architecture as body support. Overall, these results suggest that larger varanids compensate for the increased biomechanical demands of locomotion and body support at higher body sizes by developing larger pectoral muscles with higher physiological cross-sectional areas. The isometric scaling rates for fascicle length among locomotion-oriented pectoral girdle muscles suggest that larger varanids may be forced to use shorter stride lengths, but this problem may be circumvented by increases in limb excursion afforded by the sliding coracosternal joint.
Topics: Animals; Biomechanical Phenomena; Body Size; Gait; Lizards; Locomotion; Muscle Strength; Muscle, Skeletal
PubMed: 32710503
DOI: 10.1111/joa.13273 -
Journal of Morphology Jun 2023Penguins (Aves, Sphenisciformes) are pursuit divers that feed mainly on krill, fish, and squid. Although they are opportunistic feeders, some species are more...
Penguins (Aves, Sphenisciformes) are pursuit divers that feed mainly on krill, fish, and squid. Although they are opportunistic feeders, some species are more generalists than others and many show dietary preferences toward krill and other crustaceans or fish and squid. Their diving depth seems to follow a body size pattern and relates to the type of item that they prey on. Penguins dive with their wing; hence their wing musculature is responsible for the animal maneuverability and strength while diving. In the present study, ecological traits such as diving depths and prey composition are used to explore if morphology relates to foraging habits. A geometric morphometric approach is used to quantitatively address these morphological differences in the wing apparatus of all extant penguins and a fossil species taking into consideration allometric and phylogenetic factors. Results show that morphological differences among penguins with different diets are significant and strong; groups are well separated with the greatest differences found between piscivorous and crustacivorous penguins. Dive depth has a moderate covariation with morphology and a strong correspondence with wing area. Last, Madrynornis mirandus, an exceptionally well-preserved fossil from the Miocene of Patagonia, is found to be close to the piscivorous and generalist piscivorous species. It is proposed that swimming styles correlate with specific traits of the anatomy of wing and pectoral girdle skeleton and muscles.
Topics: Animals; Spheniscidae; Phylogeny; Diving; Swimming; Wings, Animal
PubMed: 37183492
DOI: 10.1002/jmor.21588 -
Developmental Biology Sep 2011The forelimbs of higher vertebrates are composed of two portions: the appendicular region (stylopod, zeugopod and autopod) and the less prominent proximal girdle...
The forelimbs of higher vertebrates are composed of two portions: the appendicular region (stylopod, zeugopod and autopod) and the less prominent proximal girdle elements (scapula and clavicle) that brace the limb to the main trunk axis. We show that the formation of the muscles of the proximal limb occurs through two distinct mechanisms. The more superficial girdle muscles (pectoral and latissimus dorsi) develop by the "In-Out" mechanism whereby migration of myogenic cells from the somites into the limb bud is followed by their extension from the proximal limb bud out onto the thorax. In contrast, the deeper girdle muscles (e.g. rhomboideus profundus and serratus anterior) are induced by the forelimb field which promotes myotomal extension directly from the somites. Tbx5 inactivation demonstrated its requirement for the development of all forelimb elements which include the skeletal elements, proximal and distal muscles as well as the sternum in mammals and the cleithrum of fish. Intriguingly, the formation of the diaphragm musculature is also dependent on the Tbx5 programme. These observations challenge our classical views of the boundary between limb and trunk tissues. We suggest that significant structures located in the body should be considered as components of the forelimb.
Topics: Animals; Body Patterning; Chick Embryo; Embryo, Mammalian; Forelimb; Mice; Muscle, Skeletal; Somites; T-Box Domain Proteins; Zebrafish
PubMed: 21741963
DOI: 10.1016/j.ydbio.2011.06.031 -
Journal of Anatomy Jul 2006Using cleared-and-stained whole mounts and computer-aided three-dimensional reconstructions made from serial histological sections, we studied the development of the...
Using cleared-and-stained whole mounts and computer-aided three-dimensional reconstructions made from serial histological sections, we studied the development of the pectoral girdle in Discoglossus pictus, an extant member of an ancient frog lineage, represented for example by Eodiscoglossus from the Middle Jurassic to Early Cretaceous periods in Europe. Basic developmental features were compared with those of extinct Temnospondyli, considered to be the most probable anuran ancestors, and with Triadobatrachus, an early Triassic proanuran. In the endochondral girdle, the separate scapula and coracoid of Discoglossus and other anurans (completed by suprascapular and procoracoid cartilages) evolved from the compact scapulocoracoid of temnospondyls by paedomorphosis. In parallel, the dermal ossifications of the girdle were reduced to a small clavicle and cleithrum. The overall reduction in ossification of the anuran pectoral girdle supports the hypothesis of a paedomorphic origin for Anura. The almost simultaneous appearance of dermal and endochondral ossifications may be explained by the accumulation of developmental events during a short, distinct metamorphosis (which did not occur in neotenic temnospondyls living permanently in water). The sternal elements seem to be neomorphs for the most part, which help to cushion the shock of landing in jumping anurans but which also evolved as functional substitutes (insertion area for the pectoralis muscles) of the temnospondyl interclavicle.
Topics: Animals; Anura; Biological Evolution; Bone Development; Clavicle; Fossils; Imaging, Three-Dimensional; Metamorphosis, Biological; Scapula; Shoulder Joint
PubMed: 16822264
DOI: 10.1111/j.1469-7580.2006.00583.x -
American Journal of Human Biology : the... Sep 2016This study investigates growth patterns in the scapula and clavicle in a cross-sectional juvenile skeletal sample ranging from 20 weeks gestation to 8.5 years of age...
OBJECTIVES
This study investigates growth patterns in the scapula and clavicle in a cross-sectional juvenile skeletal sample ranging from 20 weeks gestation to 8.5 years of age from the Kellis 2 cemetery, Dakhleh Oasis, Egypt. The primary goal is to quantify growth patterns and growth velocities in the scapula and clavicle to better understand the development of the pectoral girdle.
METHODS
A series of low-order polynomial regression models was used to examine growth curves in clavicle diaphyseal length, scapular height, and scapular width. Incremental growth and relative percent increase were examined among successive age groups as a proxy measure of growth velocity. Scapular body proportions were assessed with the scapular index and compared across age groups using a Kruskal-Wallis test with post-hoc tests.
RESULTS
A third-order polynomial best describes growth in clavicle diaphyseal length and scapular height, and a second-order polynomial best describes growth in scapular width. Growth velocity patterns are similar among clavicle diaphyseal length, scapular height, and scapular width particularly from birth until the end of early childhood. Clavicle diaphyseal length decelerates during middle childhood while scapular height and width accelerate during this time. With increasing age, the scapular body proportionately increases more in height than in width. The relatively narrow scapular body characteristic of adult scapulae is first evident during early childhood.
CONCLUSIONS
Changes in scapular body shape during ontogeny may be a reflection of the greater alterations taking place in the integrated morphology of the pectoral girdle during the biomechanical shift from crawling to bipedalism. Am. J. Hum. Biol. 28:636-645, 2016. © 2016 Wiley Periodicals, Inc.
Topics: Cemeteries; Child; Child, Preschool; Clavicle; Egypt; Fetus; History, Ancient; Humans; Infant; Infant, Newborn; Scapula; Shoulder
PubMed: 26914741
DOI: 10.1002/ajhb.22844 -
Scientific Reports Jul 2021The furcula is a distinctive element of the pectoral skeleton in birds, which strengthens the shoulder region to withstand the rigor of flight. Although its origin among...
The furcula is a distinctive element of the pectoral skeleton in birds, which strengthens the shoulder region to withstand the rigor of flight. Although its origin among theropod dinosaurs is now well-supported, the homology of the furcula relative to the elements of the tetrapod pectoral girdle (i.e., interclavicle vs clavicles) remains controversial. Here, we report the identification of the furcula in the birdlike theropod Halszkaraptor escuilliei. The bone is unique among furculae in non-avian dinosaurs in bearing a visceral articular facet in the hypocleideal end firmly joined to and overlapped by the sternal plates, a topographical pattern that supports the primary homology of the furcula with the interclavicle. The transformation of the interclavicle into the furcula in early theropods is correlated to the loss of the clavicles, and reinforced the interconnection between the contralateral scapulocoracoids, while relaxing the bridge between the scapulocoracoids with the sternum. The function of the forelimbs in theropod ancestors shifted from being a component of the locomotory quadrupedal module to an independent module specialized to grasping. The later evolution of novel locomotory modules among maniraptoran theropods, involving the forelimbs, drove the re-acquisition of a tighter connection between the scapulocoracoids and the interclavicle with the sternal complex.
PubMed: 34282248
DOI: 10.1038/s41598-021-94285-3 -
Journal of Anatomy Jan 2013Muscles of the vertebrate neck include the cucullaris and hypobranchials. Although a functional neck first evolved in the lobe-finned fishes (Sarcopterygii) with the... (Review)
Review
Muscles of the vertebrate neck include the cucullaris and hypobranchials. Although a functional neck first evolved in the lobe-finned fishes (Sarcopterygii) with the separation of the pectoral/shoulder girdle from the skull, the neck muscles themselves have a much earlier origin among the vertebrates. For example, lampreys possess hypobranchial muscles, and may also possess the cucullaris. Recent research in chick has established that these two muscles groups have different origins, the hypobranchial muscles having a somitic origin but the cucullaris muscle deriving from anterior lateral plate mesoderm associated with somites 1-3. Additionally, the cucullaris utilizes genetic pathways more similar to the head than the trunk musculature. Although the latter results are from experiments in the chick, cucullaris homologues occur in a variety of more basal vertebrates such as the sharks and zebrafish. Data are urgently needed from these taxa to determine whether the cucullaris in these groups also derives from lateral plate mesoderm or from the anterior somites, and whether the former or the latter represent the basal vertebrate condition. Other lateral plate mesoderm derivatives include the appendicular skeleton (fins, limbs and supporting girdles). If the cucullaris is a definitive lateral plate-derived structure it may have evolved in conjunction with the shoulder/limb skeleton in vertebrates and thereby provided a greater degree of flexibility to the heads of predatory vertebrates.
Topics: Animals; Biological Evolution; Gene Expression Regulation; Muscle Development; Neck Muscles; Vertebrates
PubMed: 22697305
DOI: 10.1111/j.1469-7580.2012.01530.x