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The axial skeleton of orange rumped agouti, Dasyprocta leporina, was studied for better understanding of its locomotor behaviour. The bones from eight adult agoutis of both sexes were observed for their anatomical features and functional significance. The vertebral formula was found to be C7 T12 L7 S5 Cy5-6 . The well-developed occipital crest, caudally oriented prominent axis spine and well-developed transverse processes from C3 -C7 indicated a highly flexible neck with greater sagittal mobility. Articular facets were horizontal in anterior series while oblique in the posterior series, which enabled them to perform both lateral and sagittal movements during locomotion. The caudally directed thoracic spines, T12 as anticlinal vertebra and prominent mamillary process in the posterior series were suggestive of strong dorso-ventral flexion/extension and rotation. The robust lumbar vertebrae, well-developed transverse processes with cranio-ventral extension, were the feature for powerful sagittal/dorsoventral movement. The presence of spinous processes and well-developed transverse processes in all caudal vertebrae was an indication of a highly movable tail. The ribs were 13 pairs with first seven as sternal and six as asternal. They were laterally compressed in the anterior series as a cursorial adaptation. A strong muscular attachment to vertebrae provides this rodent speed, agility, dexterity and strength suitable for survival in food chain.

A critical stage in the development of all vertebrate embryos is the generation of the body plan and its subsequent patterning and regionalisation along the main anterior-posterior axis. This includes the formation of the vertebral axial skeleton. Its organisation begins during early embryonic development with the periodic formation of paired blocks of mesoderm tissue called somites. Here, we review axial patterning of somites, with a focus on studies using amniote model systems – avian and mouse. We summarise the molecular and cellular mechanisms that generate paraxial mesoderm and review how the different anatomical regions of the vertebral column acquire their specific identity and thus shape the body plan. We also discuss the generation of organoids and embryo-like structures from embryonic stem cells, which provide insights regarding axis formation and promise to be useful for disease modelling.

Extreme body elongation has occurred repeatedly in the evolutionary history of ray-finned fishes. Lengthening of the anterior-posterior body axis relative to depth and width can involve changes in the cranial skeleton and vertebral column, but to what extent is anatomical evolution determined by selective factors and intrinsic constraints that are shared broadly among closely related lineages? In this study, we fit adaptive (Ornstein-Uhlenbeck) evolutionary models to body shape and its anatomical determinants and identified two instances of extreme elongation by divergent anatomical peak shifts in the Blenniiformes, a radiation of small-bodied substrate-associated marine teleost fishes. Species in the genus Xiphasia (hairtail blennies) evolved toward a peak defined by a highly elongated caudal vertebral region but ancestral cranial and precaudal vertebral morphology. In contrast, a clade that includes the genera Chaenopsis and Lucayablennius (pike and arrow blennies) evolved toward a peak with a long slender skull but ancestral axial skeletal anatomy. Neither set of anatomical peak shifts aligns closely with the major axis of anatomical diversification in other blenniiform fishes. These results provide little evidence that ancestral constraints have affected body shape transformation, and instead suggest that extreme elongation arose with distinct shifts in selective factors and development.

Mammaliamorpha comprises the last common ancestor of Tritylodontidae and Mammalia plus all its descendants1. Tritylodontids are nonmammaliaform herbivorous cynodonts that originated in the Late Triassic epoch, diversified in the Jurassic period2–5 and survived into the Early Cretaceous epoch6,7. Eutriconodontans have generally been considered to be an extinct mammalian group, although different views exist8. Here we report a newly discovered tritylodontid and eutriconodontan from the Early Cretaceous Jehol Biota of China. Eutriconodontans are common in this biota9, but it was not previously known to contain tritylodontids. The two distantly related species show convergent features that are adapted for fossorial life, and are the first ‘scratch-diggers’ known from this biota. Both species also show an increased number of presacral vertebrae, relative to the ancestral state in synapsids or mammals10,11, that display meristic and homeotic changes. These fossils shed light on the evolutionary development of the axial skeleton in mammaliamorphs, which has been the focus of numerous studies in vertebrate evolution12–17 and developmental biology18–28. The phenotypes recorded by these fossils indicate that developmental plasticity in somitogenesis and HOX gene expression in the axial skeleton—similar to that observed in extant mammals—was already in place in stem mammaliamorphs. The interaction of these developmental mechanisms with natural selection may have underpinned the diverse phenotypes of body plan that evolved independently in various clades of mammaliamorph. Fossiomanus sinensis and Jueconodon cheni, a newly described Early Cretaceous tritylodontid and eutriconodotan, respectively, show convergence on a fossorial body plan and provide insights into the evolution of the axial skeleton in mammaliamorphs.

To date, 40 cases of placental teratoma and 21 cases of umbilical cord teratoma have been reported in the literature. Such entities are purportedly described as originating from ectopically derived totipotential germ cells forming 1 or more of 3 germ layers, similar to teratomas arising in other sites. These entities have been described as distinct from acardiac twins based on the absence of both an axial skeleton and/or separate umbilical cord attachment. We present a case that would be compatible with placental teratoma according to these criteria. However, DNA genotyping analysis of the "teratoma" and its corresponding normal placental tissue revealed an identical genetic profile at all microsatellite polymorphic loci with exception of one locus demonstrating loss of heterozygosity involving 1 of 2 "teratoma" samples tested. Our finding established that the "teratoma" in fact represented a monozygotic acardiac (amorphous) twin with aberrant division of embryogenesis as a continuum of the monozygotic twinning phenomenon. In summary, this is the first case study of so-called placental teratoma by DNA genotyping investigation. We conclude that the diagnostic term "placental teratoma" should be discouraged unless evidence of monozygotic twining can be ruled out by molecular genotyping.

The postcranial axial skeleton of actinopterygian fishes is typically divided into three regions: (1) an anterior abdominal region, (2) a posterior caudal region and (3) those vertebrae supporting the caudal fin. However, in some actinopterygians, the axial skeleton is more finely subdivided, with up to six morphologically distinctsub-regions recognized. Phylogenetic continuity and homology of structures across these sub-regions have not been investigated in detail, either between or among groups. We examine variation in axial regionalization in saurichthyid fishes, a clade of extinct non-teleostean actinopterygians with highly variable axial skeletal morphology but an otherwise conservative body plan, and compare these findings to other non-teleostean actinopterygians to assess conservation of a regionalized axial skeleton within bony fishes. We document up to eight distinct regions in the vertebral column of Triassic Saurichthys: (1) a postoccipital region, (2) an anterior and (3) a posterior abdominal region, (4) a transitional region spanning the abdominal– caudal boundary, (5) an anterior and (6) a posterior caudal region and (7) preural and (8) ural regions. Based on taphonomical and morphological evidence, the transitional region appears to function in axial stiffening in the area of the median fins, whereas the abdominal region is highly flexible. The degree to which these axial regions are osteologically differentiated is highly variable across Saurichthyidae, implying iterative evolution of differentiation and de-differentiation over relatively short geological timescales. Such variably expressed regionalization was also identified in the outgroup non-teleostean actinopterygians Birgeria and Australosomus. Despite variation in morphological disparity, the regions identified in saurichthyids correlate well with those documented in some teleosts and Paleozoic actinopterygians, suggesting potential deep patterning homology but independent evolution of specific regionalized axial morphologies in response to changing functional demands.

Background The process of calcium carbonate biomineralization has arisen multiple times during metazoan evolution. In the phylum Cnidaria, biomineralization has mostly been studied in the subclass Hexacorallia (i.e. stony corals) in comparison to the subclass Octocorallia (i.e. red corals); the two diverged approximately 600 million years ago. The precious Mediterranean red coral, Corallium rubrum, is an octocorallian species, which produces two distinct high-magnesium calcite biominerals, the axial skeleton and the sclerites. In order to gain insight into the red coral biomineralization process and cnidarian biomineralization evolution, we studied the protein repertoire forming the organic matrix (OM) of its two biominerals. Results We combined High-Resolution Mass Spectrometry and transcriptome analysis to study the OM composition of the axial skeleton and the sclerites. We identified a total of 102 OM proteins, 52 are found in the two red coral biominerals with scleritin being the most abundant protein in each fraction. Contrary to reef building corals, the red coral organic matrix possesses a large number of collagen-like proteins. Agrin-like glycoproteins and proteins with sugar-binding domains are also predominant. Twenty-seven and 23 proteins were uniquely assigned to the axial skeleton and the sclerites, respectively. The inferred regulatory function of these OM proteins suggests that the difference between the two biominerals is due to the modeling of the matrix network, rather than the presence of specific structural components. At least one OM component could have been horizontally transferred from prokaryotes early during Octocorallia evolution. Conclusion Our results suggest that calcification of the red coral axial skeleton likely represents a secondary calcification of an ancestral gorgonian horny axis. In addition, the comparison with stony coral skeletomes highlighted the low proportion of similar proteins between the biomineral OMs of hexacorallian and octocorallian corals, suggesting an independent acquisition of calcification in anthozoans.

Somitogenesis is the process by means of which a tissue known as presomitic mesoderm (PSM) is segmented in blocks of cells, called somites, along the anterior-posterior axis of the developing embryo in segmented animals. In vertebrates, somites give rise to axial skeleton, cartilage, tendons, skeletal muscle, and dermis. Somite formation occurs periodically, and this periodicity is driven by a genetic oscillator that operates within PSM cells and is known as the segmentation clock. The correct synchronization of the segmentation clock among PSM cells is essential for somitogenesis to develop normally. When synchronization is disrupted, somites form irregularly and, in consequence, the tissues that originate from them show clear malformations. In this work, based in a model for zebrafish segmentation clock, we investigate by means of a mathematical modeling approach, how PSM-cell synchronization is affected by factors like: the size of PSM-cell networks, the amount of cell-to-cell interactions per PSM cell, the strength of these interactions, and the inherent variability among PSM cells. Interestingly we found that very small PSM-cell networks are unable to synchronize. Moreover, the effect of decreasing the strength of interactions among PSM cells is corrected by increasing the network connectivity-level, and a moderated level of variability among cells can have a positive effect on synchronization, specially in large networks.

El género Spalacopus incluye una sola especie, S. cyanus, endémica de la región central del Chile, siendo una de las especies mejor adaptada a la vida subterránea de la familia Octodontidae. Miembro del linaje que consiste en Octodontomys como hermano de Octodon y el clado representado por Spalacopus y Aconaemys. Si bien la morfología externa y cráneo-dentarias en S. cyanus han sido bien estudiadas, su morfología postcraneal es pobremente conocida. Por las peculiaridades de su estilo de vida y locomoción entre los miembros de la familia, es interesante caracterizar detalles de la morfología del esqueleto postcraneal de esta especie e inferir sus aspectos funcionales de la morfología. Se revisaron 29 ejemplares con material de postcráneo disponibles en dos colecciones sistemáticas: Museo de La Plata (MLP), La Plata, Buenos Aires, Argentina y Colección de Mamíferos del Instituto de Ciencias Ambientales y Evolutivas (UACH), Universidad Austral de Chile, Valdivia, Chile. Para la descripción detallada de la morfología de los elementos óseos se dividió al esqueleto en las siguientes regiones: esqueleto axial, cintura escapular y miembros anteriores, y cintura pélvica y miembros posteriores. Las estructuras incluidas en el esqueleto axial fueron descriptas principalmente en sentido cráneo-caudal y en los miembros en sentido próximo-distal. La observación de las estructuras se realizó con las lupas estereoscópicas Leica Wild M3Z y Nikon SMZ 745T, incluyendo fotografías para ilustrar las descripciones. En la morfología postcraneal de S. cyanus se observan características que se consideran altamente conservadas entre los miembros de la familia Octodontidae, pero algunos caracteres son exclusivos de la especie. El esqueleto axial está compuesto por siete vértebras cervicales, 12 ó 13 torácicas, seis o siete lumbares, cuatro sacras, entre 16 y 18 caudales, 12 ó 13 pares de costillas y un esternón compuesto por cinco esternebras. Los elementos óseos de las cinturas pectoral y pélvica como de los miembros anterior y posterior se describen en detalle, excepto los carpos y tarsos debido al mal estado de preservación o ausencia de los mismos. El patrón morfológico que presenta el postcráneo de S. cyanus se ajusta a un plan anatómico típico de especies terrestres y en algunos elementos óseos (húmero y ulna principalmente) se observan características típicamente asociadas con la habilidad excavadora. Los datos generados permitirán a futuro una mejor interpretación de los atributos postcraneales funcionalmente relacionados con los diferentes estilos de vida, evaluar sus estrategias locomotoras, así como también comprender la evolución de estos rasgos en un contexto filogenético. The genus Spalacopus includes only one species, S. cyanus, endemic to central Chile and one of the species best adapted to a subterranean lifetyle in the family Octodontidae. It is a member of the lineage consisting in Octodontomys as a sister clade containing Octodon and of a clade represented by Spalacopus and Aconaemys. Although the external and cranio-dental morphology have been well studied, little is known of the postcranial morphology of S. cyanus. Because of the peculiarities of its lifestyle and locomotion among the members of the family, it is interesting to characterize details of the morphology of the postcranial skeleton of this species and to infer their functional aspects of the morphology. Twenty-nine specimens with postcranial material stored in two collections were studied: Museo de La Plata (MLP), La Plata, Buenos Aires, Argentina and Colección de Mamíferos del Instituto de Ciencias Ambientales y Evolutivas (UACH), Universidad Austral de Chile, Valdivia, Chile. To describe in detail the morphology of the bone elements, the skeleton was divided in the following regions: axial skeleton, scapular girdle and forelimb, and pelvis girdle and hindlimb. The structures included in the axial skeleton were mainly described in cranial-caudal orientation and the limbs in proximal-distal orientation. All structures were observed with stereoscopic microscopes Leica Wild M3Z and Nikon SMZ 745T including pictures to illustrate the descriptions. Highly conservative characteristics among members of the family Octodontidae were observed in the postcranial morphology of S. cyanus, although some characters are exclusive to this species. The axial skeleton has seven cervical vertebrae, 12 or 13 thoracic, six or seven lumbar, four sacral, 16 to 18 caudal vertebrae, 12 or 13 ribs and a sternum with five sternebrae. The elements of the scapular and pelvic girdles as well as forelimbs and hindlimbs are described in detail, except the carpus and tarsus due to their poor state of conservation, or because they not available. The morphological pattern observed in the postcranial skeleton of S. cyanus conforms to a typical anatomical plan for terrestrial species, and some bones (mainly humerus and ulna) present characteristics associated with digging. The information obtained provided will allow a better interpretation of the postcranial attributes, functionally related with different lifestyle, in a future, as well as the evolution of the traits in a phylogenetic context. Fil: Pérez, María Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Investigación de Biodiversidad Argentina; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Conservación de los Murciélagos de Argentina; Argentina Fil: Díaz, María Mónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Investigación de Biodiversidad Argentina; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo. Programa de Conservación de los Murciélagos de Argentina; Argentina. Fundación Miguel Lillo; Argentina

A new species Melanostigma lazarevi sp. n. is described from the D’Urville Sea (Southern Ocean). This species differs from the other species of the genus Melanostigma in an original combination of the characters, particular, in the structure of the lateral line system on the head (interruption in supratemporal commissure with the loss of medial segments, absence of pores and the presence of two (instead one) segments in the temporal canal), coloration and some meristic characters of the axial skeleton.

The age-related carcass-morphology and composition changes and the growth and development patterns of the axial and peripheral skeleton systems and the bones composing them in the Simmental and crossbred young beef bulls have been studied. In order to carry out the survey, the young bulls were divided into three groups of 15 animals each. The first (control) group included the purebred Simmental young bulls. The second (experimental) group was formed of the halfbred and crossbred young stock produced by crossbreeding between the Simmental cows and the Simmental beef bulls of German selection. The third (experimental) group was composed of the crosses of Simmental cows with Charolais bulls. The Charolais crosses had more energy for growth. Thus, their liveweights comprised 431.9, 523.4, and 620.6 kg at the ages of 12, 15, and 18 months, respectively, which were 7.8, 7.5, and 10.2% more than that in their peers of the maternal breed. The crossbred young stock in both groups was distinct for carcass morphology and composition, reaching a more advanced level of the carcass flesh-coverage mass in all the age intervals when compared that to the purebred Simmentals. The age-related changes in the absolute and relative masses of the young-bull carcass bones are caused by different intensities specific to bone growth in the axial and peripheral skeleton systems. For instance, the intensity of bone growth in the axial skeleton system tended to increase in the postnatal period, while the bone growth rates of the peripheral skeleton system decreased. Irregularity in developing the indicated skeleton systems is caused by different intensities specific to growth of certain bones and their complexes. The highest growth rate is usually typical for ribs and the vertebral column, while the slowest growth rate is most common for extremitas thoracica and extremas pelvina. The bone growth rates for the limb proximal structures generally exceed that for the distal bone structures. The age-related differences in the growth rates of certain skeleton structures can cause some changes in ratios between the linear body measurements of the young bulls.

The larval development of Chirolophis japonicus and Ch. saitone from the yolk-sac stage to the settlement on the bottom is described from waters of Peter the Great Bay, Sea of Japan. The pattern of distribution of melanin pigmentation over the body of larvae in these Chirolophis species is formalized for the first time. It consists of six rows, the aggregation on the top of head, and several single melanophores. Despite the similarity between the species, each of them has its specific features that are manifested mainly as a different number of axial skeleton elements (total number of vertebrae and number of rays in the dorsal and anal fins). A conclusion is made that a reliable diagnostic character to identify larvae of Ch. japonicus and Ch. saitone within the period of their development from hatching to settlement can be the number of melanophores at the base of the anal fin rays.

Serial homology or the repetition of equivalent developmental units and their derivatives is a phenomenon encountered in a variety of organisms, with the vertebrate axial skeleton as one of the most notable examples. Serially homologous structures can be viewed as an appropriate model system for studying morphological integration and modularity, due to the strong impact of development on their covariation. Here, we explored the pattern of morphological integration of the cranium and the first three serially homologous structures (atlas, first, and second trunk vertebrae) in salamandrid salamanders, using micro‐CT scanning and three‐dimensional geometric morphometrics. We explored the integration between structures at static and evolutionary levels. Effects of allometry on patterns of modularity were also taken into account. At the static level (within species), we analyzed inter‐individual variation in shape to detect functional modules and intra‐individual variation to detect developmental modules. Significant integration (based on inter‐individual variation) among all structures was detected and allometry is shown to be an important integrating factor. The pattern of intra‐individual, asymmetric variation indicates statistically significant developmental integration between the cranium and the atlas and between the first two trunk vertebrae. At the evolutionary level (among species), the cranium, atlas, and trunk vertebrae separate as different modules. Our results show that morphological integration at the evolutionary level coincides with morphological and functional differentiation of the axial skeleton, allowing the more or less independent evolutionary changes of the cranial skeleton and the vertebral column, regardless of the relatively strong integration at the static level. The observed patterns of morphological integration differ across levels, indicating different impacts of developmental and phylogenetic constraints and functional demands.

The evolution of semi-independent modules is hypothesized to underlie the functional diversification of serially repeating (metameric) structures. The mammal vertebral column is a classic example of a metameric structure that is both modular, with well-defined morphological regions, and functionally differentiated. How the evolution of regions is related to their functional differentiation in the forerunners of mammals remains unclear. Here we gathered morphometric and biomechanical data on the presacral vertebrae of two extant species that bracket the synapsid–mammal transition and use the relationship between form and function to predict functional differentiation in extinct non-mammalian synapsids. The origin of vertebral functional diversity does not correlate with the evolution of new regions but appears late in synapsid evolution. This decoupling of regions from functional diversity implies that an adaptive trigger is needed to exploit existing modularity. We propose that the release of axial respiratory constraints, combined with selection for novel mammalian behaviours in Late Triassic cynodonts, drove the functional divergence of pre-existing morphological regions. Applying vertebral form–function relationships derived from extant animals to the synapsid fossil record indicates evolution of vertebral regions is decoupled from their functional exploitation.

The osteological description of the ocular head region and the pectoral girdle (using alizarin-stained preparations) of Ipnops agassizii Garman, 1899 (family Ipnopidae) was made based on material collected from bathyal and ultra-abyssal depths (3020–5410 m). A detailed description of the axial skeleton is provided and features of the fin skeleton are analyzed (using X-ray images). The morphological transformations in the skeleton that occurred as a result of living at great depths are considered. The wide range of functional and morphological specializations, which have an adaptive pattern aimed at adaptation to deep-sea habitats in contact with the bottom, are shown. The fin rays of the unpaired fins and their supporting elements (respectively, interneuralia and interhaemalia) have reinforced bony heads. The pelvic fins are located at the vertical line through the tips of the pectoral fin rays, slightly anteriorly of the mid-body level. The dorsal fin is located far anteriorly of the anal fin. The caudal peduncle is equally flattened both laterally and dorsoventrally.

Extinct sloths (Xenarthra, Folivora) are morphologically diverse, despite some similarities among some Pleistocene genera. Cranial and diagnostic postcranial elements (especially limb bones) are ta...

The Lower Jurassic Lufeng Formation in Yunnan Province of southwestern China provides one of the most abundant records of sauropodomorphs in the world. However, most of them have not been fully described. Xingxiulong chengi is among the most complete non-sauropodan sauropodomorphs ever discovered from Lufeng Formation and is represented by three partial skeletons. Here, we provide a detailed osteological description of its axial skeleton, including both the cranial and postcranial elements, and compare its anatomy with that of other known non-sauropodan sauropodomorphs. In general, the cranium of Xingxiulong is more similar to those of more basal sauropodomorphs than to sauropodiforms, as evidenced by features such as an only slightly concave dorsal margin of the postorbital, a caudally placed rostral margin of the infratemporal fenestra not extending below the orbit, and long and slender basipterygoid processes divergent from each other at an angle of approximately 80 degrees. However, its postcranial axial skeleton possesses some unique or relatively derived features among basal sauropodomorphs, such as four sacral vertebrae and caudal dorsal vertebrae with laterally expanded neural spine tables. This provides future workers with a reassessment of non-sauropodan sauropodomorphs through the lens of Xingxiulong chengi, which will serve to increase our knowledge on the anatomy, phylogeny, and furthermore, evolution of sauropodomorph dinosaurs. Anat Rec, 303:772-789, 2020. © 2019 American Association for Anatomy.

Based on a representative sample set (41 specimens), features of external morphology, seismosensory system, and axial skeleton of the sailfish pike Channichthys velifer (Channichthyidae) are described and compared to the corresponding features in a closely related species, ginger (rugose) pike Ch. rugosus.

We previously showed the importance of TGFβ signaling in development of the mouse axial skeleton. Here, we provide the first direct evidence that TGFβ signaling is required for resegmentation of the sclerotome using chick embryos. Lipophilic fluorescent tracers, DiO and DiD, were microinjected into adjacent somites of embryos treated with or without TGFβR1 inhibitor, SB431542, at developmental day E2.5 (HH16). Lineage tracing of labeled cells was observed over the course of 4 days until the completion of resegmentation at E6.5 (HH32). Vertebrae were malformed and intervertebral discs were small and misshapen in SB431542 injected embryos. Hypaxial myofibers were also increased in thickness after treatment with the inhibitor. Inhibition of TGFβ signaling resulted in alterations in resegmentation that ranged between full, partial, and slanted shifts in distribution of DiO or DiD labeled cells within vertebrae. Patterning of rostro- caudal markers within sclerotome was disrupted at E3.5 after treatment with SB431542 with rostral domains expressing both rostral and caudal markers. We propose that TGFβ signaling regulates rostro-caudal polarity and subsequent resegmentation in sclerotome during spinal column development.

In mammals, the caudal vertebrae are certainly among the least studied elements of their skeleton. However, the tail plays an important role in locomotion (e.g., balance, prehensility) and behavior (e.g., signaling). Previous studies largely focused on prehensile tails in Primates and Carnivora, in which certain osteological features were selected and used to define tail regions (proximal, transitional, distal). Interestingly, the distribution pattern of these anatomical characters and the relative proportions of the tail regions were similar in both orders. In order to test if such tail regionalization can be applied to Rodentia, we investigated the caudal vertebrae of 20 Sciuridae and six Gliridae species. Furthermore, we examined relationships between tail anatomy/morphometry and locomotion. The position of selected characters along the tail was recorded and their distribution was compared statistically using Spearman rank correlation. Vertebral body length (VBL) was measured to calculate the proportions of each tail region and to perform procrustes analysis on the shape of relative vertebral body length (rVBL) progressions. Our results show that tail regionalization, as defined for Primates and Carnivora, can be applied to almost all investigated squirrels, regardless of their locomotor category. Moreover, major locomotor categories can be distinguished by rVBL progression and tail region proportions. In particular, the small flying squirrels Glaucomys volans and Hylopetes sagitta show an extremely short transitional region. Likewise, several semifossorial taxa can be distinguished by their short distal region. Moreover, among flying squirrels, Petaurista petaurista shows differences with the small flying squirrels, mirroring previous observations on locomotory adaptations based on their inner ear morphometry. Our results show furthermore that the tail region proportions of P. petaurista, phylogenetically more basal than the small flying squirrels, are similar to those of bauplan-conservative arboreal squirrels.

Adolescent idiopathic scoliosis (AIS) is the most common spine disorder affecting children worldwide, yet little is known about the pathogenesis of this disorder. Here, we demonstrate that genetic regulation of structural components of the axial skeleton, the intervertebral discs, and dense connective tissues (i.e., ligaments and tendons) is essential for the maintenance of spinal alignment. We show that the adhesion G protein-coupled receptor ADGRG6, previously implicated in human AIS association studies, is required in these tissues to maintain typical spine alignment in mice. Furthermore, we show that ADGRG6 regulates biomechanical properties of tendon and stimulates CREB signaling governing gene expression in cartilaginous tissues of the spine. Treatment with a cAMP agonist could mirror aspects of receptor function in culture, thus defining core pathways for regulating these axial cartilaginous and connective tissues. As ADGRG6 is a key gene involved in human AIS, these findings open up novel therapeutic opportunities for human scoliosis., eLife, 10, ISSN:2050-084X

Middle Jurassic sauropod taxa are poorly known, due to a stratigraphic bias of localities yielding body fossils. One such locality is Cerro Cóndor North, Cañadón Asfalto Formation, Patagonia, Argentina, dated to latest Early-Middle Jurassic. From this locality, the holotype of Patagosaurus fariasi Bonaparte 1986 is revised. Th e material consists of the axial skeleton, the pelvic girdle, and the right femur. Patagosaurus is mainly characterised by a combination of features mainly identifi ed on the axial skeleton, including the following: 1) cervical centra with low Elongation Index; 2) high projection of the postzygodiapophyseal lamina; 3) deep anterior pleurocoels that are sometimes compartmentalized in cervicals; 4) high projection of the neural arch and spine in dorsal vertebrae and anterior(most) caudal vertebrae; 5) deep pneumatic foramina in posterior dorsals which connect into an internal pneumatic chamber; and 6) anterior caudal vertebrae with ‘saddle’ shaped neural spines. Diagnostic features on the appendicular skeleton include: 1) a transversely wide and anteroposteriorly short femur; 2) a medial placement of the fourth trochanter on the femur; and 3) an anteroposteriorly elongated ilium with a rounded dorsal rim, with hook-shaped anterior lobe. Th e characters that are diagnostic for Patagosaurus are discussed, and the osteology of Patagosaurus is compared to that of Early and Middle Jurassic (eu)sauropods from both Laurasia and Gondwana.

The genera Mitophis and Tetracheilostoma comprise two extant lineages of small-sized threadsnakes that exclusively inhabit several islands of the West Indies. Even though leptotyphlopids are known for their extremely reduced size, miniaturization has only been hypothesized to reflect insular dwarfism for the genus Tetracheilostoma. Herein, we aim to describe the comparative osteology and visceral morphology of both genera, investigating and discussing their several internal morphological simplifications and novelties. Our results indicate that these taxa exhibit several autapomorphies mostly concentrated in the dorsoposterior skull elements and maxillae, as well as in their axial skeleton and viscera. These novelties and simplifications are most likely a result of extreme miniaturization driven by the evolutionary constraints or ecological opportunities possibly imposed by the "island rule." Both Mitophis and Tetracheilostoma distinguish from all other Epictinae in lacking a dentigerous process in the maxillae, by having the prootic fused to the otooccipital, and by the lack (except in comparison to a few Epictia) of a cervical vertebrae intercentrum I. Additionally, Mitophis can be distinguished from other Epictinae by the participation of the unpaired supraoccipital in the dorsal border of the foramen magnum, by the absence of the pleurapophyses in the caudal vertebrae, by a higher number of liver segments, and by the extreme degeneration of the pelvic rudiments. Tetracheilostoma differs from other Epictinae by lacking a distinct supraoccipital, which is fused to the parietal. Thus, our results reinforce that morphological characters are extremely valuable for leptotyphlopid systematics given their extremely conserved external morphology.

Changes in external morphological characters and relative lengths of vertebral centra from different regions of the vertebral column are analyzed during smoltification in wild juveniles of five salmonid fish species: Atlantic salmon Salmo salar, brown trout S. trutta, mikizha Parasalmo mykiss, coho salmon Oncorhynchus kisutch, and northern Dolly Varden Salvelinus malma. The changes in the body proportions and external morphology are similar in different salmonid species, but the patterns of differentiation of the vertebral column’s postanal part are different. In Atlantic salmon, all vertebral centra of the postanal part are subject to elongation; in mikizha and brown trout, a small number of the centra are elongated only in the anterior region of the postanal part; in coho salmon, the centra are elongated in the posterior region of the postanal part; in Dolly Varden, the centra are elongated in the middle region of the postanal part. Thus, despite observed universal changes in external morphology associated with smoltification in the family Salmonidae, the development of future marine migrants' phenotypes is species-specific due to different growth of various groups of vertebral centra in the vertebral column’s postanal part. The possible reasons for the species diversity in the growth of various groups of vertebral centra are discussed.

The variability of morphometric characteristics, the structure of the seismosensory system and the external skeleton in females and nonspawning and spawning males of the spotted lumpsucker Eumicrotremus pacificus were studied. Females differed from males in their greater anteanal distance and stability of the structure of the external skeleton throughout the adult period of life. Spawning males are characterized by a significant change in a number of plastic characters and the structure of their external skeleton, apparently related to the features of the spawning biology of the Eumicrotremus species. No noticeable variability was revealed in the structure of the axial skeleton, the skeleton of unpaired fins, and the seismosensory system of the head of E. pacificus. Using the characters of external morphology and the external skeleton of females and nonspawning males in the systematics of the lumpfishes was confirmed as valid.

Australopitheus anamensis fossils demonstrate that craniodentally and postcranially the taxon was more primitive than its evolutionary successor Australopithecus afarensis. Postcranial evidence suggests habitual bipedality combined with primitive upper limbs and an inferred significant arboreal adaptation. Here we report on A. anamensis fossils from the Assa Issie locality in Ethiopia's Middle Awash area dated to ∼4.2 Ma, constituting the oldest known Australopithecus axial remains. Because the spine is the interface between major body segments, these fossils can be informative on the adaptation, behavior and our evolutionary understanding of A. anamensis. The atlas, or first cervical vertebra (C1), is similar in size to Homo sapiens, with synapomorphies in the articular facets and transverse processes. Absence of a retroglenoid tubercle suggests that, like humans, A. anamensis lacked the atlantoclavicularis muscle, resulting in reduced capacity for climbing relative to the great apes. The retroflexed C2 odontoid process and long C6 spinous process are reciprocates of facial prognathism, a long clivus and retroflexed foramen magnum, rather than indications of locomotor or postural behaviors. The T1 is derived in shape and size as in Homo with an enlarged vertebral body epiphyseal surfaces for mitigating the high-magnitude compressive loads of full-time bipedality. The full costal facet is unlike the extant great ape demifacet pattern and represents the oldest evidence for the derived univertebral pattern in hominins. These fossils augment other lines of evidence in A. anamensis indicating habitual bipedality despite some plesiomorphic vertebral traits related to craniofacial morphology independent of locomotor or postural behaviors (i.e., a long clivus and a retroflexed foramen magnum). Yet in contrast to craniodental lines of evidence, some aspects of vertebral morphology in A. anamensis appear more derived than its descendant A. afarensis.

Growth and differentiation factor 11 (GDF11) is a transforming growth factor β family member that has been identified as the central player of anterior–posterior (A–P) axial skeletal patterning. Mice homozygous for Gdf11 deletion exhibit severe anterior homeotic transformations of the vertebrae and craniofacial defects. During early embryogenesis, Gdf11 is expressed predominantly in the primitive streak and tail bud regions, where new mesodermal cells arise. On the basis of this expression pattern of Gdf11 and the phenotype of Gdf11 mutant mice, it has been suggested that GDF11 acts to specify positional identity along the A–P axis either by local changes in levels of signaling as development proceeds or by acting as a morphogen. To further investigate the mechanism of action of GDF11 in the vertebral specification, we used a Cdx2‐Cre transgene to generate mosaic mice in which Gdf11 expression is removed in posterior regions including the tail bud, but not in anterior regions. The skeletal analysis revealed that these mosaic mice display patterning defects limited to posterior regions where Gdf11 expression is deficient, whereas displaying normal skeletal phenotype in anterior regions where Gdf11 is normally expressed. Specifically, the mosaic mice exhibited seven true ribs, a pattern observed in wild‐type (wt) mice (vs. 10 true ribs in Gdf11 −/− mice), in the anterior axis and nine lumbar vertebrae, a pattern observed in Gdf11 null mice (vs. six lumbar vertebrae in wt mice), in the posterior axis. Our findings suggest that GDF11, rather than globally acting as a morphogen secreted from the tail bud, locally regulates axial vertebral patterning.

Background. The study of normal embryonic development of the vertebral column is important for understanding the pathogenesis of congenital anomalies of the axial skeleton. Objective. To study the histodifferentiation of cartilage and bone tissue in the vertebral centra and neural arches of particular parts of the vertebral column in human embryos of the first half of fetal development. Methods. Whole-mount skeletal preparations, stained with alcian blue and alizarin red, as well as serial histological sections from the embryological collections of the Belarusian State Medical University and from the Carnegie collection (3D Atlas of Human Embryology project, https://www.ehd.org/virtual-human-embryo/ ) using hematoxylin and eosin and Masson's trichrome staining were studied. A total of 37 human embryos/fetuses from 5 to 20 weeks of age were used. Results. "Primary" centers of ossification were found in the neural arches of the upper cervical and centra of lower thoracic and upper lumbar vertebrae of 9-10-week human embryos. They consist of hypertrophic chondrocytes surrounded by a mineralized matrix. Complete ossification of the cartilaginous anlages of the vertebral bodies begins at 12 week of embryogenesis. The appearance of the osteoid and structural elements of the bone marrow in their centers is preceded by the ingrowth of vascular canаls. In the vertebral neural arches, the formation of bone tissue occurs due to endochondral and perichondral ossification. Three growth zones are formed near the ossification center – one is for the region of the pedicle of the neural arch; the other for the lamina/spinous process; the third – for the base of the transverse process. Conclusion. According to the histological structure, the ossification of the vertebral body is similar to the "secondary" ossification center of long bone, and the ossification center in the neural arch at the microscopic level resembles the diaphyseal ossification center of the long bone. Differences in the timing of appearance and osteogenic pathways of the vertebral centra and neural arches are determined by different sources of their origin.

Many teleost fishes with no apparent modifications for life on land are able to produce effective terrestrial locomotor behaviors, including a ballistic behavior called the "tail-flip" jump. Cyprinodontiformes (killifishes, Teleostei: Atherinomorpha) that live at the water's edge vary in morphology and inclination to emerge onto land. Do fish with an amphibious predisposition have extensive modification of the propulsive region of the body when compared to fully aquatic relatives? We quantified body shape and anatomy of the caudal peduncle and tail (the propulsive organ on land and in water) in 11 cyprinodontiform species and two outgroup taxa (Atherinomorpha). We hypothesized that amphibious species would have longer, "shallower" bodies (larger body fineness ratios), deeper (proportionally larger) caudal peduncles, and more robust bones in the tail fin (larger ossified area of the hypural/epural bones) to facilitate locomotor movements on land. We found no evidence of convergence in body shape or skeletal anatomy among species known to make voluntary sojourns onto land. In fact, deep-bodied species, shallow-bodied species, and species with intermediate morphologies all are able to emerge from the water and move on land. It is possible that there are as-yet-undocumented subtle soft-tissue (muscle, tendon, and ligament) modifications that enhance terrestrial locomotor performance in species known to spend large periods of time on land. However, it is also possible that extreme anatomical changes are not required for aquatic cyprinodontiform species to produce effective locomotor movements when they emerge out of the water and move across the land. Anat Rec, 2019. © 2019 American Association for Anatomy.

© 2019 American Society for Investigative Pathology Mitogen-activated protein kinases, including c-Jun NH2-terminal kinase (JNK), play an important role in the development and function of a large variety of tissues. The skeletal phenotype of JNK1 and JNK2 double-knockout (dKO) mice (JNK1 fl/fl Col2-Cre/JNK2 −/− ) and control genotypes were analyzed at different embryonic and postnatal stages. JNK1/2 dKO mice displayed a severe scoliotic phenotype beginning during development that was grossly apparent around weaning age. Alcian blue staining at embryonic day 17.5 showed abnormal fusion of the posterior spinal elements. In adult mice, fusion of vertebral bodies and of spinous and transverse processes was noted by micro–computed tomography, Alcian blue/Alizarin red staining, and histology. The long bones developed normally, and histologic sections of growth plate and articular cartilage revealed no significant abnormalities. Histologic sections of the vertebral column at embryonic days 15.5 and 17.5 revealed an abnormal organization of the annulus fibrosus in the dKOs, with chondrocyte-like cells and fusion of dorsal processes. Spinal sections in 10-week–old dKO mice showed replacement of intervertebral disk structures (annulus fibrosus and nucleus pulposus) by cartilage and bone tissues, with cells staining for markers of hypertrophic chondrocytes, including collagen X and runt-related transcription factor 2. These findings demonstrate a requirement for both JNK1 and JNK2 in the normal development of the axial skeleton. Loss of JNK signaling results in abnormal endochondral bone formation and subsequent severe scoliosis.

Lizards are animals that can do autotomy. Research on the autotomy of lizard’s tail has been carried out, but few have examined about axial skeletons that focus on vertebrae caudales or arranged muscles. That is the background of this research. This research is expected to be a database for further research and as a comparison between animals that can perform other autotomies. This research intend to determine the macro and micro structures of the anatomical axial skeleton lizard’s regenerate tail and to know the micro structures of anatomy muscular segmentation lizard’s regenerate tail. The used methods are X-Ray, Alizarin Red S and Alcian Blue, Paraffin method with Hematoxylin-Eosin and Mallory Triple Strain staining. The result showed that the lizard's regenerate tail was darker than the original. On observations using X-Ray and Alizarin staining showed that the original tail is seen broad and have a Processus. The original lizard's tail is composed of bones, because it is red which shows perfectly calcified bones. While the regenerate of the lizard's tail is composed of bones in the form of long pipes which are red-colored because they have calcified from outside. Muscular segmentation of the original lizard's tail when viewed transversely has irregular segments. While the lizard's regenerate tail has 15 muscle segments. Muscles are composed of a collection of myotubes that become myotomes, each of myotomes confined by the myoseptum.

Turtles are reptiles armored backs hard, slow motion, appearing for the first time about 200 million years ago and relative ly unchanged for 150 million years. This study aims to determine the anatomical structure of the axial skeleton and determine the histologic structure of red-eared turtles (Trachemys scripta elegans) females. The method used, among others, Alizarin Red S staining Alcian Blue, methods of paraffin with Hematoxylin-eosin staining (HE) and Mallory acid fuchsin and used 3 adult turtles 3 years old. The results showed that vertebral caudalis red-eared turtles (Trachemys scripta elegans) females composed of true bone, vertebrae-type amphicoelous not have plains autotomy and histology red-eared turtles (Trachemys scripta elegans) females resemble histological structure other tail reptiles with some differences that only have 4 files do not have the muscle and fat tissue.

Gecko is an animal that can carry out autotomy. Research on gecko tail autotomy has been carried out, but there are still few who research the axial skeleton that focuses on vertebrae caudales and segmentation muscular arranged, this is the background of this research. This research is expected to be data base further research and as a comparison between animals that can induce further autotomy. This study aims to determine the macrostructure and microstructure of axial axial gecko tail regenerates and determine the anatomical microstructure of muscular regeneration of gecko tail. The methods used were X-Ray, Alizarin Red S and Alcian Blue, Paraffin method with hematoxylin-eosin staining, and Mallory Triple Stain. The results showed that the color of the gecko tail regenerate was paler compared to the original tail. On observations using radiological rays and alizarin staining showed that the original tail wo uld look segmented and have a process. The original gecko tail is composed of bones, because it is red which shows perfectly calcified bone. While the gecko tail regenerate is composed of cartilage that is shaped like a long pipe glazed red because it has calcified. At the end of the tail there is also a blue color, this indicates that the gecko tail regenerate has not been completely calcified. Segmentation Muscular of the original gecko tail, when viewed longitudinally, indicates a segment that extends from one process to the skin and when viewed from the cross has only four muscle segments separated by the septum. While the gecko tail regenerate when viewed in a longitudinal manner there is no segment and when seen transversely there are 12 muscle segments seen. Muscles are composed of a collection of myotubes that form myotomes, each myotomes limited by myoseptum.

Red-eared turtle and softshell turtles belong Cryptodira Suborder which has a different characteristic in neck length and head movement. The aim of this study was to determine of the axial skeleton anatomical structure including vertebrae, carapace and plastron of the red-eared turtle (Trachemys scripta elegans Wied, 1838) and softshell turtles (Amyda cartilaginea Boddaert, 1770) females. This research was carried out for five months starting from September 2013 to January 2014. The methods used in this study were th e X-Ray method, boiled bone and Alizarin Red S-Alcian blue staining. The result of research was analyzed descriptively comparatively by direct observation using a digital camera. Based on the results of the study the Red-eared turtle tortoise has a number of 7 cervical vertebrae, 9th vertebrae, sacral vertebrae 1 segment and vertebrae caudalis 27 segments. The anterior and posterior zygapophysis of the cervix elongate thus affecting the limited lateral movement. The thoracic center of the vertebrae adjusts the shape of the carapace. The sacralis vertebrae have 1 centrum segment extending on the lateral side attached to the carapace called the lateral pars, the caudal centrum is short and there is a shortened anterior zygapophysis structure. Whereas softshell turtles have slender and long centrums. The anterior and posterior zygapophysis are smaller and allow the softshell turtles to perform more lateral movements. Centrum vertebrae of the thorachalis have a flat shape adjusting the shape of the carapace. Sacralis vertebrae have 2 centrum and 2 lateral pars extending and meeting each other to form a hole sacralia pelvina, centrum vertebrae caudalis extends and there is a neural spinal structure. Carapace of the red-eared turtle consists of fused pieces. Whereas the carapace in the softshell turtles consists of pieces covered by cartilage. The constituent component of carapace and plastron of the red-eared turtle consists of true bones completely, while the constituent components of the carapace and plastron of softshell turtles consist of true bones and cartilage on the sides and connective between the carapace and plastron.

Snakes exhibit a diverse array of body shapes despite their characteristically simplified morphology. The most extreme shape changes along the precloacal axis are seen in fully aquatic sea snakes (Hydrophiinae): "microcephalic" sea snakes have tiny heads and dramatically reduced forebody girths that can be less than a third of the hindbody girth. This morphology has evolved repeatedly in sea snakes that specialize in hunting eels in burrows, but its developmental basis has not previously been examined. Here, we infer the developmental mechanisms underlying body shape changes in sea snakes by examining evolutionary patterns of changes in vertebral number and postnatal ontogenetic growth. Our results show that microcephalic species develop their characteristic shape via changes in both the embryonic and postnatal stages. Ontogenetic changes cause the hindbodies of microcephalic species to reach greater sizes relative to their forebodies in adulthood, suggesting heterochronic shifts that may be linked to homeotic effects (axial regionalization). However, microcephalic species also have greater numbers of vertebrae, especially in their forebodies, indicating that somitogenetic effects also contribute to evolutionary changes in body shape. Our findings highlight sea snakes as an excellent system for studying the development of segment number and regional identity in the snake precloacal axial skeleton.

Snakes are an extremely modifed and long-lived clade of lizards that have either lost or highly altered many of the synapomorphies that would clearly link them to their closest sister-group among squamates. We focus here on one postcranial morphological complex, the intercentrum system which in most non-ophidian squamates is limited to the cervical and caudal regions. The Cervical Intercentrum System (CeIS) is composed of a single intercentral element that sometimes articulates with a ventral projection (hypapophyses) of the centrum; the Caudal Intercentrum System (CaIS) is formed by an intercentral element, the haemal arch/chevron bone, and paired ventral projections of the centrum, the haemapophyses. In modern snakes, the intercentrum element of the CeIS is considered lost or fused to the hypaphophysis, and the chevron bone in CaIS is considered lost. Here, we describe new specimens of the early snake Dinilysia patagonica, and reinterpret previously known specimens of Dinilysia and Najash rionegrina, that do not show the expected snake morphology. The anatomy of these fossil taxa unambiguously shows that free cervical and caudal intercentra attached to distinct downgrowths (hypapophyses and haemapophyses) of the centra, are present in basal fossil snakes, and agrees with the proposed loss of post atlas-axis intercentra in later evolving snakes. Fil: Garberoglio, Fernando Fabio. Universidad Maimónides. Área de Investigaciones Biomédicas y Biotecnológicas. Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y de Diagnóstico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Gómez, Raúl Albero. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina Fil: Simões, Tiago R.. University of Alberta; Canadá Fil: Caldwell, Michael Wayne. University of Alberta; Canadá Fil: Apesteguía, Sebastián. Universidad Maimónides. Área de Investigaciones Biomédicas y Biotecnológicas. Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y de Diagnóstico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Taspase1, a highly conserved threonine protease encoded by TASP1, cleaves nuclear histone modifying factors and basal transcription regulators to orchestrate diverse transcription programs. Hereditary loss-of-function mutation of TASP1 has recently been reported in human resulting in a novel anomaly complex syndrome manifested with hematological, facial, and skeletal abnormalities. Here, we demonstrate that Taspase1-mediated cleavage of TFIIAα-β, rather than of MLL1 or MLL2, in mouse embryos is required for proper fetal liver hematopoiesis and correct segmental identities of the axial skeleton. Homozygous genetic deletion of Taspase1 (Tasp1-/-) disrupted embryonic hematopoietic stem cell self-renewal and quiescence states, and axial skeleton fates. Strikingly, mice carrying knockin non-cleavable mutations of TFIIAα-β (Gtf2a1nc/nc), a well-characterized basal transcription factor, displayed more pronounced fetal liver and axial skeleton defects than those with non-cleavable MLL1 and MLL2 (Mll1nc/nc;2nc/nc), two trithorax group (Trx-G) histone H3 trimethyl transferases. Our study offers molecular insights concerning TASP1-loss human syndrome and discovers unexpected role of TFIIAα-β cleavage in embryonic cell fate decisions.

Skeletal deformities reduce fish viability, growth, wellbeing, and feed efficiency but also degrade the consumer’s perception of aquaculture products. Herein, the skeletal development and the incidence of skeletal deformities in tench (Tinca tinca) reared in semi-extensive conditions has been described in detail for the first time. Larval skeletons were assessed through an acid-free double-staining procedure in 157 individuals, while 274 specimens at the juvenile stage were evaluated through X-ray analysis. The first skeletal structures to be formed were those related with breathing and feeding activities (e.g., Meckel’s cartilage and opercula) and were visible in larvae of 4 mm of standard length (SL). The axial skeleton was fully ossified in larvae of 12–17 mm of SL, and the caudal fin complex in larvae with 17–26 mm of SL. At the larval stage, no upper-jaw or opercula deformities were observed, while a low incidence (1–9%) of other severe deformities in the heads of the fish (e.g., lower-jaw deformities) were reported. The incidence of vertebral deformities in tench reared in natural ponds was considerable in larvae (54%) and juveniles (52%). Vertebral deformities (fusion and compression) were the most common deformities found in tench larvae (approximately 30%) and vertebral shape deformity in juveniles (around 10%), being mainly located in the caudal region. Thus, a regular monitoring of the skeletal deformities in tench might help to identify better rearing protocols and improve product quality sold at markets. Characterizing the skeletal development not only in semi-extensive systems such as artificial and natural ponds but also under intensive rearing conditions, seems vital for a sustainable and profitable European tench aquaculture.

SummaryAdolescent idiopathic scoliosis (AIS) is the most common spine disorder affecting children worldwide, yet little is known about the pathogenesis of this disorder. Here, we demonstrate that genetic regulation of structural components of the axial skeleton, the intervertebral discs and dense connective tissues (e.g., ligaments and tendons), are essential for maintenance of spinal alignment. We show that the G-coupled protein receptorAdgrg6, previously implicated in human AIS association studies, is required in these tissues to maintain typical spine morphology. We show thatAdgrg6regulates biomechanical properties of tendon and stimulates CREB signaling governing gene expression in cartilaginous tissues of the spine. Treatment with an cAMP agonist was able to mirror aspects of receptor function in culture defining core pathways for regulation of these axial connective tissues. AsADGRG6is a key gene involved in human AIS, these findings open up novel therapeutic opportunities for human scoliosis.HighlightsKnockout mice lackingAdgrg6function in the tendons and ligaments of the spine develop perinatal-onset thoracic scoliosis.Loss ofAdgrg6function in cartilaginous tissues of the discs contribute to the incidence and severity of scoliosis.The loss ofAdgrg6function in spine tissues provide a model of construct validity for human adolescent idiopathic scoliosisFine tuning of the biomechanical properties of dense connective tissues is essential for maintaining spine alignment.

Spondylocostal dysostosis (SCDO) is a rare heritable congenital condition, characterized by multiple severe malformations of the vertebrae and ribs. Great advances were made in the last decades at the clinical level, by identifying the genetic mutations underlying the different forms of the disease. These were matched by extraordinary findings in the Developmental Biology field, which elucidated the cellular and molecular mechanisms involved in embryo body segmentation into the precursors of the axial skeleton. Of particular relevance was the discovery of the somitogenesis molecular clock that controls the progression of somite boundary formation over time. An overview of these concepts is presented, including the evidence obtained from animal models on the embryonic origins of the mutant-dependent disease. Evidence of an environmental contribution to the severity of the disease is discussed. Finally, a brief reference is made to emerging in vitro models of human somitogenesis which are being employed to model the molecular and cellular events occurring in SCDO. These represent great promise for understanding this and other human diseases and for the development of more efficient therapeutic approaches. PTDC/BEX-BID/5410/2014, SFRH/BD/146043/2019, UID/BIM/04773/2019 info:eu-repo/semantics/publishedVersion

Therizinosaurs are highly modified, probably herbivorous, theropods from the Upper Cretaceous of Asia and North America. They are characterized by an extensively pneumatized axial skeleton, and in the derived forms, an incipiently opisthopubic pelvis. The evolution of such a pelvis is expected to be associated with extensive modification of the muscular system. The muscular system is reconstructed using observed muscle scars, reconstructions of the theropods Staurikosaurus and Tyrannosaurus, the ornithischian Maiasaura, and extant crocodilians and birds. The results indicate convergence with birds and ornithischian dinosaurs, such that the retroverted pubis in some maniraptorans can be regarded as analogous with the postacetabular bar in ornithischians. Functional implications also make derived therizinosaurs, such as Nothronychus, in some respects convergent with birds as the pubis is retroverted, becoming fused with the ischium, a laterally flaring synsacrum, and an avian-like pes.

Chordomas are locally aggressive, slow-growing tumors. Typically found in the axial skeleton, they are thought to be derived from notochord remnants. The notochord is a critical midline structure present in the early weeks of embryogenesis, where it plays a critical role in left-right and local tissue development. While the nucleus pulposus of the intervertebral disk appears to be derived from the primitive notochord, remnant notochordal cells can be found throughout adult vertebrae. What drives the transition from remnant notochord cell to chordoma remains elusive, and is likely multifactorial, but the expression of the brachyury gene appears central to this process. While wide resection remains the gold standard when possible (with or without radiation), these difficult-to-treat tumors have a high local recurrence rate even when appropriate margins appeared to have been achieved. By better understanding the role of the notochord and notochordal morphogenesis in the origins of chordomas, more efficacious, targeted therapies are currently being developed.

Background Diaphanospondylodysostosis (DSD) is a rare congenital, lethal skeletal disorder caused by recessively inherited mutations in the BMPER gene, which encodes the bone morphogenetic protein‐binding endothelial cell precursor‐derived regulator. The most prominent features of DSD are missing ossification of the axial skeleton, rib abnormalities and thoracic hypoplasia/insufficiency, as well as intralobar nephrogenic rests within the kidneys. Methods We report on the case of a 22‐month‐old patient with DSD where trio‐exome sequencing was performed. Results Genetic testing revealed a homozygous nonsense variant c.1577G>A (p.Trp526*) in the BMPER gene, leading to a premature stop in protein translation. Both parents are asymptomatic carriers for the BMPER variant, which has not been described in the literature before. Conclusions Our findings expand the genotypic and phenotypic spectrum of BMPER variants leading to DSD., Diaphanospondylodysostosis (DSD) is a rare congenital, lethal skeletal disorder caused by recessively inherited mutations in the BMPER gene, which encodes the bone morphogenetic protein‐binding endothelial cell precursor‐derived regulator. The most prominent features of DSD are missing ossification of the axial skeleton, rib abnormalities and thoracic hypoplasia/insufficiency, as well as intralobar nephrogenic rests within the kidneys. We report on the case of a patient with DSD where trio‐exome sequencing revealed an undescribed, homozygous nonsense‐variant c.1577G>A (p.Trp526*) in the BMPER gene, leading to a premature stop in protein translation. Our findings expand the genotypic and phenotypic spectrum of BMPER variants leading to DSD.

The axial skeleton of all vertebrates is composed of individual units known as vertebrae. Each vertebra has individual anatomical attributes, yet they can be classified in five different groups, namely cervical, thoracic, lumbar, sacral and caudal, according to shared characteristics and their association with specific body areas. Variations in vertebral number, size, morphological features and their distribution amongst the different regions of the vertebral column are a major source of the anatomical diversity observed among vertebrates. In this review I will discuss the impact of those variations on the anatomy of different vertebrate species and provide insights into the genetic origin of some remarkable morphological traits that often serve to classify phylogenetic branches or individual species, like the long trunks of snakes or the long necks of giraffes.

Chordoma is a rare malignant primary tumor of the axial skeleton. In recent years, advances in understanding the genetic and molecular events underpinning chordoma tumorigenesis have provided insight into avenues for more effective targeted therapies. We highlight current concepts in the molecular morphogenesis and genetic landscape of spinal chordomas.

The transcription factor Nkx3.2 (Bapx1) is an important chondrocyte maturation inhibitor. PreviousNkx3.2knock-down and overexpression studies in non-mammalian gnathostomes have focused on its role in primary jaw joint development, while little is known about the function of this gene in broader skeletal development. We generated CRISPR/Cas9 knockout ofnkx3.2in zebrafish and applied a range of techniques to characterize skeletal phenotypes at developmental stages from larva to adult, revealing fusions in bones of the occiput, the loss or deformation of bony elements derived from basiventral cartilages of the vertebrae, and an increased length of the proximal radials of the dorsal and anal fins. These phenotypes are reminiscent ofNkx3.2knockout phenotypes in mammals, suggesting that the function of this gene in axial skeletal development is ancestral to osteichthyans. Our results highlight the broad role ofnkx3.2in zebrafish skeletal development and its context-specific functions in different skeletal elements.

The avian lung is highly specialized and is both functionally and morphologically distinct 30 from that of their closest extant relatives, the crocodilians. It is highly partitioned, with a 31 unidirectionally ventilated and immobilized gas-exchanging lung, and functionally decoupled, 32 compliant, poorly vascularized ventilatory air-sacs. To understand the evolutionary history of 33 the archosaurian respiratory system, it is essential to determine which anatomical 34 characteristics are shared between birds and crocodilians and the role these shared traits play 35 in their respective respiratory biology. To begin to address this larger question, we examined 36 the anatomy of the lung and bronchial tree of ten American alligators (Alligator 37 mississippiensis) and eleven ostriches (Struthio camelus) across an ontogenetic series using 38 traditional and micro-computed tomography (µCT), three-dimensional (3D) digital models, and 39 morphometry. Intraspecific variation and left to right asymmetry were present in certain 40 aspects of the bronchial tree of both taxa but was particularly evident in the cardiac (medial) 41 region of the lungs of alligators and the caudal aspect of the bronchial tree in both species. The 42 cross-sectional area of the primary bronchus at the level of the major secondary airways and 43 cross-sectional area of ostia scaled either isometrically or negatively allometrically in alligators 44 and isometrically or positively allometrically in ostriches with respect to body mass. Of fifteen 45 lung metrics, five were significantly different between the alligator and ostrich, suggesting that 46 these aspects of the lung are more interspecifically plastic in archosaurs. One metric, the 47 distances between the carina and each of the major secondary airways, had minimal 48 intraspecific or ontogenetic variation in both alligators and ostriches, and thus may be a 49 conserved trait in both taxa. In contrast to previous descriptions, the 3D digital models and CT 50 scan data demonstrate that the pulmonary diverticula pneumatize the axial skeleton of the 51 ostrich directly from the gas-exchanging pulmonary tissues instead of the air sacs. Global and 52 specific comparisons between the bronchial topography of the alligator and ostrich reveal 53 multiple possible homologies, suggesting that certain structural aspects of the bronchial tree 54 are likely conserved across Archosauria, and may have been present in the ancestral 55 archosaurian lung.