Skeletal Elements Research Articles

Phosphatization of rocks and organic remains of the basal horizon of the Lower Eocene of the Middle Dnipro area


 
 
 The purpose of the work is to determine the mechanism of phosphorus deposition during the formation of deposits of Kanivska suite (Р2kn) within the region of the Middle Dnipro by researching the components of phosphorite contractions. The studied conglomerate-like formations were cemented with phosphate substance, selected from the basal horizon of the Kanivska suite for the purpose of their petrographic and paleontological study. Phosphorites of the basal horizon are formed in different shapes, colors and sizes. The phosphate substance that cements them (according to our data) varies in ages. Pebble inclusions in conglomerates that are the phosphatized remains of ichnofauna belong to the washed phosphates of the Cenomanian age of the Late Cretaceous, which entered the basal horizon of the Eocene as a result of washing, condensation, and new phosphatization during the Early Eocene transgression. The phosphate substance of these inclusions is represented by the mineral kurskite (Carbonate Rich Apatite) of three modifications: amorphous, microcrystalline, and radial-radiant which reflect different generations and diagenetic stages of phosphorite formation (Bushinsky, 1954). Phosphate of first-generation exists in the form of globules of amorphous kurskite and is a pore-filling material between sediment grains. The second type is the microcrystalline kurskite, which forms layers of film around sediment grains, with the thickness of 0.01–0.02 mm, has concentric microstructure and barely noticeable anisotropy. Aggregates of needle-like radiating anisotropic kurskite have a sheaf-like, parallel-fibrous structure oriented perpendicular to the surface of the fragments. They are the result of the further recrystallization of kurskite. Phosphate amorphous cementing substance had formed, in our opinion, in an early Eocene age. It contains numerous remnants of opal and partially phosphatized flora and fauna – diatoms, radiolarians, and spicules of sponges, as well as fragments of Phyto organics. These organisms were the source of additional phosphorus in the sediment. Centers of phosphate formations emerged in places of concentration of dead marine biota, where the processes of bacterial decomposition rapidly began, high concentrations of carbonate and phosphate ions were created, there was a replacement of organic residues with calcium phosphate. The most common in nature are the shells of diatoms and their fragments, which were studied in thin sections. With the most certainty in its attribute outline and shape, preserved fragments of marginal zones, as well as by the type of areola, determined samples of Paralia, Stephanopyxis families, and triangular valves of Trinacria sp. There are also elements of the valves, similar in contours to the family Hemiaulaceae. Phosphate substance and rapid burial contributed to the conservation of thin skeletal elements of microfossils. The determined genitive composition of diatoms from the sections of the basal horizon of the Kanivska suite does not deny their early Eocene age. Diatoms of the early Eocene age have not been known in Ukraine so far, and diatoms of the Middle Dniproarea are being studied for the first time.
 
 

A detailed redescription of the mesoderm/neural crest cell boundary in the murine orbitotemporal region integrates the mammalian cranium into a pan-amniote cranial configuration.

The morphology of the mammalian chondrocranium appears to differ significantly from those of other amniotes, since the former possesses uniquely developed brain and cranial sensory organs. In particular, a question has long remained unanswered as to the developmental and evolutionary origins of a cartilaginous nodule called the ala hypochiasmatica. In this study, we investigated the embryonic origin of skeletal elements in the murine orbitotemporal region by combining genetic cell lineage analysis with detailed morphological observation. Our results showed that the mesodermal embryonic environment including the ala hypochiasmatica, which appeared as an isolated mesodermal distribution in the neural crest-derived prechordal region, is formed as a part of the mesoderm that continued from the chordal region during early chondrocranial development. The mesoderm/neural crest cell boundary in the head mesenchyme is modified through development, resulting in the secondary mesodermal expansion to invade into the prechordal region. We thus revealed that the ala hypochiasmatica develops as the frontier of the mesodermal sheet stretched along the cephalic flexure. These results suggest that the mammalian ala hypochiasmatica has evolved from a part of the mesodermal primary cranial wall in ancestral amniotes. In addition, the endoskeletal elements in the orbitotemporal region, such as the orbital cartilage, suprapterygoid articulation of the palatoquadrate, and trabecula, some of which were once believed to represent primitive traits of amniotes and to be lost in the mammalian lineage, have been confirmed to exist in the mammalian cranium. Consequently, the mammalian chondrocranium can now be explained in relation to the pan-amniote cranial configuration.

A systematic compendium of turtle mandibular anatomy using digital dissections of soft tissue and osteology.

Turtles are a charismatic reptile group with a peculiar body plan, which most notably includes the shell. Anatomists have often focused descriptive efforts on the shell and other strongly derived body parts, such as the akinetic skull, or the cervical vertebrae. Other parts of turtle osteology, like the girdles, limbs, and mandibles, are documented with less rigor and detail. The mandible is the primary skeletal element involved in food acquisition and initial food processing of turtles, and its features are thus likely linked to feeding ecology. In addition, the mandible of turtles is composed of up to seven bones (sometimes fused to as little as three) and has thus anatomical complexity that may be insightful for systematic purposes and phylogenetic research. Despite apparent complexity and diversity to the mandible of turtles, this anatomical system has not been systematically studied, not even in search of characters that might improve phylogenetic resolution. Here, we describe the mandibular osteology for all major subclades of extant turtles with the help of digitally dissected 3D models derived from high-resolution computed tomography (μCT) scans of 70 extant species. We provide 31 fully segmented mandibles, as well as 3D models of the mandibular musculature, innervation, and arterial circulation of the cryptodire Dermatemys mawii. We synthesize observed variation into 51 morphological characters, which we optimize onto a molecular phylogeny. This analysis shows some mandibular characters to have high systematic value, whereas others are highly homoplastic and may underlie ecological influences or other factors invoking variation.

Biometric sex assessment from the femur and tibia in a modern Greek population

Forensic anthropologists assess sex by analysing quantitative and qualitative characters of the human skeleton. In general, the pelvis and skull are the skeletal regions used most often, but in many cases, they are missing or fragmentary. In such circumstances, where only limb bones are present, it is necessary to use techniques based on other skeletal elements. Metric traits of the long bones of the lower extremities have been reported as reliable indicators of sex. This study was designed to determine whether the two main long bones of the leg, the femur and tibia, can be used for the assessment of sex on a Greek skeletal population. The skeletal sample used in this study comes from the modern human skeletal collection that is currently housed at the National and Kapodistrian University of Athens and is known as The Athens Collection. It consists of 371 femora and 372 tibiae corresponding to 200 adult individuals (111 males and 89 females). The age range is 19–96 years for males and 20–99 years for females. The maximum lengths and epiphyseal widths were measured for the present study, and it was found that the discriminant analysis of the metrical data of each long bone provided high sex discrimination accuracies. The rate of correct sex discrimination based on different long bones ranged from 91.50 % (left femur) to 93.40 % (left tibia). Our results suggest that lower limb bones can be used effectively for sexing in forensic contexts, in addition to other sex assessment techniques.

Feeding in the Devonian antiarch placoderm fishes: a study based upon morphofunctional analysis of jaws

AbstractAntiarch placoderm fishes were an abundant component of the Middle Paleozoic vertebrate assemblages. Despite a large number of known taxa and specimens, the morphology and function of the skeletal elements of their jaws is inadequately known. Because of this, questions regarding their feeding modes and their roles in the trophic webs remain open. We present a skeletomuscular model of the antiarch jaw apparatus with an attempt to reconstruct its potential biomechanical function. The position of the upper jaw suborbital bones within the plane of the ventral side of the fish armor is suggested to represent the natural “mouth closed” position. During mouth opening, the suborbitals rotated rostrally with simultaneous depression and inward rotation of the infragnathals. The ball-and-socket jaw articulation might ensure this combined movement. Recently described lower jaw elements ofLivnolepis zadonica(Obrucheva, 1983) andBothriolepissp. from the Upper Devonian (lower Famennian) of Central Russia demonstrating very deep and porous blades of the oral division of the infragnathals queried the structure of these bones in other antiarchs. Observed porosity reflects intense vascularization to supply blood to a connective tissue underlying a supposed keratinous sheath, which protected and strengthened the jaws, as well as made possible scraping tough food objects, such as thallus algae, from the substrate.Having evolved during the Silurian in the Pan-Cathaysian zoogeographical province, antiarchs migrated to Gondwana during the Emsian and later to Euramerica during the Eifelian. Supposedly, antiarchs became the first macrophytophagous vertebrates occupying the trophic level of primary consumers during the late Silurian–Early Devonian. This event diversified the only previously existing predator–prey interrelationships between filter-feeding agnathans and predatory gnathostomes.

Note on new pterosaur remains (Archosauria: Pterodactyloidea) from Cerro La Isla, Atacama region, northern Chile

In this study, new isolated fragmentary pterosaur bones are described from Lower Cretaceous outcrops exposed at Cerro La Isla, a site located approximately 95 km east of Copiapó city, Atacama region, northern Chile. The material consists of a jaw fragment with broken teeth, the caudal portion of a mid-cervical vertebra and the distal portion of a femur. Based on their morphology, the jaw and cervical fragments are assigned to Ctenochasmatidae, a group of pterodactyloid pterosaurs that has been previously reported from this locality, while the femur lacks diagnostic characters that would allow its referral to a more exclusive taxon than Pterodactyloidea indet. This new material confirms the previously proposed presence of ctenochasmatid pterosaurs in the Cretaceous outcrops of Cerro La Isla, and increases the diversity of their skeletal elements discovered at the site.

Survivability versus rate of recovery for skeletal elements in forensic anthropology.

Survivability, the ability of a skeletal element to withstand taphonomic processes, is often equated to recoverability, the probability that an element will be recovered in a forensic context, and further misused to infer the likelihood that a forensic anthropologist will recover a particular element at a scene. Consequently, researchers have utilized notions of survivability to infer that a skeletal element may be recovered when justifying the necessity of various research endeavors. This is problematic because the factors impacting survivability are not always applicable in a forensic context; the ability of a bone to survive taphonomic processes may not align with the likelihood of recovery. Empirical recovery rates are presented from two distinct contexts, with data derived from the Forensic Anthropology Data Bank based on cases performed by the late J. Lawrence Angel (1914-1986) and cases done by the University of Tennessee Knoxville (UTK). Recovery rates may be influenced by factors beyond survivability, though we do not investigate the many considerations that might explain recovery rate variation between datasets. Rather, these data exemplify the conceptual differences between notions of survivability and rates of recovery in actual casework scenarios. Thus, it is proposed that researchers consider documented rates of recovery when providing rationale for forensic anthropology research endeavors, in addition to citing a rationale that is based on inferences of survivability. This ensures that the theoretical framework of future forensic anthropology research stems, primarily, from the premise of practical application.

The last of the large-sized tortoises of the Mediterranean islands

Abstract Archaeological investigations carried out in the cave Zubbio di Cozzo San Pietro, Bagheria, Sicily, revealed the presence of a few skeletal elements of a large-sized tortoise in a funerary area dating to the Copper/Bronze Age. The tortoise has been AMS-dated revealing an age of 12.5 ± 0.5 kyr BP and therefore it pre-dates the funerary activities. The morphology of the retrieved skeletal elements differs from that of the only native tortoise currently living in Sicily, Testudo hermanni. The tortoise’s size significantly exceeds the size range of extant Te. hermanni and all Testudo spp., as well as that of their known fossils, and suggests a shell length of 50–60 cm. Repeated efforts to obtain DNA sequences from the tortoise of Zubbio di Cozzo San Pietro failed, but the morphology of the femur is distinct enough to allow us to erect a new taxon, Solitudo sicula gen. et sp. nov., based on a parsimony analysis. It belongs to a hitherto unrecognized clade that includes other large-sized tortoises from Mediterranean islands, like Malta and Menorca. A review of the pertinent taxa indicates that the remains here described represent the geologically youngest large-sized tortoise of the Mediterranean area.

Skeletomuscular Atlas and Deep Homology of a Metamorphosing Genitalic Appendage in a Flat-Backed Millipede (Polydesmida: Polydesmidae: Pseudopolydesmus)

Abstract In millipedes, gonopods are male copulatory genitalia derived from walking legs that metamorphose during postembryonic development. The morphology of gonopods is critical for genus and species diagnosis in most taxa. However, the form and function of gonopods vary drastically at the family and ordinal level, making intricate morphological comparison practically impossible. Internal morphology could provide the basis for homologizing morphological elements present in the walking legs and gonopods. Therefore, we used x-ray computed tomography to produce 3D segmentations of Pseudopolydesmus Attems, 1898 (Polydesmida: Polydesmidae) millipedes incorporating two types of morphological elements: skeletal elements and muscles. In addition to imaging the trunk and appendages of an adult male, we imaged the developing gonopod across a series of juvenile male stadia in order to trace the identities of morphological elements. Skeletal elements were homologized, but muscle homologies were limited by the dissimilarity of muscle attachment sites between the walking leg and gonopod. Furthermore, images of juvenile males showed that appendage musculature is totally obliterated once gonopod development begins in the fourth stadium. Due to these limitations, we believe it may be more tractable to homologize gonopod musculature of various millipede taxa to each other than to that of the walking legs. Because distinct genetic developmental networks responsible for walking leg and gonopod patterning have been evolving separately since the common ancestor of gonopod-bearing millipedes (a case of paramorphy), skeletomusculature among gonopods of unrelated millipede taxa is expected to be more similar than that of the gonopod and walking leg within a given millipede lineage.

Overexpression of transcription factor FoxA2 in the developing skeleton causes an enlargement of the cartilage hypertrophic zone, but it does not trigger ectopic differentiation in immature chondrocytes.

We previously found that FoxA factors are necessary for chondrocyte differentiation. To investigate whether FoxA factors alone are sufficient to drive chondrocyte hypertrophy, we build a FoxA2 transgenic mouse in which FoxA2 cDNA is driven by a reiterated Tetracycline Response Element (TRE) and a minimal CMV promoter. This transgenic line was crossed with a col2CRE;Rosa26rtTA/+ mouse line to generate col2CRE;Rosa26rtTA/+;TgFoxA2+/- mice for inducible expression of FoxA2 in cartilage using doxycycline treatment. Ectopic expression of FoxA2 in the developing skeleton reveals skeletal defects and shorter skeletal elements in E17.5 mice. The chondro-osseous border was frequently mis-shaped in mutant mice, with small islands of col.10+ hypertrophic cells extending in the metaphyseal bone. Even though overexpression of FoxA2 causes an accumulation of hypertrophic chondrocytes, it did not trigger ectopic hypertrophy in the immature chondrocytes. This suggests that FoxA2 may need transcriptional co-factors (such as Runx2), whose expression is restricted to the hypertrophic zone, and absent in the immature chondrocytes. To investigate a potential FoxA2/Runx2 interaction in immature chondrocytes versus hypertrophic cells, we separated these two subpopulations by FACS to obtain CD24+CD200+ hypertrophic chondrocytes and CD24+CD200- immature chondrocytes and we ectopically expressed FoxA2 alone or in combination with Runx2 via lentiviral gene delivery. In CD24+CD200+ hypertrophic chondrocytes, FoxA2 enhanced the expression of chondrocyte hypertrophic markers collagen 10, MMP13, and alkaline phosphatase. In contrast, in the CD24+CD200- immature chondrocytes, neither FoxA2 nor Runx2 overexpression could induce ectopic expression of hypertrophic markers MMP13, alkaline phosphatase, or PTH/PTHrP receptor. Overall these findings mirror our in vivo data, and suggest that induction of chondrocyte hypertrophy by FoxA2 may require other factors in addition to Runx2 (i.e., Hif2α, MEF2C, or perhaps unknown factors), whose expression/activity is rate-limiting in immature chondrocytes.

New Holocene grey whale (Eschrichtius robustus) material from North Carolina: the most complete North Atlantic grey whale skeleton to date.

Skeletal remains and historical accounts indicate that grey whales (Eschrichtius robustus) existed in the North Atlantic Ocean from the Pleistocene into the seventeenth century. Fossil and sub-fossil occurrences in this basin are rare, distributed from the east coast of the United States to Iceland and Europe. Here, we report an incomplete skeleton of a Holocene grey whale from Pender County, North Carolina, USA. This specimen represents a physically immature individual and is the most complete North Atlantic grey whale specimen reported to date. It comprises 42 cranial and postcranial elements, including the cranium, parts of the rostrum, both mandibles, both scapulae, humeri, radii and ulnae, most of the vertebral column anterior to the lumbar region and numerous ribs. Its provenance near the inlet of a large estuary is consistent with previous findings from the southeastern USA and parallels the species' habitat use in Baja California breeding and calving grounds in the North Pacific Ocean. Radiocarbon dating indicates an age of 827 ± 172 years before present. Cut marks on multiple skeletal elements indicate that the animal was butchered, suggesting some level of human exploitation of the species in the southeastern USA in the twelfth century, approximately 500 years prior to its extirpation in the North Atlantic.

A Baseline for Skeletal Investigations in Medaka (Oryzias latipes): The Effects of Rearing Density on the Postcranial Phenotype.

Oryzias latipes is increasingly used as a model in biomedical skeletal research. The standard approach is to generate genetic variants with particular skeletal phenotypes which resemble skeletal diseases in humans. The proper diagnosis of skeletal variation is key for this type of research. However, even laboratory rearing conditions can alter skeletal phenotypes. The subject of this study is the link between skeletal phenotypes and rearing conditions. Thus, wildtype medaka were reared from hatching to an early juvenile stage at low (LD: 5 individuals/L), medium (MD: 15 individuals/L), and high (HD: 45 individuals/L) densities. The objectives of the study are: (I) provide a comprehensive overview of the postcranial skeletal elements in medaka; (II) evaluate the effects of rearing density on specific meristic counts and on the variability in type and incidence of skeletal anomalies; (III) define the best laboratory settings to obtain a skeletal reference for a sound evaluation of future experimental conditions; (IV) contribute to elucidating the structural and cellular changes related to the onset of skeletal anomalies. The results from this study reveal that rearing densities greater than 5 medaka/L reduce the animals’ growth. This reduction is related to decreased mineralization of dermal (fin rays) and perichondral (fin supporting elements) bone. Furthermore, high density increases anomalies affecting the caudal fin endoskeleton and dermal rays, and the preural vertebral centra. A series of static observations on Alizarin red S whole mount-stained preural fusions provide insights into the etiology of centra fusion. The fusion of preural centra involves the ectopic formation of bony bridges over the intact intervertebral ligament. An apparent consequence is the degradation of the intervertebral ligaments and the remodeling and reshaping of the fused vertebral centra into a biconoid-shaped centrum. From this study it can be concluded that it is paramount to take into account the rearing conditions, natural variability, skeletal phenotypic plasticity, and the genetic background along with species-specific peculiarities when screening for skeletal phenotypes of mutant or wildtype medaka.

Educational impact of a novel cleft palate surgical simulator: Improvement in surgical trainees’ knowledge and confidence

Trainees' experience in cleft surgery is limited due to the high-risk nature of the surgery and centralization of cleft care. Simulation training allows trainees to learn complex surgical tasks whilst ensuring patient safety. Existing cleft surgical simulators are over-simplified or prohibitively expensive. In this article, we show the development and application of a high-fidelity yet cost-effective simulator for cleft palate repair. Skeletal elements were obtained through high-resolution scanning of a pathologic specimen, 3-dimensional printed, and then molded in plastic. Soft tissue components were formed through molding layers of silicone. The simulator was tested by 26 United Kingdom (UK) specialty trainees who performed a vomerine mucosal flap and intra-velar veloplasty in a 1-hour workshop. Pre- and post-simulation questionnaires assessing cleft knowledge and surgical confidence were compared for statistical significance. The simulator had high acceptability: 23/26 participants confirmed that the simulation training was a valuable learning experience. Baseline experience of cleft palate surgery was low: 24 participants had never performed any part of the procedure before. Following the workshop, mean knowledge score increased by 38%, and confidence by 53%. The paired T-test demonstrated that observed improvements in both knowledge and confidence were statistically significant (p<0.001). Simulation training is increasingly recognized as a crucial component of improving patient safety. Our new cost-effective cleft palate simulator has high acceptability and is a powerful educational tool that is effective in improving cleft palate surgical knowledge and confidence across all grades of surgical trainees.

Combining collagen extraction with mineral Zn isotope analyses from a single sample for robust palaeoecological investigations

Collagen extraction from bones or dentine, commonly used for radiocarbon (14C) dating and stable carbon and nitrogen isotope (δ13C and δ15N) analyses, involves the dissolution of the bioapatite of skeletal elements. This fraction is typically disposed of during pretreatment. Here, we test the possibility of utilising this dissolved mineral solution for analysis of the bioapatite zinc isotope composition (δ66Zn). Bioapatite δ66Zn is a novel trophic level indicator similar to collagen δ15N but with isotopic fractionation independent from nitrogen, thus providing additional dietary information. We tested ways to minimise Zn contamination of the dissolved mineral phase during collagen extraction. We then used archaeological bone samples from Ain Difla (Jordan) and Ranis (Germany) to compare δ66Zn values of dissolved bioapatite following our collagen extraction protocol with δ66Zn values from the same sample material dissolved in a metal-free cleanroom. Our results demonstrate that with only minor adjustments to minimise Zn contamination, the dissolved mineral solution from collagen extraction protocols commonly employed for 14C dating and (palaeo)dietary analysis can be used for additional δ66Zn analyses even when collagen extraction does not take place in a cleanroom. Our protocol allows us to gain an additional dietary proxy to complement δ15N trophic level interpretations and perform more robust (palaeo)ecological investigations without further destructive sampling.

Comparison of DNA preservation between ribs and vertebrae.

The choice of skeletal element types and their intra-bone parts is important because of differences in DNA preservation, and this must be considered when sampling bones for DNA testing. When incomplete skeletons are found, ribs and vertebrae have been shown to be the most suitable for genetic identification of bones from the torso. This study compares the preservation of DNA between 12th thoracic vertebrae and first ribs to determine which bone type is more suitable for genetic typing. The study analyzed 35 12th thoracic vertebrae and 29 first ribs from one mass grave from the Second World War with commingled skeletal remains excavated. Bone DNA preservation was estimated by measuring nuclear DNA concentration and its degradation and through short tandem repeat (STR) typing success. Previous studies performed on aged skeletal remains have shown that the DNA content of the first ribs and 12th thoracic vertebrae has high intra-bone variability, and this was considered when sampling the bones. After full demineralization extraction, the PowerQuant System (Promega) was used to measure the quantity and quality of DNA, and the GlobalFiler kit (Applied Biosystems) was used for STR typing. The results showed that DNA yield and degradation and STR typing success exhibited no statistically significant difference between first ribs and 12th thoracic vertebrae, and there was no intra-individual difference when comparing only paired bones from the same individuals. Consequently, with intra-bone DNA variability considered, the first ribs or the 12th thoracic vertebrae can be selected when sampling to genetically identify the skeletal remains of highly degraded torsos. HIGHLIGHTS: The first ribs and thoracic vertebrae are the most suitable bones for sampling from the torso. The proximal part of first rib and posterior vertebral column of the 12th thoracic vertebrae yielded the most DNA. The first ribs were compared with the 12th thoracic vertebrae, and the sampling process considered intra-bone DNA variability. The quality and quantity of nuclear DNA and success of STR typing were measured. The first ribs yielded the same DNA yields as well as STR typing success as the 12th thoracic vertebrae. When only the torso is present, it is not of high importance whether the first ribs or the 12th thoracic vertebrae are collected.

Fibronectin and Integrin α5 play overlapping and independent roles in regulating the development of pharyngeal endoderm and cartilage

Craniofacial skeletal elements are derived from cranial neural crest cells (CNCCs), which migrate along discrete paths and populate distinct pharyngeal arches, structures that are separated by the neighboring endodermal pouches (EPs). Interactions between the CNCCs and the endoderm are critical for proper craniofacial development. In zebrafish, integrin α5 (Itga5) functions in the endoderm to regulate formation of specifically the first EP (EP1) and the development of the hyoid cartilage. Here we show that fibronectin (Fn), a major component of the extracellular matrix (ECM), is also required for these developmental processes, and that the penetrance of defects in mutants is temperature-dependent. fn1a−/− embryos exhibited defects that are similar to, but much more severe than, those of itga5−/− embryos, and a loss of integrin av (itgav) function enhanced both endoderm and cartilage defects in itga5−/− embryos, suggesting that Itga5 and Itgav cooperate to transmit signals from Fn to regulate the development of endoderm and cartilage. Whereas the endodermal defects in itga5; itga5v−/− double mutant embryos were comparable to those of fn1a−/− mutants, the cartilage defects were much milder. Furthermore, Fn assembly was detected in migrating CNCCs, and the epithelial organization and differentiation of CNCC-derived arches were impaired in fn1a−/− embryos, indicating that Fn1 exerts functions in arch development that are independent of Itga5 and Itgav. Additionally, reduction of itga5 function in fn1a−/− embryos led to profound defects in body axis elongation, as well as in endoderm and cartilage formation, suggesting that other ECM proteins signal through Itga5 to regulate development of the endoderm and cartilage. Thus, our studies reveal that Fn1a and Itga5 have both overlapping and independent functions in regulating development of the pharyngeal endoderm and cartilage.

Distinct proliferative and middle ear skeletal-patterning functions for SHH-expressing epithelia in the chick hyoid arch

During chick craniofacial development, the second (hyoid) pharyngeal arch expands to close the neck and gives rise to skeletal elements, including the columella of the middle ear (a homologue of the mammalian stapes). Sonic hedgehog (SHH) signalling has been implicated in hyoid arch expansion and columella formation, but spatial and temporal aspects of these signalling interactions within the hyoid arch remain poorly understood. Here, we show that SHH is initially expressed in the posterior endoderm of the hyoid arch, and that this domain subsequently splits into a distal domain at the site of arch expansion (the posterior epithelial margin, PEM), and a proximal domain that lines the foregut (the proximal hyoid epithelium, PHE). Pharmacological manipulations and heterotopic grafting experiments demonstrate that SHH signalling is required for hyoid arch expansion and skeletogenesis, and reveal distinct roles for the PEM and PHE in these processes. The PEM promotes mesenchymal cell proliferation during arch expansion but is not sufficient to repattern the columella. Conversely, the PHE promotes mesenchymal cell survival, and PHE grafts induce partial duplication of the columella. This work demonstrates crucial and distinct roles for endodermal SHH signalling in hyoid arch morphogenesis and patterning of the middle ear skeleton.

Bone pathologies of modern caprines (Ovis aries &Capra hircus) in the context of the pasture-stall system of the steppe zone of the South Urals

ObjectivesVarious dentition and bone pathologies of the postcranial skeleton of caprines are regularly mentioned in archaeozoological studies. This work analyzes pathological and age-related changes in modern animals with known life histories in order to improve the accuracy of interpretation of pathologies of caprines from archaeological sites. Materials1468 bones of modern caprines (mainly sheep) have been analyzed. The bones originate from the territory in which there are numerous settlements of Bronze Age pastoralists. MethodsBones of modern caprines with pathologies have been compared with bones without changes. The age of the animals was determined by the state of the dental system and epiphyses, which made it possible to determine the approximate age range of the caprines, the bones of which are analyzed in the work. ResultsFor each skeletal element of modern caprines, typical kinds of changes have been revealed. In some cases, a correlation has been established between the number of pathological changes and the age of livestock. ConclusionDespite the known life histories of sheep and goats, the etiology of a number of identified changes remains unknown. Most of the recorded pathologies are typical for caprines and are difficult to use for the reconstruction of the nature of animal husbandry practices. SignificanceThis work analyzes a relatively extensive collection of bones of caprines with known life histories. It will allow the identification of typical bone pathologies in sheep and goats and their approximate etiology within a given breeding system and area. These data can be used in the framework of archaeozoological studies of the steppe zone of northern Eurasia and other territories. LimitationsThis research is limited to a relatively small number of bones and complete skeletons of modern caprines, alongside the near absence of complete skeletons of modern wild ungulates from the same microdistrict. Future researchThe most promising area of future work is a combined comparative study of a larger sample of bones of modern and Bronze Age caprines and wild ungulates of the same size class. It will allow changes to be identified directly related to animal husbandry practices.

Fgf8 dosage regulates jaw shape and symmetry through pharyngeal-cardiac tissue relationships.

Asymmetries in craniofacial anomalies are commonly observed. In the facial skeleton, the left side is more commonly and/or severely affected than the right. Such asymmetries complicate treatment options. Mechanisms underlying variation in disease severity between individuals as well as within individuals (asymmetries) are still relatively unknown. Developmental reductions in fibroblast growth factor 8 (Fgf8) have a dosage dependent effect on jaw size, shape, and symmetry. Further, Fgf8 mutants have directionally asymmetric jaws with the left side being more affected than the right. Defects in lower jaw development begin with disruption to Meckel's cartilage, which is discontinuous. All skeletal elements associated with the proximal condensation are dysmorphic, exemplified by a malformed and misoriented malleus. At later stages, Fgf8 mutants exhibit syngnathia, which falls into two broad categories: bony fusion of the maxillary and mandibular alveolar ridges and zygomatico-mandibular fusion. All of these morphological defects exhibit both inter- and intra-specimen variation. We hypothesize that these asymmetries are linked to heart development resulting in higher levels of Fgf8 on the right side of the face, which may buffer the right side to developmental perturbations. This mouse model may facilitate future investigations of mechanisms underlying human syngnathia and facial asymmetry.

Anatomy informs geology: Hydrodynamic dispersal of alligator bones, with implications for taphonomic interpretations of fossil deposits of crocodylians, dinosaurs, and other morphologically novel taxa.

Distinctive anatomical features of bones can influence not only how these structures perform in living animals but also the tendency of elements to be transported by flowing water after death. Such transport can be critical in the concentration of fossils from animals that live near freshwater habitats, providing important context for interpreting the composition of paleocommunities. Measurements of the tendency of flowing water to disperse skeletal elements have been collected for diverse taxa, including mammals, turtles, and birds. However, these extant models may not be entirely appropriate for many morphologically distinct extinct lineages, such as non-avian dinosaurs. To expand the range of models available for evaluating the influence of hydrodynamic transport on the assembly of fossil deposits, we used a flow tank to measure the water speeds that disperse bones from a subadult American alligator (Alligator mississippiensis), with the skull and mandible tested in multiple starting orientations. Alligator bones are sorted into three main dispersal groups: early (vertebrae, most girdle elements), intermediate (ribs, most limb bones), and late (pubis, femur), with the skull and mandible varying between intermediate and late depending on orientation. Late dispersing elements tended to be heavy or very flat. These results can refine interpretations of the taphonomic context for deposits of fossil crocodylians and morphologically similar taxa (e.g., choristoderes, phytosaurs) and provide an additional comparative model for deposits of non-avian dinosaurs. Moreover, variation in hydrodynamic sorting across lineages highlights how distinctive anatomical features can influence the concentration of fossils, shaping understanding of assemblage composition and paleofaunal evolution.