Journal of Anatomy最新文献

Notosuchia were a successful lineage of Crocodyliformes that achieved a remarkable diversity during the Cretaceous of Gondwana, particularly in South America. Although paleohistology has expanded our knowledge of the paleobiology of notosuchians, several clades of this lineage remain poorly understood in this aspect. Here we help to address this gap by conducting the first histological analysis of appendicular bones of a peirosaurid. To increase our knowledge about growth dynamics and examine intraeskeletal and interspecific histological variation, we analyze the microstructure of a tibia, fibula, phalanx, fragment of ornamented element (possible osteoderm or skull bone) and a possible long bone of an individual assigned to Peirosauridae indet. (MAU-Pv-437). The peirosaurid studied here appears to have reached sexual but not somatic maturity and the minimum age inferred from appendicular bones results in a lower estimated than the age inferred from osteoderms in a previous study on the same individual. The cortical bone in MAU-Pv 437 is formed by vascularized parallel fibered bone/lamellar bone which indicates that this individual experienced a moderate growth rate. This indicates different growth dynamics from what has been observed for other notosuchians specimens, suggesting a lack of a uniform growth pattern for this clade.

The small-sized cervid Procervulus is considered as the most basal member of the Cervidae and one of the earliest ruminants bearing antler-like appendages. The Iberian Miocene record of this stem-cervid is extensively documented and largely overlaps with the Miocene Climatic Optimum (MCO), a transient period of global warming of particular interest when comparing present and near future conditions. Despite receiving a substantial amount of attention, histological studies on Procervulus are very scarce and only limited to postcranial remains of Procervulus praelucidus from Germany (MN3). Here we focus for the first time on the dental histology of Procervulus ginsburgi from the Early Miocene Iberian site of Artesilla (MN4, 16.49 Ma), and examine its daily enamel secretion rate (DSR), enamel extension rate (EER) and crown formation time (CFT). Results reveal a brief CTF and high DSR and EER for P. ginsburgi and suggest a fast development at least early in its ontogeny. In addition, the pronounced growth rate of P. ginsburgi emerges as higher than that of the roe deer C. capreolus-documented as an r-strategist and here examined as a possible extant analog. Overall, our findings point toward a fast life history strategy for P. ginsburgi, which unexpectedly contrasts with that of the 2 million-year-older P. praelucidus from Wintershof-West, with a marked slower growth and maturation. When these results are analyzed together with other evidence, the somewhat drier and more open conditions of Artesilla as a result of the effects of the MCO seem to be the explanation for the different life history and ecology between these Procervulus species. More generally, this study illustrates that life histories within a single genus evolve in response not only to internal constraints but also to the environments, as predicted by the Life History Theory.

The fibula, despite being traditionally overlooked compared to the femur and the tibia, has recently received attention in primate functional morphology due to its correlation with the degree of arboreality (DOA). Highlighting further fibular features that are associated with arboreal habits would be key to improving palaeobiological inferences in fossil specimens. Here we present the first investigation on the trabecular bone structure of the primate fibula, focusing on the distal epiphysis, across a vast array of species. We collected μCT data on the distal fibula for 21 species of primates, with representatives from most of the orders, and we employed a recently developed approach implemented in the R package 'indianaBones' to isolate the entire trabecular bone underlying an epiphysis or articular facet. After extracting both traditional trabecular parameters and novel topological indices, we tested for the posited relationship between trabecular bone and DOA. To disentangle this effect from others related to body size and phylogenetic relationship, we included a body mass proxy as covariate and employed phylogenetic comparative methods. We ran univariate/multivariate and exploratory/inferential statistical analyses. The trabecular structure of the fibular distal epiphysis in primates does not appear to be associated with the DOA. Instead, it is strongly affected by body mass and phylogenetic relationships. Although we identified some minor trends related to human bipedalism, our findings overall discourage, at this stage, the study of distal fibula trabecular bone to infer arboreal behaviors in extinct primates. We further found that body size distribution is strongly related to phylogeny, an issue preventing us from unravelling the influence of the two factors and that we believe can potentially affect future comparative analyses of primates. Overall, our results add to previous evidence of how trabecular traits show variable correlation with locomotor aspects, size and phylogenetic history across the primate skeleton, thus outlining a complex scenario in which a network of interconnected factors affects the morphological evolution of primates. This work may represent a starting point for future studies, for example, focusing on the effect of human bipedalism on distal fibula trabecular bone, or aiming to better understand the effects of body size and phylogenetic history on primate morphological evolution.

Studies of modeling processes have provided important insights in human evolutionary discipline. Most of these studies are based on facial bones and in much lesser extent on other bones such as those from the cranial vault. Thus, this study fills a gap in research by examining occipital bone modeling in subadults, adding individuals under 2 years old and expanding the sample size available to date. The sample comprise 14 subadults occipitals (4 months to 5 years) from archeological sites spanning the thirteenth to the eighteenth century. Resin replicas coated with gold were elaborated to examine the modeling patterns using scanning electron microscopy and the results of this analysis are illustrated in the modeling maps. The percentages of deposition and resorption were calculated to enable the comparison of the modeling patterns between individuals. The analysis unveiled a pattern of resorption predominance in younger individuals, shifting to deposition around 3 years old before reverting to resorption in older individuals. Symmetry in modeling processes between left and right halves of the occipital was observed, suggesting stability in bone modeling. Comparisons with previous studies showed variations in modeling patterns influenced by factors like age. Overall, this study sheds light on occipital bone modeling processes, highlighting the importance of sample size and quantitative analysis in the interpretation of modeling maps. Further research is justified to comprehensively explore occipital modeling patterns, particularly during the early stages of development.

24 January 2025: This paper was inadvertently published prematurely before all proof corrections had been finalized. It has been temporarily unpublished while this is rectified.

Anatomical knowledge is fundamental for all species. In particular, myology allows a deeper understanding of ecomorphology-especially for those species hard to observe in the wild-and may be an important source for phylogenetic information. In this study, we analyzed the myological variation of the musculature of the shoulder and arm of the forelimb in species of the suborder Feliformia and its relationship with the phylogenetic history and the locomotor behavior, habitat, and predatory habits of the species within this group, using Leopardus geoffroyi as a case study. We used gross-anatomy dissections of the shoulder and arm of three specimens of L. geoffroyi and contrasted these results to other previously described feliform species. Additionally, we optimized 15 myological characters to search for phylogenetic patterns. We present the first description and the first complete muscular maps of the forelimb shoulder and upper arm of L. geoffroyi. A small number of muscular characteristics allow L. geoffroyi to be distinguished from other feliforms, such as a possible partial division of m. biceps brachii, although they did not relate to any analyzed ecological habit. Some myological characteristics studied in this work contribute to the knowledge of the phylogenetic relationships and the morphological evolution of Feliformia. Felids are the only feliforms with a constantly present m. pectoantebrachialis (although it has been reported in some caniforms). Muscle rhomboideus capitis is present only in Felidae and Herpestidae, resembling various caniforms. Its presence could indicate a retention linked to their carnivoran ancestry. The Felidae and Hyaenidae represent two quite conservative morphotypes, as they present particular muscular configurations compared to other feliform families, but also, relatively little variation within each family. Functionally, some myological characters recorded in hyenids, L. lynx, P. uncia, A. jubatus (e.g., radio-ulnar insertion of m. biceps brachii), distinguish them from the rest of the species of the same suborder or family, and are convergent with other carnivorans with cursorial habits (e.g., canids). The functional and evolutionary analysis of the myology of the forelimb of L. geoffroyi and the different species of the suborder Feliformia allowed a better understanding of how muscle configurations reflect functional specialization to different ways of life. The muscle maps presented here, being the first available for a small Neotropical felid, can be considered a valuable source of information, useful for future studies of comparative anatomy in neontological and paleobiological contexts.

Anterior-posterior (A-P) elongation of the palate is a critical aspect of integrated midfacial morphogenesis. Reciprocal epithelial-mesenchymal interactions drive secondary palate elongation that is coupled to the periodic formation of signaling centers within the rugae growth zone (RGZ). However, the relationship between RGZ-driven morphogenetic processes, the differentiative dynamics of underlying palatal bone mesenchymal precursors, and the segmental organization of the upper jaw has remained enigmatic. A detailed ontogenetic study of these relationships is important because palatal segment growth is a critical aspect of normal midfacial growth, can produce dysmorphology when altered, and is a likely basis for evolutionary differences in upper jaw morphology. We completed a combined whole mount gene expression and morphometric analysis of normal murine palatal segment growth dynamics and resulting upper jaw morphology. Our results demonstrated that the first formed palatal ruga (ruga 1), found just posterior to the RGZ, maintained an association with important nasal, neurovascular and palatal structures throughout early midfacial development. This suggested that these features are positioned at a proximal source of embryonic midfacial directional growth. Our detailed characterization of midfacial morphogenesis revealed a one-to-one relationship between palatal segments and upper jaw bones during the earliest stages of palatal elongation. Growth of the maxillary anlage within the anterior secondary palate is uniquely coupled to RGZ-driven morphogenesis. This may help drive the unequaled proportional elongation of the anterior secondary palate segment prior to palatal shelf fusion. Our results also demonstrated that the future maxillary-palatine suture, approximated by the position of ruga 1 and consistently associated with the palatine anlage, formed predominantly via the posterior differentiation of the maxilla within the expanding anterior secondary palate. Our ontogenetic analysis provides a novel and detailed picture of the earliest spatiotemporal dynamics of intramembranous midfacial skeletal specification and differentiation within the context of the surrounding palatal segment A-P elongation and associated rugae formation.

Obesity, along with hypoxia, is known to be a risk factor for pulmonary hypertension (PH), which can lead to right ventricular hypertrophy and eventually heart failure. Both obesity and PH influence the autonomic nervous system (ANS), potentially aggravating changes in the right ventricle (RV). This study investigates the combined effects of obesity and hypoxia on the autonomic innervation of the RV in a mouse model. Male C57BL/6N mice were subjected to a control diet (CD) or a high-fat diet (HFD) for 30 weeks, with subsets of the mice exposed to chronic normobaric hypoxia (13% O₂) during the final 3 weeks. Light and electron microscopic stereology was used to quantify various parameters of nerve fibres innervating the RV myocardium. HFD-induced obesity significantly increased the total length of nerve fibres and axons in the RV under normoxic conditions, indicating hyperinnervation. Quantitatively, the length density of nerve fibres per unit volume of RV (unit: x10^-3 µm^-2) was similar in CD (0.158 ± 0.04), CD-Hyp (0.176 ± 0.06) and HFD-Hyp (0.147 ± 0.05). In contrast, in HFD the length density of nerve fibres showed higher values 0.206 ± 0.054. The total length of nerve fibres increased by 67% from 2.61 m ± 0.77 m in CD to 4.37 m ± 1.51 m in HFD. The total length of axons increased by 80% from 8.87 m ± 2.75 m to 15.95 m ± 4.62 m. However, when obesity was combined with hypoxia, the total axon length was significantly reduced by 27% in HFD-Hyp compared with HFD. In addition, the mean number of axon profiles per nerve fibre profile decreased from 3.44 ± 0.68 in HFD to 2.95 ± 0.43 in HFD-Hyp. Interestingly, chronic hypoxia alone did not significantly alter RV innervation but led to RV hypertrophy, independent of the diet. The attenuation of obesity-induced hyperinnervation by hypoxia suggests a complex and potentially antagonistic interaction between these conditions. In conclusion, obesity induced by a HFD caused hyperinnervation of the RV, whereas chronic hypoxia alone did not significantly alter RV innervation. Surprisingly, chronic hypoxia attenuated the obesity-induced changes in RV innervation. These findings indicate that the effects of obesity and hypoxia-induced PH on RV innervation are distinct and potentially antagonistic.

According to the World Health Organization (WHO) musculoskeletal conditions are a leading contributor to disability worldwide. This fact is often somewhat overlooked, since musculoskeletal conditions are less likely to be associated with mortality. Nonetheless, treatments, therapies and management of these conditions are extremely costly to national healthcare systems. As with all systemic conditions, biomedical imaging of relevant tissues plays a major role in understanding the fundamental biological processes involved in musculoskeletal health. However, the skeletal system with its relatively large proportion of dense, opaque (often mineralised) tissues can often be more challenging to image, and recently important advances have been made in imaging these complex musculoskeletal tissues. Thus, we here describe a novel workflow in which recent advanced imaging techniques have been modified and optimised for use in musculoskeletal tissues (specifically bone and cartilage). This will allow for investigations, of different phases of these tissues, at new and higher resolutions. Furthermore, the process has been designed to fit with the existing and standard processes which are typically used with these samples (i.e. μCT imaging and standard histology). The additional modalities which have been included here are second harmonic generation (SHG) imaging, tissue clearing, specifically the Passive Clear Lipid-exchanged Acrylamide-hybridised Rigid Imaging Tissue hYdrogel (CLARITY) method known as PACT, and then imaging of these tissues with confocal, multiphoton and light-sheet microscopy. This paper serves to introduce a combination of existing new methods and improvements in imaging of musculoskeletal tissues.

Current understanding of the histology of the dermoskeleton of tetrapods comes from fossilized and recent remains of skulls, osteoderms, carapace, plastron and other postcranial material which were always investigated using linear cross polarized light (LCPL) microscopy. The pectoral girdle of vast majority of non-amniote tetrapods, including temnospondyls evolved large ventrally located dermal bones- the interclavicle and a pair of clavicles. Despite that, there is a lack of information about the bone tissue structure from these postcranial dermal bones. This study used circular cross polarized light (CCPL) to investigate the bone tissue composition and structure from the pectoral dermoskeleton of Metoposaurus krasiejowensis, a Late Triassic temnospondyl known to have evolved massive pectoral dermal bones which could have played a role in buoyancy control in these aquatic amphibians. This novel technique shines light into the fine structure of interwoven structural fibers (ISF), a common matrix found in ossified dermal tissues, is a mesh of loops and strands of collagen instead of a lattice patterned matrix as described previously by using LCPL in previous studies that dealt with ossified elements of dermal origin. Our result of ISF is achieved by eliminating bone fiber extinction under CCPL visualization. This feature of CCPL also sheds light into the transitional forms between interwoven and parallel-fibered matrices which was never previously observed. This study shows that the historical understanding of histology of bone tissue from skeletal dermal elements is limited not only due to lack of sampling but also due to the limitations of mineralized tissue visualization with LCPL.