Anatomical Record-Advances in Integrative Anatomy and Evolutionary Biology最新文献

This research delves deeper into previous works on femoral cross-sectional properties during ontogeny by focusing for the first time on the human femoral midneck. The ontogenetic pattern of cross-sectional properties at femoral midneck is established and compared with those at three different femoral locations: the proximal femur, the midshaft, and the distal femur. The study sample includes 99 femora (70 non-adults and 29 adults) belonging to archaeological specimens. Cross-sectional properties were extracted from computed tomographic scans and analyzed with the MomentMacro plugin of ImageJ. Ontogenetic trends of these variables were assessed using locally estimated scatterplot smoothing and segmented regressions, along with Wilcoxon post hoc tests for all possible age group pairings. Our results show that the femoral midneck exhibits a unique growth pattern. Area variables showed rapid growth until adolescence, followed by a more gradual increase leading into adulthood. Nonetheless, the relative cortical area does not demonstrate any significant drops or rise during growth. The morphology of the midneck section of the femur remains stable during ontogeny, with early adolescence and the onset of adulthood marking two periods of significant change. In contrast to the femoral diaphysis, the acquisition of a mature bipedal gait does not appear to constitute a period of significant morphological change at the femoral midneck cross section.

Chameleons are a family of lizards distinguished by several unique features related to their arboreal lifestyles, such as a ballistic tongue, skin color changes, independent movement of both eyes, a prehensile tail, and cleft hands and feet. The veiled chameleon (Chamaeleo calyptratus) has been proposed as a promising model species for studying squamate biology. Despite its potential, the developmental biology of this species remains poorly understood, particularly in terms of gonadal development. This study aimed to elucidate the development of the gonads in the veiled chameleon, from the initial appearance of the gonadal ridges through the sexual differentiation into ovaries and testes, to the establishment of the gonadal structures in both sexes. The study showed the accelerated appearance of gonadal primordia compared to the soma in the veiled chameleon, which is unique and possibly influenced by a prolonged in ovo development period due to the slowed rate of embryonic development in this species. The undifferentiated gonads are characterized by a voluminous medulla and a thin cortex. The process of gonadal sexual differentiation mirrors that seen in other vertebrates. Ovarian differentiation involves the development of a cortex containing germ cells and the loss of these cells in the medulla. Differentiated ovaries are characterized by a thin cortex and early induction of meiosis, leading to the formation of ovarian follicles before hatching. In contrast, testis differentiation involves the loss of germ cells from the cortex, its transformation into a thin epithelium, and the development of germ cell-containing testis cords in the medulla. The testis cords originate from invagination and remain without forming a lumen during embryogenesis. This comprehensive examination of gonadal development in the veiled chameleon provides important insights into sexual differentiation processes in this species. Moreover, it may stimulate further, broader studies in vertebrate developmental biology.

Pseudosuchia, one of the two main clades of Archosauria, is today only represented by some 20 extant species, the crocodilians, representing only a fraction of its extinct diversity. Extant crocodilians are ectotherms but present morphological and anatomical features usually associated with endothermy. In 2004, it was proposed that pseudosuchians were ancestrally endothermic and the features observed in extant crocodilians are the remains of this lost legacy. This contribution has two parts: the first part covers 20 years of studies on this subject, first exploring the evidence for a loss of endothermy in extant crocodilians, before covering the variety of proxies used to infer the thermophymetabolic regime of extinct pseudosuchians. In the second part, the quantitative results of these previous studies are integrated into a comprehensive ancestral state reconstruction to discuss a potential scenario for the evolution of thermometabolism. Pseudosuchian endothermy would then have been lost close to the node Crocodylomorpha. The end-Triassic mass extinction is proposed to have played the role of a filter, leading to the extinction of endothermic pseudosuchians and the survival of ectothermic ones. This difference in survival in Pseudosuchia is compared to those of dinosaurs, and difference in their metabolism is also considered. Pseudosuchian endothermy might have been of a different level than the dinosaurian one and more studies are expected to clarify this question.

Xenodens calminechari is a mosasaurid taxon named by Longrich et al. (2021) based on the holotype MHNM.KH.331, a left maxilla with several teeth. This holotype was obtained nonscientifically (without technical supervision) from an area in Morocco that yields many manipulated or forged specimens. Examination of Longrich et al. (2021) reveals four tooth crowns occupy what appear to be two alveoli in MHNM.KH.331, and there is potential adhesive connecting the tooth crowns to the maxilla on their lateral sides. We argue that the articulated tooth crowns of this taxon were artificially placed in the maxilla, rendering at least two apomorphies of this taxon the product of forgery. Longrich et al. (2021)'s claims of fused tooth ‘roots' in MNHM.KH.331 are instead calcified periodontal ligament and alveolar bone that have ankylosed, resembling the typical mosasaurid condition. Differing tooth crown morphology does not preclude the referral of the teeth of this specimen to a younger ontogenetic stage of another mosasaur (possibly Carinodens) because many extant lizard species show drastic ontogenetic changes in the dentition. We argue that Xenodens calminechari represents a nomen dubium. This specimen constitutes a confluence of two persistent problems in vertebrate paleontology: material sourced from commercial excavations that has not been adequately tested for forgery, and taxa named from tooth-based holotypes that ignore the potential for intraspecific dental variation and interspecific convergence in dental characters, as are common in squamates. We suggest that Longrich et al. CT scan MHNM.KH.331, and we supply CT examples for identifying artificially added tooth crowns to Moroccan mosasaur jaws. Finally, we provide recommendations for the designation of mosasaurid holotypes.

In the context of an increasing interest for Pseudosuchia, we have compiled a Special Issue, comprising 14 collaborative studies that deepen our understanding of pseudosuchian evolution. These contributions range from the description of a new taxon to exhaustive reviews of thermometabolism, morphological adaptation, systematics, and detailed investigations into ontogeny, paleoneurology, paleohistology, and paleobiology. Through these papers, we explore the evolutionary history of pseudosuchian archosaurs, spotlighting their rise and diversification following the end-Permian mass extinction.

Crocodylians evolved a unique gular valve that is capable of creating a water-tight seal between the oral and pharyngeal cavities, allowing the animal to safely submerge with an open mouth. The gular valve has traditionally been described as consisting of two separate parts: an active mobile ventral portion (consisting of the tongue and portions of the hyolingual apparatus) and a dorsal portion, which is a static fold on the hard palate (often termed the palatal velum). The results of the present study argue that the two portions of the gular valve are functionally integrated, not separate, and that the dorsal portion (herein the dorsal gular fold) is a dynamic element the shape and tension of which are influenced by active and passive forces. Using gross dissection, histology, and DiceCT, the present study documents a previously underscribed component of the gular valve, the velar chord, which links the hyolingual apparatus to the dorsal gular fold, functionally integrating the two halves of the gular valve. Through endoscopic videography and a variety of manipulations on living crocodylians, this study demonstrates that changes in the tension on the velar chord directly alter the shape and tension of the dorsal gular fold. The shape changes observed in the dorsal gular fold could be accommodated by a shallow depression in the ventral surface of the palatine bones, herein termed the velar fossa. The velar fossa is a prominent feature of Alligator mississippiensis and was observed in other crocodilians; however, a survey of living and fossil crocodylians demonstrated that the velar fossa is not a universal feature in this clade. Understanding the functional linkage between the dorsal and ventral portions of the gular valve has implications beyond the dive reflex of crocodylians, since active manipulation of the dorsal gular fold likely plays a role in a variety of behavioral and physiological processes such as deglutition and vocalization.

Understanding patterns of cortico-cortical connections in both frequently and infrequently studied species advances our knowledge of cortical organization and evolution. The agouti (Dasyprocta aguti, a medium-size South American rodent) offers a unique opportunity, because of its large lissencephalic brain and its natural behaviors, such as gnawing and hiding seeds, that require bimanual interaction while sitting on its hindlimbs and aligning its head to receive images of the horizon on the retinal visual streak. There have been no previous studies of the intrinsic and extrinsic ipsilateral projections of the agouti's primary somatosensory cortical area (S1). In the present study, we utilized biotinylated dextran (BDA) anatomical tract-tracer injections combined with microelectrode electrophysiological mapping, correlated with analysis of cytochrome oxidase (CO) histochemical staining, to investigate the ipsilateral corticocortical connectivity of the agouti's S1. By injecting BDA into electrophysiologically identified regions within the S1, we revealed ipsilateral intrinsic connections, as well as connections with cortical areas rostral and caudal to S1, and homotopic labeling in the second somatosensory cortical area (S2). In addition, we identified a focal cluster of labeled axons and axonal terminals adjacent to the rhinal fissure, tentatively named the parietal rhinal area (PR). The analysis of CO reactivity allowed delineation of the boundaries and subdivisions of S1, as well as the locations and limits of primary auditory and visual areas. These findings provide support for the notion of a similar pattern of somatosensory cortical organization and connectivity across mammalian species.

With nearly 30 living species of relatively similar ecological traits, Crocodylomorpha is represented today by only a small fraction of its past diversity. The well-documented crocodylomorph fossil record has revealed more than 500 taxa, with much higher ecological and morphological diversity than their extant counterparts. An example of such astonishing diversity is the Late Cretaceous rocks of the Bauru Group (southeast Brazil), from which numerous taxa are known, belonging to the clade Notosuchia. These were predominantly terrestrial taxa, some of which exhibited traits associated with omnivorous or even herbivorous feeding behaviors, such as Sphagesauridae, whereas others were adapted to a carnivore diet, such as Baurusuchidae and Peirosauridae. Among these is Barreirosuchus franciscoi, originally described as a neosuchian (Trematochampsidae) but later interpreted as a peirosaurid notosuchian. Even though included in recent morphological and phylogenetic analyses, B. franciscoi still lacked a more detailed description. Here, we provide an in-depth description of the cranial elements of B. franciscoi, using data from computed tomography and a broad sample of comparative material, including living and fossil crocodylomorphs. Also, the neuro-cavities, including the endocast, nasopharyngeal duct, and the olfactory region, were digitally reconstructed. Finally, a new phylogenetic analysis recovered B. franciscoi nested within Peirosauria, forming the Itasuchidae clade with other potentially semiaquatic species: Rukwasuchus yajabalajekundu, Pepesuchus deiseae, and Itasuchus jesuinoi. The morphological and phylogenetic reassessment of B. franciscoi indicates a semiaquatic form, highlighting the ecological diversity of notosuchians from the Bauru Group as well as the capacity of notosuchians to explore a myriad of environments.

Spatial relationships between oropharyngeal structures and their coordinated dynamics ensure proper adaptations in functions such as respiration, chewing, and swallowing. Thus, the aim of this study is to analyze spatial changes in the normal oropharynx during respiration and mastication. For this purpose, eight 7-8 months old Yucatan minipigs, four of each sex were used. X-ray fluoroscopy was recorded with the field of view focused on the oropharyngeal region. The x-ray video clips showing respiratory cycles and masticatory sequences were digitized and traced. Points to be digitized and traced were located on the soft palate, epiglottis, tongue base, and pharyngeal wall. An X-Y coordinate system was established to trace distances and directions of each structure (structural), and between structures (inter-structural) during phases of respiration, chewing stages, and swallowing episodes. During respiration, the soft palate showed the largest X-Y movements with the largest distance change (1.32 ± 0.64 mm). In contrast, distance changes in the tongue base were significantly smaller (0.32 ± 0.21 mm, p < 0.05). Notably, during chewing the tongue base and epiglottis showed major changes in distance and direction. Similarly, during swallowing the tongue base showed the largest changes (2.94 ± 1.28 mm) followed by the pharyngeal wall and epiglottis. Thus, although coordinated, each pharyngeal structure plays specific roles. Understanding of these spatial and specific dynamics in different oropharyngeal structures would provide the baseline to analyze the potential mechanisms of various swallowing and breathing disorders such as dysphagia and obstructive sleep apnea.

Crocodylomorphs constitute a clade of archosaurs that have thrived since the Mesozoic until today and have survived numerous major biological crises. Contrary to historic belief, their semiaquatic extant representatives (crocodylians) are not living fossils, and, during their evolutionary history, crocodylomorphs have evolved to live in a variety of environments. This review aims to summarize the non-semiaquatic adaptations (i.e., either terrestrial or fully aquatic) of different groups from different periods, highlighting how exactly those different lifestyles are inferred for those animals, with regard to their geographic and temporal distribution and phylogenetic relationships. The ancestral condition for Crocodylomorpha seems to have been a terrestrial lifestyle, linked with several morphological adaptations such as an altirostral skull, long limbs allowing a fully erect posture and a specialized dentition for diets based on land. However, some members of this clade, such as thalattosuchians and dyrosaurids display adaptations for an opposite, aquatic lifestyle, interestingly inferred from the same type of morphological observations. Finally, new techniques for inferring the paleobiology of those extinct animals have been put forward in the last decade, appearing as a complementary approach to traditional morphological descriptions and comparisons. Such is the case of paleoneuroanatomical (CT scan data), histological, and geochemical studies.