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

The impact of artificial selection on the masticatory apparatus of dogs has been poorly studied, and comparative data with dogs subjected to more natural constraints are lacking. This study explores the jaw musculature of Tunisian street dogs, which are largely free from the influence of breed-specific selection. The masticatory muscles (digastric, masseter, temporalis, and pterygoid) of 27 adult dogs were dissected and muscle mass and physiological cross-sectional area (PCSA) were quantified, providing a baseline for comparisons between dogs from more natural versus more controlled environments. Our findings reveal that the morphology of the jaw adductor muscles is remarkably conserved among dogs, despite significant variation in skull shape. Additionally, all masticatory muscles scale isometrically with body mass. Notably, females exhibit functional adaptations that optimize muscle strength, particularly in the temporalis muscle, despite showing smaller overall muscle volumes compared to males. This could be linked to differences in predation, competition for food, or factors related to sexual behavior. Preliminary evidence suggests that captivity may limit the development of muscle mass and PCSA in the temporalis muscle, likely due to changes in lifestyle and diet. Significant relationships were also observed between skull shape and muscle data, particularly in the mandible, indicating that skull variability reflects jaw adductor muscle anatomy to some degree. This study enhances our understanding of jaw muscle morphology and function in feral dog populations and offers insights into the adaptation of the masticatory apparatus in dogs.

We aimed to determine the timing of appearance and the morphologic and morphometric features of the initial human cerebral sulcal formation. Using high-resolution magnetic resonance images obtained from 33 samples between 11 and 16 weeks (w) of gestation (crown-rump length <130 mm), the cerebral surface and internal structures on serial two-dimensional planes and all possible sulci on three-dimensional reconstructions were marked, allowing comparison of the positions of the sulci in the samples and inter-samples. Our method provided accurate conclusions regarding the timing of sulcal formation. Detection timing was as early as and earlier than those in previous studies using anatomical dissection and magnetic resonance imaging (MRI), respectively: <12 w for the callosum, <13 w for the hippocampal, calcarine, and parieto-occipital sulci, and < 15 w for the lateral sulcus. Occasionally, an olfactory sulcus was detected. However, the cingulate sulcus could not be definitely identified. The lateral sulcus gradually appeared and changed shape. The lengths of the left and right sides of the olfactory sulci and the left side of the hippocampal sulcus increased linearly with the CRL. The length of the right side of the hippocampal sulcus and the left and right sides of the calcarine, parieto-occipital, and not determined_a sulci did not increase with the CRL The depth of the all sulci, except for the parieto-occipital sulci, increased linearly with the CRL. The sulci might not arise as if they elongate gradually but arise simultaneously over some distance. We determined the timing of the initial sulcal formation using high-resolution MRI. Our findings may significantly impact prenatal diagnosis and research on neurodevelopmental disorders.

Although the reproduction of some Boidae snakes has been studied through the macroscopic anatomy of the gonads, without microscopic morphology, there is little precision in describing reproductive cycles, especially for males. The relationship between the reproductive cycle-gametogenesis and reproductive seasonality throughout the year-has yet to be detailed for many Boidae species. We present macroscopic and histological data on the reproductive tracts of both male and viviparous female Corallus hortulana (Linnaeus 1758) (Amazon Tree Boa) from the Brazilian Amazon rainforest. Males present spermiogenesis and spermiation mainly during January and June (wet season to beginning-dry season). Contrary to common assumption, we speculate that sperm production in C. hortulana, even in the tropical Amazon, is likely energetically demanding, influenced by rainfall, given that testicular involution occurred between May and November (most of the driest months of the year). Females present ovarian follicles in processes of vitellogenesis from December to August (wet season and part of the dry season). However, newborns are found in the wild mainly in the wet season, characterizing the cycle of female C. hortulana as seasonal. Unprecedentedly, we present the first microscopic description of the pouch and non-glandular uterus in a Boidae species. The cells that compose the epithelial tissue of the non-glandular uterus have been suggested for maintaining and supporting spermatozoa (sperm storage) in snakes, but we found no evidence that sperm storage occurs in this portion of the oviduct in C. hortulana. This study not only improves our understanding of reproductive biology in a boid, but because several aspects of reproductive cycles are conservative in the family (e.g., season of birth of newborn snakes), it aids in the development of effective conservation policies for endangered species such as Corallus cropanii, the rarest Boidae in the Americas.

In January 2021, Kurt Albertine, PhD, stepped down as the Editor of The Anatomical Record after 15 years of dedicated service. As Editor-In-Chief, he oversaw incredible growth, expanded scope, and increased impact of the journal. At the same time, he directed an active research lab in neonatal pulmonary biology at the University of Utah, with an exceptional track record of mentoring students, fellows, clinicians, and junior faculty. This special issue of The Anatomical Record honors Kurt's contributions to the journal, as well as to the fields of respiratory anatomy, physiology, and neonatology. Several of the invited papers were contributed by Kurt's collaborators and former trainees who cover topics related to neonatal lamb development, bronchopulmonary dysplasia, postnatal lung pathology, respiratory physiology, and the relationship of anatomy to function. Additional papers relating to Kurt's passion for dinosaur anatomy and human embryonic anatomy based on the Kyoto Collection of Human Embryos and Fetuses. Kurt's tireless enthusiasm for the journal and devotion to the field are reflected in the papers in this special issue in his honor. His tenure at the journal was transformative and provided a foundation for continued growth and impact in anatomical sciences research from dinosaurs to clinical applications in humans. We celebrate Kurt's accomplishments and broader impact on anatomical sciences in this Special Issue of The Anatomical Record.

The human voice is a major signal transmission modality for our species. Accordingly, perception of its quality serves as an intraspecific window into the status of an individual's health, robusticity, and even stature in the group. Diminished quality-as may occur in aging or certain diseases-is a major feature in the lessening of an individual's communication modality. Here, we review the underlying anatomy and function that comprise the voice producing elements-the vocal tract sensu lato-from the lungs through the larynx and supralaryngeal modifying elements. Aspects of the aging larynx and constituent elements such as the vocal folds ("true vocal cords") and intrinsic laryngeal joints, are discussed within the context of how their aging or disease degradation may affect an individual's speech and concomitant perception and interpretation by listeners. The aging voice is considered within the context of the overall effects of aging sensory systems in both humans and other mammals.

Determining the ecology of fossil species presents considerable challenges due to the often fragmentary preservation of specimens. The mammaliaform Hadrocodium wui from the Jurassic of China is known only from the cranium and mandible but may have had a fossorial lifestyle. It shares morphological similarities with talpid moles and soricid shrews and is closely related to other fossorial mammaliaforms. However, the lack of postcranial elements has so far precluded a definitive assessment regarding its fossorial behavior. Using a combination of geometric morphometric analysis of the lower mandible and finite element analyses of the cranium, comparisons between H. wui and extant groups are made. H. wui resembles talpid moles more closely than shrews in mandible shape. However, there are more similarities between H. wui and semi-fossorial/semi-aquatic moles than fully fossorial moles. The skull of H. wui is particularly weak in every tested biomechanical scenario when compared to the related mammaliaform Morganucodon oehleri and talpid moles. This weakness is potentially a result of the reduction in thickness of the zygomatic arch. In contrast, the shrew crania show similar stress magnitudes and distribution. These results imply that H. wui was not fully fossorial and fed on a diet of softer invertebrates. Skull morphology may therefore not be sufficient to infer fossoriality in forelimb-digging species.

Bones of the skull are traditionally categorized as derived from either endochondral or intramembranous bone. In our previous work, we have observed the interaction of different tissue types in growth of the skull. We find the dichotomy of intramembranous and endochondral bone to be too restrictive, limiting our interpretation of sources of biological variation. Here, we advocate for the use of the term ectochondral bone to describe bone that originates from an endochondral model but is directed in its subsequent growth by membranes and other fascial attachments. Growth of the alisphenoid and orbitosphenoid are described as two examples of ectochondral bone, influenced in their shape primarily by the surrounding soft tissues. Ectochondral bone may be an ideal mechanism for rapidly evolving new phenotypes. Instead of evolving novelties by altering morphology of the cartilage template, novel features may be formed by ectochondral ossification, a more direct and rapid mode of osteogenesis than that of the cartilage template.

Megantereon was a widespread saber-toothed felid from the Pliocene and Pleistocene of the Old World and North America, but its rarity in the fossil record makes it complicated to restore its life appearance. Lack of complete specimens makes it necessary to combine information from fossils of different individuals to reconstruct their facial anatomy. In this work, we combine the analysis of skulls and mandibles of Megantereon from various fossil sites with the study of extant carnivorans through dissection, 3D scans, and the observation of live individuals. Megantereon combined very elongated upper canines with mandibular flanges that were not deep enough to match the length of the sabers, as well as a wide maxilla combined with narrow incisor rows and mandibular symphysis. Such features are compatible with the presence of exposed canines in life, because the narrow symphysis allows room to accommodate lips and other soft tissues medial to the sabers, while the protrusion of the tips of the upper canines beyond the mental flanges makes it unlikely that they would be enveloped in soft tissue sheaths, which would dangle with the inherent risk of puncture. Megantereon was transitional between saber-toothed felids with covered upper canines, where saber length fits with mental flange depth, and the derived Smilodon where the upper canines are much longer than the flanges and the lips fit between upper canines and mandible, leaving the upper canine crowns largely exposed in life.