The Anatomical Record

The detection of chemical signals by the vomeronasal organ (VNO) is critical for communication among mammals from an early age, influencing behaviors such as suckling and recognition of the mother and conspecifics. Located in a concealed position at the base of the nasal cavity, the VNO features a duct covered with a sensory epithelium rich in neuroreceptors. A critical aspect of VNO functionality is the efficient access of stimuli from the nasal and oral cavities to the receptors. In adult dogs, it has been demonstrated through in vivo magnetic resonance imaging and anatomically postmortem how the VNO duct (VD) communicates to the environment through the incisive duct (ID). However, in newborn puppies, the existence of functional communication between the ID and the VD has not been confirmed to date, raising doubts about the potential physiological obliteration of the ID due to its small size and the degree of immaturity of the puppies at birth. Determining this aspect is necessary to evaluate the role played by chemical communication in this critical phase for the survival and socialization of puppies. This study employs serial histological staining techniques to examine the presence and functionality of the incisive duct in neonatal dogs. The serial histological sections have confirmed both the existence of functional communication between both the vomeronasal and incisive ducts in perinatal puppies, and the dual functional communication of the incisive duct with the oral and nasal cavities. The ID shows an uninterrupted lumen along its path and is associated with a sophisticated cartilaginous complex that prevents its collapse, as well as erectile tissue rich in blood vessels and connective tissue that acts as a cushion, facilitating its action under pressure induced by sampling behaviors such as tonguing. This investigation demonstrates the communicative capabilities of the VNO during the perinatal stage in dogs.

Marsupials are born with structurally immature lungs when compared to eutherian mammals. The Gray short-tailed opossum (Monodelphis domestica) is born at the late canalicular stage of lung development. Despite the high degree of immaturity, the lung is functioning as respiratory organ, however supported by the skin for gas exchange during the first postnatal days. Consequently, the majority of lung development takes place in ventilated functioning state during the postnatal period. X-ray computed tomography ({micro}CT) was used to three-dimensionally reconstruct the terminal airspaces in order to reveal the timeline of lung morphogenesis. In addition, lung and air space volume as well as surface area were determined to assess the functional relevance of the structural changes in the developing lung. The development of the terminal air spaces was examined in 35 animals from embryonic day 13, during the postnatal period (neonate to 57 days) and in adults. At birth, the lung of M. domestica consists of few large terminal air spaces, which are poorly subdivided and open directly from short lobar bronchioles. During the first postnatal week the number of smaller terminal air spaces increases and numerous septal ridges indicate a process of subdivision, attaining the saccular stage by 7 days. The 3 D reconstructions of the terminal air spaces demonstrated massive increases in air sac number and architectural complexity during the postnatal period. Between 28 and 35 days alveolarization started. Respiratory bronchioles, alveolar ducts and a typical acinus developed. With alveolarization the volume of the air spaces and the surface area for gas exchange increased markedly. The structural transformation from large terminal sacs to the final alveolar lung in the Gray short-tailed opossum follows similar patterns as described in other marsupial and placental mammals. The processes involved in sacculation and alveolarization during lung development seem to be highly conservative within mammalian evolution.

Wolves, like other canids, extensively use chemical signals for various aspects of communication, including territory maintenance, reproductive synchronization, and social hierarchy signaling. Pheromone-mediated chemical communication operates unconsciously among individuals, acting as a mysterious sixth sense that regulates both their physiology and behavior. Despite their crucial role in the life of the wolf, there is a surprising lack of comprehensive research on the neuroanatomical and physiological bases of chemical communication in wolves. This study delves into the Iberian wolf vomeronasal system (VNS) and examines potential changes brought about by dog domestication. Our findings show that the Iberian wolf possesses a fully functional VNS vital for pheromone-mediated communication. While macroscopic similarities between the wolf and domestic dog VNS are observed, there are notable microscopic differences. These include the presence of neuronal clusters associated with the sensory epithelium of the vomeronasal organ (VNO) and a higher differentiation degree of the accessory olfactory bulb (AOB). Immunohistochemical markers reveal the expression of the two main families of vomeronasal receptors (V1R and V2R) in the VNO. However, only the V1R family is expressed in the AOB. These findings not only provide deep insights into the VNS of the wolf but also hint at how domestication might have altered neural configurations that underpin species-specific behaviors. This understanding has implications for innovative strategies, such as employing semiochemicals for wolf population management, aligning with modern conservation goals.

Marsupials (Marsupialia, Mammalia) represent a clade with highly varied ecologies. This is particularly true for opossums (South American marsupials), which are difficult to observe and collect. Consequently, few studies have focused on their bite force and the muscles of their masticatory apparatus, and there exists only scant information about the diet of certain species. Here we describe the masticatory muscles of several previously unstudied opossum species including Caenolestes fuliginosus, Dromiciops gliroides, and Monodelphis touan. We calculate the bite force of these species using data from both manual and virtual dissections and compare their theoretical bite forces with literature data. Additionally, we explore the differences between manual and virtual dissection to determine muscle PCSA (Physiological Cross-Sectional Area). We tried two virtual methods (VPDE: "virtual physiological data estimating method" and SM: "slicing muscle method") to calculate the PCSA, determine the differences induced by the inter-fiber void in the virtual volume, and calculate a correction post-treatment with the contrast agent. The results highlighted variation in the position of the muscular attachments of the M. zygomaticomandibularis, whose insertion area is the largest in Monodelphis touan and the smallest in Caenolestes fuliginosus. The bite forces are coherent with estimates from the literature suggesting that the biomechanical model is reliable. The comparison between manual and virtual dissection showed that while virtual dissection allows an overall description of the masticatory muscles, it is more complex to accurately describe the different subdivisions of the muscle bundles. Virtual dissection data could potentially complete manual dissection data with the association of the VPDE method, the exclusion of inter-fiber voids, and a correction for the treatment with contrast-agents.

The aim of this study was to explore and compare patterns of morphological covariation, including symmetrical deviations, between splanchnocranium and the basicranium in Toy rabbit, a type of paedomorphic rabbit. A sample of 32 skulls of adult Toy rabbits was studied on digital pictures on ventral aspects by means of geometric morphometric methods. A set of 7 landmarks were located on the horizontal plane of the splanchnocranial ventral bones (palatine process of the maxillary bone [processus palatinus maxillae] + palatine bone [lamina horizontalis ossis palatini]), and a set of 8 landmarks were on the basicranium (sphenoid [os sphenoidale] + basilar part of the occipital bone [pars basilaris] + bulla tympanica). Both fluctuating and directional asymmetries were detected on both blocks, being the asymmetry more important among splanchnocranial bones. It appeared also a significant relationship (allometry) between size and shape, especially in the basicranium, as well a significant relationship between the two blocks. From results we deduce that, although normally cranial base usually reaches adult size before the face, in paedomorphic animals the face stops its growth earlier than basicranium, resulting in their proportionally reduced splanchnocranium, the typical brachyfacial morphology for paedomorphy. In other words, our results support the hypothesis of an early stop of facial pattern development in neoteny -the retention of juvenile characteristics into adulthood-, which can affect vital structures. So, further research should expand on clinical data of paedomorphic animals in order to advance in the understanding of pathological results of this growth anomaly.

This study explores the ocular anatomy and glandular components of domestic dogs compared to their ancestor, the wolf, with the aim of identifying evolutionary changes due to domestication and their implications for ocular pathologies. Utilizing histological and histochemical techniques, including hematoxylin-eosin, PAS, Alcian Blue, and lectins, this research conducts a detailed analysis of the canine and wolf ocular systems, particularly focusing on the eyelids, tarsal glands, and conjunctival tissues. Results indicate significant histological differences between the two species, particularly in the thickness and secretion levels of the conjunctival epithelia and the structure of the tarsal glands. Dogs exhibit a thicker epithelium with greater PAS and Alcian Blue positive secretion, suggesting enhanced ocular protection and lubrication adapted to domestic environments. Conversely, wolves display more concentrated glandular secretions and a predominance of acidic mucopolysaccharides, aligning with their adaptation to natural habitats. This study also highlights the translational value of dogs as models for human ocular diseases, given their anatomical and physiological similarities with humans. Such comparisons are essential as they provide insights that can lead to advancements in medical research and clinical applications, especially in the development of treatments for ocular surface disorders.

The Eurasian lynx (Lynx lynx) was historically native to the Iberian Peninsula, as evidenced by scarce paleontological records and sightings across northern Spain, dating from the Last Glacial Maximum until the 17th century. A novel and nearly complete skeleton of a medium-sized felid, morphologically identified as L. lynx, was recently recovered from Sima Topinoria in Picos de Europa (Cantabria, Spain). The present study aims to recover and analyze the full skeletal assemblage, establishing its chronological framework, taxonomic identification, and comparative craniometry with other ancient and modern Eurasian lynxes. Radiocarbon dating estimates the specimen around 210 years BP, representing the most recent confirmed occurrence of Eurasian lynx in the Iberian Peninsula. This evidence revises the accepted timeline for the species extirpation in the region, indicating its persistence into the early 19th century, connecting physical evidence with historical and traditional narratives. Morphometric analysis identifies the individual as an adult male with an estimated body mass of 19.7 kg. Comparative osteometric analyses revealed that the specimen from Sima Topinoria falls within the average size for modern males from the Carpathian population, while being significantly smaller than older Holocene males from the Iberian Peninsula ([~]2570 yBP), suggesting a possible trend toward a protohistoric body size reduction in the Holocene, akin to patterns reported for other mammalian fauna from the Cantabrian Mountains. These results redefine the Eurasian lynx s historical range collapse in southwestern Europe, suggesting that the species survived until recent times, coinciding with periods of intense anthropogenic landscape change. The study highlights the critical role of paleontological data in refining extinction chronologies and contributes valuable insights into the biogeographic history of this elusive feline in western Europe.

The dama gazelle is a threatened and scarcely studied species of northern Africa. Human pressure has depleted the population of dama gazelles from tens of thousands to a few hundred individuals. Since 1970, after deriving from a founder population of the last 17 surviving individuals in the Western Sahara, it has been reproduced naturally in captivity. Although certain aspects of the reproductive biology of the dama gazelle have been established in preparation for the future implementation of assisted reproductive technology there is a lack of information regarding the role of semiochemical-mediated communication in the sexual behavior of the dama gazelle. This is partially due to the lack of a neuroanatomical and morphofunctional characterization of the dama gazelle vomeronasal organ (VNO); the sensory organ responsible for the processing of pheromones. This study aims to determine the presence in the dama gazelle of a VNO fully equipped to carry out its neurosensory function and to contribute to the understanding of the interspecific variability of the VNO of ruminants. Employing histological, lectin-histochemical and immunohistochemical techniques we have performed a detailed morphofunctional evaluation of the dama gazelle VNO along its entire longitudinal axis. The findings suggest that studies of the VNO should take a similar approach, as there are significant structural and neurochemical transformations that the organ exhibits as a whole. This study contributes to the understanding of the VNO in dama gazelles and provides a basis for future studies on semiochemical-mediated communication and reproductive management of this species.

During dissecting skulls of green frogs of the genus Pelophylax it has found that the description of a number bones and cartilaginous structures requires addition and clarification. In addition, previously undescribed details of anatomical structure of the skull of green frogs has revealed. The traits of anatomical structure of skull of green frogs, characteristic for ancestral forms of Anura found too.

The supracondylar foramen with a seemingly osseous peripheral arch noticed on the medio-distal feline humeri had remained disputed among anatomists. Some scholars have argued in favor of homology between this foramen and the supracondyloid foramen formed in the presence of the ligament of Struthers in humans. Other theories include its presence as a retinaculum holding the median nerve and brachial artery to their anatomical position in a flexed elbow. Unfortunately, these theories lack investigative rigor. The emergence of non-invasive imaging modalities, such as micro-computed tomography, has enabled researchers to inspect the internal anatomy of bones without dismantling. Thus, a micro-computed tomographic investigation was conducted on three feline humeri specimens while the internal anatomy of the supracondylar foramina was examined. Unlike the humerus, the thin peripheral arch of the feline supracondylar foramen failed to elicit any osseous trabeculae or foci of calcification. While adhering to the humeral periosteum at its origin, the non-osseous arch, typical of a muscular tendon or a ligament, inserts into a bony spur attached to the medial humeral epicondyle suggestive of a ligament or aponeurotic extension of a (vestigial) brachial muscle, with the coracobrachialis longus emerging to be the most likely candidate.

Sciurus vulgaris Linnaeus, 1758, the red squirrel, is a small, mostly arboreally living rodent, spread across the Palearctic. It is mostly vegetarian, feeding on plants, fungi and seeds, and is less active in the winter months, but does not hibernate. In this lateral study, the humeri of the subspecies Sciurus vulgaris fuscoater, the Central European red squirrel, were analysed to uncover potential intraspecific variation between individuals found in different seasons. The {micro}CT-scans were obtained with a resolution of 26 microns. Five bone parameters were calculated and statistically evaluated with regards to seasonal variations: total volume, bone volume, endocortical surface, cortical thickness, and average trabecular thickness. Bone volume, trabecular thickness and endocortical thickness correlate with bone size, whereas cortical thickness does not. Seasonal differences were observed between the warmer summer and autumn months versus the colder winter and spring months for all parameters. We, speculatively, relate the observed seasonal variation to nutrient intake, notably calcium. These results offer a deeper understanding of intraindividual variation in red squirrels, that may be useful in further ecological, taxonomic, and paleontological research.

Heterochronic shifts are regarded one of the major evolutionary changes acting on developmental modules and underlying the origin of morphological disparity. Conserved characters, rarely subject to heterochronic shifts during the curse of evolution, in contrast could indicate underlying developmental or functional constraints. Here we use the development of the cranial musculature Siberian sturgeon (Acipenser baerii) as a model to investigate the role of heterochrony during the evolution of the craniofacial system of Actinopterygii. Using histology, fluorescent antibody staining and fast propagation-based phase contrast imaging in combination with 3D-reconstruction we describe the development of the branchial and hypobranchial musculature. We show that the development of the first branchial arch is accelerated compared to other basal-branching actinopterygians leading to a more synchronous development with the hyoid arch. A pattern that could relate to the derived migratory behaviour of the neural crest cells in sturgeons. In contrast, the developmental timing of the more posterior branchial musculature, including the cucullaris muscle in the Siberian sturgeon, appears to be highly conserved compared to other Actinopterygii and even Osteognathostomata. This could indicate the presence of functional or developmental constraints underlying the evolution of the muscles at the head/trunk interface.

As biological shape is usually complex and evolves on different constraints, it can be assessed using integrative methods such as geometric morphometrics. Allometric changes were analysed in three species of Didelphis genus (D. albiventris n=20, D. marsupialis n=82, D. pernigra n=35) by means of geometric morphometric techniques. A significant correlation between shape and size was found, suggesting an allometric change pattern for all three species studied. However, allometries appeared to be different between D. marsupialis and D. pernigra, both of which belong to different groups (the so-called black-eared group and the white-eared group, respectively). Results are consistent with taxonomic recognition at the group level and can help to elucidate phylogenetic relationships between these three Didelphis species.

Morphological integration and modularity are concepts that refer to the covariation level between the components of a structure. Species of the opossums, genus Didelphis, have been the object of several taxonomic and morphometric analyses but no study has so far analysed mandibular morphological integration and modularity at a species-level. The aim of this work was to check whether the body (corpus mandibulae, mandibular corpus) and the ramus (ramus mandibulae, ascending mandibular ramus) are separate modules in Didelphis pernigra using a two-dimensional geometric morphometric approach. For this purpose, a sample of hemimandibles from 36 D. pernigra (13 males and 23 females) was analysed using 17 landmarks in lateral view. The modularity hypothesis based on different developmental origins was tested, by using the RV coefficient. Later, the integration level was assessed applying a partial least-squares analysis (PLS). The underlying aim was to know whether the traditional division between mandibular body and ramus has a modular basis, as well as the morphological integration level between these two structures. Results reflected that landmarks integration was not uniform throughout the mandible but structured into two distinct modules: ramus and body. Results allow to conclude that allometry plays an important role in shape variation in this species, and that the hypotheses of two-module organization in males cannot be confirmed. Models that accurately represent the biting mechanics will strengthen our understanding of which variables are functionally relevant and how they are relevant to performances, not only masticatories.

The use of osseous materials for crafting various artifacts is well-attested in the archaeological record of the ancient Near East. While bone, the most common and available material, was used more frequently, ivory was highly valued as an exotic material for fashioning exquisite prestige items designed for ostentatious display and linked to societys elite strata. Therefore, reliably distinguishing between the taxonomic origins of the osseous artifacts is significant for interpreting the archaeological data. In the Near East, the demand for ivory products reached its zenith during the mid-2nd to mid-1st millennia BCE, producing one of the largest assemblages unearthed anywhere in the world. Using state-of-the-art bio-molecular analyses to study this collection is costly, time-consuming, and entails damaging the highly-curated artifacts. This paper provides an essential, simple, non-destructive, and validated method to distinguish bone from elephant or hippo ivory (the most common osseous materials attested in the Near East record). However, following similar guidelines can help index other biological sources of ivory.

It has been hypothesized that subterranean mammals have evolved increased skin elasticity to reduce friction when moving through their underground tunnel systems. This trait is commonly believed to be mediated by greatly elongated hyaluronan (HA) polymers in the dermal extracellular matrix, which have been reported from different distantly related burrowing mammals. However, replicating these findings has proven difficult, and a mechanism by which HA polymer size could modify skin elasticity has not been proposed. In fact, experimental data on skin biomechanics in burrowing mammals are currently unavailable. Here, we quantify the molecular mass of HA polymers extracted from the tissues of Ansells mole-rat (Fukomys anselli), a burrowing rodent yet unstudied in that respect, and investigate skin biomechanics in subterranean and epigeic small mammal species by means of in vivo-cutometry. We did not recover extremely elongated HA polymers in Ansells mole-rat, conflicting with published findings in congeneric species and the naked mole-rat. Polymer length in mole-rats was found to be moderately increased compared to guinea pigs across tissues, though. Our data on skin biomechanics indicate that subterranean mammal skin is not more elastic than that of epigeic forms. Interestingly, the skin of the naked mole-rat was characterized by very high stiffness. Uniaxial tensile tests demonstrated that it also exhibits exceptional tensile strength. Hence, we challenge the idea that hyaluronan or a subterranean ecology notably influences skin elasticity in small mammals and suggest that previous studies may have confused elasticity with skin looseness, a fundamentally different phenomenon.

Mammal tails have long been recognized for their diversity of morphological form and function, however, there remains a substantial gap between the motivation to understand and emulate the various performance functions of the tail and what is known about tail anatomy. In this study, we were motivated to discover the anatomical foundations of the fast, whipping motions of the tail of the lesser Egyptian jerboa (Jaculus jaculus), which may aid in the quick changes of direction as the animal escapes from predators using ricochetal bipedal hopping. We employed microCT scans, dissections, and museum data to describe the musculoskeletal anatomy of the jerboa in comparison with the laboratory mouse (Mus musculus) and rat (Rattus norvegicus). While many aspects of tail anatomy are conserved across these species, the jerboa does possess unique characteristics such as an extremely long tail arising from caudal vertebral elongation, development of extensive dorsal musculature differentiated into lateral and medial components to increase points of skeletal attachment, and a novel anatomical feature - the bi-lobed cranial transverse process - which serves as a supernumerary dorsal tendon attachment site and possible brace to protect the ventral tendons and intrinsic muscles for a section of caudal vertebrae which likely experiences high mechanical stress.

Spider morph ball pythons are a frequently bred design morph with striking alterations of the skin color pattern. We created high resolution {micro}CT-image series through the otical region of the skulls, used 3D-reconstruction software for rendering anatomical models, and compare the anatomy of the semicircular ducts, sacculus and ampullae of wildtype Python regius (ball python) with spider morph snakes. All spider morph snakes showed the wobble condition. We describe the inner ear structures in wild-type and spider-morph snakes and report a deviant morphology of semicircular canals, ampullae and sacculus in spider morph snakes. We also report about associated differences in the desmal skull bones of spider morph snakes. The spider morph snakes were characterized by wider semicircular canals, anatomically poorly defined ampulla, a deformed crus communis and a small sacculus, with a highly deviant x-ray morphology as compared to wildtype individuals. We observed considerable intra- and interindividual variability of these features. This deviant morphology of spider morph snakes can easily be associated with an impairment of sense of equilibrium and the observed neurological wobble condition. Limitations in sample size prevent statistical analyses, but the anatomical evidence is strong enough to support an association between the wobble condition in design bread spider morph snakes and a malformation of the inner ear structures. A link between artificially selected alterations in pattern and specific color design with neural-crest associated developmental malformations of the statoacoustic organ as known from other vertebrates is discussed.

Using photographs of swimming blue whales and mounted skeletons, the body form of the largest known animal is correctly restored, no previous effort having been entirely accurate in part because of the absence of rigorous technical efforts prior to this study. The maximum total length/depth ratio is about 7.5-8.1, with the greatest depth in the chest forward of midlength. There is a subtle ventral concavity between the chest and abdomen. The chest is broader than deep, contradicting mounted skeletons in which the ribs are articulated too vertically so that the chest is falsely deeper than broad. The tip of the mandible is fairly blunt, although the throat pouch is streamlined when cruising, the head is very large. The result is an elongated, tear drop, hydrodynamically optimized shape. A volume based mass estimate based on the restoration is close to that observed in harvested blue whales relative to length, and indicates that the largest individuals reach ~200 tonnes.

The scaling pattern of the hind limb in Carnivora was determined using a sample of 13 variables measured on the femur, tibia, and calcaneus, of 429 specimens belonging to 141 species. Standardized major axis regressions on body mass were calculated for all variables, using both traditional regression methods and phylogenetically independent contrasts (PIC). Significant differences were found between the allometric slopes obtained with traditional and PIC regression methods, emphasizing the need to take into account phylogenetic relatedness in scaling studies. Overall, the scaling of the carnivoran hind limb conformed to geometric similarity, although some deviations from its predictions (including differential scaling) were detected, especially in relation with swimming adaptations. The scaling pattern of several phyletic lines and locomotor habits within Carnivora was also determined. Significant deviations from the scaling pattern of the order were found in some phyletic lines, but not in the locomotor habit subsamples. This suggests that the scaling of the carnivoran hind limb is both more heavily influenced by phylogenetic relatedness than by locomotor specializations, and more conservative than that of the forelimb. Finally, together with our previous work on the carnivoran forelimb, the results of the present study suggest that, in large non-aquatic carnivorans, size-related increases in bone stresses are compensated primarily by limb posture changes instead of by modifying limb bone scaling. However, increasing bone robusticity might also occur in the forelimb in response to the heavier stresses acting on the forelimbs due to asymmetrical body weight distribution.