Journal of Anatomy

The ontogeny of Neanderthal (Homo neanderthalensis) perinates is poorly understood due to the paucity of juvenile skeletal remains. Here we reconstruct fetal bone growth, and explore deciduous tooth structures, in three Neanderthal juveniles (Sesselfelsgrotte, 1, 2 and 3) (90,000-50,000 years ago) from southeastern Germany using non-destructive microcomputed tomography. Sesselfelsgrotte 1 exhibited bone tissue consistent with modern human perinatal plexiform-like structures and primary osteons. Long bones showed regions of advanced growth compared to the mandible and frontal bone, which can be explained through different processes of ossification and potentially localized faster development in Neanderthals compared to modern humans. Bone microstructure resembles that of the late third trimester of modern humans, agreeing with previous estimates based on macroscopic data. Sesselfelsgrotte 2 and 3 deciduous teeth retain hypodensities deep within the crown dentine consistent with interglobular dentine. We conclude that the fetal bone patterning is similar to modern humans with areas of advanced growth, indicating that the growth trajectory for this Neanderthal perinate was broadly equivalent to that of modern humans. The abnormal dentine mineralization points toward a possible systemic disorder.

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.

Within tooth roots canals can vary in shape and configuration, and it is not uncommon for a single root to contain multiple canals. Externally, root morphology also varies, though the range of variation, and its relation to canals remains little explored. This investigation of modern human post-canine teeth uses data from computerized tomography scans of a global sample of 945 modern humans to identify the most frequent phenotypes of root and canal morphologies, and investigate how canal number, shape, and configuration relate to external root morphology. Results (1) include descriptions and definitions of root and canal morphologies, counts, and configurations; (2) indicate that certain canal counts, morphologies, and configurations can predict external morphologies; and (3) that this pattern varies in individual teeth and roots in the maxilla and mandible.

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.

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.

A new small-bodied troodontid (LH PV39) recovered from the Upper Cretaceous Wulansuhai Formation, Suhongtu, Inner Mongolia, China, is described. The new specimen preserves six postaxial cervical vertebrae, five completely fused sacral and four posterior caudal vertebrae in addition to two manual unguals. The completely fused neurocentral junctions indicate that a skeletally mature individual of the same species of LH PV39 would be smaller than Philovenator and comparable in body size to a skeletal mature individual of Almas. The extremely dorsoventrally compressed sacral centra and neural canal, and the middle three sacral centra that are shorter and wider than the first and the last one distinguishing LH PV39 from other known troodontids. A series of phylogenetic analyses were conducted using modified published matrices. By coding LH PV39 in different strategies, the troodontid affinity of LH PV39 is confirmed and it was recovered as the sister taxon of either Mei and Sinovenator (LH PV39 scored as a separate OTU) or Linhevenator (incorporating LH PV39 into Philovenator) in the best resolved coelurosaurian interrelationships. The referral of LH PV39 to Philovenator does not seriously alter the phylogenetic position of Philovenator nor the interrelationships of troodontids. This new finding confirms that the small and large sized troodontids are coexisted in the Gobi Desert of the Mongolia Plateau until the end of Cretaceous.

The mechanisms determining the rotation direction and position of hair whorls are unknown. Here we report observations on twins suggesting that the morphological parameters of whorls have genetic bases, and provide comparative data on whorls from children born in the Northern and Southern hemispheres, indicating that whorl formation also depends on environmental factors. Our results underline the importance of unusual morphological phenomena for providing general information on normal developmental processes, and plead for large-scale epidemiological assessments to support our surprizing initial findings.

Vocal learning is a rare evolutionary trait that evolved independently in three avian clades: songbirds, parrots, and hummingbirds. Although the anatomy and mechanisms of sound production in songbirds are well understood, little is known about the hummingbirds vocal anatomy. We use high-resolution micro-computed tomography (CT) and microdissection to reveal the three-dimensional structure of the syrinx, the vocal organ of the black jacobin (Florisuga fusca), a phylogenetically basal hummingbird species. We identify three unique features of the black jacobins syrinx: (i) a shift in the position of the syrinx to the outside of the thoracic cavity and the related loss of the sterno-tracheal muscle, (ii) complex intrinsic musculature, oriented dorso-ventrally, and (iii) ossicles embedded in the medial vibratory membranes. Their syrinx morphology allows vibratory decoupling, precise control of complex acoustic parameters, and a large redundant acoustic space that may be key biomechanical factors facilitating the occurrence of vocal production learning.

One of the decisive questions about human gross anatomy is unmatching the adult branching pattern of the spinal nerve to the embryonic lineages of the peripheral target muscles. The two principal branches in the adult anatomy, the dorsal and ventral rami of the spinal nerve, innervate the intrinsic back muscles (epaxial muscles), as well as the body wall and appendicular muscles (hypaxial muscles), respectively. However, progenitors from the dorsomedial myotome develop into the back and proximal body wall muscles (primaxial muscles) within the sclerotome-derived connective tissue environment. In contrast, those from the ventrolateral myotome develop into the distal body wall and appendicular muscles (abaxial muscles) within the lateral plate-derived connective tissue environment. Thus, the ventral rami innervate muscles that belong to two different embryonic compartments. Because strict correspondence between an embryonic compartment and its cognate innervation is a way to secure the development of functional neuronal circuits, this mismatch indicates that we may need to reconcile our current understanding of the branching pattern of the spinal nerve with regard to embryonic compartments. Accordingly, we first built a model for the branching pattern of the spinal nerve, based on the primaxial-abaxial distinction, and then validated it using mouse embryos. In our model, we hypothesized the following: 1) a single spinal nerve consists of three nerve components: primaxial compartment-responsible branches, a homologous branch to the canonical intercostal nerve bound for innervation to the abaxial compartment in the ventral body wall, and a novel class of nerves that travel along the lateral cutaneous branch to the appendicles; 2) the three nerve components are discrete only during early embryonic periods but are later modified into the elaborate adult morphology; and 3) each of the three components has its own unique morphology regarding trajectory and innervation targets. Notably, the primaxial compartment-responsible branches from the ventral rami have the same features as the dorsal rami. Under the above assumptions, our model comprehensively describes the logic for innervation patterns when facing the intricate anatomy of the spinal nerve in the human body. In transparent whole-mount specimens of embryonic mouse thoraces, the single thoracic spinal nerve in early developmental periods trifurcated into superficial, deep, and lateral cutaneous branches; however, it later resembled the adult branching pattern by contracting the superficial branch. The superficial branches remained segmental while the other two branches were free from axial restriction. Injection of a tracer into the superficial branches of the intercostal nerve labeled Lhx3-positive motoneurons in the medial portion of the medial motor column (MMCm). However, the injection into the deep branches resulted in retrograde labeling of motoneurons that expressed Oct6 in the lateral portion of the medial motor column (MMCl). Collectively, these observations on the embryonic intercostal nerve support our model that the spinal nerve consists of three distinctive components. We believe that our model provides a framework to conceptualize the innervation pattern of the spinal nerve based on the distinction of embryonic mesoderm compartments. Because such information about the spinal nerves is essential, we further anticipate that our model will provide new insights into a broad range of research fields, from basic to clinical sciences.

Specific character traits of mineralized endoskeletal tissues need to be clearly defined and comprehensively examined among extant chondrichthyans (elasmobranchs, such as sharks and skates, and holocephalans, such as chimaeras) to understand their evolution. For example, tiles of mineralized polygonal structures called tesserae occur at cartilage surfaces in chondrichthyans, but recent studies showing trabecular mineralization at elasmobranch cartilage surfaces suggest that tesserae are not as common as previously thought. Also, while areolar mineralized tissue in elasmobranchs is generally considered a unique, shared chondrichthyan feature, some chondrichthyan species demonstrate bone-like tissues in both a specific region of tesserae termed the cap zone and continuous (not tiled) mineralized neural arches. To clarify the distribution of specific endoskeletal features among extant chondrichthyans, adult skeletal tissues in a holocephalan chimaera (spotted ratfish) and two elasmobranchs (small-spotted catshark and little skate) were characterized using synchrotron radiation and desktop micro-CT imaging, and histological and immunofluorescent assays. Endoskeletal mineralization in the ratfish, catshark, and little skate varied both quantitively in tissue mineral density (TMD), and qualitatively in the morphology and localization of mineralized structures and tissues. For example, TMD of several skeletal elements was significantly lower in ratfish, compared to catshark and little skate. Trabecular and areolar mineralization were shared among these extant chondrichthyan species, but tesserae and bone-like tissues were not. Interestingly, three separate analyses argued that the adult chimaera endoskeleton has features of the embryonic little skate endoskeleton. Generally, this study proposes specific terminology for character states of the extant chondrichthyan endoskeleton and infers those states in ancestral chondrichthyans with reference to fossil data.

To understand how an extinct species may have moved, we first need to reconstruct the missing soft tissues of the skeleton which rarely preserve, with an understanding of segmental volume and the muscular composition within the body. The Australopithecus afarensis specimen AL 288-1 is one of the most complete hominin skeletons. Whilst it is generally accepted that this species walked with an erect limb, the frequency and efficiency of such movement is still debated. Here, 36 muscles of the pelvis and lower limb were reconstructed in the specimen AL 288-1 using 3D polygonal modelling which was guided by imaging scan data and muscle scarring. Reconstructed muscle masses and configurations guided biomechanical modelling of the lower limb in comparison to a modern human. Muscle moment arms were calculated and summed per muscle group. Simulated error margins were computed using Monte Carlo analyses. Results show that the moment arms of both species were comparable, hinting towards similar limb functionality. Moving forward, the polygonal muscle modelling approach has demonstrated promise for reconstructing the soft tissues of hominins and providing information on muscle configuration and space filling. This approach is recommended for future studies aiming to model musculature in extinct taxa.

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 olfactory system plays a critical role in mammalian environmental perception, with some clades relying on an expanded accessory olfactory (vomeronasal) system (VNS) to detect larger, non-volatile odorants. Mammals make extensive use of this system for social communication between conspecifics. Recent studies have begun to investigate how the VNS changes in response to or as part of ecological transitions. Several studies have identified trends of VNS-associated gene loss or regression in secondarily aquatic mammals. However, continuing discussion on genotype-phenotype correlation within the VNS means that greater effort should be made to investigate the morphology of the VNS in species where it remains poorly understood. Here, we use skeletal and soft-tissue data to demonstrate that the vomeronasal groove, an established osteological correlate for the VNO in bats and primates, is also a valid indicator for its presence in Caniformia. Additionally, we confirm the presence of the VNO in the secondarily aquatic North American river otter (Lontra canadensis) and compare its morphology with that of two close-related species, the semi-aquatic American mink (Neogale vison) and the terrestrial long-tailed weasel (Neogale frenata). This study expands the valid taxonomic scope of the vomeronasal grooves proxy as an osteological correlate, confirms the presence of the VNO in the previously undescribed system of the North American river otter, and highlights the complexity of the mammalian accessory olfactory system.

BackgroundThe axolotl is a key model to study appendicular regeneration. The limb complexity resembles that of humans in structure and tissue components; however, axolotl limbs develop post-embryonically. In this work, we evaluated the post-embryonic development of the appendicular skeleton and its changes with aging. ResultsThe juvenile limb skeleton is formed mostly by Sox9/Col1a2 cartilage cells. Ossification of the appendicular skeleton starts when animals reach a length of 10 cm, and cartilage cells are replaced by a primary ossification center, consisting of cortical bone and an adipocyte-filled marrow cavity. Vascularization is associated with the ossification center and the marrow cavity formation. We identified the contribution of Col1a2-descendants to bone and adipocytes. Moreover, ossification progresses with age towards the epiphyses of long bones. Axolotls are neotenic salamanders, and still ossification remains responsive to L-thyroxine, increasing the rate of bone formation. ConclusionsIn axolotls, bone maturation is a continuous process that extends throughout their life. Ossification of the appendicular bones is slow and continues until the complete element is ossified. The cellular components of the appendicular skeleton change accordingly during ossification, creating a heterogenous landscape in each element. The continuous maturation of the bone is accompanied by a continuous body growth.

The potential for variation and the capacity to evolve in response to ecological opportunity are important aspects of an adaptive radiation. Identifying the origin of phenotypic variation, in which natural selection might act upon, is a major goal of evolutionary developmental biology. The New World leaf-nosed bats (phyllostomids) are a textbook example of an adaptive radiation. Their cranial morphology is diverse along relative facial length, which is related to their diets. We previously used geometric morphometrics to reveal peramorphosis, a type of heterochrony, in the cranial evolution among phyllostomid bats. We then demonstrated that the mechanism of peramorphic diversity in phyllostomid rostrum length resulted from altered cellular proliferation. Here, we investigate the progenitors of the face, the cranial neural crest, and a key signaling pathway related to their proliferation and differentiation into mature tissues: the bone morphogenetic protein (BMP). With geometric morphometrics, immunofluorescence, and confocal imaging--in three phyllostomid species and one outgroup bat species--we show the molecular patterns that underlie the adaptive and innovative traits seen in phyllostomid bats. Then, with mouse genetics, we mimic the BMP molecular pattern observed in nectar feeding bats and recapitulate the elongated morphological variation in mice. Surprisingly, we also observe an expansion in the nose-tip of mice, akin to the expanding leaf-nose tissue in phyllostomid bats. These data, combined with the mouse genetics literature on BMP signaling, suggest the BMP developmental pathway plays a central role in shaping the craniofacial variation necessary for adaptation in bats. Further, we speculate that the BMP signaling pathway could underlie other bizarre facial phenotypes in mammals that are derived from frontonasal mesenchyme, such as the proboscis. Overall, this study combines a comparative framework to developmental data, with a genetic approach, to directly investigate the role of development on complex morphology.

Because brain tissues rarely fossilize, pinpointing when and how modern human cerebral traits emerged in the hominin lineage is particularly challenging. The fragmentary nature of the fossil material, coupled with the difficulty of characterizing such a complex organ, have been the source of long-standing debates. Prominent among them is the uncertainties around the derived or primitive state of the brain organization in the earliest representatives of the genus Homo, more particularly in key areas such as the Brocas area. By revisiting a particularly well-preserved fossil endocast from the Turkana basin (Kenya) attributed to early Homo, here we confirm that humans in Africa had a primitive organization of the Brocas area ca. 1.9 million years ago. Additionally, our description of KNM-ER 3732 adds further information about the variation pattern of the inferior frontal gyrus in fossil hominins, with implications for early Homo taxic diversity (i.e., one or two Homo species at Koobi Fora) and the nature of the mechanisms involved in the emergence of derived cerebral traits.

Morphological covariation within the modern human postcanine dentition remains an open field of study. Analysis of covariation patterns of the three-dimensional (3D) shape between different tooth types has been seldom conducted, but it is relevant for the advancement of human biology and evolution, as well as dental anthropology, phylogeny, and medicine. Here, we analysed 3D shape covariation of the postcanine dentition (excluding third molars), both within and between dental arches using geometric morphometrics (GM). Based on high-resolution ({micro}CT) scans of 526 teeth from 136 individuals we found high pairwise correlation in tooth pairs within the dental arches (lower P3 and P4, r1 = 0.89; upper P3 and P4, r1 = 0.81; upper M1 and M2, r1 = 0.86). The correlation values between antagonists varied notably from the highest value detected between upper and lower M1s (r = 0.9), to the lowest between upper P4s and lower M1s (r = 0.58). Of all analysed tooth types, only the upper M1s showed moderate to high correlation in every pair analysis. Noticeably, unusually high covariation was detected between some of the tooth type pairs that do not articulate in a normal dentition (e.g., lower P3 and upper M2, r1 = 0.88). Furthermore, a relatively high covariation was found in the pairs of lower P4s and M1s (r1 = 0.79), and upper P4s and M1s (r1 = 0.77), which are the only tooth type pairs of the postcanine dentition belonging to different tooth classes (premolars and molars, respectively) and still serving similar masticatory functions. This study points to the fact that higher morphological integration seems to characterize teeth within the same dental arch rather than between antagonistic teeth. With this study, we provided an overview of pairwise correlations and strength of covariation between different tooth types. This information might inform future studies aimed at understanding developmental, phylogenetic, and functional aspects of the human postcanine dentition, including possible phenotype-genotype associations. However, with this study being the first one performed on a 3D sample of this size, we also report on obstacles and peculiarities that have been determined.

BackgroundBorderline hip dysplasia (BhD) might be associated with insufficient acetabular coverage. Thus, we investigated potential differences in acetabular anatomical measurements derived from computerized tomography (CT) that characterize BhD compared with healthy controls. MethodsBhD patients (LCEA between 18{o} and 25{o}) and healthy controls (LCEA between 25{o} and 40{o}) underwent anteroposterior pelvic X-ray and CT to study Wiberg and Tonnis angle, extrusion and Fear index, notch width and depth, anterior and posterior wall height, anterior and posterior articular surfaces, articular circumference, the ratio between the anterior articular surface and the articular circumference, the ratio between the posterior articular surface and the articular circumference, and the ratio between the notch width and the articular circumference. An independent two-tailed t-test, U of Mann-Whitney test, and odds ratios were obtained ( = 5%). ResultsTwenty-three BhD patients aged 31.5 {+/-} 8.3 years and LCEA 21.6{degrees} {+/-} 4.0{degrees} and thirty-one healthy controls aged 34.1 {+/-} 8.0 years and LCEA 33.7{degrees} {+/-} 5.5{degrees} were included. The sensitive CT features for BhD were anterior (p < 0.001) acetabular surface, anterior (p = 0.009), anteroposterior (p = 0.008) and posterior (p < 0.008) acetabular surface ratios, and acetabular notch width (p = 0.002). ConclusionsBhD CT characterization provides tridimensional anatomical insights beyond the LCEA. BhD insufficient acetabular coverage can be found along the superior (lower Wiberg angle, and increased Tonnis angle and extrusion index), anterior (lower anterior acetabular surface and anteroposterior acetabular surface ratio, and increased posterior acetabular ratio), and inferior (increased acetabular notch width) axis.

Teleost fishes comprise more than 36,000 living vertebrate species and occupy a wide range of aquatic ecosystems. Despite their overwhelming success, extinct taxa outside of the living radiation--stem teleosts--remain poorly understood. Dorsetichthys bechei is an Early Jurassic stem teleost of historic importance. Although D. bechei is well described, its proximity to the teleost crown and relationships with other stem teleosts is challenging due to previous associations with the wastebasket assemblage known as "pholidophorids". Here we present a new, three-dimensionally preserved specimen of Dorsetichthys bechei from the Blue Lias Formation (Sinemurian) Lyme Regis, UK. High-resolution CT scanning of this specimen plus additional material reveals previously unknown internal morphological information, including of the jaw and palate, hyoid arch, and gill skeleton. Importantly, this previously undescribed articulated specimen permits description of the external dermal skeleton and internal endoskeleton for the same individual, clarifying past accounts drawing on composite descriptions of two- and three-dimensionally preserved specimens. We confirm the presence of important teleost synapomorphies such as a mobile premaxilla and quadratojugal process. However, contrasting previous accounts, we find no evidence for dorsal and ventral hypohyals or a postarticular process of the lower jaw. We also confirm the presence of a prearticular. The presence of a mobile upper jaw, elaborate gill rakers and reduced dentition also support a possible facultative filter feeding ecology. These new anatomical data support removal of D. bechei from Pholidophoridae and Pholidophoriformes as currently defined but indicate that finer-scale patterns of relationships among more crownward members of the teleost stem are some way from being resolved.

There is general awareness of artificial selection and its potential implications on health and welfare of animals. Despite growing popularity and increasing numbers of breeds of atypical colour and pattern variants in reptiles, only few studies have investigated the appearance and cause of various diseases associated with colour morphs. Ball pythons (Python regius) are among the most frequently bred reptiles and breeders selected for a multitude of different colour and pattern morphs. Among those colour variants, the spider morph of the ball python is frequently associated with the wobble syndrome. The aim of this study was to determine, whether a morphological variant can be found and brought in association with the clinical occurrence of the wobble syndrome in spider ball pythons, using MRI and CT-imaging as intra-vitam diagnostic methods. Data from eight ball pythons including five spider ball pythons and three wild type ball pythons was assessed and evaluated comparatively. We were able to identify distinctive structural differences in inner ear morphology in spider ball pythons highly probable to relate to the wobble syndrome. To our knowledge, these anomalies are described for the first time and represent a basis for further anatomical and genetic studies and discussions regarding animal welfare in reptile breeding.