Morphology of urinary system in six-banded armadillo (Euphractus sexcinctus, Linnaeus, 1758).

Euphractus sexcinctus is a wild mammal native to the Americas; they have great diversity and are not in danger of extinction like other armadillo species. Despite the diversity, the morphology of several biological systems of this species has not been fully described. This study details the gross and microscopic anatomy of the urinary system in Euphractus sexcinctus, a six-banded armadillo, compared with other mammalian study models. Six animals were dissected in the study. In the anatomical analysis, the kidneys, ureters, urinary bladder and urethra were dissected and photographed; then, fragments were submitted to histological routine for staining with haematoxylin-eosin, toluidine blue and Masson's trichrome for visualization under light microscopy. The six-banded armadillo ureter is histologically composed of four concentric layers. The urinary bladder is presented with three tissue layers. The pattern of constitution and distribution of urinary system structures was compatible with that of most domestic like Canis familiaris and wild animals like Bradypus torquatus, with adaptations for the arid and semi-arid habitat. The description of the morphology of Euphractus sexcinctus presents great relevance both for its conservation and for its use as a model for clinical research.

Taxonomic revision of the genus Cabassous McMurtrie, 1831 (Cingulata: Chlamyphoridae), with revalidation of Cabassous squamicaudis (Lund, 1845).

Cabassous comprises armadillos lacking a full osteoderm cover in the tail, justifying its common name naked-tailed armadillos. In the only taxonomic revision of the genus, in 1980, four living species were recognized, including a polytypic taxon with two subspecies. Recent studies have questioned this classification, but a comprehensive taxonomic review is lacking. Here, we revise the taxonomy of the genus Cabassous using complementary morphological approaches and clarify the geographical limits of naked-tailed armadillo species. Based on qualitative and quantitative analyses, we recognize five living species: C. centralis, C. chacoensis, C. squamicaudis, C. unicinctus, and C. tatouay. Most of the species can be easily differentiated using external or cranial traits, except C. centralis and C. unicinctus, which share several morphological features. The scutes pattern on the cephalic shield is an important diagnostic feature in naked-tailed armadillos and can be easily applied in field studies. Cabassous squamicaudis and C. unicinctus were previously treated as subspecies but we show they have conspicuous diagnostic traits, without mixture of characters even in closer contact. Cabassous species can be classified as open-dwellers (C. chacoensis and C. squamicaudis), forest-dwellers (C. centralis and C. unicinctus), or of more generalist habits (C. tatouay). We designate a lectotype for C. unicinctus to preserve its long-term nomenclature use.

Forelimb myology of armadillos (Xenarthra: Cingulata, Chlamyphoridae): Anatomical correlates with fossorial ability.

Descriptions of myology reflect adaptations of the post-cranium and are essential for understanding the functional morphology of animal limbs. Armadillos (Cingulata) are the most species-rich group of the basal superorder Xenarthra, which is evident by their various lifestyles (subterranean vs. terrestrial) and levels of fossoriality (fossorial vs. semi-fossorial). While there have been several studies on limb bone proportions in numerous armadillos, limb myology has been reported for a limited number of species. Many of these descriptions need updating, and detailed quantitative muscle data are available only for nine-banded armadillos. The main objective of this study is to assess the forelimb myology of the pichi (Zaedyus pichiy), screaming hairy (Chaetophractus vellerosus), large hairy (Chaetophractus villosus), and pink fairy (Chlamyphorus truncatus) armadillos with comparisons to previous observations to specify muscle traits that indicate scratch-digging specializations in cingulates. Several myological features are variable among the species studied, including the origin of m. trapezius pars cervicalis, presence of a distinct m. rhomboideus profundus and m. omotransversarius, and number of heads present for m. triceps brachii and m. flexor digitorum profundus, all of which can be associated with variability in their respective habitats and functional habits. These traits are consistently observed in the members of the Euphractinae, whereas they are slightly divergent (i.e., reduced complexity) in the pink fairy armadillo despite a similar distribution of muscle mass in the limb retractors, elbow extensors, and carpal/digital flexors across species. The ecomorphology observed here among cingulates also confirms their recent reorganization into separate families and subfamilies.

MORPHOLOGICAL DIVERSITY OF FACIAL VIBRISSAE IN Chaetophractus vellerosus (MAMMALIA, XENARTHRA, DASYPODIDAE) AND DIFFERENTIAL MECHANOPERCEPTION.

Vibrissae are specialized and complex mechanoreceptor organs present in the skin of most mammals that respond to a diverse mechanical stimuli (e.g. tension, pressure, movement, vibrations) and provide information on distance to the object, its location/orientation, and general characteristics of its surface; also, it may play diverse roles during food acquisition and attacking potential prey. There are scarce papers on the vibrissae of armadillos, only considering their presence/absence and distribution, but no histological analyses have been made. The goal of our contribution is to perform a histological study of the head vibrissae of Chaetophractus vellerosus, identify their morphological features, the tissues that form them, interpret their possible functions, and attempt to link the characteristics with ecological aspects of this species like its digging habits. Our results suggest that Chaetophractus vellerosus possesses two types of vibrissae: macro- and micro-vibrissae. Both types are similar in gross morphology, characterized mainly by an absence of annular sinus and ringwulst, but having a trabecular sinus that extends along the entire length of the follicle; these features might be linked to a reduction of its sensory capacity. Unlike other mammals, the macro-vibrissae are in the genal, anterobital and intermandibular regions, while micro-vibrissae are distributed in the superior labial and mental regions. In addition to size differences, the macro-vibrissae possess intrinsic muscles composed of smooth muscular fibers. The genal macro-vibrissae are very close to each other, with smooth muscle fibers connecting the capsules of adjacent ones (intrinsic muscles). Those from the superior labial and mental (micro-vibrissae), show bundles of striated muscle inserted on their capsules. These muscle fibers would be part of the facial musculature and could be considered as extrinsic muscles. The mobility of these two types of vibrissae must certainly be different, given that the respective muscles (intrinsic and extrinsic) have different origins and innervation. The presence of two types of vibrissae might indicate that these mechanoreceptors have differential perception capacities that would probably be complementary, thus providing more precise information about the environment. The presence of macro-vibrissae in the genal, anteorbital and intermandibular zone would be directly related to the life habits of Chaetophractus vellerosus.

Formation, structure, and function of extra-skeletal bones in mammals.

This review describes the formation, structure, and function of bony compartments in antlers, horns, ossicones, osteoderm and the os penis/os clitoris (collectively referred to herein as AHOOO structures) in extant mammals. AHOOOs are extra-skeletal bones that originate from subcutaneous (dermal) tissues in a wide variety of mammals, and this review elaborates on the co-development of the bone and skin in these structures. During foetal stages, primordial cells for the bony compartments arise in subcutaneous tissues. The epithelial-mesenchymal transition is assumed to play a key role in the differentiation of bone, cartilage, skin and other tissues in AHOOO structures. AHOOO ossification takes place after skeletal bone formation, and may depend on sexual maturity. Skin keratinization occurs in tandem with ossification and may be under the control of androgens. Both endochondral and intramembranous ossification participate in bony compartment formation. There is variation in gradients of density in different AHOOO structures. These gradients, which vary according to function and species, primarily reduce mechanical stress. Anchorage of AHOOOs to their surrounding tissues fortifies these structures and is accomplished by bone-bone fusion and Sharpey fibres. The presence of the integument is essential for the protection and function of the bony compartments. Three major functions can be attributed to AHOOOs: mechanical, visual, and thermoregulatory. This review provides the first extensive comparative description of the skeletal and integumentary systems of AHOOOs in a variety of mammals.

The middle ear of the pink fairy armadillo Chlamyphorus truncatus (Xenarthra, Cingulata, Chlamyphoridae): comparison with armadillo relatives using computed tomography.

The pink fairy armadillo Chlamyphorus truncatus is the smallest extant armadillo and one of the least-known fossorial mammals. The aim of this study was to establish if its middle ear is specially adapted to the subterranean environment, through comparison with more epigeic relatives of the groups Euphractinae (Chaetophractus villosus, Chaetophractus vellerosus, Zaedyus pichiy) and Dasypodinae (Dasypus hybridus). We examined the middle ears using micro-computed tomography and subsequent three-dimensional reconstructions. D. hybridus has a relatively small middle ear cavity, an incomplete bulla and 'ancestral' ossicular morphology. The other species, including Chlamyphorus, have fully ossified bullae and middle ear ossicles, with a morphology between 'transitional' and 'freely mobile', but in all armadillos the malleus retains a long anterior process. Unusual features of armadillo ears include the lack of a pedicellate lenticular apophysis and the presence, in some species, of an element of Paaw within the stapedius muscle. In common with many subterranean mammals, Chlamyphorus has a relatively flattened malleo-incudal articulation and appears to lack a functional tensor tympani muscle. Its middle ear cavity is not unusually enlarged, and its middle ear ossicles seem less robust than those of the other armadillos studied. In comparison with the euphractines, there is no reason to believe that the middle ear of this species is specially adapted to the subterranean environment; some aspects may even be indicative of degeneration. The screaming hairy armadillo, Chaetophractus vellerosus, has the most voluminous middle ear in both relative and absolute terms. Its hypertrophied middle ear cavity likely represents an adaptation to low-frequency hearing in arid rather than subterranean conditions.

Brain anatomy of two-toed sloth (Choloepus didactylus, Linnaeus, 1758): A comparative gross anatomical study of extant xenarthrans.

The neural system plays an important role in understanding some features of animals. Anatomical complexity correlates with the increase of functional capacity. Xenarthrans include anteaters (Vermilingua), armadillos (Cingulata) and sloths (Folivora). This group is the base of eutherian mammals, and understanding the anatomy of its neural system could provide data for functional and evolutionary interpretations. The gross anatomy of the xenarthran brain is recorded. Four extant families of Pilosa and two families of Cingulata were sampled. Usual dissection procedures were used, and the brains were analysed macroscopically. The brain of two-toed sloth, three-toed sloth, six-banded armadillo, giant anteater and collared anteater are gyrencephalic. Pygmy anteater, nine-banded armadillo, great long-nosed armadillo, southern naked-tailed armadillo and giant armadillo are lissencephalic. In most species, the rhinal fissure presents two segments, rostral and caudal (except in Vermilingua and three-toed sloth). The diencephalon and brainstem present similar anatomy. The cerebellum is wide and presents four lobes (rostral, central, caudal and floccular). Its average volume is 12.16% (Folivora), 14.26% (Vermilingua) and 18.61% (Cingulata). Among these groups, there is a statistical difference between Folivora/Cingulata concerning the cerebellum average. The general pattern of the brain of the xenarthrans is similar to that of other mammals.

Anatomical description of the aortic arch of a rare species "the giant armadillo" (Priodontes maximus; Kerr, 1792).

The giant armadillo (Priodontes maximus) is found in diverse habitats from South America. A female adult giant armadillo with a body mass of 45 kg was used. The animal was a victim of trampling on highway AC-40, at 70 km, near the municipality of Capixaba-Acre and the corpse donated to the Animal Anatomy Laboratory at Federal University of Acre (UFAC). The arterial system was filled with natural latex via the thoracic aorta in a direction opposite the blood flow to facilitate the description of the aortic arch and its side branches. The study was approved by CEUA/UFAC - no. 053/2015 and SISBIO no. 47124-1. The aortic arch issued side groups, which had the following sequence: brachycephalic trunk, left carotid artery, left subclavian artery. The brachycephalic trunk forked forming the right subclavian artery and the right common carotid artery. The arrangement allowed the whole carotid blood supply to the brain and surrounding structures present in the animal's head. The subclavian arteries, of homologous way, originated the arteries: vertebral, thoracic, and cervical costocervical trunk. The aortic arch armadillo showed the same pattern as that described for the Euphractus sexcinctus and different from those reported for the Dasypus novemcinctus and Tamandua tetradactyla. In addition, the function assigned to each branch was the same regardless of the species with which it was compared.

Micromorphology of osteoderms in Dasypodidae (Cingulata, Mammalia): Characterization and 3D-reconstructions.

Osteoderms are present in a variety of extinct and extant vertebrates, but among mammals, the presence of osteoderms is essentially restricted to armadillos (Cingulata, Dasypodidae). Osteoderms have been proposed to exhibit a variety of functionalities in Dasypodidae, mainly protection and thermoregulation, and they have been considered as one of the synapomorphies of this group. In this study, we use high-resolution microcomputed tomography to describe the osteoderm micromorphology of several extant species of Dasypodidae in a comparative context. This study allowed the identification, 3D-reconstruction and volume quantification of different internal structures of osteoderms as well as their interrelations. This detailed characterization of the internal osteoderm morphology was compared in a phylogenetic context to assess the evolutionary trends of the species involved. This enables the identification of distinctive patterns for the most widely recognized clades, the Dasypodinae and Euphractinae with a morphological homogeneity in the microstructure of their osteoderms, in comparison with Tolypeutinae where it has not been possible to establish a common morphological pattern. The most important features for linage differentiation is the degree of compaction of the osteoderms, the number of cavities and the development of hairs. It is likely that the differential development of the various structures occurred as adaptive response to climate changes.

Ontogenetic changes in the long bone microstructure in the nine-banded armadillo (Dasypus novemcinctus).

Analysis of ontogenetic changes in long bone microstructure aid in vertebrate life history reconstructions. Specifically, osteohistological examination of common fauna can be used to infer growth strategies of biologically uncommon, threatened, or extinct vertebrates. Although nine-banded armadillo biology has been studied extensively, work on growth history is limited. Here we describe long bone microstructure in tibiae and femora of a limited ontogenetic series of nine- banded armadillos (Dasypus novemcinctus) to elucidate patterns of bone growth. The cortex of the smallest individual is composed of compacted coarse cancellous bone (CCCB) and woven tissue. Extensive cortical drift is driven by periosteal erosion and further compaction of trabeculae resulting in an increase in the amount of CCCB. The cortex of the largest specimens is primarily CCCB with thickened endosteal bone and thin outer cortices of lamellar and parallel-fibered tissue. The outer cortices of the largest individuals are interpreted as an external fundamental system (EFS) indicating a cessation of appositional bone growth corresponding to skeletal maturity (i.e. asymptotic or adult size). The EFS forms in femora prior to tibiae, indicating femoral growth rates begin decreasing earlier than tibial in D. novemcinctus. Growth trends in common fauna like the nine-banded armadillo can be used as a foundation for understanding life histories of related, but uncommon or extinct, species of cingulates.

Taxonomic revision of the long-nosed armadillos, Genus Dasypus Linnaeus, 1758 (Mammalia, Cingulata).

Dasypus is the most speciose genus of the order Cingulata, including approximately 40% of known living armadillos. Nine species are currently recognized, although comprehensive analyses of the entire genus have never been done. Our aim is to revise the taxonomy of the long-nosed armadillos and properly define the taxa. We examined 2126 specimens of Dasypus preserved in 39 different museum collections, including 17 type specimens. Three complementary methods were applied to explore morphological datasets both qualitatively and quantitatively. Qualitative morphological variation in discrete characters was assessed by direct observations of specimens. Linear morphometric variation was based on external data and cranial measurements of 887 adult skulls. The shape and size of the skull was abstracted through two-dimensional geometric morphometric analyses of dorsal, lateral and ventral views of respectively 421, 211, and 220 adult specimens. Our results converge on the recognition of eight living species (D. beniensis, D. kappleri, D. mazzai, D. novemcinctus, D. pastasae, D. pilosus, D. sabanicola, and D. septemcinctus), and three subspecies of D. septemcinctus (D. s. septemcinctus, D. s. hybridus, and a new subspecies from Cordoba described here). Information on type material, diagnosis, distribution, and taxonomic comments for each taxon are provided. We designate a lectotype for D. novemcinctus; and a neotype for Loricatus hybridus (= D. septemcinctus hybridus).

Morphology of laryngeal cartilage of the nine-banded armadillo (Dasypus novemcinctus) Linnaeus, 1758.

Armadillos, Xenarthras representatives, known for adaptability to different ecosystems, own specific morphophysiological characteristics that are not known and deserve to be studied. The aim of this study was to describe the morphology of cartilage of the larynx of the nine-banded armadillo (Dasypus novemcinctus). Five dead armadillos were donated by the Chico Mendes Institute of Biodiversity (ICMBio-PI) to the Federal University of Piauí. The animals were fixed and dissected for removal of the larynx. The cartilages were identified and described, photodocumented, and schematized. Fragments with about 0.5 cm of each cartilage were collected and submitted to classical histology for Hematoxylin-Eosin coloring. The slides were assembled in enterlan and analyzed under a light microscope. The larynx of the armadillo (D. novemcinctus) is located in the mentonian region, ventral to the esophagus, and due to the total positioning of the tongue in the oral cavity, there is also a cranial cervical position in this species. The larynx has five cartilages, they are: a cricoid, a thyroid, an epiglottis, and two arytenoids. The corniculate process is present; however, the cuneiform process is absent. The epiglottis has a discrete bifurcation at its apex. In all cartilages epithelial variations are observed. The tissues are varied from squamoso stratified to cylindrical pseudostratified, with propria lamina rich in mucoserosas glands. With the exception of epiglottic cartilage, predominantly elastic, the rest are hyaline. The larynx of D. novemcinctus, although the same number of cartilages, differs morphologically and microscopically from the larynx of other species.

Methods for estimating the volume of the tympanic bulla in the big hairy armadillo Chaetophractus villosus (Mammalia, Xenarthra, Dasypodidae) / Métodos para la estimación del volumen de bula timpánica en el quirquincho grande Chaetophractus villosus (Mammalia, Xenarthra, Dasypodidae)

Two methods of measurement of bullar dimensions (callipers and scaling from digital images) and subsequent application of four volume formulae (rectangular prism, cylinder, ellipse and elliptical cone) were tested to find the most appropriate non-destructive method for estimating the bullar volume in Chaetophractus villosus. Material for the study consisted in clean adult skull (n=22). Real volume was obtained from latex casts of the tympanic bulla. Each estimation was corrected by a factor based on the differences between the estimated and the real volumes. Highest accuracy (5-7 % of underestimation) and precision (coefficient of variation: 13.27 %) were obtained from callipers and application of rectangular prism, cylinder and ellipse formulae. The corresponding correction factors were 0.31, 0.39 and 0.58, respectively.

Se evaluaron dos métodos para la obtención de medidas de la bula (calibre y escalado a partir de imágenes digitales), con posterior aplicación de cuatro fórmulas de volumen (prisma rectangular, cilindro, elipse y cono elíptico), a fin de hallar el método no destructivo más adecuado para el cálculo de volumen de bula en Chaetophractus villosus. El material de estudio consistió en cráneos limpios de individuos adultos (n=22). El volumen real fue obtenido a partir de moldes de látex de la bula timpánica. Cada estimación fue corregida mediante un factor basado en las diferencias entre los volúmenes reales y estimados. La mayor precisión (coeficiente de variación: 13,27 %) y exactitud (subestimaciones del 5-7 %) fueron obtenidas a partir de mediciones con calibre y aplicación de fórmulas de prisma rectangular, cilindro y elipse (factores de corrección: 0,31, 0,39 y 0,58, respectivamente).

Orientation selectivity in the visual cortex of the nine-banded armadillo.

Orientation selectivity in primary visual cortex (V1) has been proposed to reflect a canonical computation performed by the neocortical circuitry. Although orientation selectivity has been reported in all mammals examined to date, the degree of selectivity and the functional organization of selectivity vary across mammalian clades. The differences in degree of orientation selectivity are large, from reports in marsupials that only a small subset of neurons are selective to studies in carnivores, in which it is rare to find a neuron lacking selectivity. Furthermore, the functional organization in cortex varies in that the primate and carnivore V1 is characterized by an organization in which nearby neurons share orientation preference while other mammals such as rodents and lagomorphs either lack or have only extremely weak clustering. To gain insight into the evolutionary emergence of orientation selectivity, we examined the nine-banded armadillo, a species within the early placental clade Xenarthra. Here we use a combination of neuroimaging, histological, and electrophysiological methods to identify the retinofugal pathways, locate V1, and for the first time examine the functional properties of V1 neurons in the armadillo (Dasypus novemcinctus) V1. Individual neurons were strongly sensitive to the orientation and often the direction of drifting gratings. We uncovered a wide range of orientation preferences but found a bias for horizontal gratings. The presence of strong orientation selectivity in armadillos suggests that the circuitry responsible for this computation is common to all placental mammals.NEW & NOTEWORTHY The current study shows that armadillo primary visual cortex (V1) neurons share the signature properties of V1 neurons of primates, carnivorans, and rodents. Furthermore, these neurons exhibit a degree of selectivity for stimulus orientation and motion direction similar to that found in primate V1. Our findings in armadillo visual cortex suggest that the functional properties of V1 neurons emerged early in the mammalian lineage, near the time of the divergence of marsupials.

Gross Osteology, Radiographic and Computed Tomographic Morphology of the Axial Skeleton of the Nine-Banded Armadillo (Dasypus novemcinctus).

This study used 20 nine-banded armadillo, four in vivo and 16 cadavers, to describe the osteoarticular anatomy of the axial skeleton by means of digital radiography and computed tomography. Vertebral formula obtained in this sample specimens was seven cervical, 10 thoracic, five lumbar, nine vertebrae related to the synsacrum and 20-27 free caudal vertebrae. Peculiar features of this species were noted as the presence of xenarthrous processes in the caudal thoracic vertebra to the last lumbar vertebra, with prominent mammillary processes in the thoracolumbar segment, fused cervical vertebra from the second to fourth vertebra and the presence of synsacrum related to sacral and caudal vertebra fused to the pelvis. They are homodont animals presenting only molariform teeth with formula of 8/8, totalling 32 teeth. There was no complexity in the execution of radiographic and tomographic examinations, concluding that execution can be carried out in nine-banded armadillos during the clinical routine for wild animals.

Taxonomic revision of the Dasypus kappleri complex, with revalidations of Dasypus pastasae (Thomas, 1901) and Dasypus beniensis Lönnberg, 1942 (Cingulata, Dasypodidae).

Dasypus kappleri is the largest species of the genus Dasypus and is restricted to the Amazonian rainforest biome. Over the last century, related taxa have been described and synonymized without comprehensive analyses, and the current classification involving two subspecies, Dasypus k. kappleri and Dasypus k. pastasae, has never been revised. The aim of this work is to clarify the taxonomy of Dasypus kappleri through integrative morphological and morphometric analyses. We examined 70 specimens housed in scientific collections as well as photographs of the type specimens of five nominal taxa. Three methodologies (discrete characters, linear and geometric morphometrics) were employed. All results converged on the recognition of three allopatric groups, each with diagnostic qualitative and quantitative traits, that we recognize as full species: Dasypus kappleri Krauss, 1862, occurs in the Guiana shield; Dasypus pastasae (Thomas, 1901) is distributed from the eastern Andes of Peru, Ecuador, Colombia, and Venezuela south of the Orinoco River into the western Brazilian Amazon; and Dasypus beniensis Lönnberg, 1942, occurs in the lowlands of Amazonian Brazil and Bolivia to the south of the Madre de Dios, Madeira, and lower Amazon rivers. This revision raises to nine the number of living species of Dasypus.

Vertebral bending mechanics and xenarthrous morphology in the nine-banded armadillo (Dasypus novemcinctus).

The vertebral column has evolved to accommodate the broad range of locomotor pressures found across vertebrate lineages. Xenarthran (armadillos, sloths and anteaters) vertebral columns are characterized by xenarthrous articulations, novel intervertebral articulations located in the posterior trunk that are hypothesized to stiffen the vertebral column to facilitate digging. To determine the degree to which xenarthrous articulations impact vertebral movement, we passively measured compliance and range of motion during ventroflexion, dorsiflexion and lateral bending across the thoracolumbar region of the nine-banded armadillo, Dasypus novemcinctus Patterns of bending were compared with changes in vertebral morphology along the column to determine which morphological features best predict intervertebral joint mechanics. We found that compliance was lower in post-diaphragmatic, xenarthrous vertebrae relative to pre-xenarthrous vertebrae in both sagittal and lateral planes of bending. However, we also found that range of motion was higher in this region. These changes in mechanics are correlated with the transition from pre-xenarthrous to xenarthrous vertebrae, as well as with the transition from thoracic to lumbar vertebrae. Our results thus substantiate the hypothesis that xenarthrous articulations stiffen the vertebral column. Additionally, our data suggest that xenarthrous articulations, and their associated enlarged metapophyses, also act to increase the range of motion of the post-diaphragmatic region. We propose that xenarthrous articulations perform the dual role of stiffening the vertebral column and increasing mobility, resulting in passively stable vertebrae that are capable of substantial bending under appropriate loads.

Anatomy of Shoulder Girdle Muscle Modifications and Walking Adaptation in the Scaly Chinese Pangolin (Manis Pentadactyla Pentadactyla: Pholidota) Compared with the Partially Osteoderm-Clad Armadillos (Dasypodidae).

Because pangolins are unique mammals with a body and limbs almost entirely sheathed in hard keratinous overlapping scales and with digging and climbing abilities, the shoulder girdle muscles may differ significantly from those of other mammals including the partially osteoderm-clad armadillos. Therefore, we conducted a functional anatomical study of the shoulder girdle muscles in Chinese pangolins (Manis pentadactyla pentadactyla, Pholidota) and some armadillo species (Dasypodidae). Our CT scans revealed that the pangolin's overlapping scales are hard structures completely encasing the limbs. The armadillo's limbs, however, are covered with small relatively soft non-overlapping scales embedded in the skin, and articulate completely free of the hard osteodermal carapace. The attachments of some shoulder girdle muscles in the pangolin have moved from the surrounding edges of the scapula to the spine, and they, therefore, fully cover the scapula. In addition, some pangolin shoulder girdle muscles cross the shoulder joint to insert on the distal humerus, but this does not occur in armadillos. We cannot rule out the possibility that these muscle modifications represent adaptations for digging and/or climbing in pangolins. Our results and previous literature do not establish specific links between them and locomotive modes. However, we propose that the Chinese pangolin may use its derived muscular features when walking to move its armor-restricted forelimbs more effectively by swinging its head from side to side.

In vivo strains in the femur of the nine-banded armadillo (Dasypus novemcinctus).

The capacity of limb bones to resist the locomotor loads they encounter depends on both the pattern of those loads and the material properties of the skeletal elements. Among mammals, understanding of the interplay between these two factors has been based primarily on evidence from locomotor behaviors in upright placentals, which show limb bones that are loaded predominantly in anteroposterior bending with minimal amounts of torsion. However, loading patterns from the femora of opossums, marsupials using crouched limb posture, show appreciable torsion while the bone experiences mediolateral (ML) bending. These data indicated greater loading diversity in mammals than was previously recognized, and suggested the possibility that ancestral loading patterns found in sprawling lineages (e.g., reptilian sauropsids) might have been retained among basal mammals. To further test this hypothesis, we recorded in vivo locomotor strains from the femur of the nine-banded armadillo (Dasypus novemcinctus), a member of the basal xenarthran clade of placental mammals that also uses crouched limb posture. Orientations of principal strains and magnitudes of shear strains indicate that armadillo femora are exposed to only limited torsion; however, bending is essentially ML, placing the medial aspect of the femur in compression and the lateral aspect in tension. This orientation of bending is similar to that found in opossums, but planar strain analyses indicate much more of the armadillo femur experiences tension during bending, potentially due to muscles pulling on the large, laterally positioned third trochanter. Limb bone safety factors were estimated between 3.3 and 4.3 in bending, similar to other placental mammals, but lower than opossums and most sprawling taxa. Thus, femoral loading patterns in armadillos show a mixture of similarities to both opossums (ML bending) and other placentals (limited torsion and low safety factors), along with unique features (high axial tension) that likely relate to their distinctive hindlimb anatomy.

The correct name of the endemic Dasypus (Cingulata: Dasypodidae) from northwestern Argentina.

We show that Dasypus mazzai Yepes 1933 is a senior synonym of Dasypus yepesi Vizcaíno 1995. We present morphological evidence that the holotype of D. mazzai is not a juvenile of Dasypus novemcinctus or any other species of this genus, but a distinct endemic species from northwestern Argentina undistinguishable from D. yepesi. Therefore, the correct name for the long-nosed armadillo of intermediate size occurring in the Argentinean provinces of Jujuy and Salta is Dasypus mazzai Yepes 1933.