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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.

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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.

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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.

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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.

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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.

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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).

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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.

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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).

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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.

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Se investigaron las diferencias sexuales en algunos de los elementos de la cintura escapular y del miembro anterior de Chaetophractus villosus (Desmarest, 1804) utilizando técnicas de morfometría geométrica. La muestra estuvo constituida por 15 escápulas (7 machos, 8 hembras) y 50 complejos húmero-ulna (24 machos, 26 hembras). No se detectaron diferencias de tamaño entre sexos para ninguno de los tres huesos. Sin embargo, se observaron diferencias de forma para el húmero y la ulna, con mayor desarrollo en las hembras de estructuras que favorecen el incremento de fuerzas internas o de las palancas internas relacionadas. En ellas, el húmero se caracterizó por una morfología general más robusta, con mayor desarrollo de la tuberosidad deltoidea, cabeza más esférica, mayores anchos intertubercular y epicondilar, y mayor desarrollo de las crestas supracondilares. Para la ulna se observó una curvatura más pronunciada a lo largo de su eje mayor, desplazamiento de la fosa lateral hacia caudal, olecranon de mayor desarrollo, e incisura troclear más profunda. Para ambos huesos, el análisis discriminante clasificó correctamente al total de los ejemplares de acuerdo al sexo. Un pequeño porcentaje de la varianza (5,2% para el húmero; 6,8% para la ulna) se debió a efectos alométricos. Las características morfológicas del húmero y la ulna de las hembras sugieren una ventaja fosorial sobre los machos, debido a una mayor fuerza estructural durante los movimientos involucrados en el cavado, al tiempo que se mantiene una gran estabilidad en las articulaciones del hombro y del codo.(AU)

Sexual differences in some of the components of the pectoral girdle and forelimb of Chaetophractus villosus (Desmarest, 1804) were investigated by means of geometric morphometrics. A total of 15 scapulae (7 males, 8 females) and 50 humeri-ulnae complexes (24 males, 26 females) were examined. No size differences were detected between sexes for any of the bones, but shape differences were found for the humerus and the ulna that enhance the in-forces or the related in-levers. Females had a more robust humerus, with an enlarged deltoid tuberosity, a more spherical head, higher tubercular and epicondylar widths, and more developed supracondylar crests. The ulna of the females was characterised by a more pronounced curvature along its main axis, a caudal displacement of the lateral fossa, a longer olecranon, and a deeper trochlear notch. For both bones, the discriminant analysis classified correctly all the specimens according to their sex. A small percentage of the variance (5.2% for the humerus; 6.8% for the ulna) was explained by allometry. The morphological traits found for the humerus and ulna of the females suggest an increased structural strength that could result in powerful digging strokes while keeping shoulder and elbow stabilisation, suggesting a fossorial advantage over males.(AU)

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Se investigaron las diferencias sexuales en algunos de los elementos de la cintura escapular y del miembro anterior de Chaetophractus villosus (Desmarest, 1804) utilizando técnicas de morfometría geométrica. La muestra estuvo constituida por 15 escápulas (7 machos, 8 hembras) y 50 complejos húmero-ulna (24 machos, 26 hembras). No se detectaron diferencias de tamaño entre sexos para ninguno de los tres huesos. Sin embargo, se observaron diferencias de forma para el húmero y la ulna, con mayor desarrollo en las hembras de estructuras que favorecen el incremento de fuerzas internas o de las palancas internas relacionadas. En ellas, el húmero se caracterizó por una morfología general más robusta, con mayor desarrollo de la tuberosidad deltoidea, cabeza más esférica, mayores anchos intertubercular y epicondilar, y mayor desarrollo de las crestas supracondilares. Para la ulna se observó una curvatura más pronunciada a lo largo de su eje mayor, desplazamiento de la fosa lateral hacia caudal, olecranon de mayor desarrollo, e incisura troclear más profunda. Para ambos huesos, el análisis discriminante clasificó correctamente al total de los ejemplares de acuerdo al sexo. Un pequeño porcentaje de la varianza (5,2% para el húmero; 6,8% para la ulna) se debió a efectos alométricos. Las características morfológicas del húmero y la ulna de las hembras sugieren una ventaja fosorial sobre los machos, debido a una mayor fuerza estructural durante los movimientos involucrados en el cavado, al tiempo que se mantiene una gran estabilidad en las articulaciones del hombro y del codo.

Sexual differences in some of the components of the pectoral girdle and forelimb of Chaetophractus villosus (Desmarest, 1804) were investigated by means of geometric morphometrics. A total of 15 scapulae (7 males, 8 females) and 50 humeri-ulnae complexes (24 males, 26 females) were examined. No size differences were detected between sexes for any of the bones, but shape differences were found for the humerus and the ulna that enhance the in-forces or the related in-levers. Females had a more robust humerus, with an enlarged deltoid tuberosity, a more spherical head, higher tubercular and epicondylar widths, and more developed supracondylar crests. The ulna of the females was characterised by a more pronounced curvature along its main axis, a caudal displacement of the lateral fossa, a longer olecranon, and a deeper trochlear notch. For both bones, the discriminant analysis classified correctly all the specimens according to their sex. A small percentage of the variance (5.2% for the humerus; 6.8% for the ulna) was explained by allometry. The morphological traits found for the humerus and ulna of the females suggest an increased structural strength that could result in powerful digging strokes while keeping shoulder and elbow stabilisation, suggesting a fossorial advantage over males.

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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.

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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.

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All xenarthrans known to date are characterized by having permanent teeth that are both high crowned and open rooted, i.e., euhypsodont, and with a type of hypsodonty different from that of the rest of Placentalia: dentine hypsodonty. Also, most xenarthrans lack enamel; however, its presence has been reported in the fossil armadillo Utaetus buccatus and in living Dasypus. Considering the divergence of Xenarthra from other eutherians that possessed enameled teeth, the absence of enamel is a derived character. Diverse specializations are known in the dentition of xenarthrans, but the primitive pattern of their teeth and dentitions is still unknown. Here, we describe the mandible and teeth of a fossil armadillo, Astegotherium dichotomus (Astegotheriini, Dasypodidae), from the early Middle Eocene of Argentine Patagonia, with teeth showing both true enamel and closed roots. It is the oldest xenarthran with mandibular remains exhibiting protohypsodonty and is therefore likely representative of ancestral cingulates and xenarthrans generally. Astegotherium supports a recent hypothesis based on molecular data that enamel loss occurred independently not only within xenarthrans but also within dasypodid armadillos.

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Although the growth and development of tissues and organs of extinct species cannot be directly observed, their fossils can record and preserve evidence of these mechanisms. It is generally accepted that bone architecture is the result of genetically based biomechanical constraints, but what about osteoderms? In this article, the influence of physical constraints on cranial osteoderms growth is assessed. Comparisons among lepidosaurs, synapsids, and archosaurs are performed; according to these analyses, lepidosaur osteoderms growth is predicted to be less energy demanding than that of synapsids and archosaurs. Obtained results also show that, from an energetic viewpoint, ankylosaurid osteoderms growth resembles more that of mammals than the one of reptilians, adding evidence to debate whether dinosaurs were hot or cold blooded.

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We describe Pliodasypus vergelianus gen. et sp. nov., a Dasypodini armadillo from the middle Pliocene of Venezuela (Vergel Member, San Gregorio Formation). Although scarce, the remains are remarkable because of their geochronologic proximity to the main phase of Great American Biotic Interchange (GABI). The cladistic analysis conducted reveals that Pliodasypus groups with Dasypus and both are sister taxa of Propraopus, whereas Anadasypus is at a basal position. With respect to the records of tribe Dasypodini, after its oldest representative (Anadasypus, middle and late Miocene), the chronologically subsequent form is Pl. vergelianus (middle Pliocene), followed by Dasypus bellus in higher northern latitudes (late Pliocene), and then by widespread occurrences in the Pleistocene of North America (D. bellus) and South America (Propraopus, Dasypus punctatus, and Dasypus novemcinctus). Thus, we infer that Dasypus differentiated in the late Pliocene at low latitudes in the northern South America. It leads to two alternative hypotheses of dispersal: (a) some early Dasypus remained cryptically in South America until the Pleistocene, whereas others dispersed to North America between 2.2 and 2.7 Ma, or (b) they dispersed to North America subsequently to the emersion of the Panamanian isthmus and D. bellus differentiated there; later, during the Pleistocene, D. bellus entered South America and experienced speciation. The same process of re-ingression has been proposed to other xenarthrans, breaking with the traditional assumption that the GABI was unidirectional.

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We analyzed the sperm characteristics of captive six-banded armadillos (Euphractus sexcinctus), by the assessment of sperm morphology, morphometry, and ultrastructure. In general, armadillo's ejaculates present more than 80% of sperm within the range considered normal for sperm morphology currently accepted for other mammals. Coiled tails (3.9%) and detached heads (2.8%) were the defects most frequently verified. The morphometric analysis revealed that the total length of six-banded armadillo sperm is 77.6±1.2µm, and the length of the tail is 64.7±1.1µm on average. They also present a big head that corresponds to 16.6% of the entire sperm. Through transmission electron microscopy, we identified the presence of electron lucent points into the nucleus and the presence of about 45 mitochondria spirals in the mitochondrial sheath midpiece as a peculiarity of the six-banded armadillo sperm.

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Middle ears of adult Chaetophractus villosus, C. vellerosus and Zaedyus pichiy were studied for qualitative and quantitative comparisons. A great similarity in the overall shape of the middle ear structures was observed in the three species. The well-developed auditory bulla was formed by the intimate fusion of the tympanic and entotympanic. Internally, a recessus meatus and a wide epitympanic recess extending dorsally into an epitympanic sinus were recognized. The petrosal promontorium, nearly triangular, was the most salient feature in the tympanic cavity. The auditory ossicles corresponded to the transitional middle ear type. The m. tensor tympani and the m. stapedius were conspicuous. The lack of a stapedial artery was confirmed in all cases. The tympanic area and middle ear ossicles were relatively larger in C. vellerosus than in the other two species. It is hoped that the results of the present paper coupled to the bullar hypertrophy found in a previous work will provide a significant basis for future functional studies on the hearing capabilities in the dasypodids.

Se estudió cualitativa y cuantitativamente la morfología del oído medio en adultos de Chaetophractus villosus, C. vellerosus y Zaedyus pichiy. Se observó una gran similitud en las estructuras del oído medio de las tres especies. La bula auditiva, bien desarrollada, se observó formada por la fusión del timpánico y entotimpánico. Internamente se pudo reconocer un recessus meatus y un amplio receso epitimpánico que se extendía dorsalmente en un seno epitimpánico. El promontorio, casi triangular, fue la estructura más notoria del interior de la cavidad timpánica. Los huesecillos auditivos correspondieron al tipo transicional. Se observó un gran desarrollo en los músculos tensor del tímpano y estapedial. Se confirmó la falta de una arteria estapedial en las tres especies. El área del tímpano y los huesecillos auditivos fueron relativamente más grandes en C. vellerosus que en las otras dos especies. Se espera que los resultados del presente trabajo, sumados a la hipertrofia de la bula timpánica reportada previamente, provean una base significativa para futuros estudios sobre la capacidad auditiva en los dasipódidos.

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