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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.

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. Fil: Basso, Ana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; Argentina Fil: Sidorkewicj, Nora Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; Argentina Fil: Casanave, Emma Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Ciencias Biológicas y Biomédicas del Sur. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia. Instituto de Ciencias Biológicas y Biomédicas del Sur; Argentina Fil: Mason, Matthew James. University of Cambridge; Estados Unidos

The possible producer and environmental setting of large meniscate burrows (Nagtuichnus meuleni igen. and isp. nov.) occurring in late Miocene and Holocene aeolian deposits from Argentina are discussed. These are unbranched burrows with an uniform meniscate filling that range in width from 46 to 78 mm. N. meuleni distinguishing features are a filling composed of a discontinuous, outer massive layer between a central meniscate core and the excavation boundary, sets of parallel ridges in the external wall, and a particular outline plus the presence of paired pits in the concave surface of menisci (or hollows in the convex surface). The late Miocene lower member of the Rio Negro Formation at La Loberia (Rio Negro province) is interpreted as aeolian dune, damp interdune and dry interdune deposits. The Holocene sediments from Gran Salitral (southwestern La Pampa province) represent aeolian dune, wet interdune and dry interdune deposits. N. meuleni occurs only in damp and dry interdune deposits. The composite ichnofabric produced by N. meuleni in the Holocene of the Gran Salitral is composed of two suites of trace fossils. A former Skolithos suite includes Skolithos linearis, Taenidium barretti, Polykladichnus aragonensis and root traces developed in lacustrine calcareous mudstone deposits (wet interdune). This suite is overprinted by N. meuleni, with subordinate participation of S. linearis and root traces, composing the Nagtuichnus suite. The later suite is developed in brown silt and sand of dry interdune areas. The Nagtuichnus ichnofabric is considered indicative of damp to dry interdune facies of late Miocene to Holocene age. The burrow systems of the likely producers of the Holocene N. meuleni structures were studied in the field and in the laboratory. The candidates were selected from the extant local fauna of the Gran Salitral, including southern cavies (Microcavia australis, Rodentia), tuco-tucos (Ctenomys azarae, Rodentia), and pink fairy armadillos or pichiciegos (Chlamyphorus truncatus, Xenarthra). The most likely producer of N. meuleni are pichiciegos because they have fully subterranean habits and insectivorous diet involving the production of long, unbranched, horizontal burrows excavated in sand, which are mostly backfilled. In contrast to this, tuco-tucos and southern cavies, which are herbivores that forage aboveground, use their more permanent burrows for dwelling and reproduction. As observed in a live, captive-kept C. truncatus, the meniscate structure of the fill can be explained by the animal packing the excavated sand with its rump plate. This mechanism also results in a massive layer of sediment in the burrow fill. Other significant bioglyphs that are a sort of fingerprint of pichiciegos are the outline of menisci in cross-section (mimicking their rump plate) and pairs of rounded pits in the concave surface of menisci (probably tail traces).

Despite having a moderately large distributional area, both the pink fairy armadillo (Chlamyphorus truncatus) and particularly the Chacoan fairy armadillo (Calyptophractus retusus), which are among the least known xenarthrans, appear to be rare or patchily distributed. Although low density in species with large range sizes has been associated with large body size, this is not the case for fairy armadillos. We propose that past climate variations may have caused their current low densities, and evaluate retractions and expansions of suitable areas of fairy armadillos by extrapolating the consensus of habitat suitability models fitted with current climatic conditions to past conditions. We found great variation in suitable area along time in both species, with a drastic reduction in the Last Interglacial (LIG) period when compared with current situation. Both the variations and the reduction during LIG were more pronounced in Calyptophractus than in Chlamyphorus. We postulate that past extreme reductions in suitable areas could cause a delay in the recovery of the populations, resulting in low densities despite climatic conditions during more benign times allowing a more widespread distribution. Fil: Torres, Ricardo Marcelo. Universidad Nacional de Cordoba. Facultad de Cs.exactas Fisicas y Naturales. Catedra de Div.animal Ii; Argentina Fil: Abba, Agustin Manuel. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Departamento Cientifico Zoologia Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Superina, Mariella. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; Argentina

The distribution and ecology of the pink fairy armadillo Chlamyphorus truncatus, the world’s smallest armadillo, are poorly understood due largely to the strictly subterranean habits of this species. We compiled records from the literature, museum and private collections, information from rural people, and researchers to update the species’ current distribution and conservation threats. Recent records suggest that populations of C. truncatus persist in localities along most of the species’ historical range, including at least 12 sites with recurrent pink fairy armadillo records. We added new registers outside the historical distribution; south of Mendoza province, north of Río Negro province and south of Buenos Aires province, effectively extending the species range. The rate at which new records are accrued has increased, arguably reflecting a greater interest in the species and greater presence of field workers in the species range. The conservation of the pink fairy armadillo depends on the maintenance of the arid and semiarid habitats where this species occurs, with commercial agriculture, pesticides, extensive livestock farming, and predation by domestic dogs and cats, posing the threats of greatest concern. La distributión y ecología del pichiciego menor, Chlamyphorus truncatus, el armadillo más pequeño del mundo, han sido poco estudiadas debido a los hábitos estrictamente subterráneos de la especie. Recogimos registros de la literatura, de museos y colecciones privadas e informatión provista por pobladores rurales e investigadores a los fines de actualizar la distribution actual de la especie y sus problemas de conservatión. Los registros recientes sugieren que las poblaciones de C. truncatus persisten en localidades a lo largo del rango de distributión histórica, incluyendo al menos 12 sitios con registros recurrentes de la especie. Agregamos nuevos registros fuera de su distribution histórica, al sur de la provincia de Mendoza, al norte de Río Negro y al sur de la provincia de Buenos Aires, extendiendo así el rango de distribution. La tasa de acumulación de nuevos registros ha incrementado en los últimos tiempos, lo cual refleja un interés creciente por la especie y un aumento de trabajos de campo en su rango de distribution. La conservation del pichiciego menor depende del mantenimiento de los hábitas áridos y semiáridos que ocupa. Las amenazas más preocupantes para la especie son la agricultura y ganadería extensiva, el uso de pesticidas y la depredation por animales domésticos. Fil: Borghi, Carlos Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina Fil: Campos, Claudia Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; Argentina Fil: Giannoni, Stella Maris. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina Fil: Campos, Valeria Evelin. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina Fil: Sillero-Zubiri, Claudio. University of Oxford; Reino Unido

Pink fairy armadillos, Chlamyphorus truncatus, are poorly known fossorial mammals that are endemic to central Argentina. These smallest of all extant armadillos are rarely observed in the field and extremely difficult to maintain under captive conditions. This case study describes the husbandry of a male pink fairy armadillo that was maintained in an artificial environment for 8 months. A stable, undisturbed environment consisting of abundant compact sand and hiding places on the surface was the key to its successful maintenance. The artificial diet consisted of a semiliquid mixture of ground cat food, insectivore diet, mashed banana, vitamins, and minerals. Any slight modification to its environment or diet triggered a stress response. Fil: Superina, Mariella. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; Argentina