CHACO NAKED-TAILED ARMADILLO Cabassous chacoensis FAUNA PARAGUAY

Cabassous chacoensis Wetzel 1980 Image Gallery
TAX: Class Mammalia; Subclass Theria; Infraclass Eutheria; Order Cingulata; Family Dasypodidae; Subfamily Tolypeutinae (Myers et al 2006). The genus Cabassous was defined by McMurtie in 1831 and contains four species, two of which are present in Paraguay. The genus was reviewed by Wetzel (1980). This species is monotypic (González 2001). The species name chacoensis refers to the Gran Chaco the eco-region to which this species is confined. Formerly placed in the Euphractinae, Möller-Krull et al (2007) provided DNA evidence that demonstrated their position within the Tolypeutinae. Synonyms adapted from Gardner (2007):
Xenurus gymnurus Lahille 1899:204 Not Tatus gymnurus Olfers (1818).
Cabassous loricatus Yepes 1935:441 In part. Not Cabassous loricatus (JA Wagner 1855)
Cabassous loricatus Cabrera 1959:219. In part. Not Cabassous loricatus (JA Wagner 1855)
Cabassous loricatus Moeller 1968:420. In part. Not Cabassous loricatus (JA Wagner 1855)
Cabassous chacoensis Wetzel 1980:335 Type locality "5-7km W of Est. Juan de Zalazar, Departamento Presidente Hayes, Paraguay"
ENG: Chaco Naked-tailed Armadillo, Chacoan Naked-tailed Armadillo (Redford & Eisenberg 1992, Canevari & Vaccaro 2007, Gardner 2007).
ESP: Cabasú chico (Canevari & Vaccaro 2007), Tatu de rabo molle (González 2001, Canevari & Vaccaro 2007).
GUA: Tatu ai menore (sic) (Redford & Eisenberg 1992).
DES: Cabassous armadillos have a short, broad snout and small eyes. The cephalic shield has an average of 38.7 scutes (range 34-42). Dorsal plates are arranged in transverse rows along the body and there are 12 movable bands. The third movable band has a mean of 28.3 scutes (range 27-30) and the fourth a mean of 26.7 scutes (range 25-29). There are very few, isolated scales on the cheek. Scutes of the movable bands are poorly differentiated from the rest of the dorsal scutes and are of a similar size and shape. The scapular and pelvic shields extend almost to the base of the limbs. First and second complete rows of scutes on the scapular shield wider than they are long. The first complete band of the scapular shield has a mean of 17.3 scutes (range 16-19) and the last a mean of 25.3 scutes (range 23-27). The first complete band of the pelvic shield has a mean of 25 scutes (range 24-26) and the last a mean of 6 scutes (range 5-7). Colour ranges from brown to dark brown, somewhat yellower laterally. There are no hairs present on the dorsal surface, though the lateral hairs may be fairly long. Ventrally greyish almost naked and only sparsely haired. The tail is fairly long and slender and lacks scales. This species is best identified by its short ears, well-separated from each other but not extending beyond the first complete band of the scapular shield when laid backwards. The pinna has a characteristically fleshy anterior edge. Both feet have five pale claws, those of the forefeet being particularly long, especially the central (third) one which is greatly elongated and sickle-shaped. (Wetzel 1980). DF: Teeth are peg-like. Dental formula 8/8=32. There are no teeth present in the premaxillary bone. Mandibular (lower) toothrow distinctly curved. Uniquely in this genus the anterior and posterior teeth are wider than they are long (they are constricted anteroposteriorly). Upper Tooth Row Length 25.2mm (+/-0.5); Lower Tooth Row Length 23.7mm (+/-0.7). Dimensions of Maxillary (Upper) Teeth (Length x Width): 4th=2.6 (+/-0.2) x 3.4 (+/-0.12), 5th=2.7 (+/-0.16) x 3.6 (+/-0.2), 6th=2.5 (+/-0.28) x 3.6 (+/-0.38), 7th=2.4 (+/-0.28) x 3.2 (+/-0.16); Dimensions of Mandibular (Lower) Teeth (Length x Width): 5th=2.6 (+/-0.38) x 3.2 (+/-0.15), 6th=2.6 (+/-0.16) x 3.3 (+/-0.26), 7th=2.4 (+/-0.19) x 3 (+/-0.33). (Wetzel 1980). CR: Rostrum short but skull proportionately broader than that of C.tatouay. Mandible narrow and distinctly curved on the dorso-ventral and medio-alteral axes. Condyloid process of mandible only slightly higher than coronoid process. Tympanic rings present rather than bullae. Ratio of palatal length to maxillary tooth row 1.62. Ratio of rostral length to postrostral length 0.8. Condylonasal length 69.8mm (+/-1.3); Rostral length 30.7mm (+/-0.8); Palatal length 41mm (+/-1.2); Postrostral length 38.9mm (+/-0.9); Palatal width 10.3mm (+/-0-9); Anterior rostral width 11.1mm (+/-0.9); Interlacrimal width 29.1mm (+/-1); Interorbital width 21.1mm (+/-0.9); Zygomatic width 40.1mm (+/-2.4); Mastoidal width 33.3mm (+/-1.6); Cranial height 29.9mm (+/-1.6). (Wetzel 1980).
TRA: This species walks supported by the claws of the forefeet while the entire sole of the hindfoot comes into contact with the substrate.
MMT: The smaller of the "naked-tailed armadillos" in Paraguay and indeed the smallest member of the genus. The following measurements were given by Wetzel (1980) taken from two specimens: HB: 30.3cm (30-30.6cm); TA: 9.3cm (9-9.6cm); FT: 6.1cm; EA: 1.45cm (1.4-1.5cm).
SSP: Cabassous armadillos are essentially smaller versions of Priodontes maximus, but size alone immediately rules out confusion with that species - no other armadillo even approaches Priodontes in size. They can be further identified by the lack of armoured plates on the tail (the tail is "naked") and the greatly enlarged claw on the forefeet. Highly-fossorial in behaviour these armadillos dig to escape danger - they do not try to run away. As a result of these distinctive features in Paraguay this species is only likely to be confused with the congeneric Cabassous tatouay. That is a larger species (approximately 50% larger than this species) and crucially has much longer ears that lack a fleshy expansion on the anterior margins. The long funnel-shaped ears of C.tatouay extend well above the top of the head (reaching beyond the first complete row of scapular scutes when laid backwards) and are quite different in length and form to the extremely short ears of this species. The two appear to be allopatric with this species confined to the Chaco and C.tatouay only recorded in eastern Paraguay. Note that this species has consistently smaller scale counts and cranial measurements than C.tatouay for all standard measurements used in the description. Cranially the curved mandible and anteroposteriorly constricted maxillary teeth are diagnostic of this species.
DIS: A restricted range species and Chaco endemic confined to western Paraguay and a small area of adjacent northern Argentina (Provincias Santiago del Estero and Formosa, and possibly also Tucumán). The species may occur in southwestern Bolivia and Matto Grosso do Sul, but its presence has not been confirmed in either of these countries. A specimen MACN4388 from Buenos Aires Zoo with supposed provenance "Brasil, Matto Grosso" was listed by Yepes (1935) as Cabassous loricatus but is actually this species and is the only evidence of its occurrence in that country. However Gardner (2007) suspected that the record was in error. Three Paraguayan specimens were examined by Wetzel (1980) MZ1600 with no locality data other than "Paraguay Chaco", USNM 531004 from Filadelfia, Departamento Boquerón and the type specimen CONN 16892 from 5-7km W of Estancia Juan de Zalazar, Departamento Presidente Hayes. The range of the species in Paraguay may be greater than is currently known, this being a secretive, largely subterranean species that is naturally rare and infrequently encountered owing to the isolated and inhospitable nature of its habitat.
HAB: Confined to xeric habitats of the Dry Chaco. The type specimen was taken in an area of thorn forest and mixed grasses. Given the subterranean nature of this species behaviour it may be assumed that soft soils are required for burrowing and coupled with the specilaised diet it is likely locally distributed.
ALI: No specific information is available on feeding behaviour of this species but it may be supposed to be myrmecophagous as are other members of the genus, using the long claws of the forefeet to break intoant nests and termite mounds.
REP: A single young is born (Canevari & Vaccaro 2007).
BEH: General Behaviour Almost nothing is known of the behaviour of this species other than the fact that it is highly fossorial and rarely observed. They are probably primarily nocturnal.
VOC: Handled males may give a pig-like grunting noise, but females are generally silent (Canevari & Vaccaro 2007).
HUM: This rarely recorded species probably passes undetected over most of its range, an area with a low human population.
CON: The Chaco Naked-tailed Armadillo is considered Near Threatened by the IUCN, click here to see their latest assessment of the species. The species is not listed by CITES. The population may have declined by as much as 25% over the last 10 years as a result of increased human activity in the species range. It is absent from cultivated areas and grazed areas, and the elimination of ant and termite populations in areas of anthropomorphic activity also directly affects the species. The species is easily captured and likely hunted opportunistically by human populations, though its small size and subterranean behaviour means that it is not a species that is deliberately sought. The species undoubtedly suffers predation from domestic dogs.
Citable Reference: Smith P (2008) FAUNA Paraguay Online Handbook of Paraguayan Fauna Mammal Species Account 25 Cabassous chacoensis.
Last Updated: 30 January 2009.
References:
Cabrera A 1958 - Catálogo de los Mamíferos de América del Sur - Revista Museo Aregntino de Ciencias Naturales Bernadino Rivadavia Zoology 4: p1-307.
Canevari M, Vaccaro O 2007 - Guía de Mamíferos del Sur de América del Sur - LOLA, Buenos Aires.
Gardner AL 2007 - Mammals of South America Vol 1: Marsupials, Xenarthrans, Shrews and Bats - University of Chicago Press, Chicago.
Lahille 1899 - Ensayo sobre la Distribución Geogràfica de los Mamíferos en la República Argentina - Primera Reunion Congreso Cientifica Latino America, Buenos Aires 3: p165-206.
Moeller W 1968 - Allometrische Analyse der Gürteltierschädel ein Beiträg zur Phylogenie der Dasypodidae Bonaparte, 1838 - Zool. Jahrb. Anat. 85: p411-528.
Möller-Krull M, Delsuc F, Churakov G, Marker C, Superina M, Brosius J, Douzery EJP, Schmitz J 2007 - Retroposed Elements and Their Flanking Regions Resolve the Evolutionary History of Xenarthran Mammals (Armadillos, Anteaters and Sloths) - Molecular Biology and Evolution 24: p2573-2582.
Myers P, Espinosa R, Parr CS, Jones T, Hammond GS, Dewey A 2006 - The Animal Diversity Web (online). Accessed December 2008.
Nowak RM 1991 - Walker´s Mammals of the World 5th Ed Volume 1 - Johns Hopkins, Baltimore.
Olfers I 1818 - Bemerkungen zu Illiger´s Ueberblick der Säugthiere, nach Ihrer Vertheilung über die Welttheile, Rücksichtlich der Südamerikanischen Arten p192-237 in Bertuch FI Neue Bibliothek der Wichtigsten Reisebeschreibungen zue Erweiterung der Erd - und Völkerkunde; in Verbindung mit Einigen Anderen Gelehrten Gesammelt und Herausgegeben - Verlage des Landes-Industrie-Comptoirs, Weimar.
Redford KH, Eisenberg JF 1992 - Mammals of the Neotropics: Volume 2 The Southern Cone - University of Chigaco Press, Chicago.
Wagner JA 1855 - Diagnosen Einiger Neuer Arten von Nagern und Handflüglern - Arch. Naturgesch. 11: p145-149.
Wetzel RM 1980 - Revision of the Naked-tailed Armadillos Genus Cabassous McMurtie - Annals of the Carnegie Museum of Natural History 49: p323-357.
Yepes J 1935 - Las Especies Argentinas del Género Cabassous (Dasypodidae) - Physis 11: p438-444.

ACKNOWLEDGEMENTS
Many thanks to Mariella Superina for assisting with obtaining some of the references used in the construction of this species account.