Cabassous chacoensis Wetzel, 1980 Chacoan naked-tailed armadillo Xenurus gymnurus: Lahille, 1899:204. Not Tatus gymnurus Olfers 1818: 220. Cabassous loricatus: Yepes, 1935:441. Part; not Cabassous loricatus J. A. Wagner, 1855: 174-176. Cabassous loricatus: Cabrera, 1958:219. Part; not Cabassous loricatus J. A Wagner, 1855. Cabassous loricatus: Moeller, 1968:420. Part; not Cabassous loricatus J. A. Wagner, 1855. Cabassous chacoensis Wetzel, 1980: 335. Type locality: “ Paraguay, Depto. Presidente Hayes, 5-7 km W Estancia Juan de Zalazar ”. Types. The holotype (CM 67067) is an adult male collected on 28 July 1974, no collector listed, original numbers PWM 247 and UCM [originally cited as CONN] 16891. It consists of a stuffed skin, skull, and a carcass preserved in alcohol. Wetzel (1980) listed two paratypes: an adult (CONN 16982) female [erroneously cited as male in the original publication] collected in the type locality, catalog number PWM 246; and a male (USNM 531004) collected in Filadelfia, Boquerón, Paraguay. Type locality. The holotype was collected at “ 5-7km W of Estancia Juan de Zalazar, Departament Presidente Hayes, Paraguay ” (Wetzel 1980), in an area of thorn forest and mixed grasses in the dry Chaco. Diagnosis. This species can be easily differentiated from other congeneric taxa by its much smaller ears (Figure 6), limbs and sides of the body hairy, and its overall smaller size (Table 2). The scutes on the cephalic shield (45-52) exhibit a concentric organization with a large and central scute surrounded by smaller polygonal scutes (Figure 6). The cheek region is usually naked or with very small scutes. The carapace is brownish with 11-13 movable bands and hairy on its edges. The tail is overall naked with only sparse scutes and hairs. C. chacoensis exhibits wide and marked curved zygomatic arcs, its teeth are anteroposteriorly constricted, making them wider than long. The body of the mandible is well curved and the ramus shows a more vertical profile (Figure 4d). Geographic distribution. Cabassous chacoensis occurs from western Paraguay to central Argentina, comprising mainly the Gran Chaco region. However, given that the species is rarely recorded (Chebez 1994), its range may be larger than it is currently known. For example, some isolated records in Argentina also include the Yungas (Cirignoli et al. 2019) and montane grassland High Monte in La Rioja (Monguillot & Miatello 2010). Wetzel (1980) listed Brazil (“ Mato Grosso ”) as part of the distribution of Cabassous chacoensis, but this was based on a specimen obtained from the Buenos Aires Zoo in 1904. Since then, no additional record has been reported, leading several authors to not include it as part of the Brazilian fauna (Wetzel et al. 2008, Hayssen 2014b, Brandão et al. 2019; Abreu et al. 2020; Quintela et al. 2020). Nevertheless, C. chacoensis has been registered in Paraguay about 220 km from the Brazilian border. It is therefore an open question whether the species went locally extinct, has gone unnoticed for over a century, or never occurred in Brazil; in this latter case the Paraguay River might represent the barrier between the two countries. On the other hand, the absence of C. chacoensis in Bolivia might reflect the lack of studies on this genus given that the dry Chaco extends northward to the Bolivian east portion (Figure 8). Among all specimens of Cabassous examined in this study, only three were collected in Bolivia. Remarks. Hutterer & Peters (2010) listed an adult female (ZFMK 60.317, field number 448) housed at the Zoologisches Forschungsmuseum Alexander Koenig, Bonn, Germany as a paratype of C. chacoensis. This specimen is represented by a skin and skull and was collected in Filadelfia, Boqueron, Paraguay by J. Unger on 10 December 1958. However, although Wetzel (1980) listed this individual among the material examined, he did not include it as a paratype.

Published as part of Feijó, Anderson & Anacleto, Teresa Cristina, 2021, Taxonomic revision of the genus Cabassous McMurtrie, 1831 (Cingulata Chlamyphoridae), with revalidation of Cabassous squamicaudis (Lund, 1845), pp. 47-78 in Zootaxa 4974 (1) on pages 60-61, DOI: 10.11646/zootaxa.4974.1.2, http://zenodo.org/record/4773355