1♂, 1♀, Desierto de las Palmas, Benicassim, Castellón Province, Spain, 40°04’18’’ N, 0°01’02’’ E, 19-II-2017, 473 m, E. Recuero, P.C. Rodríguez, D. Osca leg.;

1♀, Saelices, Cuenca Province, Spain, 39°52’11” N, 2°47’09” W, 18-III-2019, 856 m, E. Recuero & P.C. Rodríguez leg. (Fig. 1a,b).

The species is present in the Desierto de las Palmas coastal mountains in Castellón. These small mountains, with a maximum elevation of 711 m, are geologically complex, with alternating siliceous and calcareous soils, including Palaeozoic slates, Triassic red sandstone and Mesozoic limestone (Sos Baynat, 1929; Vera, 2004). We found the species under a calcareous stone, in a small, young grove of Pinus halepensis Mill. with dense undergrowth formed by Pistacia lentiscus L., Quercus coccifera L. and Chamaerops humilis L. This population is about 160 km North of the Sierra de Aitana population in Alicante. Between these two localities there are many areas with suitable habitat for the species, so it is possible that its presence will be detected with more sampling effort.

More recently we have found the species to live in the Iberian Central Plateau. In this case it lives in a Quercus ilex L. forest on Jurassic and Cretaceous sandstones (Vera, 2004), and it was sampled in humid leaf litter. This locality is particularly interesting, as it is almost midway from every other known area occupied by Armadillidium mateui: about 200 km North of the nearest south-eastern population, 300 km South of the population from Navarra, and 250 km West of the Mediterranean localities.

The new localities increase considerably the known distribution of this Iberian endemic, and indicate a potential distribution much larger than previously expected over the eastern half of the Iberian Peninsula. Its presence in Sierra de Aitana, Desierto de las Palmas and Saelices, all of them part, or near, the Sistema Ibérico Mountain Range, suggests that the range of Armadillidium mateui could extend along these mountains into northern Spain, supporting the correct identification of the material from Navarra (Cifuentes, 1984).

The distribution of Armadillidium mateui as we know today seems largely disjunct, although the absence of records from large areas in the eastern Iberian Peninsula is probably a result of the scarcity of faunistic studies on terrestrial isopods. Alternatively, observed disjunct distribution could be real and consequence of range expansions and contractions following cyclic Pleistocene climatic changes as have been shown in many Iberian taxa (e. g. Sánchez-Montes et al., 2019 and references therein). Also, it seems that the species could be locally uncommon. Our observations, and most published records, are based in isolated individuals, in our case collected superficially in the soil. However, Jiménez-Valverde et al. (2015), sampling the deep colluvial Mesovoid Shallow Substratum, found the species to be abundant in the Sierra de Aitana mountains. This could indicate that, more than rare, the species may be difficult to collect. Combining different sampling techniques would provide more records and a better knowledge on the species abundance.