Odontoalycus exoculo, Uusitalo, 2025

Odontoalycus exoculo sp. nov.

( Figs. 7A–D, 8A–F, 9A–F)

Description. Dorsum (n=1 tritonymph, Figs. 7A, B, 9A, B). Length 240 µm; integumental ridges densely covered by transverse lamellae (see Remark); holotrichous set of dorsal setae; ciliated setae with long shafts on microplates; setae slightly longer in caudal segments; prodorsum with filamentous sensilla ve, sci and slightly elongated setae in on prodorsal shield; ciliated setae vi, sce and exp on separate microplates; mutual distances of vi, ve and in equal; eyes absent; naso absent.

Venter ( Fig. 7D). Setae short with less than 10 cilia; 13–14 genital setae per valve; 2 anal setae per valve.

Gnathosoma ( Figs. 7C, 8E, F, 9C, D, F). Chelicera robust, non-elongated, with one pair of smooth cheliceral setae in dorsal position; movable chela with 10 pairs of teeth, subequal in size; fixed digit with a pair of large teeth; subcapitulum with 3 pairs of adoral setae; rutella toothpick-like; palpal tarsus with three pairs of pseudacanthoid eupathidia.

Legs ( Figs. 8A–D, 9B, 9E). Solenidial formula for tarsi, tibiae, genua and femora of legs I, II, III, and IV, respectively: 2-2-0-0, 2-2-2-0, 6-2-2-1, 6-1-0-0, both solenidia on tibia I are more like baculiform, some solenidia are awl-like, short and sharp, pestle-like famulus I and famulus II abaxially near claws; empodia clawless.

Type material. Several high-quality photos of 1 tritonymph from litter, Sian Ka’an , Quintana Roo , Mexico, 20 November 2014, María Magdalena Vázquez. The material will be deposited in the CNCA ( Colección Nacional de Acaros) at the Instituto de Biología at UNAM ( Universidad Nacional Autonóma de México), Mexico City .

Differential diagnosis. The species can be segregated from the other species of the tribe by having: an eyeless prodorsum; chelicera with ca. 20 tiny, beak-like teeth on the movable digit and one pair of massive teeth on the fixed digit; and a clawless empodia. Alycus share the robust and non-elongated chelicera, but differ by having a holotrichous dorsum.

Remark. The specimen is flattened, but transverse lamellae are visible in random places, indicated by white arrows in Fig. 9A.

Etymology. The specific name (Lat. exoculo ) refers to the absence of eyes.

Genus Pachygnathus Dugès, 1834

Type species: “ Pachygnathe velu ” Dugès, 1834 (= Pachygnathus villosus Dugès [in: Oken ], 1836 from France); by monotypy .

Differential diagnosis. The genus can be segregated from the other genera of the family by the beak-like chelicerae ( Fig. 10C), small, fork-like rutella ( Fig. 10D, Uusitalo 2010: fig. 58), and having less than six sparsely barbed eupathidia on the palpi ( Fig. 11I).

Remarks. The genera Alycus and Pachygnathus were sometimes considered synonymous during 19th and 20th centuries until the phylogenetic analysis of the family Alycidae revealed their belonging to distinct evolutionary lines ( Uusitalo 2010). Both old generic names were retained as valid, the name Pachygnathus has been applied to the group of species with long and beak-like chelicerae in the tribe Alycini .