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 .