Sirocellus, Bartel & Dunlop & Giribet, 2023

Bartel, Christian, Dunlop, Jason A. & Giribet, Gonzalo, 2023, An unexpected diversity of Cyphophthalmi (Arachnida: Opiliones) in Upper Cretaceous Burmese amber, Zootaxa 5296 (3), pp. 421-445 : 423

Genus Sirocellus gen. nov.

urn:lsid:zoobank.org:act:EC139A74-F787-4577-9A7D-823A662E238F

Type species. Sirocellus iunctus sp. nov.

Etymology. A combination of the names of the modern genera Siro and Stylocellus . Masculine in gender.

Diagnosis. Body oval, completely granular dorsally as well as ventrally. Almost conical ozophores in the type 2 position. Chelicerae long and mostly smooth, with just a few granules or tubercles. Pedipalps long and rather thin. Legs robust and with a granular surface. Leg tarsi not subdivided, bearing a single smooth claw. Tarsus IV in males proximally with a large lamelliform adenostyle.

Remarks. Specimen GPIH05128 ( Fig. 1 ) is recognized as an adult male due to the presence of an adenostyle on tarsus IV ( Fig. 1C ) and due to the high degree of body sclerotization. The families Ogoveidae and Pettalidae can be excluded, in this case due to the absence of a large opisthosomal apophysis on the second sternite and of a modified anal region. The subtriangular anterior part of the body in combination with type 2 ozophores ( Fig. 1C, D ) is also found in modern members of the family Stylocellidae . However, a large lamelliform adenostyle situated proximally is not known from modern stylocellid genera. There it is often described as fringed or plumose and it is situated near the middle of the tarsus. The form and position of the adenostyle is in fact more alike those of most modern sironids or neogoveids, but this could be a plesiomorphic character for Cyphophthalmi not found in extant stylocellids. We choose to place this fossil in the family Stylocellidae , which better fits the biogeographic distribution of the family and corresponds with the overall habitus of the specimen. This fossil is, however, placed in a new genus due to its unique adenostyle in combination with other characters which are otherwise stylocellid-like.

Figures

FIGURE 1. Sirocellus iunctus gen. et sp. nov., male holotype (GPIH05128). A. Whole specimen, dorsolateral view. B. Same, ventrolateral view. C. Camera lucida drawing of A. D. Same of B. Abbreviations: ad, adenostyle; ch, chelicerae; fe, femur; mt, metatarsus; oz, ozophore; pa, patella; pp, pedipalp; ta, tarsus; ti, tibia; tr, trochanter; legs numbered from I–IV. Scale bars equal 1 mm (A, C, D) and 0.5 mm (B).