Stylocellidae, Hansen & Sorensen, 1904

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 : 432-433

Stylocellidae gen. sp. 3

Fig. 9

Material. Specimen BUB3653, ex coll. Patrick Müller; Myanmar, Hukawng Valley; Burmese amber, Upper Cretaceous (Lower Cenomanian).

Description. Body oval, total L 2.32, maximum opisthosomal W 1.23. Ozophores equivocal. Chelicerae rather short, its distal segment ornamented with small tubercles ( Fig. 9A–B ); basal segment L?, median segment L 0.36, distal segment L 0.18. Pedipalps moderately long; tarsus bearing a small claw on its tip and furnished with a few sensory setae; pedipalp length: tr?, fe?, pa?, ti 0.34, ta 0.27. Legs long, robust and finely granular; tarsi with a single smooth claw and additional setae; tarsus IV not subdivided, bearing a lamelliform proximal adenostyle; leg lengths: I tr 0.21, fe 0.43*, pa 0.23, ti 0.49*, mt 0.30, ta 0.41, total 2.07; II tr 0.20, fe 0.46, pa 0.14, ti 0.37, mt 0.30, ta 0.43, total 1.90; III tr 0.16, fe 0.41, pa 0.18, ti 0.42*, mt 0.28, ta 0.37, total 1.82; IV tr 0.23, fe 0.52, pa 0.18, ti 0.34, mt 0.36, ta 0.34, total 1.97. Gonostome equivocal. Opisthosomal sternites completely granular. Sternites 2–3 fused into a plate; sternites 4–8 free, their widths: 4, 0.98; 5, 0.93; 6, 0.82; 7, 0.64; 8, 0.52. Opisthosomal sternal sulci straight and parallel to each other. Anal plate rounded and unmodified ( Fig. 9B ).

Remarks. Specimen BUB3653 ( Fig. 9 ) is interpreted as an adult male as it bears an adenostyle on tarsus IV and seems heavily sclerotized. The habitus, in combination with an ornamented second cheliceral segment and free sternites, indicates stylocellid affinities. Additionally, typical pettalid or ogoveid characters, like a modified anal region or opisthosomal apophyses, are missing. The proximal position of the adenostyle ( Fig. 9A–B ) is somewhat similar to that observed in specimen GPIH05128 and is thus more typical for modern sironids or neogoveids. However, specimen GPIH05128 features a much larger and lamelliform adenostyle and a longer tarsus IV. Due to the lack of important dorsal and ventral characteristics which could not be reconstructed with the help of micro-CT ( Fig. 9C ), this fossil cannot be placed any further in the family Stylocellidae . Nevertheless, this is another interesting specimen showing a possible combination of sironid and stylocellid affinities and it is available for further studies.

Figures

FIGURE 9. Stylocellidae gen. sp. 3 (male specimen BUB3653). A. Whole body, ventral view. B. Camera lucida drawing of A. C. 3D reconstruction of whole body, ventral view. Abbreviations: ad, adenostyle; ch, chelicerae; pp, pedipalp; legs numbered from I–IV. Scale bars equal 1 mm.