Phalangiidae, Latreille, 1802

BARTEL, CHRISTIAN & DUNLOP, JASON A., 2023, First eupnoid harvestmen (Arachnida: Opiliones: Eupnoi) from mid-Cretaceous Kachin amber, with notes on sexual dimorphism in Halitherses grimaldii (Arachnida: Opiliones: Dyspnoi), Palaeoentomology 6 (3), pp. 278-291 : 284-285

Phalangiidae indet. 2

( Fig. 5 )

Material. coll. Patrick Müller, BUB3111.

Locality and horizon. Burmese amber, Hukawng Valley, Kachin State Myanmar; mid-Cretaceous.

Description. Body small and circular, L 0.95, anterior W 0.70, maximum posterior W 0.89. Pro-, meso- and metapeltidium borders equivocal. Ocularium equivocal ( Fig. 4A, C ). Chelicerae relatively small and covered with few setae on the distal segment ( Fig. 4B, D ). Cheliceral basal segment L 0.19; distal segment L 0.12, with fixed and movable finger (L 0.08). Pedipalps setose. Pedipalp tarsus elongated with a small and smooth claw on its tip ( Fig. 4B ). Pedipalp length: tr 0.13, fe 0.19, pa 0.14, ti 0.09, ta 0.37, total (tr–ta) 0.92. Legs extremely long (leg II and IV longest) and covered with somewhat spiny setae on femur and patella. Metatarsus and tarsus covered with thin (sensory) setae. Additionally, leg coxa, trochanter and femur covered with small granules. Tarsus I–IV bear a single smooth claw. Tarsal formula: 17–18:?:16:16+. Leg length: Leg I cx 0.20, tr 0.12*, fe 0.87, pa 0.24, ti 1.15, mt 0.79, ta 2.56, total (cx–ta) 5.93; Leg II cx 0.33, tr 0.15*, fe 1.60, pa 0.44, ti 2.88, mt?, ta?, total (cx–ti) 5.40; Leg III cx 0.38, tr 0.16*, fe 0.90*, pa 0.25, ti 1.08, mt 0.96, ta 2.56, total (cx–ta) 6.29; Leg IV cx 0.49, tr 0.14, fe 1.32, pa 0.24, ti 1.36, mt 1.2, ta 3.68, total (cx–ta) 8.43.

Ventral prosoma (and coxae) partly covered with larger spines ( Fig. 4B, D ). Sternites with rows of granules. Anal plate rounded, L 0.10, W 0.17.

Remarks. Another specimen, BUB3111 ( Fig. 5 ) is also a juvenile, due to its small body size and high number of relatively long sensory hairs on the straight pedipalp tarsus. The equivocal nature of the ocularium in this fossil makes it difficult to reliably place it within one of the Eupnoi families. Nevertheless, the small chelicerae, long legs, smooth pedipalp claw and the elongated pedipalp tarsus are typical phalangiid features. In addition, the family Caddidae can be excluded, due to the lack of large spines or apophyses on the pedipalps. Therefore, the fossil is also tentatively placed within the family Phalangiidae . We must also entertain the possibility that BUB4516 and BUB3111 belong to the same species, but represent different developmental stages. BUB3111 is ca. 10% smaller, has a more compact body and, oddly, bears a higher number of tarsomeres on legs I, III and IV. The pedipalps of both specimens are also relatively similar, except that BUB3111 features more pronounced sensory setae on all segments. Unfortunately, it is again impossible to reliably place this specimen in a genus as most of its important characters are not preserved and may not even be fully developed.

Figures

FIGURE 4. BUB4516 Phalangiidae indet. 1. A, Dorsal overview (camera lucida drawing). B, Close-up of the body in dorsal view. C, Close-up of the body in ventral view. Abbreviations: ch, chelicerae; cx, coxa; fe, femur; mt, metatarsus; oc, ocularium; pa, patella; pp, pedipalp; ta, tarsus; ti, tibia; legs numbered from I–IV. Scale bars = 1.0 mm (A) and 0.5 mm (B, C).

FIGURE 5. BUB3111 Phalangiidae indet. 2. A, Close up of the chelicerae and pedipalps in dorsal view. B, Close-up of the ventral body. C, Camera lucida drawing of the dorsal body. D, Camera lucida drawing of the ventral body. Abbreviations: ch, chelicerae; fe, femur; mt, metatarsus; pa, patella; pp, pedipalp; ta, tarsus; ti, tibia; legs numbered from I–IV. Scale bars = 0.25 mm (A, B) and 1.0 mm (C, D).