First eupnoid harvestmen (Arachnida: Opiliones: Eupnoi) from mid-Cretaceous Kachin amber, with notes on sexual dimorphism in Halitherses grimaldii (Arachnida: Opiliones: Dyspnoi) Author BARTEL, CHRISTIAN Author DUNLOP, JASON A. text Palaeoentomology 2023 2023-06-28 6 3 278 291 http://dx.doi.org/10.11646/palaeoentomology.6.3.11 journal article 10.11646/palaeoentomology.6.3.11 2624-2834 8209319 339DF6C2-7D16-4BAC-9428-B741F557717C Species Halitherses grimaldii (?) Giribet & Dunlop, 2005 ( Fig. 6 ) Material. MB .A.4458 (ex coll. Jörg Wunderlich, F2723). Locality and horizon. Burmese amber, Hukawng Valley, Kachin State , Myanmar ; mid-Cretaceous. Description. Body oval and dorsally completely ornamented, L 1.38. Prosoma dominated by an extremely large, strongly ornamented and bilobed ocularium, L 0.34, W 0.62 ( Fig. 6A ). Eye lenses also very large (eye lens diameter 0.22). Dorsal segments fused into scutum parvum with free metapeltidium. Chelicerae moderately sized, distal segment with a dorsal, claw-like and curved apophysis proximally (apophysis L 0.09) ( Fig. 6B–D ). Distal segment additionally covered with a few small setae. Cheliceral fingers bearing small spines or thicker setae distally. Cheliceral basal segment L?, distal segment L 0.23, finger L 0.19. Pedipalps long and slender. Pedipalp tarsus and tibia covered with numerous clavate glandular setae. Pedipalp tarsus lacks terminal claw ( Fig. 6B, D ). Pedipalp length: tr 0.26, fe 1.16, pa 0.52, ti 0.50, ta 0.42, total (tr–ta) 2.86. Legs extremely long and slender. Leg femur sparsely covered with small spines ( Fig. 6A ). Coxa strongly ornamented ( Fig. 6C ). Tarsus I–IV subdivided, ending in a single claw. Leg length: Leg I cx 0.55, tr 0.18, fe?, pa?, ti?, mt?, ta?; Leg II cx 0.66, tr?, fe?, pa?, ti?, mt?, ta?; Leg III cx 0.74, tr 0.18, fe 6.33, pa 0.92, ti 4.83, mt?, ta?, total (cx–ti) 13; Leg IV cx 0.82, tr 0.23, fe 7.50, pa 0.83, ti?, mt?, ta?, total (cx–pa) 9.38. FIGURE 6. Halitherses grimaldii (?) MB.A.4458. A , Dorsal overview. B , Ventral overview. C , Ventral close-up of the body and chelicerae (apophyses arrowed). D , Camera lucida drawing of the ventral body, inset shows close-up of the cheliceral apophyses. Abbreviations: ap, apophysis; ch, chelicerae; fe, femur; go, genital operculum; oc, ocular tubercle; pa, patella; pp, pedipalp; ta, tarsus; ti, tibia; legs numbered from I–IV. Scale bars = 0.5 mm ( A , B ), 0.25 mm ( C ), 1.0 mm ( D ) and 0.3 mm ( D inset). Genital operculum subcircular and ornamented, L 0.24, W 0.21 . Ventral area between leg coxae I highly setose . Remarks. MB.A.4458 ( Fig. 6 ) can easily be identified as a member of the extinct genus Halitherses Giribet & Dunlop, 2005 , due to the presence of extremely large eyes dominating the prosoma ( Fig. 6A ), slender legs and pedipalps, an ornamented carapace, and the absence of a pedipalp claw ( Fig. 6B, D ). The specimen described herein is the smallest representative of the genus discovered so far and could, therefore, represent a juvenile. Nevertheless, for the first time a claw-like and curved apophysis can be observed proximally on the second cheliceral segment ( Fig. 6B–D ) and is a significant observation as potential evidence for secondary sexual dimorphism (see Discussion).