Arachnologische Mitteilungen 58

12 C. Bartel & J. A. Dunlop Discussion Postembryonic development has been documented for only a few modern harvestman (reviewed by Gnaspini 2007), with a proposed sequence of egg, larvae, up to eight nymphs (the last called the subadult), plus an adult. In living laniatorids the main ontogenetic changes are an increase in the armature of the pedipalps and increasing numbers of tarsomeres (e.g. Gnaspini 2007, Townsend et al. 2009). These trends are re- flected in the juvenile fossil described here. Its body is rather small and rounded in relation to the legs, and there are no signs of free tergites at the back of the opisthosoma as would be expected in the eventual scutum magnum condition. The position and form of the ocularium and chelicerae in the ju- venile fossil are almost identical to that in the adult amber laniatorids. The juvenile already has spiny pedipalps, but the exact number of spines differs on each limb article compared to the adult. The juvenile bears one to eight spines less per article of the pedipalp, except on the tarsus where the num- ber of spines is similar to the adult condition. The tarsus is undivided which together with the weak pedipalp spination and the fact that the body length is less than a quarter of the probable adult length may hint that this is an earlier juvenile stage as opposed to a late stage or subadult. We are not awa- re of any detailed comparative studies covering all immature life stages within Cladonychiidae, but an illustration of the pedipalp (with almost no spination) in a juvenile European harvestman Scotolemon lespesi Lucas, 1860 from the Grassato- res family Phalangodidae by Juberthie (1964: fig. 27) suggests that the amber fossil may be at a later stage rather than a recently hatched juvenile. Of particular interest is the condition of the legs and their claws. The juvenile described here (CJW BB F2545) shows strong leg spination, with a regular spine pattern on all metatarsi. By contrast, the putative adult bears mostly smooth legs with only small, sparse setae on the tarsi. We are not aware of reports of legs being spinier in juvenile la- niatorids as compared to adults. Another unexpected detail relates to the tarsal claws.The smooth, unbranched claws of legs III–IV of the juvenile in amber are somewhat similar to the adult condition, although it should be stressed that the claws in the adult are essentially branched and Y-shaped. By contrast, modern juveniles of cladonychiids (and some other insidiatorid families) usually bear complex claws on legs III–IV with four to six side branches (Ubick & Dunlop 2005, Briggs & Ubick 2007): the family name Cladonychi- idae literally means “branched claw”. The presence of these side-branches, retained in at least the juvenile stages of In- sidiatores, has been used to infer that this is a plesiomorphic condition for these harvestmen. An immature Eocene cla- donychiid which does not have side branches on its claws may draw this hypothesis into question. Alternatively, if it is the juvenile of Proholoscotolemon ne­ mastomoides it may be possible to define the fossil genus on having the unusual character of unbranched claws on legs III and IV throughout its life cycle. We should also entertain the possibility that the paired claws in the amber juvenile are fused at the base – in which case they could be considered branched – or that if the claws are separate at the base then the fossil may instead belong to Grassatores. The available resolution of the fossil does not allow us to investigate this further. It would also be useful to have comparative studies into claw ontogeny in the probably closely-related modern genus Holoscotolemon , but this data is not currently available in the literature. Acknowledgements We thank Jörg Wunderlich for making the new material available, Anke Sänger for technical assistance in taking the photos, and Darrell Ubick, Christian Komposch and Amanda Cruz Mendes for valuable comments on an earlier version of the manuscript. References Briggs TS & Ubick D 2007 Cladonychiidae Hadži, 1935 In: Pinto- da-Rocha R, Machado G & Giribet G (eds.) Harvestmen: the biology of Opiliones. 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