Arachnologische Mitteilungen 58

Arachnologische Mitteilungen / Arachnology Letters 58: 9-12 Karlsruhe, September 2019 Laniatores (armoured harvestmen) is the most diverse subor- der of Opiliones, with over 4200 living species (Kury 2017). These sometimes large and often spiny and/or tuberculate harvestmen are very rare as fossils. Six species are currently known from the fossil record (Dunlop et al. 2019) including one species described from Burmese amber (ca. 100 Ma), one in Baltic amber (ca. 44–49 Ma) and four in Dominican Republic amber (ca. 16 Ma). Noticeable at all of these de- posits so far is the lack of fossil juveniles. Most of our re- cent knowledge about the development of harvestmen was summarized by Gnaspini (2007), who drew on earlier stu- dies from the 1950s and 1970s. Comprehensive information about the ontogenetic series of modern laniatorids is primari- ly known from a few Neotropical species (e.g. Gnaspini 1995, Townsend et al. 2009), but Juberthie (1964) provided data for the European species Scotolemon lespesi Lucas, 1860 from the family Phalangodidae. Here we describe a new specimen of the previously repor- ted Baltic amber laniatorid Proholoscotolemon nemastomoides (Koch & Berendt, 1854) from the family Cladonychiidae, to- gether with a juvenile assigned here to cf. Proholoscotolemon sp. which could well be an immature stage of Koch & Berendt’s species. Previous interpretations of P. nemastomoides were re- viewed by Ubick & Dunlop (2005). In brief, the amber fossil was originally placed in a South American genus. The body of the holotype is largely obscured by a white film, but the pedipalps and distal parts of the legs are better preserved and allowed Ubick & Dunlop (2005) to establish a new, extinct genus, probably closely related to the European Holoscoto­ lemon Roewer, 1915 (Cladonychiidae).The new juvenile fossil reveals, for the first time, data about the ontogenetic series of extinct laniatorids. Material and methods The two specimens studied here originate from the private collection of Jörg Wunderlich, and bear the repository num- bers CJW BBF2568 (adult) and CJW BBF2545 (juvenile). Neither required further preparation or polishing and both were immersed in water to reduce refraction and photogra- phed using a Leica Z16 APO A stereomicroscope running the software package Leica Application Suite. Stacks of ca. 15–20 images were combined using Helicon Focus 6 and edited for brightness and contrast using Adobe Photoshop CS5. Interpretative drawings were made on a Leica M205C stereomicroscope with a camera lucida attachment, whereby some setae or tubercles were occasionally omitted to enhan- ce visibility of important characteristics. All measurements are in millimetres. Measured lengths may show some devia- tions due to the three-dimensional position of the inclusions within the amber matrix and average values are marked with an asterisk (*). Fossils were compared to extant harvestmen in the collection of the Museum für Naturkunde Berlin – pri- marily Holoscotolemon jaqueti Roewer, 1915 (Cladonychiidae) and Scotolemon terricola Simon, 1872 (Phalangodidae) – to the type of the amber species P. nemastomoides (Berendt collec- tion,Museum für Naturkunde Berlin), as well as the literature on extinct and Recent species (Koch & Berendt 1854, Ubick & Dunlop 2005, Briggs & Ubick 2007). Baltic amber is by some margin the most intensively stu- died fossil resin deposit and an overview of its age, geological setting and the plant and animal groups recovered here can be found in Weitschat & Wichard (2010). The sediments hos- ting the amber are conventionally dated to the Lutetian stage of the Eocene (e.g. Wolfe et al. 2016) or ca. 44–49 Ma. At that time Europe consisted of several landmasses, with the Baltic amber forest perhaps belonging to a more northerly area (Dunlop et al. 2018: Fig. 1). A tropical to subtropical Two laniatorid harvestmen (Opiliones: Cladonychiidae) from Eocene Baltic amber Christian Bartel & Jason A. Dunlop doi: 10.30963/aramit5804 Abstract. Two new specimens of laniatorid harvestmen (Opiliones: Laniatores) from Eocene (ca. 44–49 Ma) Baltic amber are described. One is clearly adult and assignable to Proholoscotolemon nemastomoides (Koch & Berendt, 1854) from the family Cladonychiidae. The second, smaller, specimen is treated as cf. Proholoscotolemon sp., but probably represents a juvenile instar of P. nemastomoides and allows us to infer at least part of the ontogenetic sequence for Baltic amber laniatorids. The juvenile differs from the adult in the relative size of the body, weaker pedipalpal spination and the absence of tarsomeres subdividing the tarsi at the ends of the legs. Of particular note is the presence of unbranched claws at the tips of legs III–IV. This was unexpected given that juveniles of extant cladonychiids usually have four to six branches on these claws; a condition also thought to be plesiomorphic for this, and some related families. Keywords: fossil, juvenile, Lutetian, Laniatores, ontogeny Zusammenfassung. Zwei Weberknechte (Opiliones: Laniatores: Cladonychiidae) aus Baltischem Bernstein (Eozän). Zwei neue Klauenkanker (Opiliones: Laniatores) aus dem Baltischen Bernstein des Eozäns (ca. 44–49 Mio) werden beschrieben. Ein deutlich adultes Tier kann der Art Proholoscotolemon nemastomoides (Koch & Berendt, 1854) aus der Familie Cladonychiidae zugeordnet werden. Ein zweites, kleineres Tier wird als cf. Proholoscotolemon sp. eingeordnet und ist wahrscheinlich ein Jungtier von P. nemastomoides . Dies erlaubt uns, die Ontogenese von Laniatores aus dem Baltischen Bernstein teilweise zu dokumentieren. Das Jungtier unterscheidet sich vom erwachsenen Tier in der relativen Größe des Körpers, in der geringeren Anzahl der Pedipalpendornen und in der Abwesenheit von Tarsomeren, welche die Tarsen an den Beinenden unterteilen. Eine Besonderheit sind die unverzweigten Krallen an den Beinspitzen III- IV. Dies ist ungewöhnlich, da Jungtiere von lebenden Cladonychiiden normalerweise vier bis sechs Zähnchen an den Krallen tragen; ein Merkmal, das für diese und einige verwandte Familien als plesiomorph angesehen wurde. Christian BARTEL: Freie Universität Berlin, Institut für Geologische Wissenschaften, Malteserstraße 74-100, D-12249 Berlin, Germany; E-mail: christian.bartel93@t-online.de Jason A. DUNLOP: Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, D-10115 Berlin, Germany; E-mail: jason.dunlop@mfn.berlin submitted 26.2.2019, accepted 11.5.2019, online 16.8.2019