Lacinius erinaceus Staręga, 1966

Dunlop, Jason & Mitov, Plamen, 2009, Fossil harvestmen (Arachnida, Opiliones) from Bitterfeld amber, ZooKeys 16, pp. 347-375 : 368

¡ Lacinius erinaceus Staręga, 1966

Figs 27 , 31-32

Material. MB.A. 1661 (also bears the label “Ser. 12/12”), from Bitterfeld amber, probably from the site of the Goitsche open-cast Mine near Bitterfeld, Sachsen-Anhalt, Germany ; Palaeogene (Oligocene: Chattian).

Description. An almost complete, juvenile specimen ( Figs 27 , 31-32 ) in anterolateral view, obscured in places by bubbles within the matrix. Body compact, length c. 1.75 mm, maximum width of prosoma 1.20, of opisthosoma 1.25. Division into pro- and opisthosoma, and any sclerites making up the prosomal dorsal shield, poorly resolved. Ocular tubercle pronounced, width 0.33 mm, bearing seven spines; immediately in front of it three fairly prominent spines present. Further, generally smaller, spines located behind the ocular tubercle. Anterior margin of prosomal dorsal shield slightly recurved to accommodate the chelicerae. Proximal article only of chelicerae preserved, lacking details. Pedipalps short and robust, again proximal articles only preserved. Right (?)patella of pedipalp with at least three denticle-like spines. Legs relatively short. Femur, patella and tibia quite robust, compared to the more slender distal articles, and heavily ornamented with rows of thorns. Each row can be up to ten thorns on the tibiae. Thorns take the form of conical, sometimes slightly curving, tubercles, length c. 0.1 mm; typically ending in a short bristle or seta. Metatarsus with one to three thorns proximally, but distal region generally bearing setae only. Legs most complete on right side, but leg 2 here missing, apart from a proximal stub (?trochanter). Metatarsal–tarsal division in leg 3 unclear; tarsus distally subdivided. Leg 4 well preserved with podomere lengths (in mm): patella, 0.41; tibia, 0.76; metatarsus, 1.12; tarsus, 1.21. Tarsus divided into one long and nine shorter elements, ending distally in a single, curved claw. Opisthosoma lacks clear segmentation, but is ornamented, like the legs, with conical spines, longest towards the posterior margin of the opisthosoma. The microsculture is granulated. The spines on the body do not appear to form any sort of regular pattern. Ventral surface largely covered by emulsion, but ventrally directed spines also observed here on the leg coxae and opisthosoma.

Remarks. This remarkable, spiny fossil is clearly something new for the European amber fauna. Two features (cf. Martens 1978) – the stout thorns ending in setae on the legs (and to a lesser extent the body) and the presence of three prominent spines in front of the eyes ( Fig. 32 ) – indicate the extant genus Lacinius Thorell, 1876 . The original hand-written note from Manfred Moritz provisionally assigned it to this genus. The probably closely-related Odiellus Roewer, 1923 lacks such well-developed thorns on the legs. Three Recent species of Lacinius occur in Germany today. All are distributed throughout much of the country, although somewhat rarer in the north ( Blick and Komposch 2004). Interestingly, the extant central European species are notably less spiny than this Bitterfeld fossil. In gross morphology the new find is rather more like some extant species from the Mediterranean region (e.g. Lacinius insularis Roewer, 1923 ), and especially Lacinius erinaceus Staręga, 1966 from the Caucasus. Indeed we were unable to recognise any reliable or non-trivial characters – other than age – which could distinguish MB.A. 166 from L. erinaceus ( Figs 28-29 ). We concede that assigning older fossils to living species is controversial, but note again the precedent from the slightly younger Dominican Republic amber (see Age of the inclusions) and tentatively refer this new Bitterfeld harvestman to L. erinaceus . The highly spinose Lacinius morphs were clearly more widely distributed during the Oligocene and occurred further north than their distribution today.

Figures

Figures 27-30. 27 Fossil?Lacinius erinaceus Staręga, 1966, MB.A. 1661, from Bitterfeld amber (Palaeogene: Oligocene) 28-29 Recent male Lacinius erinaceus Staręga, 1966 (Holotype) in dorsal and lateral view for comparison, revealing an almost identical morphology to the amber fossil 30 Leiobunum longipes Menge, 1854 from Bitterfeld amber, MB.A. 1662. Scale bars equal 1.0 mm.

Figures 31-33. Camera lucida drawings of the specimens shown in 27 and 30. 31?Lacinius erinaceus Staręga, 1966, MB.A. 1661 32 the same detail of ocularium and its spination 33 Leiobunum longipes Menge, 1854, MB.A. 1662. Both from Bitterfeld amber (Palaeogene: Oligocene). Scale bars equal 1.0 mm (31, 33).