Lacinius bizleyi, Mitov & Dunlop & Penney, 2015

Mitov, P. G., Dunlop, J. A. & Penney, D., 2015, A new species of Lacinius in amber (Arachnida: Opiliones), Fossil Record 18 (1), pp. 37-42 : 38-40

Lacinius bizleyi sp. nov.

Figs. 1–2

2009? Lacinius erinaceus (Star˛ega, 1966; Dunlop and Mitov, 368–369; Figs. 27, 31–32 – misidentification)

Type material. Holotype, Museum für Naturkunde Berlin, MB.A. 1661.

Type locality and horizon. From Bitterfeld amber, Saxony-Anhalt, Germany. Palaeogene (?Oligocene). Described in detail by Dunlop and Mitov (2009).

Additional material. MB.A. 2815 (ex D. Penney coll., via J. Damzen). Baltic amber; precise locality not recorded, but most of the recently acquired material stems from the Kaliningrad region of the Russian Baltic coast. Palaeogene (Eocene: Lutetian).

Derivation of name. In honour of the British palaeoartist Richard Bizley (Lyme Regis) for his assistance to D. Penney with various palaeontology-related projects.

Diagnosis. Species of Lacinius with a combination of ornamented body and leg articles (except tarsi) with numerous long sharp-pointed/tipped thorns, and distinct apophyses on both the patella and tibia of the pedipalp; patellar apophysis longer than tibial apophysis.

Description of MB.A. 2815. Relatively complete specimen (right leg II mostly missing), best seen in dorso–lateral view ( Figs. 1–2 ). Body oval, flattened, length ca. 1.2 mm; maximum width of prosoma ca. 1.0 mm, of opisthosoma ca. 0.9 mm. Ocularium raised and ornamented with at least five curving thorns (whereby thorns here have a thick base and then taper about midway along their length into a sharp spine); ocularium length and width ca. 0.14 and 0.23 mm respectively, distance from front of carapace ca. 0.2 mm. Distinct pattern of triad of forward-projecting spines immediately in front of ocularium ( Figs. 1a , 2b ). Opisthosoma, particularly the posterior portion, ornamented with numerous backwards-pointing thorns, each consisting of a thicker base with a short, stiff seta at the tip. Chelicerae equivocal. Pedipalps with distinct apophyses projecting from both patella and tibia ( Figs. 1a , 2b ). Palpal femur disto-medial with one setose, apophysis-like protrusion. Patellar apophysis long, somewhat spatulate – almost reaching length of tibia – and highly setose on its mesal surface as well as apophysis tip. Tibial apophysis short and blunt, projecting mesally and again bearing numerous setae. Legs moderately long, leg II markedly longer than others (leg formula from longest to shortest: II, IV, III, I); approximate total lengths: I, 2.0 mm; II, 6.0 mm; III, 2.4 mm; IV, 3.2 mm. Trochanter, femur, patella and tibia of all legs more robust, again with distinct arrangement of thorns topped with stiff setae, arranged in discrete rows along length of limb article. Tibia to tarsus more slender. Basal part of the tibia with two robust thorns; distal portion of the legs otherwise with stiff setae only. Metatarsi dorsally bear short thorns and strong setae. Tarsi subdivided into ca. seven tarsomeres in each leg where visible (exact number equivocal on some legs); proximal and distal-most tarsomeres longer than those in between. All legs end, where preserved, in a single, curved claw. Genital characters could not be resolved.

Discussion. The new Baltic amber fossil is similar in habitus to the previous record from Bitterfeld, which Dunlop and Mitov (2009, Figs. 27, 31–32) tentatively assigned to Lacinius erinaceus . In the present study, we also considered a similar-looking, spiny harvestman genus: Homolophus Banks, 1893 . For details of this taxon, see e.g. published descriptions of H. afghanus ( Roewer, 1956) , H. chitralensis ( Roewer, 1956) , H. trinkleri ( Roewer, 1956) and H. turcicus ( Roewer, 1959) . Note that Roewer (1956, 1959) originally described these species under Euphalangium ; for a generic synonymy, see Cokendolpher (1987). We also consulted Snegovaya’s recent (2012) description of Homolophus nakhichevanicus Snegovaya, 2012 . We believe that we can exclude the amber inclusions from Homolophus based on the presence in the fossils of a triad of spines at the front of the carapace ( Figs. 1b , 2b ) and the additional presence of spines on the metatarsi of the legs ( Fig. 2a ). In many Homolophus species, there are two principal, diverging forward-pointing spines – or “Gabelzähnchen” – at the front of the carapace, surrounded by a group of denticles sometimes forming a crown. The remaining Homolophus species only have a group of frontal denticles. Furthermore, the metatarsi of the legs of Homolophus are normally smoother than the spiny metatarsi seen in the amber specimens; only some Homolophus species have denticles/tubercles ventrally.

We thus believe that both amber fossils can be comfortably referred to as Lacinius , although the absence of genital characters in these inclusions will always preclude an unequivocal assignment. The fossils are more spiny than the modern species Lacinius angulifer ( Simon, 1878) (see Roewer, 1912: p. 77; Roewer, 1923: Fig. 915), L. dentiger ( Fig. 3a ), L. ephippiatus (Koch, 1835) (see Šilhavý, 1956: Table VII, Fig. 28; Martens, 1978: Fig. 619), L. insularis Roewer, 1923 (see Roewer, 1923: Fig. 918), and Lacinius texanus ( Banks, 1893) (see Banks, 1901: Fig. 4; Roewer, 1912: p. 81; Roewer, 1923: p. 743). The fossils thus have more in common in terms of their external morphology with species like L. horridus (Panzer, 1794) ( Fig. 3b ) and L. erinaceus . The most specific characteristic of the new Baltic amber fossil is the presence of well-developed apophyses on both the patella and tibia. Apophyses of this form are not present in Lacinius erinaceus (see e.g. Dunlop and Mitov, 2009, sub L. erinaceus , Figs. 28–29; Kurt and Erman, 2012, Fig. 5c, L. erinaceus ). We re-examined the original Bitterfeld Lacinius record (MB.A. 1661). The original description did not figure the pedipalps so clearly, but upon restudy, we could confirm that patellar and tibial apophyses are present here too. This suggests that the two fossil Lacinius records probably are conspecific, but differ from L. erinaceus and at least all the modern Palearctic species in this genus.

The closest potential match would be the North American species L. texanus Banks, 1893 , for which Banks (1893, p. 403) stated that “The patella is prolonged, the inner side and prolongation being covered with short, stiff, black hairs. The tibia is enlarged at the end on the inner side and covered with similar hairs [...]”. Unfortunately there is no illustration in the original description to show whether Bank’s “prolongation” of the patella is a substantial apophysis as per the fossil specimens, but subsequent figures and/or redescriptions of L. texanus by Banks (1901, Fig. 4) and later Roewer (1912, p. 81; 1923, p. 743) do not indicate explicit pedipalpal apophyses. As noted above, the general habitus of L. texanus is also less spiny than our amber material, which argues against the fossils being closely related to the living American species.

On balance, we feel justified in proposing a new (fossil) Lacinius species diagnosed on the combination of body ornamentation and pedipalp morphology as above. As noted previously, the new specimen is quite small, and the individual may be immature. Where apophyses are present in phalangiid harvestmen, they can be more prominent in immature instars and become less well expressed in adults. We select the first specimen to be described (MB.A. 1661 from Bitterfeld amber) as the holotype of our new taxon. Since the second (Baltic) specimen is not from the same locality as the holotype, we chose not to treat it as a paratype. The Baltic example of Lacinius bizleyi sp. nov. places the genus back at least in the Eocene, and can also be added to the list of harvestmen found in both Baltic and Bitterfeld amber. The other harvestmen common to both ambers are the nemastomatid Histricostoma tuberculatum (Koch and Berendt, 1854) , the caddid Caddo dentipalpus (Koch and Berendt, 1854) , the phalangiid Dicranopalpus ramiger (Koch and Berendt, 1854) and the sclerosomatid Leiobunum longipes Menge, 1854 . The Opiliones data thus remain preliminary, but our new fossil contributes to the debate (reviewed by, e.g., Standke, 2008, and Dunlop, 2010) about whether Baltic and Bitterfeld ambers are in fact contemporary deposits, sampling the same (implicitly Eocene) fauna. Alternatively, if Bitterfeld amber is a distinct and younger deposit – and not merely older Baltic amber reworked into younger sediments – it implies that there was something of a faunal continuum in the Paleogene of northern–central Europe. In other words, the same (morpho)species of harvestmen, and probably other arachnids too, can be found in the fossil record of this region of Europe across an Eocene-to-Oligocene time period which may correspond to about 25 million years.

Figures

Figure 1. Lacinius bizleyi sp. nov. MB.A. 2815 from Eocene (Lutetian) Baltic amber.At ca.44–49Ma, this is the oldest putative record of the genus. (a) Overview.(b) Detail of the anterior prosoma showing the ocularium (oc), the three spines in front of this and the distinct apophyses on the patella and tibia (arrowed) of the pedipalp (pp). Scale bar equals 1.0 mm.

Figure 2. Camera lucida drawings of the specimen shown in Fig. 1. (a) Overview. (b) Detail of the anterior prosoma. Legs numbered from I to IV.

Figure 3. Comparative photographs of two of the more widespread recent European Lacinius species. (a) Female L. dentiger (Koch, 1848) from Graz, Austria. (b) The more heavily ornamented L. horridus (Panzer, 1795) male from Luberkogel, Austria. Images courtesy of Christian Komposch (Graz).