Neobisium henderickxi, Judson, 2003

Judson, Mark L. I., 2003, Baltic amber pseudoscorpions (Arachnida, Chelonethi): a new species of Neobisium (Neobisiidae) and the status of Obisium rathkii Koch & Berendt, Geodiversitas 25 (3), pp. 445-450 : 446-447

Neobisium henderickxi n. sp. ( Figs 1; 2 )

TYPE MATERIAL. — Holotype, adult (?) in a clear, pale-yellow piece of Baltic amber, deposited in the palaeontology collections of the MNHN (reg. No. MNHN-LP-R.11188). Ventral parts of pseudoscorpion clouded by a milky emulsion (“ Schimmel ”). Also present in the piece are a worker ant of the genus Aphaenogaster Mayr, 1853 and a small mite (Cheyletoidea?). The fossil was purchased by Hans Henderickx from an amber dealer who stated that it came from Denmark, but it seems more likely that it would have come from one of the southern Baltic states. ETYMOLOGY. — Patronym in honour of Hans Henderickx.

DESCRIPTION

Medium-sized, dark and normally-sclerotized species of Neobisium ( Fig. 1). Carapace ( Fig. 2B ) with setal formula approximately 4-6(24); epistome short and blunt; eyes well developed, anterior pair distinctly larger than posterior pair. Tergal setae 8?-8?-8?-8-8-8-8?-8-8-8?-6-2. Pleural membrane papillostriate. Chelicera ( Fig. 2A ) with six setae on hand; fixed finger with six small teeth; movable finger with three large basal teeth and about five small apical teeth; spinneret tubercle broad and low. Palps ( Fig. 2C ) without granulation; a single, small tubercle (raised lyrifissure) present on femur, near middle of posterior margin; patellar notch reaching about half length of inner (paraxial) margin ( Chamberlin 1962), x/y ratio ( Gabbutt & Vachon 1965) about 0.90; both fingers homodentate, teeth contiguous; ist slightly distad of middle of finger, nearer to it than to ib; it slightly more distal than et. Legs I and II with sparse, sharp granules on anterior face of femur.

Measurements (in mm)

Body length (contracted) 1.95. Carapace 0.72 × c. 0.65 (ocular breadth). Chelicera 0.62 × 0.44. Palp: see Table 1.

REMARKS

As noted in the introduction, N. henderickxi n. sp. is very similar to N. kobachidzei , which is known from the Caucasus and neighbouring territories, and to N. speleophilum , also from the Caucasus. The differences between N. kobachidzei and N. speleophilum are slight, so it is possible that they are synonymous ( Dashdamirov & Schawaller 1993). Characters shared by these species and the fossil include the form and dimensions of the palps (particularly the relatively long fingers), the similar number of setae on the carapace and chelicera, the general arrangement of the trichobothria, and the absence of a dense group of enlarged setae on the paraxial face of the chelal hand. The similarities in the measurements of the palps ( Table 1) are striking, but it should be borne in mind that the sex of the specimen is uncertain and that Neobisium species show sexual dimorphism of the palps. Judson (1998) suggested that the dimensions of amber pseudoscorpions might be slightly reduced from those of the living animal, but such differences, if they exist, are likely to be small. The new species can be separated from N. kobachidzei and N. speleophilum by the more basal position of trichobothria isb and est; in the fossil est is about half way between ist and et and ist, whereas in the Recent species est is clearly nearer to et. N. henderickxi n. sp. might also be separated from the Recent species by its more obtuse epistome, but this character can show intraspecific variation ( Mahnert 1988).

Neobisium henderickxi n. sp. is readily separated from the other Baltic amber species, N. exstinctum , by its longer chelal fingers (shorter than hand in N. exstinctum ) and the lower number of tergal setae (12 on middle tergites of N. exstinctum ).

Figures

FIG. 2. — Neobisium henderickxi n. sp., holotype; A, right chelicera, dorsolateral view; B, carapace, dorsal (slightly oblique) view (left eyes poorly visible); C, right palp (composite: parts of femur and trichobothriotaxy based on left palp; hand and patella moderately foreshortened; arrow indicates limit of articular notch of patella; muscle sigilla partially shown at base of hand). Scale bars: A, 0.2 mm; B, 0.3 mm; C, 0.5 mm.