Pseudochiridium lindae, Udson, 2007

Udson, Ark, 2007, First fossil record of the pseudoscorpion family Pseudochiridiidae (Arachnida, Chelonethi, Cheiridioidea) from Dominican amber, Zootaxa 1393, pp. 45-51 : 46-49

Pseudochiridium lindae n. sp.

( Figs 1 –13)

Material examined. Holotype ♂ and paratype ♀ in separate pieces of amber from Palo Alto mines, near Santiago (Santiago de los Caballeros), Dominican Republic. Both types deposited in MNHN.

Etymology. This species is dedicated to my mother, Linda M. Judson.

Diagnosis. Fossil Pseudochiridium with palps more attenuate than in extant species (e.g. palp femur 3.7– 3.9 and chela + 3.6–3.7 times longer than broad); leg coxae with large median areas free of macrogranulation; apical lobe of movable cheliceral finger long.

Description. Granules of dorsal surfaces large, sparse and irregular in form. Setae of dorsal surfaces large and strongly clavate. Carapace ( Fig. 8) with two well developed furrows, anterior 0.51–0.55 and posterior 0.85 length of carapace from anterior margin; eyespots present in ♂ (not visible in ♀); prozone with particularly large granules posterolaterally; setal formula ♂ 24: 12: 6 (42), ♀ ca. 21 [assuming that abraded area contained 2 setae]: 16: 8 (ca. 45), preocular seta slightly smaller than others. Posterior margin of carapace and tergites I–VIII chevroned. Tergites I–IX weakly divided; I–X visible in dorsal view; setae (left + right) ♂ 3+3: 3? + 5: 5? + 5: 6? + 5: 6? + 5: 6? + 5: 6+5: 5+6: 6+6: 6+6: 6+7: 6+7: 2; ♀ 4+4:5+5:5+5:6+5: 7+7: 7+7:?+7:?+8:?+7: 6+6. Coxae of palp with strong granulation; coxae of legs I–IV with large, nearlysmooth (microgranulate) areas that lack macrogranules or setae, coxa IV of ♀ (Fig. 13) with a long, broad posterior extension, that of ♂ (Fig. 11) smaller and more triangular; approximate chaetotaxy of ♂ leg coxae I 7: II 6: III 12: IV 27, setae of palp coxa dentate, seta anteriad of foramen elongate, most setae of leg coxae simple, but some dentate setae anteriorly and laterally; chaetotaxy of ♀ not determined, but coxa IV with 50–51 setae, which are very long posteriorly. Anterior genital sternite of ♂ with a median group of 34 long, simple setae; posterior sternite with a row of 6 smaller setae (Fig. 11). Anterior genital sternite of ♀ with 12 small setae extending along midline; posterior genital sternite with a row of 4 setae near middle of posterior margin ( Fig. 10). Genitalia of male partially preserved ( Fig. 6), dorsal apodeme Y­shaped; genitalia of female not visible. Anterior tracheae reaching coxa III, posterior tracheae small. Setae of sternites IV–XII (♂: left half only) 6: 8: 8: 8: 9: 8: 5: 3/5: 2; setae simple on sternites IV–VI, dentate on VII and progressively more clavate on posterior sternites, but simple on XII; chaetotaxy not determined in ♀. Chelicera ( Fig. 7) with 5 simple setae on hand, es not reduced, sb longer and thicker than b; movable finger with subapical lobe long and curved; seta gs extending well past end of spinneret; spinneret of ♀ with 2 deep branches, dorsal branch with 3 rami, ventral branch with 2; ♂ spinneret not clearly visible. Palps ( Figs 3–5) typical, but slightly more elongate than in other species. Trochanter strongly raised distally, ventral lobe long. Granulation of chela extending onto fixed finger, forming a slight dorsal elevation in lateral view, at the end of which is a long, clavate seta. Trichobothrium isb distad of esb; position of ist variable—level with est on left chela and halfway between est and it on right chela of ♀ ( Figs 3 and 4); position not determined in ♂. Legs I and II with mobile joint between femur and patella; tarsi of all legs draw out to a long thin tip distally, with a fine, dense, hispid ornamentation ventrally and laterally. Dorsal setae of legs clavate, but becoming dentate on tarsi; ventral setae denticulate, except those of tarsi, which are simple and long. Arolia of legs simple and slightly shorter than claws.

Figures 11–13. Pseudochiridium lindae n. sp.: 11, coxae IV and genital sternites of male, ventral view (granulation only shown on left coxa); 12, reference points used to measure coxa; 13, coxae IV of female, ventral view (margins of genital sternites II and III indicated between coxae; granulation only shown on left coxa).

Measurements of male. Body (fully contracted) 0.84 × 0.57. Carapace 0.42 × 0.42 (1.0). Palp femur 0.315 × 0.088 (3.6), patella 0.258 × 0.107 (2.4), chela + 0.470 × 0.128 (3.7), chela – 0.448 (3.5), hand + 0.236 (1.8), hand – 0.207 (1.6), movable finger ca. 0.228 (ca. 1.0 × hand +, 1.1 × hand –). Leg II tarsus 0.195 × 0.037 (5.3). Leg IV coxa 0.180 × 0.140 (1.3), femur 0.147 × 0.077 (1.9), patella 0.170 × 0.078 (2.2), femoropatella 0.281 (3.6), tibia 0.203 × 0.044 (4.6), tarsus 0.228 × 0.040 (5.8). Coxa IV 0.18 × 0.14.

Measurements of female. Body (fully contracted) 0.89 × 0.63; carapace 0.40 × 0.41 (1.0); palp femur 0.330 × 0.084 (3.9), patella 0.267 × 0.103 (2.6), chela + 0.470 × 0.129 (3.6), chela – 0.450 (3.5), hand + 0.256 (2.0), hand – 0.244 (1.9), movable finger 0.228 (0.89 × hand +, 0.93 × hand –). Coxa IV 0.18 × 0.21.

Remarks. The male and female types of Ps. lindae are generally similar and are here considered conspecific. It should be noted that the palps of the male are better preserved and hence more reliably measured than those of the female, except that both chelae of the male are obscured to some extent by debris. The apparent difference in the form of the trochanter in figures 3 and 5 is not significant: the joint between the femur and trochanter is strongly elevated relative to the pedicel of the trochanter in Pseudochiridiidae , which means that even a small difference in orientation can alter the outline observed.