Pseudogarypus pangaea Henderickx

Henderickx, Hans, Cnudde, Veerle & Masschaele, Bert, 2006, Description of a new fossil Pseudogarypus (Pseudoscorpiones: Pseudogarypidae) with the use of X­ray micro­CT to penetrate opaque amber, Zootaxa 1305, pp. 41-50 : 43-49

Pseudogarypus pangaea Henderickx n. sp.

( Figs 1–12 )

Type material. Holotype in Baltic amber from Jantarny, Kaliningrad, Russia, deposited in the Royal Museum for Central Africa, Tervuren, Belgium ( MRAC 219415).

Etymology. The specific epithet refers to the ancient continent Pangaea and is to be treated as noun in apposition. Based on modern distributions, ancestral Pseudogarypidae were likely to have been distributed across Pangaea , before this continent broke up (mid­ Jurassic).

Diagnosis. A small Pseudogarypus with broad carapace bearing two posterolateral protuberances, situated anterior to the alae. Anterior and posterior eyes nearly contiguous, femur length less than 1.0 mm, pedipalpal fingers with contiguous, regular teeth.

Description. Habitus as in Figs. 3 and 4 . Body clear, ventral and lateral sides obscured ( Figs. 2 , 5 ). No dorsal colour pattern could be observed (as is usual in Baltic amber, the original coloration will have been lost in the fossilization process).

Carapace wider than long (length 0.78× width measured at level of posterior margin or 0.95x when width is measured across posterolateral tips behind the eyes). Carapace very irregular in outline; anterior margin with a relatively deep notch between anterolateral and median protuberances. Posterior margin elevated into a ridge. Anterior and posterior eyes well developed, nearly contiguous, posterior eyes partially covered and facing posteriorly. Cucullar furrow a broad, shallow central depression which becomes obsolete anteriorly, extending forward from elevated median disk. Carapace, sclerites, palp and leg cuticle reticulated with an irregular net­like structure. Chaetotaxy of carapace and opisthosoma not visible, chelicerae not observable.

Opisthosoma wider than long, broad ovate (L/W=0.92). Pleural membranes raised into three folds ( Fig. 6 arrow b, Fig. 8 ), no pleural plates or tergal chaetotaxy observable. Figs. 1 and 8 show the shape of the sternites, unobservable in visible light, but reconstructed with X­ray micro­CT. No coxal spines observed.

Pedipalp ( Fig. 10 ) cuticle reticulated, except in the area around the trichobothria. The palpal articles have a remarkable ventral edging, visible with light microscopy along the full length of the femur, patella and chela of both pedipalps. Fig. 7 shows the X­ray CT scan of the pedipalpal hand. The cross section of the cuticle is drop­shaped on the outside, whereas the inside is circular. Coxa 1.40×, trochanter 0.95×, femur 4.58×, patella 2.68×, chela (with pedicel) 3.91× and hand (with pedicel) 1.56× longer than broad. Femur 1.36× as long as carapace. Due to local opaqueness of the amber, the position of only 4 trichobothria could be observed on the fixed chelal finger; on the movable finger 4 trichobothria and their position are more clearly visible ( Fig. 9 ). Fixed finger with 32, movable finger with 26 regular, not curved and not significantly spaced teeth (contiguous to very slightly spaced). Movable finger 1.5× as long as hand.

All legs with similar edging to that found on palp, visible with light microscopy on patella, tibia and tarsus; femur only observable as a contour in transmitted light, coxa and femur reconstructed with X­ray micro­CT. Leg I ( Fig. 12 ) with trochanter 1.4×, femur 1.4×, patella 2.4×, tibia 1.5× and tarsus 6.2× longer than broad. Leg IV ( Fig. 11 ) with trochanter 1.9×, femur 1.9×, patella 2.06×, tibia 4.0× and tarsus 8.8× longer than broad. Arolia shorter than claws.

Measurements (in mm). Body length 2.09. Carapace L=0.58, W=0.74 at level of posterior margin, W=0.61 at level of laterally extending tips behind posterior eyes; cucullus L=0.16; anterior and posterior ocular breadth 0.03.

Pedipalp: trochanter 0.19/0.20; femur 0.79/0.17; patella 0.43/0.16; chela (with pedicel) 0.90/0.23; hand (with pedicel) 0.36/0.23; movable finger L=0.54.

Leg I: trochanter 0.13/0.09; femur 0.14/0.10; patella 0.24/0.10; tibia 0.14/0.09; tarsus 0.31/0.05.

Leg IV: trochanter 0.19/0.10; femur 0.19/0.10; patella 0.31/0.15; tibia, 0.36/0.09; tarsus 0.53/0.06.

Distribution. Found in Baltic amber, a fossil Pinus resin from the Eocene Baltic amber forest.

Remarks. Setae are below the resolution of the CT scan in this sample. Fig. 1 shows a single image from the 3­dimensional rotating reconstruction, which is in fact a dynamic observation tool. In a single reconstructed image artefacts can occur, depending on the parameters entered. Therefore a drawing of the ventral parts was made ( Fig. 8 ), based on the dynamic model, giving more accurate dimensions. The circular inside of the pedipalpal articles is an indication that there was no shape deformation caused by pressure (squeezing) during the formation of the fossil and, though the ‘edging’ of the outside cuticula has not been described for any pseudoscorpion before, it is unlikely to be an artefact of fossilization.

Figures

FIGURE 3. Pseudogarypus pangaea n. sp., holotype, dorsal habitus reconstruction.

FIGURES 1 – 2. Pseudogarypus pangaea n. sp. holotype. 1, ventral view, X­ray micro­CT reconstruction; 2, ventral view, visible light.

FIGURES 4 – 5. Pseudogarypus pangaea n. sp., holotype. 4, dorsal view; 5: dorso­lateral view, showing opaque emulsion on lateral side.

FIGURES 6 – 7. Pseudogarypus pangaea n. sp., holotype, X­ray CT, reconstructions. 6, Lateral view with carapaceal alae (a) and pleural membranes (b). 7, Cross section of pedipalpal hand.

FIGURES 8 – 12. Pseudogarypus pangaea n. sp., holotype. 8, Ventral reconstruction; 9, Right pedipalp, externo­lateral; 10, Left pedipalp, dorsal. 11, Leg 4. 12, Leg 1. Figures 9 – 12 to same scale.