Reductholaspis, Emberson, Rowan M., 2010

Emberson, Rowan M., 2010, A reappraisal of some basal lineages of the family Macrochelidae, with the description of a new genus (Acarina: Mesostigmata), Zootaxa 2501, pp. 37-53 : 45

Reductholaspis new genus

Macrocheles .— Hyatt & Emberson, 1988: 78, pars. Type species: Macrocheles analis Hyatt & Emberson, 1988 .

Geholaspini with reduced dorsal ( Fig 11 ) and ventral sclerotisation; ventral opisthosomatic sclerotisation limited to an anal shield; chelae elongate, bidentate ( Fig. 12 ); epistome with a narrow, distally bifid median process ( Fig. 13 ); hollow seta of palp tarsus similar in length to surrounding setae.

The dorsal shield ( Fig. 11 ) tapers strongly from the shoulders and is mildly hypotrichous for the family, having 27 pairs of pilose setae, instead of the 28 pairs of setae found in most macrochelids. The shields of the ventral surface are weakly sclerotised and reduced in size. The epigynal shield is almost semicircular posteriorly and the epigynal pores are on the unsclerotised membrane. There are two pairs of lightly sclerotised post-epigynal platelets. The opisthogastric sclerotisation is reduced to a small oval anal shield ( Fig. 14 ) without pre-anal setae. The epistome has a dentate anterior margin with a narrow, bifid, median process, which is distally dissected ( Fig. 13 ). Both chelae are bidentate and elongate ( Fig. 12 ), with the fixed chela being 3.5 times as long as its basal width. The corniculi are four times as long as their basal width, and reach the anterior margins of the pedipalpal femora. The external posterior hypostomatic setae h2 are anterior to internal hypostomatic setae h3 ( Fig. 15 ). The hollow seta on the external surface of the palp tarsus, which is prominent in most other macrochelids, is no longer than the surrounding setae.

Males unknown.

Notes. The elongate corniculi and the anterior position of the external posterior hypostomatic setae (h2) are characters shared by all members of the Geholaspini, and the form of the epistome is almost identical to that found in Longicheles . The elongation of the cheliceral digits, though not their dentition, is another possible apomorphy shared with Longicheles . These characters clearly point to a close relationship of R. analis with the genera of the Geholaspini, rather than the previously suggested placement in the opacus species group of Macrocheles . The reduction in opisthogastric sclerotisation to a simple anal shield is, however, unique in the geholaspine group of genera. In the Macrochelidae , simple anal shields otherwise occur only in Neopodocinum and Lordocheles Krantz , neither of which appears to be closely related to R. analis .

Figures

FIGURES 8 – 11. 8 – 9. Longicheles hortorum (Berlese), female. 8. Dorsum, showing posterior displacement of setae j 5; 9. Anterior dorsal region, showing position and characters of setae j 1, j 2 and z 1. 10. Longicheles longulus (Berlese) comb. nov., female, anterior dorsal region, showing position and characters of setae j 1, j 2 and z 1. 11. Reductholaspis analis (Hyatt & Emberson) comb. nov., female, dorsal shield.

FIGURES 12 – 17. 12 – 15. Reductholaspis analis (Hyatt & Emberson) comb. nov., female. 12. Chelicera; 13. Epistome; 14. Anal shield; 15. gnathosoma venter, showing position of hypostomal setae. 16. Nothrholaspis carinatus (Koch), epistome. 17. Macrholaspis opacus (Koch), epistome.