Sorensenella prehensor explained

Sorensenella prehensor is a species in the endemic New Zealand genus Sorensenella described by Reginald Pocock in 1903.^[1] Ray Forster revised the genus Sorensenella in 1954.^[2] As well as the nominate subspecies, Sorensenella prehensor prehensor, added two other subspecies, S. prehensor nitida and S. prehensor obesa. This species is found from Auckland to North Cape in New Zealand's North Island.

Taxonomy

Sorensenella prehensor is the type species of the genus Sorensenella and was described by Pocock in 1903. Pocock did not explicitly designate a type specimen. However, Forster's 1954 revision of the genus Sorensenella noted there was only a single specimen in the British Museum, and that Pocock's description also implied this. Forster also noted that Carl F. Roewer's figure^[3] of S. prehensor was a specimen of S. bicornis.

Forster's revision added two subspecies based on minor morphological and geographical grounds: S. prehensor nitida and S. prehensor obesa.

Description

Sorensenella prehensor has the general characteristics of Sorensenella. Forster's redescription based on a greater range of material than was available to Pocock notes the following additional characters. Colour reddish brown with a black pattern on the scute (the unsegmented portion of the carapace). Free tergites are blackish with a transverse row of pale brown spots. The chelicerae and pedipalps have reticulated dorsal markings. Females have more slender pedipalps than males. The tubercles (pointed protuberances) behind the anterior corners of the carapace are also smaller, as is the tubercle on top of the eyemound.

The nominate subspecies S. prehensor prehensor may be distinguished from S. prehensor nitida by having a larger tubercle on the eyemound in both males and females. Sorensenella prehensor nitida is also confined to East Cape, while S. p. prehensor is found in the northern North Island. Sorensenella p. prehensor may be separated from S. p. obesa by the latter's greater size and slightly backward-pointing eyemound tubercle. Both are found at North Cape, with S. p. obesa confined to a separate population in the northernmost part of the region.

Distribution

Sorensenella prehensor is found in the northern North Island of New Zealand, from Auckland to North Cape.

Conservation status

This species has not been assessed as part of the New Zealand Threat Classification system.^[4]

Notes and References

1. Pocock . Reginald Innes . 1903-01-01 . On some new harvest-spiders of the order Opiliones from the southern continents . Proceedings of the Zoological Society of London . 1902 . 392–413.
2. Forster . Raymond Robert . 1954-07-01 . The New Zealand harvestmen (sub-order Laniatores) . Canterbury Museum bulletin . English . 2 . 1–329.
3. Roewer . Carl Friedrich . 1931-01-01 . Über Triaenonychiden (6. Ergänzung der "Weberknechte der Erde", 1923) . Zeitschrift für wissenschaftliche Zoologie . 138 . 137–185.
4. Buckley . T. R. . Palma . R. L. . Johns . P. M. . Gleeson . D. M. . Heath . A. C. G. . Hitchmough . Rod . Stringer . I. A. N. . 2012-06-21 . The conservation status of small or less well known groups of New Zealand terrestrial invertebrates . New Zealand Entomologist . 35 . 2 . 137–143 . 10.1080/00779962.2012.686319.