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Medog harvestmen (Linzhiassamia medogensis) and Zayu harvestmen (Linzhiassamia zayuensis)

Medog harvestmen (Linzhiassamia medogensis) and Zayu harvestmen (Linzhiassamia zayuensis) 1

NEWS - Researchers have established a new genus, Linzhiassamia gen. nov. from Xizang, China, along with two new species, Medog harvestmen (Linzhiassamia medogensis) and Zayu harvestmen (Linzhiassamia zayuensis) as the first descriptions of the harvestmen family (Assamiidae) from Xizang.

Knowledge of Assamiidae in the Eastern Himalayas is mostly concentrated in Nepal, while Bhutan, Xizang and northeastern India are poorly studied. This study provides a comparative analysis of other continental Asian Assamiidae with a focus on genital morphology.

The genus name is based on 林芝 (Linzhi), an alternative name for Nyingchi. The name is associated with the pre-existing name Assamia. The species epithet medogensis is derived from the specimen collection location in Medog, Nyingchi, Xizang. The specimens were collected under rocks and under bushes.

The epithet zayuensis is derived from the collection location in Zayu, Nyingchi, Xizang. Specimens were collected by sifting through fallen leaves in dark and damp undergrowth in the forest, also under stones and on the foliage of bushes.

Linzhiassamia is similar to Paktongius for sexually dimorphic coxa IV which in males can reach areas III, IV or even V of the dorsal scutum, while in females it is much shorter which is only area II and does not protrude laterally.

Similar to Dhaulagirius for sexually dimorphic chelicerae, but Dhaulagirius has much more overdeveloped chelicerae hands. Similar to Nilgirius and Paktongius for having a "pseudonychium" (tarsal process) on the tarsi of legs III and IV.

Similar to Dhaulagirius, Micrassamula and Nepalsia for not having a sharp constriction like a circular joint in the distal third of the penis truncus, between the pars basalis and pars distalis. Similar to Dhaulagirius, Nepalsia and Nepalsioides for having MS A arranged in a triangular shape.

Similar to Dhaulagirius, Nepalsia and Nilgirius in that it lacks a wide dorsal depression, so that the distal trunk looks like an ice cream scoop. Similar to Nepalsia and Nilgirius in that it has all macrosetae concentrated in the distal part. Similar to Dhaulagirius in that it has a distal part of the trunk with a constriction, widening to form a piriform structure.

L. medogensis has a prominently enlarged distal penis (pars distalis), an almost triangular ventral plate and a frontal edge with a median cleft, convex in dorsal view and concave in ventral view, the pars basalis and pars distalis of the penis connected by a joint.

Glans is partly concave to the depressed dorsal part of the pars distalis of the penis, the tip extending slightly to the distal edge of the ventral plate. Opistosomal region of the scutum with abundant setiferous tubercles. Ocularium without spines, but with scattered small tubercles. Femur of pedipalps ventrally with a row of six or seven setiferous tubercles.

Medog harvestmen (Linzhiassamia medogensis) and Zayu harvestmen (Linzhiassamia zayuensis) 2

L. zayuensis has a smooth and uncurved distal edge of the ventral plate. The external capsule is cylindrical and the internal capsule is triangular, the inner side of the internal capsule is covered with dense bristle-like microtrichia. The ocularium has short or no spines and two or three spines are present on the anterior lateral edge of the carapace.

Both new species exhibit pseudonychial tarsal claws that have prompted comparisons with Indian Trionyxellidae such as Nilgirius. However, initial examination of the genitalia of Nilgirius scaber Roewer 1915 from southern India, revealed a very different genital structure.

The Tibetan species Linzhiassamia also has a pyriform distal truncus, which is less concave, with elongated macrosetes similar to Dhaulagirius altitudinalis Martens 1977. However, sexual dimorphism in the chelicerae is much more subtle.

Comparisons with Dhaulagirius are not impossible, but defining a suprageneric group for the highlands remains unclear. Knowledge of the Eastern Himalayan highlands is still poor. No assamids are known from Bhutan and a few species from Arunachal Pradesh are from 600 m elevation with limited descriptions.

Original research

Qi X, Kury AB, Zhang C (2024). A new genus of Assamiidae (Opiliones, Grassatores) from Xizang, China. ZooKeys 1215: 27-52, DOI:10.3897/zookeys.1215.132189

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