The largest fossil of the segmented spider Parvithele muelleri Wunderlich, 2017 (Mesothelae: Parvithelidae) from Cretaceous Burmese amber

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  The largest fossil of the segmented spider Parvithele muelleri Wunderlich, 2017 (Mesothelae: Parvithelidae) from Cretaceous Burmese amber Abstract A new specimen of the fossil spider Parvithele muelleri Wunderlich, 2017 (Araneae: Mesothelae) is described from the mid-Cretaceous (ca. 99 Ma) Burmese amber of Myanmar. Like the original holotype, the new specimen is a mature male, which clearly preserves a series of tibial macrospines, similar to the condition in the extant genus Liphistius Schiødte, 1849. Given that the single extant mesothele family, Liphistiidae, is predicted to have radiated ca. 39–58 million years ago, the occurrence of somewhat modern-looking male pedipalp spination in older fossil mesotheles is of considerable interest. The new specimen also shows spinnerets in a relatively posterior position, although variability observed in extant species suggests that this trait may be of limited systematic value. Of particular note is the presence of a large and well-dev...

New species of Metagonia Simon with directionally asymmetric male and female genitalia (Araneae, Pholcidae)

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New species of Metagonia Simon with directionally asymmetric male and female genitalia (Araneae, Pholcidae)


Abstract

Genital asymmetry is a rare phenomenon in spiders, and directional asymmetry, where all specimens are same-sided, is particularly scarce. In the New World genus Metagonia, only M. mariguitarensis (González-Sponga, 1998) was previously known to be directionally asymmetric. Here we describe three further species in the genus Metagonia that all share directionally asymmetric male and female genitalia: M. embera Huber sp. nov. (Colombia and Panama), M. uca Huber sp. nov. (Colombia), and M. wayuu Huber sp. nov. (Colombia and Venezuela). Metagonia uca is the species with the most extreme asymmetry and also the only species where female asymmetry is not limited to internal structures but extends to the epigynal scape. Interspecific CO1 distances among these four species ranged from 15.5 to 20.9%. Intraspecific distances mostly ranged from 0.0–1.7%, but higher values were found for M. mariguitarensis (up to 9.1%). While the available evidence suggests that directional asymmetry in Metagonia arose only once (in the last common ancestor of the four species above), the origin of the more widespread asymmetry in Metagonia (female antisymmetry) is less clear. We briefly discuss the phylogenetic pattern of antisymmetry in Metagonia, concluding that further focused research is necessary to provide the basic data for such an analysis.

Huber, B. A., & Meng, G. (2025). New species of Metagonia Simon with directionally asymmetric male and female genitalia (Araneae, Pholcidae). European Journal of Taxonomy, 1026(1), 199–235. https://doi.org/10.5852/ejt.2025.1026.3117