Revision of recluse spiders (Araneae: Sicariidae: Loxosceles) preserved in Dominican amber and a total-evidence phylogeny of Scytodoidea reveal the first fossil Drymusidae

Abstract

Recluse or violin spiders in the genus Loxosceles (Scytodoidea: Sicariidae) are a diverse group (~140 extant species) including medically important species and distributed mainly in the Americas, Africa, and the Mediterranean region. In addition, this genus includes three fossil species from Miocene Dominican amber. Here we revise the taxonomy of these fossil species by examining, imaging and re-describing their type specimens. We find that L. defecta Wunderlich, 1988 and L. deformis Wunderlich, 1988 are bona fide members of the genus and report additional characters overlooked in their original descriptions. We further study the holotype of L. aculicaput Wunderlich, 2004 using synchrotron radiation micro-computed tomography to reveal previously unknown morphological details hidden by fissures in the amber. We found several characters inconsistent with Loxosceles but consistent with Drymusa (false violin spiders; Scytodoidea: Drymusidae), such as three claws, well-developed podotarsite, and a broad colulus. This suggests the species is misplaced in Loxosceles. To test this hypothesis, we estimated a total-evidence phylogeny of the superfamily Scytodoidea including extant and fossil taxa, morphological data, traditional molecular markers, and sequences of ultra-conserved elements. The results show unambiguously that L. aculicaput belongs to Drymusa and is a close relative of extant species of the genus inhabiting the Greater Antilles. Therefore, we here transfer this species to Drymusa, establishing a new combination and new family assignment. Drymusa aculicaputcomb. nov. represents the first known fossil Drymusidae and shows that crown members of this genus already existed in the Miocene.

Advances in the reconstruction of the spider tree of life: A roadmap for spider systematics and comparative studies

“…Wood et al (2013) used tip-dating to show that Palpimanoidea diversification was shaped by the break-up of Pangaea in the Mesozoic. Recently, using morphology observed under microCT, Magalhaes et al (2022) discovered that the holotype of Loxosceles aculicaput Wunderlich, 2004 (Sicariidae) is actually a misidentified Drymusidae, which was the first fossil from the latter family and placed in a phylogeny. Fossils are also useful in reconstructing trait evolution.…”

Advances in the reconstruction of the Spider Tree of Life: a roadmap for spider systematics and comparative studies

“…Wood et al (2013) used tip-dating to show that Palpimanoidea diversification was shaped by the break-up of Pangaea in the Mesozoic. Recently, using morphology observed under microCT, Magalhaes et al (2022) discovered that the holotype of Loxosceles aculicaput Wunderlich, 2004 (Sicariidae) is actually a misidentified Drymusidae which was the first fossil from the latter family and placed in a phylogeny. Fossils morphology is also useful in reconstructing trait evolution.…”

First record of the false violin spider of the family Drymusidae (Araneae, Synspermiata, Scytodoidea) from Venezuela, with the description of a new species

“…Members of the family Drymusidae are popularly known as false violin spiders due to their external resemblance to the brown spiders (Labarque et al 2018), also known as violin or recluse spiders, which are species of medical importance of the genus Loxosceles Heineken & Lowe, 1832 (Sicariidae). Nonetheless, this resemblance is superficial since recent morphological and molecular studies have revealed that Drymusidae is closely related to the Australian family Periegopidae, both belonging to the Scytodoidea superfamily, which includes Sicariidae and other families (Labarque et al 2018;Magalhaes et al 2022). Drymusidae comprises two genera: the African Izithunzi Labarque, Pérez-González & Griswold, 2018 with five species and the Neotropical Drymusa Simon, 1892 with 12 species (Labarque et al 2018;World Spider Catalog 2023).…”