A new Psammitis species (Araneae, Thomisidae) from an extinct volcano in Georgia with reevaluation of the generic position of Xysticus marmoratus Thorell, 1875

A taxonomic study has described a new species of crab spider from Georgia’s extinct Didi Abuli volcano and reassessed the generic placement of Xysticus marmoratus Thorell, 1875. The researchers named the new species Psammitis abuliensis and proposed transferring X. marmoratus to Psammitis as Psammitis marmoratus.

The description was based on two male specimens collected under small stones at the summit of Didi Abuli on 12 September 2018. The mountain is the highest peak in the Lesser Caucasus and lies in the Abul-Samsari Range. The holotype and paratype, both males, were deposited in the scientific collections of Ilia State University in Tbilisi, Georgia.

P. abuliensis resembles the Georgian species Psammitis sabulosus and the Turkish species P. demirsoyi. Its male genital structures distinguish it from both: the embolus tip is very short and broad and bow tie-shaped, the basal embolus is longer, and a large tutacular apophysis is present. The absence of that apophysis distinguishes the new species from P. demirsoyi, while P. sabulosus has a longer, thinner embolus tip.

The holotype measures 6.90 mm in total length, and the paratype measures 6.85 mm. Their carapaces are 3.41 and 3.39 mm long, respectively, and their abdomens are 3.80 and 3.85 mm long. The study also documented leg measurements and spination, sternum markings, coloration and the diagnostic genital morphology.

DNA analysis yielded identical mitochondrial COI barcodes for the two specimens, deposited in BOLD as AFP6894. In BOLD, the nearest listed neighbor was a Psammitis ninnii specimen from Spain with a private status, at an uncorrected p-distance of 6.3%. The new species is currently known only from its type locality, and no female was available for description.

For the broader assessment, the researchers combined the new COI sequences with published and project-generated barcodes of Psammitis and several outgroup genera. They used uncorrected p-distances to construct a Neighbor-Joining tree in MEGA 11 with 1,000 bootstrap replicates. The analysis included 13 COI sequences representing 10 thomisid species.

The authors transferred Xysticus marmoratus to Psammitis as Psammitis marmoratus comb. nov. The reassessment was based partly on the similarity of the male palp to the Psammitis type species, which has an anapophysate tegulum. The phylogenetic tree also placed X. marmoratus in close association with species of Psammitis.

Because females of Psammitis and Xysticus did not exhibit clearly defined characters that could reliably separate the genera, the evidence for the transfer rested on male morphology and the barcode-based tree. The analysis involved a limited set of specimens and taxa, and the new species remains represented by two males from one locality.

The authors said the reevaluation indicates that additional revision of Xysticus may be warranted. They also noted that exploration of remote and poorly studied localities in Georgia could reveal more species and help clarify three Caucasus-endemic Xysticus species originally described from single females.

Subject of Research: Taxonomic description and molecular reassessment of Georgian crab spiders in the family Thomisidae

Article Title: A new Psammitis species ( Araneae , Thomisidae ) from an extinct volcano in Georgia with reevaluation of the generic position of Xysticus marmoratus Thorell, 1875

Article References: Seropian, A., & Mumladze, L. (2024). A new Psammitis species (Araneae, Thomisidae) from an extinct volcano in Georgia with reevaluation of the generic position of Xysticus marmoratus Thorell, 1875. Caucasiana, 3, 119-126. https://doi.org/10.3897/caucasiana.3.e120656

Image Credits: AI Generated

DOI: 10.3897/caucasiana.3.e120656

Keywords: Psammitis abuliensis, Psammitis marmoratus, Xysticus marmoratus, Thomisidae, crab spiders, Georgia, Didi Abuli, DNA barcoding, COI phylogeny, species description, Psammitis, species