New ricinuleids from Cenomanian Kachin amber (Myanmar) and a reassessment of †?Poliochera cretacea (Arachnida: Ricinulei)

Gamarra-Cuba M.; Selden P.A.; Delclòs X. · Palaeoentomology (2026) · DOI: 10.11646/palaeoentomology.9.4.5

Resumen

The fossil record of Ricinulei Thorell, 1876 is sparse and taxonomically complex, particularly for Cretaceous amber taxa. Here we describe five previously unreported ricinuleid specimens from Cenomanian Kachin amber (Burmese amber, Myanmar) and provide a detailed morphological assessment within the existing systematic framework of the order. Special attention is given to ontogenetically informative characters, including tarsal segmentation, dentition of the pedipalpal fixed finger, the tubercle coefficient (tc), and the proportional relationship between pedipalpal tibia length and height (PT l/h). Quantitative comparisons of tc values and PT l/h ratios, together with qualitative assessment of diagnostic characters, were used to assess whether the studied specimens represent distinct taxa or different ontogenetic stages of a single species. These data were further compared with documented ontogenetic series of extant Ricinulei to establish a developmental framework for interpretation. Our results indicate that the new material exhibits stable morphological differences inconsistent with a single ontogenetic sequence. Furthermore, we propose the tentative reassignment of †?Poliochera cretacea Wunderlich, 2012 to a new genus Protoricinus, restricting the genus †Poliochera to the Carboniferous. This study highlights the importance of integrating ontogenetic data and quantitative morphological metrics in the systematic evaluation of fossil Ricinulei and contributes to a more refined understanding of ricinuleid diversity in Gondwanan Cretaceous ecosystems.

Instituciones: Universidad Nacional Mayor de San Marcos