Caeculus aeternus sp. nov. is described based on a single specimen preserved in Baltic amber (Eocene). This species is the second fossil representative of the genus Caeculus, and the third species of the genus known from Europe. The species has a remarkable resemblance to the unique extant species of Caeculus in Eurasia: C. echinipes, differing only by the number of setae in the dorsal plates and the length and shape of setae of some leg segments. Morphological diachronic stasis in caeculid mites is discussed.
Porta et al. (2025) studied this question.