Atlantasellidae Sket, 1979

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Suggested Common Name: Pillslaters
Number of subordinate taxa: 2 species 1 genus, endemic to our area
Etymology: after Atlantasellus Sket, 1979, see that account for more information.
Taxonomic History: Atlantasellidae Sket, 1979
Size Range: to 2.14mm
Description: Body ovate, highly domed. Antenna 1 peduncle highly differentiated from flagellum. Mandible right incisor simple, left incisor often multicuspid; lacinia fan-shaped; molar soft, brush-like, divided into apical setae; palp 3-segmented. . Maxilla 1 medial lobe with only 1 terminal seta. Maxilla 2 exopod with 2 endites. Maxilliped basis typical, much larger and wider than palp segments; epipod present, well-developed. Oostegites present. Pereopod 1 proposubchelate. Pereopod 5 biramous or not. Pleonites 1-2 free, well-developed. ♂ pleopod 1 present, 2-segmented. ♂ pleopod 2 (when known) exopod small, 2-segmented; endopod 1-segmented. Pleopod 3 operculate, not fused, unsegmented. Uropod minute, vestigial, uniramous, 1-segmented or fused to telson. Anus (when known) subterminal, seperated from branchial cavity.
Type taxon: Atlantasellus Sket, 1979
Notes: This tiny monogeneric family has only 2 species and is endemic to the Caribbean region. As with other monogeneric families, especially ones as distinctive as Atlantasellidae, diagnoses of the genus and family are difficult to parse from each other. The only time this family has ever been diagnosed was in the original description in Sket, 1979, so an updated diagnosis based on features consistent between both known species is included here.
The exact relationship between this family and Microcerberidae remains unknown. Interestingly, the coxae on pereopods 5-7 are fused into coxal plates in Atlantasellus, a trait traditionally considered derived in Microcerberidae (Wägele, J. W., Voelz & Vaun McArthur, 1995). The plesiomorphic state of Microcerberidae is generally considered to be all coxae free and ring-like (such as in Protocerberus and Afrocerberus), but this trait appears to have been evolved in parallel in Atlantasellidae. Atlantasellus is still very distinct from Microcerberidae on both ecological and morphological grounds and still merits its placement in a monogeneric family, so it would be interesting what our understanding of the relationships between the two family will become with more research, especially in further taxon discovery in Atlantasellidae.
The bizarre biogeography of this genus, with one freshwater species endemic to Hispaniola and a nearly marine species endemic to Bermuda, seems to suggest that this family was formerly more widespread in intersitial environments (similar to modern-day Coxicerberus) before becoming "stranded" in a few caves recently.

Subordinate taxa: Atlantasellus

Sources

Jaume, D. (2001). A new atlantasellid isopod (Asellota: Aselloidea) from the flooded coastal karst of the Dominican Republic (Hispaniola): evidence for an exopod on a thoracic limb and biogeographical implications. Journal of Zoology, 255(2), 221-233.

Sket, B. (1979). Atlantasellus cavernicolus n. gen., n. sp. (Isopoda Asellota, Atlantasellidae n. fam.) from Bermuda. Biol, vestn. (Ljubljana), 27(2),175-183.

Wägele, J. W. (1983). On the origin of the Microcerberidae (Crustacea: Isopoda). Journal of Zoological Systematics and Evolutionary Research, 21(4):249-262.

Wägele, J. W., Voelz, N. J., & Vaun McArthur, J. (1995). Older than the Atlantic Ocean: discovery of a fresh water Microcerberus (Isopoda) in North America and erection of Coxicerberus, new genus. Journal of Crustacean Biology, 15(4):733-745.

Published: Feb 15, 2023