Tegeocranellidae, P. Balogh, 1987

Pfingstl, Tobias, 2017, The marine-associated lifestyle of ameronothroid mites (Acari, Oribatida) and its evolutionary origin: a review, Acarologia 57 (3), pp. 693-721 : 714

The semiaquatic Tegeocranellidae and their relationship to marine-associated mites

Several authors (e.g. Subías 2004, Marshall and Pugh 2002) do not accept the monogeneric Tegeocranellidae as a member of Ameronothroidea because they do not consider the juvenile morphology to be important for systematic considerations. Given the above-mentioned doubts about the monophyly of Ameronothroidea , it may seem reasonable to agree with these authors. Nonetheless, Behan-Pelletier (1997) provided seven synapomorphies supporting a relationship among Tegeocranellidae , Fortuyniidae and Selenoribatidae . The most obvious synapomorphy is certainly the shared type of juvenile plication, namely a centrodorsal gastronotic plate framed by deep lateral and ventral folds and wrinkles, only present in immatures of these three taxa. Pfingstl and Krisper (2014) demonstrated that this specific type of plication plays an important role in plastron respiration of juvenile fortuyniid and selenoribatid mites. Though not investigated yet in tegeocranellid immature stages, they may use the same plastron mechanism and this could be a further indication of a common origin. Another morphological character associated with plastron respiration may also support a close relationship between Tegeocranellidae and Fortuyniidae . The already-mentioned van der Hammen’s organ of fortuyniid mites is part of the plastron system, and Behan-Pelletier (1997) noticed similar structures in Tegeocranellidae but refrained from considering these traits homologous. Considering a close relation between Tegeocranellidae and Fortuyniidae / Selenoribatidae , occupation of semiaquatic freshwater habitats may represent the more ancestral ecology. Based on these indications, the following scenario might be considered: a terrestrial ancestor colonized semiaquatic and aquatic freshwater habitats, e.g. ponds and streams, then some descendants diversified within these environments, evolving the Tegeocranellidae , and others colonized the marine littoral either by migrating downstream into brackish waters or by inhabiting coastal freshwater bodies that eventually became connected to the open ocean and evolved there to the Fortuyniidae and Selenoribatidae .