Halacarids (Halacaroidea, Acari) in freshwater. Multiple invasions from the Paleozoic onwards?

Halacarid mites are primarily marine, but about 60 species have specialized to live in freshwater. Invasion into continental waters has taken place independently in various epochs. The ancestors of the exclusively freshwater genera Lobohalacarus, Porohalacarus, Porolohmannella, Ropohalacarus, and those of the subfamily Limnohalacarinae, are supposed to have colonized the shores of Pangaea, become adapted to freshwater and dispersed via continental freshwater and coastal oligomixohaline waters in the Mesozoic. These exclusively freshwater genera are presumed to have existed for distinctly > 100 million years. Many a species or species group is present world-wide. This pattern of distribution is thought to be due to a combination of Mesozoic (pre Mesozoic) age, euryvalence with respect to environmental factors, and predominantly parthenogenetic mode of reproduction. The history of Caspihalacarus and circum-Mediterranean limnic Copidognathus seems to be closely correlated with the fate of the Tethys and/or Paratethys; their speciation dating back to the Miocene-Pliocene. Though often found in groundwater, the majority of limnic halacarid species is not limited to this realm. Most of the halacarid genera presumably invaded continental waters via surface water habitats rich in interstices. Being generalists, and tolerating a wide range of environmental conditions, such as temperature, salinity, acidity, these halacarids can survive in both hypogean and epigean waters.