The crab genus Rathbunopon is exclusively known from Cretaceous rocks, mainly from Europe. Here two new European localities are presented: one in the Albian/Cenomanian of northern Spain yielding well-preserved specimens of Rathbunopon obesum, and one from the lower Aptian
at the German-Austrian border yielding Rathbunopon schrattenkalkensis n. sp. Both are found in association with coral reefs. Based upon a revision of the genus, we place Rathbunopon within the Prosopidae. Furthermore, Homolopsis tuberculata is transferred to Rathbunopon.
Placement of 'Rathbunopon' atherfieldensis in Rathbunopon is not tenable; we place it here within the Homoloidea in open nomenclature. With the addition of R. tuberculatum, Rathbunopon is interpreted to have evolved in the Hauterivian and diversified in the Albian/Cenomanian.
Whereas R. obesum resided mainly in reefal settings, Rathbunopon species lived in a variety of environments and are suggested to be generalists.
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