Diversification of the greater hydrophilines clade of giant water scavenger beetles dated back to the Middle Eocene (Coleoptera: Hydrophilidae: Hydrophilina)
Abstract
Fossil representatives of the hydrophilid genera Hydrochara Berthold, 1827, Hydrobiomorpha Blackburn, 1888 and Hydrophilus Geoffroy, 1762 were recorded at the lower Middle Eocene locality Grube Messel in Germany. Four morphospecies were recognised, including Hydrobiomorpha eopalpalis, sp. nov. showing sexually dimorphic maxillary palpomere 2 unknown in any recent or fossil species of the genus.
These fossils are the oldest known records of the mentioned genera and indicate a minimum age of 47 million years for the divergence of the Hydrobiomorpha and Hydrophilus clades. Based on these data, we assume that the diversification of the ‘greater hydrophilines’ clade predated the lower Middle Eocene.
The fossil record of the subtribe Hydrophilina is briefly reviewed, the reasons of the scarcity or absence of some genera in the fossil record are discussed, and the paleoenviromental significance of the presented fossils is discussed.