The fossil record and the origin of ticks (Acari: Parasitiformes: Ixodida).

Ticks are obligate hematophagous ectoparasites of terrestrial vertebrates. Hypotheses on the origin of ticks have been proposed based on tick-host associations and the total-evidence approach analysis of morphological and molecular characters. Nevertheless, the origin of ticks remains a controversial issue. Here, I revised the tick fossil record including reports from the literature and the description of 7 new specimens. The analysis of fossil ticks provides few clues to tick evolution but does not contradict recent hypotheses based on total-evidence approach analysis that place the origin of ticks in the Cretaceous (65-146 mya) with most of the evolution and dispersal occurring during the Tertiary (5-65 mya).