Fossil Constraints on the Timescale of Parasitic Helminth Evolution

The fossil record of parasitic helminths is often stated to be severely limited. Many studies have therefore used host constraints constrain molecular divergence time estimates helminths. Here we review direct evidence for several these lineages belong various phyla (Acanthocephala, Annelida, Arthropoda, Nematoda, Nematomorpha, Platyhelminthes). Our compilation shows that the soft-bodied patchy, but more diverse than commonly assumed. provides ectoparasitic (e.g., worm-like pentastomid arthropods) been around since early Paleozoic, while endoparasitic (cestodes, nematodes) arose at least during, or possibly even before late Paleozoic. Nematode parasitizing terrestrial plant and animal hosts in existence Devonian Triassic, respectively. All major Platyhelminthes, Nematomorpha) had evolved Mesozoic. Interestingly, although parasitism considered derived within Metazoa, oldest Nematoda Platyhelminthes includes body fossils representatives. Furthermore, falls times based on co-evolution suggesting themselves might just as good complementary (and less circular justification) calibration associations. Data also provide obvious switches extinctions, which cautions against models pure co-divergence where use calibrations may considered.