A tardigrade in Dominican amber

Tardigrades are a diverse group of charismatic microscopic invertebrates that
are best known for their ability to survive extreme conditions. Despite their
long evolutionary history and global distribution in both aquatic and terrestrial
environments, the tardigrade fossil record is exceedingly sparse. Molecular
clocks estimate that tardigrades diverged from other panarthropod lineages
before the Cambrian, but only two definitive crown-group representatives
have been described to date, both from Cretaceous fossil deposits in North
America. Here, we report a third fossil tardigrade from Miocene age
Dominican amber. Paradoryphoribius chronocaribbeus gen. et sp. nov. is the
first unambiguous fossil representative of the diverse superfamily Isohypsibioidea,
as well as the first tardigrade fossil described from the Cenozoic. We
propose that the patchy tardigrade fossil record can be explained by the preferential
preservation of these microinvertebrates as amber inclusions, coupled
with the scarcity of fossiliferous amber deposits before the Cretaceous.