Triasacarus

Triasacarus fedelei is an extinct species of gall mite described from the Carnian of northeastern Italy. It lived as a parasite of Cheirolepidiaceae trees. The only known specimen, preserved in amber, is 0.210 mm long. Along with "Ampezzoa triassica" and an unnamed dipteran, it is the oldest arthropod found enclosed in amber.
It is possible that "Triasacarus" induced the formation of galls on the host plant.