Fossil records. This genus is known in the fossil record from the Triassic to the Eocene (from about 247.2 to 33.9 million years ago). Fossils of species within this genus have been found in Europe, United States, Canada, China, Japan, Pakistan, Colombia (Coquina Group, La Guajira), India, Thailand, Indonesia, Jordan, Lebanon, Egypt, Madagascar, Russia, Ukraine, Mexico and Peru.