Tryblidiida

Tryblidiida is a taxon of monoplacophoran molluscans containing the only extant representatives: 29 species are still alive today, inhabiting the ocean at depths of between 175 and 6500 metres (531.34 and 21,325.5 feet).

History of discoveries

Before 1952, these organisms were known only from the fossil record, ranging from the early Cambrian to the mid-Devonian periods (ca. 550 - 380 million years ago). The first captured living monoplacophoran was Veleropilina zografi in 1896, but at that time it was described as if it were an archaeogastropod, a true limpet, mainly because of its patelliform (limpet-like) shell. This species was finally revealed to be monoplacophoran 87 years later, in 1983.

In April 1952, a living specimen was collected from deep depths in the Middle America Trench off Costa Rica's Pacific coast. In 1957 that species was described and named Neopilina galatheae by its discoverer, Danish biologist Henning Mourier Lemche (1904–1977). An expert in the field has called this discovery "one of the greatest sensations in the [twentieth] century." As of 2008, there were 31 living species known, discovered in waters from 200 meters in depth to hadal depths, or more than 6,000 meters in the deepest ocean trenches.