Evolution and systematics

The earliest unequivocal record of the order Neritopsina is Late Sularian-Devonian (428-374 million years ago). Earlier Ordovician records are based on protoconch and adult shell similarities. The Neritopsina were noted as being very distinct from other "archaeogastropods" in the early twentieth century, but only since the 1970s has that placement been broadly accepted.

Neritopsina coil their shells differently than other coiled gastropods and therefore lack a central shell axis, the columella, and most species absorb the internal partitions of the shell as they grow, permitting the snail's body to be more limpet-like rather than coiled, irrespective of its shell.

The Neritopsina are the first clade in the gastropod lineage that has undergone the extensive evolutionary radiations observed across the Gastropoda. The group has shell morphologies that range from coiled conical snails (Hydrocenidae) to limpets (Phenacolepadidae), and even slugs (Titiscaniidae). While conical shells are seen in Hydrocenidae, none appear to have developed very high-spired shells. Multiple terrestrial (Helicinidae, Hydrocenidae) and freshwater invasions have oc curred (Neritidae), with some freshwater taxa still having an estuarine or marine larval phase.

The order Neritopsina contains the families Neritidae, Phenacolepadidae, Neritopsidae, Helicinidae, Hydrocenidae, and Titiscaniidae.

Was this article helpful?

0 0
Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

Get My Free Ebook


Post a comment