Trigonia
# Trigonia

Trigonia is an extinct genus of saltwater clams, fossil marine bivalve mollusk in the family Trigoniidae. The fossil range of the genus spans the Paleozoic, Mesozoic and Paleocene of the Cenozoic, from 298 to 56 Ma.

## Description

The genus Trigonia is the most readily identifiable member of the family Trigoniidae, having a series of strong ribs or costae along the anterior part of the shell exterior. They are the first representatives of the family to appear in the Middle Triassic (Anisian) of Chile and New Zealand. The first European examples (Trigonia costata Parkinson) appear in the Lower Jurassic (Toarcian) of Sherborne, Dorset and Gundershofen, Switzerland.

## Species

The following Trigonia species have been described:

* T. analoga
* T. antiqua
* T. castani
* T. castrovillensis
* T. coqueiroensis
* T. costata
* T. cragini
* T. depauperata
* T. eufaulensis gabbi
* T. eufaulensis moorei
* T. guildi
* T. hemisphaerica
* T. imbricata
* T. interlaevigata
* T. intersitans
* T. kitchini
* T. maastrichtiana
* T. maloneana
* T. marginata
* T. mearnsi
* T. montanaensis
* T. orientalis
* T. papuana
* T. picteti
* T. plana
* T. pseudocaudata
* T. pseudocrenulata
* T. pullus
* T. rebouli
* T. reesidei
* T. resoluta
* T. reticulata
* T. saavedra
* T. semiculta
* T. somaliensis
* T. stantoni
* T. stolleyi
* T. suborbicularis
* T. sulcata
* T. taffi
* T. thierachensis
* T. undulatocostata
* T. vyschetzkii
* T. weaveri

## Distribution

Fossils of Trigonia have been registered in:

### Permian

Bolivia (Copacabana Formation)

### Triassic

Austria, China, Italy, the Russian Federation, United States (Alaska, Idaho), and Vietnam.

### Jurassic

Afghanistan, Argentina, Canada (Alberta, British Columbia, Yukon), Chile, Colombia (Valle Alto Formation, Caldas), Egypt, Ethiopia, France, Germany, Greenland, India, Iran, Japan, Kenya, Luxembourg, Madagascar, Morocco, New Zealand, Poland, Portugal, the Russian Federation, Saudi Arabia, Somalia, Spain, Tanzania, Thailand, Tunisia, the United Kingdom, United States (Alaska, California, Idaho, Montana, Nevada, Oregon, Texas, Utah, Wyoming), and Yemen.

### Cretaceous

Afghanistan, Algeria, Antarctica, Argentina, Armenia, Australia, Brazil, Bulgaria, Canada (British Columbia), Chile, Colombia (Yuruma Formation, La Guajira, Macanal Formation, Eastern Ranges), Egypt, France, Germany, Greenland, Hungary, Italy, Lebanon, Mexico, the Netherlands, New Zealand, Papua New Guinea, Peru, Portugal, Serbia and Montenegro, South Africa, Spain, Switzerland, Tanzania, Turkmenistan, Russian Federation, Ukraine, the United Kingdom, United States (Arizona, California, Delaware, Mississippi, New Jersey, North Carolina, Tennessee, Texas), Venezuela, and Yemen.

### Paleocene

Argentina (Cerro Dorotea Formation)

