Trigonia

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: 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) == References ==