eviceras

Eviceras is a genus of extinct ammonoid cephalopods known from fossil records. The shells are typically planispiral, with variable degrees of involution, ornamented with ribs or tubercles, and sometimes bearing a ventral keel. Sutures are complex, a common feature in ammonoids.

Fossils attributed to Eviceras have been found in marine sedimentary rocks on several continents, indicating a broad geographic range in the oceans of the past. The genus is used in biostratigraphy as an index in certain ammonite zones, assisting correlations between separated fossil sequences.

Taxonomic placement places Eviceras within Ammonoidea; however, like many ammonite genera, it has been revised as new specimens are studied. The ecology of Eviceras was likely similar to other nektonic carnivorous ammonoids, feeding on small organisms and occupying open-water habitats.

See also: Ammonites, Cephalopoda, List of ammonite genera.