內角石

內角石（學名：）是一屬已滅絕的鸚鵡螺類。生存在奧陶紀的海洋中。巨大的內角石長度約為13英呎（3.5公尺），是生活在古生代海洋中的巨大生物之一。成年的內角石可能是隱藏在海底的伏擊型掠食者，必要時移動以取得優勢。

物種
*Endoceras annuliferum
*Endoceras aristides
*Endoceras baculoides
*Endoceras baylorense
*Endoceras calvini
*Endoceras champlainense
*Endoceras deparcum
*Endoceras durinum
*Endoceras eburneolum
*Endoceras fulgur
*Endoceras glaucus
*Endoceras hageri
*Endoceras hudsoni
*Endoceras indigator
*Endoceras knighti
*Endoceras lamottense
*Endoceras lawrencense
*Endoceras logani
*Endoceras magister
*Endoceras microlobatum
*Endoceras perannulatum
*Endoceras philipsburgense
*Endoceras primigenium
*Endoceras proteiforme
*Endoceras raymondi
*Endoceras richardsoni
*Endoceras sansabaense
*Endoceras seticornium
*Endoceras tityrus
*Endoceras trundlesense
*Endoceras warthini
*Endoceras yellvillense

參考文獻
*Flower, R. H. 1955, Status of Endoceroid Classification; Jour. Paleon. V 29. N.3 May 1955 pp 327–370
*Teichert, C. 1964. Endoceratoidea; Treatise on Invertebrate Paleontology, Part K; Geol Soc of America and University of Kansas Press