Xenacanthus, meaning “strange spine”, was a 3 foot long shark-like freshwater fish which lived in North America, South America, Europe, and Asia from the second half of the Carboniferous Period to the end of the Permian Period, approximately 323-251 million… Read More ›
Triassic Period
Shonisaurus
Shonisaurus was an absolutely gargantuan ichthyosaur which swam off North America’s Pacific coast during the middle of the Triassic Period 227 million years ago. Shonisaurus was one of the largest ichthyosaurs to have existed, measuring 45 feet long. Only a… Read More ›
Gualolepis
Gualolepis was a prehistoric freshwater fish which lived in western Argentina during the middle of the Triassic Period 235-234 million years ago. Only two specimens of this fish have been found (collection ID codes: PULR 106 and PULR 107), and… Read More ›
Challaia
Challaia was a genus of prehistoric freshwater fish which lived in South America during the early and middle Triassic Period 240-230 million years ago. Its fossils have been found within several geological formations in western Argentina. Challaia belonged to the… Read More ›
Strophodus
Strophodus was a 10 foot long hybodont shark which specialized in eating shellfish. It appeared during the early Jurassic Period and went extinct during the early Cretaceous Period, making it one of the longest-lived shark genera in the fossil record…. Read More ›
Synechodus
Synechodus was a genus of prehistoric saltwater shark which lived from the early Permian Period until the late Eocene Epoch of the Paleogene Period, 290 to 37 million years ago (Ivanov 2005, pages 127-138). Fossils of this animal reached around… Read More ›
Diplurus
Diplurus was a 3 foot long freshwater coelacanth fish which lived in the northeastern United States during the late Triassic and early Jurassic Periods, approximately 220-190 million years ago. It is divided into three species: D. longicaudatus, D. newarki, and… Read More ›
Lissodus
Lissodus was a prehistoric shark which lived from the early Triassic to the middle Cretaceous Period, about 250 to 110 million years ago, give or take. Named in 1835, it was a member of a group of sharks called the… Read More ›
Polyacrodus
NOTE: This article was originally published on May 4, 2022. On December 30, 2025, it was updated and re-uploaded. Polyacrodus was a genus of prehistoric shark, composed of several species, with fossils found in North America, South America, Europe, Asia, and… Read More ›
Semionotus
Semionotus was a genus of prehistoric fish which lived throughout the world during much of the Mesozoic Era. It was named by the famous Swiss ichthyologist and paleontologist Louis Agassiz in 1843 (type species: Semionotus bergeri). Semionotus first appeared during… Read More ›