Triassic first appearances

Thalattosauria (Greek for "sea lizards") is an extinct order of marine reptiles that lived during the Triassic Period. Thalattosaurs were diverse in size and shape, and are divided into two superfamilies: Askeptosauroidea and Thalattosauroidea.

subclass of echinoderms

Mawsoniidae is an extinct family of prehistoric coelacanth fishes which lived during the Triassic to Cretaceous periods. Members of the family are distinguished from their sister group, the Latimeriidae (which contains the living coelacanths of the genus Latimeria) by the presence of ossified ribs, a coarse rugose texture on the dermatocranium and cheek bones, the absence of the suboperculum and the spiracular, and reduction or loss of the descending process of the supratemporal.

Cidaris is a genus of pencil sea urchins.

Tanystropheidae is an extinct family of archosauromorph reptiles that lived throughout the Triassic Period, often considered to be "protorosaurs". They are characterized by their long, stiff necks formed from elongated cervical vertebrae with very long cervical ribs. Members of the group include both terrestrial and aquatic forms. While some tanystropheids were small lizard-like animals, other tanystropheids such as Tanystropheus were large animals that had necks that were several meters long, longer than the rest of their bodies.

thumb|left|240px|An impression of Ceresiosaurus eating a small aquatic animal

Mastodonsauridae is a family of capitosauroid temnospondyls. Fossils belonging to this family have been found in North America, Greenland, Europe, Asia, and Australia. The family Capitosauridae is synonymous with Mastodonsauridae.

Lydekkerinidae is a family of stereospondyl temnospondyls that lived in the Early Triassic period. During this time period, lydekkerinids were widely distributed, with putative remains reported from Russia, Greenland, India, South Africa, Madagascar, Australia, and Antarctica. In contrast to most other stereospondyls, lydekkerinids were relatively small-bodied (most with skulls less than 10 cm in length). The type genus is Lydekkerina, the namesake of the family and the best-known lydekkerinid.

Williamsoniaceae is a family within the Bennettitales, an extinct group of seed plants. Members of this family are believed to have been around two meters tall and with widely serrate leaves along a central stem. Reproductive organs of the Williamsoniaceae have varied widely in the fossil record but almost all have been found to be borne on stalks emerging from a ring of leaves. thumb|Fossils and schematic diagram of Pterophyllum (plant)|Pterophyllum bavieri from the Late Triassic ([[Rhaetian) of northern Iran, Shemshak Group, A and B: leaves attached to a branch C: complete leaf]]

The Caytoniales are an extinct order of seed plants known from fossils spanning from the Middle Triassic (Anisian) to the Late Cretaceous (Campanian). They are regarded as "seed ferns" because they are seed-bearing plants with fern-like leaves. Although at one time considered angiosperms because of their berry-like cupules, that hypothesis was later disproven. Nevertheless, many authorities consider them likely ancestors or close relatives of angiosperms. The origin of angiosperms remains unclear, and they cannot be linked with any known seed plants groups with certainty.

Capitosauria is an extinct group of large temnospondyl amphibians with simplified stereospondyl vertebrae. Mainly living as piscivores in lakes and rivers, the Capitosauria and its sister taxon Trematosauria were the only major labyrinthodonts that existed during the Mesozoic in ecological niches broadly similar to those of modern crocodiles, and some grew to very large sizes. At 6 meters in length, the Mid-Triassic Mastodonsaurus giganteus is not only thought to have been the largest capitosaur, but possibly also the largest amphibian to have lived. The latest known remains are from the Rhaet

Thalattosauroidea is a superfamily of thalattosaurs, a Triassic group of marine reptiles. It was named in 1904 by paleontologist John Campbell Merriam to include the genus Thalattosaurus from California. Thalattosauroids are one of two groups of Thalattosauria, the other being Askeptosauroidea. Thalattosauroids make up the "traditional" thalattosaurs with large downturned snouts, short necks, and long, paddle-like tails.

Zamites is an extinct genus of plants in the family Williamsoniaceae that lived from the Triassic to the Eocene. This plant is reported in the Mesozoic from North and South America, Europe, Asia, Africa, and Antarctica, and in the Cenozoic only in North America.

Ceratitidae is an extinct family of ammonite cephalopods.

Plegiocidaris is an extinct genus of echinoids that lived from the Triassic to the Early Cretaceous. Its remains have been found in Asia and Europe. It was named by the paleontologist Auguste Pomel.

Baieroxylon is an extinct prehistoric genus of plants belonging to the Ginkgoaceae family during the Triassic, Jurassic, and Cretaceous Periods.

Pseudopolycentropodidae is an extinct family of scorpionflies known from the Mesozoic. Fossils are known from the Middle Triassic (Anisian) to the early Late Cretaceous (Cenomanian). It is part of Mesopsychoidea, a group of scorpionflies with siphonate proboscis. They are suggested to have been nectarivores, feeding off the liquid pollination drops and acting as pollinators for now extinct insect pollinated gymnosperms such as Bennettitales.

Whiteiidae is an extinct family of prehistoric coelacanth fishes which lived during the Triassic period. Torino, Soto, and Perea (2021) did not support this clade as it was not found to be monophyletic in their analysis, however, Ferrante and Cavin (2025) found the family to be a valid clade.

Askeptosauridae is a family of thalattosaurs within the superfamily Askeptosauroidea. Fossils have been found from Italy, Switzerland, and China. Askeptosaurids are distinguished from other thalattosaurs by their long necks and narrow skulls.

Gomphodontosuchinae is a subfamily of Triassic traversodontid cynodonts. It includes the genera Gomphodontosuchus (the type genus), Exaeretodon, Santagnathus, Siriusgnathus, Menadon, Proexaeretodon, Protuberum, Ruberodon and Scalenodontoides.

Askeptosauroidea is a superfamily of thalattosaurs, a Triassic group of marine reptiles. Askeptosauroidea is one of two major subgroups of Thalattosauria, the other being Thalattosauroidea. It includes the family Askeptosauridae and a more basal form called Endennasaurus.