the Late Triassic only, and looked very much like modern crocodiles.
Crocodylomorphs: A group that includes crocodiles, alligators, caimans, and gavlals, known to exist from the Late Triassic to the present; not all survived to the present, including the fast-running saltoposuchians.
Rauischians: the creature’s upright front and hind legs were under the trunk of the body, making them the dominant land predator during the Triassic.
Ornithosuchian: Relatively large (10 feet [3 meters]), land predators that may have walked on all fours, but ran fast only on its hind legs; they were the most dinosaur-like of the non-dinosaur archosaurs.
Small rodent-sized mammals similar to this mouse first appeared as early as the Triassic period (iStock).
Ornithodira: The Middle and Late Triassic group of archosaurs to which the dinosaurs belong; it also includes the pterosaurs, birds, and some early forms of creatures that appear to be closely related to dinosaurs and pterosaurs.
Aerial Reptiles (Diapsids)
Gliding reptiles: The three main Late Triassic gliding reptiles used either skin membranes on the wings and legs (such as the Sharovipteryx), scales (Longisquama), or fan-like wings (Kuehneosaurus)—all of which acted as an airfoil, allowing the reptiles to glide through the air; they probably did not flap their “wings” for powered flight.
Flying reptiles: The pterosaurs (they are also called pterodactyls, but that is only one subgroup of pterosaurs); the front legs (or arms) were modified into true wings by the elongation of the fourth finger, which supported a skin membrane stretching to the body; they probably flapped their wings occasionally for powered flight; they lived from the ocean shores and inland, eating fish, insects, and other small animals; they evolved during the Late Triassic period.
Mammals and Their Reptile-like Relatives (Synapsids)
Therapsids: More advanced synapsids; varied group of mammal-like reptiles that apparently evolved from the pelycosaurs, the earliest known mammal-like reptile that evolved in the Late Carboniferous period, about 290 million years ago, and went extinct in the Late Permian period; the biggest change was their ability to walk more efficiently with their limbs tucked beneath their body, whereas pelycosaurs walked with their limbs in a sprawled position; one group of therapsids gave rise to mammals, known from the Late Triassic to today.
Anomodonts: The most common subgroup were the dicynodonts, large, herbivorous, mammal-like reptiles; it includes the Lystrosaurus, a three-to six-foot(one-to two-meter-) long, pig-like animal that has been found as fossils in Australia, South Africa, India, China, and Antarctica, and hippopotamus-like Kannemeyeria, a 10-foot-(3-meter-) long animal with two big canine-like teeth in the upper jaw; they died out during the Late Triassic period.
The Elasmosaurus was one of the largest plesiosaur species to swim through Earth’s oceans. Today, some people believe that the Loch Ness monster in Scotland is a type of plesiosaur that survived the extinction of the dinosaurs (Big Stock Photo).
Cynodonts: Carnivorous, mammal-like therapsid reptiles; they walked more upright, with limbs held more underneath their bodies; some were probably wolf-like animals, and some seem to have had whiskers, pointing to the possibility of having fur, and thus, may have been warm-blooded; they evolved during the Late Permian to the Middle Jurassic; at least one group of cynodonts evolved into mammals.
Therocephalians: Existed from the Late Permian to Middle Triassic period, these therapsid reptiles had their peak during the Late Paleozoic era; they were small to medium sized, walked on all fours, and ate insects or small animals.
True mammals: Small, about the size of a rat or mouse, with the largest about the size of a cat; they were probably nocturnal; they probably ate insects or small mammals, and at least one group ate plants; they evolved in the latter part of the Triassic, at the same time as the dinosaurs first appeared. Triconodonts: Late Triassic to Late Cretaceous mammals; one of the oldest fossil mammals; three cusps of teeth in a straight row give them their name.
Haramyoids: Late Triassic to Middle Jurassic mammals; one of the oldest fossil mammals; their teeth had many cusps in at least two parallel rows.
Other Creatures
Insects: Very common; included the first species to undergo complete metamorphosis from larva through pupa to adult.
Spiders: Very common; spiders had been around for millions of years already, showing up in fossils dating back to the Cambrian period. Earthworms: Very common; earthworms had been around for millions of years already, showing up in fossils dating back to the Cambrian period.
What were the major marine animals living during the Triassic period?
There were many marine animals that swam the oceans of the Triassic, and many of the species still continue to this day. In general, the oceans held the following animals, although with new fossil discoveries, this list may eventually change.
All modern sea urchins, such as this red sea urchin off the coast of British Columbia, are descended from urchins that survived the Permian extinction (iStock).
Major Marine Animals
Reptiles (Euryapsids)
Ichthyosaurs: Also called “fish reptiles,” these were predatory sea reptiles that probably preyed mostly on shellfish, fish, and other marine reptiles; they looked similar to, and probably had some of the same habits of, modern dolphins, whales, and sharks; they lived in the oceans from the Early Triassic to Middle Cretaceous periods, probably out-competed by the mosasaurs of the Middle Cretaceous period.
Plesiosaurs: Medium to large, long-to short-necked reptiles, with bulbous bodies; their four legs were modified into paddles; they probably ate mostly fish; they lived mostly in marine environments, but some also lived in freshwater lakes; they lived from the Early Triassic to the end of the Cretaceous period and are often sighted as the model for what the Loch Ness monster is presumed to look like.
Placodonts: Large marine reptiles that had a long trunk and tail, with feet that were probably webbed; their teeth were using for crushing, and they probably ate clams and other shelled invertebrates from the ocean floor.
Nothosaurs: Small to moderate-sized marine reptile with long necks and sharp, conical teeth for spearing fish; their legs were modified flippers, rather than the paddle-shaped legs of the more advanced eurapsids; they lived from the Early to Late Triassic period.
Other Marine Creatures
Sea urchins: The few pencil urchins that survived the Permian period extinction are also the ancestors of all modern urchins; the Triassic period was also the time of the first burrowing urchins.
Corals: First relatives to the modern corals evolved during the Triassic period.
Crabs and lobsters (crustaceans): First close relatives of modern crabs and lobsters evolved during the Triassic period.
Ammonoids (chamber-shelled organisms): Ammonoids rapidly diversified during the Triassic period.
Bony fishes: Found in salt, brackish, and fresh water, and could often move back and forth among the three; they are divided into two groups based on their structure: the ray-finned (for example, the Triassic period’s Perleidus) and lobe-finned (for example, the Triassic period’s Diplurus).
Sharks: During the Triassic, the intermediate form between primitive and modern sharks evolved; the earliest sharks