A place to list many other presumably extinct reptiles that are often asociated with dinosaurs. Though he animals listed in this section are not dinosaurs, they are often included in dinosaur media and are important to learn about.
Postosuchus is one of the most popular presumably extinct reptiles. It is classified as an Archosaur, the reptiles that Dinosaurs and kin alledgedly evolved from, and therefore not considered a dinosaur. Evolutionary dating places it in the late Triassic around 228-202 million years ago, though Creationist dating methods place it at the same time as very other creature at 6,000 years ago onward since the account of Genesis states all creatures were made during Creation week and so have all lived together from the beginning.
The first fossil remains of Postosuchus were discovered in Crosby County, Texas by Ermine Cowles Case in 1922 but since there was so little to work with, the bones were assigned to Ceolophysis. Since then the taxonomy has been somewhat improved since hundreds more bones have been found.
Postosuchus is said to have been a predator but this too is speculation since teeth alone cannot prove an animals diet, but it may well have been carnivorous after The Fall.
Postosuchus was a large quadrupedal reptile that measured up to at least 13 feet long and 6.5 feet tall. There is some debate over whetehr or not Postosuchus could walk bipedally as well but so far no one is 100% sure. It's head has often been compared to that of a Tyrannosaurs' skull it terms of shape and design, one of the reasons it is believed to have been a predator. It back was covered with bony scutes that would have acted like armor, a feature in many reptiles, including dinosaurs and kin.
There is one known report of a man shooting and killing an animal that may have been a Psotosuchus in modern times, but the body was never recovered so we may never know. The existence of a Postosuchus in modern times would certainly have the same impact as Dinosaurs and kin on evolutionary timelines and beliefs, but for many overzealous humanists it would simply be assimilated into evolutionary theories like everything else.
Dimetrodon is a Synapsid or "mammal like" reptile that is believed by many to have lived on the Permian period between 280-265 million years ago. Dimetrodon means "two measures of teeth", which is a reference to the fact that it has two types of teeth, as opposed to most reptiles which have only one. Dimetrodons grew to between 5.5-15 feet in length depending on the subspecies/local variant, and weight estimates for them range from 60-550 lbs for adult specimens. The tail of these animals made up a significant portion of it's body length, despite the fact that early reconstructions by paleontologists portrayed them with short tails due to incomplete fossils.
Most fossil remains have been uncovered in the Red Beds of Texas and Oklahoma, though fossils have been uncovered in other places as well, including some recently found in Germany. While Dimetrodon is often lumped in with Dinosaurs, it is not considered a true Dinosaur based on it's anatomy, though for the sake of some conversations it makes little difference since they are also a unique Kind of reptile that is now considered extinct.
Post-Fall, Dimetrodon may well have used their large teeth to eat animal matter, but may, like still living Monitor and Tegu lizards, ate fruit and vegetable matter as well, to date, the exact diet of most presumably extinct creatures is not fully known, though even the mentioned lizards still alive both can eat fruit and vegetables.
The most iconic piece of Dimetrodon anatomy is its large sail on its back. It has long been thought that the sail was used for thermal regulation of some sort. Other theories have suggested mating rituals and warding off predators, so far there is no consensus. The relationship to mammals is based solely on the teeth, arguing that since Dimetrodon has two types of teeth, it gave rise to mammalian animals whom have multiple types of teeth.
There has been one report from Africa of an animal with a sail on its back that resembled a Dimetrodon. So far it is the only known sighting of a Dimetrodon type creature in modern times.