Barbaturex

Barbaturex morrisoni, a large herbivorous lizard which lived about 40-37 million years ago during the Eocene. Known from Myanmar in Southeast Asia, it’s estimated to have reached lengths of 1.4-1.8m (4′7″-5′10″) and was closely related to modern spiny-tailed lizards.

It had a row of bony knobs along the edges of its lower jaw, which may have supported some sort of display structure. I’ve given it some fleshy double-dewlaps here, and a spiky tail similar to its relatives, but since it’s only known from fragmentary fossils these features are pretty speculative.

Surprisingly Barbaturex was much bigger than a lot of the herbivorous ungulate mammals around at the time, and was also larger than most of the local carnivores – a very different situation to modern ecosystems, where even the biggest plant-eating lizards are still smaller than ungulates.

Nicrosaurus

Nicrosaurus kapffi from the Late Triassic of Germany, about 221-205 million years ago. Although rather crocodile-like in appearance, this 4-6m long (13′-19′8″) animal was actually part of an extinct group called phytosaurs – long-snouted heavily-armored reptiles with their nostrils high up on their heads near their eyes.

Phytosaurs’ exact evolutionary relationships are still disputed, with opinions currently going back and forth between them being archosauriformes or an early branch of the croc lineage within the true archosaurs. But either way they weren’t directly ancestral to modern crocodilians, and instead developed a very similar body plan via convergent evolution.

While some phytosaurs had very slender gharial-like snouts and probably fed mostly on fish, others like Nicrosaurus had much more robust jaws and seem to have secondarily adapted to a terrestrial predator lifestyle. They had longer limbs and a more upright posture than their semi-aquatic relatives, and enlarged fangs at the hooked tips of their jaws that may have been used to deliver a powerful stabbing blow to their prey.

Nicrosaurus also had a raised bony crest running along its snout, which I’ve depicted here as supporting an even larger soft-tissue display structure.

Eudibamus

Eudibamus cursoris, a bolosaurid from the Early Permian of Germany (~284-279 mya).

Although very lizard-like in appearance, this animal was actually part of a completely extinct group known as parareptiles – a diverse group of early sauropsids who were once thought to be the ancestors of turtles, but are now considered to instead be the evolutionary cousins to the true reptiles.

With a total length of about 25cm long (8-10″), the structure and proportions of its limbs suggest it could run fast on its hind legs, making it one of the earliest known examples of bipedal locomotion. Since its teeth were adapted for a herbivorous diet, it wasn’t using its speed to chase down prey but was instead probably sprinting away from predators.

But unlike the sprawling running of some modern lizards, Eudibamus may have been capable of holding its legs in a more upright position directly under its body, convergently evolving a more energy-efficient posture similar to that of later bipedal animals like dinosaurs.

Sclerocormus

Sclerocormus parviceps, an unusual ichthyosauriform from the Early Triassic of China (~248 mya).

Its short toothless snout suggests it was a suction feeder, using water pressure differences to pull small soft-bodied prey straight into its mouth like a syringe.  Along with a heavily built body similar to those of hupehsuchians, and a very long tail that made up over half of its 1.6m length (5′3″), it was probably a fairly slow swimmer living in shallow coastal waters.

It was a close relative of Cartorhynchus, and may have been similarly capable of hauling itself onto land like a modern pinniped.

Colobomycter

Colobomycter pholeter, a parareptile from the Early Permian of Oklahoma, USA (~289 mya). Although known only from partial skull fossils, its full size was probably around 30cm long (1′).

It had huge fangs at the front of its jaws, along with a few other enlarged teeth further back, all with serrated edges that show it was clearly a predator. What exactly it was feeding on with this unusual tooth arrangement is unknown – but proposed ideas include piercing through hard-shelled arthropods, or stabbing into smaller vertebrate prey.