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.

Titanoboa

Titanoboa cerrejonensis, a boine snake from the Mid-to-Late Paleocene of Colombia, South America (~60-58 mya). Estimated to have reached lengths of up to 12-14m (39-46′) it was one of the largest known snakes of all time, about twice the length of the biggest modern anacondas and pythons. It was probably able to reach such a huge size due to a combination of factors – mainly a very warm climate and the absence of large terrestrial predators immediately following the K-Pg extinction a few million years earlier.

Despite frequently being depicted eating dyrosaurid crocodiles, the anatomy of Titanoboa’s skull suggests it primarily fed on fish. Considering that some of the fish in its tropical riverine habitat were some of the largest available prey in the area, reaching around 3m in length (10′), a piscivorous diet would actually make a lot of sense for a such a big snake.

Unsolved Paleo Mysteries Month #12 – Muddled Mosasaurs

Numerous groups of reptiles have “returned to the water” and become aquatic over the last three hundred million years, but tracing their direct ancestry can be surprisingly difficult. Highly modified and specialized anatomy, lack of transitional forms, and similar features convergently evolving multiple times can all obscure relationships, making it hard to properly classify them.

We’re only just starting to figure out the true origin of turtles (they’re probably archosauromorphs), and they’re a marine reptile group with living members.

Some of the completely extinct ones are even more uncertain. For example: mosasaurs. (Represented here by the eponymous Mosasaurus.)

While some semi-aquatic early mosasaurs are known, and they seem to be closely related to aigialosaurs and dolichosaurs, their exact placement within the squamates is a lot less clear. Traditionally they were regarded as the sister group to snakes, but some studies have found them to be closer to monitor lizards instead, and others have even placed them as much more basal scleroglossans. Their classification in phylogenetic analyses is “highly unstable”, changing depending on what other reptile groups are included, so there’s no real current consensus.

(And even if they are most closely related to snakes, that doesn’t necessarily help much – the exact origin and evolution of snakes is still very poorly known, too!)