Hovasaurus

The Permian-Triassic extinction 252 million years ago was the most severe mass extinction in Earth’s history, so incredibly devastating that it’s been nicknamed the “Great Dying” – but there were still some animals that somehow just… didn’t seem to really notice it at all.

And one of these surprisingly resilient species was Hovasaurus boulei.

It was part of a group known as the tangasaurids, a fairly early evolutionary branch of diapsid reptiles from Madagascar and East Africa that originated sometime in the mid-Permian, just before the common ancestor of modern lizards and archosaurs.

Hovasaurus lived in Madagascar both just before and for some time after the Great Dying, dating to around 252-247 million years ago. Growing up to about 90cm long (~3′), it was one of the largest tangasaurids and was also highly specialized for aquatic life in freshwater rivers, with an eel-like tail twice the length of the rest of its body and heavy thickened ribs.

Hundreds of fossils have been found representing life stages from hatchling to adult, and juvenile Hovasaurus actually seem to have been almost fully aquatic – they had proportionally shorter limbs and may have behaved similarly to modern sea turtles, crawling into the water shortly after hatching and only returning to land as adults once they had longer better-developed legs.

Many fossils also preserve clusters of pebbles in their abdominal cavities, which are thought to have been used as extra ballast to help weigh them down in the water when hunting small fish and invertebrates.

It’s not entirely clear why these odd little aquatic reptiles were apparently unaffected by the Great Dying. Perhaps, much like the many freshwater species that survived though the later end-Cretaceous mass extinction, Hovasaurus was simply very good at dealing with sudden changes in its environment and food availability due to the variability of river habitats, and was able to weather though the worst of the extinction without much trouble. 

Or maybe it was just one of the lucky ones.

Eons Roundup 4

Some more recent commission work for PBS Eons!

The entelodonts Eoentelodon and Brachyhyops, from “The Hellacious Lives of the Hell Pigs”
https://www.youtube.com/watch?v=trJpxwMGoCw

The early ichthyosaur Tholodus and the mosasaurPluridens, from “When Ichthyosaurs Led a Revolution in the Seas”
https://www.youtube.com/watch?v=V342aXQs9XY

The early bats Onychonycteris and Icaronycteris, from “When Bats Took Flight”
https://www.youtube.com/watch?v=zWeYCULC0UQ

Island Weirdness #26 – The Mauritian Giant Skink

Along with its unique birds, Mauritius was also home to many endemic reptile species. In the absence of terrestrial mammals giant tortoises were the largest herbivores on the island, and various geckos, skinks, and snakes helped to fill out the rest of the vertebrate ecosystem.

Leiolopisma mauritiana was a very large skink, one of the biggest ever known to have existed with a total length of around 80cm (2′7″). Its ancestors originated in Australasia, over 5600km away (~3500 miles) at least 3-4 million years ago – and they must have endured a particularly long ocean rafting journey without any island hopping stops, since none of the other islands along that route seem to have ever had populations of similar skinks.

It probably lived in rocky areas, possibly also being capable of digging burrows, and would have eaten an omnivorous diet of seeds, fruits, invertebrates, and smaller lizards and birds.

By the early 1600s it was already extinct, very soon after the arrival of humans, probably due to predation from invasive mammals like rats. However, its half-sized close relative Leiolopisma telfairii does still survive on rat-free Round Island a short distance to the north of Mauritius, and recent conservation efforts have been rebuilding its population and setting up new colonies on other nearby small islands.

Xinpusaurus

Thalattosaurs were a weird and rather mysterious group of Triassic marine reptiles. It’s not clear where they actually fit on the reptile evolutionary tree (we know they’re diapsids, but nobody can really agree on anything more definite than that), and they had some very strange skulls that seem to have been highly specialized for something, although their actual function is still unknown.

Xinpusaurus kohi here is known from the Late Triassic of China (~232-221 mya). About 1.3m long (4′3″), with half of that being its paddle-like tail, it had an elongated upper jaw that formed a protruding pointed spear-shaped snout.

It’s not clear whether this odd snoot was an adaptation for hunting similar to the long bills of swordfish – there’s quite a bit of variation in length and shape between different individual specimens – or if it was serving some other purpose like the sexually dimorphic noses of some modern lizards.

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.