Eucritta melanolimnetes, an amphibian-like creature from the Early Carboniferous of Scotland (~335 mya). About 25cm long (10″), it had a mixture of anatomical characteristics similar to baphetid stem-tetrapods, temnospondyls, and reptile-like amphibians, making its exact classification difficult. It’s currently considered to be a close relative of both the baphetids and Crassigyrinus, and it was probably close in appearance to what the common ancestor of all later tetrapods would have looked like.

Its name means “true creature from the black lagoon”, in homage to the 1954 monster movie.


Anteosaurus magnificus, a dinocephalian from the Middle Permian of South Africa (~266-260 mya). Known from several skulls and fragments of the rest of the skeleton, it was one of the largest carnivorous non-mammalian synapsids with an estimated body length of at least 5m (16′4″).

The skull of Anteosaurus [image source]

It had patches of thickened bone above its eyes forming a pair of short “horns”, as well as heavily reinforced areas around its skull roof and the sides of its lower jaw. These were probably used for head-butting behaviors, and similar adaptations are seen in other groups of dinocephalians.

The front part of its mouth was also prominently upturned, and it had enlarged “sabretooth” fangs – although these features are covered by lips in my reconstruction.

The Francevillian Biota

Life seems to have existed on Earth for over 4 billion years, but for much of that time it was primarily microscopic. And although multicellularity is known to have independently evolved multiple times, large complex forms didn’t really get started until around 600 million years ago, with the strange Ediacarans being some of the most famous early examples.

But that may not have been the first time such an evolutionary experiment happened.

A collection of fossils discovered near the city of Franceville in Gabon appear to represent an even earlier example of large multicellular life. Known as the “Francevillian biota” or “Gabonionta”, these fossils are over three times older then the Ediacarans, dating to a staggering 2.1 billion years ago during the Paleoproterozoic Era.

Over 400 specimens have been collected, representing a variety of different forms — including discs with ruffled edges, rods, rounded clusters of blobs, and elongated shapes that are sometimes attached to long “strings of beads” — with the largest reaching lengths of about 17cm (6.5”). Their age places them somewhere around the origin point of the earliest eukaryotes, and they may represent a completely unique kingdom of life unlike anything alive today.

These organisms’ appearance in the fossil record came shortly after the Great Oxygenation Event, suggesting the evolutionary development of large complex bodies is directly linked to the amount of available oxygen for aerobic respiration. Later, atmospheric oxygen dropped again, and the Francevillian biota disappeared into extinction, leaving us with only these mysterious fossils hinting at a surprisingly diverse and alien-looking period in life’s deep past.


Potanichthys xingyiensis, a fish from the Middle Triassic of China, living around 235-242 million years ago.Measuring about 15cm long (6″), it was one of the oldest known fish capable of aerial gliding – possessing a “four-winged” body plan with enlarged pectoral and pelvic fins, and an asymmetrical tail with a long lower lobe. It was also almost completely scale-less, which may have helped to reduce drag and make it more aerodynamic.

Despite the similar appearance it had no close relation to modern flyingfishes, and was instead a result of convergent evolution in a completely different lineage of the ray-finned fishes.


Inermorostrum xenops, a recently-named ancient cetacean!

Living about 30 million years ago in shallow coastal waters around the southeast USA, in what is now South Carolina, it was a member of one of the very earliest groups of toothed whales known as the xenorophids. Although only very distantly related to modern forms, xenorophids show evidence of being able to echolocate, suggesting the ability was probably ancestral to all toothed whales.

Estimated to have measured about 1m long (3′3″), Inermorostrum had a very short downturned snout and was completely toothless – specialized adaptations for suction feeding on small soft-bodied creatures on the seafloor.

Unusually for a toothed whale it also had proportionally large infraorbital foramina, openings in the bones of its snout for blood vessels and nerves to pass through. This suggests the presence of well-developed fleshy lips and possibly whiskers (as illustrated here), or maybe even an electroreceptive sense similar to some modern dolphins.


Ampelomeryx ginsburgi, a palaeomerycid ungulate from the Early Miocene of France (~17 mya). About the size of a deer, around 1m tall at the shoulder (3′3″), it was a distant relative of modern giraffids.

Males sported three distinctive ossicone-like ‘horns’ – two over their eyes and a third forked one at the back of the skull – and protruding tusks like some modern deer, which probably served a similar purpose in fights against each other.


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.


Dinomischus isolatus, an enigmatic animal from the mid-Cambrian Burgess Shale Formation in British Columbia, Canada (~505 mya). Only about 2cm (0.8″) in total length, it had a soft cup-shaped body topped with a whorl of about 20 solid plate-like “petals”, and lived attached to the seafloor by a thin stalk.

Impressions of its internal anatomy show the presence of a U-shaped gut, with its mouth and anus positioned next to each other in the center of the “petals”. It probably fed in a similar manner to crinoids, filtering small particles of food from the surrounding sea water.

But what type of creature it actually was is still unknown. Although comparisons have been made with several different groups – particularly the tiny entoproctsDinomischus doesn’t seem to quite fit in anywhere.

Despite this ongoing mystery, a few other similar fossils have been found that seem to be its relatives. Specimens of another species of Dinomischus from slightly older deposits in China show different “petal” shapes, and have been named as D. venustum. Another Burgess Shale animal called Siphusauctum gregarium may also be closely related.

Balbaroo fangaroo

An early relative of kangaroos, Balbaroo fangaroo. Known from a couple of partial skulls discovered at the Riversleigh World Heritage Area in Queensland, Australia, it lived during the Early Miocene (~23-16 mya) and was probably about the size of a cat, around 45-60cm long (18-24″) not including the tail.

It had unusually enlarged canine teeth forming prominent “fangs” – hence its species name – which may have been used for display and fighting in a similar manner to some ungulates such as water deer and camelids.

Based on the skeletons of other closely related species, it probably wasn’t able to hop. Instead it would have moved around quadrupedally, and the shape of its feet suggest it was also capable of climbing like a modern tree kangaroo.


Mirischia asymmetrica, a theropod dinosaur from the Early Cretaceous of Brazil (~112-99 mya). Although known only from its hips and a few other partial bones, these pieces were so well-preserved that it was given a genus name that translates to “wonderful pelvis”.

In life it would have been about 2m long (6′6″), but since the known fossil represents a subadult its full-grown size may have been a little bit larger. It was probably a member of the compsognathids, closely related to Compsognathus and Aristosuchus – which would make it the only representative of that family currently known from the Americas.

The ischium bones of Mirischia’s pelvis were oddly asymmetrical, hence the species name ‘asymmetrica’, with one side featuring a hole and the other side only having a notch in the same position. The fossil specimen also had thin-walled bird-like bones, and soft-tissue impressions of intestines and a posterior air sac.