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″).
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.
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.