While this animal might look like some sort of deer or horse, it was actually only distantly related to any modern hoofed mammals.
This is Thoatherium from the Early Miocene (~17-16 mya) of Argentina. About 70cm long (2′3″), it was related to the weird llama-like Macrauchenia and was part of an extinct group of ungulates (the Meridiungulata) which evolved during South America’s time as an isolated island continent.
It was adapted for fast running, with long legs and only a single horse-like hoof on each foot – but it was even more one-toed than modern horses are, having no remaining “splint bones” from vestigial side toes.
The Jamaican ibis (Xenicibis xympithecus) was a bird unique to the Caribbean island of Jamaica. One of only two known types of completely flightless ibises, it was similar in size to a chicken – probably around 75cm long (2′5″) and weighing 2kg (4.4 lbs).
It had some incredibly unusual wing anatomy, with strengthened bones, a proportionally short forearm, and the “hand” section modified into a thick club-like shape. Some remains show evidence of blunt-force injuries, suggesting these birds fought each other by swinging around their heavy wings like baseball bats.
Its bones have found in several cave deposits which are difficult to accurately date, but are likely to be somewhere between 10,000 and 2,200 years old. It’s unclear whether Xenicibis was still around when humans first colonized the island, but if so it was probably driven to extinction soon after.
Shringasaurus indicus, an archosauromorph reptile from the Middle Triassic of India (~247-242 mya). About 3-4m long (9′10″-13′1″), it was part of a group known as the allokotosaurs, specialized herbivores with lizard-like bodies, and was related to the strange long-beaked Teraterpeton.
Partial remains of about seven different Shringasaurus individuals of varying ages have been found, with several of them having large curving horns over their eyes convergently similar to those of the later ceratopsids. A couple of adult specimens lack horns entirely, suggesting the feature was sexually dimorphic with only the males developing ornamentation – a very rare arrangement among archosauromorphs, but similar to some horned mammals.
Linguamyrmex vladi, an ant from the Late Cretaceous of Myanmar (~99 mya). Part of an extinct group known as the Haidomyrmecini, or “hell ants”, it measured about 5mm long (0.2″) and is known from several individuals in amber.
It had huge scythe-shaped mandibles and a horn-like appendage on its head which together formed a powerful trap-jaw mechanism, snapping vertically shut when a pair of long sensitive trigger hairs touched against a target. One specimen was preserved close to a large soft-bodied beetle larva, which may have been an intended prey item.
When closed, the mandibles formed a tube-like channel to Linguamyrmex’s mouth, allowing it to suck out the “blood” from its impaled victims – and inspiring its species name, referencing Vlad Dracula.
The horn was also reinforced with metal particles in the chitinous exoskeleton, strengthening it against the impact of its closing jaws.
Gamerabaena sonsalla, a baenid freshwater turtle that lived at the very end of the Cretaceous (~66 mya) in North Dakota, USA. Known only from a single skull, its full size is uncertain, but it may have reached lengths of around 50cm (1′7″).
Its genus name was inspired by Gamera, a fictional giant turtle from a series of Japanese kaiju movies.
Baenids first appeared in the mid-Cretaceous (~112 mya) – although their ancestry may go as far back as the Late Jurassic (~150 mya) – and were part of an early lineage of the cryptodiran turtles, the grouping which includes most freshwater turtles and terrapins, all terrestrial tortoises, and all sea turtles. However, unlike many of the their modern cousins, they weren’t capable of fully retracting their heads inside their shells.
They survived well through the K-Pg mass extinction, with several species found on both sides of the boundary, but eventually went extinct in the mid-Eocene (~42 mya).
Ikrandraco avatar, a pterosaur from the Early Cretaceous of China (~120 mya). Although it was close relative of the well-known Pteranodon it was much smaller, with an estimated wingspan of around 1.5m (4′11) – similar in size to a large seagull.
Its name was based on the fictional ikran creatures from the 2009 movie Avatar, in reference to similarity of the the large crests on their lower jaws.
A hook-shaped projection at the back of the crest may have been an attachment point for a pelican-like throat pouch. The paleontologists who described Ikrandraco also suggested that its crest could have been used for skim-feeding, although this is a highly controversial idea among pterosaur specialists.
Zuul crurivastator, an ankylosaur from the Late Cretaceous of Montana, USA (~75 mya).
One of the most complete ankylosaurids ever found in North America, it’s known from a full skeleton about 6m long (20′). Much of its bony osteoderm armor is preserved in life position, along with skin impressions and the remains of keratinous scales and spike sheaths – although so far only the skull and tail have actually been fully prepared and described.
(The fuzz on this reconstruction is highly speculative, but since it’ll likely end up inaccurate anyway once of the rest of the body is fully described… why not have some fun with it?)
Its genus name was inspired by its skull’s resemblance to Zuul the Gatekeeper from the 1984 movie Ghostbusters, while its species name translates to “destroyer of shins” in reference to its especially large tail club.
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″).
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.