Category: science illustration

Weird Heads Month #24: Hook-Snouted Swimmers

Thalattosaurs were another group of weird Triassic animals, found in coastal marine environments all around the world. Their evolutionary relationships are unclear beyond “they were some sort of diapsid reptile”, and they were well adapted for aquatic life, with streamlined lizard-like bodies, short limbs with webbed feet, and long paddle-like tails.

Most of them had long narrow toothy snouts, but others had odd spear-shaped noses or downturned upper jaws. 

Hescheleria rubeli here was one of the strangest, living in Europe during the mid Triassic, about 247-235 million years ago. It was one of the smaller known species of thalattosaurs, around 1m long (3’3″), and had a particularly bizarre-looking head.

A close-up of the head of the extinct marine reptile Hescheleria. The front of its snout is sharply downturned, forming a near-right-angled hooked shape, with small sharp teeth at the front of its jaws along with a pair of large conical bony projections in its lower jaw.

Its snout was so sharply curved downward that it formed a right-angled hook relative to the rest of its jaws, sort of resembling the initial interpretation of Atopodentatus but without the vertical split.

There were also small sharp teeth at the front of its mouth, along with a pair of large conical bony projections on its lower jaw.

This weird arrangement must have been highly specialized for something, but its actual function is still unknown. One suggestion is that the large jaw-spikes were used to crunch into hard-shelled prey, although there doesn’t seem to have been any reinforced surface in the upper jaw for them to crush against.

But I personally wonder if maybe these jaws were the equivalent of the hooked kypes seen in the males of some modern salmonid fish – structures associated with dominance fighting.

Weird Heads Month #23: Dome-Headed Claw-Horses

Much like Platybelodon from a few entries back, chalicotheres look like a fictional creature design rather than something that actually existed.

These animals were odd-toed ungulates related to modern horses, tapirs, and rhinos, who ranged across Africa, Eurasia, and North America for a large chunk of the Cenozoic. Instead of hooves they had large claws on their feet, and they appear to have occupied the same sort of ecological niche as ground sloths or therizinosaurs – sitting or rearing up on their hind legs to browse on high vegetation, using the hook-like claws on their forelimbs to pull down and strip branches.

There were two different lineages of chalicotheres which developed along slightly different evolutionary paths: the knuckle-walking gorilla-like chalicotheriines and the more goat-like schizotheriines.

Tylocephalonyx skinneri here was one of the latter group, known from the Miocene of North America about 16-13 million years ago. Standing about 2m tall at the shoulder (6’6″), it had the same sort of chunky body as other schizotheriines and walked around with its large front claws held up to keep them raised away from the ground.

But there was also an unusual feature on its otherwise rather horse-like head – a large bony dome on top of its skull, like a mammalian version of a pachycephalosaur.

It probably used its dome in the same way as the dinosaurs it convergently resembled, headbutting or flankbutting in fights with each other.

Weird Heads Month #22: Flat Headed Crocs

The heads of modern crocodilians are already pretty amazing, with their high-set eyes and nostrils, moveable ear flaps, numerous dermal pressure receptors, and a distinctive chaotic “scaly” surface texture that’s actually formed from cracks in thick stiff skin.

And back during the Late Cretaceous of West Africa, about 95 million years ago, there was a huge variety of odd-looking crocdyliformes all sharing a river delta environment and specializing in different ecological niches from terrestrial to aquatic. There were species with nicknames like “duck croc“, “boar croc“, and “pancake croc” – but one of the most intriguing of them all was Aegisuchus witmeri, the “shieldcroc”.

Known only from the back end of its skull, Aegisuchus seems to have had a very wide and flat head, possibly similar in shape to those of the “pancake crocs” which it may have been closely related to. From the sheer size of the known remains it must have been rather big, with a skull at least 2m long (6’6″) and a total length of around 10m (32’10”).

But its weirdest feature was a raised circular bony boss in the middle of its forehead. Unlike any other known croc, the bone around this area shows evidence of deep blood vessel channels, suggesting it was anchoring a more extensive keratinous “shield”. Much like the “horns” seen on some crocodilian species this was probably used for territorial and mating displays, but its extensive blood supply may have also allowed it to play a role in body temperature regulation.

Aegisuchus would have had a fairly weak bite, and may have fed more like a pelican than a modern croc, snapping up fish and other small animals with its gaping mouth. Its jaw mechanics also resembled those of the Triassic amphibian Gerrothorax’s “toilet seat head”, so it could have had a similar hunting strategy, laying motionless on riverbeds with its mouth wide open, waiting for prey to swim close enough to catch.

Weird Heads Month #21: Honking Hadrosaurs

The ceratopsians and pachycephalosaurs weren’t the only ornithischian dinosaurs to do weird things with their skulls.

The hadrosaurs are commonly referred to as “duck-bills” (despite how their beaks weren’t actually duck-like at all), and are famous for the elaborate crests seen on some of the group’s members, with shapes ranging from lobes to helmets to hatchets to spikes – and even some of the apparently crestless species are now known to have sported fleshy combs instead of the bony structures seen in their relatives.

But by far the most recognizable of the crested hadrosaurs is Parasaurolophus walkeri, with its long curved backwards-pointing tubular crest.

This particular species was mid-sized for the genus, growing up to around 10m long (32’10”) and is known from Western North America during the Late Cretaceous, about 76-73 million years ago.

Its crest was intermediate in size and shape between the other two known species. The larger Parasaurolophus tubicen had a longer and slightly straighter crest, while the smaller Parasaurolophus cyrtocristatus had a shorter more strongly curved one. Juveniles developed these crests as they matured, starting off with much smaller bumps on their snouts that gradually grew backwards and upwards.

Some hadrosaur crests were purely for visual display, but in the lambeosaurine lineage that Parasaurolophus belonged to they also incorporated complex looping nasal passages that were probably used as resonating chambers, allowing each species to make a unique-sounding loud bellowing call to communicate with each other.

There are also rumors of a currently-undescribed specimen of Parasaurolpphus that has preserved soft tissue around its crest, possibly a keratinous covering or skin flaps that made it appear even larger and more flamboyant in life than the underlying bone. So I’ve given this reconstruction a speculative structure like that, along with hoof-like claws on its hands similar to those recently revealed for Edmontosaurus.

Weird Heads Month #20: Shovel-Tuskers

With their odd-looking skulls, long tusks, and their noses and upper lips modified into tentacle-arm-like trunks, modern elephants are the sort of animal that would seem completely unbelievable if we only had fossils of them.

But not nearly as strange as some of their ancient relatives.

Platybelodon is probably the most famously weird member of the proboscideans (the group that contains both modern elephants and their extinct cousins), looking like some sort of deliberately outrageous speculative creature design.

Living during the mid Miocene, around 15-4 million years ago, several different species of Platybelodon ranged across Africa, Europe, Asia, and North America, with Platybelodon grangeri here known from abundant fossils in Asia.

These strange-looking proboscideans stood around 2.2m tall (7’3″) and had fairly standard elephant-like bodies, but also heads with bizarre-looking elongated lower jaws that ended in a wide flat shovel-like shape tipped by two flat tusks, leading to their nickname of “shovel-tuskers”.

It was originally interpreted as a swamp-dwelling animal using its weird jaw to scoop up soft aquatic vegetation, with a fairly short flat trunk. But more recent studies of the wear patterns on its teeth suggest it actually used them more like a scythe than a shovel, cutting through tough grasses and branches – a feeding style that would also require it to have a much more modern-elephant-like trunk, using it to hold on to plants while it was sawing through them.

Weird Heads Month #19: Sword-Snouted Whales

Cetaceans are just weird animals in general. Fully aquatic mammals best described as “fat screaming torpedoes“, with bizarre head anatomy and their nostrils pulled up to the top of their heads behind their eyes. Some of them are among the largest animals to ever exist, some of them can live to over 200 years old, and some can dive to incredible depths below the ocean surface.

And they’re all descended from tiny deer-like creatures, with their closest living relatives being hippos and other even-toed ungulates.

Some ancient cetaceans were particularly odd-looking, evolving walrus-like tusks or elongated chins – or in the case of Eurhinodelphis longirostris here, an incredibly long swordfish-like snout.

Living during the mid to late Miocene, about 14-7 million years ago, Eurhinodelphis ranged across the Mediterranean and the North Atlantic, with fossil remains known from Western Europe, Turkey, and the East Coast of the United States. It was a fairly small dolphin-like cetacean about 2m long (6’6″), and was part of a lineage of early toothed whales called eurhinodelphinids.

Its upper jaw was around five times longer than the rest of its skull, and toothless past the point where the lower jaw ended. Much like the modern billfish it resembled, it probably used its snout to slash at fast-moving fish, stunning them and making them easier to catch.

Weird Heads Month #18: Boneheaded Dinosaurs

Pachycephalosaurs are highly recognizable dinosaurs with their thick spiky skulls, and it’s not hugely surprising that they were the evolutionary cousins of the equally weird-headed ceratopsians.

Much like their frilled relatives they had beaks at the tips of their snouts and large gut cavities for digesting plant matter, but they also had surprisingly sharp theropod-like teeth in front of their more standard herbivore teeth further back – suggesting they may also have been opportunistic omnivores, occasionally snacking on carrion or small animals similarly to modern pigs or bears.

Their striking-looking dome heads were probably used for combat, headbutting or flank-butting each other, and many fossil skulls show evidence of injuries that would have been caused by that sort of behavior.

The eponymous Pachycephalosaurus wyomingensis lived in North America right at the end of the Cretaceous, about 70-66 million years ago. It was one of the largest of its kind, reaching lengths of around 4.5m (14’9″), and was characterized by a large bony dome-head surrounded by small blunt spikes.

But it turns out that was probably only what it looked like as a fully mature adult.

Recent discoveries of juvenile Pachycephalosaurus skulls confirmed a hypothesis proposed a few years earlier: these dinosaurs changed appearance drastically as they grew up, and younger individuals had been mistaken for separate species. They started off with domeless flat heads, bristling with long spikes (a form previously named Dracorex hogwartsia) then as they matured their domes began to grow (previously Stygimoloch spinifer) and by full maturity they had big domes with the spikes shrunk down to smaller stubbier knobs (the classic Pachycephalosaurus look).

This particular reconstruction depicts a Stygimoloch-like subadult individual, not quite fully mature and still sporting some longer spikes.

Weird Heads Month #17: Trapjaw Ants From Hell

Ants first evolved sometime in the Late Jurassic or Early Cretaceous, but only really began to diversify about 100 million years ago in the Late Cretaceous after the rise of flowering plants.

One of their evolutionary experiments around that time was a group called the haidomyrmecinae – also known as the “hell ants”.

Known from Asia, Europe, and North America, hell ants had bizarre-looking heads, possessing huge upward-curving scythe-shaped mandibles and a horn-like projection between their antennae.

They were fast-moving arboreal predators that would have fed mainly on other invertebrates such as soft-bodied beetle larvae, and unlike most modern ants their workers were probably solitary hunters. They were capable of gaping their mandibles by almost 180°, and when they got close enough to their targets the long sensory hairs around their faces triggered their jaws to snap vertically upwards, impaling their prey against their horn in a unique trap-jaw mechanism.

Some species also reinforced the exoskeleton of their horns with metal particles, strengthening them against impacts from both struggling prey and their own powerful jaws.

Ceratomyrmex ellenbergeri was one of the oddest-looking of all known hell ant species. Known from a few specimens preserved in amber, with adult workers up to 6mm long (~0.25″), it lived during the Late Cretaceous of Myanmar about 100-94 million years ago.

It had an especially pronounced horn and very long mandibles, which may have been adaptations for tackling significantly larger prey items than other hell ants.

And due to this being a species known from Burmese amber, sadly we also have to address the controversy surrounding these sorts of specimens. This amber is currently mined in incredibly dangerous conditions, often using child labor, with sales of both jewellery and paleontological specimens directly funding the ongoing violent conflict in the region.

It’s the fossil equivalent of blood diamonds, and a huge ethical dilemma for the paleontology community.

Weird Heads Month #16: Big Honking Snoots

The dinoceratans featured here a few days ago were some of the first large mammalian herbivores to evolve in the Cenozoic, but during the Eocene they were joined by another group: the even bigger brontotheres.

Part of the odd-toed ungulate lineage, brontotheres convergently resembled rhinos but were actually much more closely related to horses. And much like the dinoceratans they also had some unusual heads, with some species evolving concave foreheads and sexually dimorphic ossicone-like pairs of blunt horns on their noses.

But others went really weird.

Embolotherium andrewsi lived in Mongolia during the late Eocene, around 37-34 million years ago. Standing around 2.5m tall at the shoulder (8’2″), it was one of the largest brontotheres and also one of the oddest-looking.

It had a large bony “battering ram” at the front of its snout, formed from modified nasal bones – and while some reconstructions tend to shrinkwrap this structure as a horn, the fact that the nasal cavity appears to have extended all the way to its tip suggests that it was actually supporting a huge bulbous nose.

Since Embolotherium also doesn’t seem to have been sexually dimorphic like other brontotheres, its enormous ridiculous-looking snoot may instead have been a resonating chamber used for sound production and communication.

Weird Heads Month #15: Hammerhead Reptiles

Atopodentatus unicus lived in Southwest China during the early-to-mid Triassic, around 247-240 million years ago. About 3m long (9’10”), it was a marine reptile – probably part of an early branch of the sauropterygians – with an elongated streamlined body and paddle-like limbs.

When it was originally described in 2014 it seemed to have a head unlike anything seen before. The skull of the only known fossil specimen was incomplete and badly crushed, but it was reconstructed as having a downward-hooking upper jaw with a vertical split in the middle forming a zipper-like row of teeth.

An illustration of the old interpretation of Atopodentatus. It has a bizarre vertical split in the front of its snout full of needle-like teeth resembling a zipper.
The original version of Atopodentatus

But then just two years later some more complete skulls were discovered and revealed something completely different: the projections on Atopodentatus‘ snout actually stuck out to each side in a wide flat “hammerhead” shape on both its upper and lower jaws.

Not quite as bizarre as before, but still a Triassic weirdo!

It also seems to have been a rare example of a herbivorous Mesozoic marine reptile, probably rooting around on the seafloor with its shovel-like mouth, using its chisel-shaped front teeth to scoop up mouthfuls of algae and other marine plants and then straining out the water through its closely spaced needle-like back teeth.