paleoart – Page 37 – Nix Illustration

Ensidelphis

Last week’s weird-snouted Furcacetus wasn’t the only recently-discovered ancient platanistoid dolphin that deserves some attention.

Ensidelphis riveroi was described in the same paper, and also lived in the coastal waters around Peru during the early Miocene, about 19 million years ago. It was a little less closely related to its modern river-dwelling cousins than Furcacetus, and was slightly larger, estimated to have measured about 3m long (9’10”).

But what made it weird was its incredibly long snout, lined with around 256 tiny sharp teeth, which also curved markedly to the right side along its 55cm (1’10”) length.

With only one known skull of Ensidelphis it’s impossible to tell if this was a natural condition for the species or if it was some sort of anomalous individual. It doesn’t seem to be a deformation of the fossil, at least.

Similar unusual right-side bending has been seen in the skulls of a few individuals of modern South Asian river dolphins, franciscanas, and Amazon river dolphins, possibly caused by injuries at a young age being exaggerated as the animals grew. However, many other platanistoid dolphins (especially squalodelphinids) are known to have naturally had similar bends in their snouts – but always to the opposite side, curving to the left instead of the right.

But naturally bent or not, what might Ensidelphis have been doing with that incredibly lengthy snoot?

Its long slender jaws would have had a fairly weak bite, so it probably wasn’t able to catch large prey, and it had a very flexible neck. Possibly it swam along near the seafloor using its snout to probe and sweep around in the sediment for buried small prey.

Modern South Asian river dolphins swim along on their sides while doing this – almost always on their right sides, interestingly enough – and if Ensidelphis did the same sort of thing then a snout bent in that direction might have been an advantage.

Furcacetus

The two living subspecies of the South Asian river dolphin are the last surviving members of a lineage known as the Platanistoidea, an early evolutionary branch of the toothed whales. This group was once much more diverse and widespread than their modern representatives, found in oceanic habitats around the world from the Oligocene to the mid-Miocene.

Many of them had forward-pointing protruding teeth at the tips of their snouts, resembling those of some plesiosaurs or pterosaurs, suggesting they were a convergent adaptation used for snagging hold of slippery soft-bodied aquatic prey.

Furcacetus flexirostrum is one the newest additions to this group, named and described in late March 2020. It lived in Pacific coastal waters around Peru during the early Miocene, about 19-18 million years ago, and was about the same size as modern South Asian river dolphins at around 2.3m long (7’7″).

And it had a uniquely-shaped snout for a cetacean, curving upwards for most of its length but then turning downwards right at the tip, which along with large forward-pointing teeth gave its jaws a vaguely crocodilian appearance.

A closeup view of the jaws of Furcacetus.

Much like slender-snouted crocodilians and spinosaurids, this arrangement would have allowed Furcacetus to make quick bites at small-fast-moving prey like fish and crustaceans.

Eons Roundup 6

Time for some more recent commissions from PBS Eons!

An illustration of an extinct carnivorous mammal. It resembles a dog-hyena, with chunky jaws and a long thin tail. — Megistotherium osteothastes

The hyainailourids Megistotherium osteothastes and Hyainailouros napakensis, from “When Giant Hypercarnivores Prowled Africa”
https://www.youtube.com/watch?v=rK2nvNxAuk4

An illustration of a bear-dog, an extinct carnivorous mammal. It resembles a dog or fox with a long thin tail. — Daphoenus demilo

An illustration of a bear-dog, an extinct carnivorous mammal. It resembles a bear, with a chunky body and a long thin tail. — Daphoenus demilo

The bear-dogs Daphoenus demilo and Amphicyon giganteus, from “The Forgotten Story of the Beardogs”
https://www.youtube.com/watch?v=xbmLqrnxH2w

An illustration of an extinct relative of giant pandas, sitting and eating a bamboo branch. It has more brownish fur than modern pandas, with less defined white markings. — Ailuropoda microta

The early panda Ailuropoda microta, from “The Fuzzy Origins of the Giant Panda”
https://www.youtube.com/watch?v=G2DbShys9ww

Weird Heads Month #30: Lumpy-Faced Synapsids

Among the synapsids (“proto-mammals”), head ornamentation evolved multiple times in the therapsids, from basal members of the group like Tetraceratops, burnetiamorphs, and dinocephalians to later lineages like dicynodonts and gorgonopsids.

But these sorts of structures don’t seem to have really ever developed in one of the lineages most closely related to the ancestors of modern mammals, a group known as therocephalians.

…With the exception of Choerosaurus dejageri.

Living in South Africa during the late Permian, around 259-254 million years ago, this small synapsid was only about 35cm long (1’2″) but sported some large bulging bony bosses on the sides of both its snout and lower jaw.

The bosses would have been covered by tough skin in life, similar to modern giraffid ossicones.

A study of Choerosaurus‘ skull found that its head was rather delicately built, and the bosses were relatively fragile and lacked the sort of reinforcement needed to resist impacts, suggesting that these structures weren’t used as weapons for fighting each other but were probably more for display – so they may even have been brightly colored.

The upper jaw bosses were also well-supplied with nerves and blood vessels, and would have been quite sensitive to touch.

Weird Heads Month #29: Giant Saw-Toothed Birds

The pelagornithids, or “pseudotooth birds”, were a group of large seabirds that were found around the world for almost the entire Cenozoic, existing for at least 60 million years and only going completely extinct just 2.5 million years ago.

Their evolutionary relationships are uncertain and in the past they’ve been considered as relatives of pelicaniformes, albatrosses and petrels, or storks, but more recently they’ve been proposed to have been closer related to ducks and geese instead.

Whatever they were, they were some of the largest birds to ever fly, and many of the “smaller” species still had wingspans comparable to the largest modern flying birds.

But their most notable feature was their beaks. Although at first glance they look like they were lined with pointy teeth, these structures were actually outgrowths of their jaw bones covered with keratinous beak tissue. While these bony spikes would have been useful for holding onto slippery aquatic animals like fish and squid, they were actually hollow and relatively fragile so pelagornithids must have mainly caught smaller prey that couldn’t thrash around hard enough to break anything.

The serrations also only developed towards full maturity, and the “toothless” juveniles may have had a completely different ecology to adults.

Pelagornis chilensis here was one of the larger species of pelagornithid, with a wingspan of 5-6m (16’4″-19’8″), known from the western and northern coasts of South America during the late Miocene about 11-5 million years ago.

Like other pelagornithids it was highly adapted for albatross-like dynamic soaring, with long narrow wings that allowed it to travel huge distances while expending very little energy – but with its proportionally short legs it would have been clumsy on the ground and probably spent the vast majority of its life on the wing, only returning to land to breed.

Weird Heads Month #28: Pig-Nosed Tanks

There’s already been quite a few Triassic weirdos in this series, so it’s probably not much of a surprise that we’ve got one more before the end of the month.

Desmatosuchus spurensis here was part of a group called aetosaurs, a lineage of heavily-armored herbivorous archosaurs which convergently resembled the later ankylosaurs but were more closely related to modern crocodilians.

Living in the Southwestern and South Central United States during the late Triassic, about 221-210 million years ago, Desmatosuchus measured around 4.5m long (14’9″) and was covered in thick interlocking bony osteoderms that protected its back, sides, belly, and tail, with longer spines over its neck and shoulders.

It had a triangular skull with a few blunt teeth at the back of its jaws and a toothless snout at the front. Its pointed lower jaw probably had a keratinous beak, while its upper jaw had an odd upturned flared tip. What exactly was going on with that snoot is uncertain, but it may have anchored a shovel-shaped upper keratinous beak – or, since there was a little bit of flexibility between its snout bones, possibly even a pig-like nose!

It probably mostly ate soft vegetation, using its shovel-like snout to dig up roots and tubers, although similarities with the skulls of modern armadillos suggest it may also have fed on insect grubs.

Weird Heads Month #27: The Weirdest Wildebeest

Earlier in this series we saw some ruminants with bizarre-looking headgear, but there was another species in that group that evolved a completely different type of strange head.

Rusingoryx atopocranion was a close relative of modern wildebeest that lived during the late Pleistocene, around 100,000 to 50,000 years ago. Its fossil remains are known from the Kenyan part of Lake Victoria, on Rusinga Island – an area which wasn’t actually an island at the time due to lower lake levels, and was instead part of a hot dry grassland environment.

Standing about 1.2m at the shoulder (~4′), it had an oddly-shaped skull with a pointed snout and a highly domed forehead. But this wasn’t the thick bony dome of a headbutting animal – this structure was narrow and fairly fragile, and had looping nasal passages running through it.

Instead it was something never before seen in any mammal: a bony nasal crest convergently similar to those of hadrosaurid dinosaurs.

Juveniles had less developed crests, developing them as they matured, and one skull that may represent an adult female also has a smaller crest, suggesting that this feature was sexually dimorphic.

Based on just the anatomy of the nasal passages Rusingoryx may have honked at a frequency similar to a vuvuzela, but the added length of its vocal tract could have lowered this pitch even further, closer to infrasound ranges – so more like a tuba! Such low frequencies can travel very long distances and are also below the hearing range of many carnivores, and would have effectively allowed Rusingoryx to shout at each other in “stealth mode”.

Weird Heads Month #26: Curious Cambrian Creatures

During the Cambrian explosion, a time full of incredibly weird-looking evolutionary experiments, Opabinia regalis was one of the weirdest of all – so ridiculous, in fact, that when its anatomy was first revealed at a presentation the audience laughed.

Known from the mid-Cambrian Burgess Shale fossil deposits in Canada, this bizarre creature lived around 508 million years ago and had a body measuring just 4-7cm long (~1.5-2.75″).

It had five stalked eyes on its head, and a long flexible proboscis that resembled a vacuum cleaner hose ending in a pincer-like grasping structure. Its mouth was located on the bottom of its head, behind the base of its proboscis, and the opening pointed backwards forming a U-bend in its digestive tract.

The rest of its segmented body had overlapping swimming lobes and a tail fan, and small triangular structures that may have been legs on its underside.

It was probably a bottom-feeding predator or a detritvore, swimming along above the seafloor using its proboscis to snatch up small soft prey or organic material and passing it up to its mouth.

It also seems to have been a fairly rare member of the Burgess Shale ecosystem, with less than 50 specimens known from the thousands of fossils found there.

For a while Opabinia was thought to represent a completely new phylum, but after further discoveries of similar animals like Anomalocaris it’s now considered to be a “stem-arthropod”, a close evolutionary cousin to modern insects, arachnids, myriapods, and crustaceans. Its exact relationships with other stem-arthropods are still being debated, however, and some studies suggest its closest living relatives may actually be tardigrades.

Weird Heads Month #25: The Case of the Missing Trunk

The rhino-like toxodontids from earlier in this series weren’t the only weird-headed South American ungulates. Another group known as the litopterns evolved in a different direction, becoming long-legged fast-moving animals convergently filling the same sort of ecological niches as modern horses, deer, bovids, camelids, and giraffids.

Macrauchenia patachonica was one of the strangest members of this lineage, living from the Late Miocene to the end of the Pleistocene, between about 7 million years ago and just 12,000 years ago.

It stood around 1.8m at the shoulder (5’11”) and resembled a large camel or llama with thee-toed hoofed feet, but its head was… confusing.

Its skull had a bizarre combination of features, with a shape closer to a sauropod dinosaur than a mammal, a cartoonish-looking set of teeth, and its nostrils set up high above its eyes, more like a cetacean blowhole than a terrestrial herbivore.

Due to its retracted nostrils it’s commonly been restored with an elephant-like or tapir-like trunk. And while a trunk gives Marauchenia a wonderfully weird and memorable appearance, there’s just one problem with that interpretation.

There’s no evidence for it.

Aside from its nostrils being far back on its head, it didn’t have any other features associated with anchoring the complex musculature of a trunk. In fact, a recent study found that its skull characteristics were much closer to those of moose than tapirs!

It seems more likely that it had a moose-like bulbous fleshy nose – possibly giving it an enhanced sense of smell or functioning as a resonating chamber – perhaps with slightly retracted external nostrils like a giraffe or sauropod to prevent it from being stabbed in the nose when feeding on spiky vegetation.

Whatever it was doing with its weird schnoz, it was clearly a highly successful species, since it was found across most of South America in a wide range of habitats.

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.