mammal – Page 7 – Nix Illustration

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 #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 #13: Many-Horned Mammals

The dinoceratans were a lineage of hoofed herbivorous mammals whose evolutionary affinities are a little uncertain, but may have been related to the South American meridiungulates. Found in Asia and North America from the late Paleocene to the late Eocene, they had bulky rhino-like bodies and were some of the largest terrestrial animals of their time.

Eobasileus cornutus was one of the biggest of them all, measuring around 2.1m tall at the shoulder (~7′) and living in the Western United States during the early Eocene, about 46-40 million years ago.

And it had a very odd-looking head, with six blunt ossicone-like horns, large sabre-like fangs, bony flanges on its lower jaw, a concave forehead, and a proportionally tiny brain for its body size. The horns and fangs were sexually dimorphic, much smaller in females, suggesting they were mainly used for display or combat between males.

Weird Heads Month #09: Butterfly Faces

The nose-forks and head-crests we saw last time weren’t the only unusual headgear in ancient ruminants.

The giraffoids are represented today by just pronghorns, giraffes, and okapi, but in the past they were much more diverse, modifying their prongs and ossicones into multiple sets of horns, or into deer-like and moose-like antler shapes.

And Prolibytherium was probably the most striking of the lot.

Two different species have been identified, with Prolibytherium magnieri here living in North Africa during the early-to-mid Miocene, about 17-16 million years ago. Its exact evolutionary relationships are uncertain but it was probably part of a group called climacoceratids, deer-like giraffoids which often had thorny branching ossicones that resembled antlers.

It stood around 1.2m tall at the shoulder (~4′), and exhibited dramatic sexual dimorphism – females had slender forked horn-like ossicones, while those of the males flared out into large wide flat shapes that resembled butterfly wings.

Heavy reinforcement in the bones of the back of the males’ skulls helped to support all the extra weight of those huge ossicones, and if they actually used the structures to fight with each other then this may have also provided some protection or shock absorption.

Weird Heads Month #08: Nose-Forks and Handlebar Heads

Modern ruminants are the only living mammals with bony headgear, with four different lineages each sporting a slightly different type: deer antlers, bovid horns, giraffid ossicones, and the prongs of pronghorns.

We still don’t actually know much about the evolutionary origins of ruminant headgear, although a recent genetic study suggests they’re all derived from a single common ancestral structure (and that deer antlers started off as controlled bone cancer).

And some extinct species were even stranger.

The protoceratids were an early group of North American ruminants whose relationships are uncertain, but may have been related to modern chevrotains. They were convergently deer-like in appearance, with teeth adapted for grazing on tough grasses – and along with having a pair of horns in the usual position on their heads, males also sported an additional pair of ossicone-like growths on their noses.

Synthetoceras tricornatus lived during the Late Miocene, around 10-5 million years ago, and was one of the largest protoceratids, standing about 1.1m tall at the shoulder (3’7″). Its two nose-horns were partially fused into a single long structure with a forked tip, which may have been used for sparring in a similar manner to the antlers of modern deer.

A colored line drawing of an extinct deer-like animal. It has a pair of horns on its head, along with a long horn on its nose that has a two-pronged forked tip. — Synthetoceras tricornatus

Meanwhile on a different branch of the ruminant family tree, closer related to deer and giraffes, a group known as the palaeomerycids independently developed a similar sort of extra head appendage – but at the opposite end of their skulls.

These ruminants were a little more heavily built than the protoceratids, and specialized in feeding on soft vegetation in humid forest environments. They were a highly successful group, existing for almost 30 million years, ranging across Eurasia, Africa, and North America, and even ventured into South America during the early phases of the Great American Interchange.

Males had two giraffe-like ossicones above their eyes, along with a third crest-like one at the very back of their heads. In some species this formed a single central “horn” shape, while in others it forked out to each side. They also often had long saber-like canine teeth similar to modern water deer and musk deer, which were probably used for fighting while their elaborate headgear was purely for visual display.

Xenokeryx amidalae lived in Spain during the mid Miocene, about 16 million years ago. It stood around 0.8-1m tall at the shoulder (2’7″-3’3″) and had a unique T-shaped “handlebar” crest which ended up inspiring its genus name – a reference to the similar shape of one of Queen Amidala’s headpieces in Star Wars, which was itself based on Mongolian imperial fashion.

A colored line drawing of an extinct deer-like animal. It has fang-like tusks protruding from the sides of its mouth, a pair of giraffe-like ossicones above its eyes, and a T-shaped handlebar-like crast on the back of its head. — Xenokeryx amidalae

Weird Heads Month #04: South American Unicorns

South America was an isolated “island continent” for a large chunk of the Cenozoic, and during that time it was home to a unique mix of species evolving completely separately to the rest of the world.

One group found there were the meridiungulates, a lineage of hoofed mammals related to modern horses, rhinos, and tapirs. Many of them convergently evolved to resemble other types of mammals, and the large rhino-like toxodontids were some of the most common and successful.

And, like rhinos, some of them may even have had horns.

Hoffstetterius imperator lived in Bolivia during the late Miocene, about 11-5 million years ago. Standing around 1.6m tall at the shoulder (5’3″), it had a particularly oddly-shaped skull, with a deep downward-flaring lower jaw and a large bulging bony “shield” on its forehead that resembles the attachment points for horns on rhino skulls.

Keratinous structures like that only fossilize very rarely, so the actual size and shape of whatever attached there is unknown – the pointed horn shown here is one possibility – but we honestly don’t know what was going on with these guys’ heads.

Puijila

We have a fairly good picture of the evolutionary origins of most groups of aquatic mammals – except for the pinnipeds. The fossil record of early seals is still rather sparse, and for a long time the earliest known species was Enaliarctos, an animal that was already very seal-like and didn’t help much in figuring out whether seals’ closest living relatives are bears or musteloids.

But then Puijila darwini was found in the late 2000s, a transitional form with a near-complete skeleton, filling in a gap in our understanding so conveniently it almost seems too good to be true.

This is the equivalent of Archaeopteryx for seals.

Discovered in Nunavut, Canada, Puijila dates to the early Miocene, about 23-20 million years ago. It was a small freshwater otter-like animal, about 1m long (3’3″), with a long tail and webbed feet adapted for paddling with all four of its limbs.

It lived at around the same time as the more specialized Enaliarctos, so it wasn’t a direct ancestor of modern seals, instead being part of an early offshoot lineage that retained more basal characteristics – but it does gives us a clue as to what the earliest pinnipeds looked like. Along with genetic studies it also helped to clarify that seals’ closest relatives are indeed the musteloids, although they’re estimated to have last shared a common ancestor around 45 million years ago so there’s still a lot of time unaccounted for in the proto-seal fossil record.

Several other fossil species that were previously thought to be musteloids have now also been recognized as close relatives of Puijila, and it seems that they were a fairly widespread group basically filling the ecological niche of otters at a time before true otters existed.

Most surprising and frustrating of all, however, is that some of these other otter-seals actually survived all the way into the Pleistocene, only going completely extinct sometime in the last 2 million years.

We barely missed having them still alive today!

Eons Roundup 5

Some more recent commission work for PBS Eons!

The lemurs Archaeolemur and Pachylemur, from “When Giant Lemurs Ruled Madagascar”
https://www.youtube.com/watch?v=1hTJh8W0khU

The meridiungulates Notiolofos and Antarctodon, from “When Antarctica Was Green”
https://www.youtube.com/watch?v=cC4WiBCoVeo

The Near Eastern wildcat Felis silvestris lybica, from “How We Domesticated Cats (Twice)”
https://www.youtube.com/watch?v=CYPJzQppANo

Maiabalaena

The earliest baleen whales didn’t actually have any baleen plates in their mouths, and the evolutionary origin of these unique filter-feeding structures is still poorly understood.

It was thought to have been a fairly simple linear process from toothed ancestors to a mix of teeth and baleen and then to fully toothless with just baleen, but more recent discoveries have begun to cast doubt on that idea. The teeth of ancestral baleen whales weren’t suited to filter-feeding at all, instead still being adapted for predatory piercing and chewing – actions which would have been constantly interfering with and damaging any proto-baleen forming alongside them, and making it seem much more unlikely that there would have ever been a transitional form that had both teeth and baleen at the same time.

But then how did baleen whales get their baleen?

Maiabalaena nesbittae here provides a possible solution. Discovered in Oregon, USA, this early baleen whale dates to the early Oligocene, around 33 million years ago, and compared to most of its modern relatives it was comparatively tiny, only about 4.6m long (15′).

And it had no teeth at all, but possibly also no baleen.

Baleen rarely fossilizes, so it’s unclear whether Maiabalaena actually had any or not, but the shape of its skull suggests it probably didn’t – it lacked the broad thickened upper jaw associated with supporting racks of baleen plates. It instead seems to have been adapted for suction feeding similar to modern belugas and beaked whales, using muscular cheeks and tongue to manipulate water pressure and pull small prey like fish and squid straight into its mouth.

Since it lived at a time when the Antarctic Circumpolar Current was forming and cooling the oceans, changing ecosystems and prey availability, it may represent a previously unknown stage in baleen whale evolution – a point when they’d moved towards specializing for suction feeding and lost their teeth entirely, before transitioning again over to filter-feeding with baleen in a completely separate evolutionary development a few million years later.