mammal – Nix Illustration

Samotherium

Have you ever seen half a giraffe?

Samotherium boissieri was a giraffid that lived from the mid-Miocene to early Pliocene, about 12-5 million years ago, ranging across what is now Southeastern Europe, North Africa, and the Middle East.

Standing 2.3m tall at the shoulder (~7’6″), and with a total height of around 3-3.5m (9’10”-11’6″), it had long pointed ossicones and a neck that was halfway in both length and bone anatomy between those of its modern relatives the okapi and giraffe.

(But it wasn’t a direct ancestor of modern giraffes, instead being an offshoot of the okapi lineage and most closely related to sivatheres.)

The shape of its snout and microwear on its teeth suggest that it was a seasonal mixed feeder, varying its diet between grazing and browsing at different times of year.

It would have also lived alongside another slightly larger species in the same genus, Samotherium major — but the two appear to have been ecologically partitioned, avoiding direct competition by each preferring slightly different habitats and diets. S. boissieri inhabited more open grasslands, while S. major lived in mixed woodland-grassland and was more of a grazing specialist.

Kalakocetus

Kalakocetus aurorae was an early cetacean that lived during the Eocene, about 50-48 million years ago, in what is now the northwestern region of the Indian subcontinent.

It represents the (currently) most basal known branch of the whale lineage, with teeth that are transitional between the crushing herbivorous-omnivorous molars of the closely-related raoellids and the shearing carnivorous molars of later archaeocetes.

Only known from a lower jaw and teeth, its full life appearance is unknown — but based on the body proportions of other early cetaceans it would have been a roughly cat-sized animal, around 60cm long (~2′), possibly resembling a smaller version of its better-known relative Pakicetus. It was also probably similarly semiaquatic, wading into rivers to hunt fish and other small freshwater prey.

Nanophoca

Nanophoca vitulinoides was a small earless seal that lived during the mid-Miocene (~14-12 million years ago) in what is now Belgium, which at the time was covered by the southern margin of the North Sea.

It was slightly smaller than any modern pinnipeds, no more than 1m long (3’3″), and had more mobile front and back flippers than modern earless seals — indicating it had a different swimming style than its living relatives, and that it may have been more mobile on land.

It also had a very dense skeleton, which would have made it a slower, less maneuverable swimmer. It may have fed on small prey on the seafloor in shallow coastal waters, similar to modern bearded seals.

Xenocranium

Xenocranium pileorivale lived during the late Eocene, about 35 million years ago, in what is now the Midwestern and Mountain states regions of the USA.

Despite its very mole-like appearance, this little mammal was a member of an extinct lineage known as palaeanodonts — and its closest living relatives are actually pangolins.

Around 15cm long (~6″), Xenocranium was highly adapted for a subterranean burrowing lifestyle, with an upturned shovel-shaped snout bearing a pad of thickened skin, and short powerful limbs with large digging claws. Its eyes were very reduced, functionally blind, and may not have even been visible in life. Its sense of hearing was also specialized for the sort of low-frequency sounds that carry well through the ground.

It was probably a head-lift digger, using upward motions of its snout and downward strokes with its forelimbs to excavate tunnels while foraging for worms and underground insects.

Gomphos

Gomphos elkema was an early lagomorph – closely related to the ancestors of modern rabbits, hares, and pikas – that lived during the Early Eocene, about 56-47 million years ago, in what is now Mongolia and northern China.

Around 20cm long (~8″), it had some anatomical features surprisingly similar to modern rabbits and hares, such as long feet and hindlimbs capable of hopping. But unlike its modern relatives it also had a longer tail, and more “primitive” features in its jaw and teeth that link it to lagomorphs’ shared ancestry with rodents.

Arsinoitherium

Arsinoitherium zitteli was a large herbivorous mammal living in what is now northern Africa during the late Eocene and early Oligocene, about 36-30 million years ago.

Despite looking like a double-horned rhino this resemblance was only superficial, and for most of the 20^th century it was actually the only known representative of an entire order of mammals – the embrithopods – with its wider evolutionary relationships being unknown. Since the 1970s, however, more members of this group have been discovered and embrithopods are now understood to be afrotheres, a very early offshoot of the tethythere lineage, with their closest living relatives being modern elephants and sirenians.

Arsinoitherium was by far the most abundant embrithopod, with numerous fossil remains making it one of the most completely known African fossil mammals. It stood around 1.8m tall at the shoulder (6′), similar in size to modern white rhinos, and would have been a massively-built slow-moving animal with elephant-like columnar limbs.

Its pair of enormous nose horns (and smaller brow horns) were structurally more similar to those of bovids than rhinos, with large hollow bony cores that probably bore thick keratinous sheaths that would have increased their apparent size even more. Both males and females appear to have had these horns, and muscle attachments at the back of the skull suggest Arsinoitherium could powerfully swing its head upwards – possibly wrestling with each other in combat over territories, competing for mates, or in establishing dominance hierarchies.

Flandriacetus

Flandriacetus gijseni was an early beaked whale that lived during the late Miocene, about 8 million years ago, in nearshore marine waters covering what is now the Netherlands.

Around 4m long (~13′), it had a long snout lined with small sharp teeth – unlike modern beaked whales which are mostly toothless – and much like its close relative Messapicetus it probably led a more dolphin-like lifestyle feeding on small fish near the surface.

It’s currently the youngest known example of a long-snouted stem beaked whale, a holdover from a time when these cetaceans were much more ecologically diverse than they are today.

Postschizotherium

Postschizotherium intermedium was a large hyrax that lived during the late Pliocene and early Pleistocene, about 2.5-2.2 million years ago, in what is now northern China.

About 1.5m long (~5′), it had very high-set and sideways projecting eye sockets similar to those of modern hippos, indicating it probably had a similar sort of semi-aquatic lifestyle. The shape of its skull also suggests it may have had a short tapir-like trunk.

Much like modern hippos or capybaras Postschizotherium probably spent much of its time wallowing in bodies of water, and emerging onto land to graze on grasses. Its habitat would have been humid forest and grasslands, alongside other animals such as large horses and bovines, one of the last chalicotheres, woolly rhinos, beavers, macaques, bears, big cats, early lynxes, and scimitar-toothed cats.

Megabalaena

Megabalaena sapporoensis was a member of the balaenid baleen whale lineage, related to modern right whales and bowhead whales. Living in marine waters covering what is now northern Japan during the late Miocene, about 9 million years ago, it helps to fill in a significant gap in the fossil record of this group.

Known from a partial skeleton about 12.7m long (~42′), it was much larger than earlier balaenids, but smaller than modern forms. It also had a narrower flipper shape compared to its modern relatives, a less arched jaw, and its neck vertebrae were only partially fused.

Modern right whales are slow-swimming ram feeders, but since Megabalaena was less specialized for this particular filter feeding style it’s unclear what its ecology was.

Spectember/Spectober 2025 #05: Strangels

We’re continuing into Spectober with another anonymous request, this one asking for: “Hominids that evolved with 6 limbs, 2 of which are wings. Limb placement is up to you.”

A digital sketch of a speculative six-limbed hominind, pictured in both tree-climbing and gliding poses. It has a monkey-like face with very large eyes, opposable thumbs and first toes, no tail, short fur over its body – and an extra pair of "arms" hanging just behind its shoulders that end in stubby fingerless hands and support a large gliding membrane. In the aerial pose it's shown grabbing hold of its wing-limbs to hold them in place for gliding.

Living several million years in a possible future, Anomalangelus anthropogenis is a bizarre case of a six-limbed primate.

Its additional pair of upper limbs originate from a heritable form of notomelic polymelia, similar to the Developmental Duplications condition seen in our time’s domestic cattle. It has a rather chimeric genome that appears to contain ancestry from several different hominid lineages, suggesting that this strange little creature actually descends from something that was originally genetically engineered.

It’s a tiny dwarfed species, only about 25cm long (~10″), with a highly arboreal omnivorous loris-like lifestyle, spending most of its life clambering around in trees. Although its extra limbs can’t move independently, lacking a lot of functional musculature and nerve connections, they’ve been exapted into brightly-patterned display structures and also serve as attachment for a large gliding membrane – Anomalangelus uses its forelimbs to grab hold of these “wings” while airborne, spreading them out and stabilizing them to form a composite wing.