science illustration – Page 4

Spectember 2025 #03: Dicyny World

Sophie Shepherd requested: “Predator and prey from an alternate Mesozoic where archosaurs and cynodonts never displace dicynodonts as the dominant terrestrial vertebrates. Lystrosaurus-descendants conquer the world!”

Well into an alternate Jurassic, long after the Great Dying, the descendants of the opportunistic survivor Lystrosaurus are thriving. Cynodonts and rauisuchian-like archosaurs still saw decent success as large predators during this world’s Triassic, but the extinction at the end of that period wiped most of them out, and now the lystrarch dicynodonts are the dominant land vertebrates.

A digital sketch of a speculative descendant of the protomammal Lystrosaurus. It's a hairy deer-like animal with a turtle-like beak, lumpy bosses on the top of its snout, short pointed "devil horns" above its eyes, and antler-like horns growing out from its cheekbones.

The most common herbivorous lystrarchs are big bulky Lisowicia-like forms, but in open savanna-like habitats smaller fast-running deer-like forms like Diablocervops shepherdi are starting to diversify.

Standing around 1m tall at the shoulder (~3’3″), Diablocervops has particularly elaborate facial ornamentation, with bosses on its snout, pointed brow horns, and long pronged horns flaring out from its cheekbones. These structures only develop towards maturity but aren’t sexually dimorphic, used for visual displays and in head-pushing contests to establish dominance hierarchies within herds.

It lacks teeth, and grinds mouthfuls of food against its tough palate before swallowing, also using a gizzard-like stomach chamber with gastroliths to further process tough vegetation.

A digital sketch of a speculative carnivorous descendant of the protomammal Lystrosaurus. It resembles a Komodo dragon with a hooked eagle-like beak, a pair of short tusks, thick bony ridges on its brows and cheeks, and thick lumpy leathery skin covering its body.

Meanwhile, following the loss of the former archosaur and cynodont predators, Dakorhynchus gorgoides is part of a new lineage of predatory lystrarchs descended from small pig-like omnivorous burrowers that had remained quite similar to their Lystrosaurus ancestors for much of the Triassic.

Around 4m long (~13′), it’s built rather like a large monitor lizard or crocodilian, with a low-slung semi-erect posture and hairless pebbly leathery skin. It’s an ambush predator that lunges with short bursts of speed, grappling with its well-muscled forelimbs and using slashing strikes from its hooked beak and short pointed tusks to subdue prey.

Spectember 2025 #02: A Little Shell-Fish

Another anonymous request asked for a “terrestrial placoderm“:

A digital sketch of a speculative terrestrial placoderm fish. It has only two limbs, with a bony carapace covering its head, body, and legs. Its boxy head has large frog-like eyes, its back is high-domed like tortoise's shell, and a scaly tail protrudes behind it for balance. Its legs are made up of two segments each, somewhat resembling the hind legs of a grasshopper, ending in blocky triangular "feet".

Keluphichthys pezoporus is a descendant of Bothriolepis-like Devonian placoderms. Inhabiting shallow freshwater environments, they often used their rigid jointed fins to scramble short distances over land to reach new isolated ephemeral pools, and they developed convergently lung-like structures that could exchange gases directly from air, allowing them to survive in poorly-oxygenated waters and make even longer terrestrial journeys.

While the end-Devonian extinction devastated all other placoderms, this odd lineage survived into the Carboniferous, eventually raising themselves up to walk fully on their two limbs using a heavily scaled tail for balance.

Due to the relative weight of its bony carapace Keluphichthys is a fairly small animal, standing about 10cm tall (~4″). Its high domed body shape allows it to right itself when overturned, and resists the bite forces of larger predators such as the early tetrapods it lives alongside.

Its jaws are protrusible, with bony blades fused into a serrated “beak” used to snatch up invertebrate prey.

A digital sketch of a speculative terrestrial placoderm fish's head, detailing its protrusible jaws made up of serrated beak-like bony blades.

It’s still reliant on wet environments, needing to stay moist and returning to pools of water in order to reproduce. Juveniles start out aquatic and gradually transition to terrestrial habits as they mature.

Spectember 2025 #01: The Creeping Whale

Another September, another #Spectember, and maybe, just maybe, one day I’ll finally finish getting through the speculative evolution concept submissions you all gave me several years ago.

(Also, a reminder: I’m not taking further requests!)

As with the previous couple of years I’m not setting a definite posting schedule; it’ll just be whatever I can manage to get done during the month.

So, let’s get started with an anonymous submission that requested a “secondarily terrestrial cetacean similar to Cartorhynchus and Sclerocormus”:

A digital sketch of a speculative secondarily-amphibious early whale. It has a short blunt snout with nostrils in front of its large eyes, a humped back, large flippers, a vestigial-looking dorsal fin, and a fluked tail.

Repocetus aigialonatus is a 2.5m long (~8′) Late Oligocene cetacean closely related to mammalodontids — early baleen whales with toothy jaws — living around the mostly-submerged continent of Te Riu-a-Māui Zealandia.

Its ancestors hunted in shallow waters around the low-lying islands, occasionally semi-beaching themselves in pursuit of penguins or to escape from larger marine predators. This eventually led to Repocetus regaining some degree of terrestrial locomotion ability, able to galumph somewhat like modern seals using a combination of undulating its body and pushing off using flippers with powerful shoulder muscles.

It’s slow and awkward, but there are no terrestrial predators to threaten it — and so it’s also reverted to giving birth on the safety of the shore.

Like its mammalodontid relatives it has large eyes and a fairly short snout. It occupies a similar ecological niche to the modern leopard seal, using large sharp teeth to grip and tear at large prey. While it mainly feeds on large fish, it will also use its amphibious abilities to charge onto shore to raid beach-nesting bird colonies or to take advantage of other beached cetaceans.

Akidostropheus

Akidostropheus oligos was a small tanystropheid archosauromorph reptile that lived during the late Triassic, about 223-218 million years ago, in what is now Arizona, USA.

Only a few tiny isolated vertebrae have been discovered, so its full size and appearance isn’t known – making any reconstruction rather speculative – but it was probably around 30cm long (~12″). Like other tanystropheids it would have been a long-necked lizard-like animal, and may have had a similar build to the closely-related Tanytrachelos.

But despite the scarcity of material the few known vertebrae are unique among archosauromorphs, bearing elongated spikes with a surface texture that suggests they were covered with keratinous sheaths. The spikes were conical, sharp, and hooked on the neck and upper back, but became more flattened, straighter, and blade-like on the lower back and tail.

These structures were probably defensive in nature, especially considering that there’s direct fossil evidence for predators targeting the long necks of tanystropheids and decaptiating them.

Akidostropheus lived in a tropical floodplain environment around a meandering river system, but without more and better fossils it’s impossible to tell what its ecology was. Tanystropheids were a strange and diverse bunch, with both terrestrial and aquatic lifestyles, bipedal runners, and possibly even bizarre leg-gliders, so this spiky little Triassic weirdo could have been doing almost anything.

Gigantspinosaurus

Gigantspinosaurus sichuanensis was an early stegosaur that lived during the mid-Jurassic, about 166 million years ago, in what is now southwestern China.

Around 4.5m long (~14’9″), it had relatively small back plates and a pair of enormous shoulder spikes. It’s unclear exactly how the shoulder spines were positioned in life, but based on how they were found articulated in a fairly complete skeleton they seem to have swept sideways and backwards, protecting Gigantspinosaurus’ flanks.

Skin impressions show a mosaic of polygonal scales with scattered “rosettes” made up of larger scales surrounded by a ring of smaller scales, with a rough ridged surface texture that may have reduced light glare – suggesting an overall more matte appearance rather than glossy.

The thigh bones of one specimen are pathological, showing evidence that these dinosaurs sometimes suffered from bone tumors.

Tulaneia

Tulaneia amabilia was an enigmatic Ediacaran animal that lived in what is now Nevada, USA just before the start of the Cambrian Period, about 540 million years ago.

Up to around 10cm across (~4″), its body was made up of a fan-shaped frill of airbed-like tubes, with tips that separated from each other and tapered to blunt points. Much like its close relative Ernietta it would have lived with its base buried in the seafloor sediment, and it was probably a suspension feeder catching organic particles in water currents.

One Tulaneia fossil specimen shows birfurcating tips, but it’s unclear whether this was a common feature of this species or a developmental anomaly in this particular individual.

Notiomastodon

Notiomastodon platensis was a gomphothere – a relative of modern elephants – that lived across much of what is now South America from the mid-Pleistocene to the early Holocene, between about 800,000 and 10,000 years ago.

Similar in size to an Asian elephant, it stood around 2.5m tall at the shoulder (~8’2″) with a domed head and thick tusks that varied in length and curvature between different individuals. It had a stockier build than modern elephants with thicker and slightly shorter limbs, and fossilized footprints suggest it had five nails on its front feet and at least three on the hind feet.

Isotope analysis and wear analysis of Notiomastodon’s teeth suggest it was a generalist browsing herbivore, with different populations adapting their dietary habits to local conditions. As one of the largest South American herbivores of its time it was probably an important seed disperser for plants such as bamboo and palms – and some of the plants that once depended on it may now be “evolutionary anachronisms“.

Mirasaura

Back in 1939, fossil collector Louis Grauvogel discovered a couple of reptile fossils in Middle Triassic-aged deposits (~247 million years old) in eastern France. A large preserved structure was noted above the animal’s back, but for many years it was interpreted as an unrelated fish fin, insect wing, or plant frond.

It was only when the State Museum of Natural History Stuttgart acquired the specimens in 2019 that they were recognized as representing something very special: a long-sought-after relative of the bizarre and enigmatic Longisquama!

Mirasaura grauvogeli grew to around 30cm long (~1′) and was, if anything, even stranger than its relative. It had humped shoulders, grasping limbs, and a bird-like head with large forward-facing eyes and a long pointed snout that was toothless at the front, probably used to probe for small invertebrates in cracks and crevices.

But most strikingly it had up to 20 tall structures overlapping along its back to form a sail-like crest. Although they were superficially feather-like in shape with preserved melanosomes that resemble those of birds, structurally they weren’t feathers at all – but they also weren’t modified scales. Instead these appear to have been an entirely novel type of skin appendage, made up of continuous sheets with a midline shaft and a corrugated texture.

The crest was probably used for visual display, and 80 additional fossils of isolated crest structures suggest they were regularly shed and regrown.

Along with Longisquama, Mirasaura appears to have been an early member of the drepanosaur lineage – a group of wonderfully weird tamandua-like reptiles whose evolutionary relationships are still disputed, with different studies currently recovering them as either a unique early offshoot of the diapsids or as archosauromorphs.

(Interestingly, a specimen of Drepanosaurus reportedly preserves some soft tissue on its back that may also be one of these strange new crest structures. Drepanosaurs just keep on getting weirder and weirder and I love them.)

Protemnodon

Protemnodon viator was a large macropod that lived in what is now western and southern Australia during the late Pleistocene, around 50,000 years ago.

Although it was built more like a giant wallaby, ancient mitochondrial DNA has shown that its closest living relatives are actually modern grey kangaroos.

Estimated to have weighed about 170kg (~375lbs) – twice as much as the largest modern red kangaroos – it would have stood up to 2.4m tall (~8′) on its hind legs. But unlike its living relatives Protemnodon’s limb proportions indicate it wasn’t a very efficient bipedal hopper, instead probably mostly moving with a bounding or galloping quadrupedal gait.

Its forelimb anatomy also suggests it was a good digger, and strongly curved claws on its hind feet may have helped provide grip on uneven ground.

Sinopterus

Sinopterus dongi was a tapejarid pterosaur that lived during the early Cretaceous, around 120 million years ago, in a temperate forest in what is now northeastern China.

It’s known from multiple specimens representing different life stages, with the largest fully mature individuals reaching a wingspan of about 1.9m (6’2″). Like other tapejarids it had a toothless parrot-like beak, and a low bony crest on its skull may have supported a larger soft-tissue structure.

A specimen with gut contents has been found showing evidence of plant matter and gastroliths, suggesting that Sinopterus was primarily herbivorous.