Spectember 2023 #06: Some Big Reptiles

An anonymous request asked for a “large ankylosaur-like herbivorous notosuchian“:

A shaded sketch of a speculative ankylosaur-like animal related to modern crocodilians. It has a chunky body covered in interlocking armor plates, with a row of spikes down each side of its body and a longer pair of upward-pointing spikes on the bulbous tip of its tail. It has four squat legs, also armored, with hoof-like claws, and a short wide snout with large forward-facing nostrils.

Mitafosuchus pachysomatus is descended from Simosuchus-like notosuchians in Madagascar that survived through the K-T extinction.

Highly convergent with the now-extinct ankylosaurs, it’s a 5m long (~16’4″) squat tank-like herbivore with hoof-like claws, and a wide short snout used for grazing on low vegetation. Heavy interlocking osteoderm amor covers most of its body, protecting it against the big carnivorous crocodyliformes that also still survive in this version of Cenozoic Madagascar.

Another anon wanted to see a “giant warm blooded lizard”:

A shaded sketch of a speculative giant lizard descended from tegu. It has a small head with a slender snout, a crest on its head and a small pair of horns behind its eyes. Its neck is long and thick with a hanging fleshy dewlap, a chunky body with a sloping back, four legs in a semi-upright stance, and a long thick tail.

Atopohippus zestamenus is a descendant of invasive Argentine giant tegu lizards that became established on an island archipelago. At 2m tall (~6’6″) and around 6m long (~20′) it’s an example of island gigantism, and occupies a high-browsing-herbivore ecological niche similar to giant tortoises and prosauropods.

Its ancestors’ seasonal endothermy has become full endothermy in this species, partly due to young individuals having a very rapid growth rate and metabolism – their main defense against the predators on their island home (primarily carnivorous tegu-descendants and large birds of prey) is to simply get to a big body size as fast as they possibly can.

Spectember 2023 #05: Shiny Mammal

Someone who identified themself only as “Hanna” requested a “mammal that’s shiny and iridescent like some insects and spiders”:

A shaded sketch of a speculative semiaquatic hairy armadillo. It has a wide armor carapace with a green-blue-purple iridescent sheen, a pig-like snout, wide paddle-like hands and feet, and a short tail.

Lustrophractus hannae is a relative of modern hairy armadillos that has adapted for a semiaquatic lifestyle.

About 40cm long (~16″), its unusually shiny carapace originally evolved thanks to its ancestors’ burrowing habits. Much like golden moles and some snakes, these armadillos’ scutes and hairs developed microridges that reduced friction and repelled dirt particles, with the side effect of becoming strikingly iridescent – and, conveniently, also rather water repellent, enabling Lustrophractus’ lineage to take up aquatic omnivorous foraging habits.

The iridescence also serves a defensive function, using a bright flash of color to startle and confuse predators.

Spectember 2023 #04: Some Aukward Birds

An anonymous submitter asked for a “penguin/auk-like relative of Pelagornis“:

A shaded sketch of a speculative flightless seabird related to the extinct "pseudotooth" bird Pelagornis. It has a long slender beak with serrated tooth-like edges, a penguin-like body, flipper-like wings, large webbed feet, and a stumpy tail.

Odontopinguinus vomitus represents an unusal early branch of the pelagornithids that didn’t take up long-distance soaring, instead specializing for a pursuit diving lifestyle convergently similar to that of the contemporaneous early penguins, and the later auks and plotopterids.

About 1.2m tall (~4′), it has a more slender spear-like beak than its relatives, with forward-pointing pseudotooth serrations. Like other pelagornithids these “teeth” are fairly fragile, so it feeds primarily on soft-bodied fish and squid, pursuing them underwater with wing-propelled underwater “flight”.

Much like procellariiformes they’re also rather stinky birds, producing musky preen oil and projectile vomiting foul-smelling stomach contents at threats and rivals.

And another anon wanted to see a “big flightless marine duck”:

A shaded sketch of a speculative flightless marine duck. It has a goose-like beak with protruding comb-like structures at the sides (giving it the superficial appearance of having teeth), a long neck, a long loon-like body with vestigial folded wings, large cormorant-like webbed feet position far back, and a short tail.

Thalassonetta anambulatus is descended from the already mostly-flightless steamer ducks. At around 2m long (6’6″) it’s massive for a waterfowl, with vestigial wings and large webbed feet used to propel itself while diving.

With its rather elongated and heavy body and loon-like leg configuration it’s no longer able to walk on land – and it’s actually almost fully aquatic, only awkwardly hauling out into isolated island beaches to molt and breed.

It feeds mainly on molluscs, crustaceans, and other marine invertebrates, using the large lamellae in its bill to strain them out of soft seafloor sediments.

Spectember 2023 #03: Raptorial Isopod

Modzilla07 asked for a “eurypterid or anomalocarid-esque isopod”:

A shaded sketch of a speculative swimming predatory isopod. Its shaped similarly to an extinct sea scorpion with a streamlines segmented body that ends in a fin-like horizontal tail fan. It has short antennae, a large pair of spiny grabbing front appendages similar to an anomalocarid, large compound eyes on short thick stalks, and two pairs of its legs are modified into long paddle-like structures.

Agriopterus modzillaseptenorum is descended from scavenger-predator intertidal cirolanids. At about 10cm long (~4″) it’s a giant compared to most other isopods, but not nearly as big as some of the radiodonts and eurypterids it convergently resembles.

Adapted for a free-swimming lifestyle, its second pair of antennae have been modified into spiny raptorial appendages and its first two pairs of legs have become flat swimming paddles. It’s a voracious little predator, usually snatching small fast-moving prey from the water and raking up soft-bodied animals from the seafloor – but groups will sometimes opportunistically swarm on much larger dead, dying, or injured targets.

Spectember 2023 #02: Carnivorous Ungulates

An anonymous submitter asked for a “derived carnivorous, pack-hunting agriochoerid“:

A shaded sketch of a speculative predatory early ungulate. It has a cat-like body, long and low-slung with clawed feet and a long slender tail. Its head looks like a mix between a cat and a camel, with a fleshy cleft lip, forward-facing eyes, leaf-shaped ears, and a mouth full of sharp pointy teeth. It's depicted in two poses: on the left climbing up a tree trunk, and on the right standing and baring its fangs.

Felichoerus ochlos is fairly similar-looking to its herbivorous relatives, but this cat-sized agriochoerid comes from a lineage that initially specialized in eating fleshy fruits – and then shifted towards eating actual flesh.

With its long cat-like body, forward-facing eyes, clawed digits, and flexible limbs, it’s a capable tree climber. Groups of this animal practice cooperative hunting, with one member chasing arboreal prey down to the ground for the rest to mob.

And another anon wanted to see an “obligate carnivore bovine”:

(I see what you did there. A literal carnotaurus!)

A shaded sketch of a speculative predatory bovine. It has a muscular body with humped shoulders and cloven hoofed feet, a thick neck, and a large cow-like head. Two individuals are depicted, a standing long-horned bull and a sitting short-horned cow. The cow has a chunk missing from one ear and has her mouth open to display her sharp teeth.

The bulltcher (Carnovitulus grassator) is a sheep-sized descendant of small buffalo that gradually took up more and more omnivorous diets, eventually becoming somewhat entelodont-like opportunists. This particular species has shifted over into hypercarnivory, occupying a predator niche in an ecosystem lacking other types of carnivorous mammal.

Like their ancestors they still lack upper front teeth, and instead have modified their dental pad into an almost beak-like tough keratinized structure that their sharp lower teeth can slice and self-sharpen against.

These animals live in small matriarchal herds, with bulls usually hanging around on the edges of the group to protect from threats. Bulls have larger backwards-pointing horns, used to compete with each other for mates – but the size of these structures on their skulls results in them having slightly less powerful jaw muscles than cows.

Herds hunt cooperatively, pursuing and harassing larger prey until it can be brought down and torn apart.

Spectember 2023 #01: Kiwi Alvarezsaur

It’s #Spectember time again!

I’m still trying to work through that big pile of speculative evolution concepts from a few years ago, so I’m hoping to make this month sort of a “lightning round” to finally clear out the backlog.

(I’m not going to set a definite posting schedule this year because things are pretty chaotic right now. But I’ll try to fit in as many as I can!)

So let’s start off with a concept from an anonymous submitter, who requested a “kiwi/sengi niche alverezsaur”:

A shaded sketch of a speculative dinosaur. It has a long narrow snout, small eyes, and whiskery facial feathers like a kiwi bird, a round fuzzy body, short chunky arms with large hooked thumb claws, long slender legs, and a long tail with a tufted fan at the tip.

Khamartaia dolabella is similar in size and build to Shuvuuia, about 1m in length (3’3″), with slender legs and stumpy arms with massive thumb claws. Unlike its close relatives, however, it has small eyes and fairly poor vision, relying more on its other senses to forage around during the darkness of night.

It has an acute sense of smell, and its long narrow snout is full of highly touch-sensitive nerves, allowing it to probe around for invertebrate prey in soil, undergrowth, and cracks and crevices. Its chunky thumb claws are used to dig up burrows and to tear through bark to access deeper insect nests.

It mainly relies on its long legs to sprint away from threats, although with its poor eyesight these escapes are often rather ungainly.

Strange Symmetries #23: Convergent Earvolution

Although it’s not visible externally, owls have one of the most striking modern examples of asymmetry. The ears of many species are uneven, with the right ear opening positioned higher up than the left, giving them the ability to pinpoint the sounds of their prey much more accurately.

But surprisingly this isn’t a unique anatomical trait that only ever evolved once in their common ancestor.

Instead, multiple different lineages of owls have actually convergently evolved wonky ears somewhere between four and seven separate times.

The boreal owl (Aegolius funereus), also known as Tengmalm’s owl, is a small 25cm long (~10″) true owl found across much of the northern parts of both Eurasia and North America. While most other owls’ asymmetrical ear openings are formed just by soft tissue, the boreal owl’s lopsided ears are actually visible in the bones of its skull.

But despite how many times owls have convergently evolved asymmetrical ears, and how successful this adaptation has been for them, for a long time it seemed to be something that no other animals have ever mimicked.

In the early 2000s asymmetric ears were reported in the skulls of some troodontid dinosaurs, which seem to have been nocturnal hearing-based hunters similar to owls, but proper details on this feature still haven’t been formally published.

Then, just a couple of weeks ago, another example was finally announced.

The night parrot (Pezoporus occidentalis) is a small ground-dwelling parrot found in Australia, close to the same size as the boreal owl at around 22cm long (~9″). Critically endangered and very elusive, it’s rarely seen and little is known about it – and it was presumed extinct for much of the 20th century, until more recent sightings of living individuals confirmed that the species is still hanging on.

Recent studies of preserved museum specimens have revealed that it seems to have poor night vision but excellent hearing, and that its right ear opening is noticeably asymmetrical, bulging out sideways from its skull. Much like owls the night parrot relies on acute directional hearing to navigate in darkness, but since its diet consists mainly of seeds it’s probably not using this ability to locate food sources. Instead it may be listening out to keep track of the precise locations of other parrots, and for the approach of predators – so its sharp sense of hearing may be the reason this unique bird has so far just barely managed to survive the presence of invasive cats and foxes.

Strange Symmetries #20: The 16 Million Year Fiddler Crab Rave

Many decapod crustaceans have slightly asymmetrical pincers, often with one claw being chunkier and specialized for “crushing” while the other is more slender and used for “cutting”.

But fiddler crabs take this sort of asymmetry to the extreme as part of their sexual dimorphism – males have one massively oversized claw, which is used for both visual display to potential mates and for physical fights against rivals.

Some of the earliest fiddler crabs are known from the Miocene of what is now northern Brazil. Although the fossils have been given several different taxonomic names since their discovery in the 1970s (including Uca maracoani antiqua, Uca antiqua, and Uca inaciobritoi) they’re currently considered to be indistinguishable from the modern Brazilian fiddler crab, Uca maracoani, meaning that these crabs have remained externally unchanged for the last 16 million years.

Up to about 4cm in carapace width (~1.6″), modern Uca maracoani are found in coastal mangrove swamps and tidal mudflats around the northern and eastern coasts of South America – and some of these environments have also undergone little change since the Miocene. Males of the species can develop their enlarged pincer on either side of their bodies, with lefties and righties seeming to occur in equal numbers.

It Came From The Wastebasket #01: Is This An Insectivore?

Most of the wastebasket taxa featured this month are completely extinct and known only from fossils, but to start things off let’s take a look at a major example of how even groups with living members could have their classification muddled up for centuries.

The name Insectivora first came into use in the early 1820s, and was used to refer to various “primitive-looking” small insect-eating mammals, with modern shrews, moles, hedgehogs, tenrecs, and golden moles as the original core members.

An illustration showing the animals that originally made up "Insectivora". From left to right it pictures a shrew, a tenrec, and a hedgehog on the top row, and a mole and a golden mole on the bottom row. Text at top of the the image reads "Insectivora".

Then over the next few decades solenodons, treeshrews, sengis, and colugos all got lumped in with them too.

By the early 20th century insectivorans were considered to represent the “primitive” ancestral stock that all other placental mammals had ultimately descended from, and any vaguely similar fossil species also got dumped under the label. Extinct groups like leptictids, cimolestans, adapisoriculids, and apatemyids all went into the increasingly bloated Insectivora, too, making the situation even more of a wastebasket as time went on.

An illustration showing the animals that made up the expanded historical version of "Insectivora". From left to right it pictures a leptictidan, a shrew, a tenrec, a hedgehog, and a sengi on the top row, an apatemyid, a mole, a golden mole, and a solenodon in the middle row, and a cimolestan, a colugo, and a treeshrew on the bottom row. Text at top of the the image reads "…Insectivora?", styled like a typewritten label that has been stuck over the previous image's text.

The problem was that the only characteristics that really united these various animals were very generic “early placental mammal” traits – small body size, five clawed digits on the hands and feet, relatively unspecialized teeth, and mostly-insectivorous diets – and attempts at making sense of their evolutionary relationships were increasingly convoluted.

An image of a diagram from a 1967 academic paper, showing a complicated attempt to figure out the evolutionary relationships of "insectivores", with many different group names linked by arrows. For comparison next to it is the "Pepe Silvia" conspiracy wall meme.
…They’re the same image.

(Image sources: http://hdl.handle.net/2246/358 & https://knowyourmeme.com/memes/pepe-silvia)

The rise of cladistic methods from the 1970s onwards resulted in a lot of “insectivores” finally being recognized as unrelated to each other, removing them from the group and paring things back down closer to the name’s original definition. The idea that insectivorans were ancestral to all other placentals was abandoned, instead reclassifying them as being related to carnivorans, and the remaining members were recognized as just retaining a superficially “primitive” mammalian body plan.

Just shrews, moles, hedgehogs, solenodons, tenrecs, and golden moles were left, and to disassociate from the massive mess that had been Insectivora this version of the group was instead now called Lipotyphla.

An illustration showing the animals that made up "Lipotyphla". From left to right it pictures a solenodon, a tenrec, and a hedgehog on the top row, and a shrew, a mole, and a golden mole on the bottom row. Text at top of the the image reads "Lipotylpha", styled like an embossed label-maker sticker that has been stuck over the previous images' text.

But there were still no unique anatomical links between the remaining lipotyphlans. And then once genetic methods became available in the late 1990s, something unexpected happened.

Studies began to suggest that tenrecs and golden moles were actually part of a completely different lineage of placental mammals, the newly-recognized afrotheres, with their closest relatives being sengis and aardvarks. Meanwhile the rest of the lipotyphlans were laurasiatheres, closely related to bats, ungulates, and carnivorans.

Lipotyphla was suddenly split in half. For a while it was unclear if even the remaining shrew-mole-hedgehog-solenodon group was still valid – hedgehogs’ relationships were especially unstable in some studies – but by the mid-2000s things began to settle down into their current state.

Finally, after almost 200 years of confusion, the insectivore wastebasket has (hopefully) now been cleaned up. The remaining “true lipotyphlans” do seem to all be part of a single lineage, united by their genetics rather than by anatomical features, and are now known as Eulipotyphla.

A few fossil groups like nyctitheriids and amphilemurids are generally also still included, but since this classification is based just on their anatomy it isn’t entirely certain. The only exception to this are the nesophontids, which went extinct recently enough that we’ve actually recovered ancient DNA from them and confirmed they were eulipotyphlans closely related to solenodons.

An illustration showing the animals that now make up Euipotyphla. From left to right it pictures a solenodon, and a hedgehog on the top row, and a shrew, a mole, and an amphilemurid on the bottom row. Text at top of the the image reads "Eulipotylpha", with the letters "E" and "U" hastily scribbled onto the front of the previous image's text.

And a bonus image with species IDs:

Continue reading “It Came From The Wastebasket #01: Is This An Insectivore?”

Spectember 2022 #04: Aquatic Brontotheres

Squeezing in one last bonus #Spectember post this year!

This one isn’t based on a specific prompt, but instead is a companion piece to a previous one.

While North American brontotheres were adapting to the spread of grasslands, some of their Asian cousins took a very different evolutionary path through the rest of the Cenozoic.

Continue reading “Spectember 2022 #04: Aquatic Brontotheres”