An anonymous request asked for a “large ankylosaur-like herbivorous notosuchian“:
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”:
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.
Someone who identified themself only as “Hanna” requested a “mammal that’s shiny and iridescent like some insects and spiders”:
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.
An anonymous submitter asked for a “penguin/auk-like relative of Pelagornis“:
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”:
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.
Modzilla07 asked for a “eurypterid or anomalocarid-esque isopod”:
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.
An anonymous submitter asked for a “derived carnivorous, pack-hunting agriochoerid“:
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!)
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.
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”:
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.