Month: October 2023

Spectember/Spectober 2023 #11: A Large Spider

An anonymous submission requested a “spider the size of a coconut crab”:

A shaded sketch of a speculative giant herbivorous descendant of jumping spiders. It's a big stocky spider covered in fuzz, with thick legs ending in cloven-hoof-like claws. It has the characteristic large main pair of eyes of jumping spiders, with the other three pairs more spread out around the front and sides of its wide head, and it also has two pairs of "horns". Its abdomen is wide and round, somewhat flattened on the top, with several spiky structures around the edge.

Ceratohispidus aspectus is a distant descendant of jumping spiders living on an Aotearoa-like landmass, isolated with no mammalian predators.

This particular lineage is notable for both their extreme gigantism (with their larger size and weight causing them to lose the ability to jump) and for having taken up herbivory in a similar manner to one modern species. Most of these big plant-eating spiders are around the size of wētāpunga, and occupy a similar ecological niche, but Ceratohispidus is the largest of them by far – rivalling the modern coconut crab with a body length of up to 40cm (~1’4″) and a legspan of almost 1m (~3’3″).

After reaching sexual maturity at 5-10 years old, adults grow very slowly, molting only once every year or two and taking several decades to actually get anywhere close to their maximum size.

Ceratohispidus’ thick legs end in hoof-like claws, and it selectively browses on vegetation by snipping off pieces with its pincer-like palps. A gizzard-like structure in its digestive system helps to grind up fibrous plant material with small gastroliths, and its wide abdomen houses both large book lungs and a tracheal system with air sacs that can contract and expand to provide a small amount of active ventilation.

While the “horns” and spikes ornamenting its body may provide some defense from the few avian and reptilian predators in its habitat, they’re mainly used as part of highly elaborate visual displays between individuals.

Spectember/Spectober 2023 #10: Tree Goat

An anonymous submitter asked for an “arboreal goat with grasping sloth-like claws”:

A shaded sketch of a speculative tree-climbing descendant of goats. It's a hairy sloth-like animal, clinging to a tree trunk with long chunky limbs that end in large hooked claw-like hooves. Its head is proportionally small, with fleshy giraffe-like lips, forward-facing eyes, and small stubby horns.

Cluraix cephalula is a distant descendant of feral goats in a tropical forest environment, representing a small tree-climbing offshoot of a specialized chalicothere-like lineage.

About 70cm long (~2’4″), it clambers around in the high tree canopies, with its forward-facing eyes providing good depth perception in this complex three-dimensional habitat. Its long hooked claw-hooves are used both to cling onto branches and to hook-and-pull clumps of foliage towards itself, stripping the leaves with its flexible fleshy lips.

Spectember/Spectober 2023 #09: Things With Wings

(Apologies for the abrupt absence – I’m okay, just having everything break down at once. This is fine.)

So— back to the speculative evolution request list!

TheBigDeepCheatsy requested a “cactus-dwelling/germinating evolution of introduced rosy-faced lovebirds”:

A shaded sketch of a speculative symbiotic relationship between lovebirds and saguaro cactus. The lovebird is shown on the left, a small parrot that looks very similar to modern rosy-faced lovebird except with hints of a more mottled color pattern. The cactus is shown on the right, a large fasciated saguaro with its top fanning out into a wide "crown", with several nest holes dug into it and multiple lovebirds occupying them.

While Agapornis cheatsyi is still quite physically similar to its introduced ancestors, this lovebird has developed a close symbiotic relationship with the cactus Carnegiea ornipolis, a descendant of the modern saguaro.

Naturally fasciated, this cactus grows a splaying fan-like crown which the lovebirds excavate their shallow nest burrows into. Feeding on the cactus’ fruit in early summer, the lovebirds then disperse the seeds via their droppings – a process that significantly improves propagation chances, both due to the birds commonly foraging and defecating around suitable nurse plants and the passage through their gut speeding up germination.

Someone calling themself “LB” asked for some “flying afrotherians”:

A shaded sketch of a speculative flying tenrec. It's a bat-like animal with membranous wings supported by three elongated fingers, and a large shrew-like head with long toothy jaws and an elephant-shrew-like nose.

Elbeitandraka venenifer is a descendant of tree-climbing Malagasy tenrecs that developed gliding membranes – and its lineage is now just about achieving true powered flight.

About 25cm long (~10″), its proportionally short broad wings require it to fly very fast to generate enough lift for its weight. It mostly only actively flies when traveling between roosts and feeding sites (or when escaping from threats), alternating between gliding to save energy and flapping to recover altitude.

It’s an opportunistic omnivore, crawling around in the tree canopy foraging for vegetation, fruits, fungi, invertebrates, and the occasional smaller vertebrate, using its flexible sengi-like nose to probe around in crevices.

Much like modern common tenrecs it’s capable of hibernating for months at a time through periods of scarce food availability. It also accumulates alkaloid toxins in its body from its arthropod prey, advertising its unpalatability to predators with bold contrasting warning coloration on its wing membranes.

And here’s a combination of a couple of anonymous requests for both “flying heterodontosaurs” and “dragons with hind leg wings, a la sharovipteryx”:

A shaded sketch of a speculative flying predatory heterodontosaurid dinosaur, show both on the ground in a quadrupedal posture and in flight. Its hind legs form its main wings, with elongated outer toes supporting large pterosaur-like flight membranes. It also has a hooked beak at the front of fanged jaws, an s-curved neck, a compact fuzzy body, short forelimbs with taloned hands and small stabilization membranes, and a long vaned tail.

Inversodraco rapax is a highly specialized Jurassic descendant of heterodontosaurids that took to climbing and gliding, developing delta-wing-like membranes on their hindlimbs convergently similar to those of the earlier sharovipterygids.

Around 75cm long (~2’6″), it has unusually flexible hip joints for a dinosaur, able to splay its legs out to the sides to deploy wings supported by an elongated outer toe on each foot. Its arms form small forewings for stability, and its long tail ends in a vane of stiffened feathers that aid in steering.

Unlike its herbivorous-to-omnivorous ancestors it’s primarily a carnivore, swooping down onto small prey and grabbing it with its talon-like forelimbs.

Spectember/Spectober 2023 #08: Various Filter-Feeders

Admantus asked for a “freshwater baleen whale”:

A shaded sketch of a speculative freshwater baleen whale. It has a very wide duck-like snout with whisker-like bristles, short baleen inside its mouth, very small reduced eyes, and broad paddle-like flippers.

Rostrorutellum admantusi is descended from small cetotheres that became isolated in a large inland body of water (similar to the modern Caspian Sea), eventually becoming landlocked and gradually reducing in salinity towards fully freshwater.

Highly dwarfed in size, just 2-3m long (~6’6″-9’10”), they’re slow swimmers with broad duck-like snouts that are used to scoop up mouthfuls of sediment and strain out their invertebrate prey in a similar feeding style to gray whales.

Due to the murkiness of the water, and the lack of large predators in their environment, they have poor eyesight and instead use sensory bristles and electroreceptors around their snouts to navigate and detect prey.

And an anonymous submission requested a “whale-like filter-feeding marine crocodile”:

A shaded sketch of a speculative filter-feeding crocodile. It has spatula-like jaws lined with many delicate closely-spaced needle-like teeth, flipper-like limbs, and a long paddle-like tail.

Sestrosuchus aigialus is a 6m long (~20′) crocodilian closely related to the modern American crocodile, living in warm shallow coastal waters.

It’s adapted for an almost fully aquatic lifestyle convergently similar to the ancient thalattosuchians, swimming with undulations of its long tail and steering with flipper-like limbs. But unlike other crocs it’s specialized for filter-feeding, with numerous delicate needle-like teeth in its jaws that interlock to sieve out small fish and planktonic invertebrates from the water.

A couple more suggestions also asked for “fully aquatic pinnipeds” and “future crabeater seal evolution”:

A shaded sketch of a speculative filter-feeding fully aquatic crabeater seal. It has four wing-like flippers, a streamlined body, and elongated jaws with many lobed teeth used to sieve krill.

Euphausiolethrus volucer is a fully aquatic descendant of the crabeater seal. About 5m long (~16’4″), it occupies the ecological niche of a small baleen whale in the krill-abundant Antarctic waters that lack most actual baleen whales.

Its jaws contain numerous finely-lobed teeth that are used to strain krill from the water, and it utilizes all four of its wing-like flippers to swim in an “underwater flight” motion similar to that of plesiosaurs.

Highly social, it tends to congregate in pods that cooperate to herd swarms of krill for easier feeding.

Spectember/Spectober 2023 #07: Terror Eagle

September might have ended, but guess what? I am not remotely done with this yet so we’re continuing on.

Now it’s Spectober.

(Also just a reminder: I am not currently taking new requests. I’ve got far too many existing ones that I’m still working through!)

Someone who identified themself only as “Adam” asked for “eagles evolving into terrestrial predators to pursue larger prey”:

A shaded sketch of a speculative flightless eagle. It has a large head with a big hooked beak, with the skin on its head and neck only sparsely feathered like a vulture. It's body is chunky and covered in shaggy feathers, and it has thick legs and stumpy tail. Its small vestigial-looking wings have a large bony knob growing from just below the wrist joint.

A flightless eagle occupying an apex predator niche in the same island chain as the giant herbivorous tegu, Terraetus adamii is descended from a species similar to the modern harpy eagle. It isn’t substantially larger than the biggest modern eagles – standing about 1.2m tall (~4′) – but it’s certainly much more massive, weighing around 25kg (~55lbs).

In the absence of other large terrestrial predators its ancestors originally took up a caracara-like lifestyle, preferring hunting on foot over flying, before gradually becoming totally flightless and converging on terror birds with large heavy skulls, reduced wings, and powerful legs.

Terraetus’ head is only very sparsely feathered, an adaptation for feeding inside the carcasses of large prey, which it dispatches using a combination of kicking and blows from its large hooked beak. It’s usually a solitary hunter that can tackle prey up to two or three times its own weight – preferencing the juveniles of the herbivorous tegu – but during the breeding season pairs will occasionally hunt cooperatively to take down larger targets.

Despite possessing sharp beaks and talons, these weapons aren’t actually used in fights between individuals of this species. Instead they bodily shove each other back and forth, battering at each other with large bony knobs that grow from the hand bones of each wing.