Worldbuilding Stack Exchange is a question and answer site for writers/artists using science, geography and culture to construct imaginary worlds and settings. It only takes a minute to sign up.
Sign up to join this community
This is a submission for the Anatomically Correct Series
The snallygaster is a cryptid from Maryland. It is often described as resembling a half bird/half reptile like creature with large wings, a metal beak, tentacles like an octopus (sometimes depicted as emerging from its beak) and is known for snatching prey and draining them of their blood. Could something like this evolve naturally?
TL;DR: You are probably looking at a featherless therizinosaur with steering wings derived from shoulder blades, an internal bladder of lighter-than-air gas, a metallic-looking beak and a multi-appendaged, oversized tongue.
Well, I'm going to use this picture as a reference:
The first thing that strikes me here is that there are four limbs along with a pair of wings. This either means that it is a hexapod (Perhaps from an alternate Earth timeline where a six-finned lobe-finned fish colonized the land?), or that the wings are not developed from forelimbs.
Seen as the latter option is consistent with real-life evolutionary history, I'll go with that one. Instead, the wings can be in fact modified shoulder blades.
So, we now know that this is not a bird. Overall, its body plan is quite evocative, for me, of a therizinosaur:
The above depiction is currently outdated, as we now know that they had feathers, but it is entirely plausible that a therizinosaur could lose its plumage due to environmental pressures (Stable temperatures? Semi-aquatic habits?). The feathers on the wings could stay though, as they are far more aerodynamic than any other biological wing on Earth. Also, therizinosaurs were extant at the time of the K-Pg impact, so they could have been potential survivors.
That being said, it is obvious that the snallygaster could not be supported in the air by these tiny shoulder-blade wings. The illustration depicts it as airborne, so I imagine that the wings could be used for steering (and display, too) if it had some other method of buoyancy.
As for what that method of buoyancy would be, perhaps it fills an internal bladder/sac with hydrogen or methane, making it lighter than air? I'm not sure how plausible this is given the apparent large size of the snallygaster, but it's something to consider, certainly.
As for the beak, some therizinosaurs had beaks, so that's okay. The metal part is tricky though, but not impossible. Technically, steel is made from iron and carbon - elements which are both found in animal bodies, but I'm not really sure if it could form some kind of sheath over the keratinous bill. There are plenty of birds with shiny, grey beaks, though, and since the snallygaster is a cryptid, accounts will inevitably be exaggerated.
Lastly, the tentacles. Since they emerge from the mouth, the most plausible option for me is that they are derived from the tongue. If the tongue was to split into multiple appendages, which would be quite feasible evolutionarily, engorge those appendages and gain limited independent control of the members, it would resemble tentacles in every way.
Why would this evolve? Well, while therizinosaurs do have grasping hands, many have long claws which make any kind of dexterous use of the forelimbs quite clumsy. As such, the tongue could have evolved its tentacle-like properties as a means of attaining a prehensile organ. The prehensile forepaws are very important to how big cats hunt, and is in part why they can tackle such massive prey more than virtually any other predator. I imagine that the tongue could start out as being one, long, serpentine appendage, and then going on to split into more members to grapple with prey better.
I believe almost anything can evolve naturally. Life on Earth is incredibly varied, and organisms come in all different forms.
It is not too difficult to conceive of all the attributes of your creature evolving as they have evolutionarily occurred in other organisms:
So the only difficult one to achieve is a truly metal beak - although keep in mind beaks in current birds are quite strong and adequate for most purposes already.
A snallygaster could have evolved from a toothed ornithuran. It would most likely eat fish. At some point, some fish would start to eat huge amounts of plant matter, which they would store in a crop. The snallygasters would evolve to consume this plant matter, by entering symbiosis with methanogenic microorganisms similar to what is found in ruminants. They may store the methane they produce in the blind-ended portions of their respiratory system. This would reduce their weight, leading them to increase in size and density, and also to increase the size in the body of the methane-storing respiratory organs. They might switch diets to become predators, and develop scaly armour over their body, to protect against prey. It may become larger, and start to hunt large prey like an eagle. The snallygasters could at some point rapidly shrink in population, causing a genetic drift effect leading to many snallygasters having Cyclopia. These snallygasters, while not as intelligent, may be able to have larger, and better at focusing eyes, as the resources and space for eyes is not split between two eyes. The snallygasters may evolve an extremely loud shriek, in order to find mates over a large area.
In the ocean, there may be large, long-lived, intelligent octopodes, that live near the coast and are hematophagous. In order to avoid the snallygasters and other predators, they may become toxic and gain warning colours. A drop in oxygen levels could lead to these octopodes gaining simple lungs. These octopodes would be vulnerable to human hunters, who could cook their meat and make it edible, and so the octopodes would learn to hide in the nests of the man-eating snallygasters, using their warning signals to avoid being eaten. These octopodes would create tools, to help the snallygasters get the most meat out of each kill, as they benefit from having many snallygaster nests to hide in. Soon, the snallygasters would learn to keep the octopodes around, and start to protect them by hiding them in the top of their oesophagus. The octopodes would create tools for the snallygaster, such as a helmet to protect their eyes, ears, and other weak-spots.
The main issue of a real snallygaster is the half-bird/half-reptile thing. Any animal like that would be long dead once humans came, and likely too unlike the snallygaster for the realms of plausibility
However, the world is full of tiny distant branches on the tree of life, and evolution can be a powerful thing, so let's continue
Firstly, we need an ancestor: To best fulfill the snallygaster, we'd ideally get something primitive with pennaceous feathers. Unfortunately, pennaceous feathers are restricted to the maniraptors, with true flight feathers themselves even more limited in scope. Taking this into account, we can make the snallygaster as a small primitive oviraptor, with wings and beak, but a long tail and teeth as well
This oviraptor is still far from the snallygaster, and there's a mass extinction heading its way. We could make progress with both issues if this species were to adapt to arboreal life. This would give us many changes useful to our ends; It could likely gain grasping feet and wings, and perhaps even become flighted. All these traits would bring it one step closer to the snallygaster
Being smaller, this species could likely survive the mass extinction just as well as the various avian clades. However, like all animals, it will need to change first. Firstly, it will likely have to lose its arboreal adaptations for the lack of trees (while their were some trees, they were rare and ground-dwellers often had the advantage). Given that all their limbs were in use in the trees, it seems reasonable that the same would stay true on the surface
These terrestrial creatures would benefit from some protection, both from the rough ground and from predators. Scales would be quite useful to this end. One plausible arrangement could be having the head, chest, and wings be feathered for aerodynamics, with the feet, legs, and tail being scaly to maximize protection. This would make these proto-snallygasters much more reptilian
After the extinction, there would be many niches to fill, especially for fliers. A good niche for this proto-snallygaster would be a piscivore. This would motivate adaptations like a long beak and sharp teeth, like a snallygaster. These piscivores, given the right environment, could become rather large. This shouldn't be an obstacle to flight: Argentavis, a flighted bird, was heavier than a human being
Piscivores need not subsist solely on fish. They would likely add other foods to their diet, if possible. Perhaps these snallygasters (or at least some of them) could take on a more eagle-like lifestyle, to supplement their diet if there aren't enough fish. While they won't be able to pick up human-sized beasts, small children and other similar-sized creatures would be more than light enough
They will need some way to hold their prey, however, as unlike birds they would only have 3 forward-facing toes. They could grasp small prey between the hindfeet, but they will need a better solution. One such possibility could be a large hooked claw like that of the dromaeosaurs, which could be turned out like a thumb to grab prey
Now we have made quite a snallygaster, but there are still some obstacles to the complete picture. Some traits could be considered as display; Reflective colouration could account for the metallic beak and steely claws, and a locomotive-like whistle could be an effective mating call. However, the other remaining traits are hard to justify
Tentacles, especially those of the octopus, are full-fledged limbs, which would be hard to add to such an advanced tetrapod. We can still do something similar, though
While reptiles and birds do not have cartilages on their face, it isn't totally implausible for the snallygaster to have them. A set of cartilaginous display nubs around the mouth would be a good origin for tentacles. These nubs could likely extend out as a Fisherian runaway, forming long flexible structures that would seem remarkably close to tentacles
The central eye would be another issue. Cyclopia, while it has the desired effect, is always accompanied by many other deleterious features. However eyespots (or fake eyes) are very common in nature
A single scaly eyespot in the forehead would be a useful feature, as it would resist attacks more than a feather eyespot, and it is where attackers would expect an eye. This could adapt into a large, shell-like eye-dome in the centre of the forehead
Finally, we must discuss its hematophagy. A large animal like the snallygaster could not subsist on blood alone, but other animals can
If the snallygasters are capable of withstanding hematophagous worms and bugs (which shouldn't be implausible with their thick skin and scales), then they could use these bugs as a defense, going to dense areas and even cultivating their numbers. This would inevitably result in any meat they store ending up wholly drained of blood before they go to eat it. This won't be much of a downside for the snallygaster, as there are still a lot of nutrients left over, as our own diets can attest
Overall, these changes would lead to an animal very much like the snallygaster of folklore
The metallic beak and claws are hard to swallow, but not quite as farfetched as one might think. There is one real-life animal, the scaly-foot gastropod, a deep-sea snail which incorporates metallic iron into its physiology in order to produce a functional metallic shell. But the snail lives around deep-sea vents which pump out vast quantities of free molecular iron sulfide, and contains symbiotic chemosynthetic bacteria which eat the iron sulfide and provide the snail with both energy and free iron atoms. The snail was getting iron as a waste product before it evolved something to do with it. It's a lot harder to imagine a similar evolutionary path happening in a terrestrial avian.
However, it is noted that the Snallygaster has a taste for blood. While it's unlikely that a large predator would subsist entirely on blood, it is possible that it evolved from a much smaller creature that did. Animals that drink blood need to have some means of removing the excess iron to avoid iron poisoning. So, perhaps the evolutionary path looked something like this:
Small birdlike predator evolves to occasionally drink blood
Small birdlike predator learns to extract iron from blood in order to tolerate a blood-based diet
Small birdlike hemovore learns to incorporate the excess iron into its hard body parts, assisting in its offensive capabilities - perhaps allowing it to slice open veins like a living scalpel
Small birdlike hemovore can now kill larger animals more easily and returns to a predatory lifestyle
Snallygaster grows to its current size to tackle larger prey, but retains its taste for blood and ability to incorporate iron into its beak and claws
Half-bird half-reptile isn't too farfetched, as birds are pretty reptilian already and this could easily be a member of a living fossil clade that branched off around the time of the dinosaurs. An additional set of dragon-like wings, such as those in your picture, are less plausible on an Earth tetrapod, but if we modify the design a bit we could get clawed wings such as one might find on a primitive avian, and that's fine.
The mouth tentacles could be highly modified tongue (tongues are basically tentacles already, and snakes show that it is possible for them to split into multiple branches). I'm not sure what its function could be, but "mating display" is always an easy choice when all else fails.
