Fangworms

During the Tempuscene, some 200 million years ago, the eelsnakes evolved from the swordtails. These predator fishes were elongated, their fins reduced, with strong jaws. They were amphibious, able to hunt out of the water as long as they stayed damp, and could breathe atmospheric oxygen and absorb it directly into the lining of their gut. Eelsnakes would become a group with incredible staying power; they have survived all that Serina has so far thrown at them, including the Thermocene-Pangeacene mass extinction, to which they were well-adapted with their semi-aquatic habits to survive in the few existent riverine refugia at that time. But over so long, the eelsnakes have changed very little compared to their better-known distant relatives the tribbetheres, whose first mudwicket ancestors diverged from the guppy lineage around the same time as the first eelsnakes appeared. Frog-like mudwickets went on to produce the reptile-like tribbets, some of which went on to evolve into the myriad of diverse, mammal-like tribbetheres that dominate Serina today (though very primitive mudwickets still exist on Serina.) Eelsnakes never produced a tribbet-like radiation of megafauna unrecognizable from their ancestor. Their success lay in the simplicity of their bodyplans. Modern eelsnakes are easily recognizable, having changed in only a few, mostly superficial ways. All of them give birth to small litters of very well-developed young, which have a placental connection to the mother. All of them can breathe both above and below water, and the majority can - at least during some life stages - move on both land and water. They are also all carnivorous.

One of the most successful groups of these amphibious fishes in the early to mid Ultimocene are the fangworms, small animals never more than 20 inches in length, which fill a role in the ecosystem somewhere between a salamander and a small snake. Fangworms have entirely lost all of their fins save for their pectoral fins, which have developed a bony support and evolved into small, two-lobed arms helpful in aiding it to climb. They are commonly found in damp, cool forest habitats and along swiftly moving streams and are able to survive indefinitely both on land - so long as they remain moist - and under water - as long as it is cold and highly oxygenated - because they have both highly permeable skin that can take oxygen out of fast flowing water and gut-derived lungs with which to breath air. Fangworms are extremely cold-hardy; most of the water in their bodies, including their blood, can freeze solid and they can revive once thawed thanks to antifreeze proteins in the cells of their tissues, but are intolerant of high heat, which means the modern cooling climate is benefiting them, allowing them to colonize the equatorial region. Today these small, seemingly unassuming creatures are only still found on Serinarcta, but their range formerly included much of Serinaustra before its glaciation.

Fangworms feed on a wide variety of prey including fish, invertebrates, birds, and small molodonts. They are largely passive hunters which wait for their prey to find them and then ambush it, but some search out their food by scent. Different species may be found either below ground in burrows, under leaf litter or in the rocky bottoms of rivers and some can be found in all three. When suitable food comes within range, they strike out quickly and ensare it in their backward-hooked teeth. If the prey is small like an earthworm or a small minnow, it is swallowed whole, but if it is relatively large - like a molodont or a sparrowgull - it is now that the reason for their common name is apparent, as two very elongate, hollow teeth in the upper jaw chew a venomous saliva into the victim. This allows the fangworm to subdue animals much larger than it otherwise could, including molodonts as large as rats and several times its weight. The venom is fast-acting and neurotoxic, causing the prey to stop breathing and die of suffocation in just a few seconds. In its way of feeding on large prey the fangworm is very different from either a salamander or a snake; unable to swallow it whole, it will drag its large quarry to a secluded hiding place nearby and feed in peace by chewing open the belly and entering to feed on the softer entrails and then moving on to the muscles, while avoiding the tough skin.

Fangworm venom is, to different degrees, dangerous to larger animals as well as prey and so is useful for defense. Many fangworms, though colored cryptically on top to allow them to hide, show bold red or yellow aposematic markings on their underbellies. If threatened by a predator, these small eelsnakes will flip onto their backs to reveal the bold colors and writhe around violently with the jaw open and fangs exposed, advertising that they can deliver a deadly bite and are best left alone. Most enemies respect the warning and will make a retreat, which is all the better for the fangworm as venom is metabolically expensive to produce and best left available to use in hunting. If for some reason an animal tries to attack the creature anyway, the fangworm will bite and the effects can vary from almost instant death for animals up to the size of a cat to only permanent nerve damage in the afflicted limb for larger animals. Though preyed upon by certain other species of eelsnakes, just about the only birds that regularly hunt and kill fangworms are snifflers - small trunko birds which are so quick and agile, they can often kick the creature to death before it can ever land a bite.

above: the firebellied fangworm lives in the temperate forests of extreme southern Serinarcta. When threatened, it flips partway onto its back to expose bright red ventral patterns, and curves into a figure-eight with its jaws widely agape in threat posture. If pressed further it will bite with enough venom to almost instantly kill most birds under twenty pounds, except for the snifflers which - quick of reflex and probably somewhat immune to their bite - often eat them with impunity.