Bumblets of the Middle Ultimocene

Bumblets are the only living vivas, descended from aardgeese that evolved to incubate their eggs internally 210+ million years ago, and have been since the extinction of all other species at the end of the Thermocene 175 million years PE. Bumblets today carry many highly derived characters that were absent in other viva groups; namely they are fully viviparous and entirely quadrupedal, characteristics that have only ever evolved in a single other bird group, the metamorphs. Both of these adaptations began evolving in the earliest bumblet ancestors as they adapted from large cursorial birds - like ostriches - into subterranean burrowing animals - like kiwis - in order to avoid predators. Bumblets adapted the large thumb claws their even earlier ancestors evolved to defend themselves into soil-moving shovels, becoming the first wing-powered digging birds which over many millions of years resulted in their forearms becoming highly modified. The upper arm bones receded while the wrist became the primary driving force powering arm motions; this gradually allowed the bumblets to bear weight on their wings. Such primitive bumblets had sprawling forearms, but derived species which needed to move more quickly above ground later evolved to stand fully erect again, as the wrist extended to function as and replace the entire forearm, rotating only at the shoulder and flexing at its distal tip where two fingers remained, each ending in secondarily evolved keratinous claws not homologous to those of bird ancestors (ancestral canaries had already lost their original wing claws.)

Bumblets were the first birds to circumvent the constraints of egg-laying to give birth to live young, which required laying soft eggshells with little to no calcium. This would be fatal to most birds, but bumblets adapted to be born at increasingly early stages with their bones undeveloped, and then to be provided the minerals necessary to develop their skeletons through food by the mother. The first vivas only kept their eggs in their oviducts until they hatched, providing no internal nourishment but developing a complex cloacal pumping system to oxygenate the developing eggs. Bumblets adapted to oxygenate their oviducts directly from their respiratory systems, with the tissue of the oviduct becoming heavily vascularized and diffusing oxygen directly from her bloodstream through the thin eggshells to oxygenate the embryos. Over time the system still in place by all modern bumblets evolved where the egg’s shell was entirely lost and a membrane produced by the embryo fuses to the embryo via a placental cord, and there developed directly nourished by the mother’s blood supply. This allowed bumblets to evolve to give birth to large and relatively well-developed young with already developed bones, as occurs with gravediggers and other bumblebadger species, and is similar to the evolutionary process that also allowed certain metamorph birds to give birth to large and precocial live young. 

Bumblets survived where no other vivas did because they were burrowers, already adapted to harsh low-oxygen conditions. Furthermore, an invertebrate-based diet - invertebrates, especially decomposing ones like earthworms, were less reduced than either plants or vertebrates - and a fondness for damp soils meant they could depend on freshwater riverine ecosystems to find food, and these were the least affected environments in the aftermath of the end-Thermocene extinction. But through the Pangeacene, in a world stripped of most of their former competitors, the bumblets were able to return to the surface and undergo a new radiation. Initially overshadowed by other megafaunal quadruped birds - the metamorphic placental birds - that overcame the limits of the bird wing and evolved to walk on their forearms through developmental neoteny, today such birds are no longer doing as well. Bumblets, however, have continued to thrive even in a cooling world and have lost relatively little diversity. 265 million years PE, both fairly primitive and highly derived forms still exist of these carnivorous quadrupeds, ranging in size from the wormslayer, a tiny burrowing form that weighs only three ounces, to the truculent bumblebear: an apex land predator standing eight feet tall on all fours. Bumblets are intelligent birds and have already reached sapience once with the gravedigger, and additional species exist near the cusp including an entire clade of highly social, dolphin-like oceanic predators which have completely severed ties with the land, turning all four of their limbs into flukes and swimming with alternate strokes in the same way as Earth plesiosaurs. 

All bumblets have keratin teeth. While these are not structurally the same as the teeth of bird ancestors, rather being evolved from keratin spikes on the ancient herbivore viva’s beaks that they used to chew plants, their function today is the same. Keratin teeth develop somewhat like a horn and somewhat like an antler; a bony core develops over time in the tooth’s development, surrounded by hard beak keratin, so that each tooth is structurally like the horn of an ungulate. But these teeth are also periodically shed and regrow, like antlers, and must develop through a soft and vascularized stage similar to an antler in velvet before they erupt from the gums hard and ready for use. Bumblets ancestrally lost the hard beak of their ancestors but have subsequently re-evolved it some three different times when it proved beneficial again, in each time by covering the soft flesh of the snout with a harder keratin layer (archosaurs, the group to which all birds including bumblets belong, were notorious for evolving beaks in numerous unrelated families long before any endemic Serinan species had diverged.) Today the wormslayer and its relatives still lack a hard beak, whereas the bumblebadgers, the dolfinches, and the spiny snoots (not to be confused with the unrelated snow snoot, a trunko) have bird-like beaks, though in some dolfinches they are less keratinized than others and more alike the softer beak of a dolphin. Bumblebadgers always have serrated beaks evolved for shredding flesh at the distal tip of their jaws, a trait also seen in some macropredatory dolfinches, but spiny snoots have a completely smooth bill, adapted to probe for worms in the dirt.

All living bumblet clades represent grades in evolution. The wormslayer is similar to the common ancestor of the other three clades, and spiny snoots resemble the ancestors of bumblebadgers which themselves include bumblebears, a subset of animals structurally identical, only larger, that form a polyphyletic group within them. Dolfinches split from spiny snoots and bumblebadgers very early, at the beginning of the Pangeacene, and today have been highly modified for aquatic life but can have some passing resemblance to bumblebadgers through convergent evolution of their jaws. 

Sample of Species

The wormslayer is a very primitive-looking bumblet, though it is not a living fossil; it too has the same, more advanced reproductive system common to all other living species, and so comes from the same more recent radiation of evolution. These small bumblets still live underground and as their name suggests primarily hunt earthworms. They are native to southern Serinarcta, across the forest refugia and much of the harp steppe, avoiding the dry continental interior and tundra to the north.

Giant spiny snoots may not look especially massive, but they are quite large for snoots, which otherwise are rarely more than five or six pounds in weight. The giant snoot however weighs up to twenty pounds and thus has somewhat reduced its protective covering of spines, as it has fewer predators. All snoots represent the first grade of evolution of bumblets returning to the surface as terrestrial animals; they have regained upright forearms, but still feed primarily on a similar diet to their ancestors: worms, though they now probe for them from the top of the ground rather than catch them from below. Spiny snoots are somewhat omnivorous, however, and will also feed on seeds, insects and fruit. This species is native to the towertree taiga. 

A very typical bumblebadger, three-stripes are functionally similar to the ancestors of gravediggers. Though they have not learned to utilize traps or tools to hunt, they are intelligent and skilled problem solvers. Living in underground dens in small family units, they are still relatively social animals. Like gravediggers they favor meat but can consume a variety of plant foods when necessary. Three-striped bumblebadgers live across most of southern Serinacta. 

Bramblebreakers are an animal nobody wants to meet. Short but stocky, made up of little more than pure muscle, these exceedingly bad-tempered bumblebadgers can weigh three hundred pounds and are primarily predatory. They are endemic to the cactaiga biome where they hunt young thorngrazers and steal carrion from anything weaker than themselves. Like the thorngrazer, these sturdy animals can break paths through the brambles and so despite their fierce nature can benefit smaller animals by opening up the thick vegetation. 

The final clade of bumblets are the most divergent from any other; dolfinches are exquisitely adapted marine animals whose bodies have been shaped by time into smooth, hydronamic forms adapted to easily fly through the cold equatorial ocean in pursuit of fish and other aquatic prey. Entirely aquatic, dolfinches have no remaining claws or differentiated digits. Swimming is done through flapping motions of all four legs in alternation. Very social, dolfinches live in large, extended families most often led by the eldest females. The whitebeaked dolfinch is a member of a smaller, fast-moving group of fish hunters common to open waters of the icebox seaway. It is hunted by tortorncas - ferocious giant burdles - but also by its own, larger relatives.