Raspberry robfin
The European robin (Erithacus rubecula) was one of the most common, adaptable and successful bird species of the Quaternary period, at least in its range. Even with the Earth’s (relatively minor) struggles from humanity, the population always stood in the hundreds of millions. The robins had lifestyles full of opportunity, some even plunging into receding streams to catch fish during the harsh winters. These smart birds would take advantage of this strategy during the blistering glacial periods that would fluctuate throughout the period. In the next few millions of years, some robins would evolve to exploit this tactic further, into diving species similar to dippers and kingfishers. From that they’d take even further to the waters, evolving loon-like forms the size of seals (of any species), spending almost their entire lives in water, save when they needed to nest. But that would never be the norm, for some species had evolved viviparity, giving birth to live young without eggs. This would allow them to dominate even more aquatic environments. The whales that used to dominate the world’s oceans for millions of years were falling into decline into the Allogene period, and so a niche was open for the water robins, becoming the fully-aquatic erithacetes. These new rulers of the sea have a similar physiology to cetaceans, but as convergent birds have their own differences. The spikes of their snouts are not teeth, but serrated edges of their bills similar to the mergansers and pelagornithids of old. They also do not have melons to echolocate, but rictal bristles that have modified into stiff whiskers to sense movements in the water, their only feathers left. Finally, their caudals are actually modified hind-limbs, moving in a "clapping" manner for propulsion.
The raspberry robfin (Erithacetus rubecephalus), 50 million years from the (actual) time of writing, is a representative erithacete, the Allogene’s equivalent to the beaked and sperm whales of the Quaternary. This species gets its name from the big, red, raspberry-like mass of caruncles on the males’ heads, called a carubum. It is used both for attraction and for dominance. The bigger and redder the carubum, the more powerful the robfin. Speaking of which, it still carries on the aggressive, territorial legacy of its unassuming robin ancestors. Males will defend their own territories from eachother, and will attempt to back off each other with their carubums either for that or a mate. If that doesn’t work, a brutal tussle of serrated bills will occur that can result in death of either opponent. These solitary, carubum-ornate males grow to massive sizes of thirteen metres and fifteen tonnes. Females on the other hand are more gregarious, lack carubums, and size up at only nine metres and five tons, which is still enormous. This erithacete is a generalist predator of prey of up to "medium" proportions, from a diverse array of small sharks and other fish to other, non-erithacete birds and giant squid, the latter it hunts in the deep dark depths of the oceans, for this whale of a bird will regularly dive down there, up to thousands of metres down. Here is where its whiskers not only come in handy for sensory, but also as a lure. The abyssal raspberry robfin has a symbiotic relationship with bioluminescent bacteria on its whiskers, that light them up, attracting the curiosities of animals that might be on the robfin’s menu, similar to the bacteria that lights the escas of deep sea anglerfish. The raspberry robfin is a weird and wonderful predator of the Allogene oceans worldwide, a mighty leviathan with origins hailing from among the most unexpected kind.
My first Spectember piece of the year. There are lots of fully-aquatic bird concepts, often descended from seabirds which could be more likely as ancestors, but I’m just experimenting here with my favourite bird for that. It’s just fun.