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Description

On one of seeded worlds, fish came out of water. But that fish wasn’t bony, it was a shark, actually.

Unlike Sarcopterygii (and just bony fish in general), sharks don’t have enough skeleton to actually ossify. But they didn’t have other fish on their world, and plenty of new food source there, on surface. And, instead of developing their internal skeleton, they started developing external one.

As sharks have some structure covering their skin, which is homologous to teeth, they at first made it much thicker to live semi-amphibious way (just hiding from aquatic predators for some time and occasionally feeding there). The next step was to develop proper way of breathing surface air, and by creating complex internal ‘gills’ which action like lungs, they made this as well. Two spiracles by which they breathe are located on the sides of the head, which is, in turn, the only place with properly ossified internal skeleton. Some forms then developed ears, as it was advantageous to hear the coming predator or prey. And, already being viviparous, they didn’t really struggle with conquering the landmass on which they evolved.

However, there was a realm which they couldn’t claim for a long time: the air. Being big, heavy, and without much evolutionary need to became flighted, they didn’t. But a diverse array of insects and insect-like flyers remained, and with that one group of arboreal insectivores made its exoskeleton much lighter and grew a new, ‘toothy’ wing. It still was a glider though, as not much needed musculature appeared. They could fly up from ground, but to become full-time flyers they needed to become much smaller.

The new flyers’ size is comparable to insects, though due to active respiration they can become bigger, somewhere to chicken-sized. They utilize new niches from aerial insectivores to very specialized pollinators, and sometimes even sanguivores which stalked herds of herbivore terrestrial sharks or hunted small animals like a flying spider. Their diversity became comparable to their flightless relatives.

Pictured a gliding, more-terrestrial flying shark and two species of its flying relatives. The one on background, near former animal, is an insectivore which flies near animals, spotting parasites on their skin and eating them (or, in the case of parasite being sanguivorous flying shark, drive it away). On the foreground a pollinator is tricked by a trickflower. This pollinator is specialized to pollinate a few flower species which have nectaries hidden deep inside the flower itself, but trickflower otherwise could be mistaken for a simple plant. Its secret are its smell and color, as, by smell, they appear to be flowers on which pollinator usually feeds, and by color they trick its vision, appearing to be such flowers. The pollinator, however, despite pollinating this flower, doesn’t feed in process at all.

Description

On one of seeded worlds, fish came out of water. But that fish wasn’t bony, it was a shark, actually.

Unlike Sarcopterygii (and just bony fish in general), sharks don’t have enough skeleton to actually ossify. But they didn’t have other fish on their world, and plenty of new food source there, on surface. And, instead of developing their internal skeleton, they started developing external one.

As sharks have some structure covering their skin, which is homologous to teeth, they at first made it much thicker to live semi-amphibious way (just hiding from aquatic predators for some time and occasionally feeding there). The next step was to develop proper way of breathing surface air, and by creating complex internal ‘gills’ which action like lungs, they made this as well. Two spiracles by which they breathe are located on the sides of the head, which is, in turn, the only place with properly ossified internal skeleton. Some forms then developed ears, as it was advantageous to hear the coming predator or prey. And, already being viviparous, they didn’t really struggle with conquering the landmass on which they evolved.

However, there was a realm which they couldn’t claim for a long time: the air. Being big, heavy, and without much evolutionary need to became flighted, they didn’t. But a diverse array of insects and insect-like flyers remained, and with that one group of arboreal insectivores made its exoskeleton much lighter and grew a new, ‘toothy’ wing. It still was a glider though, as not much needed musculature appeared. They could fly up from ground, but to become full-time flyers they needed to become much smaller.

The new flyers’ size is comparable to insects, though due to active respiration they can become bigger, somewhere to chicken-sized. They utilize new niches from aerial insectivores to very specialized pollinators, and sometimes even sanguivores which stalked herds of herbivore terrestrial sharks or hunted small animals like a flying spider. Their diversity became comparable to their flightless relatives.

Pictured a gliding, more-terrestrial flying shark and two species of its flying relatives. The one on background, near former animal, is an insectivore which flies near animals, spotting parasites on their skin and eating them (or, in the case of parasite being sanguivorous flying shark, drive it away). On the foreground a pollinator is tricked by a trickflower. This pollinator is specialized to pollinate a few flower species which have nectaries hidden deep inside the flower itself, but trickflower otherwise could be mistaken for a simple plant. Its secret are its smell and color, as, by smell, they appear to be flowers on which pollinator usually feeds, and by color they trick its vision, appearing to be such flowers. The pollinator, however, despite pollinating this flower, doesn’t feed in process at all.