Tiny fish of the genus Lycoptera, sparring over territory among submerged Archaefructus leaves.
There are practically no life reconstructions of this animal, so I ended up making a quick piece of my own. Lycoptera is by far the most common fossil animal in the Yixian Formation. There are literally thousands and thousands of them. It's a relative of modern osteoglossiforms: arovanas, African knifefish, elephantnose fishes and mooneyes.
I noticed some fossil specimens have a disproportionately long caudal fin. In some modern species of small fish (such as Rasbora trilineata) this sort of long fins are patterned and act both as signals to keep a school together in murky water, and as ornaments. In many species of small fish, the schools or shoals break up during spawning season, and individual males form tiny spawning territories among aquatic plants. They then spar with each other, circling and showing off their colours to attract females.
I thought it would not be unreasonable to reconstruct similar behaviour for Lycoptera, as it seems to be ecologically similar, even though it's not closely related to modern cyprinids or characiforms.