When: Late Devonian (~387-360 million years ago)
Where: Globally, found in both fresh water and marine shoreline deposits.
What: Bothriolepis is a placoderm. Placoderms were a group of heavily armored prehistoric fish. This placoderm had a very ‘box-like’ dorsally-ventrally compressed shell, as its head armor was fused with its thoracic shield. Bothriolepis had pectoral fins that were armored as well, but these fins were mobile, having a joint at the base of the fin and one at the midpoint. There were two openings on the anterior surface of the shell, the top opening served to allow its eyes to peer out from its carapace. This dorsal position is different from the anterior placement of eyes in most fishes. The ventral opening was for its mouth; Bothriolepis had no jaws, instead just a mouth composed entirely of soft parts. It is thought to have been a bottom feeder, swimming around on the lake or ocean floor and sucking up food-rich sediments.
Bothriolepis was a very successful genus of placodems; there are over 100 recognized species, many of which pop up in short succession in an explosive radiation. Why was it so successful? Many Bothriolepis specimens are found in freshwater deposits, an environment that was just starting to be colonized by vertebrates. As Bothriolepis is also found in marine sediments near shorelines, it is theorized that they could have swam inland to lay eggs and thus the young would be protected from the ocean predators. If these young swam back to the same fresh water lakes and rivers every time to then breed themselves, the populations would quickly diverge. Additionally, evidence from some exceptionally preserved fossils indicate Bothriolepis had lungs, which would allow it to feed on the muddy shorelines, eating food well out of the reach of most of its contemporaries.
Bothriolepis is distantly related to the gigantic Dunkleosteus. It was much much smaller, averaging 12 inches (~30 cm) long. Like its apex predatory cousin, and the rest of its placoderm kin, all species of Bothriolepis were extinct by the end of the devonian.
these things are making me really uncomfortable and I have no idea why