Orthorhachia (lit. "straight spine") is a benthic clade of Acanthopodia, analogous to bony fish on Earth.
The first Orthorhachids were anguilliform swimmers, swimming in a matter similar to eels, lampreys and some species of knifefish. The slower yet more maneuverable form of swimming led to most pelagic Orthorhachids going extinct, having been outcompeted by the faster Hadrorhachids. However, the remaining species have flourished in Anthostome reefs, which their maneuverability is more suited for.
Modern Orthorhachids have coloration designed to help them blend into their surroundings.
There are two branches of the Orthorhachid tree: