“Perch-like” fish once claimed forty percent of bony species
Perciformes, meaning perch-like, is an order of ray-finned fish that includes perches, darters, sea basses, groupers and scorpionfishes. It was once thought to contain about 41 per cent of all bony fish, some 10,000 species in 160 families, before DNA studies redrew its borders.
Members range from familiar freshwater fish of temperate lakes and colourful tropical reef species to hardy extremophiles that have settled in polar waters at both ends of the planet and in the ocean’s deepest reaches. At its old size the order held more families than any other group of vertebrates.
Sorting it out took decades of argument, with families shuffled in and out depending on the study. Molecular phylogenetics largely settled matters in recent decades. Many former suborders moved to their own orders elsewhere in the wider clade Percomorpha, shrinking the group, but the traffic ran both ways: the scorpionfish order Scorpaeniformes, the stickleback group Gasterosteiformes and part of the weeverfish order were folded in.
The fossil record starts with Paleoserranus, a stem perciform from the Early Paleocene of Mexico, first taken for an early sea bass and named in 2018. Possible older relatives such as Eoserranus and Prolates come from the Maastrichtian, the last stage of the Cretaceous, though their identity is uncertain. The earliest fossils belonging to the living group date to the Early Eocene and include the scorpionfish relative Eosynanceja and flathead ear stones from New Zealand.
The current list in Eschmeyer’s Catalog of Fishes shows how broad the order still is. Alongside sea basses, fairy basslets, groupers, soapfishes and the perches and darters, it contains weeverfishes and a run of icy-water families, including cod icefishes, plunderfishes, Antarctic dragonfishes and crocodile icefishes. The former scorpaeniform side adds searobins, stonefishes, scorpionfishes, sablefishes, greenlings and sculpins, plus oddities known as racehorses, horsefishes and combfishes.
Source: Perciformes
