Characiformes: Characins

Most of these species are carnivorous, and have an adipose fin as well. They tend to be similar in body shape to Cypriniformes.


This suborder contains two families, and is notable for its bicuspid teeth (similar to molars with two cusps, or raised areas).


Distichodontidae: Distichodontids

According to Nelson, there are two "groups" in this family. The first group tend to be herbivores or "micropredators," and do not have a protractile upper jaw. The other group tends to have a skinnier body, a protractile upper jaw, and feeds on the fins or entire bodies of fishes.


Citharinidae: Citharinids

These fishes have a taller body and a reduced maxilla. They are also known as lutefishes (not because of their musical abilities).


No details exist, so we're going to pretend that they all have a fear of heights.


Parodontidae: Parodontids

These fishes have a ventral mouth and feed by scraping algae off of rocks. Nelson describes them as peculiar, for unknown reasons (maybe they're kleptomaniacs).


Curimatidae: Toothless Characiforms

As you can tell by the name, they lack jaw teeth! However, these fishes utilize a tricky loophole, and maintain their pharyngeal teeth! Tricky tricky!


Prochilodontidae: Flannel-Mouth Characiforms

No, this fish isn't overly-prepared for Flannel Fridays! However, it does look like it received collagen injections, because it has overly large lips used for suction.


Anostomidae: Toothed Headstanders

Although only having a few teeth, the ones they have are enlarged. Often, the mouth is turned upwards, which is where the scientific name comes from. The second half of the common name originates from their habit of swimming with their heads down at a 45 to 90 degree angle from the bottom.


Chilodontidae: Headstanders

This family engages in similar behavior to the Anostomids, but are apparently less "toothy." The teeth are supposedly movable in the jaw. Another feature that identifies this family is that the 6th lateral line scale is much smaller than the other scales.


Crenuchidae: South American Darters

Not to be confused with the darters in Percidae, this family is distinguished by a couple minor cranial features. Make sure you know them, because they'll be on the exam.


Hemiodontidae: Hemiodontids

These fishes have a well-developed adipose eyelid and a fusiform shape. Almost all species lack teeth in the lower jaw, and most have a round spot on the midbody.


Alestiidae: African Tetras

Formerly in Characidae, this family is only found in Africa. A couple notable members:


Gasteropelecidae: Freshwater Hatchetfishes

These fishes have a similar body shape to deepwater hatchetfishes, with a compressed head and a deeply keeled body. They have long, slender pectoral fins with strong muscles, which are used to leap out of the water.


Characidae: Characins

This family is ridiculously huge, and Nelson makes it even larger by including the Serrasalmids (more recent classifications puts them in a different family, but too bad). They're so large, they don't really have any defining characters. So let's look at some individual members!


Acestrorhynchidae: Acestrorhynchids

There is only one genus, Acestrorhynchus. These fishes have elongated, pike-like bodies with small scales. They are often known as "freshwater barracudas" for their similar shape, dentition, and dietary habits. However, they only reach 40cm in length.


Cynodontidae: Dogteeth Tetras

This family is known for its well-developed canines, giving the fish a look like a two-hole punch. These fishes use their teeth to ambush and impale smaller prey. They have a long, upwards-pointing mouth, and elongated pectoral fins. Two of the largest species are the Payara (Hydrolycus scomberoides) and the Biara (Rhaphiodon vulpinus).


Erythrinidae: Trahiras

These fishes have a similar body plan to the Bowfin (Amia calva), with a cylindrical body shape, a large mouth and lack adipose fins. Some species can breathe air, and there have been reports of individuals walking on land between ponds.


Lebiasinidae: Pencil Fishes

These fishes have small, cylindrical bodies and small mouths. One species, Copeina arnoldi, is known for its unique breeding habits. The male and female gather together beneath an overlying leaf, then simultaneously leap out of the water and suction themselves together to the underside of the leaf. They will fertilize their eggs, which they then glue to the leaf. This is repeated until about 200 eggs have been laid. The male will remain to guard the eggs, occasionally leaping up to splash the eggs with water.


By Rufus46 (Own work) [CC BY-SA 3.0], via Wikimedia Commons

Ctenoluciidae: Pike-Characids

The common name comes from the similarity in body shape to pikes (Esocidae), with the dorsal and anal fins being placed posteriorly on an elongated body. They are also recognizable by their long, upturned mouth, with a slender upper jaw and a lower jaw that often has a rounded tip.


Hepsetidae: African Pikes

There is only one genus Hepsetus. These fishes do not have as elongate a body as the Ctenoluciids, but the dorsal and anal fins are still placed relatively far back on the body. They have a few large canines and some smaller teeth in their mouths. They lay their eggs in a nest of floating foam, which is highly exciting (or so I've been told).