The cephalic lateralis system includes 7 preopercular and 5 dentary openings. The lachrymal bone has only 3 lateralis openings. There are 6 infraorbital bones, the 3rd with a middle foramen. Astronotus species are readily identified by their general appearance, especially the long soft dorsal and anal fins and the heavy scaly sheath covering the soft unpaired fins. The colour pattern is cryptic, with a seemingly irregular pattern of light and dark blotches and stripes, and a prominent spot on the caudal fin base, encircled with a red, yellow or silvery ring.
Juveniles are black with contrasting white stripes.
The largest specimen measured so far is a 240 mm SL specimen of Astronotus crassipinnis . Etymology Astronotus refers to the ocellated spots on the dorsal fin of A. ocellatus , and is composed of the Greek words astron , star, and notos , back. Acar is the Tupi-Guarani name for cichlids, incorporated in Brazilian Portuguese. Treated as masculine in Portuguese and by the author, it retains its gender, masculine. The second word also might be gonos , borth, offspring, descendant, etc., but that interpretation seems far-fetched.