These large cetaceans are usually more than 9.1 m (30 ft) long and can be found throughout the ocean. Instead of teeth, mysticetes have a series of horny plates called baleen. The baleen is made from the same materials as human hair and fingernails. The baleen plates hang from the gums of the upper jaw and are used to filter small bits of food from the water. Baleen whales have symmetrical skulls and have two (or paired) blowholes.
The mysticetes are divided into four families: rorquals (blue, humpback, minke, sei, fin, and Bryde’s whales), right whales, pygmy right whales, and gray whales. Rorquals have throat pleats, or ventral grooves, that expand when the whales gulp large amounts of water during feeding. Baleen whales can migrate up to hundreds of miles to feed in cooler areas with lots of food. On the feeding grounds baleen whales filter out small organisms from the water either by skimming the surface or gulping large quantities of water to filter. Baleen whales are not known to echolocate but produce a variety of sounds used for communication. Echoes from baleen whale vocalizations may help in navigating under ice or detecting the ocean floor.