Cetacea toothed whales and two in baleen whales. The nostrils are located on top of the head above the eyes so that the rest of the body can remain submerged while surfacing for air. The back of the skull is significantly shortened and deformed. By shifting the nostrils to the top of the head, the nasal passages extend perpendicularly through the skull. The teeth or baleen in the upper jaw sit exclusively on the maxilla. The braincase is concentrated through the nasal passage to the front and is correspondingly higher, with individual cranial bones that overlap. In toothed whales, connective tissue
Rough-toothed dolphin Rough-toothed dolphin The rough-toothed dolphin ("Steno bredanensis") is a species of dolphin that can be found in deep warm and tropical waters around the world. The species was first described by Georges Cuvier in 1823. The genus name Steno, of which this species is the only member, comes from the Greek for 'narrow', referring to the animal's beak — which is a diagnostic characteristic of the species. The specific name honours van Breda, who studied Cuvier's writings. There are no recognised subspecies. The rough-toothed dolphin is a relatively large species, with adults ranging from in length, and weighing between ;