''Semirostrum ceruttii'' is an extinct porpoise that lived between 5 and 1.5 million years ago (Ma), during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

is highly distinctive due to the extremely long

symphysis A symphysis (, pl. symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing togethe ...

on the

lower jaw In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

, reaching lengths of 85

centimeters 330px, Different lengths as in respect to the Electromagnetic spectrum, measured by the Metre and its deriveds scales. The Microwave are in-between 1 meter to 1 millimeter. A centimetre (international spelling) or centimeter (American spellin ...

(33.46 inches), while that of a modern porpoise are 1–2 centimeters (0.39–0.79 inches) long. The main hypothesis regarding its use is that it probed along the

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

in the murky

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environmen ...

and

shores Shores is a band from Grand Rapids, Michigan, and Minneapolis, Minnesota. The band is often described as "slowcore". Shores began as a recording project between guitarist, vocalist and bass guitarist Brian Przybylski, and drummer John Massel in s ...

of what is now

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

in search of food, which would easily be scooped up the symphysis and into the jaws. The

etymology Etymology ()The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the Phonological chan ...

of the name means "half beak", referring to the

upper jaw The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

being half the length of the lower. Semirostrum NT

References

{{Taxonbar, from=Q15958617 Pliocene cetaceans Prehistoric toothed whales Prehistoric cetacean genera Fossil taxa described in 2014 Pliocene mammals of North America Paleontology in California