Semirostrum ceruttii
March 14, 2014

Massive Underbite Of An Ancient Porpoise

Brett Smith for - Your Universe Online

Researchers from Yale University have announced the discovery of a new species of ancient porpoise with a massive underbite.

According to a report published in the journal Current Biology, the newly discovered cetacean had a jaw that extended nearly 2.8 feet – a unique feature that was probably used to probe to seafloor for something to eat, the study team said.

"The extinct porpoise is a bizarre new animal, with the mandible extending well beyond the beak-like snout, which it may have used for probing and 'skimming' in the substrate," said Rachel Racicot of Yale University. "Although this morphology has been recorded in birds and fish, this is the first described mammal with this anatomy."

The new species has been dubbed Semirostrum ceruttii – after Richard Cerutti, the collector from the San Diego Natural History Museum who found the first evidence of the creature along the California coast in 1990. Years later, an analysis of CT scans taken of the specimen revealed just how special the find was, as well as the animal’s unique morphology.

The scans revealed many details about the ancient porpoise, such as sensory structures in the lower jaw like those seen in seabirds called black skimmers, which utilize their lower jaws to feel for around food, particularly at night. The study team also found that the animal’s optic canals were smaller than those in contemporary porpoise species, an indication that the extinct animal had poor vision.

Based on an analysis of these scans, the study team concluded that Semirostrum relied on its lower jaw and echolocation abilities to find food. Using a comparative morphology analysis, the team also concluded that Semirostrum ceruttii was similar to today's freshwater river dolphins.

"Today we don't find anything resembling river dolphins in the same kinds of habitats that Semirostrum likely occupied," Racicot said, adding that the porpoises may have become more specialized over time.

The study team added that many other similar discoveries could be coming soon as modern 3-D imaging technology is making it possible to non-invasively revisit other museum specimens.

"Many exciting new species awaiting description are lying in museum collections, but the sort of detailed descriptions that are required to do full justice to them often take a lot of time," Racicot said.

In another recently published study in the international journal Geodiversitas, researchers cataloged a recently discovered cache of fossils in central California that included 21 marine mammals.

The report included a newly identified species of ancient whale, dubbed Balaenoptera berate, which existed for three to four million years.

Based on their analysis, the study team concluded that primitive porpoises and baleen whales were living alongside contemporary marine mammals such as the Northern fur seal and right whales. They also found that species far geographically and climatically removed from their modern relatives, such as beluga-like whales and tusked walruses, which today live in the Arctic.

“At the same time as this eclectic mix of ancient and modern-type marine mammals was living together, the marine mammal fauna in the North Atlantic and Southern Ocean were already in the forms we find today,” said Robert Boessenecker, a geology PhD student at New Zealand’s University of Otago, and author of the new study.