Since Herman Melville penned his novel Moby Dick more than 150 years ago, scientists have been fascinated by the remarkable attributes of the sperm whale and its kin - the smaller pygmy and dwarf whales. Now, fossils from an extinct pygmy sperm whale that died seven million years ago, have shed new light on the evolution of modern day whales. The remains, which were discovered in Panama, indicate that the organ involved in sound generation and echolocation got smaller throughout the whale’s evolution. Fossils from an extinct pygmy sperm whale that died seven million years ago have shed new light on the evolution of modern day whales. This image shows the right lateral view of the skull of Nanokogia isthmia . Although why this is so remains a mystery. While many whales, dolphins and porpoises have a long fossil record, enabling scientists to understand their evolution, there is limited evidence of sperm whales and smaller pygmy and dwarf whales, which are capable of navigating the ocean deep underwater. Now an international team of scientists, led by the Natural History Museum of Los Angeles County has discovered a new species of extinct pygmy sperm whale, called Nanokogia isthmia, which clarifies key aspects of the evolution of these  animals. The  well-preserved skulls of two individuals were unearthed at a sea cliff along the Caribbean coast of Panama. The find will help experts fill in gaps in the evolution of cetaceans. This is the evolutionary tree of sperm whales showing links between extinct and living species, and when the spermaceti organ changed shape . The remains, which were discovered in Panama, indicate that the bone involved in sound generation and echolocation got smaller throughout the evolution of the sperm whale. In contrast modern sperm whales (a stock image is shown) are much larger than their extinct relatives . The sperm whale is the largest of the toothed whales and the largest toothed predator. It's only one of three living species in the sperm whale family, along with the pygmy sperm whale and dwarf sperm whale. Mature males reach an average length of 52 ft (16 metres) with their head making up one third of their length. They mostly dine on squid and swim to depths of 7,380 FT (2,250 metres) to hunt for prey. They are the second deepest diving mammal, following only Cuvier's beaked whale. The sperm whale's clicking vocalisation - a form of echolocation and communication - can be as loud as 230 decibels underwater, making it the loudest sound produced by any animal. It has the largest brain of any animal on Earth, more than five times heavier than a human's and can live for more than 60 years. It reveals an unexpected level of complexity in the evolution of the spermaceti, which is an organ located within the head that plays a key role in the generation of sound and in the whale’s capacity for echolocation. The study, published in the journal Plos One, shows that at one time small sperm whales measuring  around seven feet (two metres in length) had a much larger spermaceti organ relative to their size than  modern day relatives. It got downsized at least twice during their evolutionary history, including the evolutionary event that gave origin to the living pygmy and dwarf sperm whales. Lead researcher Dr Jorge Velez-Juarbe said: ‘The new discovery gives us a better understanding of the ancient distribution of these poorly known relatives of the sperm whale. ‘Previously we knew of similarly-aged pygmy and dwarf whales from Baja California and Peru, but this new fossil fills in an important geographic gap in the group’s ancient distribution.’ He added: 'Our study is part of a larger scientific effort aimed at understanding the changes in the marine habitats that resulted from the complete closure of the Isthmus of Panama,' referring to the separation between the eastern Pacific Ocean and the Caribbean Sea that took place sometime within the last 10 million years. The new fossil is known from the well-preserved skulls of two individuals which were unearthed at a sea cliff along the Caribbean coast of Panama, shown on this map . The fossils show that at one time small sperm whales measuring  around seven feet (two metres in length) had a much larger spermaceti organ relative to their size. A dorsal view of the fossilised skull is shown .
Team of scientists discovered new species of extinct pygmy sperm whale . Seven million-year-old Nanokogia isthmia bones were found in Panama . Suggest the bone involved in sound generation and echolocation got smaller throughout the whale’s evolution . Today's larger sperm whales are able to navigate under water with ease .