By Science Daily
A major fossil discovery in Canada sheds new light on the development of the earliest vertebrates, including the origin of jaws, the first time this feature has been seen so early in the fossil record.
A key piece in the puzzle of the evolution of vertebrates has been identified, after the discovery of fossilised fish specimens, dating from the Cambrian period (around 505 million years old), in the Canadian Rockies. The fish, known as Metaspriggina, shows pairs of exceptionally well-preserved arches near the front of its body. The first of these pairs, closest to the head, eventually led to the evolution of jaws in vertebrates, the first time this feature has been seen so early in the fossil record.
Fish fossils from the Cambrian period are very rare and usually poorly preserved. This new discovery shows in unprecedented detail how some of the earliest vertebrates developed — the starting point of a story which led to animals such as later fish species, but also dinosaurs and mammals such as horses and even ourselves. The findings are published in the 11 June edition of the journal Nature.
Fossils of Metaspriggina were recovered from several locations including the Burgess Shale site in Canada’s Rocky Mountains, one of the richest Cambrian fossil deposits in the world. These fossils shed new light on the Cambrian ‘explosion’, a period of rapid evolution starting around 540 million years ago, when most major animal phyla originated.
Previously, only two incomplete specimens of Metaspriggina had been identified. During expeditions conducted by the Royal Ontario Museum in 2012, 44 new Burgess Shale fossils were collected near Marble Canyon in Kootenay National Park in British Columbia, which provide the basis for this study. Researchers from the University of Cambridge and the Royal Ontario Museum/University of Toronto used these fossils, along with several more specimens from the eastern United States, to reclassifyMetaspriggina as one of the first vertebrates.