Our Ears Once Breathed?
Helen Pearson
Nature
Our ears could have started evolutionary life as a tube for breathing, say scientists, after examining the ancestral structure in a 370-million-year-old fossil fish.
The bony structures in ancient fish, which at some point turned into ears appear to have had mainly a structural function, bracing the cheek and holding up the jaw. How exactly they made the transition to their role in hearing has proved a bit of a mystery.
Martin Brazeau and Per Ahlberg of Uppsala University in Sweden decided to take a close look at the ear-like features of an ancient, metre-long monster from the Latvian Natural History Museum in Riga.
Panderichthys was a fish, but is thought to be closely related to the earliest four-limbed tetrapods that eventually climbed on to land and gave rise to modern vertebrates.The researchers examined Panderichthys and found that the bony structures in its head combine features of fish and tetrapods, capturing a snapshot of evolution in action.
Ancient fish have a narrow channel from the roof of the skull into the mouth, known as a spiracle, which is bounded by a long bone known as the hyomandibula that braces the cheek.The team found that Panderichthys has a wide, straight spiracle rather than a narrow one, and a shortened hyomandibula.
The team speculates that the widened spiracle may have served Panderichthys much like the breathing holes used by modern-day sharks and rays. These allow the fish to inhale water over their gills while lying on the seabed, and avoid gulping in grit through the mouth.
Jan 18, 2006
Helen Pearson
Nature
Our ears could have started evolutionary life as a tube for breathing, say scientists, after examining the ancestral structure in a 370-million-year-old fossil fish.
The bony structures in ancient fish, which at some point turned into ears appear to have had mainly a structural function, bracing the cheek and holding up the jaw. How exactly they made the transition to their role in hearing has proved a bit of a mystery.
Martin Brazeau and Per Ahlberg of Uppsala University in Sweden decided to take a close look at the ear-like features of an ancient, metre-long monster from the Latvian Natural History Museum in Riga.
Panderichthys was a fish, but is thought to be closely related to the earliest four-limbed tetrapods that eventually climbed on to land and gave rise to modern vertebrates.The researchers examined Panderichthys and found that the bony structures in its head combine features of fish and tetrapods, capturing a snapshot of evolution in action.
Ancient fish have a narrow channel from the roof of the skull into the mouth, known as a spiracle, which is bounded by a long bone known as the hyomandibula that braces the cheek.The team found that Panderichthys has a wide, straight spiracle rather than a narrow one, and a shortened hyomandibula.
The team speculates that the widened spiracle may have served Panderichthys much like the breathing holes used by modern-day sharks and rays. These allow the fish to inhale water over their gills while lying on the seabed, and avoid gulping in grit through the mouth.
Jan 18, 2006
