Pelican fossil poses evolutionary puzzle
17:00 22 June 2010 by Jeff Hecht
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Pelicans that closely resembled those living today were scooping fish from the water while our ancestors were still swinging from the trees, a fossil discovery suggests.
The identification of an extremely well preserved 30-million-year old fossilised beak raises interesting questions over why evolution has left the birds so little changed over such a long period.
The nearly complete beak of the 30-million-year old fossil, found in the Luberon area of south-eastern France, resembles those of the seven modern pelican species so closely that it falls within the genus Pelecanus, says Antoine Louchart of the University of Lyon, France.
Pelican beaks are the longest of any living birds. Beneath the beak is a flexible pouch that allows the birds to capture their prey in the water, then spit out the water before swallowing their meal. Like other bird beaks, they are rarely preserved as fossils, so little had been known about their early evolution.
Family resemblance
Louchart recognised the fossil, discovered in the 1980s, while examining specimens in the collection of his co-author Nicolas Tourment. Protected by being buried in fine-grained limestone, it includes most beak bones, plus parts of the skull and neck, and strongly resembles the modern great white pelican, Pelecanus onocrotalus.
The lack of evolutionary change could suggest the beak has reached an evolutionary optimum for flight or for eating. Louchart is not convinced that either of these hypotheses offers a complete explanation; he thinks something else may be involved but does not know what that might be.
The find not only pushes back the origins of pelicans, but of related birds too. “The groups now thought to be closest to pelicans, the shoebill and hamerkop, must also have differentiated very early, says Louchart.
“The pelican bill has been a successful adaptation or trait, in that it has remained very similar over time,” says Rebecca Kimball of the University of Florida. Two years ago Kimball reported in Science (DOI: 10.1126/science.1157704) that pelicans were genetically close to near relatives, which she said would reflect their slow evolution.
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