The Sarcosuchus skull also features a large nasal bulla, a bulbous bony growth on the end of its snout, "like a toilet bowl," jokes Sereno. The bulla appears to increase in size dramatically upon the animal's maturity.

Sereno and colleagues solicited opinions on the bulla's function from a number of reptile researchers. Bulla size seems constant throughout the Sarcosuchus sample, with no obvious differences that could be attributed to males and females, so it's unlikely to be involved in any type of sexual selection, according to Sereno. Some scientists suggested the bulla was used to improve directional smell in the stiff-necked reptiles, unable to turn their heads towards interesting scents as mammals do. The bulla may have also enhanced vocalizations.

"We're still wondering what it's for," admits Sereno. "Crocodilians are among the most vocal reptiles, so I wouldn't doubt that it may have been involved in both sound and smell."

Sarcosuchus' era on the earth was a rich time for crocodilians. The researchers have uncovered six different species of crocodilian reptiles at the Niger site, ranging from the modest to the monstrous, and including a bite-sized crocodile that Sereno describes as "not much more than an Oreo cookie" to Sarcosuchus.

"That's the fascinating thing about crocodile evolution. It seems like modern crocodiles have been trimmed at each end of their size range, with the little ones and the big ones disappearing," says Sereno.

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Contact: Lisa Onaga
lonaga@aaas.org
202-326-7088
American Association for the Advancement of Science
25-Oct-2001