Fish with cleft lip solves evolution riddle
Michael Hopkin
Gap-toothed species shines light on nostril development.

A 395-million-year-old fish may have answered a pressing question of human
evolution: how did our nasal cavities adopt their current layout? The
strange specimen has nostrils in the middle of its upper teeth.

The fish, called Kenichthys campbelli, represents a halfway point in the
evolutionary reshuffling of the nasal passages, say Min Zhu of the Chinese
Academy of Sciences in Beijing and Per Ahlberg of Uppsala University in
Sweden, who describe the fossil in this week's Nature1. Most modern fish
have four external nostrils, whereas land vertebrates, which are descended
from Kenichthys, have nasal passages that form openings near the throat
called choanae.

Some experts suggested that choanae evolved through the gradual
repositioning of external nostrils. But sceptics countered that this would
involve the nostrils migrating through the line of the teeth, a feature not
seen in any fossil.

Full Text at Nature:
http://www.nature.com/news/2004/041101/full/041101-9.html

Posted by
Robert Karl Stonjek
---
þ RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info{at}bbsworld.com

---
 * RIMEGate(tm)V10.2áÿ* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 11/8/04 9:33:33 PM