Modern-looking lampreys ‘older’ than thought
by Michael J. Oard
Photo Wikipedia.com
Mouth of a River Lamprey
It had been assumed up until the late twentieth century that cyclostomes, living
jawless vertebrates that include the lamprey and hagfish, evolved from armoured
jawless vertebrates that supposedly lived from the Ordovician to the Devonian periods,
490 to 358 Ma within the evolutionary/uniformitarian timescale.1 Furthermore, lampreys and hagfish were supposed
to have diverged from a common ancestor sometime in the early Mesozoic about 250
Ma.2 Then lampreys and hagfish
were discovered in ‘older’ rocks from the Carboniferous period.
Just recently a lamprey was discovered from the late Devonian period, considered
360 Ma.3 This discovery
pushes back the oldest dates for lampreys by about 35 Ma. The most amazing aspect
of the new fossil is that it looks surprisingly modern, indicating little
or no change in lampreys for 360 Ma! Janvier is astonished:
‘This shows that lamprey morphology has been astonishingly stable for 360
Myr, and proves that lampreys and hagfishes had already diverged by late Devonian
times, earlier than previously thought.’
Not only does the new discovery push back the supposed evolution of both lampreys
and hagfish, but it also shows little change in all that time.
Furthermore, DNA and RNA sequence data supposedly shows that lampreys and hagfish
are ‘sister groups’, while morphological and physiological aspects tell
researchers that they evolved from different groups. Their evolution now is thought
to have occurred before the armored jawless vertebrates.4 So, there is much confusion over the supposed evolution
of cyclostomes.
Not only does the new discovery push back the supposed evolution of both lampreys
and hagfish, but also shows little change in all that time. Maybe, the
fossil record is trying to tell us that hagfish, lampreys and various armoured,
extinct fish are independent creations.
Related articles
Related resources
References
- Janvier, P., Modern look for ancient lamprey, Nature
443:921–924, 2006; p. 921. Return to text.
- Janvier, ref. 1, p. 923. Return to text.
- Gess, R.W., Coates, M.I. and Rubidge, B.S., A lamprey from
the Devonian period of South Africa, Nature 443:981–984,
2006. Return to text.
- Janvier, ref. 1, p. 924. Return to text.
Published: 14 February 2008(GMT+10)
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