AW: paleonet Fish Tails

["Klaus Ebel" <klaus@xxxxxxxxx>]

Dear Alex,

tails do not all at all provide thrust, neither upward nor downward thrust. The literature is not confused, it is not up to date. For more information about swimming locomotion and functional morphology you may visit my website www.ebel-k.de\loco1.html

Kuaus

-----Ursprüngliche Nachricht-----
Von: paleonet-owner@nhm.ac.uk [mailto:paleonet-owner@nhm.ac.uk]Im Auftrag von Alex Glass
Gesendet: Donnerstag, 23. März 2006 00:50
An: PaleoNet@nhm.ac.uk
Betreff: paleonet Fish Tails

Can someone point me to a nice RECENT summary of the functional morphology of heterocercal versus hypocercal tails in early fish?  Can someone explain to me the functional significance of why Hemicyclaspis has a heterocercal tail and Drepanaspis has a hypocercal tail when both fish are ventrally flattened and appear to have been benthic bottom-dwellers (or is that idea outdated?)?  The literature seems a little confused on this subject.  I have found seemingly contradictory claims: heterocercal tails are typical of bottom-dwelling creatures because it provides a downthrust and keeps the lower lobe from dragging through the mud, whereas as hypocercal tails (such as in Pteraspis) provides upward thrust.  If this is true why is the tail of Drepanaspis hypocercal?  Wouldn't the lower lobe drag through the mud and move the animal away from the substrate?

A confused invertebrate paleontologist who is getting frustrated with "just-so-stories"....

;) Alex

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Alexander Glass
Assistant Professor

Central Washington University
Department of Geological Sciences
400 East University Way
MS 7418
Ellensburg, WA 98926-7418
United States
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Tel: 1-509-963-2192
www.geology.cwu.edu/facstaff/glassa
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