[Annelida] An explanation of Treptichnus trace fossils?

Geoff Read via annelida%40net.bio.net (by g.read from niwa.co.nz)
Sat Jul 31 02:05:38 EST 2010


FYI

It is said that treptichnid trace fossils  "are characterized by
subhorizontal segmented burrow systems exemplified by Treptichnus pedum
that is internationally recognized as the marker of the
Precambrian-Cambrian boundary."

And the suggestion is that the makers were ancestral priapulids:

Vannier, J.; Calandra, I.; Gaillard, C. ; Żylińska, A. 2010:  Priapulid
worms: Pioneer horizontal burrowers at the Precambrian-Cambrian
boundary.  Geology 38(8): 711-714.

http://dx.doi.org/10.1130/G30829.1

But the match is not perfect: "Major differences between the Cambrian
and the present-day seafloor may also explain the differences between
treptichnids and Recent priapulid burrows."  And: "present-day priapulid
worms such as Priapulus, by contrast with the Cambrian treptichnid
makers, do not generally produce well-defined subhorizontal burrow
systems."

Maybe some would put a question mark in the title then?  The striking
right-angle direction changes shown in the Treptichnus rectangularis
trace fossil seem especially a puzzle.

Geoff






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