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
NIWA is the trading name of the National Institute of Water &
Atmospheric Research Ltd.
