The Burgess Shale - Fossil Ecosystems of North America: A Guide to the Sites and their Extraordinary Biotas - page 36

32 33 34

32 Reconstruction of Vauxia. 33 Reconstruction of

Thaumaptilon.

34 The priapulid worm Ottoia
prolifica, showing anterior proboscis
with spines USNM. Diameter
<10 mm 0.4 in.

ThaumaptilonPhylum Cnidaria;
Order Pennatulacea
A rare constituent of the sessile Burgess
fauna, this possible sea pen ( 33 ) is none-
theless important as it is a survivor of the
Precambrian Ediacara fauna (Chapter 2),
resembling the genus Charnia (see 22 ). It
has a broad central axis with up to 40
branches, each housing hundreds of
individual star-like polyps (see Conway
Morris, 1993).

35

OttoiaPhylum Priapulida
This is the most abundant of the mud-
dwelling priapulid worms ( 34, 35 ),
especially in the higher beds of the
Burgess Shale. Priapulids are carnivorous
animals, rare today, but common in the
Cambrian seas. They had a bulbous
anterior proboscis surrounded by vicious
hooks and spines. At the end of the
proboscis is a mouth with sharp teeth;
their stomachs often reveal the last
meal, which may includes hyoliths,
brachiopods, and even other specimens
of

35 Reconstruction of Ottoia.

cannibals. They are commonly fossilized
in a U-shape, suggesting that they lived in
U-shaped burrows. However, recently
discovered straight specimens may suggest
that the U-shape was due to post-mortem
contraction (see Conway Morris, 1977a). Ottoia , for these animals were