The Bertie Waterlime - Fossil Ecosystems of North America: A Guide to the Sites and their Extraordinary Biotas - page 75

they walked on the tips of their legs
(digitigrade), bore gills, and lacked many
terrestrial adaptations. So it was quite
likely they were aquatic, like the
eurypterids (Selden and Jeram, 1989).
A new study of the Bertie scorpions by
Dunlop et al . (2007) has shown that they
all belong to one species: Proscorpius
osborni.

Ordovician Soom Shale of South Africa
(see Selden and Nudds, 2004, Chapter 3).
More recently, this record has been
extended to the Silurian Period with the
discovery of Naraoia bertiensis from the
Williamsville Formation of the Ridgemount
Quarries in Ontario (Caron et al ., 2004).
Budd (1999) described Buenaspis from
the Lower Cambrian Sirius Passet fauna of
Greenland, and also re-examined the
naraoiid-like animals, concluding that
they were better not included within the
true trilobites (e.g. Fortey, 1997) but he
resurrected an old taxon name,
Nektaspida, for these animals. Caron et al .
(2004) produced a phylogenetic analysis
of all naraoiid-like animals and concurred
with Budd. So, Nektaspida form a group of
trilobite-like animals which are
characterized by having no or very few
(maximum five, in Buenaspis ) free
thoracic segments, an uncalcified dorsal
exoskeleton, and no apparent eyes. The
extension of the range by the find of a true
Naraoia in the Bertie Waterlime shows that
these near-trilobites were in existence
far longer than previously thought and
were most likely more diverse but rarely
preserved owing to their soft exoskeleton.

Crustaceans
The phyllocarid Ceratiocaris acuminata
( 79 ) is common in the Williamsville
Formation and somewhat rarer in the
Fiddlers Green Formation of the Bertie
Waterlime. These bivalved crustaceans are
still around today, represented by only
about 40 species in three families, but have
a rich fossil record extending back to
the Middle Cambrian Burgess Shale
(Chapter 3). Characteristics of
phyllocarids include the bivalved carapace
which covers most of the body and
appendages, and a telson (tail spine)
usually with a furca attached.

Naraoia
First described from the Burgess Shale
(Chapter 3), the strange arthropod
Naraoia , with its uncalcified, two-part body
over a trilobite-like underside, has generally
been allied with the true trilobites. Since its
first discovery in the Middle Cambrian
Burgess Shale, Naraoia -like animals have
been described from the Early-Middle
Cambrian of Idaho and Utah, the Early
Cambrian Emu Bay Shale of Australia, the
Early Cambrian Chengjiang Biota of China,
the Early Cambrian of Poland, the Early
Cambrian of Sirius Passet, Greenland, the
Early Ordovician of Sardinia, and the Late

Mollusks
Nautiloid cephalopods ( 80 ) are a
characteristic element of the Eurypterus
lacustris fauna of the Williamsville
Waterlime. Both straight (orthocone) and
coiled specimens are frequently
discovered; some orthocones up to 1 m
(3.3 ft) long have been encountered.
High-spired gastropods are also common
in the Williamsville; most are very small
and usually occur in clusters.