The eldonioids are a poorly
understood Lower Palaeozoic group of non-mineralised discoidal fossils, the
best known of which is the enigmatic Eldonia ludwigi, described by
Walcott from the Burgess Shale (Lower Cambrian, British Columbia). The group is
characterised by the presence of a coiled sac, enclosing the digestive tract of
the animal, a distinguishing feature which is unique, and easily identifiable.
The paropsonemids are an even more poorly known clade within the eldonioids,
occasionally mistakenly identified as chondrophorines (‘by the wind sailors’).
These forms are distinguished by a complex ornamentation consisting of one or
more orders of radial rays interconnected by fine pitted structures. A newly
discovered site in southern Morocco has yielded 30 specimens of a new
paropsonemid eldonioid, preserved as moulds and casts within a single sand bed
of upper Ordovician age. The fossils preserve the ornamentation in fine detail,
and show the integument to have been flexible. Preservation at different levels
within the bed confirms the fossils to have been transported, however they all
appear to be preserved with the same surface facing downwards, suggesting an
element of their morphology or their environment may have exerted an overriding
control on their preserved orientation.