Squamacula clypeata is flattened (dorsoventrally). It has 11 segments in total: the
cephalon (the head), nine thoracic
tergites (each of which covers a
somite), and one
pygidium. It has a
doublure, a piece of exoskeleton that covers part of the underside of the animal. Its doublure is, on average, about twice as long as the length of its cephalon. It has been hypothesized that this large doublure could have aided the animal in digging through sediment to find food, as it was thought to have been both a predator of small animals and a scavenger.
Squamacula clypeata has one pair of antennae attached to its cephalon, but no other appendages or auditory or visual structures. No mouth is present in the specimens, but the gut is present, so
S. clypeata must have had a mouth, which is thought to have been between the cephalon and doublure on the underside.
Squamacula clypeata has one pair of
biramous appendages (an appendage which branches into two) per thoracic tergite. The
endopod (inside branch) has seven segments, the first six of which are roughly even in size and shape, with small spines on the underside, and the last of which terminates with a claw and appears to have been used for walking and eating, as the claw could be useful in grabbing hold of and tearing up food. The exopod (outside branch) was not segmented, but flap-like, with
setae (bristles) near the tip, which may have been used for both locomotion and respiration.
S. buckorum differs from
S. clypeata in that it has 11 thoracic tergites, which appear to exhibit less overlap that those of
S. clypeata, though the differences between the two species are relatively minor. The species also preserves elements of the gut tract not preserved in
S. clypeata, which show that it was narrow annulated tube running along the midline of the animal, with three or possibly four pairs of midgut glands within the cephalic shield, with other gland pairs extending along the trunk. == Taxonomy ==