A
tergum (Latin for "the back"; plural
terga, associated adjective
tergal) is the
dorsal portion of an
arthropod segment other than the head. The
anterior edge is called the
base and posterior edge is called the
apex or
margin. A given tergum may be divided into hardened plates or
sclerites commonly referred to as
tergites. So, for example, in a
thoracic segment, the tergum may be divided into an anterior
notum and a posterior
scutellum. Lateral extensions of a tergite are known as
paranota (Greek for "alongside the back") or
carinae (Latin for "keel"), exemplified by the so-called flat-backed millipedes of the order
Polydesmida.