Page 378 - Introduction to Paleobiology and The Fossil Record

ECDYSOZOA: ARTHROPODS 365

(a) (b)

(c) (d)

(e) (f)

Figure 14.2 (a–d) Parvancoria from the Ediacara biota, Flinders Ranges, South Australia;
(e, f) Skania from the Middle Cambrian of Guizhou Province, South China. Scale bar: 3.5 mm
(a), 4 mm (b), 10 mm (c, d), 2 mm (e, f). (Courtesy of Jih-Pai (Alex) Lin.)

With the exception of the agnostids and is usually a plate of between one and 30 fused
eodiscids, which have two and two to three segments. Most Cambrian trilobites have
thoracic segments, respectively, trilobites are small, micropygous pygidia, whereas later
polymeric, that is usually having up to about forms are either heteropygous, where the
40 thoracic segments. The trilobite pygidium pygidium is smaller than the cephalon,