Page 384 - Introduction to Paleobiology and The Fossil Record

ECDYSOZOA: ARTHROPODS 371

(a) (b) (c) (d)

Pelagic Illaenimorph

(e) (f) (g) (h)

Marginal cephalic spines Olenimorph

(i) (j) (k) (l)

Pitted fringe Miniaturization Atheloptic
Figure 14.8 Trilobite ecomorphs: pelagic (a, b), illaenomorph (c, d), marginal cephalic spines (e, f),
olenimorph (g, h), pitted fringe (i), miniature (j, k) and atheloptic (blind) (l) morphotypes. (Based on
Fortey & Owens 1990.)

high-latitude Selenopeltis province (Gond- bonate, illaenid–cheirurid communities appar-
wana). Despite a number of modifi cations, ently lasted the longest.
this basic pattern is generally accepted (see Trilobites (such as Choubertella and

also Chapter 2). Schmidtiellus) first appeared in the Early
Some Early Paleozoic trilobite communities Cambrian and the group survived until the
may also be interpreted as showing an end of the Permian, when the last genera, such
onshore–offshore spectrum, from shallow- as Pseudophillipsia, disappeared (Fig. 14.11).
water illaenid–cheirurid associations to deep- In a history of 350 million years, the basic
water olenid communities (Fig. 14.10). In body plan was essentially unchanged, but
general terms, the shallow-water, pure car- many modifi cations promoted trilobite