Page 356 - Introduction to Paleobiology and The Fossil Record

SPIRALIANS 2: MOLLUSKS 343

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

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

Figure 13.13 Some gastropod genera: (a) Murchisonia (Devonian) (×1.25), (b) Euomphalus
(Carboniferous) (×0.5), (c) Lophospira (Silurian) (×0.5), (d) Patella (Recent) (×1), (e) Platyceras
(Silurian) (×1), (f) Neptunea (Plio-Pleistocene) (×0.6), (g) Viviparus (Oligocene) (×0.8), and (h) Turritella
(Oligocene) (×1). (Courtesy of John Peel.)

tropods appear to comprise a unifi ed group Cenozoic, gastropods reached their acme with
derived from either advanced eogastropods or the neogastropods in particular dominating
primitive mesogastropods during the Late molluskan nektobenthos.
Mesozoic. Gastropods are not particularly good
Most Paleozoic gastropods were probably zone fossils, although nerineid gastropods are
herbivores or detritus feeders. Drill holes in stratigraphically useful in parts of the English
brachiopod shells, however, suggest that a few Middle Jurassic in the absence of ammonites.
genera were carnivores and some, such as Gastropods are generally associated with
Platyceras, were parasites. The class became particular facies and few rapidly evolving
more important during the Late Paleozoic and lineages are known in detail. Nevertheless,
the Mesozoic when many more predatory microevolutionary sequences in the genus
groups evolved. However, during the Poecilizontes from the Pleistocene of Bermuda,