Page 320 - Introduction to Paleobiology and The Fossil Record
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SPIRALIANS 1: LOPHOPHORATES 307
(a)
(b)
Figure 12.8 Teeth of articulated brachiopods: (a) deltidiodont and (b) cyrtomatodont dentition.
The brachiopods experienced fi ve main Not unexpectedly, the end-Permian mass
extinction events followed by recoveries and extinction saw the demise of over 90% of
radiations of varying magnitudes. The end- brachiopod species, including some of the
Ordovician event occurred in two phases most ecologically and taxonomically diverse
against a background of glaciation and groups. The post-extinction fauna was fi rst
accounted for the loss of almost 80% of bra- dominated by a variety of disaster taxa (see
chiopod families. The recovery and subse- p. 179), including lingulids; nevertheless the
quent radiation is marked by the decline of brachiopod fauna later diversifi ed within a
deltidiodont groups such as the orthides and relatively few clades dominated by the rhyn-
strophomenides, whereas the spire-bearing chonellides and terebratulides. The end-Trias-
atrypides, athyridides and the spiriferides sic event removed the majority of the remaining
with cyrtomatodont dentition (Fig. 12.8), spiriferides and the last strophomenides. The
together with the pentamerides, achieved agenda set by the end-Permian event, involv-
greater dominance, particularly in carbonate ing the subsequent dominance of rhynchonel-
environments. Late Devonian events, at the lide and terebratulide groups, was continued
Frasnian–Famennian Stage boundary, were after the end-Triassic event. The end-Creta-
also associated with climate change and ceous event may have been responsible for the
removed the atrypides and pentamerides and loss of about 70% of chalk brachiopod faunas
severely affected the orthides and stropho- in northwest Europe; nevertheless, many
menides, whereas the spiriferides and genera survived to diversify again in the
rhynchonellides survived in deeper-water Danian limestones. Despite the post-Permian
environments and staged an impressive recov- decline of the phylum, Modern brachiopods
ery. A particular feature of the post-Frasnian exhibit a remarkable range of adaptations
fauna was the diversity of recumbent brachio- based on a simple body plan and a well-
pod megaguilds (see p. 91), dominated by the defined role in the fi xed, low-level benthos.
productides. The Carboniferous and particu-
larly the Permian were intervals of spectacular
experimentation: some brachiopods mim- Ecology: life on the seabed
icked corals or developed extravagant clusters Living and fossil brachiopods have developed
of spines while a number of groups reduced a wide range of lifestyles (Fig. 12.9). Most
their shells, thus presenting soft tissues to the were attached by a pedicle cemented to a hard
outside environment. substrate or rooted into soft sediment. A
