Page 445 - Introduction to Paleobiology and The Fossil Record

432 INTRODUCTION TO PALEOBIOLOGY AND THE FOSSIL RECORD

posterior anterior anterior
posterior

basal cavity
basal cavity
Hertzina Furnishina
(a) (b)
anterior posterior posterior main cusp
main cusp anterior
anterior
blade denticles denticles
basal
posterior cavity
blade
basal cavity Prioniodina
Ozarkodina

posterior
posterior
platform platform
carina

basal cavity
secondary
platforms
lateral
process
blade inner side outer side
blade
anterior anterior
Polygnathus Amorphognathus
(c)
Figure 16.3 Descriptive morphology of the main types of conodont elements: (a) protoconodont
Herzina (×40); (b) paraconodont Furnishina (×40); and (c) euconodonts Ozarkodina (×40), Prionodina
(×20), Polygnathus (×40) and Amorphognathus (×40). (Based on Armstrong & Brasier 2004.)

Paraconodonts are reported from the Mid wide variety of blades and platforms in the
Cambrian; older records are doubtful. During Mid to Late Ordovician. This great diversity
the Late Cambrian, simple conical eucon- of forms was wiped out by the Late Ordovi-
odonts appeared. In the Early Ordovician, cian mass extinction (see p. 169). Silurian
apparatuses with coniforms, and some with faunas are less variable, mainly apparatuses
coniform and ramiform element types, with ramiform and pectiniform elements. The
appeared. Conodont diversity peaked during conodonts again radiated during the Late
the Mid Ordovician, with a global maximum Devonian, with specialized ramiform and pec-
of over 60 genera. During this interval of tiniform elements; over 1000 conodont taxa
experimentation, there was a huge diversity have been named from the Upper Devonian.
of apparatus patterns never again matched; Carboniferous conodonts (Fig. 16.5a) were
later apparatuses are relatively uniform, characterized by a lack of coniform elements,
perhaps indicating stabilization of feeding together with pectiniform elements in the P
modes. Pectiniform elements were common apparatus position, whereas ramiform ele-
from the Early Ordovician, together with a ments occupied the M and S positions (see