Page 446 - Introduction to Paleobiology and The Fossil Record

FISHES AND BASAL TETRAPODS 433
(c)
(a) (b)
(d)
(e)
(f)
(g)
(h)
(i) (j)
Figure 16.4 Conodont elements: (a, b) coniform,
lateral view; (c, d) ramiform, lateral view;
(e) straight blade, upper view; (f) arched blade,
lateral view; (g) ramiform, posterior view; and
(h-j) platform, upper view. Magnifi cation ×20–35
for all. (Courtesy of Dick Aldridge.)
next paragraph). Conodonts became rarer
during the Early Permian, and most Late
Permian and Triassic species had small appa-
ratuses. They became extinct at the end of the
Triassic.
The first piece of evidence about the iden-
tity of the conodont animal is that the ele-
ments sometimes occur in a cluster or
apparatus consisting typically of 15 elements,
14 of them arranged bilaterally and one sym-
metric element positioned on the midline. The
elements are arranged in a particular way in
the apparatus: pectiniform (P elements) at the
back, makelliform (M elements) at the front,
and symmetry transition series (S elements) in
between. Generally bars and platforms occupy
P positions, whereas bars and cones are found
in M and S positions. The P, M and S posi-
(a)
(b)
Figure 16.5 Homing in on the conodont animal:
(a) natural assemblage of conodonts from the
Carboniferous of Illinois (×24); and (b) the
conodont animal from the Carboniferous
Granton Shrimp Bed, Edinburgh, Scotland, with
the head at left-hand end (×1.5). (Courtesy of
Dick Aldridge.)
tions may be defined more precisely with sub-
scripts, for example P a and P b elements.
The first conodont apparatus was found in
1879, and this gave some idea about the func-
tion of conodonts, perhaps as some sort of
teeth, and provided some clues about the
whole animal. Several supposed conodont
animals were identified in the 1960s, but most
of these turned out to be predatory critters
that had just eaten a conodont animal, and
so had lots of conodont elements inside
them!