Page 295 - Introduction to Paleobiology and The Fossil Record

282 INTRODUCTION TO PALEOBIOLOGY AND THE FOSSIL RECORD

K outer wall (epitheca)
KL KL
K
K KL KL I
K I tabularium
dissepiment
II
II
L III III
C L L L L
C L
C I I
II II
(i) III H III tabula
dissepimentarium
(ii)
(a)
septal groove
operculum
calicular pit
calicular boss Calceola interseptal ridge
calice

septa fossula
transverse striation
epitheca
tabulae
calicular platform rootlet
rugose corallite
Amplexizaphrentis Palaeosmilia Omphyma
(b)
Figure 11.23 (a) Septal and tabular development in solitary rugose corals with (i) details of vertical
partitions, and (ii) details of horizontal structures. C, cardinal septa; K, counter-cardinal septa; KL,
counterlateral septa; L, alar septa. (b) Rugose coral morphology: external morphology of a variety of
solitary rugose corals. (Based on various sources.)

the heliolitids, may not even be cnidarians. Silurian tabulate coral faunas were domi-
The occurrence of fossilized polyps in Silurian nated by massive to domal Favosites with
tabulates clearly demonstrates that at least cerioid corallites, Halysites, the chain coral
some of them were corals. Only colonial or with a series of linked, long cylindrical coral-
compound growth forms evolved in this order, lites of elliptical cross section, and Heliolites,
usually with small, elongate corallites ranging the sun coral, with short, stubby septa. Simi-
from 0.5 to 5 mm in diameter. Commonly, the larly distinctive tabulates were characteristic
corallite walls are perforated by minute holes of the Devonian. Aulopora usually comprised
or mural pores. Tabulate corals fi rst appeared branching, encrusting colonies (Box 11.6),
in the Early Ordovician, probably predating similar to the bryozoan Stomatopora; the

the first rugosans. Forms such as Lichenaria extraordinary Pleurodictyum with large mural
have been recorded from Tremadocian rocks pores and thorn-like septa was virtually
in the United States, although more defi nitive always associated with the commensal worm
reports of the same genus are from the Hicetes.
Darriwilian. Tabulates such as Catenipora, Carboniferous tabulates such as Michelinia,
Paleofavosites and Propora became wide- with small colonies possessing large, massive,
spread during the later Ordovician. thick-walled corallites, and the long-ranging