Tabulate Corals - mound shaped
Tabulate corals are colonial corals. The entire tabular coral is called the corallum, while the individual tubular chambers within the corallum are called corallites. While solitary forms of rugose corals were made up of a single corallum with large, cup-shaped calices (cups), most tabulate corals had a large corallum comprised of a colony of corallites (sometimes thousands) with very small calices in which the actual coral animals (polyps) lived. Although the individual coral polyps were generally smaller than their rugose cousins, their colonies often grew to much larger sizes. These types of coral mounds were the reef formers of the Silurian and Devonian seas.
The individual corallite chambers contain thin plates called tabulae (TAB-yu-lee in English, or tah-BOO-lye in classic Latin), which extend across the chambers. The tabulae are what this order of corals are named for. All tabulate corals have tabulae, but they are only obvious in fossils, when the sides or insides of the fossils are exposed. The tabulae are stacked within each corallite, and define successive living chambers of the coral polyp, as it grew. As each coral polyp grew it abandoned its old living compartment and secreted a new skeletal tabula above the old one resulting in the stacked living chambers seen in fossils.
A common types of mound-shaped colonial tabulate coral found in Kentucky is Favosites. These corals commonly form mounds several inches, to several feet in diameter. In the detail on the right, a large favostid mound is exposed in cross section and the corallite (tubular chambers) are exposed. These examples are from the Falls of the Ohio, but similar corals are found in other Paleozoic strata as well.
Favistella stellata (Hall)
This small Favistella coral was found in Ordovician strata. The close-up photograph shows the shape and arrangement of corralites (holes), in which the coral animals (polyps) lived when the coral was alive. The scale on the picture to the left is in centimeters. Collected by Gabe Jones, an amateur collector, in Lexington. Identified by Alan Goldstein.
Favosites hemisphericus is a specific species of Favosites coral. It commonly grew in hamhock-shaped mounds in which the pointy or thin end of the hamhock shape was attached to the sea bottom and the rounded end of the hamhock was upright. Each of the tiny holes (corallites) on the outside of the coral mound were where coral polyps grew when the coral was alive. This specimen is from the Devonian-age Jeffersonville Limestone at the Falls of the Ohio and was pictured in Greb and others, 1993, Fig. 19c, p. 18.
Favosites turbinatus (Billings)
Favosites turbinatus is a specific species of Favosites coral. This coral was given it's name because of the turban-shape of the coral when viewed from the top. Each of the tiny holes (corallites) on the outside of the coral mound were where coral polyps grew when the coral was alive. This specimen is from the Devonian-age Jeffersonville Limestone and is 12 cm across (from Greb and others, 1993, Fig. 19b, p.18). Identification by Alan Goldstein.
Favosites turbinatus (Billings)
This is another example of Favosites turbinatus, a type of tabulate, colonial coral. The specimen on the left is oriented as it would have been in life, with the bottom attached to the sea floor, and the turbon-shaped top pointing upward. The picture on the right is a slice through the sample, which reveals the individual corallite chambers beneath the holes seen in the picture on the left. Each chamber is divided into segments by thin plates, called tabulae, from which tabulate corals get their name. Identification by Alan Goldstein.
Emmonsia is another type of tabulate coral mound common in the Jeffersonville Limestone (Devonian) at the Falls of the Ohio. Most often, this coral occurs as branching shapes, but sometimes it forms mounds several feet across (The camera lens can be used for scale in this example). Emmonsia can be differentiated from Favosites by looking closely at side views or cross sections through the corallites (tubes) within the coral. The corallites of Emmonsia are very thin, almost like hairs and small pores can be seen in the walls. In addition, Emmonsia has tongue-shaped projections that extend from the walls, projections that Favosites do not have. Emmonsia is considered a subgenus of Favosites by several coral paleontologists. Some information was provided by Alan Goldstein.