Eighth Edition
by Harold L. Levin

Chapter 12 - page 8

Life of the Paleozoic

What ARE conodonts?

The conodonts were previously placed in a separate phylum (Phylum Conodonta), because their affinities were unknown. The current interpretation places them with the Chordates in Phylum Chordata.

Conodont elements. Note that the color is indicative of thermal history and burial temperatures. Darker color indicates higher temperature. Temperatures are important to determine whether petroleum may have been generated in the rock, or whether temperatures were too high for petroleum to be preserved.

Name: Conodont means "cone" + "teeth" (dont)

Chief characteristics:

• Conodont elements are microfossils (fossils that are so small that you need a microscope to examine them).
  Most conodont elements are 0.5 - 1.5 mm (some up to 10 mm, and some as small as 0.1 mm).
• They are composed of a calcium phosphate variety of the mineral apatite (calcium fluorapatite).
• Individual conodont elements resemble cone-shaped teeth, or consist of bars with rows of tooth-like denticles, or irregular knobby plates called platforms.
• Each conodont element is a part of a larger organism. Most fossil occurrences are of disassociated elements, but occasionally they are found arranged in specific patterns, assemblages or "apparatuses."

Geologic range: Neoproterozoic (Late Proterozoic) to Late Triassic. Conodonts are extinct, and the organism from which they came is not known with certainty.

Significance: Useful in biostratigraphy and marine paleoenvironmental interpretation. Their color is a good indicator of the temperature to which the enclosing rock has been subjected. (This is important in determining whether oil or gas may be present in the rock.)

Mode of life: Marine, free-swimming.

     
Examples of various shapes of conodont elements.
Images courtesy of Anita Harris, U. S. Geological Survey.

What WAS the conodont animal?
Several fossils of conodont animals have been reported, but most were discredited and reinterpreted as an organism which had actually eaten the conodont animal, because the conodont elements were only in the stomach or digestive tract.

Reconstruction of the conodont animal from the Lower Carboniferous of Scotland. Note the large eye on the left.

The conodont animal is found as soft-bodied impressions. The animals lack skeletal parts except for the conodonts, which occur in the mouth region.

What were the conodont elements used for in the conodont animal?
Internal laminated structures within the conodont elements indicate that new lamellae were added on the outer surface of many elements, suggesting that they were an internal skeletal appatatus, covered with tissue, rather than being used as teeth. The function of the apparatus is not known. Some conodonts show evidence of having been broken and subsequently repaired. They may have been supports for a food-gathering apparatus.

Present evidence strongly favors chordate status for the conodont-bearing animal.