Conodonts and Microvertebrates

Conodonts are tooth-like phosphatic microfossils of an extinct early vertebrate, prized as some of the finest index fossils of the Paleozoic and Triassic.

Definition

Conodonts are microscopic phosphatic elements that formed feeding apparatuses in an extinct eel-shaped chordate; microvertebrates are isolated small vertebrate hard parts studied as microfossils.

Scope

This topic covers conodont elements, their phosphatic composition, apparatus reconstruction, and the soft-bodied animal that bore them, as well as other microvertebrate remains such as fish scales and teeth (ichthyoliths) used in micropaleontology.

Core questions

• What kind of animal made conodont elements?
• How are conodont apparatuses reconstructed from isolated elements?
• Why are conodonts such valuable index and thermal-maturity fossils?
• How are other microvertebrate remains used in stratigraphy?

Key concepts

• Phosphatic elements and apparatuses
• Conodont animal affinity
• Color alteration index
• Microvertebrate ichthyoliths

Key theories

Conodont animal affinity

Rare soft-tissue fossils show that conodont elements belonged to a small chordate, resolving a long-standing question about the maker of these fossils.

Conodont color alteration index

Progressive color change in conodont elements with heating provides a widely used index of the thermal maturity and burial history of host rocks.

Clinical relevance

Conodonts provide high-resolution biostratigraphy for much of the Paleozoic and Triassic and define several stage boundaries, while their color alteration index is a practical tool for assessing the thermal maturity of hydrocarbon source rocks.

History

Conodonts were described as enigmatic microfossils from 1856 and long debated as to their biological nature. The discovery of fossilized conodont animals in the 1980s confirmed their chordate, likely vertebrate, affinity.

Debates

Vertebrate status of conodonts

Whether conodonts are true vertebrates or stem chordates, and the homology of their tissues, continues to be discussed.

Key figures

• Walter C. Sweet
• Richard Aldridge
• Klaus Muller

Seminal works

• sweet1988
• armstrong2005

Frequently asked questions

What animal did conodonts come from?

Conodont elements were the hard feeding parts of a small, eel-shaped early chordate, likely an early vertebrate, known from rare soft-bodied fossils.

Why are conodonts useful besides dating rocks?

Their color changes predictably with heating, so geologists use a conodont color alteration index to estimate how hot rocks became during burial.