Conodonts represent an enigmatic group of fossils that ranged from the Late Cambrian to the Triassic (approximately 510 to 210 million years ago! ). The Russian paleontologist Christian Heinrich Pander was the first to discover conodont fossils sometime in the early 1830s. A conodont fossil itself is a minute (generally <1 mm), denticulated structure composed of calcium phosphate (a mineral substance that also permeates human bone). For the next one hundred years or so, the tremendous abundance and diversity of conodont fossils made them one of the types of fossils used for biostratigraphy (the relative dating of rocks based on the fossils they contain) and petroleum exploration. Yet it was not until the late 1950s that paleontologists began to recognize that different types of conodont fossils could originate from the same animal; much in the same way that each human individual possesses teeth of different types (for example, molars, incisors, etc.). And even more astounding was the discovery in 1983 of the first fossil of an entire conodont animal, in Carboniferous sediments (350 million years ago) of Scotland. We now believe that the conodont animal was probably a close relative of modern vertebrates, and that the conodont fossils are single elements of more complex apparatuses (each individual animal would therefore have possessed an apparatus composed of elements).

Given our rapidly increasing knowledge of conodont biology, and the excellence of the conodont fossil record, a great deal of attention is now being paid to these fossils by paleontologists interested in evolutionary theory. The present study examines, in detail, the evolutionary history of a group of Early Devonian (approximately 390 million years) conodonts, Wurmiella, from a single stratigraphic section of sediments, using a single type of element (the P1 element), from the mountains of central Nevada.

We collected samples spanning approximately 10 million years and extracted all the Wurmiella P1 elements. Next, we used image analysis and geometric description to discriminate three separate species of Wurmiella, including one new species. One of these species, Wurmiella wurmi, was particularly abundant, so we proceeded to first describe the growth and development of the elements from specific samples (and therefore specific times), and then described the mode of evolutionary change over the 10 million year interval. Perhaps surprisingly, we discovered that one part of the P1 element evolved significantly within a relatively short interval of time, while other aspects remained unchanged. Moreover, the period of significant change can be equated to changes in element development.

This study is the first of its kind to combine the excellent conodont fossil record with detailed quantitative analyses of development and evolution. As our knowledge of the conodonts and their fossil record increases, we will be able to apply this type of approach to a broader array of elements, times, and places.