LARGE-SCALE PATTERNS IN CONODONT MORPHOLOGY: PLATFORMED PECTINIFORM (PA/P1) ELEMENTS THROUGH THE CONODONTOZOIC

The persistence of conodonts from the Cambrian–Triassic and their generally cosmopolitan distribution make them ideal index fossils for shallow water biostratigraphy of the Paleozoic and lower Mesozoic. The same characteristics also make them an ideal group for exploring broad-scale ecological and evolutionary patterns through time. This research focuses on temporal patterns in the morphology of the Pa/P₁ element, specifically the repeated appearance and disappearance of a broad, flat platform element with little to no free blade. Conodont morphologies such as this seem to be the dominant form for portions of Earth history then abruptly disappear for equally long intervals before appearing again later in the Conodontozoic. For example, species belonging to Astropentagnathus, Apsidognathus, Distomodus, Aulacognathus, and Pterosphathodus evolve and become dominant during the Late Ordovician to early Silurian, but are then decimated in a series of extinctions during the Ireviken Event. Similarly broad, flat platforms virtually disappear for the majority of the next 50 million years only to reappear in the Middle to Late Devonian with species-rich genera such as Palmatolepis, Ancyrognathus, and Klapperina. These in turn are then devastated by the end-Devonian mass extinction before yet another round of broad, flat platform-bearing groups develops during the mid-to-late Carboniferous.

Little is known about conodont life habits, but it is generally agreed upon that the organism was a nektic or nektobenthic predator, and the Pa/P₁ element likely played a role in food processing after capture. It therefore seems likely that Pa/P₁ morphology reflects prey selection and food web relationships. The major extinction levels for massive platform-bearing species occur within significant upheavals of the global carbon cycle, which provokes questions of causality. Did carbon cycle perturbations affect prey animal abundance and availability? Was climate a major driver of ecological specialization reflected by Pa/P₁ morphology? These questions cannot be addressed without first documenting the patterns and comparing them to dynamics of coeval fossil groups, focusing on putative prey taxa.