Paraconodontida

Paraconodonts (Paraconodontida) are an extinct order of probable chordates, closely related or ancestral to euconodonts (true conodonts). The order contains the superfamily Furnishinacea, itself containing the families Westergaardodinidae and Furnishinidae.

Paraconodonts were introduced into the scientific literature by Klaus Müller, who sought out the Cambrian ancestors of conodonts through the 1950s and 1960s and proclaimed success upon the discovery of paraconodont fossils. Like early true conodonts, paraconodont elements were phosphatic fossils which generally had a horn- or tooth-like shape, and some were serrated with multiple cusps. Westergaardodina acquired an even more unusual W- or horseshoe-shaped form.

True conodont 'teeth' have a distinct crown and base tissue, with each component growing independently through the addition of external layers. In contrast, paraconodont 'teeth' have a single main component which only grows downwards via additional sheath-like layers. As a result, the tip of the 'tooth' remains fully exposed and unmodified through its entire lifetime, while the base of the 'tooth' eventually expands into a rimmed cavity.

In the earliest paraconodonts (such as Furnishina and Prooneotodus), the basal cavity is very simple and entirely lacks internal growth. Later paraconodonts are more complex: Problematoconites, for example, has 'cone-filling laminae' (very thin layers which stack up within the basal cavity), while Rotundoconus adds a spherulitic infilling (thicker beady-textured layer) below the 'cone-filling laminae'.