Article: Panderodus from the Waukesha Lagerstätte of Wisconsin, USA: a primitive macrophagous vertebrate predator

Conodonts are an extinct group of early vertebrates. Articulated fossils of their feeding apparatus (‘natural assemblages’) are rare, and preserved soft tissues vanishingly so. Here, a primitive conodont with preserved soft tissues is redescribed from the Waukesha Lagerstätte of Wisconsin, USA. Although the feeding apparatus of derived prioniodontid conodonts is well understood, together with the homologies between taxa, the same is not true of more primitive conodonts that have apparatuses composed entirely of coniform elements. The new data provide insights into the long-term problem of determining homology across different types of conodont feeding apparatus. The Waukesha Panderodus preserves an almost complete apparatus, consisting of two parallel rows of elements that occluded across the sagittal plane. A pair of M elements lies at the rostral end of the apparatus, with four pairs of S elements located immediately caudal to them. Three pairs of P elements are identified at the caudal end of the apparatus, for the first time in a primitive conodont with coniform elements. A symmetrical S₀ element is located on the midline between the M–S and P suites and provides the key for establishing homology with more derived ramiform–pectiniform apparatuses. The exceptional preservation reveals cartilaginous supports for the elements that inserted into their basal cavities. The trunk of the animal is poorly preserved but was dorsoventrally flattened in life with transverse myomeres containing muscle fibrils. Overall, the specimen shows that Panderodus was a macrophagous feeder and provides an insight into the functional anatomy of early vertebrate predation.

Carrie Eaton (University of Wisconsin Geology Museum) is thanked for her assistance in locating and loaning the Waukesha specimen, and Dr Thomas Davies (University of Bristol) for assistance with XTM scanning. Ivan Sansom (University of Birmingham) and Emilia Jarochowska (FAU Erlangen-Nuremberg) provided perceptive and detailed reviews that greatly improved the clarity and accuracy of the manuscript.