Coleodus Archeognathus is a fossilized jaw apparatus of a large predatory conodont[2] from the Ordovician period (Darriwilian to Sandbian stages).

Its large size has made classification difficult, and it has historically been compared to conodonts and gnathostomes (jawed fish) since its remains were first discovered in Missouri.

[3] Complete articulated jaw apparatus of Archeognathus primus are common in the Winneshiek Shale lagerstätte of Iowa, allowing its identity as a conodont to be secured.

The S elements are indistinguishable from those of many species of Coleodus, a wastebasket taxon of Ordovician conodonts.

This strongly suggests that most specimens referred to Coleodus actually belong to Archeognathus.