What is "protoconodont"

Protoconodonts are an extinct taxonomic group of conodonts or, possibly, Chaetognaths.

Chaetognaths (also known as arrow worms) were thought possibly to be related to some of the animals grouped with the conodonts. The conodonts themselves, however, are thought to be related to the vertebrates. It is now thought that protoconodont elements (e.g., Protohertzina anabarica Missarzhevsky, 1973), are probably grasping spines of chaetognaths rather than teeth of conodonts. Previously chaetognaths in the Early Cambrian were only suspected from these protoconodont elements (for example Phakelodus), but the more recent discoveries of body fossils have confirmed their presence then.