Ordovician Heterostracan Fish Plate Or Worm Plate?

[Geodigger]

Sorry for the poor quality of this photo folks. It was scanned from an old slide picture.

It was found in residues after processing limestone for conodonts and now resides in a small vial ... so I will try to get a better pic at a later date (and don't sneeze when working with these things!). As far as microfossils go they are quite rare and less than 1 mm. They are known as Milaculum and have been variously classified under different groups over the years. This specimen is from the Upper Ordovician Verulam Formation of the abandoned Lakefield Quarry in Ontario, Canada.

Some of the older publications consider these to be the plates of a Heterostracan fish (Agnatha). Here is a link to one of these articles in PDF (Some data on Milaculum). I did a quick search on the internet for Milaculum and it appears that more recent publications consider it a palaeoscolecid worm plate (e.g. extinct type of plated priapulid worm). Here is a link to some more information of this type of classification (palaeoscolecid link).

Anyway just thought some of our Ontario fossil collectors would be interested. What are your thoughts as to what these phosphatic plates belong to? Would be nice to think they are a type of primitive Ordovician fish plate.

[pleecan]

Wow is that a neat looking fossil.... Heterostracan exists in the Silurian... may extend to Late Ordovician... ..

[Auspex]

You are really stretching my think, and I thank you

[pleecan]

You are welcome Auspex.... when it comes to fossils the impossible can some times be plausible.... as so much is not known... just waiting to be discovered....