Mystery nautiloids from NY shore of Lake Ontario


TONMO Supporter
Nov 19, 2002
Can anyone identify this excellent fossil of two nautiloids?

It was found along the New York State shoreline of Lake Ontario, basically half way between Youngstown, NY and Rochester NY. (coordinates are lat. 43.37612 / long. -78.37752 ) The Buffalo Museum of Science identified it as a cephalopod probably c.420 million years old (mid. Silurian period) - Lockport formation. The stone is roughly 12 inches in width. The larger cephalopod on the right measures 4.25" in length.

They look like Orthoceras to me, though maybe they could possibly be Dawsonoceras which is also found in the Lockport?

Any advice will be forwarded on to Lawrence Fortunato who was lucky enough to find this lovely fossil. Thanks Lawrence!


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They look like orthoceras to me too. Speaking of which, I picked up a cool example at the Tucson mineral and gem show. Supposedly from the Atlas Mountains.
:smile: Nice fossils. They do have the transverse annulations of Dawsonoceras, although maybe not strong enough.
Leurocycloceras is another possibility, it has less distinct annulations than Dawsonoceras.

I cant tell if the chambers were filled with calcite by the nautiloid or if they were filled after burial. One would need a better look at the siphuncle and cameral deposits for a better ID. The third specimen (near the bottom right) seems to show the camera and the siphuncle but I cant see it well enough.

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