Actinocerid Perhaps?

[JUAN EMMANUEL]

I spotted this flat orthocone on a platform of limestone at a park beside the Lake Ontario. The limestone on which the fossil is set on was hauled in from Manitoba (from what I heard) and is used in many created and developed parks here in Toronto. I also heard that this limestone is Ordovician, which is kinda true judging from the fossils that I've observed on the rocks (ex. Isotelus fragements, some Ordovician strophomenids, some Favosites corals, only straight-shelled orthocones). Could it be an actinocerid and could these limestones be the ones that originate from the Tyndall limestone?

[JUAN EMMANUEL]

The limestones used when the park was developed.

Edited August 5, 2015 by JUAN EMMANUEL

[Ridgehiker]

It wouldn't be possible to ID an orthocone without examining the chambers, etc. but there's a good chance it is from that cephalopod family.

All types of neat stuff in your photo. I like looking at the matrix as much as individual specimens.

In Banff there is a hotel with Tyndall Limestone. It's probably pricey stuff so I'd guess the less quality material is surplused for projects like the parks in Toronto. Fortunately that doesn't mean less quality for fossils.

[FossilDAWG]

I am skeptical about a Manitoba source for this material. First, the lithology is unlike any Manitoba Ordovician material I have seen; in particular it is totally different from Tyndall stone, the Ordovician (Selkirk Member, Red River Formation) material quarried at Tyndall and Garson, MB. That limestone is tan colored, and full of darker colored Thalassanoides burrows. (see here for images)It is also not crinoidal at any level. There are also quarries at Stoney Mountain, but again the lithology is completely different.

Another argument would be that it makes no financial sense to quarry this rock and transport it all the way from Manitoba when rock of this nature is available and has long been quarried in Ontario.

It is hard to say much about the cephalopod without uncovering more of it. It could be an actinocerid. It'll be hard to prep given the density of the rock; it might be easier to section it lengthways, which should also reveal diagnostic features and make for an attractive specimen at the same time.

Don

[bethk]

I would agree that this rock is from Southern Ontario - it looks just like the typical Ordovician rock quarried east and northeast of Toronto (it also underlies the city), which contains lots of cephalopods, crinoids, trilobites, etc. No need to get it from anywhere else! Some of the buildings in Toronto (and I know of one in Guelph, too) are faced with Tyndal stone, but it's pretty highly prized (i.e. expensive) stuff, and therefore unlikely to be used as shoreline reinforcement.