Crescent-shaped fossils (possibly trilobite?)

[Emthegem]

Hello!

I recently decide to split a fossil that seemed to have the edge of a shell poking out. To my surprise, it split open to reveal something I have never seen before in all my years hunting in Toronto. I thought perhaps it might have been the head of an unusual trilobite, but I am not convinced for sure. 

 

It was found on the riverside deposits of Etobicoke creek in Toronto, Canada, which is part of the Georgian Bay formation. Let me know what you guys think @Malcolmt @Monica @JUAN EMMANUEL:

 

[Emthegem]

here are some more photos:

[piranha]

Isotelus hypostome:

 

 

Rudkin, D.M., Tripp, R.P. 1989
The Type Species of the Ordovician Trilobite Genus Isotelus: I. gigas Dekay, 1824.
Royal Ontario Museum, Life Sciences Contributions, 152:1-18  PDF LINK

[Malcolmt]

Definitely an isotelus hypostome

[Emthegem]

44 minutes ago, piranha said:

Isotelus hypostome:

 

 

Rudkin, D.M., Tripp, R.P. 1989
The Type Species of the Ordovician Trilobite Genus Isotelus: I. gigas Dekay, 1824.
Royal Ontario Museum, Life Sciences Contributions, 152:1-18  PDF LINK

 

4 minutes ago, Malcolmt said:

Definitely an isotelus hypostome

 

Wow sweet! Do they usually get split from the rest of the body like this one or are they usually found intact with the rest?

[connorp]

8 minutes ago, Emthegem said:

Do they usually get split from the rest of the body like this one or are they usually found intact with the rest?

They are usually found isolated (although I can't comment specifically on this formation). Hypostomes are one of the less common Isotelus bits to find, but complete Isotelus are quite rare in most places.

[Huntonia]

Nice hypostome! 

[Malcolmt]

On isotelus they are almost always found separate when the bug is ventral. 

[FossilNerd]

Very nice Em! A Conulariida  one day and now an Isotelus hypostome. You are on a roll!  
 

[Tidgy's Dad]

Great find! 

[Emthegem]

2 hours ago, Huntonia said:

Nice hypostome! 

Thanks! This is a first for me so I'm proud to have a new piece in my collection.

 

1 hour ago, FossilNerd said:

Very nice Em! A Conulariida  one day and now an Isotelus hypostome. You are on a roll! 

Thanks, you can say that again! Technically, I found the hypostome a while back in the beginning of the summer, and only a small edge was exposed. I was confident it was going to be a really good quality Pholadomorpha pholadiformis - but I was incredibly confused and very excited when the rock split and I saw this embedded in it. 

 

1 hour ago, Tidgy's Dad said:

Great find! 

Thanks! 

 

2 hours ago, connorp said:

They are usually found isolated (although I can't comment specifically on this formation). Hypostomes are one of the less common Isotelus bits to find, but complete Isotelus are quite rare in most places.

2 hours ago, Malcolmt said:

On isotelus they are almost always found separate when the bug is ventral. 

Okay good to know! I've found partial pieces all over the place, but they are usually so heavily embedded in veeeerrryyyy hard rock :/. I actually talked to someone (6 feet away of course) at one of the sites I went to the other day and they had a huuuge chunk of what looked to be an Isotelus thorax - I personally have never found anything nearly as complete as what they had. I don't think they knew how rare their piece was either - they thought it was a nautiloid at first.

[JUAN EMMANUEL]

On 7/6/2020 at 10:22 PM, Emthegem said:

Thanks! This is a first for me so I'm proud to have a new piece in my collection.

 

Thanks, you can say that again! Technically, I found the hypostome a while back in the beginning of the summer, and only a small edge was exposed. I was confident it was going to be a really good quality Pholadomorpha pholadiformis - but I was incredibly confused and very excited when the rock split and I saw this embedded in it. 

 

Thanks! 

 

Okay good to know! I've found partial pieces all over the place, but they are usually so heavily embedded in veeeerrryyyy hard rock :/. I actually talked to someone (6 feet away of course) at one of the sites I went to the other day and they had a huuuge chunk of what looked to be an Isotelus thorax - I personally have never found anything nearly as complete as what they had. I don't think they knew how rare their piece was either - they thought it was a nautiloid at first.

How big was the thoraic fragment? Very nice hypostome. 

The persom wasnt digging the thoraic fragment from the shale was he? That's how I managed to find some of my partial specimens. 

[Ludwigia]

Good find and found not all that often. I only have one plus an imprint from the Ordovician at Gamebridge.

[Emthegem]

9 hours ago, JUAN EMMANUEL said:

How big was the thoraic fragment? Very nice hypostome. 

The persom wasnt digging the thoraic fragment from the shale was he? That's how I managed to find some of my partial specimens. 

Thanks you! I don't think it was 100% complete as it seemed that it had broken off and was slightly weathered around the edges and whatnot, but despite that it was probably about 10-15 cm by 10 cm. They were there with their kids and I believe they just found it resting in the rocks (it did look like shale I believe).

 

8 hours ago, Ludwigia said:

Good find and found not all that often. I only have one plus an imprint from the Ordovician at Gamebridge.

Thanks, and good to know! I'm happy I finally have some pieces that are somewhat uncommon in my collection