Streetsville Trip in Mississauga, Ontario

[JUAN EMMANUEL]

Yesterday on April 24 I decided to go and visit a place in Mississauga, Ontario called Streetsville which used to be a township of its own before being joined to Mississauga to form the City of Mississauga.

I took public transportation to get there and it took me about 1.5 hrs to get there. I went to the Credit River near Streetsville and explored the banks. I had trouble finding a natural exposure as all I was finding were banks with worn out rocks and silt. The river's bottom does not have the same clarity as the Humber River in Etobicoke as I could not see the shale bottom of river. All I was seeing at the Credit's bottom were worn out rocks, algae and silt. The river was also wider than the Humber and in some places it seemed deeper as well which made me think twice about crossing to reach this natural exposure I found.

The banks mostly had worn rocks but some nice material can be found. I was surprised at the fauna I found. The rocks are still part of the Georgian Bay Formation but the fossils are completely alien to my eyes. They were nothing that I usually encounter at the Humber River or at Mimico Creek. The place was littered with small coral bits and there lots of what appeared to be Tetradium bits. There also many brachiopod hash plates around. This hash plate here has a piece of coral at the bottom along with many brachiopod bits.

There were some things familiar to me like that hash plate of bryozoans and I only found one cephalopod fragment. Where I usually hunt cephalopods are very common to find in Mimico Creek and at the Humber River.  

There were also these odd trace fossils lying around.

 

 

 

[JUAN EMMANUEL]

I decided only to take 3 specimens with me home as these were the most decent ones that I could find. I don't have their ID's confirmed yet.

Is this some sort of Tetradium?

[JUAN EMMANUEL]

A colony of something-I-don't-know. The widest part is around 2o cm.

[JUAN EMMANUEL]

 

A nice piece of coral I took home. Could be a Columnaria sp.

At the end of the day I was tired from having to carry the first 2 specimen home for another 1.5 hrs. of bus ride. This was my first time coming here and I definitely look forward to going back.

[Fruitbat]

Looks like you had a pleasant and productive trip!

 

-Joe

[Peat Burns]

Great trip report.  Thanks for posting.  Love the coral.

[FossilDAWG]

Interesting to see that corals can still be found at the Streetsville site.  I collected there in the early 1980s, and corals were abundant along the river in places.

 

Your first specimen is a Tetradium, and likely so is the second.  By the way, "Tetradium" is now considered to be a red algae, not a coral.  The name for the genus is now Prismatophyllum, as Tetradium was preoccupied.  Tetradium was OK as long as it was considered to be an animal (a coral), as the same genus name can be used for taxa in different kingdoms (such as plants vs animals).  Once Tetradium was recognized as a plant, it was found that the name had been used for a genus of trees before the name was used for the "corals", and so a different name had to be applied to the corals.  As it turned out, the name Prismatophyllum had been given to an Ordovician "Tetradium" species but was later discarded as a junior synonym.  Once "Tetradium" was invalidated, Prismatophyllum became the first valid name that had been applied to the genus, and it was resurrected.  Don't you just love taxonomy?

 

In the same vein, the genotype of Columnaria, C. sulcata, is a Devonian species with a complex internal structure including dissepiments, which are lacking in the Ordovician corals that had been called Columnaria.  This was published by Lang and Smith in 1940, but some people continued to use "Columnaria" for a long time after that.  Also in the 19th and early 20th century it seems no-one paid much attention to corals, thinking they were not very useful for stratigraphy, so essentially all the colonial corals were lumped under Columnaria.  Currently no Ordovician corals are properly assigned to Columnaria, instead they are distributed amongst several genera including Favistella, Favistina, Cyathophylloides, Paleophyllum, and Foerstephyllum, and maybe more.  The Streetsville corals are, as I recall, now called Favistina calicina (Nicholson, 1874). Besides the Columnaria issue, generic names for North American Ordovician corals were plagued with missing holotypes, types based on material from glacial erratics, and confusion about actual publication dates.  These issues led Rousseau Flower (1961, New Mexico Bureau of Mines and Mineral Resources Memoir 7) to suppress Favistella and erect the replacement genus name Favistina.

 

I also recall that Flower debated about whether to include F. calicina in Paleophyllum, because in many specimens there are some corallites that become phaceloid (not in contact with other corallites, so they form circular tubes), although the colonies start out as cerioid (corallites in contact in a solid mass, like your specimen).  F. calcina thus seems intermediate between Favistina (with cerioid growth form) and Paleophyllum (with phaceloid growth form).  However the issue was settled with the discovery of an older and better intermediate in Black River (Middle Ordovician) aged rocks, ruling out F. calicina as the branching point between Favistina and Paleophyllum.  Rather, it seems F. calicina could grow in somewhat muddy conditions, unlinke most other corals, and the phaceloid growth form was an adaptation for growing fast enough to stay above the sediment that was settling on the sea floor.  

 

Besides the abundant Favistina and Prismatophyllum, I collected some nice Calapoecia corals, and a small chain coral (Catenipora) which I have not seen otherwise reported from the Georgian Bay Formation at Streetsville.  Nearby, on Mullet Creek (at least, that is the name I recall), I found some Grewingkia canadensis solitary corals, which I have also not seen reported from that area though they do occur in the Georgian Bay up near Craigleith.  I was looking for a channel deposit that used to be exposed on the creek, that yielded several specimens of a new genus and species of crinoid, but I did not find any before I was booted from the creek by an irate landowner.  Honestly, I had no idea it was private property!

 

Don

[Nimravis]

Nice report, finds and pics. Thanks for sharing.

[Malcolmt]

Very nice , thanks for sharing. By the way I live about 5 minutes from where you were hunting. I tried there a few times but being a trilobite eurypterid  and crinoid hunter for the most part I have not been there in probably 10 years. 

[JUAN EMMANUEL]

One thing I noticed was the absence of flakes of shale on the banks. In Mimico and the Humber bits of shale are present. At this location there were mostly round pebbles.

For the Stromatocerium, did the name change the same way it did for the Prismatophyllum and the Favestina? @FossilDAWG

 

[FossilDAWG]

I don't think Stromatocerium has as complicated a nomenclatural history.  At any rate it has been in use since the 1800s and is still valid today.

 

It's been a long time, but I only recall collecting Streetsville corals from "float", loose specimens along the river banks.  I don't recall finding them in an actual outcrop.

 

Don

[Wrangellian]

Some nice specimens, I would have been tempted to take home some of those trace fossils too but I guess not if it was going to be a big effort carrying them all on foot.

BTW the small pics in your first 2 posts don't enlarge...?