Wednesday, July 8, 2020

Partial placoderm plate from the Arkona formation

I have never found much in the way of fish remains at Hungry Hollow, Ontario, but once I did find a small fragment from a bony placoderm plate.  Placoderms were early, shark like fish that had external bony armor around their heads. There are a few species known from the middle Devonian aged rocks found at Hungry Hollow (Arkona formation and Widder formation) but this is just a fragment so I doubt I could narrow the species down.

I found this piece near the base of a slope of eroded Arkona formation and could not find any trace of more uphill. You can tell it is bone due to the pale blue color (evidence of the phosphate mineral Vivianite) and the spongy structure within the piece.

Top surface - this is what would have been the outer facing portion of the bone. Note the bumps, perhaps they helped streamline the fish for swimming purposes?

Two side views of the bone showing the spongy nature.

This was the interior side of the bone

I collected this specimen from the Arkona formation which is Devonian in age, Givetian stage.

Sunday, July 5, 2020

Small sponge from the Widder formation

On a trip to the exposures of the Widder formation along the Credit river in Hungry Hollow, Ontario, I found this cluster of sponge spicules. It is not uncommon to find individual spicules like this within the Hungry Hollow member of the Widder formation, but a large cluster like this is less common. I checked the "Check List of Fossil Invertebrates Described from the Middle Devonian Rocks of the Thedford-Arkona Region of Southwestern Ontario" by Stumm and Wright (1958) and they list one sponge known from the Widder formation: Astraeospongia hamiltonensis.  I am familiar with that genus from the upper Silurian where it is known as Astraeospongia meniscus from the Brownsport formation. The spicules in my specimen look very similar to those earlier species so I think I will stick with the name Astraeospongia hamiltonensis.

I collected this specimen from the Hungry Hollow member of the Widder formation which is Devonian in age, Givetian stage.

Thursday, July 2, 2020

Mystery echinoderm from the Verulam formation

Below are some pictures of a mystery Echinoderm from the Verulam/Bobcaygeon formation. I am not entirely sure of the formation this comes from as it was found in an area that was close to the boundary of the two units.

It was found a couple of years ago and cleaned by an expert but there it not much there to go on. I posted these images to a group on Facebook that is frequented by knowledgeable people who have collected for many years from the Verulam and Bobcaygeon formation. The only possibility that was suggested was that it could have been part of the central body of a starfish. The presence of many small plates does make it seem like an echinoderm and starfish have lots of small plates as part of their bodies so I think this is as close as I'll be able to get to figuring out just what this was. For reference, the fossil is about the size of a US quarter.

I collected this fossil in 2017 at the James Dick quarry near Gamebridge, Ontario. The Verulam and Bobcaygeon formation is late Ordovician in age, Katian/Mohawkian stage.

Monday, June 29, 2020

Ceraurus globulobatus Trilobite from the Verulam formation

I've mentioned before that I don't often have luck with finding Trilobites, well the specimen below is a definite exception to the rule. It's a Ceraurus globulobatus from the Verulam formation. I found it a few years back and a friend, M.T., did the prep work to clean it up. It's not a perfect specimen but it's darn nice. The glabella is slightly crushed and one of the tail spines is missing as well as a small section of shell from the end of the thorax. All in all though, it's a large fossil and a species I never had before.

It is a very flat specimen so perhaps more evolved to swim in the water column?

The eyes are fairly well preserved and not crushed. I am not able to see any lenses though.

Here is what it looked like before it was cleaned up.

I collected this fossil in 2017 at the James Dick quarry near Gamebridge, Ontario. The Verulam formation is late Ordovician in age, Katian/Mohawkian stage.

Friday, June 26, 2020

Cupulocrinus jewetti crinoid from the Bobcaygeon Fm.

This is a partial Crinoid from the Bobcaygeon formation in Gamebridge, Ontario, Canada. I found it a few years ago on a field trip and a friend, Malcolm, cleaned it up for me. The crinoid is named Cupulocrinus jewetti and this is a pretty good example. The stem and some arms are missing but otherwise it is a decent specimen.  It is one of the few articulated crinoid specimens that I have found myself.

The Bobcaygeon formation is Ordovician in age (late Ordovician, Katian/Mohawkian stage).
I used William Hessin's book "South Central Ontario Fossils", 2009, Self Published, pg. 244 to help identify this fossil.