Wednesday, March 4, 2015

Eurypterus lacustris from the Bertie formation

This past fall I finally found some Eurypterid fossils while visiting the Ridgemont Quarry near Stevensville, Ontario, Canada. It was my fourth or fifth trip to the quarry and previously I'd only found isolated parts of the animal. None were 100% complete but all were more than I had ever found. At the quarry the fossils are found by splitting thin bedded dolostone. The beds formed in a lagoon like habitat that was shallow and low in oxygen. Because the rock is dolomite this can be taken as evidence that the paleoenvironment was very warm with rapid evaporation. This is further reinforced by layers that have mud cracks preserved. Most of the fossils of Eurypterids that are found are molts of their exoskeleton. Depending on how quickly they became buried they would often break apart into smaller individual segments and be scattered by the currents. Thus to find any specimens of whole or nearly whole bodies is rare.

Here is the pit I was working
My finds as I had them set aside before I wrapped them up

Specimen #1 is a positive and negative of the same fossil that is just the front half of the animal. Note that the lower plate is two smaller pieces that I glued back together. This is not uncommon at the site as the dolostone is very fragmented in places with cracks from previous blasting (it is an active quarry after all).
Specimen #2 is mostly intact but has many bits and pieces scattered about. The exoskeleton may have started to disintegrate just before it was buired or the pieces are from a different exoskeleton.
Specimen #3 is the most intact with nearly the entire Teslon (the spiny tail bit) and one of the swimming arms. I have no idea what happened to the upper half of the other side. I must have lost it among the rock debris during excavation and was not able to find it.

Monday, March 2, 2015

Macraster ibizaensis echinoid from Spain

This is a nice specimen of Macraster ibizaensis from the Aptian stage of the Cretaceous near Jbiza, Spain. Thank you to my friend Karoly for the cool specimen!

Adapical surface (top)
Anterior (front)
Side profile
Posterior (rear)
Side profile
Adoral surface (underside or bottom)

Thursday, February 19, 2015

Atactotoechus fruiticosus bryozoan from the Moscow Formation

I found two little "stumps" of a bryozoan at the Deep Springs Rd. quarry in Madison County, NY. There is not too much to examine as they are fairly small but they resemble the species Atactotoechus fruiticosus. It is interesting to find these specimens as small, individual colonies and not larger, branching versions.

This first specimen is a thick, finger like piece with small monticules on the surface. The next few pictures will show different angles of it but this appears to be a single mound and was not broken off from a larger piece.

The second piece is a very small button like mound. It reminds me of Prasapora from the Ordovician.

This is the bottom of the specimen. I need to clean it off a little better to see if there is any evidence of what it attached to when it started to grow.
Top of the specimen

I have found Atactotoechus fruiticosus before in the Moscow formation at Lake Erie near 18 Mile Creek (Hamburg, NY) in the Wanakah shale of the Ludlowville formation.

Tuesday, February 17, 2015

Evidence of post mortem activity in fossil Pelecypod shells from the Panther Mountain formation

Once a hard shelled animal dies it's shell often lies around on top of the muddy bottom until it gets buried. While it is exposed it provides a hard surface for many other encrusting animals that otherwise would not be able to establish themselves. Today I have two examples of trace fossils that were left on the interior surfaces of pelecypod shells from the Devonian aged Panther Mountain formation in NY.

First up is this shell which may be an Actinodesma erectum or another species. It's hard to say for sure because along the hingeline only the wing is visible and not the ear. But that is not why I kept the piece. What caught my eye are the spider like trails that criss cross the fossil.
It's important to remember that the fossil is not composed of shell material (actual, remineralized or replace). Instead it is a cast that shows the interior surface of the shell. If it were a mold the shell would be concave and not convex like this specimen.  Getting back to the fossil, a closer look reveals what looks like cracks in the surface (which was my initial reaction). I think there is a better explanation though. These lines all join together and are sinuous in places and they also have differences in depth and width. Perhaps they are evidence of worm tubes or bryozoans that colonized the interior surface of the shell while it was exposed. It could also be evidence of a type of sponge that bored into shells and used the calcium carbonate to build it's skeleton.
 Then, off to the left side, I noticed another pattern. This one looks like a bursting firework or a flower like a Dahlia.
 A closer view shows a clear pattern and I think it is of a species of bryozoan called Paleschara incrustans. Interestingly, it appears to have over grown over one of the sinuous lines implying it colonized the shell later before it ultimately became buried.

 Another pelecypod fossil from the same locality is shown below and this one has multiple, straight and wide traces on it. 

To me these look very much like a boring clam or sponge that was digging a home within the shell of the expired clam.

Both specimens come from the Panther Mountain formation (Devonian, Givetian stage) at Cole Hill Rd. quarry in Madison county, NY.

Sunday, February 15, 2015

Hallotheca aclis hyolith from the Moscow Formation

Hyoliths are enigmatic creatures that existed from the Cambrian until the Permian. They have triangular shaped shells that are half moon shaped in cross section, an operculum that covered the head and two little horns, called helens, that protruded out from where the operculum and body met. I found a specimen of a Hyolith called Hallotheca aclis in Madison County, NY in the Moscow Formation (Devonian, Givetian stage). The view is of the ventral surface, or underside, of the shell and you can see the fine concentric growth lines.

The coolest part of this specimen is that the operculum is preserved as well and nearly articulated. It's rotated from the life position but the fact that it's even present is rare. This is the only specimen of the operculum that I've found.

The only other examples of this odd fossil that I've found have been from the Mahantango formation in PA of which a portion is roughly equivalent to the Moscow formation.