Platycystites cystoid from Oklahoma

Platycystites is a strange echinoderm from the Ordovician. It belongs to a class known as Paracrinoids and is thought to have sat upright in the sediments with arms spread out via a thin ridge running across the body. Here is an artists rendering (that I found at the AccessScience website) with Platycrinites on the left.

Next are a couple of specimens from my collection.Note the ridge along the top of the first two pictures. The stem attachment point is on the middle right in the first picture (just below my thumb).

A view of the stem attachment point.

A second specimen that is a little more crushed.

There are several species of Platycystites listed as being known from the Bromide formation. The only good pictures I can find online are here from the Iowa Digital Library. Based on their pics I'm inclined to label these specimens as Platycystites infundus.

The Bromide formation is upper Ordovician in age (Blackriverian [N. American stages] or Sandbian [ICS stages]). The above specimens came from the Mountain Lake Member of the Bromide formation and were found in the 1970's near Davis, Oklahoma.

Rafinesquina brachiopod from the Martinsburg formation

When visiting rock and fossil shows or shops I always keep and eye out for items from Pennsylvania. Swatara Gap material especially so since that is a now closed site and I only collected there once or twice as a child.

This plate caught my eye because of the large, detailed Rafinesquina brachiopod. It is preserved in a very fine grained sandstone (or sandy mudstone).

Here is another that I collected years ago from the site.

Swatara Gap was a well known collecting site up until about ten years ago when the Pennsylvania Department of Transportation buried the site to prevent undercutting of I-81. The Martinsburg formation is dated to the late Ordovician (Katian stage or Tentonian to Edenian of N. America stages)

Taeniaster spinosus starfish from Pennsylvania

This is a piece of mudstone from the Martinsburg formation at Swatara Gap, PA with parts of a fossil starfish called Taeniaster spinosus.

Swatara Gap was a well known collecting site up until about ten years ago when the Pennsylvania Department of Transportation buried the site to prevent undercutting of I-81. The Martinsburg formation is dated to the late Ordovician (Katian stage or Tentonian to Edenian of N. America stages)

Three Ordovician Crinoids from Canada

A few years ago I bought some Crinoids from a dealer on e-bay. I've since lost the labels but remember that they all came from Canada and were from the Verulam or Bobcaygeon formations. I sent pictures of the specimens to my friend Joe since he is very familiar with the fauna of those two formations. Here is what he suggests:

Daedalocrinus or possibly Cupulocrinus

Isotomocrinus 

Daedalocrinus (lying on some other crinoid's scattered plates... maybe Carabocrinus?)

I welcome any other ideas or suggestions.

Hexagonaria alpenensis from Michigan

Hexagonaria is a common colonial rugose coral in the middle Devonian. It's also the source of the "Petosky stones" that one sees for sale or can find on the beaches of northern Michigan. Here is a typical example of a "Petosky stone" in the unpolished state.

This stone was cut but not polished to show the coral pattern that is hidden inside.

When you wet it you can see the coral pattern more clearly. Often these stones are polished and used for decoration.

The piece above had been washed and naturally tumbled by the surf of Lake Huron. Here is very good example of what a small intact colony looks like without the tumbling.

The underside show the wrinkled epitheca surface where it contacted the muddy bottom nicely.

I'm not sure which formation any of the above specimens came from. The "Petosky stones" were beach float while the colony was unlabelled save for "Michigan, Devonian". They all most likely originate in the middle Devonian (Givetian stage).

Ptychodus teeth from Texas

Ptychodus was a genus of shell crushing sharks that lived during the Cretaceous. Like all sharks they are best known from their teeth since much of their skeleton is made from cartilage rather than bone. Since they crushed shells rather than rend flesh their teeth were more flattened like a modern ray or skate. Here is a link, to a page on the Oceans of Kansas website with more information on these sharks and pictures of articulated sets of teeth.

This is a tooth from a Ptychodus whipplei that was found in the Atco formation (Cretaceous, Santonian stage)near Prosper Texas.

This smaller tooth is from a different species called P. anonymous. It came from the Arcadia Park formation (Cretaceous, Turonian stage) near Dallas Texas.

Both of these fossils were among a group that I won on  Fossil Forum site. Thanks to Travis for sending me these shark teeth.

A couple of Decapods from the Brittion Fm. of Texas

Decapods is another name for crabs and their kin. Here I have two partial crab fossils from the Britton formation (Cretaceous, Turonian stage) of Texas.

The first fossil is Cenomanicarcinus vaelstrani from near Little Elm

The second fossil is a Notopocorystes dichious from near Las Colinas

I received both specimens from an auction that I won on the Fossil Forum site. Thanks to Travis for sending me these crab fossils.

Exogyra costata from Texas

I immediately recognized this next shell when I first unwrapped it from the parcel it came in. It belongs to the genus Exogyra and likely is the species E. costata. It comes from the Corsicana formation (Cretaceous, Maastrichtian stage) near San Antonio, Texas. It looks very similar to E. costata shells found in the Navesink thru Mt. Laurel formations ( also Cretaceous, Maastrichtian stage) of New Jersey and Delaware like this one.

Left valve top

Right side profile

Anterior

Left side profile

Posterior

Interior of left valve. It still has a slight mother of pearl sheen to the interior!

I received this in a batch of fossils that I won in an auction on the Fossil Forum site. Thanks, Travis, for the cool fossil!