Age:??Mississippian

Formation:??Burlington
Location:??Ralls County, Missouri

The Burlington Formation contains more species of crinoids than any other stratigraphic unit in the world

This crinoid has large, stellate plates on the cup and very small, smoother plates on the tegmen. The anal opening of the crinoid is quite evident. The arm attachment areas around the periphery are easily seen.?

Usually, crinoids from this formation are found only as calyces. It is unusual to find this crinoid with an articulated stem. It is also unusual to find an Uperocrinus with an anal tube as long as this one.

The crinoid in the middle of the plate is Dorycrinus unicornis. The smooth-plated crinoid at the bottom is Platycrinites sp. Both of these crinoids exhibit the arm attachment points. All three crinoids display good plate structure. There is also THREE fine Cryptoblastus melo blastoids on the plate.

Although these two crinoids look very different, they belong to the same genus, based upon the plate structure. The specimen on the left is Uperocrinus aequibrachiatus. This crinoid has a very lobed appearance. The specimen on the right is Uperocrinus pyriformis. This crinoid has a much longer cup.?

Rare find. There are very few complete crinoids found in the Burlington. This specimen even has a nice length of stem attached. （2.7 inches with stem）

On the left is a wonderful specimen of Uperocrinus nashvillae. This crinoid is only found in the uppermost layers of the Upper Burlington Formation. The crinoid is extremely 3-dimensional and exhibits fine detail. The rugose plates of the calyx are beautifully displayed and the arm attachment points are easily seen. A Pentremites elongatus is on the right side of the slab. This is one of the earliest known species of Pentremites. The wide ambulacra of this robust blastoid are clearly defined.?

There are two crinoids, five blastoids (two different types), and an unusual bryozoan on this slab. On the left side of the plate is a wonderful example of Cactocrinus multibrachiatus. This crinoid has a large stellate-plated cup and a tegmen composed of numerous, protuberant plates. The long anal tube is unusually well preserved and the arm attachment points are easily seen. On the right side of the plate are two specimens of Orophocrinus stelliformis. These highly uncommon, star-shaped blastoids are highly prized by the local collectors and to have two examples on the same plate is very rare indeed. There are also three Cryptoblastus melo on the plate. These melon-shaped blastoids exhibit fine detail - the thin ambulacra are easily seen. In the extreme lower left of the limestone block is a strange bryozoan, Evactinopora sp., that looks somewhat like a starfish. Lying between the large Orophocrinus and the center Cryptoblastus is an example of Steganocrinus. This crinoid shows the stem attachment point.?

Cryptoblastus?隱海蕾屬

Platycrinites?寬發(fā)蓋海百合屬

bryozoan 苔蘚蟲類

Systematic revisions to?Aorocrinus, Dorycrinus, Macrocrinus, Paradichocrinus, Strotocrinus, and?Uperocrinus: Mississippian camerate crinoids (Echinodermata) from the stratotype region

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