Stephanocrinus - Case of the Triangular Stem

Over the last year or so while collecting fossils in the Silurian period Waldron Shale of Indiana, I have encountered pea size fossils.  These little flower bud looking fossils have one unique characteristic that makes them stand out.  The base of the fossil has an almost equilateral triangle shape. How often do you see this type of shape in organic creatures?

Early paleonotology studies done by George Greene (1894-1906) of New Albany, Indiana and James Hall (1878-1891) of New York noted this triangular shape.  No explanation given as to why the creature evolved this way.  It was thought to be crinoid but has characteristics of a blastoid.

In 1962, Robert Fay of the Oklahoma Geological Survey published a paper Ventral Structures of Stephanocrinus angulatus showing the crinoid belonged in the order of Coronata.  Fossils in this order had be identified as crinoids, blastoids and even cystoids.  He notes the characteristics of the order are: "All have three basal plates, with the azygous one in the right interior interradial position, five radials and five interradials that extend into coronal processes, and an anal opening on the adoral side of the coronal process at the junction of two adjacent radial limbs with the anal interradial. High ridges, in the form of pore-rhombs, extend at right angles to the sutures on the sides of the calyx, giving the appearance of a pore-rhomb cystoid. These ridges are superficial and are not extended in depth."

Dr. Carlton Brett of the University of Cincinnati did research of Rochester Shale (similar to Waldron Shale) fossils in which he comments on the Stephanocrinus in the 1981 book Colossal Cataract" The Geologic History of Niagara Falls edited by Irving Tesmer.   "The elongate, pyramidal thecae of this genus are among the most abundant echinoderm remains in the bryozoan-rich layers of the lower Rochester shale. Stephanocrinus possesses prong-like structures at the top of the theca and rather tiny coiled armlets. The stem, which is rarely preserved, was relatively short and attached by pad-like structure at its lower end."  He goes to say that maybe this an early version of a blastoid found later in the period.

In 2002, it was classified as a

See Stephanocrinus fossils else where on the Internet:

Stephanocrinus angulatus of the Rochester Shale

The New York Geological Survey web site showing it as a blastoid.  That is a nice image of a specimen!

Stephanocrinus documented in Naubug Beds of Kashmir

Fluorescent Uranium Glass Marbles

These unique glass marbles contain a small amount of the isotope uranium-238. When exposed to ultraviolet (UV) light, the uranium's electrons in a low energy state move to an excited energy state that emits a greenish light. Uranium 238 is a naturally occuring isotope that has been used as glass coloring (uranium oxide) for almost 2000 years. In ancient Roman ruins dating back to around 80 A.D., a yellow glass mosaic was found that contained uranium oxide. Two marbles in this set are different types. An approximate 1 inch in diameter marble that is cream colored opaque marble with a few minor indentations. This type of marble material might also be referred to as carnival or vaseline glass. The smaller marble is more transparent with a light green tone. It is very bright green under longwave UV light. The pictures taken of the marbles include one under 30W fluorescent lighting and the other under UV LED flashlight (longwave ultraviolet - 395 nm). The marbles should glow under blacklight bulbs as well.

Similar marbles are for sale for a low price! You can buy uranium marbles here on eBay:

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Next picture is of two other marbles both of clear uranium glass and underlit by UV light.

Unidentified Ammonite

A mineral collector asked me to look at this ammonite fossil he had in his collection.  He could not remember where he had acquired it which is problematic for identification.  I was wondering if anyone has any ideas how I might identify this.  I was guessing it is from Texas and maybe Cretaceous.  It has a pearl like finish on the visible shell.  The other side of the plate is pictured showing a light brown matrix the fossil is embedded in.

The fossil is about 7 inches wide.

UPDATE (2022): My cousin ended up buying this fossil and prepped it some more revealing more fossil details. https://louisvillefossils.blogspot.com/2022/02/what-genus-is-this-ammonite-fossil.html