PALEONTOLOGY STUDY GROUP MEETING
Paleontology Study Group November 18, 2000
Chairman John Good called the meeting to order and attendees introduced themselves. John said that the last Field Trip to the Field Museum went well and no more are planned now. John mentioned that Dinofest was coming up at Navy Pier from December 1, 2000 to January 7, 2001. Karen Nordquist asked if anyone was interested in participating for ESCONI in some way. She will try to find out what options there might be for us – perhaps a bulletin board where we could pass out club information. Committing to long hours manning a table may not be realistic. John mentioned a trip to Thornton Quarry (Silurian with reef formations) with Ray Wiggers. A vote was taken to determine the subject matter for the next two meetings (no recounts were accepted!!).
Future Paleontology Meetings
January 20 Burgess Shale Video
February 17 Florida fossils
MAPS meeting will be at the end of March and will be on Trilobites. This is a change to a later date and it means that we can have a Paleo meeting in March. John will be Field Trip Chairman next year and is looking for suggestions for trips. Bealis can help us get into Lone Star again. Other possibilities are St. Paul for crinoids, LeHigh for Silurian, and Larsen’s is where the kid found the starfish. There are several possibilities for a one week summer trip – Arkansas for quartz, Canada for amethyst, or Colorada where Trick Runions lives now. Jack Wittry reported that they may be plowing up part of Mazon this spring and it may be good for a trip after that.
Andy Hay then reported that the Illinois state law that said that you could not pick up fossils or minerals on state property has been set aside. It also mentions that there is no commercial collecting. This has caused some uproar, but Andy feels that it depends on what the intent of the collector is. This kind of activity can mess it up for all of us, so they should quiet down as they are lucky to be able to get in now.
FOSSIL CRINOIDS
Chris Cozart then presented our program on Crinoids (which follows the General Meeting program by Wendy Taylor last week). He began with an overview on Echinodermata, marine invertebrates, which includes crinoids. They have pentameral symmetry, a water vascular system, and tube feet. The Crinozoa subphylum also has global theca or calyx (main body), feeding appendages, and are generally stalked (some modern ones have lost the stalk). There are three major parts, crown (cup and the tegmen), stalk and holdfast. There are characteristics that separate them from other Echinoderms. They include arms instead of brachioles (like cystoids and blastoids). The arms actually have organ extensions in them and they attach to the radial plates of the calyx. The calyx plates are more uniform in arrangement than the others (except blastoids). The four groups are Camerata, Inadunata, Flexibilia and Articulata. Articulata are the only one of the four groups of crinoids alive today. Look at the cup and the arms to tell them apart. The cups are monocyclic with one circle of plates (radials and basals) or dicyclic with two layers (radials, basals and infrabasals). The arms are uniserial (stacked on top of one another) or biserial (alternating) and are pinnulate or ramulate.
The Camerata have biserial arms and are always pinnulated. The lower part of the arms are incorporated into the cup. The upper part of the calyx or tegmen is large and robust with many sutured plates. An anal tube is common. There are two groups one with 3 basals and one with 5. They lived from the Ordovician to the Permian with about 210 genera.
The Inadunata have arms attached above the radial plates. The arms are uniserial and non-pinnulate although later ones may be biserial. They are dicyclic. The second group of these are always uniserial and never pinnulate. They can be very unusual. These may have given rise to the modern crinoids. They ranged from the Ordovician to the Triassic with 480 genera.
The Flexibilia have free arms above the radial plates. The arms are uniserial and non-pinnulate and may be curled at the tips. They never have cirri. The stem below the cup may have thin stems called proxistele under the cup. They lived from the Ordovician to the Permian with about 60 genera.
The Articulata have uniserial arms and are pinnulate with the lower free arms. The tegmen is usually unplated and fleshy. There is no anal plate. The cup plating is reduced and they may be stemless. They lived from the Triassic to the Holocene with 255 genera. There are about 165 extant genera today.
The crinoids were marine filter feeders with stalks to hold them off the bottom. They lived in gregarious communities. They needed a current to bring them food and the water could not be too dirty. Some were swimmers, some were floaters and some anchored to all kinds of things from brachiopods to logs. Some also lay on the bottom. There are stems reported as long as 30 feet. The holdfast varies based on the substrates to hold onto. One is like a boat anchor for muddy bottoms. And there are some in the Devonian that hung down from a float. They don’t have a complete one with a crown yet. There is some commensalism where a gastropod or starfish may attach to part of the crinoids.
Based on the extant crinoids, the life stages start with an embryonic egg stage that floats in the water or attaches to the mom for about 5 days. The larval stage is brief from hours to a few days and is where bilateral symmetry begins. Then they go through metamorphosis to a radial symmetry in about 5 days. The stalked juvenile stage of about 6 weeks is followed by the pentacrinoid stage where the arms develop over several months. The unstalked juvenile stage lasts for several months and then the adult stage is at about I year. The life is usually about 4-5 years. They were probably more successful than other echinoderms because they exploited several levels of the water. Many of the others were restricted to the bottom. They also had more functional arms. They were preserved when quickly buried, because disarticulation after death was fast. That is why plates and pieces of stems are most commonly found. Many are found in turbidites or mud flows. To find crinoids you need to look in sedimentary rock of the right age. Marine limestones and shales are the best (avoid black shales and sandstones). They can be found in lenses of shale. Look at bedding surfaces at limestone shale contacts, residual soils and weathered shales. If you find big pieces, it is a good sign that there may be more near. Look closely because only part of it may be exposed. There may be a lot of preparation needed to find more of the animal.
Chris then showed us many fossil crinoids representing all the groups he had talked about. Some were Mississippian, Devonian, Permian, Jurassic, and Ordovician from many collecting sites including St. Louis, Ontario, Minnesota, Cincinnati and many other locations. Chris also recommended several reference books on crinoids (and other invertebrates). One was Fossil Invertebrates by Bordman.
Other members also brought fossils. Sheila and Dave Bergman had several interesting slabs; one from St. Louis Paint River Formation had 15 types of crinoids and 9 blastoids on it. A slab from Crawfordsville had about 6 crinoids on it. They also had two prepped ones from Sylvania. Dave Carlson brought 5 specimens: an Ordovician crinoid from Ontario, a Pennsylvanian one from LaSalle, and three from the Lone Star Quarry. The meeting was adjourned for refreshments and discussion.
Respectfully
Return To Home Page | Return To Paleontology Study Group
Number Of Visitors Since 2/5/2005