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Wooster’s Fossil of the Week: A new crinoid genus from the Silurian of Estonia
It is my pleasure to introduce a new Silurian crinoid genus and species: Velocrinus coniculus Ausich, Wilson & Vinn, 2015. The image above is a CD-interray lateral view of the calyx (or head), with the small anal plate in the middle-top. (This will make more sense below.) The scale bar is 2.0 mm, so this is a small fossil. It was captured by the Crinoid Master himself (my friend and colleague Bill Ausich) from the Middle Äigu Beds of the Kaugatuma Formation (Upper Silurian, Pridoli) at the Kaugatuma Cliffs of Saaremaa Island, Estonia. It is described in the latest issue of the Journal of Paleontology. Here’s a link to the abstract. (This is the first issue produced by Cambridge University Press, so we’re honored to be part of publishing history.)
Here is another view of the calyx, this time looking laterally at the E-ray.
This figure explains the calyx views we see above. It is a plate diagram of Velocrinus coniculus. Imagine it as what the crinoid would look like if we could separate all its preserved ossicles and lay them out. The radial plates are black; the anal plate is shown stippled and marked with an “X”; the other letters indicate the particular rays. The artwork, and the images above, are from Bill Ausich.
The genus Velocrinus is defined this way in the paper: “Crotalocrinitid with a calyx cone shaped, lacking stereomic overgrowths, comprised of relatively large plates; infrabasals not fused, visible in lateral view; two anal plates; primaxil minute, not visible in lateral view; fixed brachials present; free arms not laterally linked; anus on tegmen; (nature of tegmen plating unknown).” This certainly is opaque to most readers. Trust us — it separates this new genus from all described before. Velocrinus is derived from the Latin term velo, which means to cover or conceal (think “veil”). It refers to the tiny primibrachials, which are not visible in lateral view. The species name coniculus refers to the cone-shaped calyx.
Velocrinus coniculus is known only from the Kaugatuma Cliffs locality on Saaremaa Island. This is one of my favorite outcrops in Estonia. The extensive bedding-plane exposures are rare in the region. They show hundreds of holdfasts (essentially roots) of crinoids, some very large. The deposit was a relatively high-energy carbonate sand shifting through a forest of tall crinoids rooted in the sediment. Palmer Shonk (’10) did an excellent Senior Independent Study with rocks and fossils we collected from this place. The site shown above, by the way, was the location of a Soviet amphibious landing in November 1944.
This is a close look at a bedding plane of Middle Äigu Beds of the Kaugatuma Formation. The crinoid stems are robust and abundant. Oddly enough, we’re still not sure what genus is represented by the large stems and holdfasts. The calyx of Velocrinus coniculus is far too small to have been associated with them. I suppose this means we need another expedition to Estonia!
References:
Ausich, W.I., Wilson, M.A. and Vinn, O, 2012. Crinoids from the Silurian of western Estonia. Acta Palaeontologica Polonica 57: 613–631.
Ausich, W.I., Wilson, M.A. and Vinn, O, 2015. Wenlock and Pridoli (Silurian) crinoids from Saaremaa, western Estonia (Phylum Echinodermata). Journal of Paleontology 89: 72-81.
Source: http://woostergeologists.scotblogs.wooster.edu/2015/03/13/woosters-fossil-of-the-week-a-new-crinoid-genus-from-the-silurian-of-estonia/
