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oldtimer

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I went looking the other day and found these star shaped Crinoids.  This rock is full of them It was located in the twins peaks limestone group of the Jurassic time.

I believe it is from the species C. Pentacrinus.  Is this correct?

5a8a16276684b_StarCrinoid1.jpg.202c5e1b777d69ffb277237d56048b2c.jpg

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I think the name is Pentacrinites now, but not sure if that is the only genus

 with star-shaped columnals. 

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They remind me of Isocrinus nicoletti columnals.

" We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. "

Thomas Mann

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Thanks Tigdy's Dad.  You may be correct.  I found the site through an older paper.

abyssunder they appear a little different than Isocrinus nicoletti but I am still open to suggestions and help.

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Location, geologycal settings, high-res images with a scale are always helpful.

 

Definitely they are not Pentacrinus or Pentacrinites ossicles, but might be Isocrinus or Chariocrinus columnals.

 

1-s2.0-S0031018208001557-gr6.jpg.e698343f9948a829d7103c58d948b681.jpg

Distribution of different crinoid groups across Middle Jurassic facies in Britain and North America (shaded). The bars signify the presence of diagnostic ossicles. Adapted from Hunter (2006).

 

" In the past, the crinoid at this locality was referred to as Pentacrinus asteriscus, a name used to describe almost all of the crinoid columnals found throughout the Jurassic of the U.S. western interior. However, systematic work indicates that the crinoid is Isocrinus nicoleti and is the first non-endemic crinoid to be reported from North American Jurassic strata. " - Tang et al., 2000

 

" Articulated Jurassic crinoids, relatively common in Europe, are rare in North America. The few that have been described are simply, and incorrectly, labeled 'Pentacrinus'. The Jurassic crinoid community of North America consequently remains poorly known. However, encrinites (rock chiefly composed of crinoid debris) are surprisingly common in North America, and represent some of the best examples of post-Paleozoic accumulations known. These rocks are highly significant for understanding the early ecology of isocrinid crinoids, and provide an insight into the wider crinoid communities of North America. A previous study of the encrinites of Utah revealed the great potential of these sediments for our understanding of crinoid palaeocommunities, however such treatment has not been applied across all of the crinoid faunas in North America. " - Hunter, 2005

 

 

 

" We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. "

Thomas Mann

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If you look at the picture below you can see how close to each other are the columnals in a general aspect, also you can choose the most appropriate to yours.

 

1-s2.0-S0031018208001557-gr4.thumb.jpg.f0c690ea1db8557b6478e8348aae31f4.jpg

Columnals showing symplectial articulations. A-B, Chariocrinus sp., Sundance Formation, Arminto, Wyoming. C-F, Isocrinus nicoleti (Desor, 1845), Carmel Formation, Mount Carmel Junction, Utah. G-I, Isocrinus aff. wyomingensis, Sundance Formation, Wyoming.

 

excerpt from A. W. Hunter, J.-P. Zonneveld. 2008. Palaeoecology of Jurassic encrinites: Reconstructing crinoid communities from the Western Interior Seaway of North America. Palaeogeography, Palaeoclimatology, Palaeoecology 263: 58-70

 

" We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. "

Thomas Mann

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Can you make a distinction between symplectial, cryptosymplectial and synostosial articular facets?

" We are not separate and independent entities, but like links in a chain, and we could not by any means be what we are without those who went before us and showed us the way. "

Thomas Mann

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