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I needed to get out of the house for a few hours and so went to try my luck at finding some local Silurian fossils. First outing of the year. My first best find was this crinoid which I believe is a Eucalyptocrinites crassus calyx. A good size.

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On the reverse side is a small  Encrinurus egani.

 

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This next find I was pretty excited about. A large D. platycaudus cephalon.

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I took it home to prep...

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Unfortunately,  the preservation was not ideal, but that's the way the cookie crumbles. I placed a nicer example next to it that I found last year for comparison. 7cm across. Thanks for looking.

20210307_101323.thumb.jpg.817a225e5433ad5db3e3c5367eca855e.jpg

 

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Al Tahan

Very nice!! Is that some type is dalmanid trilobite? I hope I spelled that right lol. 

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@Al Tahan Yes, Dalmanites platycaudus. This species can get pretty big. The average size is usually 2 or 3 cm across. Still haven't found a whole one after 5 years looking. 

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Well done! Indeed, those dalmanitids could get quite large (and I haven't yet found a complete one either :( ). It's just the start of the season, so maybe this will be the year. :Luck:

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piranha

The anterior process is typically pointed on Dalmanites platycaudatus.  With the chance of a new species, I showed it to a specialist friend:

 

A:  This Sugar Run dalmanitid lacks the pointed anterior process, so I am hesitant to call it D. platycaudatus.

 

Q:  Yes, the anterior process is shorter than seems generally the case in D. platycaudatus. What appears similar is the long anterior genal field, because the front of the eye is situated relatively far back – it seems even farther back in this specimen (well behind the outer end of S3) than in the syntype cephalon of platycaudatus figured by Delo (1940, pl. 3, fig. 14). The displacement of the front of the eye from the border furrow is similar in D. limulurus but in that species the back of the eye lies farther forward and the anterior process is also longer. The length of the anterior genal field as well as that of the anterior process distinguishes the specimen from D. howelli. Of course, the length of the anterior process may vary somewhat within the species but I’m still not absolutely convinced that it is platycaudatus.

 

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Delo, D.M. 1940
Phacopid Trilobites of North America.
Geological Society of America, Special Paper, 29:1-135

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@piranha Wow - this is pretty exciting! I noticed this difference before but chalked it up to be ontogenetical differences. Now that I'm comparing different specimens from my collection, I see other differences as well, in particular, the shape of the eyes, size (all of my D. platycaudatus specimens measure about 3cm across) and the anterior process as you mentioned.  Here are some more comparisons. 

D. platycaudatus on the left and the mysterious dalmanitid on the right.

Can you send me a copy of this paper, I can't find it... Thank you!

Delo, D.M. 1940
Phacopid Trilobites of North America.
Geological Society of America, Special Paper, 29:1-135

 

dalmanitids1.jpg.523a98d8b939d5e56cc9f1d6dcc4ff5f.jpg

 

dalmanitids2eyes.jpg.13e7862855cbd72c908c9a0c3d354c6c.jpgdalmanitids3.jpg.ac5dfcaa5efee443d133c62eca0cbada.jpg

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piranha

The eyes are quite large--approximately twice the number of lenses per vertical lens file compared to D. platycaudatus. The plot thickens.. mail?url=http%3A%2F%2Fmail.yimg.com%2Fok%2Fu%2Fassets%2Fimg%2Femoticons%2Femo71.gif&t=1615227771&ymreqid=23281213-8dc1-3cff-1c02-7b0011016700&sig=_74dcuQCtfMwn4joVYTAAA--~D

 

Delo 1940 sent! 

mail-happy-smiley.gif?1292867634 check-email-smiley.gif?1292867567
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