Fossils B/C

c21k
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Re: Fossils B/C

Postby c21k » March 31st, 2019, 4:01 pm

Does anyone have advice on how to differentiate between cross sections of Nummulites vs Fusulinids
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Re: Fossils B/C

Postby wec01 » March 31st, 2019, 4:23 pm

c21k wrote:Does anyone have advice on how to differentiate between cross sections of Nummulites vs Fusulinids

You shouldn't really have to worry about that; I rarely see cross sections so if you see something circular it's Nummulites and if it's elliptical/grain-shaped it's Fusulinida.

If they do give a cross section though, I guess the individual rings for Nummulites look more regular and uniform in thickness while Fusulinida has rings that are more bumpy. Not sure if that's a legitimate difference or a good way of describing it, but in general I'd say Nummulites cross sections are all very similar and recognizable, so once you can identify those you can just assume things that don't look like Nummulites are Fusulinida.
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Re: Fossils B/C

Postby Unome » March 31st, 2019, 4:52 pm

wec01 wrote:
c21k wrote:Does anyone have advice on how to differentiate between cross sections of Nummulites vs Fusulinids

You shouldn't really have to worry about that; I rarely see cross sections so if you see something circular it's Nummulites and if it's elliptical/grain-shaped it's Fusulinida.

If they do give a cross section though, I guess the individual rings for Nummulites look more regular and uniform in thickness while Fusulinida has rings that are more bumpy. Not sure if that's a legitimate difference or a good way of describing it, but in general I'd say Nummulites cross sections are all very similar and recognizable, so once you can identify those you can just assume things that don't look like Nummulites are Fusulinida.

I wrote a question with a cross-section of a fusulinid for a recent test.
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Re: Fossils B/C

Postby Rock&Roll92 » April 4th, 2019, 3:25 pm

How do you guys differentiate between trilobites when they're in a ball. The only thing i'm using is the color of the trilobite atm as for example eldredgeops is normally a darker color, and calymene lighter. Obviously, it isn't working well, but with pictures most of the trilobite isn't visible.
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Re: Fossils B/C

Postby UTF-8 U+6211 U+662F » April 4th, 2019, 5:01 pm

Rock&Roll92 wrote:How do you guys differentiate between trilobites when they're in a ball. The only thing i'm using is the color of the trilobite atm as for example eldredgeops is normally a darker color, and calymene lighter. Obviously, it isn't working well, but with pictures most of the trilobite isn't visible.

There are a number of features that are different, e.g. size, the laces, what the eyes look like, the shape of the body, etc. I wouldn't rely on the color of the specimen because that only depends on what rock it's fossilized in, which can vary.

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Re: Fossils B/C

Postby wec01 » April 4th, 2019, 5:15 pm

UTF-8 U+6211 U+662F wrote:
Rock&Roll92 wrote:How do you guys differentiate between trilobites when they're in a ball. The only thing i'm using is the color of the trilobite atm as for example eldredgeops is normally a darker color, and calymene lighter. Obviously, it isn't working well, but with pictures most of the trilobite isn't visible.

There are a number of features that are different, e.g. size, the laces, what the eyes look like, the shape of the body, etc. I wouldn't rely on the color of the specimen because that only depends on what rock it's fossilized in, which can vary.

Yeah, for me I try to look for the eyes first as they are easy to distinguish between calymene and eldredgeops (the other trilobites are less likely to be enrolled). If you can't see the eyes, the segments and some other body parts are shaped slightly differently, and you may be able to use them to identify it. If you want to use the rock to help, calymene seems to be more likely to have matrix still between the ridges resulting in a less finished/polished look, but that's very unreliable/inconsistent (it's just a matter of preparation of the fossil) and I wouldn't use this as the sole basis for identification.
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Re: Fossils B/C

Postby BennyTheJett » April 4th, 2019, 5:28 pm

wec01 wrote:
UTF-8 U+6211 U+662F wrote:
Rock&Roll92 wrote:How do you guys differentiate between trilobites when they're in a ball. The only thing i'm using is the color of the trilobite atm as for example eldredgeops is normally a darker color, and calymene lighter. Obviously, it isn't working well, but with pictures most of the trilobite isn't visible.

There are a number of features that are different, e.g. size, the laces, what the eyes look like, the shape of the body, etc. I wouldn't rely on the color of the specimen because that only depends on what rock it's fossilized in, which can vary.

Yeah, for me I try to look for the eyes first as they are easy to distinguish between calymene and eldredgeops (the other trilobites are less likely to be enrolled). If you can't see the eyes, the segments and some other body parts are shaped slightly differently, and you may be able to use them to identify it. If you want to use the rock to help, calymene seems to be more likely to have matrix still between the ridges resulting in a less finished/polished look, but that's very unreliable/inconsistent (it's just a matter of preparation of the fossil) and I wouldn't use this as the sole basis for identification.

The features of the head are quite different between the trilobites. I tried to know characteristics of each trilobite, and used that to determine the genus. However you can reliably distinguish them works.
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