Silurian ostracod species of the Leighton Formation

[Mainefossils]

In this thread, I hope to share numerous examples of the ostracods of the Leighton Formation. As I identify them to at least genus level, if not species, I hope to post them here. If anyone has a better suggestion for the id, please let me know. 

 

First up is a cast of a left valve, female, Hemsiella maccoyianna sulcata. Length is approximately 900 microns. 

 

Literature on the subspecies:

 

Copeland, M. J. (1964) Canadian Fossil Ostracoda, Some Silurian Species. Geological Society of Canada 117. https://emrlibrary.gov.yk.ca/gsc/bulletins/117.pdf

Martinsson, A. Ostracodes of the Family Beyrichiidae from the Silurian of Gotland. https://paleoarchive.com/literature/Martinsson1962-BeyrichiidaeSilurianGotland.pdf. 

 

 

 

Edited April 13, 2021 by Mainefossils

[marguy]

I am always surprised and fascinated to see the degree of precision that can be attributed to this type of fossil (species, male or female, right or left valve, and so on ...)

Thank you for sharing

[Mainefossils]

12 minutes ago, marguy said:

I am always surprised and fascinated to see the degree of precision that can be attributed to this type of fossil (species, male or female, right or left valve, and so on ...)

Thank you for sharing

Thanks!

[Mainefossils]

Next up is a cast of a male, left valve, Hemsiella maccoyianna sulcata.

 

[Mainefossils]

Next is a cast of a male, right valve, Kloedinia wilckensiana. Length is approximately 1600 microns. First described by Jones(1886), as Beyrichia wilckensiana, moved to Kloedinia. 

 

Literature on genera and species:

Copeland, M.J. Ostracoda from the Upper Silurian Stonehouse Formation, Arisaig Nova Scotia, Canada. https://www.palass.org/sites/default/files/media/publications/palaeontology/volume_3/vol3_part1_pp93-103.pdf

Ulrich, E. O; Bassler, R. S. New American Paleozoic Ostracoda. Preliminary Revision of the Beyrichiidae, with Descriptions of New Genera. https://repository.si.edu/bitstream/handle/10088/14044/USNMP-35_1646_1908.pdf?sequence=1&isAllowed=y 

Martinsson, A. Ostracods of the Family Beyrichiidae from the Silurian of Gotland. 

https://paleoarchive.com/literature/Martinsson1962-BeyrichiidaeSilurianGotland.pdf

 

 

[Mainefossils]

Next is a pair of ostracods, both casts. On the right is a male, left valve, Kloedinia wilckensiana; and on the left, a right valve of a Zygobeyrechia, species indefinite.  Length is approximately 110 and 900 microns, respectively. If anyone has literature on Silurian Zygobeyrichia, please let me know. The literature on Zygobeyrichia is pretty sparse. 

 

Literature:

Ulrich, E.O; Bassler, R. S. (1923) American Silurian Formations: Paleozoic Ostracods: Their Morphology, Classification and Occurrence. 

 

 

 

Edited April 16, 2021 by Mainefossils

[Mainefossils]

Next is an association of three ostracods. On the top left is a male, left valve, Hemsiella maccoyianna sulcata. On the top right is a poorly preserved ostracod, possibly the same species. In the middle and bottom are my first Londinia arisaigensis, both casts of male left valves.  

 

 

Edited April 18, 2021 by Mainefossils

[Mainefossils]

Next are casts I made of the external molds of some ostracods. 

 

The external molds of the ostracods preserve more surface detail than the casts, so I made wax casts of them to see the detail better. There are two problems with this process, first, the wax is transparent, and it is slightly difficult to see the surface detail. Second, I cannot clean the casts without damaging the surface detail, so, the wax casts come out slightly dirty.

 

The cast underneath is of a male, left valve, Kloedenia wilkensiana. There are also two partial casts on the left and right of it. You can see the slight pits on the surface, but the picture does not do the specimen justice. 

 

 

 

[Fossildude19]

This is a wonderful post, and informative to boot.  

Not the kind of material we see here, regularly!

Thanks for bringing these to our attention!  

[Tidgy's Dad]

I agree.

Splendid thread.

[Mainefossils]

Thanks so much everyone! I am happy to share what I am learning with you! 

[Mainefossils]

Next is a wax cast of a Loedenia arisaigensis, a male left valve. It is complementary to the L. arisaigensis that was shown 2 posts ago. It is approximately 1500 microns long. 

 

Literature on the species:

 

Copeland, M. J. (1964) Canadian Fossil Ostracoda, Some Silurian Species. Geological Society of Canada 117. https://emrlibrary.gov.yk.ca/gsc/bulletins/117.pdf

 

 

[Mainefossils]

Next is a rather badly preserved cast of a female, right valve, L. arisaigensis. I think this might be the only female specimen of this species that I have.  Length is approximately 900 microns. 

 

[Wrangellian]

Interesting.... I too am impressed by the ability to identify such small moulds (internal or external).

I wonder if you used latex to make your casts? Also I would experiment with a thin solution of some kind of consolidant (paraloid or superglue) to strengthen the fossil first, if you can do so without obscuring the sculptural detail. Then make the cast. The latex is a little more opaque so you see a more of a solid-looking object.. and if not, you could paint it with something (again, something thin, so as not to obscure fine detail. It may not be a perfect process but with a little trial and error you should be able to refine it.)

I have done latex casts a couple times and it worked reasonably well, except I did not like that it left an oily deposit on my fossil, which is why I suggest coating it in something like Paraloid. Live and learn! Does wax leave a oily/greasy look to your fossils too?

[Mainefossils]

9 hours ago, Wrangellian said:

Interesting.... I too am impressed by the ability to identify such small moulds (internal or external).

I wonder if you used latex to make your casts? Also I would experiment with a thin solution of some kind of consolidant (paraloid or superglue) to strengthen the fossil first, if you can do so without obscuring the sculptural detail. Then make the cast. The latex is a little more opaque so you see a more of a solid-looking object.. and if not, you could paint it with something (again, something thin, so as not to obscure fine detail. It may not be a perfect process but with a little trial and error you should be able to refine it.)

I have done latex casts a couple times and it worked reasonably well, except I did not like that it left an oily deposit on my fossil, which is why I suggest coating it in something like Paraloid. Live and learn! Does wax leave a oily/greasy look to your fossils too?

Thank you!

 

I have tried using Paraloid, but, like you said, it does hide the details. Most of the ostracod fossils themselves are in a hard gray shale, which does not accept the Paraloid well. The wax I use does leave behind some residue, but it is soluble in ethanol, so I just soak them. Since the wax is so transparent, I often do use thinned out acrylic paint, but only on the second cast, that way I do not alter the first one. The pictures above are of the unpainted ones. I will look into latex, I have not used that before, and it sounds like a really good possibility. Thank you for interest and comments!

[Wrangellian]

Even a thin solution of Paraloid obscures details and doesn't spread/soak into the shale?

[Mainefossils]

19 minutes ago, Wrangellian said:

Even a thin solution of Paraloid obscures details and doesn't spread/soak into the shale?

Yes. The shale itself is very hard and impermeable, but it is also the size of the details. Some of it soaks into the shale, but because of reverse-migration, and the natural pooling of the consolidant, the pits are filled with it. 

[Mainefossils]

Next are an unidentified ostracod and two Hemsiella maccoyianna sulcata. 

 

The first is only 750 microns long. It is undoubtedly a male left valve, but I am unsure on its id. It generally resembles H. maccoyianna sulcata, but the slight pits on the surface, and the prenodal and adductorial sulcuses are too shallow. This could be due to bad preservation, but I am not sure. 

 

The second is about 1000 microns long. It is a male, right valve, H. maccoyianna sulcata. 

 

The third is about 800 microns long. It is a male, left valve, H. maccoyianna sulcata. 

 

 

 

 

[Mainefossils]

Next is a Silurian ostracod, but it is from the Eastport formation. I have included this one because it is also found in the Leighton Fm, and because this is the best preserved specimen I have seen of this species. 

 

I have not been able to identify this ostracod yet, and any suggestions would be welcome. It is approximately 2500 microns long. The first picture is from directly above it, and the second is a view from along the bottom. 

 

 

 

 

[doushantuo]

I might sleep better if you change the name of your "Kloedinia".

The scientist after whom the species is named was Kloden(kloeden with diacritic)

But: nice thread

Edited July 6, 2021 by doushantuo

[doushantuo]

Maine,you might like:

JOURNAL OF CRUSTACEAN BIOLOGY, 36(6), 841-848, 2016
COLLECTING AND PROCESSING FOSSIL OSTRACODS
David J. Horne  and David J. Siveter 
 

 

 

jcb0841.pdf

Edited July 6, 2021 by doushantuo

[Mainefossils]

9 hours ago, doushantuo said:

I might sleep better if you change the name of your "Kloedinia".

The scientist after whom the species is named was Kloden(kloeden with diacritic)

But: nice thread

I am sorry for the typo, but I am not able to edit it anymore - it has been too long. Could a moderator possibly help me out with this? 

9 hours ago, doushantuo said:

Maine,you might like:

JOURNAL OF CRUSTACEAN BIOLOGY, 36(6), 841-848, 2016
COLLECTING AND PROCESSING FOSSIL OSTRACODS
David J. Horne  and David J. Siveter 
 

 

 

jcb0841.pdf 7.77 MB · 3 downloads

I appreciate the suggestion, this could be of use next time I encounter shells that are preserved. 

Thanks for reading! 

[Mainefossils]

Hello everyone! Been a little while since I posted on this thread, but I thought that an update was in order. 

I have just read that Hemsiella maccoyiana sulcata is occasionally nearly indistinguishable from some species in the genus Sleia. So some of my identifications on this species may be faulty. 

Thanks for reading! 

 

 

 

[Mainefossils]

Okay, a little bit of an update here. Because of my recent collecting trip to the Leighton formation, I came back with some new ostracod species for my collection. My favorite is below, it is among the best spined ostracods I have. It belongs to the genus Beyrechia (=Neobeyrechia), possibly of the species B. ringerikensis. It is really hard to identify it to species, mainly because of the lack of literature, but also because of the poor preservation of my specimen. 

 

The specimen below is the cast of a right valve. 

 

Literature on the species: 

 

Henningsmoen, G. (1989) Silurian Ostracods from the Oslo Region, Norway. Norsk Geologisk Tidsskrift, 34. 

https://njg.geologi.no/images/NJG_articles/NGT_34_1_015-072.pdf

 

[Mainefossils]

Well, a new update. I have found a new little ostracod species from this formation. I am not sure on the identification, but my best guess is Cytherella concinna. Due to the lack of literature on this species I am uncertain. The genus this species belongs to is widespread, and is still extant. It is listed as being present in the Denny's formation - but the literature is so old, they seem to have not identified ostracods from any other formation. Here is the ancient article, it is shown in plate XVI, figure 30-31. 

 

The specimens are from the Leighton Formation, which is Silurian, Pridoli. Below are a few examples of this species. The first one is of an associated pair, the second image is of a separate pair, the third and fourth photos are of the external mold and cast of a single specimen. You can see the pitting on the surface of the specimens, this is one of the characteristics of this genus.

 

Thanks for reading!