The Arthropod That Can't Get Any Respect

[jkfoam]

The Ostracod (Class Ostracoda) is a very small bivalved crustacean that is very important as an index fossil in identifying stratigraphic units. Petroleum Geologist use them and Foraminifera taken from oil well drilling debris to know where they are stratigraphically. However, most of us amateur fossil collectors ignore completely the Ostracod. They are too small, generally too featureless, and you need expensive equipment even to see them. Typically, an Ostracod is less that a couple of millimeters in length. Heck, I've got Forams in my collection that are larger than a two bit piece.

Well, the other day I was going through some bulk micro fossil material I had collected from the Texas Eocene, Cook Mountain Formation in Brazos County and Houston County. I came across an Ostracod that is making me rethink my attitude about collecting Ostracods. While this Ostracod is highly ornimented and a handsome fossil indeed, it is quite small, only about 0.2 mm on the long axis. So far I have identified its taxonomy as follows;

Phylum Arthropoda

Subphylum Crustacea

Class Ostracoda

Order Podocopida

Superfamily Cytheroidea

Family Trachyleberididae

Genus Cythereis

specie ?

I'm still looking for the proper reference to get a specie identification. I think I need to contact someone at the U. of Houston Geology Dept. There is a hotbed of Ostracod activity there. (LOL)

Here are a couple of photos of the Ostracod I found. I apologize for the quality of the photos, they were taken through my microscope at 40X and I really need to get a better quality microscope camera.

JKFoam

[JohnJ]

Jim, does that thing really have a "rim" of spines on both ends?

[fig rocks]

I will have to look at some of my core samples that I have to see if I have some of those fossils. These cores have come from old oil wells somewhere in Alberta

[jkfoam]

Jim, does that thing really have a "rim" of spines on both ends?

JohnJ

Yeah, it does look like that but I think they are more prominent on the posterior end. (there is some debate on what is the posterior end of an ostracod) LOL

JKFoam

[JohnJ]

JohnJ

Yeah, it does look like that but I think they are more prominent on the posterior end. (there is some debate on what is the posterior end of an ostracod) LOL

JKFoam

I'll bet there is.

[Bill]

Nice specimens. I have a few Cretaceous and Pliocene ones from the UK. I've not id'd them yet though.

Cretaceous, Wealden. The top right is a different sp.

Pliocene, Red Crag. 2 sp. again.

[Roz]

Jk, I love those but being that small guess I would not

find any.

Bill are yours that tiny too? Awesome creatures.

[JohnJ]

Roz, we probably find them all the time. They just get washed away when we are cleaning the big stuff.

[PaleoPutz]

I have read about small stuff like that while reading about Oklahoma trilobites. I haven't got the microscope out to look for them yet. A very interesting specimen you have there though.

[Bill]

Hi Roz, yes they're tiny. I can't get to them at the moment but they're a mm or 2 in length, if that.

[PaleoPutz]

I just noticed something as I was replying... Are they arthropods? I have read about them being found with them, but I didn't think they were... I thought they had to have legs. I would be far from a voice of authority though.

Edited January 7, 2010 by PaleoPutz

[Bill]

They are basically tiny 'shrimp-like' critters, with a bivalve shell.

Apparently, the male genitalia is, compared to the size of the whole animal, the largest in the animal world.

See here for images and sketches of the critter with one valve removed.

Edited January 7, 2010 by Bill

[Bear]

Here is one from Hungry Hollow in Ontario. It is maybe 1 - 1.5 mm, Devonian (I believe). It is on the back of a disarticulated Greenops pygidium plate.

Ponderodictya punctulifera

[PaleoPutz]

They are basically tiny 'shrimp-like' critters, with a bivalve shell.

Apparently, the male genitalia is, compared to the size of the whole animal, the largest in the animal world.

See here for images and sketches of the critter with one valve removed.

Ah, cool.... ya learn something every day. Thanks for the link.

[Placoderms]

For those that have access to Geology, check out Figure 2 Item C in this article: http://geology.gsapubs.org/content/37/10/907.short

There is cooler stuff still to be published on Ostracods

I like the Ostracods from the Chengjiang:

http://www2.le.ac.uk/departments/geology/images/djsbrachipod.jpg/view

[Acryzona]

JKFoam, I don't know the species of your ostracod but have seen similar in some Cretaceous samples from TX.

As far as ostracods from Oklahoma, there are plenty in washings I have from the Haragan and Henryhouse formations. A nice addition to my collection. As a general comment, I find that older (Devonian / Silurian) ostracods are not as ornate as younger (Cretaceous, Paleocene etc.) I'm still amazed of the preservation of fine spines on some of the Cretaceous critters in my collection!

Acryzona

[jkfoam]

Acryozona,

The Genus I assigned my specimen to, Cythereis, ranged from the late Cretaceous to present. Generally that genus is pretty ornate and spiny. And I think I agree with you that the Cenozoic Ostracods are more ornate than the early ones. That said some of the Cenozoic ones can be pretty nondescript.

Ostracods are pretty amazing. I read somewhere that Ostracods are currently one of the largest animal biomasses on earth, second only to copepods, another even more minute arthropod.

JKFoam

[Foram-Mike]

just another ostracod

[jkfoam]

Foram-Mike,

The contrast, depth-of-field and focus is amazing with your electrom microscope photos. Umm, I wonder if I could talk the wife in to letting me buy an electron microscope. Umm, I'd probably have to buy a divorce as an accessory though.

JKFoam

[Blastoid]

Ostracods are collectible by the millions at Arkona, Ontario. Simply bring home a bucket of the nice grey clay and spend a great deal of time breaking it down, soaking and rinsing repeatedly in water. The very fine-grained remains will be primarily minute tentaculites and ostracods. Conodonts are a real prize; also bits of brachs and the odd tiny gastropod, but 99.9% tentaculites and ostracods. An inteesting record that suggests very long periods of very dull times. Beautiful, interesting, and curious little fossils, surprisingly ornamented, under 2mm max, need 30x to appreciate. Superbly described and figured by Kesling & Chilman.

Blastoid

[Northern Sharks]

Blastoid:

Welcome to the forum. Where in Ontario are you and where do you mainly hunt? There are a few other locals on here as well

[Blastoid]

Hiya Northern;

I'm 15 minutes from Arkona. Not a fanatical fossil guy, more into minerals, but god help me if I had the money I'd be a fanatic all right. Love Devonian things, love trilobites, any fossil from Ontario, and lately into Green River fish.

Blastoid

Blastoid:

Welcome to the forum. Where in Ontario are you and where do you mainly hunt? There are a few other locals on here as well

[pleecan]

Ostracods are collectible by the millions at Arkona, Ontario. Simply bring home a bucket of the nice grey clay and spend a great deal of time breaking it down, soaking and rinsing repeatedly in water. The very fine-grained remains will be primarily minute tentaculites and ostracods. Conodonts are a real prize; also bits of brachs and the odd tiny gastropod, but 99.9% tentaculites and ostracods. An inteesting record that suggests very long periods of very dull times. Beautiful, interesting, and curious little fossils, surprisingly ornamented, under 2mm max, need 30x to appreciate. Superbly described and figured by Kesling & Chilman.

Blastoid

Now you got my interest.... I took some Arkona clay let sit in water for 2 days... poured the slurry through a 50 mesh screen and looked at the screen under a microscope and wow... a new alien world.

[JimB88]

There are some large (by ostracod standards) ones in the middle Ordovician (Platville group) of N. Illinois that were close to 1/2 inch in size.

[Rumi]

Ostracods are indeed fascinating creatures, and not as hard to collect and study as one might think. You need magnification, obviously, and a binocular stereo microscope is the way to go. These can be had on E-bay for less than $150, probably cheaper if you get one used. Some that are being offered on E-Bay at very reasonable prices, less than $200, come with a USB camera so you can see the images on your computer monitor.

Literature for identifying your finds is not hard to come by, either. Volume Q of the Treatise on Invertebrate Paleontology, 1961, is still the standard (although a bit out of date): 411 pages of text and drawings illustrating every genus known as of the publication date. I just bought one used at Amazon.com for $6.39, including shipping!! (Also a used copy of Cushman's basic work on forams, last edition, for $13.) This is a really beautiful book, IMHO, the drawings are superb, explanations of ostracod morphology are clear and simple, a good glossary, charts of the distribution of each genus through time, etc., etc. Once you know the genus to which a specimen belongs, an internet search will often turn up leads to a specific ID.

Microfossils are really abundant wherever there are sedimentary rocks, and they require very little effort to collect. As for the more recent ostracods being more "ornate" than those of the Paleozoic: I beg to differ. Check out the family Beyrichiidae (peaked in the Silurian), or the genus Rakverella in the Piretellidae (Ordovician): marvelous structures!

Rumi