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holdinghistory

Brownsport Formation, Tennessee ID Help

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holdinghistory

I had bought this piece along with a bunch of other stuff since I thought it was interesting. The guy I got it from thought it was maybe a big Trilobite pygidium, but I think not. Honestly no idea what it could be, any suggestions?

ID1.jpg

ID2.jpg

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MeargleSchmeargl

I see a little of what looks like a trilobite Pygidium, but I also see crinoid bits and bryozoa. Pretty neat piece!

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Herb

it looks like a Dalmanites sp pygidium

Dalmanites_limulurus_trilobite_silurian.jpg

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Tidgy's Dad

I agree, Dalmanites or a relative, pygidial spine and all. 

It's a nice size! 

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holdinghistory

So that little bit on the pygidial spine is part of a different fossil?

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Herb

maybe a crinoid stem and holdfast

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Paciphacops
2 hours ago, holdinghistory said:

So that little bit on the genal spine is part of a different fossil?

 

That's the Thagomizer :).

 

This is definitely a trilobite pygidium. 

The large trilobites I find in the Brownsport are Glyptambon, which do not have a spine. This one is massive! 

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Herb

might also be Huntonia sp.

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DPS Ammonite
2 hours ago, Paciphacops said:

 

That's the Thagomizer :).

 

This is definitely a trilobite pygidium. 

The large trilobites I find in the Brownsport are Glyptambon, which do not have a spine. This one is massive! 

Here's an article about the creation of the term thagomizer first mentioned in a Far Side cartoon that named caveman Thag Simmons as a victim of that weapon: http://geologyinart.blogspot.com/2010/03/thagomizer.html?m=1

 

A serious question, did trilobites use their large spine as a club?

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holdinghistory

Thanks guys!

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andyrice11

It appears as though the fossil the very tip of the pygidial spine might a fragment of a fenestra bryazoan..It looks similar to some other fragments on the matrix. Perhaps the bryazoan anchored itself to the pygidium as it sat on the sea floor. What a cool piece!

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DevonianDigger

Was this one settled as being a Dalmanites sp.? At 8 cm, that's a mighty hefty Dalmanites. I have my doubts, it seems too broad, and the attachment of the pygidial spine is more narrow. I've attached a sublimated b&w photo for additional assistance. 

 

 

image.png

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piranha

Glyptambon typically has a pygidial spine (mucro).  Apparently, this one is undescribed and quite unusual, so I sent the photo to a friend that works on dalmanitids.

 

 

Q: Which genus fits best for this large specimen?  Is it possibly Glyptambon or is it Huntoniatonia?

 

A: "Pity it’s so fragmentary!  It has narrow, sharply impressed pleural furrows similar in form to the interpleural furrows, so in that respect it is unlike Dalmanites (in a broad sense), Huntoniatonia or the other Devonian forms described by Campbell which have expanded pleural furrows and much narrower, shallow interpleural furrows.  In this respect it is more like Glyptambon, and it also resembles that genus in the axis that is poorly defined posteriorly and merges with the mucro.  In Glyptambon the posterior pleural bands become inflated distally as the anterior bands diminish in height and width, more so towards the back of the pygidium; this may be the case also in your specimen but it’s difficult to confirm it because the outer edge of the pleural region is not exposed.  Until you find more complete material you could call it Glyptambon?"

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Paciphacops

I recently visited this site. There was a lot of fresh material that had fallen from the bluff, and many large trilobite pygidia and cephalons were present. The pygydia were typically missing the spines, but you could see the nub where the spines where originally attached. This is how I usually find them (without spines). The associated cephalons that I can only assume are from the same species, are what I believe was described as Glyptambon amsdeni, from the same location in 1991.

 

Edgecombe, G. (1991). The Silurian dalmanitid trilobite Glyptambon Holloway: New species from Tennessee and Illinois. Journal of Paleontology, 65(2), 294-300. doi:10.1017/S0022336000020527

 

Here are a couple of photos from my recent trip. The cephalon is about 10 cm wide, and the eye is about 1 cm tall.

 

 

Glyp1.jpg

Glyp2.jpg

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DevonianDigger

@piranha & @Paciphacops, thanks for the feedback guys! It didn't match up to anything I was finding in the lists of the Tennessee material I had access to. Glad to have a direction to research further!

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dalmayshun

are the eyes amazing...I love the fact that you can see the individual lenses...I wonder what the mechanism was that read info from all those lenses...can you imagine how complex that brain must have been simply to process all the info taken in through those lenses. I am in awe. 

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FossilDAWG

While I agree that trilobite eyes are quite beautiful, I disagree that they would have required especially complex brains to process the information.  They are homologous with insect compound eyes, but many insects have many more elements (called ommatidia) than phacopid trilobites.  In insect (and horseshoe crab) eyes each ommatidia generates what we might think of as a pixel, with information about color (colour for the Brits and Canadians) and light intensity.  They do not, on their own, produce an image.  Rather, the ommatidia in a compound eye, which has a hemispherical shape, all point in a

slightly  different direction, and the brain stiches the "pixels" together to form an image.  In other words, you should compare each facet of a trilobite eye to a light sensing cell in the retina of our eye, not to the complete eye.  Because we have many more rods and cones (light sensing cells) in our retina than any trilobite, insect, or horseshoe crab have ommatidia in their compound eyes, our image forming capacity is much better.  However, some insects can partially compensate by being especially sensitive to moving objects (such as an approaching predator).  Also many insects can see further into the ultraviolet or infrared than we do.  Overall, though, the amount of information that arthropods have to process in their visual system is much less than what we deal with.

 

Don

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dalmayshun

certainly agree, lol, your information was terrific..considering the size of our brain compared to one inside a 1/2 long bug, I'm still going to go with my "amazing" comment...your explaination was actually what I was hoping to get. Perhaps, I was thinking perhaps more about nerves, and the individual connecting tissue or membrane or whatever, that connects each of those single lenses to work as a whole...I can't help but conclude the process in intriguing...perhaps that is a better word than complex...I was marveling at how all those lenses must work together, either as individual pixels or not...and even an insect brain, (how large is a dragon fly brain) makes me marvel...it controls amazing flight, 4 wings, 6 legs, a mouth, snatches insects out of the air, and allows the animal to see...for me, that is all marvelously intriguing. so can I ask you to elaborate a bit more...do scientists understand how the information was processed and moved...guess i am asking about the nerve system, if that is what arthropods use. AND thanks you so much, I continue to be fascinated by trilobite eyes...I had a trilobite from Paulding I was looking at under my scope, when  a lens came out of its socket, and so I was able to look at it individually as well...so cool. Thanks FossilDAWG, I always learn so much here . 

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FossilDAWG

A lot is known about how insect brains/nervous systems function, though of course there is still an enormous amount to learn.  When I was at the University of Arizona a colleague had a set-up with Manduca (tobacco hornworm) moths to study how visual information was used to drive flight control.  He was able to put tiny electrodes into the optic nerve and the motor neurons controlling the flight muscles, so the moth was flying free but tethered to these fine wires.  He had the moth flying in a wind tunnel that had a conveyor belt on the floor so he could scroll a paper belt that had a pattern that made it look as if the insect was drifting to the right or left as it was flying.  He could record the signals from the optic nerve and see how that controlled firing from the motor neurons as the moth tried to turn to keep flying in a straight line according to it's visual input.

 

Last year I saw an amazing seminar by a researcher who had genetically engineered mosquitoes using green fluorescent protein (gfp) so their nerves would give off light when they were active.  They had the mosquitoes mounted under a microscope with the brain exposed, so they could stimulate the antennae with different odors and then see all the nerves in the brain that processed that sensory input light up.  They are making great progress at understanding the entire process by which mosquitoes can recognize thousands of different odors and use that to find hosts for blood feeding.

 

I think this is really the golden age of neurobiology.

 

Don

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FossilDAWG

One more truly amazing factoid (in my opinion anyway): the smallest known insects are fairyflies (aka fairy wasps). 

From Wikipedia: "Fairyflies include the smallest known insect, Dicopomorpha echmepterygis from Costa Rica, which have males that are only 0.139 mm (0.0055 in) long. They do not have wings or eyes, their mouths are mere holes, and their antennae are simply spherical blobs. The ends of their legs have been modified into suction cups for clutching at females long enough to fertilize them.[20] They are so small, their entire bodies are smaller than a single-celled Paramecium.[28][29] Four male individuals, lined up end-to-end, would just about encompass the width of a period at the end of a typical printed sentence.[12] The females of the species, however, are typical fairyflies, and are much larger.[5][20] The smallest flying insect is also a mymarid, Kikiki huna from Hawaii, which is 0.15 mm (0.0059 in) long.[30]

 

Think about that: a fully functional flying insect with an adult body size of only 0.15 mm (6/100ths of an inch for those who still measure things relative to the King's thumb).  These are parasitoid wasps that insert their eggs into eggs of a variety of other (much larger) insects.  So they can fly, and they can process all the visual and olfactory information to find mates and then to find insect eggs in which to lay their own eggs.  They are fully functional, as much as any insect, or most vertebrates for that matter.  Yet, if their total body length is only 0.15 mm, how small is their brain?  Do they have a normal complement of neurons, only much smaller than usual, or do they make do with fewer neurons, or some combination of the two?  It turns out that the brain of one of the smallest species has only 7,400 neurons, compared to 340,000 in the housefly and 850,000 in bees, and most of those 7,400 neurons lack nuclei so they can be much smaller than normal neurons. 

 

See where admiring trilobite eyes can take us?  I love biology.

 

Don

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