Predatation Marks Or Weird Fossilization?

[DeepTimeIsotopes]

This is quite an odd find but I'm pretty sure it is a Knightia eocaena. The spine has a weird curve in it, which looks like a bite pattern...

Edited October 19, 2014 by Utahfossilhunter

[tmaier]

OK, I thought about it for a half hour, so here is my opinion.

The fish became stranded due to drying up of the lake. A predator like a raccoon came along and ate some out of the upper back, right behind the dorsal fin, but not as deep as the backbone. Then the fish was washing back and forth in the receding water and the water movement broke the backbone in the two places that you see. The two halves were floating separately, attached by the backbone. Then it was covered with silt and fossilized.

I got this idea because I've seen a similar thing happen to the salmon that run up stream to spawn, and then die, wash up on shore, and are partially eaten by raccoons. Sometimes they are almost cut in half, but the raccoons often don't eat the spine. There are so many salmon to eat the raccoons don't eat the whole thing and they don't run off with it, they just move to the next fish.

So yes, I think this was caused by predation by a land animal.

[snolly50]

Just conjecture, but the most likely agent is post-mortem disarticulation brought on by one of many factors that could have impacted the decaying critter (e.g. current, small scavengers). I would guess that anything with a powerful enough bite to displace the spine to that degree, would simply have severed the morsel it was after.

Geological shifting might also be a player, but the visible portion of the slab suggests an undistorted layer.

Neat little fish.

[Fossildude19]

I agree with Snolly, it's probably due to decomposition rather than predation.

The body exploded from gasses contained within the rotting fish, and current or wave action moved the spine to where it is now.

Regards,

[squali]

I'm in the non predation camp. Knightia are of similar size to sardines and would be consumed in entirety.

I am working on a dis articulate fish now and you would be surprised where the anatomy ends up.

[tmaier]

I'm sticking with predation by scavengers, because I've actually seen this happen many times to fish in the field.

[DeepTimeIsotopes]

Both sides have a point but both have the conclusion that this happened after death. It may be a mix of these theories as well or maybe the aliens did it...( just joking!)

[tmaier]

Some pictures to think about...

http://www.google.com/search?q=mass+fish+kill&btnG=Search&hl=en&gbv=1&tbm=isch

[snolly50]

Some pictures to think about...

http://www.google.com/search?q=mass+fish+kill&btnG=Search&hl=en&gbv=1&tbm=isch

A fascinating look at piscine carnage. Indeed the Green River Formation (the assumed resting place of the specimen at hand) is well know for mass mortality plates preserved in the fossil record. Schooling fish, Knightia and Gosiutichthys are preserved together by the hundreds. Water stratification inversion and toxins (think, algal bloom) are often cited as the lethal culprits.

This begs the question is this a lone individual and is he plate large enough to provide an answer?

The other impulse that would have already taken over were the specimen mine - is there any more of the creature to be revealed? As an adventuresome prepper, I would take a carbide needle, under magnification, to the "scalloped out" area. I believe there may be more preserved there. I see at least one scale which is matrix obscured. Finding more, albeit disarticulated, would further test the extant hypotheses.

Just because I would do it, please don't dig into a nice piece. I would enjoy doing it, but your mileage may vary.

[DeepTimeIsotopes]

A fascinating look at piscine carnage. Indeed the Green River Formation (the assumed resting place of the specimen at hand) is well know for mass mortality plates preserved in the fossil record. Schooling fish, Knightia and Gosiutichthys are preserved together by the hundreds. Water stratification inversion and toxins (think, algal bloom) are often cited as the lethal culprits.

This begs the question is this a lone individual and is he plate large enough to provide an answer?

The other impulse that would have already taken over were the specimen mine - is there any more of the creature to be revealed? As an adventuresome prepper, I would take a carbide needle, under magnification, to the "scalloped out" area. I believe there may be more preserved there. I see at least one scale which is matrix obscured. Finding more, albeit disarticulated, would further test the extant hypotheses.

Just because I would do it, please don't dig into a nice piece. I would enjoy doing it, but your mileage may vary.

I am fairly certain he is a lone individual. The plate he came from was fairly large with only him on it. I cut around this specimen about 2 inches out and the sides I cut had nothing in or on them. As for the carbide needle, all the tools I have at my disposal at this time are some $5 dental picks so there is only so much I can do without damaging the fish extensively.

[squali]

The scavenging I have seen is usually centered around the gut and head region.

There doesn't seem to be an obvious pattern of scavenging. The scales appear to

have moved towards the missing vertebrates.

[squali]

Geeze I can't see worth a darn. The vertebrae are all there just pushed askew.

Definitely not predation.

[snolly50]

I am fairly certain he is a lone individual. The plate he came from was fairly large with only him on it. I cut around this specimen about 2 inches out and the sides I cut had nothing in or on them. As for the carbide needle, all the tools I have at my disposal at this time are some $5 dental picks so there is only so much I can do without damaging the fish extensively.

Well, it displays great as it is. My urge to poke it more just comes from curiosity. I don't imagine there is much to be gained by any additional prep. It is probably best displayed as it is. A little mystery never hurts. It is a wonderful thing. I am very fond of these amazing fish. I have prepped quite a few, but have never been to the quarries. I've been invited, but never took the time/effort. I guess it's on my bucket list. Thanks for posting this interesting piece.

[DeepTimeIsotopes]

Well, it displays great as it is. My urge to poke it more just comes from curiosity. I don't imagine there is much to be gained by any additional prep. It is probably best displayed as it is. A little mystery never hurts. It is a wonderful thing. I am very fond of these amazing fish. I have prepped quite a few, but have never been to the quarries. I've been invited, but never took the time/effort. I guess it's on my bucket list. Thanks for posting this interesting piece.

The particular quarry I visited was Warfield Fossil Safari. It was a great time! I found more than enough fossils within an hour.

Eventually I will get better tools so I can remove some of the mystery within my pieces. Also I thank you for answering my topic, along with all these other fine people!

[tmaier]

I might have given the wrong impression with using the word "predation". That implies one creature killing another. I think the fish was dead on the shore and scavenged, having the section behind the dorsal eaten out. When I've see this with salmon die-off at the end of spawning, the head and tail halves are bobbing around independant from each other, tethered together by the spine and some of the belly skin. The two pieces end up in different orientations.

There is quite a stench after the dying...

http://www.google.com/search?q=dead+salmon+spawning&btnG=Search&hl=en&gbv=1&tbm=isch&nfpr=&spell=1

Here's one that was eaten almost in half above the dorsal...

http://www.shutterstock.com/pic-60302464/stock-photo-dead-salmon-during-spawning-partially-eaten-by-wild-animals.html

When only one fish dies, it is commonly dragged off into the woods and wholly consumed. When many die, the scavengers don't bother and just move on to the next fish. The woods becomes full of scavengers from miles around to partake in the feast.

[Fossildude19]

I'm not sure.

There were massive fish kills in the Green River Formation, and just because it was found alone, to me, does not indicate predation/scavenging.

It isn't the woods, and there are wave action and currents to be taken into consideration as the fish sank to the bottom, and as it lie there, on it's way to becoming a fossil.

I don't see many ribs really broken, as you would expect from predation, or scavenging, and the area above the backbone seems like it would be a rather shallow bite . The absence of the scales in that area leads me to believe that an explosive release of the decompositional gasses are responsible for this. I don't believe this guy made it to the shore.

Just my two cents. I have enjoyed reading your postulations, Tmaier.

Regards,

Interesting related paper HERE.

Edited October 21, 2014 by Fossildude19

[tmaier]

The reason I can't go along with the decomposition, gas explosion idea is because the front and back halves of this specimen are in such good condition. Also, being an avid fisherman and outdoorsman, I've never seen something like that happen and would need to see and example.

I can't think of any other way to explain what we see.

Edited October 21, 2014 by tmaier

[Fossildude19]

The reason I can't go along with the decomposition, gas explosion idea is because the front and back halves of this specimen are in such good condition. Also, being an avid fisherman and outdoorsman, I've never seen something like that happen and would need to see and example.

I can't think of any other way to explain what we see.

[tmaier]

That second specimen you show has the similarity to the Green River fish in that the missing section of the fish on both is directly above the anus, in close association with the intestinal tract of the fish. So, yes, that does add credence to the idea of abdominal gas from decomposition having some role in it.

But notice on that scavenged salmon I showed above, the spine is still exposed, many scales are missing from the scavenged area, but the spine is bowing together, exactly like the Green River fish. and I can tell you that is quite common with scavenged fish from mass die offs in the field.

How do you know that the second fish you show was not scavenged in half?

[Fossildude19]

These fish, while from different times and locales, are products of a similar, anoxic environment, virtually devoid of the scavengers and microbes that would have inhibited fossilization, or defaced the fish bodies.

Having seen many examples of this, and given the similarity of environments at the time of fossilization, I think it's the more likely scenario.

The paper I posted the link to (in post #16) states :

"However, as the F-2 beds were deposited in a more marginal setting, both facies can be broadly considered as shallow water deposits. Fossil fish are most abundant in these F-1 and F-2 facies and also tend to be better preserved than in other lithologies, particularly in the more organic-rich F-1 deposits (Buchheim et al.2011).

Bioturbation or other soft sediment disturbance is absent in both facies. Excellent preservation of coprolites, highly articulated fish, plus the lack of any disturbance of the sedimentary laminations, all strongly suggest that macroscopic infauna, and probably benthos, was absent (see Grande 1984).

A lack of oxygen in the interstitial pore waters and lower parts of the water column is the most likely inhibitory factor.
The presence of a highly diverse nekton confirms the water column in Fossil Lake was stratified, as suggested in the seminal depositional model erected by Bradley (1948)."

PG.355

Regards,

Edited October 21, 2014 by Fossildude19

[tmaier]

Ahh... so these fish died and sank into an oxygen deprived area? That would rule out scavenging. I had always assumed that these Green River fish were from mass seasonal die-offs and they floated to the shore.

If that is well proven, then I have to change my opinion.

Thanks.

[Fossildude19]

Thank you for providing an interesting discussion!

You think outside the box, and that is a great quality.

Regards,

[tmaier]

I've spent most of my life in research. I stick with the data until better data comes along. I've found it to be the most fruitful method of solving problems.

I don't consider it "outside the box", I see myself locked in the box by surrounding data. It never hurts to try to speculate a way out, but you are not allowed to leave the box unless you find more data that opens a door.

[DeepTimeIsotopes]

Wow it's amazing what one picture can do, this is a great discussion!

[DeepTimeIsotopes]

One detail I have missed is that there is a coprolite to the bottom right that seems to not be in the picture which would add more credibility to the underwater theory.