Permian Predators

[dinodigger]

Thanks for the great responses; I'm glad to see its making everybody think. Here's an attempt at responding to some of those. What we are seeing preserved in this situation and the dilemmas that present themselves in regards to the trophic levels, are definitely out of the norm. There is no question that there is cannibalism occurring; aside from the buckets of shed teeth representing the feeding zone, we have tons of Dimetrodons that have been dismantled and chewed, their remains slowly pulled apart. The larger bones of the individuals mark the unmistakable consequences of a finback encounter, the chew marks are abundant. Large bones such as Femurs and Humeri are often missing major condyles; ribs now no more than rib-lets, we even have a complete pelvis with a substantial hole bitten directly through the ilium, and a maxillary fang found not far away that fits exactly. (This was no love-bite on the rump... this one would have been fatal.) The evidence for cannibalism is clear, it happens. Just how long did it occur, was it seasonal, why here?

Soft-Bodied Organisms

Sure. There were tons. Its a pond filled with worms and fish that failed to fossilize. But are these the food source of a Dimetrodon that needs a bulky substance to sustain. He would have to eat a lot of fish to sustain, and we have a small pond with hundreds of Dimetrodons. Not likely going to be a major food source.

Sharks

We do have sharks in one zone, and they were fed on by Dimetrodon. What is the evidence here? Thousands of shark teeth; OK, sharks lose there teeth, not a great way to count sharks. Thousands of headspines; great way to count sharks. They have one, and don't regrow them. Tons of shark skulls. Ok. Not a good technical term for this purpose, but the ammount of shark-cartilage, or Shark-lage as we call it, is immense. The common six foot Xenacanth only has so much cartilage. A general calculation of how much cartilage can be done. And on a side note, the Xenacanth only reached around 6 feet. Not a big shark. 200 pounds. Enough meat to fill a Bull Dimetrodon for a summer, or six months. The smoking gun: a large shark skull with a Dimetrodon post-canine embedded. Good evidence there. The problem here is this. The Shark Zone has hundreds of Shark. But the evidence for Dimetrodon is minute. Only enough shed teeth (Dimetrodon) to count on two hands. The Dimetrodon were not living there. We don't have any Dimetrdon remains there. Maybe an isolated fragment of bone here and there, but nothing substantial enough. They fed there rarely. Yes, the waterhole when filled with sharks was a perfect food source for Dimetrodon. Yes; this source was tapped by Dimetrdon, and most likely each season the Dimetrodon population fed and was happy. And they did not feed there. They took their meals elsewhere, or we would have more shed teeth. Now back to our main Dimetrodon bone bed. NO SHARKS. Zero. Nadda. None. No teeth, no shark-lage. Zero. So in the main bone-bed, shark was not on the menu. But Dimetrodon was.

So Did the Population Last?

Yes. Temporarily. And it absolutely fell apart and was eventually decimated. The population did not survive. The OX-Bow dried up as well. There was not enough water for sharks at their level. There was, at one time, a few seasons past. Once the Dimetrodon returned to their favorite sea-food hut only to find out that the Xena's had moved on, the Dimetrodon turned toward eachother, and they survived just fine. We have excellent age-distributions of bones, teeth, spines, etc. The ratio of big adults is smaller than the ratio of infants, and that pyramid is pretty regular. The big adults did keep the population down. They lived and fed, together and on each other. Again, a bull Dimetrodon can survive for six months or better on a 200 pound carcass. One infant Dimetrodon of a hundred pounds was good eating. But yes. After so long and so little other food source, the population decimated.

Successive Seasonal Events

When the watering hole was full of sharks, the Dimetrodon most likely visited regularly to feed. We have the "smoking gun" skull with the tooth. In the wild, we see big carnivores retreat with their kill to feed, so not finding a whole lot of sheds, and finding a whole lot of Maxilar-ily dismantled sharks, not unusual. The rainy season came and went. Multiple layers with amphibians supports that. The cut-off had enough water to support sharks at one time. Now in the Dimetrodon Zone, we have a population that is living there. Babies to adults. Feeding. Expelling.

So what the $%^&* is going on??

The problems that remain, are these?

How long did this population actually survive at this location. Working on that one.

Did the Dimetrodon survive primarily on each other, and small amphibians? Most-Likely. The amphibs would have been nuggets, but enough to feed the young ones. The young ones enough to feed the adults, and so on.

Why here? This may have been a last stand for water in the area. Crocs travel hundreds of miles to get to the next watering hole. These most likely didn't. Too many ages present. With a final lingering waterhole, this population stayed.

Could the not escape.

This is a great thought. Just recently we found evidence of a collapsed sinkhole. This seemed to be occurring regularly in the area do to Ordovician salts underneath. So the possiblity of a ecosystem in which these guys got trapped is possible. Still working on that one with Dr. Bakker. Might have a better response for that later.

Anyway, I'm sure I'll have another load to spew at you soon. Next trip coming up fast. Should have some good reports coming.

Hope all is well and everyone is in good health. Snakes are definitely on the move, so look-out. Be smart out there on your travels.

Chris

Edited May 17, 2010 by dinodigger

[Fossildude19]

Chris,

Thanks for the insights! Really,... very interesting stuff. And now, with the sinkhole evidence.... makes allot of sense.

Pretty cool!!

It is great to hear about all you've been finding, and "finding out" about this sight,... and I am looking forward to your next report!!!

Thanks so much,... for "Bringing us there" with you!

[TroyB]

One thought would be was the shark cartlage tough enough to cause the Dimetrodon to shed teeth? Or, did he simply gulp them down like chicken nuggets?

[Rover]

So, essentially this is shaping up to be somewhat like the "predator-traps" that you see at places like La Brea, except, instead of specifically trapping predators due to the very nature of the place, a large population of predators just got unlucky and ended up there, along with the aquatic creatures that were trapped when the ox-bow was formed from a bend in a river.

Incidentally, how strong is the evidence for plant life at this location, and what types are you seeing? This may explain why it was Dimetrodon and not some herbivorous population that got trapped here.