Edestus "shark"

[Still_human]

Does anyone know much about the edestus? Ive always wondered about their teeth as they age. All sharks and fish(and animals), when they're young their teeth are also small. Edestus are supposed to never lose their teeth, like their buddy helicoprion(right?), and just have their jaws continue to extend out from their mouths over time. That being the case, how are the oldest teeth, from when they were little young things, full sized, or almost full sized, as they always are? The jaw bone starts off small at the tip, but quickly thickens, but the teeth start large. Also, does that mean that they are born with just a single tooth on the top and bottom, and grow new teeth at an unheard of slow rate?

[Troodon]

I believe Edestus teeth were replaced and moved forward as a conveyor belt.

 

http://www.prehistoric-wildlife.com/species/e/edestus.html

[Still_human]

Exactly. So that means the teeth at the front of the conveyor belt jaw are the oldest, which it must have had as a little baby, since they never lose any. The only way I can understand it is if they started with a few teeth and the teeth themselves grew until they were large enough, and THEN they started growing new ones and pushing the old ones forward. I'll bet that's not how it worked though.

 

[Still_human]

What a crazy "shark" they are! Almost as crazy as the helicoprion group. I would kill to get to actually see them, and how they worked.

[Auspex]

If their rate of tooth replacement was high compared to the shark's rate of growth, we would expect the observed results.

[PaleoRon]

I have seen single teeth on long jaw sections that had fairly deep grooves in the top of the "root" where it seems the next, newer, tooth and root section attached. Large multi tooth sections seem to show newer teeth nested into the older root sections. My thought was that the oldest, bottom, tooth and root section detached from the bottom of the tooth grouping as the animal aged. If the small teeth just break off from damage as the animal ages the leading edge of the tooth grouping would show obvious break damage and residual overlapping "root" sections.

 

[Still_human]

36 minutes ago, PaleoRon said:

I have seen single teeth on long jaw sections that had fairly deep grooves in the top of the "root" where it seems the next, newer, tooth and root section attached. Large multi tooth sections seem to show newer teeth nested into the older root sections. My thought was that the oldest, bottom, tooth and root section detached from the bottom of the tooth grouping as the animal aged. If the small teeth just break off from damage as the animal ages the leading edge of the tooth grouping would show obvious break damage and residual overlapping "root" sections.

 

I'm not 100% sure I'm following you, but if you're saying what I think I am, that would work except if you look at all the fossils, the tip of the jaw shrinks to a nice point, which means that's the very beginning of the jaw. If they grew and periodically broke off, they would have broken ends, not points, still. And the first tooth, being large, is placed at the very tip, not leaving room for missing baby teeth in front of it.

 

Whenever you see a long jaw with a single tooth, it's my understanding that it's from the other teeth breaking off post-fossilization. I don't think they could survive with just a single tooth. The teeth are permenant fixtures, but seem to be a weak spot that breaks easier than most other places, during/after fossilization. I guess it makes sense that they still have "sockets", even though they aren't supposed to lose the teeth.

 

is that what you meant, or did I misunderstand?

[Still_human]

2 hours ago, Auspex said:

If their rate of tooth replacement was high compared to the shark's rate of growth, we would expect the observed results.

Yeah, that's part of what confuses me--such small amounts of teeth for such large animals(over 20ft). They grow for decades and end up with like just a dozen or less teeth on each jaw? That tooth-to-growth rate is just so hard to imagine. 

[PaleoRon]

Read this section again.

 

"My thought was that the oldest, bottom, tooth and root section detached from the bottom of the tooth grouping as the animal aged." 

 

                                                   If the entire tooth and root section detach from the bottom of the tooth group there would be nothing left of that section. 

 

"If the small teeth just break off from damage as the animal ages the leading edge of the tooth grouping would show obvious break damage and residual overlapping "root" sections."

 

                                                   Again, not broken off. There could have been some mechanism (enzymatic action?) that weakened the connection (connective tissue)                                                          between the oldest tooth/base and the rest of the tooth group. Many animals, including humans,  have mechanisms that absorb the root                                                      of a tooth that is being shed/replaced.  New teeth would grow in from the rear as older and smaller teeth are shed from the front/bottom                                                       row. I do not believe that the teeth were never shed. 

 

 

 

 

[Auspex]

7 hours ago, Still_human said:

Yeah, that's part of what confuses me--such small amounts of teeth for such large animals(over 20ft). They grow for decades and end up with like just a dozen or less teeth on each jaw? That tooth-to-growth rate is just so hard to imagine. 

With that question, we have a line of inquiry: what, and how, were they eating that might let this make sense? We should maybe not use modern sharks in modern oceans to compare to a 350 million year old environment. Let's begin by placing "shark" in air-quotes when referring to Edestus. They are as unrelated to Charcharius as we are to Dimetrodon.

[Shellseeker]

2 hours ago, Auspex said:

Let's begin by placing "shark" in air-quotes when referring to Edestus. They are as unrelated to Charcharius as we are to Dimetrodon.

 

I like the way you think and how you turn a phrase, Chas. Just wish I had said it first...

[Still_human]

9 hours ago, PaleoRon said:

Read this section again.

 

"My thought was that the oldest, bottom, tooth and root section detached from the bottom of the tooth grouping as the animal aged." 

 

                                                   If the entire tooth and root section detach from the bottom of the tooth group there would be nothing left of that section. 

 

"If the small teeth just break off from damage as the animal ages the leading edge of the tooth grouping would show obvious break damage and residual overlapping "root" sections."

 

                                                   Again, not broken off. There could have been some mechanism (enzymatic action?) that weakened the connection (connective tissue)                                                          between the oldest tooth/base and the rest of the tooth group. Many animals, including humans,  have mechanisms that absorb the root                                                      of a tooth that is being shed/replaced.  New teeth would grow in from the rear as older and smaller teeth are shed from the front/bottom                                                       row. I do not believe that the teeth were never shed. 

 

 

 

 

Oh ok, I think I follow...although I'm going to feel so dumb if I'm wrong again lol!

are you talking about a baby teeth kind of situation? As babies they had their own tooth thing going on, and where we lose our baby teeth and have adult teeth grow in, they would have the entire baby jaw/root bar fall out and be replaced by the larger full size jaw/root bar(I like "root bar", that's what I'm gonna use from now on:)?

 

OH! I think i just got what u mean--do you mean the baby teeth root bar splits off from remaining root bar, and not the entire baby root bar being released from the gums? That's funny cause the only reason I caught that right now is because I just so happened to be about to point out on here that the root bar has layers, which could be "growth ring" type things. From what I'm able to see in multiple pictures, is that each layer ends in a tooth, so if those are growth patterns, that means they grow a new tooth for each growth cycle, however many years that might be. 

[Still_human]

Yeah, they're in the chimera family. Was i calling them sharks? I thought I used "" around the word shark. If not, sorry, I really should've been more careful with that:/

wow, I forgot the "" in the actual thread title! It's fixed now, though:)

[Auspex]

48 minutes ago, Still_human said:

I'm going to feel so dumb if I'm wrong again lol!

I hope not, and I will censure anyone who suggests that asking good questions in search of the truth  is "dumb".
This is how science (and the Forum) thrives!

[Auspex]

It strikes me that the morphology of the alternating tooth positions in the Edestus jaw bone is very like that of the denticles on a ratfish fin spine.

Close enough to suggest a re-expressive gene.

[Still_human]

6 hours ago, Auspex said:

It strikes me that the morphology of the alternating tooth positions in the Edestus jaw bone is very like that of the denticles on a ratfish fin spine.

How do you mean?

[Auspex]

looking down at either one, with teeth/denticles pointing up, their bases overlap left-right-left-right; they are not just strung end-to-end, but are staggered like footprints.

[Still_human]

5 hours ago, Auspex said:

looking down at either one, with teeth/denticles pointing up, their bases overlap left-right-left-right; they are not just strung end-to-end, but are staggered like footprints.

Oh ok, like this, gotcha. I'm confused about the connection though. Edestus have a single row of teeth on each jaw. 

[Auspex]

3 hours ago, Still_human said:

Edestus have a single row of teeth on each jaw. 

Some do, but some have a single staggered row. If I can find one that I have like that, I will post a picture. (If it is in a box 280 miles away, that will take a while...).

[Still_human]

7 hours ago, Auspex said:

Some do, but some have a single staggered row. If I can find one that I have like that, I will post a picture. (If it is in a box 280 miles away, that will take a while...).

That I did NOT know! I'm very surprised about that, Ive not seen any like that. I guess it would be kind of hard to tell from the side view usually given, but I feel like they at least don't overlap from a side view, even if the DO from above

[Auspex]

On another thread this afternoon, an image turned up that illustrates what I am talking about (although the staggering is not so clearly evident as on mine and others I have seen).

[Still_human]

Oh wow, I never knew that! That's cool, thanks! i guess that means the upper and lower jaw don't have to have the teeth alternating to close, but can actually have them match eachother, Just alternate side-to-side. This way would probably even cut better, too.

[Still_human]

On 8/16/2018 at 5:40 AM, Auspex said:

Some do, but some have a single staggered row. If I can find one that I have like that, I will post a picture. (If it is in a box 280 miles away, that will take a while...).

Wait, so they're not all like the picture? That's really odd if some alternate, while others line up. I wonder if that's a difference between species. I'll have to look them up and see if there ARE more than one. I'd imagine if there were differences like that  between an animal from different locations, that it would be made a separate species. That's a much bigger difference than between some that were split into separate species.

 

*update: yeah, there's a number of different species of edestus, so I'll bet that's it.

[Still_human]

--Just a brainstorm--I wonder if helicoprion and the other ~coprions evolved from edestus. They're in the same non-shark/chimera family, and edestus' jaw could easily be an early form of the helicoprion groups tooth whorls. 

Does anyone have any information supporting or refuting it?

[Still_human]

i just noticed--look at the jaw on the bottom right. It has alternating teeth too! None of the others do. Maybe it's my imagination, but it looks like the jaw shape of that one is different than the rest. Much shorter and thicker. 8 teeth present, and missing at least 3. That's the same amount of teeth as the largest jaw right next to it. Thats got to be a different species. It actually appears to have a much heavier alternation than the other alternating one in the picture above, even taking the angle into consideration.