How did Dunkleosteus really look like

[Stegotyranno420]

I seen and heard many folks argue about dunkleosteus appearance and size, like the tail, the armor, and some even proposed lips and it's all confusing. Dunkleosteus in figure for, usually has lipless jaws, hard armor, and a eel like tail, so how accurate is it based on the most current dunkleosteus depiction?

[Newt]

Dunkleosteus is known only from the armor plates that covered the head and front of the trunk, and from pectoral fin elements. So reconstructions of the rest of its body are not based directly on fossil evidence.


Some much smaller relatives of Dunkleosteus, such as Coccosteus, are known from more complete remains. The eel-like tail seen in most Dunk reconstructions is based on Coccosteus. However, a recent paper (Humberto G. Ferrón, Carlos Martínez-Pérez and Héctor Botella. 2017. Ecomorphological inferences in early vertebrates: reconstructing Dunkleosteus terrelli (Arthrodira, Placodermi) caudal fin from palaeoecological data) indicates that a Coccosteus-like tailfin would not be adequate for an animal as big as Dunkleosteus if it were an active open-water swimmer. We know Dunkleosteus was an active open-water swimmer because of the black shale sediments where its remains are found - these kinds of sediments form where the waters near the ocean bottom are deoxygenated and cannot support large animals. Ferron et al. therefore reason that Dunkleosteus must have had a tail more like ecologically similar pelagic sharks (and ichthyosaurs, for that matter), rather than phylogenetically close Coccosteus.


As far as fleshy coverings and lips go, this is just the normal way vertebrates do things. Exposed bone is surpassingly rare in living vertebrates (only the antlers of deer, and even they are only exposed a few months of the year). Bony armor may be covered by thin scutes, as in turtles, or by more substantial dermal coverings. Lips are more variable, but most vertebrates have them. Often with archosaurs the density of nutrient foramina (tiny holes in the bone that allow blood vessels to pass through) in the oral region is used to determine the presence of lips; I'm not sure if this is applicable to Dunkleosteus.

[Stegotyranno420]

Dunkleosteus is known only from the armor plates that covered the head and front of the trunk, and from pectoral fin elements. So reconstructions of the rest of its body are not based directly on fossil evidence.


Some much smaller relatives of Dunkleosteus, such as Coccosteus, are known from more complete remains. The eel-like tail seen in most Dunk reconstructions is based on Coccosteus. However, a recent paper (Humberto G. Ferrón, Carlos Martínez-Pérez and Héctor Botella. 2017. Ecomorphological inferences in early vertebrates: reconstructing Dunkleosteus terrelli (Arthrodira, Placodermi) caudal fin from palaeoecological data) indicates that a Coccosteus-like tailfin would not be adequate for an animal as big as Dunkleosteus if it were an active open-water swimmer. We know Dunkleosteus was an active open-water swimmer because of the black shale sediments where its remains are found - these kinds of sediments form where the waters near the ocean bottom are deoxygenated and cannot support large animals. Ferron et al. therefore reason that Dunkleosteus must have had a tail more like ecologically similar pelagic sharks (and ichthyosaurs, for that matter), rather than phylogenetically close Coccosteus.


As far as fleshy coverings and lips go, this is just the normal way vertebrates do things. Exposed bone is surpassingly rare in living vertebrates (only the antlers of deer, and even they are only exposed a few months of the year). Bony armor may be covered by thin scutes, as in turtles, or by more substantial dermal coverings. Lips are more variable, but most vertebrates have them. Often with archosaurs the density of nutrient foramina (tiny holes in the bone that allow blood vessels to pass through) in the oral region is used to determine the presence of lips; I'm not sure if this is applicable to Dunkleosteus.

Wow thanks very much, so to be clear the awnsers are still debatable due to the small amount of evidence we have, but this is the most likely outcome?

[RobinGoodfellow]

..not the most up-to-date reference but still interesting:

https://youtu.be/GakZEA80xNI

[Ozraptor4]

Despite recent online speculation among paleoartists and bloggers regarding "lipped Dunkleosteus", this idea has never been seriously championed by fossil experts within peer-reviewed literature. Cannot rule out the possibility, but if Dunkleosteus really did have enough extraoral tissue to completely conceal it's gnathal blades, it would have been an extremely unusual placoderm - thus most Devonian fish workers consider the possibility unlikely.

Earlier placoderms (Entelognathus, Romundina, Brindabellaspis etc) didn't have full-lips (Antiarchs might have been an exception, but they are phyletically very far from Dunk.). Jaws bones were covered with rough bony ornamentation all over the outer surfaces (often extending into the biting margins) which would have abraded/torn away any extraoral tissue. Dunk. and it's close relatives lost this ornamentation, but this at least demonstrates that their immediate ancestors were lipless.

Also worth noting that no evidence of arthrodire lips has been identified in the Gogo Formation, a Devonian Lagerstätten famous for preserving soft-tissue in placoderms, including dunkleosteid taxa like Eastmanosteus . (although it should also be noted that external lips would be harder to preserve vs internal organs shielded within the trunk armor).

[andrewsaurus rex]

Dunk's tail has long been an area of interest with me.   When I first joined this forum I had a long discussion with some of the members about the true shape of Dunk's tail.  I felt that the shark like appearance of Dunk was nothing more than sensationalism by paleontologists trying to grab some headlines and sell some books.

After reading some well thought out and reasoned arguments from other forum members, I concluded that it's certainly a strong possibility that Dunk did have a shark like tail.....i'm about 85% of the way there.   There is no question that smaller placoderms definitely had an eel like body.  That is for sure.  So the question is, if the body shape changed to a more shark like appearance, at least in the tail area, at what point in placoderm evolution did that begin ie how big did they have to get in order for those evolutionary changes to be forced upon them (ie selected for).  It's quite a transition from eel like to shark like, so as I said, i'm personally only about 85% convinced.   However, it's also quite a transition from 4 legged land animal to whale, so...

Nature is full of surprises that often defy logic and reason.

[Bowhead Whale]

Dunkleosteus is known only from the armor plates that covered the head and front of the trunk, and from pectoral fin elements. So reconstructions of the rest of its body are not based directly on fossil evidence.


Some much smaller relatives of Dunkleosteus, such as Coccosteus, are known from more complete remains. The eel-like tail seen in most Dunk reconstructions is based on Coccosteus. However, a recent paper (Humberto G. Ferrón, Carlos Martínez-Pérez and Héctor Botella. 2017. Ecomorphological inferences in early vertebrates: reconstructing Dunkleosteus terrelli (Arthrodira, Placodermi) caudal fin from palaeoecological data) indicates that a Coccosteus-like tailfin would not be adequate for an animal as big as Dunkleosteus if it were an active open-water swimmer. We know Dunkleosteus was an active open-water swimmer because of the black shale sediments where its remains are found - these kinds of sediments form where the waters near the ocean bottom are deoxygenated and cannot support large animals. Ferron et al. therefore reason that Dunkleosteus must have had a tail more like ecologically similar pelagic sharks (and ichthyosaurs, for that matter), rather than phylogenetically close Coccosteus.


As far as fleshy coverings and lips go, this is just the normal way vertebrates do things. Exposed bone is surpassingly rare in living vertebrates (only the antlers of deer, and even they are only exposed a few months of the year). Bony armor may be covered by thin scutes, as in turtles, or by more substantial dermal coverings. Lips are more variable, but most vertebrates have them. Often with archosaurs the density of nutrient foramina (tiny holes in the bone that allow blood vessels to pass through) in the oral region is used to determine the presence of lips; I'm not sure if this is applicable to Dunkleosteus.

If I understand well, it is like supposing the great white shark should have a tail with the upper half of the fin way longer than the lower half because almost all sharks have a tail that is far from being symetrical, almost eel-like. And, all of a sudden, seeing a great white for the first time, we see THIS particular shark has a tail fin that is almost symetrical. At least, very close to symetry for a shark. It seems like we are experimenting something like that with Dunkleosteus.

[Newt]

@Bowhead Whale - Just so. Of course, deducing the animal's shape from supposed ecological equivalents is not foolproof. Dunk's postcrania may be no more like those of modern pelagic fish than like those of little Coccosteus. See old reconstructions of Deinocheirus that made it look either like a typical, if long-armed, large carnosaur or like an inflated Ornithomimus; neither was close to the unexpected and bizarre morphology revealed when more complete fossils were discovered. Nature is full of surprises!

[Halichoeres]

If I may indulge in some self=promotion, I wrote a pretty detailed thread about Dunkleosteus here: http://dinotoyblog.com/forum/index.php?topic=9367.0

[Faelrin]

Yeah I'm thinking this newest member might be a bot, what with digging up random older threads posting stuff based only on the titles without context of the rest of the thread, or like this outdated and incorrect info above. Dunkleosteus a filter feeder? Not a chance. The eel tail hypothesis has been outdated in favor of a fluked tail for a number of years now.

Edit: Gone now lol.

[DefinitelyNOTDilo]

Yeah I'm thinking this newest member might be a bot, what with digging up random older threads posting stuff based only on the titles without context of the rest of the thread, or like this outdated and incorrect info above. Dunkleosteus a filter feeder? Not a chance. The eel tail hypothesis has been outdated in favor of a fluked tail for a number of years now.

Definitely

[Lynx]

Yeah I'm thinking this newest member might be a bot, what with digging up random older threads posting stuff based only on the titles without context of the rest of the thread, or like this outdated and incorrect info above. Dunkleosteus a filter feeder? Not a chance. The eel tail hypothesis has been outdated in favor of a fluked tail for a number of years now.

They also repeat typical patterns of Chat GPT results

[Justin_]

"They" have made 15 posts in the last few hours. Often long posts only a few minutes apart, and as previously noted, on old threads.

https://dinotoyblog.com/forum/index.php?action=profile;area=showposts;u=3270

[HD-man]

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