Mosasaur dorsal fin

[Scipionyx]

I have heard of the relatively recent discovery of tail flukes in mosasaurs, but I have seen some reconstructions showing them with ichthyosaur or dolphin-like dorsal fins (here is an example: ).
I think they look really cool, but how plausible is it really?

[Dinoguy2]

I feel like we probably would have found evidence for this by now, but i'd have said the same thing about flukes a year ago...

Not all marine animals swim in a way that requires dorsal fins, but who knows at this point?

[Yutyrannus]

Hmm...I think that may be taking things a bit too far.

[Balaur]

How? We have ichthyosaurs with dorsal fins. Speaking of which my Halisaurus for Sea Monaters does have a dorsal fin.

[Yutyrannus]

Pretty much what Dinoguy said, we probably would have found evidence of it by now as we did in ichthyosaurs. Then again it could be possible, but something about the way mosasaurs are built doesn't go with a dorsal fin.

[Balaur]

Pretty much what Dinoguy said, we probably would have found evidence of it by now as we did in ichthyosaurs. Then again it could be possible, but something about the way mosasaurs are built doesn't go with a dorsal fin.

I guess so. The dorsal fin for Halisaurus will not be that big, like those in humpbacked whales.

[Yutyrannus]

Pretty much what Dinoguy said, we probably would have found evidence of it by now as we did in ichthyosaurs. Then again it could be possible, but something about the way mosasaurs are built doesn't go with a dorsal fin.

I guess so. The dorsal fin for Halisaurus will not be that big, like those in humpbacked whales.

Oh, that would work, I was talking about a shark or dolphin-like dorsal fin.

[Balaur]

Oh, okay.

[DinoToyForum]

Without soft tissue evidence we may never know. It isn't impossible.

I've even seen plesiosaurs restored with a dorsal fin, though that is highly unlikely!

[EmperorDinobot]

Need evidence. I put in a mini dorsal fin on one of my mosasaurs quite some time ago...the one with the funny name. I forget.

[Funk]

The specimen with the tail fluke also shows the outline of the limb fins, but no dorsal fin, even though the back is preserved. So seems unlikely.

[Newt]

I don't really know that much about mosasaurs, but I always assumed they would swim with a full-body lateral sculling motion, like modern crocodilians and large lizards.  If so, a dorsal fin would be a hindrance, as its purpose is to improve tracking (moving forward in a straight line), and it would only impede lateral sculling.  It's sort of like a keel on a boat; boats made for long distance travel have prominent keels, while those made for maneuverability (such as whitewater canoes and kayaks) may have no keel at all.

Of course, if the fin were mobile, as in bony fishes, this wouldn't be an issue, but I don't believe anyone has proposed this. There would almost have to be some bony, or at least cartilaginous structure, as well as muscle attachments on the spine, involved that would surely leave some trace.

[Reuben03]

well this discussion has been revived recently in paleo circles due to the discovery of Megapterigyus, a long finned mosasaur from japan, related to derived mosasaurinae mosasaurs like plotosaurus.

some feel strongly, including the authors of the paper, that this animal possessed a dorsal fin, due to the bizarre dorsal differences not seen in other mosasaurs, but seen in cetaceans possessing a dorsal fin.

however i personally feel due to multiple reasons that regardless of whether or not this species in particular had a dorsal fin, i really don't think we should start putting them on all our mosasaurs, not at all.

in fact i'd go so far as to say theres issues with the way we reconstruct our mosasaurs now already! the last thing we need is to add unneeded dorsal structures to our mosasaur artwork.



one issue i have is that there are cetaceans with similar dorsal structures and they don't have a dorsal fin, it could be another concavenator quill knobs situation.

[BlueKrono]

@Reuben03 I have mixed feelings about mosasaur dorsal fins. I'll let the scientists figure out whether they were more likely or not, but when it comes to dino toys... I don't usually collect sea reptiles with dorsal fins. I don't think they're as cool and won't add them to my collection, so this trend will obviously save me money. Positive and negative I guess.