A lizard with fins or a hybrid of a lizard and a whale?
I know that not every mosasaur species preferred the same habitat. Although known to be marine predators of open water, they were also represented by riverine (freshwater) species.
They are sometimes depicted with smooth scales, sometimes with roughened ones.
So, which species are we most certain about?
An interesting fact about them is that they most likely had the same tracking and finding device as monitor lizards: a forked tongue. This is indicated by the anatomy of their skull, which shows openings suitable for Jacobson's organ. So this detail of the reconstruction at the top is not just an artistic vision.
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What’s that top image from?
This is some guy's 3D replica.
Link to his Instagram. https://www.instagram.com/p/C6z_kP8LlHt/?img_index=1&epik=dj0yJnU9b3NlZGk5Z2dpR1luLWpLdVAtZFI3X3JxZlp6bGF6NzEmcD0wJm49TVRmN3MzV2JtQzc2R01NZnlfMDhhUSZ0PUFBQUFBR2xIOWFJ
Thanks bro!
Somewhere in between. They were very lizardlike with a couple whale-ish features. Its likely a scale between them depending on where in the evolution the species you are looking at is.
That being said, the bottom reconstructs it WAY too wide. Mosasaurs were extremely sleek, streamlined predators, and their torso wasnt a whole lot taller than their skulls were. Path of Titan's new Tylosaurus is a superb mosasaur depiction that nails it
Most images of their skeletons that I can find show massive ribcages.
Most have a tendency to articulate the ribs wrong
"This content is no longer available."
:(
It’s got a heavily backswept ribcage.
So it's supposed to look something like this
https://preview.redd.it/xpil7ryyhv8g1.jpeg?width=815&format=pjpg&auto=webp&s=4fec3690e740c8364690ae997b3fde2debcf8610
(best photo I could find where the ribs don't appear to be perpendicular to the spine. Hard to tell because of the angle)
And this is Plotosaurus even, one of, if not the most ichthyosaur-like mosasaur
Yeah, kind of like this.
Thank you for the confirmation :)
I see.
fun fact, that bottom one wasn't really that all up to date. It was mostly speculative because the fossils were still under study.
That’s rly cool how the Path Of Titans devs made a scientifically accurate (at the moment) tylosaurus!
Honestly, they've been doing awesome with their newer models
Imo, the second version kinda makes more sense because it's more hydrodynamic, and that's a thing necessary for sea predators
While you could argue the similarities are due to convergent evolution for the purposes of hydrodynamics, Mosasaurs still look too similar to whales. Look at that image, it literally looks identical to an early whale, and it shouldn't. Its a reptile, it should look more like a water born monitor lizard with sharper features.
Not like a whale
As it happens, whales don't look like mammals either. It would be better said that whales are mimicking mosasaurs. There's a reason the shark-like body plan keeps evolving, and why we don't still have whales that look "like a mammal". Whales are unique and jt's one of the most converged-upon shapes in nature. It's that good.
You ever heard of basilosaurus? It's name means emperor lizard, it's a whale but it's skull made the discoverers think of a reptile first, it really looks like the mammal version of a mosasaur impo
It was probably a bit of both, OP didn’t mention a species but a group, but it does makes sense to me that the later and larger species would eventually converge on that second body shape. Hydrodynamics have a pretty heavy hand in evolutionary pressure. From the early large fish to the whales we have today, large pelagic species will adopt that shape over time.
Edit - I’ll add that “it should look like” line of thinking is core to the older Linnaeus classification system, and while it was often correct, genetics in modern taxonomy has shown us there are many wild outliers to the “it should look like its relatives” theory!
Whales don’t look much like their terrestrial relatives though
Whales don't look like water-borne horses
Ichthyosauria are just dolphins, everything evolves into crabs via carcinization. Evolution finds body plans and repeats them. To extrapolate on this, the human body plan is the most unique to evolve in millions of years
From what I've heard, they shouldn't be depicted with blubber, and they shouldn't be particularly whale-like.
Why? I thought the understanding was they were likely homeothermic and therefore likely to have insulating fat
They wouldn’t need it in most cases. Late Cretaceous oceans could be sweltering, especially the shallow seas which mosasaurs would often inhabit. Blubber wouldn’t be necessary for insulation in many parts of the world.
Their fossils have been found in polar regions which would have been cool to cold even in the late Cretaceous. If you are warm blooded you need insulation even in fairly warm seas.
True, polar species would probably need it. But for other areas, Cretaceous seas weren’t just fairly warm, they were hot. During the thermal maximum equatorial oceans were sweltering, somewhere between 80 and 100 degrees at the surface. Plus it’s not like no blubber means no insulation, body mass alone would help retain heat.
How much of the ocean is equatorial? Tropical cetaceans today still have insulating fat because the optimal body temperature is still higher than the water temperature. There might be a case for saying that water temperatures at the equator were so high in the Cretaceous that it would make having insulation a non issue there specifically but all the large mosasaur species we know of ranged into cooler waters too. Simple fact is that we know all other large marine tetrapods had insulating fat including in the late Cretaceous, both for insulation and to maintain a shape that reduces drag, and though we don’t have direct evidence of it in mosasaurs it seems very likely they, or at least all species that ventured into cooler waters like the big famous ones, did too.
I’m wondering if keeping close to the surface mimics land based reptiles sunning themselves, one could posit they might be migratorial as well, given prey animals often are when following food or when mating seasons start. I really do think the fun is in the not knowing though.
They definitely dived into deeper water at times given some mosasaur fossils show signs of decompression damage. Im not sure where the idea of mosasaurs specifically living in shallow seas comes from, many of them were clearly creatures of the open ocean. I’m sure they were very likely migratorial because almost all species of marine megafauna alive today are and the same reasons why applied then too (even if seasonal temperature changes were less pronounced)
Honestly I don't know, I just heard someone who researches Mosasaurs say it. I think it's because we have no evidence of blubber, but I could be wrong.
I don’t think there is direct fossil evidence of a blubber-like fat layer like there is in ichthyosaurs but the fact that some lived in colder regions and were almost certainly warm blooded means that it is considered that they very likely did
Something about the neck and how the head transitions into the body lol off quite off to me about the top one. Seems very terrestrial lizard inspired and not very hydrodynamic for an aquatic predator.
I think if they flattened out the "hump" and removed the flaps of skin from the neck it would feel better maybe? Rn it kinda just looks like a tegu head was swapped with a "regular" one. Still very beautiful artwork though :)
Hey,
The bottom image was from Saurian, and while it wasa correct at the time, I wouldn't use it as something that is 100% correct. At the time I was advising for that image, the remains were pretty scappy and the 2021 paper was still under review so we had limited knowlege. Now with the recent updates, I prefer Beth Zaiken's version. No clue whats up with that top image, its not bad just not what I would go with.
The bottom one is accurate. Mosasaurs had massive ribs and smooth, whale-like skulls.
Also, Jacobson’s organ is found in many vertebrates, including lizards without forked tongue and even some mammals. It doesn’t necessarily imply a forked tongue, just that it’s got a sense of smell.
Cladistically Mosasaurs have been placed as Toxicoferans alongside either snakes or monitor lizards both of which possess forked tongues. If the forked tongue was an ancestral trait to both monitors and snakes then it would be very likely that Mosasaurs also had them.
I imagine they were like reptilian cetaceans.
I've watched Prehistoric Planet, and until have proof of the contrary that is how mosasaurs looked in my head.
If the monitor theory is correct the top could be more accurate for earlier mosasaurs
However the second is much more likely for later mosasaurs
Both work fine depending on the subspecies. My only gripe would be the tongue sticking out. Would it have been possible in earlier mosasaurs? Very likely but with the way the top one has been sculpted it seems very out of place. I would assume that mosasaurs would periodically open their mouths to taste sea water like modern lizards taste the air but full on tongue out for the larger species, doubt it (but not ruling it out)
Streamlined and blubbery, and the more derived they are the more pronounced the hypocercal tail fin ought to be
I don't know enough about the subject to really comment, but I have heard someone who studies Mosasaurs say that they probably didn't have blubber.
My point is, there's going to be some kinda soft tissue that's smoothing out the margins between sections of anatomy, because there's simply too much adaptive pressure to streamline those contours. It might not be blubber-blubber, but I'm putting my money on smooth mosasaurs.
With feathers bro