Largest mosasaur

[thalattoarchon]

Largest mosasaur specimen as far as I know is Mosasaurus maximus ALMNH PV 988.0018. Dentary bone of this specimen 97.5+7.1=104.6 cm long that give total lenght of lower jaw about 186 cm. Total lenght of animal probably close to 16-18 meters based on Plotosaurus bennisoni, Mosasaurus spp. (both postcranial elements) and Tylosaurus proriger (intervertebral space in largest specimens) measerments.

This is the ALMNH PV 988.0018:

[Grey]

Sept 15, 2018 20:59:58 GMT 5 thalattoarchon said:

Largest mosasaur specimen as far as I know is Mosasaurus maximus ALMNH PV 988.0018. Dentary bone of this specimen 97.5+7.1=104.6 cm long that give total lenght of lower jaw about 186 cm. Total lenght of animal probably close to 16-18 meters based on Plotosaurus bennisoni, Mosasaurus spp. (both postcranial elements) and Tylosaurus proriger (intervertebral space in largest specimens) measerments.

This is the ALMNH PV 988.0018:

Isn't the skull/body ratio outdated ?

All the recent reconstructions (randomdinos) talk about the Grigoriev specimen to have come from a 13 m animal.

[theropod]

Proportions of Plotosaurus and Tylosaurus still don’t even remotely support those kinds of sizes, and they haven’t ever, really.
The good old 10:1 ratio is not even outdated, it was already baseless when it was first published.

In Russell 1967, the ratio between mandible length and total length (curved axial, i.e. including the natural spine curvature and tail fin, that would become even lower) in both illustrated Tylosaurus skeletals is 6.6 and 7.0 respectively, and in the Plotosaurus skeletal it is 7.1. I’m sure we can all do the math that this does not result in a 16-18m animal even given a 1.86m mandible. Around 13m may be realistic, more really is not. I’m not sure what you mean by intervertebral space in this context. As there are articulated skeletons from which measurements can be taken, this is likely already included. If not, add perhaps 10-15% to that, which is still a far cry from 18m.

The problem is that it is so widely cited despite being demonstrably wrong. All it would have taken was one person taking a ruler to one of the many published figures of complete mosasaur skeletons to show this, but admittedly it’s not immediately obvious that this would be necessary since one generally assumes a scientific paper could get their facts straight before being published…apparently not.

–ref:
Russell, D. A. 1967: Systematics and morphology of American mosasaurs (Reptilia, Sauria). Vol. 23. Peabody Museum of Natural History, Yale University.

[thalattoarchon]

Sept 15, 2018 21:07:58 GMT 5 Grey said:

Isn't the skull/body ratio outdated ? All the recent reconstructions (randomdinos) talk about the Grigoriev specimen to have come from a 13 m animal.

I heard about new amateur reconstructions from devinart. If we use proportions of PWNZ3R-Dragon reconstruction for ALMNH PV 988.0018 we can get a ~14.1 meters long animal. If we use proportion of reconstruction by Harry-the-Fox we can get a ~16.3 meters long animal. Not so big, but easily entering in the 10-20 tons weight category even with a most conservative tylosaurus-like shape of the rib cage.

But after discussion with Gripnev in pers., I have several points to say that these reconstructions have problems and looks somewhat inaccuratele. PWNZ3R-Dragon just use two isolated vertebrae of NHMM 006696 from figures with scale bars in Street (2016) paper (not actual measurements) as well as vertebrae of some other specimens to scale the full vertebral column. All gaps (almost full vertebral column) are replaced by vertebrael measurement of Moanasaurus mangahouangae S34-S77, although there are discrepancy at least in the proportions of caudal vertebrae in Moanasaurus and Mosasaurus. He also seems to underestimate the number of caudal vertebrae (21 intermediate caudals as in problematic M. conodon SDSM 452, not 24-25 as observed in M. missouriensis TMP 2012.010.0001 and M. lemonnieri IRSNB 3119). As a final, PWNZ3R-Dragon get a disproportionately short tail even with moderate (n=35) possible number of dorsal vertebrae. And it is not all problems. PWNZ3R-Dragon reconstruction has the another (so far controversial) defect - there are no any space between the vertebrae where must be located intervertebral disks (some little black space between the vertebrae you can see for example on Hartman's skeletals). By the way Mike Everhart estimate the Bunker tylosaur up to 15.8 m long in 2016s Mosasaur meeting based on the probably length of intervertebral discs which can add length up to 2 meters or more according to their personal correspondence with Gripnev. Although Gripnev use a smaller number of vertebrae in its Bunker tylosaur size estimates and get a smaller increase in total length... He get 14.5 meters for Bunker specimen as far as I can remember.


Next Harry-the-Fox fixed problematic short tail of PWNZ3R-Dragon reconstruction using the tail reconstruction of Plotosaurus bennisoni from Lindgren et al. (2007) that have similar number and proportions of caudal vertebrae as M. missouriensis TMP 2012.010.0001 and M. lemonnieri IRSNB 3119 and may be even a closer relative to Mosasaurus hoffmanni/maximus. However, this reconstruction (based mainly on comparison with TMP 2008.036.0001 M. missouriensis) looks to have same problem with spaces between vertebrae because TMP 2008.036.0001 does not seem to have preserved intervertebral discs. Gripnev by comparison with close relatives and scaling from the NHMM 006696 vertebrae get a mean lower jaw-total length ratio for Mosasaurus hoffmanni at 1:8.74, and note that based on Everhart's data about intervertebral discs in Bunker tylosaur the real lower jaw-total length ratio in Mosasaurus hoffmanni/maximus can be easily (and ironically) be close to 1:10 as claimed by Russel (1967)...

[jhg]

Tylosaurus is the largest of all.

[Grey]

Sept 17, 2018 23:02:15 GMT 5 jhg said:

Tylosaurus is the largest of all.

No, the largest from which we have a complete skeleton but fragments strongly suggest Mosasaurus larger and more massive.

[jhg]

Count me surprised.

[thalattoarchon]

Anne Schulp said that NHMM 003892 from Everhart et al. (2016) and NHMM 603092 from Lingham-Soliar (1995) is a two different specimens...

[thalattoarchon]

IRSNB 3119 (Mosasaurus lemonnieri) with long tail (~1/2 of total length) and ~1:10 skull-total length ratio (Dollo, 1892).

[Grey]

I recall the Saurian team, reputed for being rigorous, have included Mosasaurus in their game, in a rather up to date style and 17 m long.

I questionned this on their page 3 years ago and here is what a mosasaur worker (Nathan Van Vranken) responded me :

  

"...17-18m specimens have been discussed at various technical meetings based off of fragmentary material. Mosasaurs could in theory, have gotten to whale sizes at least if the K-Pg never occurred. Isotope data, fragmentary specimens, and modeling supports this. Measurements can get skewed, no one is perfect like the editors. I'm assuming you are basing off the Lingham-Solier material."

I think I will check again this, I remember a guy on carnivora, somewhat fanboyish, but who pointed on that some fragmentary material in Netherlands seems to suggest mandible quite over 2 m long.

[Verdugo]

Jun 28, 2015 16:17:05 GMT 5 theropod said:

Since the version of Blender I got when updating my OS seems to finally sport a reliable volume estimation package for the purpose of 3D-printing, I thought I’d give this a go:



At a straight-line length of 10m this animal would have a mass very close to 3.5t (since its density can be assumed to be similar to water), so yes, roughly similar to allosaurs that have axial lengths in this region, but with a lower volume and higher density. That means at 15m, it would be about 11.7t and so forth.
The largest mosasaur I’m aware of is still the giant quadrate illustrated by Lingham-Soliar. If legit, with a skull length of 1.95m and similar proportions to those in Blaze’s reconstruction, the owner would be about 14.4m long and 10.5t in weight.

I’ve ignored the flippers because I was too lazy to model them accurately (and frankly neither good enough a 3D-modeler myself) and their impact doesn’t seem to be that significant. In real life, they would add a few tens of kilograms (maybe 100+kg in a very large specimen, but not much more than that). My dorsal view is relatively conservative too, so this should be considered a cautious estimate, but I think it could come close to the real mass.

In any case, based on this it would appear that there have been a few significant under- and overestimates in the past, and unless some mosasaurs were way more robust than this, I don’t think any reached the 20t-mark.

However it was more or less a guess, so any suggestions regarding body width or the general dorsal-view morphology would be very welcome.

EDIT: I’ve attached the model and other relevant files.

EDIT-II: Slight update of image and a correction pertaining to my background image, model ended up being scaled 7cm too small, (9.93m instead of 10m, now amended).

Where did you get the dorsal view for Tylosaurus though? General tunniform shape just sounds a bit 'generic'. I suppose it's based on shark but then what types?

Anyway, i guess it would be fairly appropriate for Tylosaurinae Mosasaur but what about Mosasaurus? Wouldn't they be more bulky than this? You know, barrel chest description.

[theropod]

I didn’t get it from anywhere, dorsal view images of mosasaur skeletons don’t appear to be available, and for obvious morphological reasons, sharks are not really an option (sharks tend to have very broad jaw structure, mosasaurs have a long, relatively narrow skull, correspondingly, sharks tend to have their widest point at or near the head and gills, for thunniform marine reptiles it tends to be somewhere in the ribcage).
In that case, I worked from the dorsal view of the skull, and made the assumption the body would be widest in the ribcage and be about 1 m wide at the widest point. That assumption really was just as arbitrary as it sounds, it simply seemed about right.

This hjust happens to still seem fairly reasonable though, perhaps a bit conservative, as looking at numerous skeletons since then, the rib cages in mosasaurs and ichthyosaurs tend to be just slightly narrower (as restored in this case) than they are tall.

I’ve since simplified my models a bit by modelling the cross-section of most of the body as circular where I had no reference for the width, and applying a correction factor (i.e. flattening it bilaterally afterwards).

For example, here is a model based on Scott Hartman’s Tylosaurus pembinensis, also scaled to 10 m tip-tip length (the original skeletal, the mesh is a few cm shorter due to the subsurf algorithm applied to it, which generates the round cross-section but also rounds off the tips of the snout and tail a bit, but the weight approximation should be good this way):

The volume is in m³. This is assuming circular cross-sections for most of the body (only the fin is flattened, because realism).

You can now play around with this. If you think the torso should be 2/3 as wide as it is deep, you can multiply that by 2/3=0.667. etc.

I’ve previously proposed, based on this photo→ that 0.85 may be a good correction factor. Which would give us about 4 t at 10 m.

I recall doing another mosasaur model some time in between those, but I don’t remember what exactly I based it on or what the results were, but presumably it came out fairly similar as well, otherwise I would probably remember.

[Verdugo]

Thanks Theropod, that's actually pretty cool.

How about this very popular Mosasaurus skeletal drawing on Deviant Art?



I suppose it's no longer accurate or that we should just stick to more 'official' source just to be safe?

Anyway for what it's worth, Lingham-Soliar 1995 has a drawing and some descriptions of M.hoffmanni ribs cage:

Only fragments of ribs are preserved in IRSNB R26
although two complete ribs are present in Mr R.
Garcet's specimen of Mosasaurush offmanni. Unusually,
each is deeply curved, forming an almost perfect
semicircle (restored, figure 18), comparatively much
shallower in the gigantic Hainosauru(sL ingham-Soliar
1992a) and in Plotosauru(sC amp 1942). The proximal
ends are broad, distal ends slightly flattened, and a
groove runs along the length of each rib. These are
clearly posterior thoracic ribs, judging from the
enormous curvature, which probably met at the
narrowest end of the sternum (ster). Furthermore, in
anterior thoracic ribs the connections with the sternum
would have been extensively cartilaginous, as in for
example, Platecarpusp, resumably to facilitate breathing
movements and thoracic collapse at depth

Supposed to be posterior ribs but how posterior is not clear. I did some pixel measurement (low resolution) and got the correction factor ~0.93

[theropod]

^I’m wondering whether I have actually done a model based on that that I didn’t save, because I do have a screenshot of one that looks a lot like it. Sadly no volume measurement though. But I recall discussing the specimen with Broly on DA a few years ago, and I think its weight came up.

[theropod]

Oh yes, turns out I did:
www.deviantart.com/spinoinwonderland/art/Mosasaurus-hoffmanni-712779730
www.deviantart.com/comments/1/712779730/4684828570



I assumed a width 2/3 the body depth though, which in hindsight appears too low by quite a margin. Excellent find on the ribs. Since the sternum is still in the picture, this should be roughly representative of the deepest and widest portion of the chest.

As broly points out, the skeletal would correspond to roughly 12.5 m TL for the Penza specimen with a 170 cm mandible, which would mean 7.2 t based on my model, but if we correct the width (.93/.667) we actually get 10 t. Quite impressive.