Where are all the British mosasaurs?

[pachy-pleuro-whatnot-odon]

Hi all,

 

While I'm aware that current Cretaceous exposures in Britain are largely restricted to the south and east coasts of the islands (see geological map below; source), significant marine deposition is said to have taken place across much of Great Britain from the Aptian onward (source).

 

 

As such - and especially considering the richness of the record of the marine ecosystem during the Jurassic- one would expect an abundance of marine reptile remains to be known from British Late Cretaceous sediments as well, the epitome of which, of course, would be the mosasaurs. However, whereas finds of remains of ichthyosaurs and pliosaurs have been reported (see, for instance, Fischer et al. 2014 or Madzia 2016) - albeit from somewhat older strata than from which one might expect mosasaur remains to show up - very little information actually seems to be available as concerns this highly diverse group of marine squamates. When browsing the literature, for example, I've only found limited references to mosasaurs in Britain, most notably in Benton and Spencer's (1995) "Fossil Reptiles of Great Britain", in which the authors (p. 221) observe that

 

Quote

Mosasaurs are patchily represented in the British Chalk, although they are better known in the type Maastrichtian of the Netherlands and in Belgium, in the United States and in parts of north Africa.

 

Some further mentions of mosasaurs are made in this work on pages 264-265, which include lists of marine reptile finds at various locations across the country, as well as page 270, which describes St. James's Pit in Norwich, Norfolk, purportedly "Britain's best mosasaur locality" (ibid.). The pages have been reproduced below for ease of reference:

 

 

Some material is also illustrated and described by Milner in "Fossils of the Chalk, second edition" (Smith and Batten, eds., 2002), but again minimally so:

 

 

Plate 64 3) Leiodon anceps, Campanian, Norwich, Norfolk; 4) Clidastes sp., ?Upper Turonian, Dorking, Surrey; 5, plioplatecarpinae incertae sedis, Upper Chalk, Sussex

Plate 65 1) Clidastes sp., Upper Chalk, Sussex; 5) cf. Tylosaurus, Santonian, Forness Point, east of Margate, Kent

 

Outside of that, over the past couple of years I've only bumped into some loose specimens here and there being offered at auction sites, such as the below batch of alleged mosasaur teeth from Worcestershire, purportedly once part of the prominent Gregory, Bottley and Lloyd collection (at the resolution provided and in their state of preservation it's hard to make out whether they are indeed mosasaurian, however); or the mosasaur lumbar vertebra of unknown origin. It was actually these specimens that first attracted my attention to the existence of British mosasaurs, since so little has been reported on them elsewhere: an internet search doesn't result in anything fruitful, for example, nor have I come across any mosasaur material listed in museum collections.

 

 

 

I would therefore be very interested in hearing what you all make of the above specimens, as well as the apparent paucity of British mosasaur material either in museums or published literature. Is this just the outcome of a collection/research bias, lack of suitable accessible exposures, or could there be another reason...

 

@Praefectus @JohnJ @caterpillar @Welsh Wizard @paulgdls @DE&i and others

Edited September 27, 2021 by pachy-pleuro-whatnot-odon

[caterpillar]

Maybe the temperature of the sea was not good in british cretaceous

[JohnJ]

Questions about water temperatures and depths come to mind.  The shallower waters of the Western Interior Seaway not only provided bountiful food environments, but provided more opportunities for the deposition and burial of its inhabitants.  

 

What were the paleo-environments of British Late Cretaceous deposits?

[Welsh Wizard]

Hi @pachy-pleuro-whatnot-odon.

 

Sorry I can’t help much with your questions and I would’ve pointed you towards Mike Benton’s book.

 

What I can say is that there are some nice U.K. mosasaur pieces out there but they do tend to be from old collections.

 

Nick

[pachy-pleuro-whatnot-odon]

2 hours ago, Welsh Wizard said:

What I can say is that there are some nice U.K. mosasaur pieces out there but they do tend to be from old collections.

 

Thanks, Nick! Makes sense, seeing as much of this material is likely to have been found in old quarries...

 

These pieces you're referring to, are they held in private hands or are those museum specimens? For, part of what I'm so surprised about is that even the MNH in London doesn't seem to list any mosasaur material as part of its collections... That makes it very hard to do comparative research 

[pachy-pleuro-whatnot-odon]

On 9/27/2021 at 5:25 PM, caterpillar said:

Maybe the temperature of the sea was not good in british cretaceous

 

On 9/27/2021 at 5:48 PM, JohnJ said:

Questions about water temperatures and depths come to mind.  The shallower waters of the Western Interior Seaway not only provided bountiful food environments, but provided more opportunities for the deposition and burial of its inhabitants.

 

While I agree that water temperature and depth influence prey and thereby predator populations, I doubt this is a sufficient explanation of the British situation. For one, although species presence amongst mosasaurids is known to vary by palaeolatitude, mosasaurs have been reported from all areas across the globe, including places with high latitudes, such as Antarctica (Martin and Crame, 2006), Sweden, Canada, Argentina, New Zealand and others (source). If we look at the reconstructed palaeogeographical location of the UK as of the early Aptian, shown on Scotese's maps below, it becomes clear that its location is well within the palaeolatitudinal belt from within which mosasaur remains have been recovered. In fact, for most of the Cretaceous, the UK (though particularly the southern part) is located in much the same palaeobiogeographical range as both the Netherlands and Belgium, from which extensive amounts of mosasaur material are known.

 

Early Aptian (Early Cretaceous)

 

Late Albian (Late Cretaceous)

 

Turonian (Late Cretaceous)

 

Early Campanian (Late Cretaceous)

 

Maastrichtian (Late Cretaceous)

 

On 9/27/2021 at 5:48 PM, JohnJ said:

What were the paleo-environments of British Late Cretaceous deposits?

 

I wouldn't know, to be honest. But to judge from the above maps and the description on Wikipedia, conditions wouldn't have been all that different from those in either the Low Countries (the Netherlands, Belgium) or of the Western Interior Seaway at the time: a shallow marine environment - albeit one less pelagic than in the Netherlands, for instance.

 

Overall, though, I don't think the palaeobiogeographical conditions provide us with any clues as to why mosasaurs from Britain are so much rarer than those from across the Channel. As such, I suspect the difference may lie in local variations of depositional and preservational conditions, as well as sampling biases.

[JohnJ]

1 hour ago, pachy-pleuro-whatnot-odon said:

I suspect the difference may lie in local variations of depositional and preservational conditions, as well as sampling biases.

 

Did the suspected "depositional and preservational conditions" impact other, contemporary vertebrate fossils?

 

I'm not sure how sampling bias comes in to play, unless it is available exposures of the correct strata.

[Notidanodon]

If I remember correctly the Ik chalk is a much deeper water deposit than the ones in Central Europe? Not entirely sure though

[pachy-pleuro-whatnot-odon]

Just read your way of telling mosasaur from crocodile vertebrae in this thread, @jpc. And while I fully agree with the notion underlying it, I hadn't thought about the length of the posterior convex articulation surface of mosasaur and crocodile vertebrae as being diagnostic between the two clades before. Seen in this light, I wonder whether the vertebra I posted above might not actually be of a crocodile (which would greatly reduce the amount of British mosasaur material I'm aware of, but would very much be in line with my presumed misidentification of many if the teeth shown above). May be you have an opinion about this?

[jpc]

the brown vertebra seen from several angles above.. I would call that a croc ... no doubt about it.  The convex end way too bulbous for a mosasaur.  The neural processes also crocish.

[The Amateur Paleontologist]

Sorry I'm late to the party... but I think water depth might play a role when it comes to the rarity of mosasaur remains. See for instance, a lot of the chalk in southern England (e.g. Maastrichtian chalk in Norfolk) was deposited in a rather deep-water setting, probably a few hundred meters deep. This is similar to the chalk deposits in the Maastrichtian of Denmark (Møns Klint) or Germany (Rügen), where mosasaur fossils are exceedingly rare (material restricted to small handfuls of teeth).

Compare with the Maastrichtian type area (Netherlands & Belgium), which represents a 40-50m-deep sea, and where mosasaur fossils are much more frequent.

[Welsh Wizard]

Here is a tooth that was recently found in the chalk in Norfolk, U.K. Identified as a mosasaur tooth.

 

Note, I didn’t find this but it’s been posted on FB. I wasn’t sure how to do a link but if you go on FB and search for Norfolk Mosasaur Tooth then you’ll find it.

 

They do turn up from time to time but very rare.

[pachy-pleuro-whatnot-odon]

On 1/15/2022 at 10:32 AM, Welsh Wizard said:

Note, I didn’t find this but it’s been posted on FB. I wasn’t sure how to do a link but if you go on FB and search for Norfolk Mosasaur Tooth then you’ll find it.

 

I guess this is the post you were referring to...

 

On 1/15/2022 at 10:32 AM, Welsh Wizard said:

Here is a tooth that was recently found in the chalk in Norfolk, U.K. Identified as a mosasaur tooth.

 

 

But, wow, that's spectacular!  That's indeed unmistakably a mosasaur tooth, and by the size and curvature of it, I'd even say a mosasaurine one (though better pictures would be needed to confirm this)! Very interesting morphology too, as it looks very pragmatic with numerous facets, and, as such, not like Mosasaurus hoffmannii known from across the channel (at first glance, rather more like M. lemonnieri, maybe, if a lot more sizeable, or possibly M. beaugei, if its range wouldn't have been so southerly). I think there's still a lot to be gleaned from studying British mosasaur teeth like this, and it's therefore a pity nobody seems to have hunted them down for study yet...

 

Boy, what an incredible find! First time too I've heard about a find like this outside of scientific literature, best photographs I've seen too! Thanks for sharing, Nick! This has got me very excited! 

[Kosmoceras]

There are quite a lot of specimens in museums - here's a pic of some on display in the Sedgwick. The NHM has a load but photos and details of the specimens haven't been uploaded to the online data portal yet. 

[pachy-pleuro-whatnot-odon]

12 hours ago, Kosmoceras said:

There are quite a lot of specimens in museums - here's a pic of some on display in the Sedgwick. The NHM has a load but photos and details of the specimens haven't been uploaded to the online data portal yet. 

 

Oh wow! That's quite the eye opener! Thanks for that!  

 

Haven't ever been to the Sedgwick, but with their abundance of marine reptile material it seems high time I went there...! 

 

I did check the online catalogue of the NHM a while back, though, but as I couldn't find even the smallest reference in their database, I feared the worst. Good to know this isn't the case, though. Would you know whether they've got their mosasaur material on display? In any case, it's been a while since I last was there too...

 

Thanks again, as well as for the wonderful photograph! 

[Kosmoceras]

9 hours ago, pachy-pleuro-whatnot-odon said:

 

Oh wow! That's quite the eye opener! Thanks for that!  

 

Haven't ever been to the Sedgwick, but with their abundance of marine reptile material it seems high time I went there...! 

 

I did check the online catalogue of the NHM a while back, though, but as I couldn't find even the smallest reference in their database, I feared the worst. Good to know this isn't the case, though. Would you know whether they've got their mosasaur material on display? In any case, it's been a while since I last was there too...

 

Thanks again, as well as for the wonderful photograph! 

 

There are a few mosasaur specimens on display at the NHM but not the British material - that's all behind the scenes. 

[pachy-pleuro-whatnot-odon]

4 minutes ago, Kosmoceras said:

There are a few mosasaur specimens on display at the NHM but not the British material - that's all behind the scenes. 

 

Pity! Doubly so since no images are available in their online catalogue either...

[pachy-pleuro-whatnot-odon]

On 10/4/2021 at 6:48 PM, will stevenson said:

If I remember correctly the Ik chalk is a much deeper water deposit than the ones in Central Europe? Not entirely sure though

 

On 12/23/2021 at 3:13 PM, The Amateur Paleontologist said:

Sorry I'm late to the party... but I think water depth might play a role when it comes to the rarity of mosasaur remains. See for instance, a lot of the chalk in southern England (e.g. Maastrichtian chalk in Norfolk) was deposited in a rather deep-water setting, probably a few hundred meters deep. This is similar to the chalk deposits in the Maastrichtian of Denmark (Møns Klint) or Germany (Rügen), where mosasaur fossils are exceedingly rare (material restricted to small handfuls of teeth).

Compare with the Maastrichtian type area (Netherlands & Belgium), which represents a 40-50m-deep sea, and where mosasaur fossils are much more frequent.

 

I had reason to review Christian's presentation on the Møns Klint `Thoracosaurus` (see also), when I noticed a very useful map reconstruction that supports the above arguments on water depth playing a role in the occurrence of mosasaur remains in both the UK and Denmark and Germany. Unfortunately, I couldn't get at the exact map used, but I did find a number of other ones, most of which, however, are included in pay-walled articles. What I could get at, I've attached below:

 

Late Campanian palaeogeography of Europe (Niechwedowicz, Walaszczyk and Barski, 2021)

 

Upper Campanian palaeogeography of Europe (Jurkowska and Świerczewska-Gładysz, 2019)

 

Upper Campanian-Lower Maastrichtian palaeogeography of Europe (Engelke et al., 2017)

 

Maastrichtian palaeogeography of Europe (Jurkowska, Barski and Worobiec, 2019)

 

While these maps clearly show that the Møns Klint `Thoracosaurus` would've been way out of its usual near-shore comfort-zone compared to Thoracosaurus macrorhynchus known from the chalk deposits in the Netherlands and Belgium, none of these shows the accompanying water depths. This is unfortunate, because considering the extents of the near-shore environments around the Welsh Massif (for some reason not reconstructed by Engelke et al. [2017]) and Mid-European Island the distance from there to the UK and Limburg (Belgian/Dutch) chalk deposits doesn't seem to differ too much - although, of course, the absolute distance between land and sea at these respective points is significantly larger in the UK. So, maybe, rather than water depth it could be distance to land that's a factor in occurrence of mosasaur remains?

 

It would also be good to note that, contrary to popular perception, mosasaur/marine reptile remains are also not extremely abundant in the Low Countries, even if their occurrence there is higher than in other parts of Europe.

[rocket]

My experience is, whereever you look in the european campanian mosasaurs are always rare... I know some from german and british sites, only a few have been found in the Hannover-Region (lower and upper campanian), Westphalia (Coesfeld, Beckumer Berge, Stemweder Berg) and south-east britain. Mostly teeth, rarely ribs or vertebrae. I think one of the main problems in the chalk is the preservation of bones. Teeth can be found, rare, but they are. And, you can identify them in the field, bones... 

 

might be interesting for you:

The Mosasaur Fossil Record Through the Lens of Fossil Completeness (whiterose.ac.uk)

pp 76ff, British museums material, lot of the material is british

Edited May 9, 2022 by rocket

[pachy-pleuro-whatnot-odon]

12 hours ago, rocket said:

might be interesting for you:

The Mosasaur Fossil Record Through the Lens of Fossil Completeness (whiterose.ac.uk)

pp 76ff, British museums material, lot of the material is british

 

Thanks! That does sound like a very interesting article. I'll have to find some time to read it

 

12 hours ago, rocket said:

My experience is, whereever you look in the european campanian mosasaurs are always rare...

 

Is it any different for either Santonian or Maastrichtian, then? Because I get the impression the record for mosasaurs in Europe is generally rather scant.

 

On 9/29/2021 at 1:19 AM, pachy-pleuro-whatnot-odon said:

As such, I suspect the difference may lie in local variations of depositional and preservational conditions

 

On 9/29/2021 at 3:22 AM, JohnJ said:

Did the suspected "depositional and preservational conditions" impact other, contemporary vertebrate fossils?

 

12 hours ago, rocket said:

Mostly teeth, rarely ribs or vertebrae. I think one of the main problems in the chalk is the preservation of bones. Teeth can be found, rare, but they are.

 

It is interesting you should mention this preservational bias towards teeth versus bones in the European chalk deposits, as I get the impression that in earlier chalk deposits, like the Cenomanian-age Cambridge Greensand, teeth also greatly outnumber other types of vertebrate remains - though I might be wrong. If true, however, this may be a reflection of the nature of the depositional environment seeing as, while the chalk itself would of course create alkaline conditions suited to the preservation of bone, sandy substrate typically is acidic, and would therefore favour the preservation of teeth over bone. As I believe many of the deposits in which these mosasaur teeth are found,  moreover, generally are not excessively rich in fossils (again, I could be wrong), an absence of a high amount of shell-forming invertebrates might support such a hypothesis. With acidity levels furthermore allowing for local variation, this may also explain why certain areas in certain time periods yield more fossils than others. @Kosmoceras, would you know whether such a hypothesis would hold up at all, whether the underlying assumptions are correct?

[rocket]

In Maastrichtian some skeletons and many teeth are known from NL and Belgium. I digged there many years ago and found parts, myself. Sandy rocks, full of invertebrates.

From santonian some remains are known, I will check my database today. Teeth are known from Gehrden (near Hannover), Weiner Esch (NW-Westfalia, I do not know if they are published, but think so), Gelsenkirchen (unpublished). All are sandy layers, most common fossils are shells and echinoderms, shallow water

[pachy-pleuro-whatnot-odon]

2 minutes ago, rocket said:

In Maastrichtian some skeletons and many teeth are known from NL and Belgium. I digged there many years ago and found parts, myself. Sandy rocks, full of invertebrates.

 

Yeah, I'm familiar with it. I've dug there as a kid, years ago. Never found much except for shells, of course, but they were indeed very abundant. Hence my comment about the potential for local variance in preservational conditions. There also seems to be a lot of fine-grained shell material dispersed throughout the Limburg marl, and may be it'd be possible for buffer out the acidity of the otherwise sandy substrate? I know that's probably a long shot, but it's very surprising that except for at a few locations, teeth far outnumber bone material. That can't all have come from transitory animals, can it?

 

How about the Cenomanian sites you mentioned before? How's the proportion of invertebrates in those deposits? I had a look at Stemweder Berg and it seems there, at least, fossil shells have been found...

 

22 minutes ago, rocket said:

From santonian some remains are known, I will check my database today. Teeth are known from Gehrden (near Hannover), Weiner Esch (NW-Westfalia, I do not know if they are published, but think so), Gelsenkirchen (unpublished). All are sandy layers, most common fossils are shells and echinoderms, shallow water

 

Thanks for checking! That's a lot of useful information already! And what kind of database are you using? Is it a personal database, one from your personal collection, or a research database?

[rocket]

3 hours ago, pachy-pleuro-whatnot-odon said:

 

How about the Cenomanian sites you mentioned before? How's the proportion of invertebrates in those deposits? I had a look at Stemweder Berg and it seems there, at least, fossil shells have been found...

 

 

Its "similar" normally you find more teeth, bones are rares. But, we got skeleton-parts, too, in middle Cenomanian of Westfalia (Ichthyosaurs, see Geologie und Paläontologie in Westfalen (lwl.org), from southern westphalia we got skeleton-parts and teeth (bones are better preserved), from Hannover-Area normally teeth are preserved, bones are rare or hard to see.

 

 

Quote

Thanks for checking! That's a lot of useful information already! And what kind of database are you using? Is it a personal database, one from your personal collection, or a research database?

 

I have my own database, was a researcher for many years and used my own (not always good...) one :-)

[rocket]

Some remains have been found near Anröchte (Haarstang), Bones and teeth.

We digged and worked for a really long time in southern Münsterland Basin, focus Turonian and Cenomanian Sediments and Fossils. Teeth or marine reptiles had been raaaaare, I published some small remains from middle Cenomanian.

Turon-Sediments are nealy empty of this fossils..., if you like you can see the other faunistic elements here: Dortmunder-Beitr-Landeskde_36-37_0247-0340.pdf (zobodat.at)

[The Amateur Paleontologist]

On 5/6/2022 at 1:35 PM, pachy-pleuro-whatnot-odon said:

although, of course, the absolute distance between land and sea at these respective points is significantly larger in the UK. So, maybe, rather than water depth it could be distance to land that's a factor in occurrence of mosasaur remains?

 

Sorry it's been a while I haven't been here, exams have kept me busy..

 

You raise an interesting point about how distance from land might factor into the occurrence of mosasaur remains.. However, I'd still maintain that variation in mosasaur fossil rarity is more tied into water depth. For instance - compare the chalks of two sites in the Danish Basin: Stevns Klint and Møns Klint. Both SK and MK are considered to be from roughly the same paleogeographical distance from the nearest landmass (Fennoscandia). The chalk at the former was deposited at depth ranges of ~100-200m, and the latter was deposited in deeper water ~200-300m (see papers by Jelby et al. 2014, and older literature from Surlyk, Rasmussen..)

At Stevns Klint, mosasaurs are rare but not exceedingly so.. You've got a total of ~20 mosasaur shed teeth from that locality, as well as the partial skeletons from two individuals. At Møns Klint it's a different story: only 6 shed teeth ever found over there, no partial postcrania or anything else. Mosasaur remains are demonstrably more rare in the MK chalk, compared to the slightly shallower-deposited SK chalk.

But who knows, honestly? It could be a combination of those two, or more factors! Also, I think it would be a good idea to introduce into this discussion the aspect of collecting bias, which undoubtedly skewers our data