The truth about Mosasaurus hoffmanni

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The truth about Mosasaurus hoffmanni

Postby CrocodylusNiloticus » Wed May 03, 2017 9:14 am

Hello everyone, I registered in your wonderful forum with the purpose to offer a more correct and scientifically-reliable "version" of Mosasaurus hoffmanni. Specifically, regarding his morphology, ecology and behavior. I apologize in advance for my bad English.

Well, i will begin:
1. Morphology.
1.1. Caudal anatomy.
The tail of Mosasaurus hoffmanni (and other members of the genus) was about 1/2 of the total length. Anatomically tail of Mosasaurus genus was modified in comparison with earlier mosasaurines - it had more pygal (non-chevron-bearing) vertebrae.
The tail fluke of Mosasaurus occupied about 4/10 of all tail leinght and be reversed heterocercal (hypocerca) - I.e. vertebrae extends into the lower lobe of the tail and making it longer. Thus, the tail fluke of the Mosasaur hoffmanni differed from the tail fluke of the Placarpus and not suitable for such fast swimming.
From Lindgren et al. (2011):
Image
1.2. Cranial anatomy.
To describe the cranial anatomy, I'd rather just quote abstrac of papper by Lingham-Soliar (1995):
Many characters of the skull show that M. hoffimanni was among the most advanced mosasaurs. The skull is robustly constructed and is the least kinetic in the Mosasauridae and, with a tightly assembled palatal complex, provided greater cranial stability in this large-headed mosasaur. The cranial musculature is highly modified. The four-bar linkage system of lizards and early mosasaurs is non-functional in M. hoffimanni. The elements of the lower jaw are also more tightly united than in other mosasaurs.
Mosasaurus hoffmanni tooth crowns are divided into several distinct, unique cutting surfaces or prisms. A functional analysis of the marginal teeth shows that they are particularly adapted to powerful bite forces although pterygoidal teeth are small and reduced in importance in ratchet feeding. Moderately large orbits and poorly developed olfactory organs suggest that Mosasaurus hoffmanni was a surface-swimming animal. A relatively lower level of binocular vision than in some other mosasaurs may indicate a somewhat uncomplicated habitat.

In addition, this paper provides excellent reconstruction of the skull and jaws musculature:
Image
Skull of medium-sized (lower jaw ~ 1.5 m) M. hoffmanni:
Image
The lower jaw (and maximum head length) of the Mosasaurus hoffmanni was about 1/10 of the total body length (originally by Russell, 1967), like his closest relative - plotosaurus (Lindgren and Caldwell, 2007). According to some people head was 1/7 of the total body length, as in prognathodon, but there is no evidence for this: cervical vertebrae of prognathodon seem very small compared to the head, not as in mosasaurus. See Prognathodon overtoni by Konishi et al. (2011) and Mosasaurus missouriensis by Konishi et a. (2014).
1.3. Postcranial anatomy (but not caudal).
Very little known about the postcranial anatomy of the Mosasaurus hoffmanni. However, M. hoffmanni had a very massive and durable skeleton, and Lingham-Soliar (1995) leads a sketch of the thoracic ribs, vertebra and
sternum of small individual (the narrowest part of the chest):
Image
M. hoffmanni have large spinous processes of the vertebrae (2.6 times larger than the vertebra). Fins are relatively small, but strong (Lingham-Soliar, 1995).
1.4. Size.
Mosasaurus hoffmanni, without a doubt, was the largest member of mosasaurinae and even mosasauroidea. It is one of the largest marine predators in history, but still not the "largest marine reptile known," as said Lingham-Soliar. The huge Triassic ichthyosaurs (e.g. Shastosaurus) probably exceeded the Mosasaurus hoffmanni in weight and and possibly even in length.
I collected a sample of M. hoffmanni specimens and estimated their sizes:
1. Holotype MNHN AC 9648 - based on the lower jaw constituting 10% of the total body length, the estimated total length is about 13.5 m (Street & Caldwell, 2016; Lingham-Soliar, 1995).
2. NHMM 009002 from the Maastricht Museum of the Netherlands - based on the lower jaw total length is about 16.7 m (Lingham-Soliar, 1995; the future calculations based on fragment size indicates jaw length of 167.36 cm), but not 17.6 m with "about 1.6 m jaw", as stated in the Lingham-Soliar's paper.
3. IRSNB R26 - based on the lower jaw constituting 10% of the total body length, the estimated total length is about 15 m (Lingham-Soliar T., 1995).
4. Plastotype M. hoffmanni YPM - based on the lower jaw constituting 10% of the total body length, the estimated total length is about 12.4 m (Russell, 1967).
5. NJSM 11053 (Mossasaurus maximus, now synonymous with M. hoffmanni) - based on the lower jaw constituting 10% of the total body length, the estimated total length is about 12.4 m (Russell, 1967).
6. Sample YPM 773 (also "M. maximus") - by the height of a quadrate of 200 mm (versus 167 mm in NJSM 11053), the length of the lower jaw estimated as 1473 mm and total body length as about 14.7 m (Russell 1967) . Although, here + -, because the size of the quadrate bone can vary.
7. JMB-0057-99 - based on the lower jaw constituting 10% of the total body length, the estimated total length is about 15 m. The authors indicate the length of the skull at 1.3 m and compare this specimen in size with IRSNB R26 (Bardet & Tunoglu, 2002).
8. A speciemen of M. hoffmanni, mentioned by Dollo (1917, p. 17), based on the lower jaw constituting 10% of the total body length, the estimated total length is about 15 m (Russell, 1967).
9. "Penza mosasaur" (CCMGE 10/2469 and aslo copy PRM 2546) - based on the lower jaw constituting 10% of the total body length, the estimated total length is not less than 17 M (Grigoriev, 2014).
10. "Bemelse Mosasaur" (NHMM 006696) - based on the lower jaw constituting 10% of the total body length, the estimated total length is about 14.4 m or more (Schulp et al., 2006).
11. IRSNB R12 - based on the lower jaw constituting 10% of the total body length, the estimated total length is about 11-12 (Lingham-Soliar, 1995). It was a young animal that grew on 1/3 or 1/2 (Dylan Bastiaans et al., 2014).
12. IRSNB R27 - based on the lower jaw constituting 10% of the total body length, the estimated total length is about 6 m. Perhaps the smallest known M. hoffmanni. Definitely a young animal.
13. IRSNB R25 - based on the lower jaw constituting 10% of the total body length, the estimated total length is about 8 m. Is no doubt that is a young animal.
14. MGGC 21876 - based on the lower jaw constituting 10% of the total body length, the estimated total length is about 14.5 m (Fanti et al., 2013). However, at present it is very difficult to identify this sample as M. hoffmanni. Authors of the description assert that its belonging to this taxon is very unlikely.

Based on this sample, it can be accurately assumed that the length of adult M. hoffmanni averaged about 14-15 meters. Larger (15-17 m) individuals are probably mature males, and smaller (12-13 m) ones are probably females, because in modern monitor lizards females are usually smaller than males, although this is just speculations. Some fragmentary fossils - quadrate NHMM 603092 and humerus TSMHN 11252, indicate that among M. hoffmanni there were individuals larger, possibly with lower jaws over 2 meters.
I do not know with which speciemen can be compared TSMHN 11252. But I know a lot of quadrates of M. hoffmanni. Height of the quadrate of NJSM 11053 is about 16.7 cm, width is 10 cm (Mulder, 1999). MNHN AC 9648 quadrate height is 17 cm, width is 12 cm (Street et al., 2016). IRSNB R26 quadrate height is only about 13 cm, width is 9.2 cm (although in fact the skull of IRSNB R26 is larger than the skull of NJSM 11053 and MNHN AC 9648) (Lingham-Soliar, 1995). In comparison, height of the NHMM 603092 is 26 см, width is about 18.5 cm (Lingham-Soliar, 1995). This allows us to estimate the length of the lower jaw NHMM 603092 and it will be 193-302 cm. I do not believe in the 30-meter mosasaurs and very skeptical to the upper estimate (based on IRSNB R26), but 193-229 cm lower jaw and ~19.3-22.9 m total leinght (based on NJSM 11053 and MNHN AC 9648) seems is quite possible.
Fanti et al. (2013) estimated the weight of the 11 meter mosasaur in 4000 kg. According to the cube-square law, weight of 15 meter M. hoffmanni will be about 10143 kg, weight of 17 meter M. hoffmanni will be about 14765 kg, weight of 20 meter M. hoffmanni will be about 24042 kg, and weight of 23 meter M. hoffmanni will be about 36565 kg.
2. Ecology.
2.1. Feeding.
First i turn to Lingham-Soliar (1995):
Very little is known about the feeding habits of Mosasaurus hoffmanni. Gut contents and coprolites are lacking although an alleged coprolite specimen of M. hoffmanni in Teylers Museum is probably a stomach stone and apparently not even associated. The enormous size of Mosasaurus hoffmanni, and the presence of teeth capable of both crushing and cutting, mean that most animals were potential prey. Further evidence may be gained from other sources. Mosasaurus hofmanni shared its environment with a number of vertebrates including turtles such as the giant Allopleuron hoffmanni and invertebrates such as belemnites. Tooth marks of M. hoffmanni on a scute of A. hoffmanni (Lingham-Soliar 1991 c) and rehealed dentary breaks indicate its savagery and the possibility of male-male fights cannot be ignored. Presumably recuperation from such severe injuries to the jaws would have been rapid, as in crocodiles (Meyer 1984), since they would have made the animal rather vulnerable and feeding difficult. The small size of the pterygoid teeth suggests that they were of only minor importance in ratchet feeding in M. hoffmanni. This is consistent with the reduction of skull mobility. Large pterygoid tooth size may simply have got in the way of prey (cf. the relatively clear palate of plesiosaurs, Taylor & Cruickshank 1993). Nevertheless, firm grip was probably still possible despite a reduced depth of penetration. Compared with for instance Prognathodon and Plioplatecarpus, in which the pterygoids house enormous teeth that almost equal those of the marginal dentition, highly different feeding styles may be inferred.

The teeth of M. hoffmanni have a variety of cutting surfaces, in particular, large serratet carinae. His skull was very powerful, lower jaw is very durable in comparison with other mosasaurs, and jaw musculature resembled that of modern tegu lizards and xenosaurus, which have very powerful bites (bite force per weight as in crocodiles). Jaws can open very widely, but the pterygoid teeth are reduced. And it seems that some mobility of the lower jaw allowed him to sawn the victim, like a hand saw!
Teeth of M. hoffmanni:
Image
Serrated cutting edge on teeth of some Mosasaurus spp. by Poynter (2011):
Image
I again quote Lingham-Soliar (1995):
The head musculature in Mosasaurus hoffmanni had become more differentiated, more powerful and more mechanically effective. These conditions led to greater control of skull and jaw movements. Mosasaurus hoffmanni shows the most advanced form of tooth facetting in marine reptiles; each crown providing numerous cutting or breaking edges.

So, M. hoffmanni had a powerful bite, crushing and cutting teeth, akinetic skull and sawing with movements back and forth heavy lower jaw. In addition, he was not a fast swimmer (see "1.1. Caudal anatomy") and has a poor stereoscopic vision (see "1.2. Cranial anatomy"). We also now know that mosasaurids were warm-blooded and have a fast metabolism, dufficiently primitive Campanian mosasaurs, such as the clidastes, tylosaurus and platecarpus maintained body temperature above the temperature of environment (Harrell et al., 2016). More progressive mosasaurids, such as the M. hoffmanni, may have better thermoregulation mechanisms becouse their fossils are known even from Antarctica. Because of the high metabolism, he required large ammout of food.
Thus, we end up convincing that the well-armed, having poor binocular vision, slowly swimming and having fast metabolism, M. hoffmanni was a "big game hunter" and attacked prey from an ambush (perhaps from the thickets of algae or from the some water depths). M. hoffmanni was also not an obligate scavenger, since he had poorly developed Jacobson's organ (see Lingham-Soliar, 1995). Mosasaurus hoffmanni, apparently, hunted mainly on other marine reptiles, including plesiosaurians, giant sea turtles and even other mosasaurids (including smaller M. hoffmanni). As well in a case with the modern komodo dragons and crocodiles (and also confirmed by some jaws injuries in young M. hoffmanni, IRSNB R25 and IRSNB R27), prey can be larger than the hunter.
A very good description of the hunting behavior of the Mosasaurus hoffmanni I found in this article: http://www.prehistoric-wildlife.com/spe ... aurus.html
Being such a large creature with a heavy build suggests that Mosasaurus had a preference for larger slower prey,? ?quite probably other marine reptiles.? ?Further support for this specialisation and behaviour comes from the side wards facing eyes that meant Mosasaurus had poor stereoscopic vision.? ?A lack of this ability strongly suggests that Mosasaurus did not rely heavily upon gauging distances between itself and prey and as such probably did not rely upon speed to chase down prey over distance.
While some would envision Mosasaurus as a scavenger the fossil evidence also contradicts this as the olfactory bulb? (?the part that processes smells?) ?is one of the most poorly developed areas.? ?While many oceanic predators use smell to detect injured prey for an easy meal,? ?Mosasaurus would have been at a disadvantage to most of these.? ?Perhaps the most likely scenario for Mosasaurus hunting behaviour is one that saw it hanging around the upper ocean and waiting for other marine reptiles to surface for air.? ?At this time they would be at their most vulnerable as they would be in the most lit portion of the water? (?and silhouetted against the light if Mosasaurus was looking up from below?)?,? ?and unable to dive back down? ?as? ?they would drown without? ?a? ?fresh supply of air in their body.? ?Using its tail to provide a quick burst of speed Mosasaurus could launch a sudden attack that if it did not kill the prey,? ?would at least injure it so that Mosasaurus could follow and hound it until it tired.

2.2. Habitat.
Again, just quote Lingham-Soliar (1995):
Russell (1967) described two distinct lineages for mosasaur radiation - clidastoids, shallow water forms, and plioplatecarpines and tylosaurines, deeper water forms -although a greater range of intermediate habitats is now known (Lingham-Soliar 1991 a-c; 1992 a, b). Recent geological and palaeontological evidence (Robaszynski et al. 1985) gives some indications of the environment of Mosasaurus hoffmanni. Previous suggestions that all the Late Cretaceous deposits in the Maastricht area had been laid down on the marine shelf, point to a maximum depth of 200-400 m. In practice the water depth was considerably less, probablywith an average of 40-50 m (reviewed, Lingham-Soliar 1994a). Apparently the Campanian and Maastrichtian deposits in the Limburg area were laid down in nearshore waters with changing temperatures and were rich in vertebrate and invertebrate life (Robaszynski et al. 1985, p. 18). By the later Campanian the composition of the North American mosasaur fauna had changed. Clidastes had disappeared and the tylosaurines were replaced by large mosasaurines e.g. Mosasaurus maximus. In Europe on the other hand there is no evidence of clidastoids (Lingham-Soliar 1994 b). However, the large mosasaurines (e.g. M. hofjmanni) and tylosaurines (e.g. Hainosaurus bernardi) coexisted to the end of the Maastrichtian. Part of the competitive success of European tylosaurines (Lingham-Soliar 1992 a), compared with their North American counterparts, may have been in their higher evolutionary development and an ability to occupy different adaptive zones.

3. Behavior.
3.1. Intraspecific aggression.
Schulp et al. (2006, 2014), Lingham-Soliar (2004) and some other authors detal describe the pathologies of M. hoffmann speciemens, although, a small number of relatively complete fossils very limit the sample. Although a large number of pathologies are also described for other members of the genus Mosasaurus (e.g. Bell & J.E. Martin, 1995) and "infinite" number of them can be found in more well-studied species of mosasaurids. For example, Williston (1904, p. 49) said:
As I have previously remarked, it is certain that all mosasaurs did not die of old age. Indeed, the many hyperostosial mutilations of antemortem origin indicate only too well the fierce struggles the mosasaurs had with the carnivorous enemies of their own and other kinds.

Therefore, obviously, adults and even young individuals of M. hoffmanni be very aggressive towards relatives (and, probably, to other large mosasauids, for example, the skull of IRSNB R12 was probably rammed by Hainosaurus bernardi [Lingham-Soliar, 1998]) and fight for territory, females, hunting ground and even hunted each other.
3.2. Reproduction.
It is proved that even early mosasaurids gave birth to live babies in the open ocean (Field et al., 2015). It is not proven, but it is possible, that some species of mosasaurids still used sheltered nurseries or areas such as shallow water.
However, it is very unlikely that mosasaurids, especially such large ones as the Mosasaurus hoffmanni, cared for their babies. Such behavior is not observed in modern monitor lizards. A large, active animal, requiring a large amount of food, it is very difficult to keep track of small cubs and drive them along.

Finally, I would like to present my reconstruction of Mosasaurus hoffmanni:
Image

Thanks for attention!
In particular, I hope this review will help you to revise the description of the Mosasaurus hoffmanni on this page: http://prehistorickingdom.com/wiki/inde ... Mosasaurus
For example, i think adult M. hoffmanni will be more impressive than 3 stars (especially after the last films like "Jurassic world" :D ), will require more food, will hunt larger animals and require extreme security level.

References:
    *Lingham-Soliar T. (1995), "Anatomy and functional morphology of the largest marine reptile known, Mosasauruhs offmanni (Mosasauridae, Reptilia) from the Upper Cretaceous, Upper Maastrichtian of The Netherlands".
    *Street and Caldwell (2016), "Rediagnosis and redescription of Mosasaurus hoffmannii (Squamata: Mosasauridae) and an assessment of species assigned to the genus Mosasaurus".
    *Bardet and Tunoglu (2002), "The First Mosasaur (Squamata) from the Late Cretaceous of Turkey."
    *Russell D. A. (1967), "Systematics and Morphology of American Mosasaurs".
    *D. V. Grigoriev (2014), "Giant Mosasaurus hoffmanni (Squamata, Mosasauridae) from the Late Cretaceous (Maastrichtian) of Penza, Russia.
    *Federico Fanti, Andrea Cau, Alessandra Negri (2013), "A giant mosasaur (Reptilia, Squamata) with an unusually twisted dentition from the Argille Scagliose Complex (late Campanian) of Northern Italy".
    *Anne S. Schulp, Geert H.I.M. Walenkamp, Paul A.M. Hofman4, Yvonne Stuip5 & Bruce M. Rothschild (2006), "Chronic bone infection in the jaw of Mosasaurus hoffmanni (Squamata).
    *Dylan Bastiaans, John W. M. Jagt, Anne S Schulp (2014), "A Pathological Mosasaur snout from the Type Maastrichtian (SE Netherlands)".
    *Bell, G.L., Jr. & Martin, J.E., 1995. Direct evidence of aggressive intraspecific competition in Mosasaurus conodon (Mosasauridae: Squamata).
    *Poynter Jeremy (2011), "Using dental microwear analysis to predict feeding types in mesozoic marine reptiles".
    *Lingham-Soliar T. (1998), "Unusual death of a Cretaceous giant".
    *Lingham-Soliar T. (2004), "Palaeopathology and injury in the extinct mosasaurs (Lepidosauromorpha, Squamata) and implications for modern reptiles".
    *Takuya Konishi, Michael G. Newbrey, Michael W. Caldwell, (2014), "A small, exquisitely preserved specimen of Mosasaurus missouriensis (Squamata, Mosasauridae) from the upper Campanian of the Bearpaw Formation, western Canada, and the first stomach contents for the genus".
    *Takuya Konishi , Donald Brinkman , Judy A. Massare & Michael W. Caldwell, (2011), "New exceptional specimens of Prognathodon overtoni (Squamata, Mosasauridae) from the upper Campanian of Alberta, Canada, and the systematics and ecology of the genus".
    *Mosasaur Pathology (Mike Everhart). Oceansofkansas.com.
    *Field, D. J., LeBlanc, A., Gau, A., Behlke, A. D. (2015), Pelagic neonatal fossils support viviparity and precocial life history of Cretaceous mosasaurs.
    *Eric W.A. Mulder (199), "Transatlantic latest Cretaceous Mosasaurs (Reptilia, Lacertilia) from the Maastrichtian type area and New Jersey".
Last edited by CrocodylusNiloticus on Sun Sep 03, 2017 5:22 am, edited 7 times in total.
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Re: The truth about Mosasaurus hoffmanni

Postby ProjectMammoth » Wed May 10, 2017 10:42 am

ooh
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Re: The truth about Mosasaurus hoffmanni

Postby NublarRex » Thu May 11, 2017 1:38 pm

Holy shit you put a lot of research into this.
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Re: The truth about Mosasaurus hoffmanni

Postby Jetsnake » Sat May 13, 2017 11:29 am

This is...extraordinary
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Re: The truth about Mosasaurus hoffmanni

Postby DiloRaptor » Sat May 13, 2017 12:06 pm

Wow. This was incredibly written and quite informative. I applaud you.
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