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Post by creature386 on Jun 23, 2013 1:16:58 GMT 5
I don't think we can predict that, as they are extinct. For example their birth rate is not known, which is important in finding out, wether an animal is a K or R strategist.
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Post by Grey on Jun 23, 2013 1:28:32 GMT 5
About mosasaurs by Mike Everhart :  |
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Post by coherentsheaf on Jun 23, 2013 1:38:16 GMT 5
What about Pliosaurs or Ichthyosaurs in that regard? are they K or R? Given the size of the offspring, Plesiosaurs were probably K strategists. Ichthyosaurs seem to have had relatively many babies each time. |
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Post by Grey on Jun 23, 2013 23:55:13 GMT 5
Mike Everhart about mosasaurs :   |
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Post by Grey on Jun 28, 2013 21:37:21 GMT 5
Quote fom McHenry's thesis :
In palaeobiology, body size is one of the principal predicators of the ecological options available to a species (Meers 2003). The data presented here suggests that pliosaurid and brachaucheniid pliosaurs dominated the apex predator guild from the Callovian to the Turonian, with a body size of under 10–11 tonnes for much of this time, but with the largest pliosaurs reaching up to 20 tonnes in the Kimmeridgian and perhaps the Callovian.
This pattern should be placed within a macroevolutionary context. Pliosaurids and brachaucheniids were not, on average, noticeably the largest marine carnivore groups of the Mesozoic. The larger species of a related group, the Lower Jurassic rhomaleosaurids, reached 1-10 tonnes (although nearer the lower end of that scale). The ichthyosaurs Cymbospondylus (Middle Triassic) and Temnodontosaurus (Early Jurassic) were carnivores in the 1–10 tonne range [by comparing reported body lengths from McGowan (1991) with length–weight data for balaenopterids]. By comparison of TL with modern crocodilians, the largest mosasaurs Tylosaurus and Mosasaurus (Late Cretaceous) may have weighed up to 30 tonnes, although given the likely ‘eel-like’ body form of these taxa this must be considered a maximum estimate and a range of 10–15 tonnes is perhaps more likely. The largest Mesozoic marine reptile of all was the Late Triassic Shonisaurus, which reached 21 m and perhaps 40–50 tonnes, although adults of this taxon was edentulous and were presumably teuthivores rather than carnivores (Nicholls and Manabe 2004). Other than Shonisaurus, and the hypothesised mega-pliosaurs, all the marine reptiles of the Mesozoic were less than 20 tonnes and the majority of apex carnivores appear to have been between 1–10 tonnes.
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Post by theropod on Jun 28, 2013 21:50:39 GMT 5
I had overlooked the weight figure for Shastasaurus before. Sounds very high for the slender body shape of this taxon.
On the other hand, he doesn't seem to include the lower Jurassic mega-Ichthyosaurs or Himalayasaurus; in any case those would ahve deserved a mention but they are not very well-known. I'm agreed with the rest.
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Post by Grey on Jun 28, 2013 22:25:25 GMT 5
I had overlooked the weight figure for Shastasaurus before. Sounds very high for the slender body shape of this taxon. On the other hand, he doesn't seem to include the lower Jurassic mega-Ichthyosaurs or Himalayasaurus; in any case those would ahve deserved a mention but they are not very well-known. I'm agreed with the rest. Shastasaurus was slimmed (and renamed) after the thesis release. No solid datas are known of the others ichthyosaurs so... |
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Post by theropod on Feb 28, 2014 21:53:03 GMT 5
Yes I am talking about Himalayasaurus: mygeologypage.ucdavis.edu/motani/pdf/Motanietal1999a.pdfBut Himalayasaurus is probably smaller tha the temnodontosaur relative from MC Gowan's paper. I have seen the fossil remains of complete Temnodontosaurus in the Stuttgard paleontological museum and it has a pretty deep body. If isometric scaling suggests 14-16m for the largest similar remains as MCGowan indicated, these are probably the largest marie reptiles. Awfully little published though. I agree. The only issue to this I see is the mention in the paper about Thalattoarchon, where they consider Himalayosaurus estimate of 15 m as "poorly constrained" and remark that Himalayosaurus dental elements are not much larger than Thalattoarchon's. Now the later estimate of 8.6 m was itself considered as clearly conservative. Now if isometric scaling is good enough, that's potentially the largest, heaviest, marine reptile to date, though I'd like to know how much may have weighed sikanniensis. Direct comparison of dental remains is not reliable either. Himalayasaurus has axial and appendicular elements larger than in Shonisaurus, which is definitely much longer than 8.6m. The only question, how bulky was it? |
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Post by Grey on Feb 28, 2014 22:12:31 GMT 5
Himalayasaurus is suggested to ba shastasaurid. As far as I know these are not tyically bulky built beasts.
"The exact quote was : Himalayasasaurus must have been larger than Thalattoarchon,
but the published estimate of a body length of 15 m (16) is poorly
constrained. With a crown height of close to 6 cm, the teeth of
Himalayasaurus are only slightly taller than those of Thalattoarchon
with a body length of >8.6 m."
There was also an additionnal data where they showed trends of tooth sizes in ichthyosaurs. That teeht is size is not that reliable does not mean it is unreliable at all.
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Post by Grey on Feb 28, 2014 22:29:49 GMT 5
theropod: No idea about the mass. I culd do a guestimate but that is probably not good enough. grey: Regarding Thalatarchon: I dont know and the paper does not give much detail. If tooth size is the only material compared, then I think this is not a reasoable estimate, as tooth size is not the best proxy. Hymalayasaurus remains are as big as or bigger than the largest Shonisaurus remains, which it is closely related to. I am looking into the reliability of body size estimates of Shnisaurus. Or that would mean that Thalattoarchon was proportionnaly more macrophagous than Himalaysaurus. There is trend about crown height and body size among icithyosaurs. www.pnas.org/content/110/4/1393/F3.large.jpg |
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Post by theropod on Feb 28, 2014 23:52:16 GMT 5
That there is a trend does not mean it is a better predictor than vertebral and flipper size, both are bigger than in Shonisaurus. If Greg Paul’s skeletal and this one? from the University of Berkeley aren’t totally inaccurate, shonisaurus is not a serpentine animal like Shastasaurus. One would expect Himalayasaurus to be of a similar lenght, albeit probably with a shorter snout. |
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Post by Grey on Mar 1, 2014 0:04:02 GMT 5
At least in the cases of pliosaurs, flipper have been actually known to be poor predictors of body size. The trend only suggests that 15 m estimate is not that certain either. Without being gracile, Shonisaurus is now reported to not have been as bulky as many depictions still indicate. The centra for S.sikanniensis are reported to be about the same width or diameter as S. popularis, but as being longer which gives rise to it being a longer animal. www.oceansofkansas.com/ichthyosaur.htmlWhat I get here is that popularis was not deeper bodied than sikanniensis which was simply more elongated. |
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Post by creature386 on Mar 1, 2014 0:49:42 GMT 5
Himalayasaurus is suggested to ba shastasaurid. As far as I know these are not tyically bulky built beasts. "The exact quote was : Himalayasasaurus must have been larger than Thalattoarchon, but the published estimate of a body length of 15 m (16) is poorly constrained. With a crown height of close to 6 cm, the teeth of Himalayasaurus are only slightly taller than those of Thalattoarchon with a body length of >8.6 m." There was also an additionnal data where they showed trends of tooth sizes in ichthyosaurs. That teeht is size is not that reliable does not mean it is unreliable at all. Given that Thalattoarchon was likely more of a macropredator than Himalayasasaurus, it is (IMO) very well possible that it had proportionally a lot larger teeth. It is good to point out that the size is poorly constrained, but I don't think comparing the teeth of two animals with likely very different feeding habits proves a lot. |
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Post by Grey on Mar 1, 2014 1:08:04 GMT 5
What is your reference to argue they had such differents feeding habits ? I was only suggesting this.
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Post by creature386 on Mar 1, 2014 1:41:32 GMT 5
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