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Post by Grey on Mar 20, 2018 13:50:41 GMT 5
creature386 you can post it too. Here I compare estimates of the Livyatan holotype using the Physeter specimens in Lambert 2010 supplementary data. The calculation for each individual is the same that Lambert et al. used with the Zygophyseter specimen. Physeter BL - Physeter CLB / Physeter BZW = X X(Livyatan BZW) + Livyatan CBL = Livyatan BL For the males Physeter : 16.15 m 11.62 m 13.87 m 13.77 m 14.68 m 13.55 m 14.88 m 15.51 m 14.81 m Average : 14.31 m, for a range of 11.62 m to 16.15 m. Some suggests the 11.62 m estimate is based on an outlier (oddly proportioned Physeter), which results in a range of 13.55 to 16.15 m, which results in an average of 14.65 m. For the females : 13.69 m 14.76 m 13.93 m 14.70 m 13.93 m For an average of 14.20 m. Similar to the males even tough I'd favor males based estimates because of their larger size. So I'm even inclined to suggest a more stable size range of 14.65 m (based on the average from adult male Physeter) to 17.53 m (based on the upper estimate of Zygophyseter). Here I compare Otodus megalodon estimates of the Yorktown associated dentition using adult great white sharks specimens dentitions listed in Leder et al. 2016 and their calculations. Note the parameters and methods involved are similar to those used in Livyatan. GWS TL / GWS upper dentition width = X X( megalodon upper dentition width) = megalodon TL 17.80 m 15.62 m/16.22 m (both side of the dentition) 17 m/16.95 m 15.42 m/15.11 m 20.27 m/20.59 m 20.16 m /19.92 m 16.59 m 18 m 18 m 18.27 18.77 The range is 15.11 m to 20.59 m, not excluding the outliers. The average TL for the Yorktown dentition based on adult white sharks dentitions (>4 m) is 17.79 m. In short, dentition size compared with GWS indicates the Yorktown dentition comes from an approx. 18 m megalodon. So, the average size based on various adult white sharks dentitions for the Yorktown adult megalodon is slightly larger than the upper estimate of Livyatan based on Zygophyseter. At least, the maths based on those similar methods (sperm whale skull width / white sharks dentition width) suggest this. Now, note the crown width of the largest upper anterior of the Yorktown dentition is 108.5 mm. The crown width of Hubbell's largest tooth is 134 mm (source : Hubbell private communication). Conservatively, this method suggests 18 m might not be an extraordinarily rare occurence for megalodon. For an up to date summary of meg size research, I advise to read this : theworldofanimals.proboards.com/post/30265
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Post by elosha11 on Mar 20, 2018 19:28:42 GMT 5
Grey, great responses, and really applaud your professionalism in dealing with Sam1's ad hominem attacks. He's a smart, articulate guy in a lot of ways, but don't know why he has to jump to insults at the drop of a hat. From his latest responses, I think he's even grudgingly acknowledging the validity of your arguments. Whenever I have some time, I'll try to drop in a few posts on this topic myself and circle back around to GWS v. SW croc.
Creature386, I'm sure you already know this, but just a reminder not to cite the WOA link Grey cites above at the end of his post. I believe that is prohibited on carnivora and I don't want to give Taipan any reason try to ban these quite enjoyable cross-forum debates. Grey, my suggestion would be to copy the entire summary of Meg size research into this thread and ask Creature386 to post it directly.
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Post by Grey on Mar 20, 2018 22:11:48 GMT 5
Slasher wrote
The other situation is true as well. Unsure about what you call the first megalodon ever discovered. The first tooth or the Danish assiciated material ?
If you refer to the later, well there is definitely way larger teeth and presumably centra than this one. Yet it is certainly suggesting something larger than the "average" you supported previously.
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Post by Grey on Mar 20, 2018 22:43:15 GMT 5
Never wrote Bianucci said this. He said that no material (the Chilean/Peruvian teeth) suggests something larger than the holotype.
Most of the teeth available in pictures are not as large or comparable.
So I concluded that tentatively this was suggesting an individual rather on the large side. But I wouldn't claim anything, even if we had three or four complete specimens.
The 200 years quote is inaccurate and caricatural. I'd rather expect you to ask me the source about that.
According to Cailliet, Goldman and Mollet. 2014, once exceeding 70 years, a female may be able to approach the 8 m mark... And the species do reach that age, at least represented by a male.
The problem is there is hardly anything conclusive in science, unless a really abrupt discovery changes everything, i.e. if we discovered one or the other, because of extraordinary allometric proportions was much smaller than expected.
Currently Livyatan upper size is 17.5 m. The calculations of the Yorktown dentition suggest this individual could go anywhere between 15 and 20 m, and there are much larger teeth than in this set...
So, cautiously, available evidence suggest megalodon was larger.
Of course it can change anytime.
It wouldn't be surprising the shark could grow larger. As Farlow 1993. wrote being presumably a less active mesotherm than its endotherm mammal predatory counterparts, the shark was able to grow larger with the same food source and quantity. Note however, as suggested in Ferrón 2017, Figure 2, that Livyatan was without a doubt more active (Ferrón suggests as well Livyatan less heavy than the shark but there are some inaccuracies in his table, like the Basilosaurus and Shonisaurus proportions and weights...).
Another reason is the cartilaginous skeleton, cheaper to build than a bony one and so easier to grow large.
About the Beaumaris tooth, note the smallest mandibular teeth described in Lambert 2016 is 31.5 cm so I don't think it supports a super-Livyatan.
I'm interested but a bit skeptical in the argument of the wear facets regarding the Beaumaris tooth. Fitzgerald is working on it so hopefully the paper will say more.
But I guess it would be interesting to ask him about.
Livyatan and megalodon are extraordinary organisms. It is incredible that such large superpredatory life forms, preying on multi-tons prey items by themselves were able to grow that large and to evolve at all.
So far, never macropredatory shark and tetrapods have ever evolved that large in the history of life. If there was one larger than the other by a small margin ultimately does not count.
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Post by creature386 on Mar 21, 2018 1:54:54 GMT 5
Creature386, I'm sure you already know this, but just a reminder not to cite the WOA link Grey cites above at the end of his post. I believe that is prohibited on carnivora and I don't want to give Taipan any reason try to ban these quite enjoyable cross-forum debates. Grey, my suggestion would be to copy the entire summary of Meg size research into this thread and ask Creature386 to post it directly. For some reason, I at first thought this was referring to a link I've already accidentally posted on Carnivora after pasting the text…Anyway, I plan to simply copy the linked post. |
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Post by Grey on Mar 21, 2018 15:06:52 GMT 5
Leder 2016 explains well the issues about Pimiento. The other link I posted previously as well. When for the same dentition, the size suggested by the individual crowns give an absurd range of 12 to 45 m, it is natural to question its accuracy. It is not wrong, I have studied this situation, it is simply that cetaceans have other advantages as well and a particularly advantageous evolutionary context. Microphagous cetaceans grow up to around 30 m, microphagous sharks up to around 20 m. It appears that the ability to operate in cold waters where the planktoon is naturally much more abundant is the first advantage that allowed the cetaceans to grow larger than any microphagous shark. The baleens appear to be a serious advantage to collect huge quantity of filtered waters. There is a study that explains that for some biological reasons, marine reptiles couldn't evolve baleen at all and thus were never able to grow as large as any balaenopterid, despite the marine reptiles being endotherms and lunged organisms as well. Another reason is that the modern oceans have never been as cold. Cold allows planktoon to develop. Modern baleen whales simply benefit of unique biological advantages (baleens), ability to forage in cold waters (the whale shark is a tropical species) and to have evolved in an era that sees the highest proportions of planktoon possible. There is a reason why baleen whales were much smaller during the Miocene, the global marine temperatures were higher, the genus were more numerous and the predatory pressures higher. Other than that, all the other statements are false. The orca has been equaled and outsized by several macropredatory sharks (Otodus, Parotodus, Cardabiodon...) in history while few predatory marine reptiles actually rival it in weight. The sperm whale has an exclusive niche that allows it to be unrivaled in it. It is an almost exclusive teuthophagous. No shark has a comparable lifestyle so no shark can be compared. The fact is that less metabolic active taxa need slightly less food to grow. Megalodon had this, a cheaper skeleton to build, and being a generalist carnivore in the most diverse marine megafauna in history. That's definitely an interesting case. Fitzgerald implied it might be comparable in size to Livyatan though we'll see what the study says, new material has been found in the region earlier this year. The estimates based on Physeter directly implies that for the same length, they had the same skull width. The skull width directly implies overall similar body thickness. If the holotype was actually 16-18 m, based on Zygophyseter, it inherently implies a skull width much smaller than compared to a male Physeter of the same length. There is no suggestion that Livyatan for some reasons had to be much bulkier than Physeter, which is already among the most massive whales. In fact, Bianucci implied that the animal was more athletic than Physeter and not as bulky, suggesting this artistic reproduction by Alberto Gennari in collaboration with Bianucci to be the most realistic : i.pinimg.com/originals/0b/0b/2f/0b0b2f2afba6ba69eb6523b2dec1fbfa.jpg |
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Post by Grey on Mar 22, 2018 3:59:49 GMT 5
. 10.5 m is not an average size figure, it is a mean figure between neonates, juves, subadults, adults, of different populations...with a certainly inaccurate method. Like I suggested, it is more appropriate to compare the Livyatan holotype with the Danish meg associated remains or the Yorktown one, because, like the Livyatan holotype, they represent adult individuals that achieved their life and growth here. The Danish remains suggest a size range of 14.5-18.5 m following the various published estimations methods. The Yorktown set suggest a size range of 15-20 m according to Leder 2016. Yet, despite the actual evidence of sensibly larger teeth specimens than those in these two specimens, no one implies they were average size. And the same has not to be implied for the Livyatan specimen. Of course there were larger adults but how much of those and how much larger ? So far, none of the isolated teeth found in the same region suggest something larger. Added to the fact that 17.5 m is an upper estimate, based on the upper estimate of Zygophyseter. Making any first substantial specimen of any species automatically an average size specimen is not particularly scientifically rigorous. The truth is for now 17.5 m is the upper size estimate for the Livyatan species, nothing else can be said. Larger adults (than the 13.5-17.5 m holotype) can be expected for Livyatan. Larger adults (than the 15-20 m Yorktown meg) are definitely known. Speculations about larger size don't interest me, datas are my interest. Stephen Godfrey once said me, despite the numerous megalodons teeth found, we're unlilely to have found the largest teeth of the largest individuals ever in their 20 million years of evolutions. So this kind of speculation is endless and can be applied to anything. Let the data speak. Megalodon proportions are hard to establish in detail but they aren't speculation. The few vertebral centra, very similar to Carcharodon according to Gottfried 1995, are indicative of a "robust, fusiform body" (Kent private communication 2012) and Siversson (private communication, 2013) suggests their structure are not indicative of a short, stocky body like the Cretaceous Cardabiodon. Also, Leder 2016 data indicate larger GWS overall to have a proportionally larger body to dentition than in smaller specimens. I agree Livyatan may have had a different hunting style and being an endotherm, was probably more active. You should keep you update about the fossil cetacean research : www.google.fr/amp/s/www.pbs.org/newshour/amp/science/thar-grows-whales-got-big"The fossil samples showed that before 3 million years ago, whales very rarely grew over 30 feet in length. "
"We might imagine that whales just gradually got bigger over time, as if by chance, and perhaps that could explain how these whales became so massive," Slater said in a statement. "But our analyses show that this idea doesn't hold up—the only way that you can explain baleen whales becoming the giants they are today is if something changed in the recent past."Simply because the GWS (and the lamniform in general) is a species in steady decline since a long. Ancestral GWS forms (Pliocene) reached more than 8 m as indicated by large teeth. At a time when the orcas were only 4 m long (O. citonniensis) and less macropredaceous. Orcas grow up to 8 tonnes because they are now the only alpha predators preying on adult giant cetaceans. The GWS is not in position anymore to reach such sizes and never intended to replace the megatooth sharks as multi-tons prey eaters. If you believe sharks are poorly competitive organisms and unable to win an arms race, think about the Cardabiodon lineage which managed to evolve and equal in size the fearsome Kronosaurus in the Early Cretaceous of Australia (Siversson 2013). 10 tonnes of predatory shark that competed and outlived a marine reptile with jaws more powerful than a T. rex. No shark is as specialized in squids as the sperm whale, which is unique in its method to forage. The large size of P. macrocephalus may be attributed to their foraging behavior (Evans & Hindell, 2004; Rice, 1989; Watwood et al., 2006; Whitehead, MacLeod & Rodhouse, 2003). As a known deep-sea diver, P. macrocephalus regularly dives to depths that few other pelagic animals reach (Watwood et al., 2006). Large size confers a benefit in these deep-sea excursions, not only by making the trip less metabolically costly, but also by increasing aerobic capacity and enabling P. macrocephalus to stay submerged for longer periods of time (Watwood et al., 2006; Whitehead, MacLeod & Rodhouse, 2003). Large size also allows P. macrocephalus to feed on many cephalopods during a single dive (Rice, 1989). Lindberg & Pyenson (2007) hypothesized that the wide diversity of cephalopods during the Eocene allowed archaeocetes, primitive cetaceans, to exploit mid- and deep-water cephalopods and subsequently evolve into large odontocetes capable of diving to great depths. The snout has no relevance in this, I look at the skull width/body length ratio. If the holotype was 17.5 m, its skull width was still approx. 2 m. By comparison, a 17.5 m male Physeter is gonna have a skull width of 2.3-2.5 m. This does not suggest a bulkier proportion for Livyatan but a more athletic body, alike the picture link I posted. |
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Post by Grey on Mar 22, 2018 11:20:48 GMT 5
Wolf Eagle remark...
Preying on much smaller whales...that's exactly true as well for Livyatan. Lambert 2010 clearly explained this.
For the good reason that whales were...smaller back then.
Really, this kind of information is easily accessible guys...
I would add Kallal et al. 2012 suggests strongly a juvenile megatooth shark attacked and wounded a large Pliocene balaenopterid.
And Livyatan's average size. And probably we won't know it ever. All what we have is the current data.
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Post by Grey on Mar 22, 2018 15:20:19 GMT 5
To Sam1 comparison. This is certainly a more valuable comparison since you're using here material from actual scientific reproductions and not CGI or artistic reproductions which do not respect precisely the proportions of the species. But you miss the point, the Livyatan has the skull width that corresponds approx. to a 15 m long male sperm whale. The skull width directly implies a similar body mass at the same length. Large axial swimmers (such as Carcharocles, Physeter and Livyatan) must operate at very high Reynolds numbers, which in turn, places strong physical constraints on plausible body morphologies. These constraints are so restrictive that numerous large, axial swimmers (e.g, lamnid sharks, tunas, odontocete whales, ichthyosaurs) have all evolved biomechanically-similar thunniform body morphologies (Webb, 1988; Weihs, 1989; McGowan, 1991; Motani, et al., 1996; Wilga and Lauder, 2004). All of these groups are characterized by a relatively rigid fusiform body with large anterior depth a lunate, high aspect ratio caudal fin with lateral keels on the caudal peduncle, reduced second dorsal and anal fins of the posterior half of the body, a spacing between the first (or only) dorsal fin and caudal fin of about 40% the fork length, and long pectoral fins. Many thunniform swimmers are also at least partially endothermic. So at the same body length, either Physeter, Livyatan and Carcharocles had similar proportions and body mass. I doubt you could assume that shorter skull is reflected in a wider, more robust body. Both Livyatan and modern sperm whales would be operating at exceptionally high Reynolds numbers (50-100 million would be a good guess), and there are VERY tight biomechanical constraints on body shapes for such large, high speed animals. Based purely on physical constraints, I'd expect the two of them to have similar masses at the same body length. This wish of Livyatan being super-bulky comes out from nowhere and I've linked what Bianucci thinks it might be the most likely look of the animal. The estimates based on Zygophyseter directly implies a more athletic build, since it would be even more smaller headed. By the way, there is at least a scientific source that proposes a body mass of 57 tonnes for Livyatan using the 17.5 m estimate. This figure is based on the often reported body mass of a large 18.3 m male Physeter. www.hostingpics.net/viewer.php?id=951676app.png |
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Post by Grey on Mar 22, 2018 16:24:46 GMT 5
Sam1 wrote
Good thing that no one scales megalodon size on tiger shark or porbeagle parameters, which would give 30 m plus figures, or Alopias (closely related) which would give 50 m TL.
Using a closely related, ecologically similar and as large as possible model is of course far more reliable.
There is a good reason why Lambert 2010 didn't use orca as a model.
No one says the sperm whale is the best model, its purpose is to give a cautious eange (Lambert private communication). I persinnally favor the estimates based on Zygophyseter, though this one being itself uncomplete and represented by only one specimen.
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Post by creature386 on Mar 22, 2018 19:55:58 GMT 5
Multi-quoting would make my life much easier…
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Post by Grey on Mar 22, 2018 22:27:44 GMT 5
Thanks, you understand how the mutual research can progress. The argument you have posted that interests me the most is about the wear facets teeth. I'll investigate it and ask to some of the authors mentionned earlier.
It bothers me that you imply I'm not objective. I've investigated a lot about the isolated teeth from Peru and Chile in order to find an indication of larger than the holotype specimen but so far, there is nothing strong.
I'll search about this suggestion.
I didn't. I compared the 17.5 m upper estimate for Livyatan with the Yorktown and Danish megs, which do not represent the biggest remains we have from the megatooth species, albeit quite certainly on the large side. Just like the Livyatan holotype as I suspect. But I don't assume any of them to be an average-sized individual. It is comparing specimens thar are comparable in their state, quality and preservation.
This is exactly why I'm interested to see the Beaumaris tooth study.
However, the other teeth found early 2017 (which are even younger apparently) are similar sized to this one.
In his early comments, Fitzgerald didn't describe it as being likely a small one for the dentition. From its shape, I doubt it is among the tiniest of the original dentition.
But let's wait for more.
I've seen several giants teeth from Chile and Peru and I strongly doubt they belong to the medium-size or small ones. They simply suggest specimens comparable in size to the holotype, which is wow enough.
Actually, while searching about them, I'm more interested in their diameter since apparently the tooth length can be a deceptive mean to predict size in odontocetes (Wood 1982).
A solid evidence of larger specimen would be to find a tooth with a diameter greater than the 122 mm of the most massive uncomplete maxillary tooth in the holotype.
The data I've used in my listing of estimates based on Physeter is from Lambert 2010 supplementary material. Below are the males.
TL Bizygomatic width
1630 170
1440 220
1560 200
1460 190
1000 125
1400 180
1280 160
1150 130
1360 165
1220 165
Note, when I used "skull width" I referred to BZW. I ignore the amount of fat and muscle in order to avoid the speculations and simplify the data.
The skull width I predicted was simply based in the average of the data; approx. a 15 m Physeter has a BZW of 2 m.
Unsure about the skull width, I've pondered about it but never tested it. There is few data about the sperm whale melon height.
But all in all Livyatan had a quite more modest melon and spermaceti chamber so I doubt it would be higher. Most likely similar but needs to be tested. How high is the melon of a 15 m Physeter. And how high was the one for Livyatan. There is few hard data here.
But Pimiento's data is hardly solid as it is demonstrated.
I think the true average adult size of the sample was a bit more than 14 m (a sample filled with calculations errors by itself, the 17.9 m individual being actually 19.6 m...).
According to Gottfried (which used a conservative methodology), a 13.9 m meg could be represented by an immature female. So I don't trust the claim that this size would represent the average for the adults of the species.
Depending of the species, the distribution of body size can be left-skewed or right-skewed. Hence, a species can have a modest average size but being much larger at maximum size.
That's the reason why I prefer to compare specimens with specimens in similar conditions (definitive adults that achieved their lifetime). The point, about megalodon, is when someone finds a very large isolated tooth, the very fact the tooth is isolated indicates the animal behind was still living and growing.
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Post by Grey on Mar 27, 2018 21:47:57 GMT 5
Pimiento did not revise her method, Perez, one of her students, did it. You should rather contact him.
I don't see the reason why the whale should have some massive advantages at the same length. In modern days, I don't see any odontocetes with any significant advantage or dominance against a similar-sized macropredatory shark. The massive, powerful, 600 kg Tursiops avoid the smaller bull shark. The massive toothed, 1-2 tonnes Pseudorca does not appear to be a more powerful, higher in the trophic system predator than the GWS.
At similar length they probably had a similar body mass. Livyatan only has quite larger teeth (most of their size being root) and a longer rostrum, while megalodon had more numerous, sharper, extremely hard teeth in a larger bite radius in a wider head.
At the same length, they avoided each other without much doubt.
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Post by elosha11 on Apr 7, 2018 1:47:59 GMT 5
Hey Creature386, just didn't know if you saw Grey's above post to Sam1 back on March 27. Just in case you want to post it.
Hope to jump on this thread at some point soon myself.
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Post by creature386 on Apr 7, 2018 2:26:19 GMT 5
I haven't seen it.
Thanks for reminding me.
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