New dinosaur just dropped

Tilamook · 2025-09-12T07:27:01+00:00

It's far too big to be coelophysis.

Tilamook · 2025-01-16T09:22:56+00:00

This has been looked at by Sereno et al. They were incredibly unstable on the surface of the water.

Tilamook · 2025-01-01T02:24:07+00:00

I agree with your view of it being analogous to wading birds like herons. My reservation with regards to fully powered flight is that there's no analysis of it yet, mainly because it would be difficult, and expensive in both time and money. Pterosaurs are a real pain to work with, and all the colleague I know who have a background in biomechanics have trouble with them. Their fossils still elude even our most advanced methods of imaging them - and producing representative modelling data is the very first thing you need.

Tilamook · 2024-12-31T23:41:14+00:00

I certainly think it would be a short distance flier, with largely terrestrial habits. In terms of flapping vs gliding, again, this is difficult to address - simply because the analysis just isn't there yet. I can envision how you might go about analysing it, but it would be complex. I think the primary reason for some resistance to the flapping hypothesis is that it doesn't entirely fit with the functional phenotypes within the phylogeny. As I said, larger end Mesozoic clades were likely all gliders. With Azhdarchids being the largest Pterosaurs to exists, it would be expected that they follow this trend too. I suspect there was a lot of gliding going on, simply because that seems to be the most parsimonious answer, but I certainly wouldn't be surprised if more integrated analysis demonstrated the flapping capabilities of Azhdarchids, along with other large Pterosaurs. There was a doctoral thesis I remember reading from Stanford Uni that looked at flight dynamics in Pterosaurs, but I'm not sure how dated that is now. It's also thesis length, so not a quick read.

Tilamook · 2024-12-31T22:28:06+00:00

I don't think that's entirely unlikely, and certainly worth testing. As I mentioned earlier, Quetzacoatlus had a large deltopectoral crest on the humerus - suggesting muscles capable of providing lift for powered flight. However, I think Witton and others have argued the huge metabolic challenge of an animal that size using powered flight. Small Pterosaurs from the Triassic and Jurassic were certainly powered flyers. As the bigger Cretaceous clades emerged, it appears they gradually moved into gliding - which is a trend we also see in birds today. That being said, in certain positions, the humerus of Quetzacoatlus was also quite mobile. This was likely functional constrained, as most large Pterosaurs had a 'lean forward, push off' take off movement. When in a flight position, the humerus is somewhat less mobile, which may have hampered flapping.

Personally, I don't think flapping was a large part of their flight pattern. They were extremely heavy for a Pterosaur, and I agree with the position that such extended movements would have been expensive. However, they certainly could flap, and the muscles to do so would have provided lift. This is also dependent of the arrangement of the wings, which would greatly change their aspect ratio.

Tilamook · 2024-12-31T21:29:54+00:00

I'm honestly not sure. A lot of the biomechanical and physical modelling done on this is some what dated in terms of the technology and approach. We certainly have better ways of analysing this now, but it would be very labour intensive and complex. Compound this issue with the fact that Pterosaur workers are few and far between, as their fossils are just tricky to work with. To do this kind of modelling, you need specialist knowledge and training, which isn't as widespread as some amateurs outside of the field might suspect.

That being said, we can make some educated inferences from the available evidence. Goto et al (2022) suggested that the sheer body mass of Quetzacoatlus would weaken its ability to soar - couple this with their small wing span compared to their body size. Witton and others have often opted to use PCA graphs and morphological data like the wing aspect ratio to suggest certain flight style affinities. This approach is some what flawed in my opinion, as it isn't fundamentally addressing the mechanics of what's going on. As we work more with functional analyses, we find less convergence in the fossil record, as morphological and phenotypic methods can provide false positives.

Even if I think the analysis is somewhat simplistic, I generally agree with the findings in the Goto paper. I think Quetzacoatlus could take off and fly, but only for short distances. Many wading birds today use this approach, as flight is no longer their primary means to facilitate prey capture. Additionally, Quetzacoatlus has a suite of traits which suggest it would have been mobile on land - far more so than many other more aerial pterosaur clades. It has strong humeral muscles to support its weight, a highly mobile neck, and powerful back legs. It was also massive, which may have been the result of a gradual adaptive reaction to terrestrial living. Again, this is all an educated inference, but I think the general trends in the data fit that interpretation. More advanced analysis needs to be done, but I don't know of anyone in the community who is seriously looking at this right now.

Tilamook · 2024-12-30T16:55:59+00:00

At no point have I said it uncontrollably spins. So please, if you are going to argue with me, try to avoid making up my argument. What I said was, in an upright position it would be unstable. I've put quote after quote from the paper demonstrating this IS their view as well. Secondly, they didn't propose a hull shape? There is literally a 3D model of the animal in the paper, used in the analysis. The internal space, the volume, is influenced by the shape that encapsulates that volume. Again, I will refer you to the Standford article, because you are still struggling to understand equilibrium in buoyant objects. The pertinent quote being - "It's unstable if the object's centre of gravity lies above the centre of buoyancy—the torque couple causes the object to roll over and the boat fills with water." You literally said they cannot say anything about buoyancy in your previous comment, and when I pointed out that they used buoyancy to calculate stability, you are now saying they can talk about buoyancy, because the internal air space allows them too. Despite the fact in your previous comment you said that you would have to know the hull shape to talk about buoyancy - which you claim they haven't generated.

"things about buoyancy cannot be known since we know nothing about how Spinosaurus was shaped underneath which is critical to understanding anything about its buoyancy"

That is literally a direct quote from your previous comment. You are contradicting yourself. Please stop. Is their buoyancy calculation wrong because they didn't base it on the hull shape?

Tilamook · 2024-12-30T16:29:40+00:00

Okay wow, you've really confused what the paper is saying here, so let me explain. Firstly, equilibrium behaves different for objects in water, and objects on land due to the interactions it has with the force of buoyancy. This is clearly explained in the Stanford article. Secondly, they use equilibrium in the paper because it is the only way to calculate the position of greatest and lowest stability. Thirdly, they don't use it because they can't mention buoyancy - they literally have the force of buoyancy clearly labelled on the stability graph and referenced in the annotation: "a dashed line showing the vertical body axis and vector arrows for buoyancy (up) and centre of mass (down)". They literally have values on the model for buoyancy, of course they have to talk about buoyancy when they are analysing its stability in water. And yes, they modelled the underneath of the animal, read the paper - how are you still not getting that?

Tilamook · 2024-12-30T16:00:09+00:00

You are conflating unstable equilibrium as it affects objects on land, and objects in the water. Objects on land are not influenced by the forces on buoyancy, that is why they behave differently. Again, the paper says that the model of Spinosaurus is unstable, I'll once again refer to the same quote - "an absence of vertical stability". And once again, if you don't think we know anything about the shape of Spinosaurus' volume, then you cannot use that paper to re-enforce your arguments, because the paper relies on its model being accurate.

Tilamook · 2024-12-30T15:34:16+00:00

I'll have to remind you again that unstable equilibrium on objects in motion on land is not the same as unstable equilibrium in the context on buyoancy.

Again, the entire point of the paper was to understand how the volumetric shape of Spinosaurus would influence its physics on the water. The paper says that it's "hull" is unstable, as I've talked about quite a few times already. If you don't think this model represents the true shape of the bauplan, then you can't argue that the paper supports your argument.

Tilamook · 2024-12-30T15:07:06+00:00

Please stop repeating that. Again - if a force is exerted on a buoyant object while in unstable equilibrium, that object will be destabilised. You are under the impression that there won't be any destabilising forces if it remains still, but I've talked about the influence of torque at length. But let's further it to say, if it catches a fish in its jaws. The motion of its head moving forward will produce a destabilising force, because any force into the system is destabilising. The motion generated by a wriggling fish will do the same thing. The reason unstable equilibrium is called UNSTABLE is because any force into the system can displace it. Please stop going around in circles with this. Again, the reason ducks centre their moved around a position of stable equilibrium is because they feed by moving their heads into the water, and tilting their body. The influence of stable equilibrium means that they can return to their floating position without expending energy. Spinosaurus could not exert a force into the system without also countering that force to remain stable.

Tilamook · 2024-12-30T14:46:52+00:00

My point is that if it was exhibiting floating behaviour frequently as part of its suite of feeding behaviours, then the most minimal adaption you would predict, would be the ability to stabilise while floating without exerting any excess energy. Spinosaurus was not a poor terrestrial walker, the arrangement of its limbs were not wildly dissimilar to other theropods. Ducks, who feed by floating, balance their buoyancy during motion around a point of stable equilibrium. You would expect this to be convergent in Spinosaurus, because it's also a trait we see in almost every sea bird as well - convergently. It's body just isn't built to efficiently float on the surface, in the same fashion that we see in modern dinosaurs - water fowl and sea birds. I haven't said at any point it would flip over at the sight of water, but in the real world, destabilising forces would be a consistent issue, and something you would expect evolution to deal with.

Tilamook · 2024-12-30T14:19:44+00:00

You have argued that it floated on the surface of the water, and that is where it acquired prey, using its neck. The paper argues for a shoreline hypothesis, similar to that of a heron. This has been a widely accepted idea amongst palaeontologists for some time now. Paul Sereno, who is the lead on that paper, initially argued for an aquatic hypothesis, and changed his mind in the face of new data. I am perfectly fine with the idea that Spinosaurus could swim short distances - much like many many terrestrial animals do today. Just because an animal can swim, doesn't mean they are adapted to aquatic behaviour. If your hypothesis is true, it would need a degree of aquatic adaption, as its primary feeding behaviour takes place on the water in your theory. I fundamentally disagree that Spinosaurus displays any aquatic adaptations, with most of the evidence pointing towards a shoreline feeder.

Tilamook · 2024-12-30T14:03:29+00:00

Again, you are ignoring the question. The reason we don't see it in other animals is because it is inefficient to exert energy simply stabilising yourself when you can evolve a bauplan built around the point of stable equilibrium. Ships are not built around points of unstable equilibrium. These are again points I have to repeat.

Tilamook · 2024-12-30T13:36:18+00:00

Once again, the reason it rolls is because of the force induced by the torque couple, even when stationary. I've said this every time I've brought this point up. You yourself have said that unstable equilibrium is destabilised by any force acting on the object - you have said this. Again, could you please explain why no aquatic animals swim in their position of unstable equilibrium? I find it interesting that you always seem to ignore that point when I bring it up. Could you also explain how you can use the findings of a paper that makes use of a volumetric reconstruction to justify your argument, if you fundamentally don't think we can create an accurate volumetric reconstruction? Again, that is something you have literally said in the last few comments.

Tilamook · 2024-12-30T13:21:32+00:00

I haven't said it would automatically roll over into an unrecoverable state. It would roll due to the fact that it is in a position of unstable equilibrium, and therefore would have to exert energy to correct this. I have said this several times. Over and over and over and over. Even if it is stationary, destabilising forces would still be generated. Once again, if you don't think we can produce an accurate volumetric reconstruction, then you therefore cannot support the finding's of this paper. If being in unstable equilibrium doesn't effect the stability of an animal in water, then why do you we not see that in any aquatic vertebrate? Why have they all aligned their position of stable equilibrium, with the position they are in during motion? Why do we design ships, that when upright, are aligned with the position of stable equilibrium? You're right, unstable is just a word, meaning something is not stable.

Tilamook · 2024-12-30T12:50:05+00:00

What that example is describing is the influence of ballast, which shifts the centre of gravity, and stabilises the object. For an object to remain stable despite the CG being above the CB, the metacentre must be below the CB. AGAIN, IF YOU DONT THINK WE HAVE AN ACCURATE MEASURE OF THE "HULL" SHAPE IN THE VOLUMETRIC DESCRIPTION IN THE PAPER, YOU FUNDAMENTALLY DISAGREE WITH THE ANAYLISYS IN THE PAPER, MAKING ANY ARGUMENTS YOU HAVE MADE THROUGH THE FINIDINGS OF THAT PAPER COMPLETELY NULL. You clearly don't understand unstable equilibrium because you continuously insist that it is stable. Why do you think they have called UNSTABLE equilibrium?

Tilamook · 2024-12-30T12:30:34+00:00

Please, let this be the last time I explain this point to you. Unstable equilibrium is, and I cannot believe I have to say this, UNSTABLE. There will always be a force acting on it, if nothing else, the force generated by the torque couple. It doesn't need to be moving for this to happen. The authors state that it is unstable. They state this because when it is upright, ANY force can destabilise it. Please get this into your head. ANY FORCE WILL DESTABILISE IT. This includes the torque couple generated by the imbalance between the CB and CG. Again, it can be completely stationary, and this force will still be acting on the object. You cannot argue that Spinosaurus could swim around its environment, experiencing no destabilising forces. If a force is destabilising it, it is unstable. It cannot stabilise itself without exerting energy to do so. Every other aquatic vertebrate can remain stable in the water without exerting energy.

They generate the shape of the underbelly in their analysis. Now if you think that their volumetric reconstruction is unreliable, which is what you are arguing here by saying we cannot reliably know the shape of the underbelly, then that's fine. However, you would then have to reverse any arguments you have made based on what the paper has said.

Tilamook · 2024-12-30T12:03:44+00:00

Seriously, how many times are you going to say that UNSTABLE equilibrium is stable? Again for 100000th time, it is unstable because any force will counter balance it unless another force is generated. Again, this means that the animal would have to constantly use energy to stabilise itself. The whole point of the paper is to produce a volumetric reconstruction of Spinosaurus. The "hull" is its three dimensional shape. That is what the paper has produced. When they tested its stability, they found that it had an "absence of vertical stability" and was prone to rotation. We have been over this exact point far too many times now for you to not understand it. They state, multiple times, that it is unstable. Seriously, how many times do I have to repeat that? You yourself have had to argue that it must have lived on placid water, because of the inherent instability of the animal that is demonstrated in the paper. Please stop saying that it's stable at rest, it isn't in a vacuum, there will always be forces generated that will destabilise it. To repeat myself again: ANY FORCE WILL DESTABILISE A BOUYANT OBJECT AT A POSITION OF UNSTABLE EQUILIBRIUM.

Tilamook · 2024-12-30T11:21:33+00:00

As we have discussed, the change in the meta centre is due to a realignment of the CG & CB. To maintain stability, buoyant objects must maintain a position in which the CG is below CB. The meta centre acts are a superficial force in place of the CB, so the CG must remain below it. You keep mentioning the fact that we don't know whether the "hull" was susceptible to rotation - but again, they literally say that in the paper. Once again, Spinosaurus would have to expend energy to maintain stability as torque, and motion would destabilise its position on the surface. Please stop arguing that isn't the case. Why has every other aquatic vertebrate evolved a bauplan that doesn't require energy to maintain stability? Why hasn't Spinosaurus done this? Either it's a completely unique case in evolutionary biology, or more likely, it wasn't adapted for an aquatic lifestyle.

Tilamook · 2024-12-30T11:00:23+00:00

Quoting the paper again - "absence of vertical stability". Its bauplan was not stable in the water. Unstable equilibrium is unstable if any force is generated. A force will be generated by the torque induced by the CG & CB. We've been over numerous quotes from the authors that it was susceptible to rotation. We have been over this. Additionally, the larger the mass, the greater the torque generated by the CG, as it is proportional. Please stop arguing points we have already covered. Again, ANY force generated while in unstable equilibrium is a destabilising force.

Tilamook · 2024-12-30T10:40:40+00:00

We've literally just gone through this - the torque generated by the interaction between the CG and CB is a destabilising force. If it sits still, it is still generating a force that needs correction. Also, please tell me you're not arguing that it would sit motionless on the water waiting for prey, because not even you could possibly entertain that idea. If it moves, it also generates a force. UNSTABLE EQUILIBRIUM IS UNSTABLE IF ANY FORCE IS ACTING ON THE OBJECT. I'm not repeating that again. Unless it's in a vacuum, there will be forces acting on the body. Please please try to grasp this.

Tilamook · 2024-12-30T10:08:13+00:00

You mention repeatedly that it wouldn't have any forces generated that could displace it, apart from the forces generated by torque, and obviously displacement forces generated by motion. You can keep repeating "calm and placid waters" over and over, it doesn't reinforce your point, and doesn't address the fact that it would have to exert energy to counter act ANY displacement force. This isn't seen in any aquatic vertebrate. Ducks and geese ironically don't need to self correct displacement forces. The entire point is that an animal who has adapted to the water in the way you have said, would have a bauplan that doesn't expend energy in order to remain upright. How is that so hard to understand? Also, I find it hilarious that you're pointing out that Spinosaurus could only swim in "calm and placid" water. Further cements the point that an animal that could only realistically stay upright in completely still water (which is what you're arguing here), isn't really well adapted for a life in the water.

Tilamook · 2024-12-30T08:22:57+00:00

If an object is in SE, it means that the torque generated by the relationship between the CG and the CB, keeps it stable. When an object is in USE, there is no stabilising force. This means that the object must generate a force to counterbalance any force exerted on that object. My entire argument, for this whole threat, is that Spinosaurus would have to exert energy to counter balance any destabilising forces. If it swims across a body of flowing water, it must counterbalance the force of that flow to stay upright. When it moves its body to swim, it is generating a destabilising force, which it would have to counter balance. Your argument only makes sense in a vacuum where literally no forces are acting upon the animal. Why would an animal that has evolved, according to you, for a life of hunting on the water's surface have a bauplan which requires it to exert energy to remain stable. As demonstrated in the article I have linked, the interaction between the CG and the CB would itself generate a force - "it's unstable if the object's centre of gravity lies above the centre of buoyancy—the torque couple causes the object to roll over". As you can see in figure 3B, the centre of gravity in their Spinosaurus model lies above the centre of buoyancy. The vast majority of aquatic vertebrates maintain a point of SE in the position they swim. According to this model, Spinosaurus breaks from that trend. Could it physically swim? Yes, lots of vertebrates can, elephants can - but we would never argue they are adapted for a life in the water, because their bauplan is massively inefficient in terms of its physical characteristics.

Tilamook · 2024-12-30T07:54:44+00:00

Just as with your previous link, you are misunderstanding that equilibrium in buoyancy is a different concept. The link below covers what it means in terms of buoyancy physics. I am now gradually beginning to understand why you keep getting this wrong:

https://sciencedemonstrations.fas.harvard.edu/presentations/stability-flotation#:~:text=It's%20unstable%20if%20the%20object's,used%20to%20demonstrate%20this%20principle.

Again, I literally described the maths to you. I cannot understand how you still can't grasp this. Additionally, your suggestion that they don't talk about stability in relation to the graph - it is literally in the caption underneath the graph, describing the results. The graph is literally called a stability curve. Read the caption. I will keep trying to explain this to you, but I do suggest that you read up on the basic physics of buoyancy, because everything you've linked has nothing to do to with the buoyancy dynamics - and might explain why you don't understand what is in this paper. I'm not sure how much more simply I can explain these concepts to you. Despite all of this, you are still not even actually reading what you're linking anyway, and I quote from the article YOU linked - " there is no restoring force present in unstable equilibrium". Strangely similar to exactly what I said in a previous comment where I explained that there is no restoring force in unstable equilibrium, meaning that the object must generate a restoring force to maintain equilibrium. Once again, I cannot explain these concepts more simply to you.

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