“Measurements of bones from its hind leg and foreleg revealed that the animal was 65 tons, and still growing when it died in the Patagonian hills of Argentina about 77 million years ago.”
Scientists seem to keep finding larger and larger dinosaurs. There has to be a physical limitation to their size though. What’s the approximate upper limit for land-animal body mass? How much bigger could they get?
Depends on your environment. Are you allowed to increase atmospheric oxygen? Because in the Jurassic oxygen and CO2 levels were higher than today. That means more oxygen for large creatures to breathe, and higher plant productivity to support larger animals.
Bring a Brachiosaur to today’s ecosystems and it would be gasping for air, and would starve to death because its digestive system wouldn’t be adapted to present-day plants.
I have no idea how they can claim that that’s the heaviest dinosaur to ever live.* Wikipedia lists atleastfivedinosaurs with greater masses; including one that is twice the weight. It’s an exceptional find in terms of completeness, and it’s a huge dinosaur, but it’s not breaking any records.
Huge dinosaurs keep on being discovered because paleontologists know that big dinosaurs get more press and publicity, and thus have an incentive to inflate estimates and focus on bigger dinosaurs. It’s the same reason that we hear about the cure for cancer every other day; it’s how to keep the money flowing in.
Also, Dreadnoughtus is a bastardization of Latin, even by the lax standards of academic Latin.
actually, I do know how. They claim that all of the other, larger dinosaurs are irrelevant because there aren’t enough bones, which seems like a nice way to shit on other researchers’ work.
The article notes that these bounds are likely underestimates as larger animals likely have adaptations that allow for larger size and cannot be accounted for by scaling up smaller models.
For reference, the largest known dinosaur has a mass of 122 metric tons, though this somewhat speculative as the bones were lost in the late 1800s.
At what point do issues such as circulation and transportation of oxygen to tissues become relevant? I know that the latter renders infeasible the mega insects that we visualised in 50s sci-fi movies.
This paper (which focuses on sauropods and how/why some of them were able to have gotten so large, but can also be extrapolated to any large terrestrial animal) discusses some of the constraints which must be addressed for extreme gigantism. It doesn’t necessarily address the question of maximum size, but it does discuss the many issues with which a very large animal must contend.
I don’t think so. The upper limit for arthropods, if I understand their physiology correctly, is based on their respiration, and limits them to much smaller sizes than vertebrates, in general.
It’s not that an animal can’t be as big as the ants in “Them,” it’s that ants can’t scale up to that size with the same proportions. I don’t know about circulation and oxygen, but their legs simply wouldn’t hold up their body weight.
There’s a lot of focus on the structural integrity/strength of a large animal’s body, but for a long time I’ve wondered about fluid mechanics. Pressure at the bottom of a static column of liquid is proportional to the column’s height. In addition to the problem of moving blood through a humungous network of vessels, you’d also have the problem of blood pressure in the lower extremities being much higher than in the upper extremities. For an animal 33 feet tall, the blood pressure at the bottom of its feet will be about 15 psi greater than whatever the pressure is in its head. Compare this with human blood pressure, typically ~2 psi at the upper arm.
You’d also experience massive fluctuations in pressure as you move a limb up or down, which is extremely important in the animal’s brain. Example, if you (a human being) do a handstand, the blood pressure inside your head rises by about 2.5 psi. Taller animals have it even worse. ISTR that giraffes have specially adapted blood vessels in their necks to keep the pressure in their head from skyrocketing when the bend down to drink water. (note that whales don’t have this problem because regardless of their orientation, the external water pressure against each part of their body is very closely matched to the internal blood pressure at that same depth below the surface of the ocean; whales can be gigantic and not give a damn whether they’re head-up, level, or head-down).
So for a land animal to be extremely large, blood vessel walls need to be much thicker than ours are in order to accomodate potentially very large pressures (even if those pressures are transient, as when stooping to drink ground water). Even capillaries would need to be thick-walled, lest they rupture on a regular basis. In addition to limiting O2 transfer, I expect the biological cost for constructing/maintaining such a vessel network might get pretty large.
I’m at a loss to estimate an upper size limit, but surely the circulatory system is a determining factor.
Insects have a simple breathing mechanism that relies on passive diffusion of gases through holes in each segment and internal tubes to deliver the air to cells. Some larger ones pump the abdomens to move air in and out, but the there is a limit to its efficiency. They have to keep the distance from the outside amosphere short to their cells short, which limits their size.
Here is the giant Weta, the worlds biggest insect weighing in at 71g.
Animals and Fish have a more advanced active respiration system that is energy intensive. Insects are limited by design.
Side question: how do they know it was still growing when they only have fossils? It says “bone growing cells will morph” in the article but there aren’t any left to look at.
Photosynthesis (which I assume is what you’re using to infer higher plant productivity) uses carbon dioxide but is competitively inhibited by oxygen, so having higher levels of both (O2 and CO2) wouldn’t necessarily give you higher productivity. It would depend on the balance between them, and also on temperature (high temperature promotes oxygenation relative to carboxylation, so oxygen becomes more of a ‘problem’.)
Oxygen also has other negative effects on plants (and at high enough levels, for animals as well), due to its tendency to form extremely reactive species (superoxides, etc.). I don’t know exactly what the levels were in the Jurassic (I’m vaguely recalling someone telling me 35%), but more of a good thing isn’t always better.
They know there were titanosaurs bigger than Dreadnoughtus; what they don’t know is how much bigger. What’s unique about the Dreadnoughtus holotype is that they can be sure it’s mass falls into a fairly narrow range. With the larger sauropods, estimates can vary by a factor of two, which isn’t much more than an informed guess.