Comments on: Dinosaur Reproduction, Not Ancient Gravity, Allowed Super-Sized Sauropods to Evolve

By: Herman Diaz

Herman Diaz — Sun, 31 Mar 2013 19:39:32 +0000

Good summary overall (as usual). There are 3 things that stood out to me, though.

“Although exactly how these dinosaurs processed the massive amounts of plant food they needed is a mystery.”

Based on what I’ve read (although I might’ve missed something newer), the same way prosauropods did (“Once the food was past the mouth, grinding likely took place via gastroliths — which have been found in association with prosauropod skeletons — and by stomach fermention, to judge from their barrel—shaped torsos”: http://www.amazon.com/Dinosaurs-Concise-David-E-Fastovsky/dp/0521282373/ref=la_B001IQZAB4_1_1?ie=UTF8&qid=1364756913&sr=1-1 ).

“Sauropod mothers laid clutches about 10 eggs at a time in small nests, and the embryonic dinosaurs developed in eggs about the size of a large grapefruit.”

Again, based on what I’ve read, they laid “clusters of 15—34 linearly paired eggs” (Same book).

“The fact that all the genera that are contenders for the “largest dinosaur of all time” title – including Argentinosaurus, Supersaurus, and Diplodocus – top out around 100 to 110 feet in length might indicate that these dinosaurs were reaching the anatomical ceiling of how large it was possible for them to get.”

Again, based on what I’ve read, the largest sauropods are estimated to have reached “40 m from the tip of the snout to the tip of the tail” (Same book).

By: Stephen Hurrell

Stephen Hurrell — Wed, 13 Mar 2013 13:47:15 +0000

Thanks for confirming those references. I briefly discussed Hokkanen’s 1985 paper in my 2012 paper about ancient gravity and highlighted how he had also calculated the athletic ability of the largest animal to be so low that, “a mass 10^6 kg allows a running speed of 6 km/h – a man could walk and overtake”. I can’t think of any modern paleontologists that argue that the sauropods were this unathletic. Do you know of any? Your suggestion of air sacs invading the bones to “make the skeletons of these dinosaurs lighter without sacrificing strength” overcomes this objection of low athletic ability but I calculate we would need to reduce sauropods weight by about 50% to explain their large size. This seems a very large void space to account for. How large are the air sacs you are suggesting? But air sacs may only be part of the answer and as you suggest, perhaps a combination of “air sacs and laying lots of little eggs allowed sauropods to grow to large size”.

Also my memory of Economos’s 1981 paper (I can’t find my copy unfortunately) is that he simply assumed that the limit to mammal size must be the largest mammal ever found without outlining why the mammals of today are smaller. Mammals’ size is very interesting. Have you considered writing an article about this? It always seems such a neglected area.

Hopefully many of your thoughts about large size will become clearer when I get hold of a copy of your new book, My Beloved Brontosaurus.

All the best.

Stephen

By: Stephen Hurrell

Stephen Hurrell — Fri, 08 Mar 2013 11:35:45 +0000

Interesting article. Can I check a few references please? When you say that “In a 2011 paper on sauropod gigantism, paleontologist P. Martin Sander and coauthors briefly debunked the proposal that Jurassic gravity was weaker.” Are you talking about the sections that say:
“Gravity also limits body size, and the current gravity constant of 0.981 ms−2 has been proposed to limit body size to 20 t (Economos, 1981) based on a mass estimate for the largest land mammal ever, Paraceratherium (also known as Indricotherium). However, sauropods were much heavier than the largest land mammals, and G¨unther et al. (2002) suggested the upper limit for terrestrial organisms due to gravitational forces to be at least 75 t. Similarly, Hokkanen (1986) calculated that bone strength and muscle forces only become limiting to terrestrial animal size at masses in excess of 100 t.”

“(1) Physical boundary conditions
Although gravity is of overriding importance in determining the bauplan of an organism, we have to assume that there were no secular variations in Earth’s gravity in the Phanerozoic geologic past (Economos, 1981).”

[Yes. That's it. - Brian]

All the best

Stephen

By: Jaideep

Jaideep — Thu, 07 Mar 2013 17:17:15 +0000

Now looking at my pet cockatoo in whole new light. Great article! We can say now sauropods have been up against gravity ever since. I also wonder why there haven’t been any walking-type (like modern hippos) life form of similar gigantism in our oceans; you know with all the water to support such a gait?

By: Mark Robinson

Mark Robinson — Sat, 02 Mar 2013 03:04:50 +0000

@David Esker
Please direct me to your peer-reviewed paper(s) where you delineate the actual evidence for your hypothesis that the Mesozoic atmosphere was substantially “thicker” than today.

Making something up is not doing science no matter how neatly it might resolve whatever problems you think exist. You could make it science by looking for evidence both in support *and* against your idea, than (and this is important) publishing it so that other scientists can review the evidence for themselves.

You should consider getting in contact with Brian J. Ford. He shares your methodology.

By: BJ Nicholls

BJ Nicholls — Fri, 01 Mar 2013 22:34:28 +0000

Kudos to Jose Canseco for having an the science curiosity to think about interesting questions. And to Brian and Matthew for respecting curiosity by providing considerate scientific answers.

By: Adrian D. Thysse

Adrian D. Thysse — Fri, 01 Mar 2013 13:28:41 +0000

Great article. I have strayed from reading your blog regularly in the last few years…my loss.

By: Jordan

Jordan — Fri, 01 Mar 2013 09:56:17 +0000

I really enjoyed reading this article. It was my first time coming to this site. I will have to look for more things you have written. Very interesting

By: Mike Taylor

Mike Taylor — Thu, 28 Feb 2013 08:22:45 +0000

"Sorry dude, but if you want to actually contribute to science then you need to develop your thinking skills rather than just play follow the leader." Well, I don't wish to seem arrogant, but in this field I am one of the leaders. See my publications (all free to read) here. I am afraid your "theory" proposes left-field solutions to problems that are already well understood. And with that, I will leave the last word to you, as I doubt there is much point in prolonging this discussion.

By: David Esker

David Esker — Thu, 28 Feb 2013 03:52:48 +0000

Hi Mike. You start off with the statement “As a matter of fact…” and then you give a link to a paper presenting a dumb hypothesis: long necks produced gigantism. Mike, a hypothesis is not a fact, not even close. Your claim that this solves the paradox of how the dinosaurs grew so large does not even qualify as being ridicules. It’s just stupid. Sorry dude, but if you want to actually contribute to science then you need to develop your thinking skills rather than just play follow the leader.

“Unthinking respect for authority is the greatest enemy of truth.” Albert Einstein