Size of internal organs of giant sauropods

[Vladimír Socha]

Good day!

Interesting question is also how big were internal organs of giant sauropods - lungs, heart, stomach etc. I know that Hanns-Christian Gunga published two studies in 1999 and 2008 about organs of Brachiosaurus (Giraffatitan) brancai weighing 38 000 kg and with a body volume of 48 m3. Its stomach was estimated to weight almost 2.5 tonnes (and could accomodate about 8.5 tonnes of plant matter at once), heart 198 kg, lungs 386 kg (and volume of almost 3000 l), liver 318 kg, kidney 55 kg, spleen 141 kg, skin 2140 kg, skeleton 5.5 tonnes, muscle mass 17 tonnes, etc. Volume of blood in the whole body was somewhere between 1881 l and 3659 l (in the older, more massive version of body proportions) and also, Giraffatitan had to eat something between 182 to 360 kg of vegetation per day. It's heart was beating at the rate of 14-17 beats per minute. It inhaled 3.5 times per minute on average and normally would inhale about 50 litres of air per minute. During a hot sunny day, if this animal was still wet, about 567 kg of water would evaporate from its skin. Systemic arterial blood pressures reached 600 to 800 mmHg at the heart of this sauropod. There are many other interesting data in these studies.

OTOH, 1992 study from the Columbia University claimed that the fully grown Diplodocus with its long neck would have required 1.6 ton heart. I would like to know, if there are any newer, more up-to-date estimates?

BTW - where did they get those sizes and shapes of T. rex organs in the show T. rex autopsy? According to this documentary, the heart of a fully grown T. rex was 75 x 50 x 50 cm ("like a Mini-Fridge"); stomach was about 1 m tall ("and could fit a 4 year old"); liver was 90 cm long; and ovaries were 75 x 40 x 40 cm. Interesting numbers, but based on some scientific reasearch or just completely made up for the documentary? (Link)

References:

Gunga, Hanns-Christian & Kirsch, K. & Rittweger, J. & Röcker, L. & Clarke, Andrew & Albertz, J. & Wiedemann, Albert & Mokry, S. & Suthau, T. & Wehr, A. & Heinrich, Wolf-Dieter & Schultze, Hans-Peter. (1999). Body size and body volume distribution in two sauropods from the Upper Jurassic of Tendaguru (Tanzania). Fossil Record. 2. 10.5194/fr-2-91-1999. 

Seymour, R. S.; Lillywhite, H. B. (2000). Hearts, neck posture and metabolic intensity of sauropod dinosaurs. Proceedings of the Biological Sciences. 267 (1455): 1883-1887.

Gunga, H.-C., Suthau, T., Bellmann, A., Stoinski, S., Friedrich, A., Trippel, T., Kirsch, K. and Hellwich, O. (2008). A new body mass estimation of Brachiosaurus brancai Janensch, 1914 mounted and exhibited at the Museum of Natural History (Berlin, Germany). Fossil Record. 11: 33-38.

Seymour, Roger S. (2016). Cardiovascular Physiology of Dinosaurs. Physiology. 31: 430-441.

[Mike Taylor]

Lots of interesting questions here, and those Gunga et al. papers are begging for a follow-up. (I wish I had the time to work on this properly myself, but I really don't.)

Some oddities in the numbers you report from those papers:

* The stomach could accommodate 8.5 tonnes of plant matter but the animal only ate 182 to 360 kg of vegetation per day. That would mean the stomach could hold all the food ingested across 23–46 days. That seems ... unlikely?

* It inhaled 3.5 times per minute on average and normally would inhale about 50 litres of air per minute, which would mean 14 litres of oxygen per inhalation, so that the 3000 litre lung volume could hold 210 inhalations. Again, something feels off here.

* It's ingesting 182 to 360 kg of vegetation per day, but losing 567 kg of water through evaporation. So it's drinking 1.6–3.1 times as much water as it's eating food. Not impossible, but maybe surprising. (It would be interesting to know the food/water ratios of extant animals)

All in all, something's not right here. The Gunga et al. papers were important first steps into this kind of physiological quantification, but as I said very much overdue to revisiting.

-- Mike

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[Mike Habib]

A lot of things to unpack with regard to visceral anatomy in sauropods, for sure, with the upshot being that we really don’t understand organ scaling very well, especially as regards gigantism. Early estimates of organ sizes in baleen whales (example: heart size in blue whales) turned out to be way off (falsified by dissection of beached animals).

Musculoskeletal scaling is better understood, but still far from mastered - visceral scaling is comparatively under-explored. 

Regarding giant hearts, incidentally, I get more or less the correct answer for whales using a power scaling model. However, everything I’ve seen in the literature to date is a force-stress model.

Cheers,

—Mike H.

Michael B. Habib, MS PhD

Research Associate, Dinosaur Institute
LA County Museum of Natural History
900 W Exposition Blvd. Los Angeles, 90007

Adjunct Professor, Biology

College of the Canyons

26455 Rockwell Canyon Rd, Santa Clarita, CA 91355

michae...@canyons.edu

biology...@gmail.com
+1 (443) 280-0181

On Jul 17, 2025, at 3:11 AM, Mike Taylor <saur...@gmail.com> wrote:



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