Frequently Asked Dinosaur Question 2 and 3: How long did a dinosaur live and how fast did they grow?

(Massospondylus, Owen, 1854)

In regards to the first question, not much is known about how old individual dinosaurs lived for but estimates have been made. It is likely that dinosaurs did not have a long life-span. For example, the oldest known tyrannosaur was 28 and the oldest sauropod was 38 (Erickson et al., 2004). Reasons for such low life expectancies have been proposed as high predation on young individuals and fierce sexual competition for old (Erickson et al., 2006). These ages were based on growth rings on the dinosaur's bones.

(Triceratops, Marsh, 1889)

In regards to the second question, there has been a lot of research conducted on the growth rates of dinosaurs. Why? Because it can help to answer another question, namely were dinosaurs warm- or cold-blooded. This is based on the idea that warm-blooded or endothermic animals grow faster than cold-blooded or ectothermic ones. Dinosaurs were initially born in quite small eggs, with even the largest only being the size of a basketball (Carpenter et al., 1994). Through the numerous studies conducted in this area, it would appear that, compared to other reptiles, dinosaurs grew much faster. However, compared to mammals and birds, it is dependant on size. When comparing similarly sized animals, dinosaurs under 220 g grew slower than marsupials. Dinosaurs between 1-20 kg grew at the same rate as marsupials but slower than precocial birds (those able to run around from birth). Dinosaurs between 100-1000 kg grew faster than marsupials, at the same rate as precocial birds but slower than placental mammals. Dinosaurs between 1500-2500 kg grew at the same rate as most placental mammals (except whales) but slower than altricial birds (those that are born helpless). Finally, dinosaurs over 2500 kg grew faster than placental mammals, at the same rate as whales but still slower than altricial birds (if you scaled them up) (Erickson et al., 2001, Curry, 1999).

(Growth curves of four tyrannosaurids from Erickson et al., 2004)

Some studies have looked at individual dinosaurs. For example Erickson et al (2004) and Horner and Padian (2004) looked at Tyrannosaurus rex (Osborn, 1905). These studies showed that Tyrannosaurus exhibited a teenage growth spurt, just like human teenagers do. I wonder if Tyrannosaurus teenagers developed attitude problems as well? Anyway, I digress. Tyrannosaurus went from around half a ton at age ten to around five tons when they get to twenty. After that they practically stopped growing. However, some herbivorous dinosaurs could grow even faster. For example, the hadrosaur Hypacrosaurus (Brown, 1913) reached its full size of 9.1 m (Lull and Wright, 1942) and 4 tonnes (Horner et al., 2004) at the age of 15 (Cooper et al., 2008). This means (if my maths is correct), Hypacrosaurus grew, on average, 60 cm and 260 kgs a year.

 As can be seen then, dinosaurs lived relatively short lives but they grew very fast. This pattern is typical of warm-blooded animals. We'll look in more detail at this argument at a later date. Next will be the long awaited final part of Tyrannosaurus, looking at its taxonomy and any other interesting things I've missed out.

See also:
More dinosaurs
More about Tyrannosaurus rex

References
Brown, B. (1913) 'A new trachodont dinosaur, Hypacrosaurus, from the Edmonton Cretaceous of Alberta', Bulletin of the American Museum of Natural History, 32, pp. 395-406

Carpenter, K., Hirsch, K. and Horner, J. (1994) 'Introduction', in Carpenter, K., Hirsch, K. and Horner, J. (Eds) Dinosaur Eggs and Babies, Cambridge: Cambridge University Press

Cooper, L., Lee, A., Taper, M., and Horner, J. (2008) 'Relative growth rates of predator and prey dinosaurs reflect effects of predation', Proceedings of the Royal Society B, 275 (1651), pp. 2609-2615

Curry, K. (1999) 'Ontogenetic Histology of Apatosaurus (Dinosauria: Sauropoda): New Insights on Growth Rates and Longevity', Journal of Vertebrate Paleontology, 19 (4), pp. 654-665

Erickson, G., Rogers, K. and Yerby, S. (2001) 'Dinosaurian growth patterns and rapid avian growth rates', Nature, 412 (6845), pp. 429-433

Erickson, G., Makovicky, P., Currie, P., Norell, M., Yerby, S. and Brochu, C. (2004) 'Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs', Nature, 430 (7001), pp. 772-775

Erickson, G., Currie, P., Inouye, B. and Winn, A. (2006) 'Tyrannosaur Life Tables: An Example of Nonavian Dinosaur Population Biology', Science, 313 (5784), pp. 213-217

Horner, J. and Padian, K. (2004) 'Age and growth dynamics of Tyrannosaurus rex' Proceedings of the Royal Society B, 271 (1551), pp. 1875-1880

Horner, J., Weishampel, D. and Forster, C. (2004), 'Hadrosauridae', in Weishampel, D., Dodson, P. and Osmolska, H. (Eds) The Dinosauria (2nd Edition), Berkeley: University of California Press, pp. 438-463

Lull, R. and Wright, N. (1942) 'Hadrosaurian Dinosaurs of North America', Geological Society of America Special Papers, 40, pp. 1-242 

Marsh, O. (1889) 'Notice of gigantic horned Dinosauria from the Cretaceous', American Journal of Science, 3 (38), pp. 173-175

Osborn, H. (1905) 'Tyrannosaurus and other Cretaceous carnivorous dinosaurs', Bulletin of the American Museum of Natural History, 21, pp. 259-265

Owen, R. (1854) Descriptive Catalogue of the Fossil Organic Remains of Reptilia and Pices [sic] Contained in the Museum of the Royal Colleges of Surgeons of England, London: Taylor and Francis