Today Tom Hübner takes us through his recent paper on the bone histology of Dysalotosaurs. This little ornithopod is a close relative of Dryosaurus (pictured here) but unlike the US Dryosaurus, comes from the famous Tendaguru beds of Tanzania. This is a great piece of work to see for me as Tom started this work for this PhD thesis in Munich while I was there and so I know the long hours and hard work Tom put into this and it’s great to see it come to fruition.
Many of you might know it already that I finally got a rather long paper on the bone histology of a small ornithopod dinosaur (Dysalotosaurus) published in PLoS ONE. 29 pages sounds like a lot but I wanted to break with tradition a bit to publish only as brief a paper as possible. This had something to do with the beginnings of my studies on bone histology because most papers at that time restricted the information to the most necessary facts which was quite difficult to follow and reconstruct. Without the personal help of ‘experts’ I never would have understood all that. Another reason for the length of the paper is the enormous variation in the microstructure of the bone. Many times I was struck by a completely different type of tissue and it needed some time to identify them and sort them out. That’s because ‘variation’ is also one of the three main topics of the paper.
Anyway, for everyone interested in bone histology, I think it is worth reading [seconded, it's a great review as well as providing new information and analyses]. The most important aspect is the usage of a new type of growth cycles for life history reconstructions which might be applicable for other vertebrates as well, especially when they lack lines of arrested growth (LAGs).
Some might wonder why such a small animal delayed sexual maturity until about its 10th year of life because it should suffer many losses by all types of predators. Well, that’s a good question and difficult to answer. One strategy is definitely the precocial breeding strategy, but the predators could also be the reason for delayed sexual maturity. The animals would not start breeding until they were large and strong enough to withstand the additional stress of mating and breeding, and they still had at least 5 years for reproduction because, according to the size-frequency distribution, only after about 15 years of age decreased their abundance within the herd significantly. Large ornithopods, on the other hand, had the opposite strategy (see Cooper et al. 2008) by outgrowing predators in a short time. Most of them also had altricial breeding behavior. This, and other arguments presented in the paper, could be a good non-phylogenetic difference between small and large ornithopods in general, but there is still much do to before this can be a strongly supported theory. As always: “More fossils and more studies …”.
Constructive criticism is always welcome, so don’t hesitate to post them. I’m still not at all too old to change my mind. Well, this is science – nobody can learn something new without knowing where the mistakes are.
As this is in PLoS ONE, the paper is freely available here.
Hübner TR (2012) Bone Histology in Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia) – Variation, Growth, and Implications. PLoS ONE 7(1): e29958. doi:10.1371/journal.pone.0029958