By comparing humeral and femoral robustness (the mid shaft circumferences plotted against length) of Telmatosaurus with Maiasauria, which has one of the best ontogenetic series among "higher" iguanodontian ornithopods, it is seen that the smallest of examples of Telmatosaurus are smaller than nesting Maiasauria and that Telmatosaurus are slightly more robust than Maiasauria of a similar size, the latter being thought of as sub-adult indicating that Telmatosaurus were downsized relative to the ontogenetic trend represented by Maiasauria. (Figure 1)

Juvenile characters of Telmatosaurus

Telmatosaurus is smaller than other basal iguanodontians like Ouranosaurus and Iguanodon bernissartensis and retains the features found in the teeth of the juveniles found in both species. (Weishampel et al, 1993). The maxillary teeth are narrow, diamond shaped and equipped with a single centrally placed ridge which is seen in most juveniles of non-hadrosaurid iguanodontians and similar to the maxillary teeth of more derived hadrosaurids. The dentary teeth however are wider, asymmetrical and have several low ridges. These are also small, but seem to be some sort of intermediate form of other hadrosaurids and basal iguanodontians. They do however resemble the shape of most adult non-hadrosaurid iguanodontians so could be presented as evidence for dwarfing through the process of paedomorphosis.

The bone histology of Telmatosaurus

The primary bone tissue of Telmatosaurus transsylvanicus consists of fibrolamellar bone with reticular primary osteon organization in hatchlings ad lamellar organization in sub-adults (Figure 2: a-b) and adults (Figure 2: c). As seen in Magyarosaurus dacus the fibrolamellar bone matrix of T.transsylvanicus has a strong lamellar component suggest that it too had a slower growth rate.

Artwork: Telmatosaurus transsylvanicus

Kindly provided by Mihai Dumbrava

Literature cited

• Benton M. J., Csiki Z., Grigorescu D., Redelstorff R., Sander P. M., Stein K. and Weishampel D. B., 2010, Dinosaurs and the island rule: The dwarfed dinosaurs from Hateg Island, Palaeogeography, Palaeoclimatology, Palaeoecology, Article in Press
• Weishampel, D.B., Norman, D.B., Grigorescu, D., 1993. Telmatosaurus transsylvanicus from the Late Cretaceous of Romania: the most basal hadrosaurid dinosaur. Palaeontology 36, 361-385.
• Grigorescu, D., Csiki, Z., 2006. Ontogenetic development of Telmatosaurus transsylvanicus (Ornitischia: Hadrosauria) from the Maastrichtian of the Haþeg Basin, Romania - evidence from the limb bones. Hantkeniana 5, 20-26.
• Horner, J.R., deRicqlès, A., Padian, K., 2000. Long bone histology of the hadrosaurid dinosaur Maiasaura peeblesorum: growth dynamics and physiology based on an ontogenetic series of skeletal elements. Journal of Vertebrate Paleontology 20, 115-129.