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Island dwarfing for Hateg dinosaurs



From: Ben Creisler bh480@scn.org

In case this paper has not been mentioned yet:

Benton, Michael J., Csiki, Zoltan, Grigorescu, Dan, 
Redelstorff,Ragna, Sander, P. Martin, Stein, Koen, 
Weishampel, David B., Dinosaurs and the island rule: The 
dwarfed dinosaurs from Hateg Island, Palaeogeography 
(2010), doi:10.1016/j.palaeo.2010.01.026



Abstract
Islands are fascinating natural laboratories of evolution. 
One much debated theme among evolutionary ecologists is 
whether there is an ?island rule?, the observation that 
large animals tend to become smaller and small animals 
larger. Franz Nopcsa was the first, in 1914, to suggest 
that the latest Cretaceous dinosaurs from Hateg, Romania 
were an island fauna, based on its low diversity and 
apparently unbalanced composition, and the basal position 
("primitiveness") of many of the included taxa within 
their respective clades. In turn, the small size of the 
taxa compared to their relatives from other landmasses in 
conjunction with the proposed island setting were used to 
support the presence of the island rule and size reduction 
(dwarfing; nanism) among the Hateg dinosaurs. In Nopcsa's 
day, palaeontologists had seen the same phenomenon many 
times in the Pliocene, Pleistocene, and Holocene mammals 
of the Mediterranean islands. Although often quoted as a 
key Mesozoic example of the island rule, the supposedly 
dwarfed Hateg dinosaurs have never been investigated 
thoroughly. Here we review a wealth of new data, from 
tectonics and regional geology to limb proportions and 
dinosaur bone histology, which support Nopcsa's original 
claim of insularity of the Hateg fauna. Current 
evolutionary studies confirm that the island rule applies 
in many, if not all, modern cases, as well as to the 
Mediterranean island mammals. Geological evidence confirms 
that Hateg was probably an island in the Late Cretaceous, 
and phylogenetic, ecological, and bone histological 
evidence shows that at least two of the Hateg dinosaurs, 
the sauropod Magyarosaurus and the ornithopod 
Telmatosaurus, as well as possibly the ornithopod 
Zalmoxes, were dwarfs by progenesis, a form of 
paedomorphosis.