[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

*Europasaurus holgeri* in tomorrow's Nature

P. Martin Sander, Octávio Mateus, Thomas Laven & Nils Knötschke: Bone histology indicates insular dwarfism in a new Late Jurassic sauropod dinosaur, Nature 441, 739 -- 741 (8 June 2006)

Abstract (refs removed): "Sauropod dinosaurs were the largest animals ever to inhabit the land, with truly gigantic forms in at least three lineages. Small species with an adult body mass less than five tonnes are very rare, and small sauropod bones generally represent juveniles. Here we describe a new diminutive species of basal macronarian sauropod, *Europasaurus holgeri* gen. et sp. nov., and on the basis of bone histology we show it to have been a dwarf species. The fossils, including excellent skull material, come from Kimmeridgian marine beds of northern Germany and record more than 11 individuals of sauropods 1.7 to 6.2 m in total body length. Morphological overlap between partial skeletons and isolated bones links all material to the same new taxon. Cortical histology of femora and tibiae indicates that size differences within the specimens are due to different ontogenetic stages, from juveniles to fully grown individuals. The little dinosaurs must have lived on one of the large islands around the Lower Saxony basin. Comparison with the long-bone histology of large-bodied sauropods suggests that the island dwarf species evolved through a decrease in growth rate from its larger ancestor."

For the skull shape, imagine *Brachiosaurus* with a shorter snout and a nasal bridge that rises above the level of the skull roof.

The 6.2 m specimen is adult as shown by its external fundamental system, but "must have died soon after reaching full size". It has 3 LAGs (in the investigated distal femur anyway).

The supplementary information contains the following phylogeny (matrix modified from the Sauropoda chapter of The Dinosauria II) with bootstrap values:

                    |  `--*Cedarosaurus*
                             `--"higher Titanosauria" (an OTU)

Interesting position for *Lapparentosaurus*...

The name Titanosauromorpha crops up a few times. Its meaning is not explained.

A few papers are cited that I haven't seen but should get... somehow...