Sander P Martin, Mateus Octávio, Laven Thomas, Knötschke Nils
Institute of Paleontology, University of Bonn, Nussallee 8, D-53115 Bonn, Germany.
Nature. 2006 Jun 8;441(7094):739-41. doi: 10.1038/nature04633.
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.
蜥脚类恐龙是有史以来生活在陆地上的最大动物，至少在三个谱系中具有真正巨大的形态。成年体重小于五吨的小型物种非常罕见，小型蜥脚类恐龙骨骼通常代表幼体。在此我们描述了一种新的小型基础巨鼻龙类蜥脚类恐龙，霍尔格欧洲龙（Europasaurus holgeri），属名及种名均为新拟。基于骨骼组织学，我们表明它是一个侏儒物种。这些化石，包括精美的头骨材料，来自德国北部的启莫里阶海相地层，记录了超过11个个体的蜥脚类恐龙，全长1.7至6.2米。部分骨骼和孤立骨骼之间的形态重叠将所有材料与同一个新分类单元联系起来。股骨和胫骨的皮质组织学表明，标本内部的大小差异是由于不同的个体发育阶段造成的，从幼体到成年个体。这些小恐龙一定生活在下萨克森盆地周围的一个大岛屿上。与大型蜥脚类恐龙的长骨组织学比较表明，这种岛屿侏儒物种是通过其较大祖先的生长速度下降而进化而来的。
