Europasaurus 5468113 223111758 2008-07-02T16:57:36Z 192.165.213.18 hu:Europasaurus {{Taxobox | | name = ''Europasaurus'' | fossil_range = [[Upper Jurassic]] | image = Europasaurus_holgeri_detail.png | image_width = 200px | image_caption = Life restoration of ''Europasaurus holgeri''. | regnum = [[Animal]]ia | phylum = [[Chordate|Chordata]] | classis = [[Reptile|Sauropsida]] | superordo = [[Dinosauria]] | ordo = [[Saurischia]] | subordo = [[Sauropodomorpha]] | unranked_familia = [[Macronaria]] | genus = '''''Europasaurus''''' | species = '''''E. holgeri''''' | binomial = ''Europasaurus holgeri'' | binomial_authority = Mateus, Laven, & Knötschke ''vide'' Sander ''et al.'', 2006 }} '''''Europasaurus''''' <ref name="Sander ''et al.'', 2006">Sander, P. M., Mateus, O., Laven, T., Knötschke, N. 2006. Bone histology indicates insular dwarfism in a new Late Jurassic sauropod dinosaur. ''Nature'' '''441''': 739-741.</ref> is a basal [[macronaria]]n [[sauropod]], a form of [[quadraped]]al [[herbivorous]] [[dinosaur]]. It lived during the Upper [[Jurassic]] ([[Kimmeridgian]]) of northern [[Germany]], and has been identified as an example of [[insular dwarfism]] resulting from the isolation of a sauropod population on an island within the Lower Saxony basin. Remains of both adults and juveniles have been recovered from marine [[carbonate]] beds ("bed 93"), representing more than eleven individuals ranging from 1.7 to 6.2 meters in total body length. The [[genus]] name means "lizard from [[Europe]]" (Europe + [[Greek language|Greek]] ''sauros'' = lizard), and the [[species]] is named in honor of Holger Lüdtke, who discovered the first [[fossils]] of the [[taxa]]. The [[holotype]] specimen (DFMMh/FV 291; Dinosaurier-Freilichtmuseum Münchehagen/Verein zur Förderung der Niedersächsischen Paläontologie) consists of portions of a disarticulated skull, along with [[cervical]] and [[sacral]] [[vertebrae]], derived from a single individual. This specimen and all others referred to the taxon were collected from "bed 93" at the Langenberg quarry, Oker near [[Goslar]], [[Lower Saxony]] (Niedersachsen). == Phylogeny == A [[cladistic]] analysis of ''Europasaurus holgeri'' <ref name="Sander ''et al.'', 2006"/> indicates that the species' dwarfism is a derived characteristic, and that this taxon is a more derived macronarian than ''[[Camarasaurus]]'', and should be regarded as the [[sister group]] of the [[Brachiosauridae]] and all more derived members of the Titanosauriformes. == Dwarfism and Histology == [[Image:Europasaurus skull.JPG|thumb|left|''Europasaurus'' skull]] It has been suggested that the ancestor of ''Europasaurus'' would have "dwarfed rapidly" after immigrating to a paleo-island <ref name="Sander ''et al.'', 2006"/>, as even the largest of these islands in the Lower Saxony basin (a landmass <2,000 square kilometers) would not have possessed sufficient food for a population of large sauropods. Other examples of insular dwarfism among dinosaurs have been cited from the [[Maastrichtian]] (latest [[Cretaceous]]) [[Haţeg Island]] in [[Romania]], namely the sauropod ''[[Magyarosaurus]]''<ref name="Nopsca, 1914">[[Franz Nopcsa|Nopsca, F.]] 1914. Über das Vorkommen der Dinosaurier in Siebenbürgen. ''Ver. Zool. Bot. Ges. Wien.'' '''54''': 12-14.</ref> and the [[hadrosaur]] ''[[Telmatosaurus]]'' <ref name="Weishampel ''et al.'', 1993">Weishampel, D., Norman, D. B. et Grigorescu, D. 1993. ''Telmatosaurus transsylvanicus'' from the Late Cretaceous of Romania: the most basal hadrosaurid dinosaur. ''Palaeontology'' '''36''': 361-385.</ref>. In these two examples, [[paleogeography]] and [[paleoecology]] have been employed to explain the [[evolution]] of new and miniature versions of larger species. These fossils were determined to represent a dwarf species, and not merely juveniles of a large macronarian species, by studying the [[histology]] of the fossil bones. Likewise, by comparing the long-bone histology of a typical large-bodied sauropod, ''Camarasaurus'', [[paleontologist]]s have concluded that the diminutive size of ''Europasaurus'' resulted from a decreased growth rate. This phenomenon is a reversal of the accelerated growth responsible for [[gigantism]] in other sauropod dinosaurs <ref name="Sander ''et al.'', 2006"/>. Dwarfism among macronarians seems especially remarkable as this [[clade]] includes some of the largest known dinosaurs, such as the brachiosaurs ''[[Brachiosaurus]]'' and ''[[Sauroposeidon]]''. == Diagnosis and Comparative Morphology == [[Image:Europasaurus.png|thumb|left|Size comparisons of adult and juvenile ''Europasaurus'' with human for scale.]] ''Europasaurus holgeri'' exhibits the following unambiguous autapomorphic states <ref name="Sander ''et al.'', 2006"/>: "[[nasal]] process of [[premaxilla]]ry projecting anterodorsally; [[medial]] notch is posterior [[Dorsum (biology)|dorsal]] margin of cervical vertebral [[centra]]; [[scapula]]r [[acromion]] with a prominent posterior projection; and [[transverse]] width of [[talus bone|astragalus]] twice its dorsoventral height and anteroposterior width." In comparing ''Europasaurus'' with ''Camarasaurus'' <ref name="Sander ''et al.'', 2006"/>, ''Europasaurus'' differs "in the wing-shaped posterior process of the [[postorbital]] being slightly longer and wider than the anterior process, whereas it is much shorter in ''Camarasaurus''." Other differences include ''Europasaurus''' shorter nasal-[[frontal]] contact and a [[parietal]] bone which is rectangular in posterior view. Unlike ''Camarasaurus'', the neural spines of the presacral vertebrae are undivided. In comparing ''Europasaurus'' with ''Brachiosaurus'' <ref name="Sander ''et al.'', 2006"/>, the former genus differs from the latter by having a shorter muzzle, a [[quadratojugal]] which makes contact with the [[squamosal]], and an anteromedially flattened [[humerus]] possessing unaligned [[proximal]] and [[distal]] [[epiphyses]]. ''Europasaurus'' was also compared with the macronarians ''[[Lusotitan]]'' and ''"[[Cetiosaurus]]" humerocristatus'' and found to be distinct from both those forms. Finally, ''Europasaurus'' can be distinguished from most known members of the Neosauropoda by its very small adult body size. == References == {{reflist}} {{portalpar|Dinosaurs}} [[Category:Dinosaurs of Europe]] [[Category:Jurassic dinosaurs]] [[Category:Sauropods]] [[ca:Europasaure]] [[cs:Europasaurus]] [[de:Europasaurus]] [[es:Europasaurus]] [[it:Europasaurus]] [[lt:Europazauras]] [[hu:Europasaurus]] [[nl:Europasaurus]] [[pl:Europazaur]] [[pt:Europassauro]] [[sk:Europasaurus]] [[zh:歐羅巴龍]]