雅思阅读材料：＂Horse Dragon,＂ Colossus Dinosaurs Found in Utah

　　相信很多人对恐龙都非常感兴趣，近来在犹他州发现的被称之为Horse Dragon的恐龙十分引人注目，让我们看看究竟这是一种什么样的恐龙，它是如何发现的，它有什么特点？

　　A shield-toothed horse-dragon may sound like a mythical creature, but the newly described dinosaur once roamed the U.S. West, a new study says.

　　The 125-million-year-old herbivore Hippodraco scutodenswhose partial skull and skeleton were unearthed in 2004 in eastern Utahhas a long, low skull like a horses and a mouth filled with shield-shaped teeth.

　　Hippo and draco are Latin for horse and dragon, respectively, while scutum means oblong shield and dens means tooth.

　　Also revealed recently, fossils of another newly described species from the same time period, Iguanacolossus fortis, were found in 2005 not far from Hippodraco.

　　That ponderous beast is named for its relatively large sizeabout 30 feet long, compared with Hippodracos 15 feet , according to the study.

　　Iguanacolossuss teeth resemble those of Iguanodon, a related, 33-foot North American herbivore that likely lived a few million years before Hippodraco.

　　Related: 39;Amazing Dinosaur Trove Discovered in Utah.

　　Both of the newfound dinosaurs are iguanodonts, an extremely successful group of plant-eaters that expanded worldwide during the early Cretaceous period, the study team wrote.

　　Despite their abundance, North American iguanodonts from this period are rare in the fossil recordexcept in one Utah rock formation, which spans about 40 million years and contains fossils of many types of creatures, according to study leader Andrew McDonald, a graduate student at the University of Pennsylvania.

　　Theyre part of this really interesting window into the early Cretaceous thats been emerging in western North America during the past two decades, McDonald said.

　　Theyre filling in another chapter of what will eventually be a complete and intricate story.

　　Iguanodonts: Cows of the Cretaceous

　　Already the new species are causing some shifts in the iguanodont family tree, McDonald said.

　　His team discovered that North American iguanodonts are less closely related to duck-billed dinosaursthe most evolutionarily advanced members of this dinosaur groupthan some European and Asian iguanodonts.