Vol.24 No.2 2010 Dinosaurs

A Decade of 21st-Century Dinosaur Research at IVPP

Corwin Sullivan* Institute of Vertebrate Paleontology and Paleoanthropology, CAS, Beijing 100044, China

n the first decade of the 21st alongside crocodilians, turtles and their close relatives. Many other century, a larger number of other terrestrial vertebrates. Although features confirm that Guanlong is a Iimportant new dinosaur specimens fossils are relatively sparse in the relatively primitive tyrannosauroid, have come from China than from Shishugou Formation, the Shishugou a status that makes it in some ways any other country. The Institute dinosaurs are of extraordinary more interesting than its larger and of Vertebrate Paleontology and importance because many of them presumably fiercer cousins. Guanlong Paleoanthropology (IVPP) has been represent early, relatively primitive sheds light on the early stages of the at the forefront of the scientific effort members of groups that became evolutionary trajectory that led from to document and analyze these fossils, far more structurally specialized more typical theropods (predatory in collaboration with a wide range and taxonomically diverse in the dinosaurs) to true monstrosities of other institutions in China and subsequent Cretaceous Period. like Tyrannosaurus. However, around the world. Recently discovered The small (about 3 meters in total Guanlong should not be seen only Chinese specimens, described by IVPP body length) Shishugou predatory as a transitional form. It also had researchers and their collaborators, dinosaur Guanlong wucaii (Xu et important features of its own that have shed considerable new light on al., 2006a), discovered in 2002 by a were not shared with more advanced the evolution of several important joint expedition mounted by the IVPP tyrannosauroids, most notably a dinosaur groups and on various and George Washington University striking crest of bone running down aspects of dinosaur biology. Some of in the United States, perfectly the middle of the snout. The name the findings of these studies would exemplifies this pattern. A number of Guanlong is a direct transliteration have seemed even twenty or thirty details of the skeleton, such as fused of the Mandarin pronunciation of the years ago to be closer to the realm of nasal bones in the skull, show that science fiction than paleontological Guanlong is a tyrannosauroid—a reality. member of the group that includes the In the past decade IVPP field infamous Tyrannosaurus and i t s expeditions and research efforts have Asian cousin Tarbosaurus. concentrated on three very different As well as its small dinosaur faunas from different parts of s i z e , h o w e v e r, China. First, in the Xinjiang Uyghur Guanlong lacks Autonomous Region in the extreme the enlarged skull northwest, the Middle and Upper and tiny forelimbs Jurassic rocks of the Shishugou that characterize Skull of the primitive tyrannosauroid dinosaur Guanlong wucaii Formation have yielded a curious Ty r a n n o s a u r u s , from the Jurassic Shishugou Formation of Xinjiang, China. (Photo: assemblage of dinosaurs preserved Tarbosaurus and By courtesy of IVPP)

* Dr. Corwin Sullivan is an associate professor at IVPP. Correspondence should be addressed to him at [email protected].

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characters 冠龙, meaning “crowned research on Shishugou dinosaurs will that appears to have died with its head dragon.” yield additional new species and new tucked under a presumably feathered Other Shishugou taxa excavated inferences about dinosaur evolution. forelimb. and described by IVPP scientists The second area of concentration The majority of the known and their colleagues have also been for IVPP dinosaur workers, the Lower Jehol dinosaurs are small, with many identified as early members of their Cretaceous Jehol Group of Liaoning species measuring less than a meter. respective evolutionary lineages. Province in the northeast, provides an Although there are notable exceptions, Yinlong downsi, for example, is a excellent and in many ways unique particularly the 7-meter plant eater primitive ceratopsian or “horned window on the early stages of dinosaur Jinzhousaurus yangi (Wang and Xu, dinosaur” (Xu et al., 2006b), although diversification during the Cretaceous. 2001), the unparalleled preservation this species is in fact so primitive that Many of the Jehol Group’s abundant of diverse small forms is probably the horns that give the group its name fossil plants, invertebrates and the single greatest factor that makes are not yet evident. The very recently vertebrates are found in exquisitely the Jehol Group interesting to described Haplocheirus sollers is fine lake sediments, which frequently dinosaur researchers from the IVPP a primitive member of an unusual, preserve near-complete skeletons that and elsewhere. Small dinosaurs are bird-like group of theropods called may even show traces of feathers and generally rare in the fossil record, and to the alvarezsauroids (Choiniere et al., other soft tissue structures. have a large sample of them preserved 2010). Another Shishugou theropod, The rate of discovery and alongside birds, aquatic amphibians and Limusaurus inextricabilis (Xu et al., description of new Jehol dinosaurs reptiles, early mammals, and a diverse 2009), proved to be a particularly have been so rapid in the past several array of fish, plants and invertebrates is important find. Limusaurus is not years that it is possible to mention only extraordinary. only a very primitive member of the a few particularly important species. Even as ecological interpretations major theropod group Ceratosauria, Microraptor gui (Xu et al., 2003) is a of this unique tableau of Early but is also unique among known small member of the Dromaeosauridae, Cretaceous life continue, IVPP a group of theropods closely paleontologists have been at the related to birds. Although forefront of research on a geologically this species has a few older assemblage of less diverse but unusual skeletal similarly preserved dinosaurs from features, such western Liaoning and the Daohugou as a strongly Locality in easternmost Inner curved tibia, it Mongolia. These small dinosaurs is mainly notable date from the Late Jurassic. The for the presence of long, most spectacular specimen yet beautifully preserved feathers recovered from this older fauna is an that form potentially aerodynamic extravagantly feathered individual of surfaces on the hind limbs as well as Anchiornis huxleyi (Hu et al., 2009), The small theropod Mei long from the the forelimbs (see Hone, page 92 this a close relative of Mei. Potentially Lujiatun Beds of the Lower Cretaceous Jehol Group of Liaoning, China—a volume). Liaoningosaurus paradoxus even more intriguing, however, are dinosaur that died in a bird-like sleeping is an ankylosaur or armored dinosaur, two small and possibly arboreal posture. (Photo: IVPP) described by Xu et al. (2001) on the dinosaurs assigned to the new group basis of a small juvenile specimen, Scansoriopterygidae. Epidexipteryx ceratosaurs in being toothless and with an unusual shell-like plate over (Zhang et al., 2008) sports closely probably herbivorous. Furthermore, the abdominal region. Whereas both packed, forward-pointing teeth and the hand of Limusaurus has an unusual Microraptor and Liaoningosaurus long display feathers on the tail, while configuration, with digit I (the thumb) are known from articulated skeletons Epidendrosaurus (Zhang et al., 2002) surprisingly reduced. This is a piece of preserved on slabs of rock, so that is known from a fragmentary juvenile evidence in favor of the controversial the specimens are essentially two- specimen but clearly possesses a long, hypothesis that digit I eventually dimensional, the Lujiatun Beds of the slender finger reminiscent to some disappeared in theropods, so that the Jehol Group have yielded a number of extent of the middle digit on the hand three fingers present in advanced important specimens preserved in three of a living primate called the aye- theropods and their avian descendants dimensions. Perhaps the most striking aye (Daubentonia). The aye-aye uses are identifiable as digits II, III and example is the tiny theropod Mei long its slender finger to probe for insects IV (Xu et al., 2009). It is virtually (Xu and Norell, 2004), known from while foraging, and it is possible that certain that further field and lab an exquisitely preserved individual Epidendrosaurus did the same.

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Finally, the third area of wealth of information concentration has been the Upper on the anatomical Cretaceous Wulansuhai Formation characteristics of of western Inner Mongolia, an this group. However, exceptionally prolific source of work is ongoing and beautifully preserved dinosaurs further discoveries will and other vertebrates from the certainly follow. Also closing stages of the Mesozoic. worthy of mention is the In collaboration with both local recent description of another paleontologists and foreign colleagues, Cretaceous theropod, The dromaeosaurid IVPP researchers embarked on major Gigantoraptor erlianensis, theropod Linheraptor expeditions to Wulansuhai sites north from the Iren Dabasu Formation exquisitus from the Upper of the city of Linhe in the summers of of eastern Inner Mongolia (Xu et Cretaceous Wulansuhai Formation of Inner Mongolia, China. 2008 and 2009. Ever since Chinese al., 2007). Gigantoraptor, which must (Photo: IVPP) and Canadian paleontologists visited rank as one of the most surprising the same area together in 1988 and finds of the past several years, is an work of describing new taxa and 1990, the Wulansuhai Formation has enormous (probable body mass greatly assessing their phylogenetic positions, been known to contain a fauna rich in exceeding one tonne) relative of the and dinosaur research has been no ankylosaurs, primitive ceratopsians small, toothless, crested Mongolian exception. For example, Zhao et and small theropods, preserved theropod Oviraptor. al. (2007) inferred the presence of alongside lizards, mammals and The efforts of IVPP dinosaur gregarious behavior in juveniles of the dinosaur eggs. In many respects this researchers have not been limited to primitive ceratopsian Psittacosaurus, assemblage is similar to that known the three regions discussed above. Sullivan et al. (2010) documented the from the famous Flaming Cliffs and For instance, Xu et al. (2010b) gradual evolution of a bird-like wrist other localities in the seemingly recently described the new Cretaceous posture in theropods, and Hone et al. contemporaneous Djadokhta alvarezsauroid Xixianykus based (2010) found evidence corroborating Formation of Mongolia proper. on a specimen from Xixia County the possibility that the dromaeosaurids The only Wulansuhai specimen in Henan Province. Furthermore, of the Wulansuhai fauna sometimes from the recent IVPP expeditions the IVPP has seen a recent trend fed on ceratopsians. Dinosaur research to have so far been described is toward analytical studies of various at the IVPP has moved emphatically Linheraptor exquisitus (Xu et al., aspects of the biology and evolution into the 21st century—without, of 2010a), a nearly complete small of extinct vertebrates, taking place course, losing sight of the Jurassic and dromaeosaurid that provides a alongside the important traditional Cretaceous in the process.

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