Rinchen Barsbold

A Review of the Mongolian Cretaceous Dinosaur Saurornithoides (Troodontidae: Theropoda)

Abstract We review the morphology, taxonomy, and phylogenetic relationships of the upper Cretaceous Mongolian troodontid Saurornithoides. Saurornithoides mongoliensis is known only by the holotype from Bayan Zag, Djadokhta Formation. This specimen includes a nearly complete, but weathered, skull and mandibles, a series of dorsal, sacral, and caudal vertebrae, and a partial pelvic girdle and hind limb. Saurornithoides junior, here referred to Zanabazar, also is known only by the holotype from Bugiin Tsav, Nemegt Formation. This specimen consists of a skull and partial mandible, a series of sacral and caudal vertebrae, a partial pelvic girdle, and the distal part of the right hind limb. Saurornithoides + Zanabazar is one of the few Mongolian taxa known from both the Djadokhta and Nemegt formations. The monophyly of Saurornithoides + Zanabazar has not been seriously questioned historically, yet empirical support for this clade is currently tenuous. A privileged phylogenetic relationship between Saurornithoid...

Palaeobiology - Herbivorous diet in an ornithomimid dinosaur

In 1997, twelve well-articulated skeletons of an ornithomimid dinosaur from the Upper Cretaceous Ulansuhai Formation in China were discovered. Each skeleton contained a preserved gastrolith mass inside the ribcage that was attached on the medial surface of the articulated dorsal ribs and gastralia. The occurrence and characteristics of gastrolith masses in this ornithomimid indicate that these non-avian toothless theropods may have had gizzards and been herbivores, like modern herbivorous birds that use grit to grind up plant matter.

TWO NEW OVIRAPTORIDS (THEROPODA: OVIRAPTOROSAURIA), UPPER CRETACEOUS DJADOKHTA FORMATION, UKHAA TOLGOD, MONGOLIA

ditions in the 1960s and 1970s. Two monotypic genera of Ovi raptoridae and a new species of Oviraptor were named and described by Barsbold (1981, 1983, 1986), and other material from these collections was described by Osm?lska (1976) and Elzanowski (1999). An oviraptorid skeleton from the Djadokhta Formation of China, also preserved on top of a nest, was de scribed by Dong and Currie (1996). The Djadokhta Formation preserves one of the richest, most diverse, and well preserved terrestrial vertebrate faunas of the Mesozoic, and Ukhaa Tolgod is the richest site in this formation yet discovered (Dashzeveg et al., 1995; Norell, 1997). Ovirap torids, surprisingly, are one of the most abundant taxa repre sented at Ukhaa Tolgod; previously reported discoveries include an embryo within an egg (Norell et al., 1994) and an adult sitting on a nest (Norell et al., 1995; Clark et al., 1999). The specimens collected from Ukhaa Tolgod thus far represent two new species, and they are described below.

A new enantiornithine bird from the Late Cretaceous of the Gobi Desert

Synopsis We report on a new species of enantiornithine bird from the Late Cretaceous of the Mongolian Gobi Desert, which adds to the meager record of birds from the latest part of the Mesozoic in this region. The exceptional, three‐dimensional bones of the new fossil increase the known anatomical diversity of enantiornithine birds, providing information about previously unreported morphologies such as a pneumatised furcula. Several synapomorphies nest the new bird within an enantiornithine clade of proficient fliers, but the anatomy and proportions of its flight apparatus imply significant aerodynamic restrictions. The combination of phylogeny and our functional interpretation suggests that this new fossil bird is a representative of a flightless lineage. This discovery thus provides the first evidence of a trend towards more limited flying capabilities among Enantiornithes, a group of Cretaceous birds otherwise believed to be represented by competent fliers.

Cranial osteology of a juvenile specimen of Tarbosaurus bataar (Theropoda, Tyrannosauridae) from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia

ABSTRACT A juvenile skull of the tyrannosaurid Tarbosaurus bataar found in the Bugjn Tsav locality in the Mongolian Gobi Desert is described. With a total length of 290 mm, the present specimen represents one of the smallest skulls known for this species. Not surprisingly, it shows various characteristics common to juvenile tyrannosaurids, such as the rostral margin of the maxillary fenestra not reaching that of the external antorbital fenestra and the postorbital lacking the cornual process. The nasal bears a small lacrimal process, which disappears in adults. Lacking some of the morphological characteristics that are adapted for bearing great feeding forces in adult individuals, this juvenile specimen suggests that T. bataar would have changed its dietary niches during ontogeny. The numbers of alveoli in the maxilla (13) and dentary (14 and 15) are the same as those in adults, suggesting that they do not change onto genetically in T. bataar and thus are not consistent with the hypothesis that the numbers of alveoli decreases ontogenetically in tyrannosaurids.

A pygostyle from a non-avian theropod

The independent evolution of a bird-like tail has been discovered in an oviraptorosaur.

An exquisitely preserved troodontid theropod with new information on the palatal structure from the Upper Cretaceous of Mongolia

Troodontidae is a clade of small-bodied theropod dinosaurs. A new troodontid, Gobivenator mongoliensis gen. et sp. nov., is described based on the most complete skeleton of a Late Cretaceous member of this clade presently known, from the Campanian Djadokhta Formation in the central Gobi Desert. G. mongoliensis is different from other troodontids in possessing a pointed anterior end of the fused parietal and a fossa on the surangular in front of the posterior surangular foramen. The skull was superbly preserved in the specimen and provides detailed information of the entire configuration of the palate in Troodontidae. Overall morphology of the palate in Gobivenator resembles those of dromaeosaurids and Archaeopteryx, showing an apparent trend of elongation of the pterygoid process of the palatine and reduction of the pterygopalatine suture toward the basal Avialae. The palatal configuration suggests that the skull of Gobivenator would have been akinetic but had already acquired prerequisites for later evolution of cranial kinesis in birds, such as the loss of the epipterygoid and reduction in contact areas among bones.

New material of dsungaripterid pterosaurs (Pterosauria: Pterodactyloidea) from western Mongolia and its palaeoecological implications

New material of dsungaripterid pterosaurs from the Early Cretaceous of Tatal, western Mongolia, allows the diagnoses of Dsungaripteridae and Noripterus to be amended. All pterosaurs found at Tatal belong to Dsungaripteridae (either Dsungaripterus or Noripterus ). The name Phobetor is a junior synonym of Noripterus . The differing shapes of the anterior tips of skulls, differing tooth morphologies and the coexistence of both Dsungaripterus and Noripterus may imply that they occupied distinct ecological niches.

A Nest of Protoceratops andrewsi (Dinosauria, Ornithischia)

Abstract A remarkable specimen of the small neoceratopsian dinosaur Protoceratops andrewsi (Late Cretaceous, Mongolia) reveals the first nest of this genus, complete with fifteen juveniles. The relatively large size of the individuals and their advanced state of development suggests the possibility that Protoceratops juveniles remained and grew in their nests during at least the early stages of postnatal development. The nest further implies that parental care and sociality are phylogenetically basal behaviors in Ceratopsia. Finally, it reaffirms the conclusion that Protoceratops lived (and died) in the sandy aeolian dune fields of the central Asian craton.

Perinatal Specimens of Saurolophus angustirostris (Dinosauria: Hadrosauridae), from the Upper Cretaceous of Mongolia

Background The Late Cretaceous Nemegt Formation, Gobi Desert, Mongolia has already yielded abundant and complete skeletons of the hadrosaur Saurolophus angustirostris, from half-grown to adult individuals. Methodology/Principal Findings Herein we describe perinatal specimens of Saurolophus angustirostris, associated with fragmentary eggshell fragments. The skull length of these babies is around 5% that of the largest known S. angustirostris specimens, so these specimens document the earliest development stages of this giant hadrosaur and bridge a large hiatus in our knowledge of the ontogeny of S. angustirostris. Conclusions/Significance The studied specimens are likely part of a nest originally located on a riverbank point bar. The perinatal specimens were buried by sediment carried by the river current presumably during the wet summer season. Perinatal bones already displayed diagnostic characters for Saurolophus angustirostris, including premaxillae with a strongly reflected oral margin and upturned premaxillary body in lateral aspect. The absence of a supracranial crest and unfused halves of the cervical neural arches characterize the earliest stages in the ontogeny of S. angustirostris. The eggshell fragments associated with the perinatal individuals can be referred to the Spheroolithus oogenus and closely resemble those found in older formations (e.g. Barun Goyot Fm in Mongolia) or associated with more basal hadrosauroids (Bactrosaurus-Gilmoreosaurus in the Iren Dabasu Fm, Inner Mongolia, China). This observation suggests that the egg microstructure was similar in basal hadrosauroids and more advanced saurolophines. Competing Interests One of the authors (FE) is employed by the commercial organization Eldonia. Eldonia provided support in the form of a salary for FE, but did not have any additional role or influence in the study design, data collection and analysis, decision to publish, or preparation of the manuscript and it does not alter the authors’ adherence to all the PLoS ONE policies on sharing data and materials.