Barun Goyot Research Articles

The first troodontid (Dinosauria: Theropoda) from the Upper Cretaceous Baruungoyot Formation of Mongolia

ABSTRACT Among non-avian dinosaurs, troodontids are relatively rare but diverse. The Nemegt Basin in the Mongolian Gobi Desert, which incorporates three of the most fossiliferous beds in the world, is one such region with high troodontid diversity and has also produced eight troodontid taxa until now. The diversity of troodontids is biased towards the two formations, Nemegt and Djadochta. Despite its rich vertebrate fossil record, no troodontids have been described from the Baruungoyot Formation. This faunal absence is perplexing as the Baruungoyot Formation has often been considered intermediate between the other two units in stratigraphy and paleoenvironment, but there are no definite troodontid materials that could fill this ‘gap.’ Here, we report a new troodontid, Harenadraco prima gen. et sp. nov., from the Baruungoyot Formation in Hermiin Tsav, Mongolia. It is represented by an incomplete skeleton that mainly consists of partially articulated left hind limb elements. Harenadraco is small and lightly built like other troodontids, but its tarsometatarsus exhibits extreme slenderness comparable only to Philovenator among cursorial non-avian maniraptorans. It also implies high cursoriality that could be an adaptation of Harenadraco to its environment where potential prey animals like mammals and predators such as eudromaeosaurs were likely to be agile. The discovery of Harenadraco confirms the presence of troodontids in all three formations in the Nemegt Basin. http://zoobank.org/urn:lsid:zoobank.org:pub:0981D708-986B-4B81-8809-E239DF9E8444

Ontogeny and miniaturization of Alvarezsauridae (Dinosauria, Theropoda)

The ontogenetic status of the known specimens of alvarezsaurid theropod dinosaurs is revised. We present histological data that the holotype of Parvicursor remotus from the Upper Cretaceous Barungoyot Formation of Mongolia is not an adult individual, as previously thought, but a juvenile less than one year old. The miniaturization took place only in the Late Cretaceous Asiatic Parvicursorinae, whereas the Late Cretaceous South American non-parvicursorine alvarezsaurids were large animals. The miniaturization occurred by shifting ossification to earlier ontogenetic stages, in particular, by the closure of the neurocentral sutures on the presacral vertebrae of juvenile animals. There is no morphological support for the myrmecophagy in the alvarezsaurids and a shift to a myrmecophagous ecological niche does not explain the need for miniaturization.

First occurrence of the eutherian mammal Asioryctes nemegtensis from the Upper Cretaceous Djadokhta Formation, Gobi Desert, Mongolia, and a revised alpha taxonomy based on the skull and dentition

ABSTRACT We report on the discovery of new skulls and dentitions documenting a broader geographic and stratigraphic range for the eutherian mammal Asioryctes nemegtensis. Originally discovered in the Upper Cretaceous Barun Goyot Formation of the Gobi Desert, Mongolia, A. nemegtensis has been hypothesized to be absent from the Djadokhta Formation, another Upper Cretaceous Gobi Desert formation. This distinction has previously contributed to an emphasis on faunal and age dissimilarity between the two sets of Cretaceous rocks. Here we report four new specimens of A. nemegtensis from the Djadokhta Formation and document its first co-occurrence with its sister taxon, Ukhaatherium nessovi. The new specimens reveal additional details about the cranial and dental anatomy of asioryctitheres and prompt an alpha taxonomic revision and emended diagnosis for A. nemegtensis. Among the new specimens are a nearly complete skull and several articulated jaws, which provide new information on tooth occlusion. These discoveries are an additional datapoint indicating that some Upper Cretaceous faunal assemblages in Mongolia are not as distinctly different in composition and age as has been previously hypothesized.

A new alvarezsaurid theropod dinosaur from the Upper Cretaceous of Gobi Desert, Mongolia

Ondogurvel alifanovi gen. et sp. nov. (Alvarezsauridae, Parvicursorinae) is described based on a partial postcranial skeleton from the Upper Cretaceous (Campanian) Barungoyot Formation at the Nemegt locality in Mongolia. The new taxon differs from all other alvarezsaurids in having metatarsals II and IV completely fused along their contact area. The phylogenetic analysis places Ondogurvel in a clade with the Late Cretaceous Asian parvicursorines Xixianykus and Albinykus, which have proximally co-ossified metatarsals II and IV. Two morphological types of the parvicursorine carpometacarpus can be recognized. In the first type exemplified by Mononykus and Ondogurvel, the articular surfaces of metacarpals III and IV are located along the lateral margin of the carpometacarpus and small, but functional digits III and IV were flexed in a plane almost perpendicular to the flexion plane of digit II. In the second type exemplified by the Bissekty alvarezsaurid and Linhenykus, the articular surface of metacarpal IV is missing and the articular surface of metacarpal III is located along the distal margin of the carpometacarpus, in line with the distal condyles of metacarpal II. In this case, the small functional digit III was flexing in the same plane as the main digit II. Linhenykus has the carpometacarpus of the second type, but the distal articular surface of metacarpal III is greatly reduced and manual finger III was apparently absent. This drastic difference in the morphology of the carpometacarpus may suggest a deep divergence between the parvicursorine lineages represented by the Bissekty alvarezsaurid – Linhenykus and Mononykus – Ondogurvel.LSID: urn:lsid:zoobank.org:pub:AC4A7F7F-3E67-425A-865F-3F47B0AB2AAE.

The second taxon of alvarezsaurid theropod dinosaurs from the Late Cretaceous Khulsan locality in Gobi Desert, Mongolia

ABSTRACT Khulsanurus magnificus gen. et sp. nov., is described based on a partial skeleton, including cervical and caudal vertebrae, scapulocoracoids, humerus, and pubis from the Late Cretaceous (Campanian) Barungoyot Formation at Khulsan locality in Gobi Desert, Mongolia. The new taxon differs from other alvarezsaurids by a combination of characters that include cervicals lacking pleurocoels, carotid processes, and epipophyses, dorsoventrally thick and subtriangular in cross-section transverse process of the anterior caudals, prominent infrapostzygapophyseal fossa on the transverse process of anterior caudals, short and mostly anteriorly directed prezygapophyses of anterior caudals, neural arch of anterior caudal lacking the interzygapophyseal ridges and having a prominent dorsal depression around the anterior end of the neural spine. The new taxon retains a number of plesiomorphic traits: slightly convex posterior centrum condyle of anterior caudals, prominent anterior, and posterior bumps at the neurocentral junction in anterior caudals, neural arch of anterior caudals extending for the entire length of the centrum, and pubic foot and apron. Khulsanurus shares with Shuvuuia the deltopectoral crest of humerus that is continuous with the humeral head. The phylogenetic analysis placed Khulsanurus in the Parvicursorinae in a polytomy with Mononykus, Shuvuuia, Albinykus, and Xixianykus.

A New Dromaeosaurid (Dinosauria: Coelurosauria) from Khulsan, Central Mongolia

Dromaeosaurid theropods represent a rare but important clade of nonavialan dinosaurs. Their close evolutionary relationship to modern birds has placed them at the center of paleontological research for the last several decades. Herein we describe a new species of dromaeosaurid—Kuru kulla, gen. et sp. nov.—based on a partial skeleton from the Late Cretaceous Khulsan locality (Barun Goyot Formation) of Mongolia. This species is diagnosed by several autapomorphies within Dromaeosauridae, including a sharp groove anterior and ventral to the narial fossa on the premaxilla, a posterolaterally directed hornlet on the posterodorsal process of the lacrimal, a deep surangular bearing two surangular foramina, and anteriorly displaced pleurocoels on the dorsal centra. The taxon is further characterized by a unique combination of characters, including a mediolaterally narrow metatarsal II, serrations on both carinae of the dentary teeth, hyposphenes that are widely separated but joined by a web of bone, and a lacrimal with a poorly developed boss on its lateral surface. Phylogenetic analysis finds Kuru kulla to be the sister taxon of Adasaurus mongoliensis, from the slightly later Nemegt Formation, with which it is united by three synapomorphies: a posterior surangular foramen that is ∼30% the depth of the surangular, absence of a fourth trochanter of the femur, and thoracic centra that are markedly longer than their midpoint widths. The recognition of this taxon has important implications for common assumptions of Mesozoic terrestrial ecosystem structure and adds new data to a recently recognized pattern in dromaeosaurid faunal composition among Late Cretaceous localities in Mongolia and Inner Mongolia (Nei Mongol Autonomous Region, China).

A re-appraisal of Parvicursor remotus from the Late Cretaceous of Mongolia: implications for the phylogeny and taxonomy of alvarezsaurid theropod dinosaurs

Parvicursor remotus Karhu & Rautian, 1996, based on a fragmentary skeleton from the Campanian Barungoyot Formation at Khulsan, in the Gobi Desert of Mongolia, is re-described in detail. Contrary to the original description, we find no evidence that the last dorsal vertebra is opisthocoelous. A biconvex last dorsal vertebra could be present in Parvicursor as in other parvicursorines. The transversely compressed sacral centrum with a sharp ventral keel is the last sacral, not the first sacral as originally alleged. The pelvic bones are not fused at the acetabulum. The holotype of P. remotus, the smallest known alvarezsaurid specimen, is a juvenile individual far from skeletal maturity. New morphological details of Parvicursor that are revealed include a ventral ridge on the posterior dorsal vertebrae; a horizontal supraacetabular crest of the ilium whose anterior end is placed anterior to the most ventrally projecting part of the pubic peduncle; the possible presence of a pubic obturator foramen; an entocondylar tuber on the femur; internal flexor flanges on metatarsals II and IV; a lateral flexor ridge on metatarsal IV; and a proximoventral notch on pedal phalanx IV-1. The Tugriken Shireh alvarezsaurid is not referable to Parvicursor because of its much larger ungual phalanx on the second pedal digit. Kol ghuva is excluded from Alzarezsauridae. The two successive sister taxa for Parvicursor are Ceratonykus and Linhenykus. Ceratonykus differs little from Parvicursor and might be a synonym of the latter. Linhenykus is very similar to Parvicursor in all overlapping skeletal elements. The Parvicursorinae includes all Asian Late Cretaceous alvarezsaurids except Qiupanykus and Nemegtonykus.

A new ankylosaurid skeleton from the Upper Cretaceous Baruungoyot Formation of Mongolia: its implications for ankylosaurid postcranial evolution

A new articulated postcranial specimen of an indeterminate ankylosaurid dinosaur from the Upper Cretaceous (middle-upper Campanian) Baruungoyot Formation from Hermiin Tsav, southern Gobi Desert, Mongolia includes twelve dorsal vertebrae, ribs, pectoral girdles, forelimbs, pelvic girdles, hind limbs, and free osteoderms. The new specimen shows that Asian ankylosaurids evolved rigid bodies with a decreased number of pedal phalanges. It also implies that there were at least two forms of flank armor within Ankylosauridae, one with spine-like osteoderms and the other with keeled rhomboidal osteoderms. Unique anatomical features related to digging are present in Ankylosauridae, such as dorsoventrally flattened and fusiform body shapes, extensively fused series of vertebrae, anteroposteriorly broadened dorsal ribs, a robust humerus with a well-developed deltopectoral crest, a short robust ulna with a well-developed olecranon process, a trowel-like manus, and decreased numbers of pedal phalanges. Although not fossorial, ankylosaurids were likely able to dig the substrate, taking advantage of it for self-defence and survival.

A New Dromaeosaurid from the Late Cretaceous Khulsan Locality of Mongolia

A new dromaeosaurid dinosaur, Shri devi, from the Late Cretaceous deposit of the Barun Goyot Formation at Khulsan, Mongolia, is described here. The Barun Goyot Formation (herein referred to as the Barun Goyot) is stratigraphically intermediate between the overlying Nemegt Formation and the underlying Djadokhta Formation, where much of the dromaeosaurid diversity has been reported to date. Sediments of the Barun Goyot are typically considered Upper Campanian in age. Although dromaeosaurid remains have been noted to occur in the Barun Goyot for decades, descriptive and taxonomic work has never been completed for the material. The holotype specimen (IGM 100/980) consists of a partially articulated individual preserving the right hind limb; left tibiotarsus; pelvis; and adjacent cervical, dorsal, and caudal vertebrae. IGM 100/980 is referable to a clade with Velociraptor based on the presence of a distinct ambiens tubercle located proximally on the anterior face of the pubis, a well-developed anterior tuberosity proximally located on the ischium, and a rounded longitudinal ischial ridge. It is distinguishable from V. mongoliensis based on a weak fourth trochanter (shared with all other dromaeosaurids) and deep anterior pedicular fossae in the cervical vertebrae; epipophyses in the last four cervicals are not raised but are instead represented by rugose circular scars. A suite of axial and appendicular characters are diagnostic for the new species. New discoveries including Shri devi allow for an improved understanding of dromaeosaurid anatomy, as well as the temporal and regional variation of the dromaeosaurid fauna of Mongolia and Inner Mongolia (Nei Mongol Autonomous Region, China), during the Late Cretaceous.

Heyuanninae clade nov., a replacement name for the oviraptorid subfamily"Ingeniinae" Barsbold, 1981.

Barsbold (1981) erected Ingenia yanshini Barsbold, 1981 for a nearly complete oviraptorid skeleton from the Upper Cretaceous (Campanian-Maastrichtian) Barun Goyot Formation in Ömnögov, southern Mongolia. Moreover, he erected a subfamily-level clade Ingeniinae Barsbold, 1981 to distinguish Ingenia yanshini from other oviraptorids such as Oviraptor philoceratops Osborn, 1924 (Barsbold, 1981). When Barsbold first erected the subfamily, he considered this subfamily as monotypic (Barsbold, 1981) but now this subfamily comprisesmultiple taxa such as Machairasaurus leptonychus Longrich, Currie, and Dong, 2010 and Heyuannia huangi Lü, 2002.

Ontogeny and variation of a protoceratopsid dinosaur Bagaceratops rozhdestvenskyi from the Late Cretaceous of the Gobi Desert

ABSTRACT Bagaceratops rozhdestvenskyi is a ceratopsian dinosaur from the Late Cretaceous Baruungoyot Formation of the Gobi Desert, closely related to Protoceratops spp. Several Bag. rozhdestvenskyi skulls demonstrate a wide range of variation in their morphology and size. Here I argue that the observed variability is most likely of intraspecific nature. Specimens classified in a few allegedly distinct species from the same or near-contemporary sediments, namely Gobiceratops minutus, Lamaceratops tereschenkoi and Platyceratops tatarinovi from Baruungoyot Formation, and Magnirostris dodsoni from Bayan Mandahu, are younger subjective synonyms of Bag. rozhdestvenskyi. They plausibly represent an ontogenetic series within the latter. Breviceratops kozlowskiiis a distinct taxon. The evolutionary relationships within Protoceratopsidae are complicated by the mosaic distribution of plesiomorphic and derived features in distinct species. I suggest that taxa distribution and observed changes in morphology are an evidence for the ancestral position of Protoceratops andrewsi among protoceratopsids. It implies possible temporary separation between the geological formations of the Gobi Desert yielding distinct protoceratopsid species. The novel evolutionary scenario suggests number of convergences that occurred in Protoceratopsidae and Ceratopsoidea (reduction of the premaxillary dentition, fusion of nasals, development of the accessory antorbital fenestra). Present study reveals the significance of the intraspecific and ontogenetic variation in the study of the neoceratopsian taxonomy.

Redescription and affinities of Hulsanpes perlei (Dinosauria, Theropoda) from the Upper Cretaceous of Mongolia.

Hulsanpes perlei is an enigmatic theropod dinosaur from the Baruungoyot Formation (?mid- to upper Campanian, Upper Cretaceous) of Mongolia. It was discovered in 1970, during the third Polish-Mongolian paleontological expedition to the Nemegt Basin. The taxon is known based on a partial braincase and an incomplete right hindlimb. However, the braincase fragment has never been described nor illustrated. We redescribe all elements that form the holotype of Hulsanpes and discuss the affinities of this taxon. The braincase fragment is interpreted as belonging to the inner ear region, and includes the floccular recess and part of the labyrinth. Hulsanpes perlei is confirmed as a valid taxon, diagnosed by a unique combination of metatarsal characters, including two autapomorphies. Historically, it represents the oldest record of the recently-established clade Halszkaraptorinae. Our findings identify subcursorial adaptations for Hulsanpes, shared with Mahakala, and differentiating them from Halszkaraptor. As such, appendicular disparity in the potentially sympatric halszkaraptorines suggest a reduced ecological overlap among these taxa, which may explain the co-occurrence of multiple species of this clade during the latest Cretaceous in what is now the Nemegt Basin.

Stratigraphy and paleoenvironmental evolution of the dinosaur-rich Baruungoyot-Nemegt succession (Upper Cretaceous), Nemegt Basin, southern Mongolia

Portions of the dinosaur-rich Upper Cretaceous Baruungoyot-Nemegt succession are exposed in four geographic areas of the Nemegt Basin, Mongolia: Nemegt, Altan Uul, Bügiin Tsav, and Hermiin Tsav. Lithostratigraphic correlations of these areas employ marker beds and non-random stratigraphic patterns of lithology, grain-size variation, and inferred paleoenvironments. Correlations suggest a minimum thickness of 350m for the succession. Exposures at Nemegt, Altan Uul, and Bügiin Tsav form a 100km east-west transect along the northern margin of the basin, exposing 265m of section. From east to west the transect exposes higher portions of the succession, extending from the uppermost Baruungoyot Formation and encompassing an almost complete section of the Nemegt Formation, which has a minimum thickness of 235m and can be consistently divided into three informal members: lower, middle, and upper. The lower Nemegt is well exposed at Nemegt and Altan Uul and is dominated by fluvial deposits. The middle and upper Nemegt are well exposed at Altan Uul 2 and Bügiin Tsav and consist of alluvial plain, paludal, lacustrine, and fluvial deposits. As confirmed by earlier studies, the Baruungoyot and Nemegt formations exhibit an interfingering transition at Nemegt. The Hermiin Tsav section is a geographic outlier, tens of kilometers west-southwest of the northern transect. It exposes about 150m of section that overlaps with, but is mostly lower, stratigraphically, than the northern transect. The uppermost Hermiin Tsav section correlates with the lowermost Nemegt section, and also exhibits an interfingering contact between the Baruungoyot and Nemegt formations. The remaining section at Hermiin Tsav comprises sediments of the Baruungoyot Formation (135m) that were deposited in alluvial fan, fluvial, paludal, lacustrine, and eolian environments, and can be divided into two informal members designated as lower and upper. The distribution of facies through the composite section records changes in paleoenvironments during the Late Cretaceous that may provide insights into the origins of the dinosaurian biostratigraphy.

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

BackgroundThe 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 FindingsHerein 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/SignificanceThe 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 InterestsOne 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.

The ankylosaurid dinosaurs of the Upper Cretaceous Baruungoyot and Nemegt formations of Mongolia

The discovery of a new ankylosaurid skull with some unusual features from the Baruungoyot Formation of Mongolia prompted a systematic review of ankylosaurid specimens from the Baruungoyot and Nemegt formations. Dyoplosaurus giganteus was found to possess no diagnostic features and is regarded as a nomen dubium. The holotype of Tarchia kielanae (previously synonymized with Tarchia gigantea) has one autapomorphy, an accessory postorbital ossification with surrounding furrow, and Tar. kielanae is here considered a valid species, making the combination Tar. gigantea unnecessary. An accessory postorbital ossification is also found in the holotype of Minotaurasaurus ramachandrani, and this species is here considered a junior synonym of Tar. kielanae. The newly described skull from the Baruungoyot Formation forms the holotype of a new genus and species, Zaraapelta nomadis gen. et sp. nov., diagnosed by unusual bilayered ornamentation on the squamosal horn and extensive postocular ornamentation. Two distinct tail club handle morphotypes are present in the Nemegt Formation and probably represent two different species. However, it is impossible to assign either tail club morphotype to the single valid species from the formation, Saichania chulsanensis, because of a lack of overlapping material. A revised phylogenetic analysis including newly identified characters found Zaraapelta nomadis to be most closely related to Tar. kielanae. © 2014 The Linnean Society of London

Revisiting Sabath's "Larger Avian Eggs" from the Gobi Cretaceous

In 1991, Sabath described “larger avian eggs” from the Upper Cretaceous Barun Goyot and Djadokhta Formations of Mongolia. These were later included in the ootaxon Gobioolithus major. Here we recognize the larger avian eggs of Sabath as a distinct ootaxon, Styloolithus sabathi, oogen. et oosp. nov. These eggs differ from those of Gobioolithus in being larger (70 by 32 mm) and more elongate. Microscopically, the shell bears a third layer (possible external zone) thicker than the mammillary layer and nearly as thick as the second layer (possible squamatic zone); the continuous layer (including layers two and three) to mammillary layer thickness ratio is 3.1:1. Within the clutch, the tightly spaced eggs stand with their long axes steeply inclined. Adult remains are associated with two clutches, suggesting an incubation mode similar to that of troodontid maniraptorans, where adults sat atop largely buried eggs. S. sabathi provides evidence that relative egg size in Mesozoic non-ornithuromorph birds had increased markedly from the non-avian theropod condition in oviraptorids and troodontids, but had not yet reached the modern egg-adult proportions of Neornithes. Sediment-bound upright eggs appear common to Enantiornithes and more basal avians, suggesting that like non-avian theropods, these birds lacked chalazae, the chords of albumen allowing egg rotation in modern birds. Absence of this simple structure may have restricted these basal birds to ground nesting in areas with appropriate substrates and not permitted the type of nesting diversity found in Neornithes. Neornithes are the only Mesozoic clade of Dinosauria to nest completely free of sediment; this may have played a crucial role in their surviving the K-Pg mass extinction event.

An embryonic enantiornithine bird and associated eggs from the cretaceous of Mongolia

Enantiornithes is the most speciose clade of Cretaceous birds, but many taxa are known from isolated postcranial skeletons. Two embryonic enantiornithine bird skeletons of Gobipipus reshetovi gen. et sp. nov. from the Upper Cretaceous (Campanian) Barun Goyot Formation of the Gobi Desert in Mongolia provide new insights into the anatomy, radiation, and mode of development of early avialans. In recent times, both enantiornithine and ornithuromorph birds are known from the Barun Goyot Formation as well as from the Djadokhta and Nemegt Formations. The 80-million-year-old Gobipipus skeletons encased within eggshells shows several features characteristic of enantiornithine birds. The wing skeleton and shoulder girdle show morphological features indicating that Gobipipus achieved sophisticated powered flight. Gobipipus reshetovi gen. et sp. nov. is quite distinct from the sympatric enantiornithine species Gobipteryx minuta from the same strata in many anatomical features. Phylogenetic analysis of 26 avialan ingroup taxa based on distribution of 202 characters indicate that Gobipipus is a basal member of enantiornithine birds along with Confuciusornis and shares more characters with ornithuromorphs than previously recognized. The embryonic nature of Gobipipus specimens sheds new light on the developmental history of enantiornithine birds. The well-ossified bones of the fore- and hind limbs, and fusion of many skeletal elements indicate a precocial mode of development in Gobipipus. Apparently Gobipipus hatchlings could walk away from the ground nests as soon as they emerged from their eggs. The asymmetry of egg poles are unique features of Gobipipus eggs (oogenus Gobioolithus) among Cretaceous avialans. The microstructure of the shell in Gobioolithus eggs with the embryos of Gobipipus is typical avian (of ornithoid basic type) and less ratite-like in morphology of the spongy layer than is that in the other possible egg-remains of enantiornitine birds (oofamily Laevisoolithidae).

The taxonomic identity of a nearly complete ankylosaurid dinosaur skeleton from the Gobi Desert of Mongolia

Mongolian Paleontological Center (MPC) 100/1305 is one of the most complete ankylosaurid skeletons ever collected, and includes much of the postcranial skeleton and numerous in situ osteoderms. This specimen has been referred to Saichania chulsanensis, based on the similarity of the skull compared to the holotype of Saichania, MPC 100/151. However, MPC 100/1305 does not include a skull, and so referral of MPC 100/1305 to Saichania must be based on postcranial characters. Comparison of the postcrania of MPC 100/1305 and MPC 100/151 reveals several differences in the scapula, humerus, and metacarpals, indicating that MPC 100/1305 should not be referred to Saichania. Additionally, although it was previously reported that MPC 100/1305 was collected from the Baruungoyot Formation at Khulsan in Mongolia, collection records indicate that this specimen was instead collected from the Djadokhta Formation at Zamyn Khond. Two ankylosaurid species are known from the Djadokhta Formation of Mongolia and China, Pinacosaurus grangeri and P. mephistocephalus. There are no diagnostic characters in MPC 100/1305 that can be used to refer this specimen to P. grangeri or P. mephistocephalus, and there are a few differences between MPC 100/1305 and Pinacosaurus, such as the number of caudal vertebrae, and morphology of the coracoid, which have uncertain taxonomic implications. At present, MPC 100/1305 is best referred to Ankylosauridae indet., or cf. Pinacosaurus, based on its generally congruent morphology with Pinacosaurus and its provenance from the Djadokhta Formation, in which Pinacosaurus is the only recognized ankylosaurid taxon.

New Specimens of Nemegtomaia from the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia

Two new specimens of the oviraptorid theropod Nemegtomaia barsboldi from the Nemegt Basin of southern Mongolia are described. Specimen MPC-D 107/15 was collected from the upper beds of the Baruungoyot Formation (Campanian-Maastrichtian), and is a nest of eggs with the skeleton of the assumed parent of Nemegtomaia on top in brooding position. Much of the skeleton was damaged by colonies of dermestid coleopterans prior to its complete burial. However, diagnostic characters are recovered from the parts preserved, including the skull, partial forelimbs (including the left hand), legs, and distal portions of both feet. Nemegtomaia represents the fourth known genus of oviraptorid for which individuals have been found on nests of eggs. The second new specimen, MPC-D 107/16, was collected a few kilometers to the east in basal deposits of the Nemegt Formation, and includes both hands and femora of a smaller Nemegtomaia individual. The two formations and their diverse fossil assemblages have been considered to represent sequential time periods and different environments, but data presented here indicate partial overlap across the Baruungoyot-Nemegt transition. All other known oviraptorids from Mongolia and China are known exclusively from xeric or semi-arid environments. However, this study documents that Nemegtomaia is found in both arid/aeolian (Baruungoyot Formation) and more humid/fluvial (Nemegt Formation) facies.

Trace fossils on dinosaur bones from Upper Cretaceous eolian deposits in Mongolia: Taphonomic interpretation of paleoecosystems in ancient desert environments

The formation processes of trace fossils – including shallow to deep pits, notches, borings (tunnels), and channels, particularly at the limb joints – observed on the surfaces of Velociraptor, Protoceratops, ankylosaurid, and Bagaceratops skeletons from Upper Cretaceous eolian deposits in the Gobi desert, Mongolia were investigated. The median diameters of these structures ranged from 5.25 to 7.68 mm. These structures were likely created by insects scavenging on dinosaur carcasses. This interpretation is corroborated by the presence of burrows of a size similar to the trace fossils observed on the dinosaur bone surfaces at the same locality. Broad borings (about 32 mm in diameter) created by small Mesozoic mammals have also been discovered on the ribs and scapulae of a Protoceratops skeleton. Dinosaur skeletons found at two localities, Tugrikin Shireh and Khermeen Tsav, and two formations, the Djadokhta Formation and Barun Goyot Formation, exhibited the same type of damage to the limb joints. The high frequency of trace fossils at the limb joints suggests that small animals targeted the collagen in the joint cartilage of dried dinosaur carcasses as a source of nitrogen, which was relatively scarce in the eolian environments of the Gobi desert during the Late Cretaceous.