Browsing by Author "Norell, Mark"
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Item A new dromaeosaurid (Dinosauria: Coelurosauria) from Khulsan, Central Mongolia (American Museum novitates, no. 3982)(American Museum of Natural History., 2021-11-08) Napoli, James G.; Ruebenstahl, Alexander; Bhullar, Bhart-Anjan S.; Turner, Alan H. (Alan Hamilton); Norell, MarkDromaeosaurid 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).Item A new dromaeosaurid from the Late Cretaceous Khulsan locality of Mongolia (American Museum novitates, no. 3965)(American Museum of Natural History., 2021-01-13) Turner, Alan H. (Alan Hamilton); Montanari, Shaena A.; Norell, MarkA 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.Item Reconstructing the specimens and history of Howe Quarry (Upper Jurassic Morrison Formation; Wyoming). (American Museum novitates, no. 3956)(American Museum of Natural History., 2020-06-24) Tschopp, Emanuel; Mehling, Carl; Norell, MarkIn 1934, Barnum Brown of the American Museum of Natural History in New York (AMNH) led a large-scale dinosaur excavation in northern Wyoming, where he had found bones two years earlier. Initially, Brown expected to excavate two skeletons of sauropod dinosaurs, but soon after opening the quarry, the team realized that the site far exceeded their expectations: in the end, they unearthed approximately 3000 bones within six months and sent approximately 144 crates back to the AMNH. Due to the enormous number of bones, the site became world famous as a dinosaur graveyard, and media from all over the United States and abroad reported on the expedition. Soon after, however, the collection shifted away from a curatorial focus. What followed was a history of neglect: inappropriate storage conditions, water and fire damage, collapsing wooden boxes, and deteriorating plaster jackets. Relocation and further excavation of the quarry by the Sauriermuseum Aathal (Switzerland; SMA) from 1989 to 1991 confirmed earlier finds of skin impressions and resulted in the recognition of a novel diplodocid sauropod: Kaatedocus siberi. Given that the amount of bones found by the AMNH far exceeded those found by the SMA, a new project was started in 2017 to reassess the state and scientific value of the historic collections at AMNH. Although most of the bones are heavily fragmented, preliminary results show that overall preservation is still exceptional. Here, we reconstruct the history of the excavation, as well as past conservation and preparation procedures, and provide a report of current efforts to prepare, conserve, and catalog the material that has remained in storage since the 1930s. These current efforts show that historic collections, even after decades of neglect, can be of great and unexpected value, both for research and scientific outreach.Item Spatial and temporal distribution of the island-dwelling Kogaionidae (Mammalia, Multituberculata) in the uppermost Cretaceous of Transylvania (Western Romania) (Bulletin of the American Museum of Natural History, no. 456)(American Museum of Natural History., 2022-06-14) Csiki-Sava, Zoltán; Vremir, Mátyás; Meng, Jin (Paleontologist); Vasile, Ștefan; Brusatte, Stephen; Norell, MarkThe latest Cretaceous kogaionid multituberculates from Transylvania (western Romania) were part of an endemic European clade of mammals that underwent an insular radiation at the end of the Cretaceous and then survived the end-Cretaceous mass extinction that extinguished many groups of contemporary therians. Transylvanian kogaionids lived on what was an island during the latest Cretaceous—“Hațeg Island”—and their fossils are found in the uppermost Campanian to upper Maastrichtian deposits of the Hațeg, Rusca Montană, and southwestern Transylvanian basins. This fossil record has improved dramatically over the past several decades, in part resulting from our decade-long joint Romanian-American-Scottish fieldwork, and comprises one of the most impressive and complete archives of Mesozoic mammals, including not only jaws and teeth but several incomplete skulls and partial skeletons.We here review the fossil record of kogaionids from Transylvania. We report four new occurrences from the Hațeg Basin, update information on previously described ones, and use our database to reassess the chronostratigraphical and geographical distribution of kogaionids and their evolutionary patterns. Although it was previously suggested that large and small kogaionids had largely mutually exclusive spatial distributions, we recognize the cooccurrence of small and large taxa in various units, suggesting a sympatric distribution across their entire chronostratigraphic range. We also identify a novel pattern: small kogaionids appear somewhat earlier than their larger relatives in all well-sampled sedimentary successions, suggesting that kogaionid colonizations of Hațeg Island and component regions took place at small body size and that body size increased only later through local evolution. We find correlations between body size, preservation style, and sedimentary context, which give insight into kogaionid paleobiology and diversity. Larger kogaionids are represented more often by partial skulls and occasionally skeletons compared with small kogaionids, which are usually represented only by isolated teeth, regardless of provenance. Larger kogaionids currently have a higher recognized local taxic diversity than their smaller relatives. We hypothesize that this may be in part a consequence of preservational bias related to body size, as more complete specimens may be more easily diagnosed as distinct taxa than those that are represented by more fragmentary and/or incomplete fossils. If true, the taxic diversity of smaller kogaionids may currently be underestimated. Finally, we identify correspondence between sedimentary facies and preservation style. Red-colored fine-grained rocks, suggestive of well-drained, oxidized floodplain paleoenvironments, yield more complete specimens than drab, greenish or grayish sediments deposited in more poorly drained parts of the floodplain. This pattern may suggest habitat preferences for better-drained floodplain environments and a semifossorial lifestyle for some taxa. As the kogaionid fossil record improves, we can further test the hypotheses and patterns outlined above. The pace of new kogaionid discoveries by our team and others indicates that a more complete picture of kogaionid distribution, paleobiology, and evolution will emerge in the coming years, contributing to a more profound understanding of this peculiar group of island-dwelling Mesozoic mammals.Item Supplemental Material for 'A second specimen of Citipati osmolskae associated with a nest of eggs from Ukhaa Tolgod, Omnogov Aimag, Mongolia. (American Museum novitates, no. 3899)'(2018-04-26) Norell, Mark; Balanoff, Amy M.; Barta, Daniel E.; Erickson, Gregory M.; Mongolian-American Museum Paleontological Project.; Mongolyn Shinzhlėkh Ukhaany Akademi.Supplemental Material for 'A second specimen of Citipati osmolskae associated with a nest of eggs from Ukhaa Tolgod, Omnogov Aimag, Mongolia. (American Museum novitates, no. 3899)'Item Supplemental Material for 'Convergent evolution of a eusuchian-type secondary palate within Shartegosuchidae. (American Museum novitates, no. 3901)'(2018-06-18) Dollman, Kathleen N.; Clark, James Matthew; Norell, Mark; Xu, Xing; Choiniere, Jonah N.; Mongolian-American Museum Paleontological Project.; Mongolyn Shinzhlėkh Ukhaany Akademi.Supplemental Material for 'Convergent evolution of a eusuchian-type secondary palate within Shartegosuchidae. (American Museum novitates, no. 3901)'Item Supplemental Material for 'Reconstructing the specimens and history of Howe Quarry (Upper Jurassic Morrison Formation; Wyoming). (American Museum novitates, no. 3956)'(2020-06-24) Tschopp, Emanuel; Mehling, Carl; Norell, MarkSupplemental Material for 'Reconstructing the specimens and history of Howe Quarry (Upper Jurassic Morrison Formation; Wyoming). (American Museum novitates, no. 3956)'