Martharaptor greenriverensis, a New Theropod Dinosaur from the Lower Cretaceous of Utah

Abstract

BackgroundThe Yellow Cat Member of the Cedar Mountain Formation (Early Cretaceous, Barremian?) of Utah has yielded a rich dinosaur fauna, including the basal therizinosauroid theropod Falcarius utahensis at its base. Recent excavation uncovered a new possible therizinosauroid taxon from a higher stratigraphic level in the Cedar Mountain Formation than F. utahensis.Methodology/Principal FindingsHere we describe a fragmentary skeleton of the new theropod and perform a phylogenetic analysis to determine its phylogenetic position. The skeleton includes fragments of vertebrae, a scapula, forelimb and hindlimb bones, and an ischium. It also includes several well-preserved manual unguals. Manual and pedal morphology show that the specimen is distinct from other theropods from the Cedar Mountain Formation and from previously described therizinosauroids. It is here named as the holotype of a new genus and species, Martharaptor greenriverensis. Phylogenetic analysis places M. greenriverensis within Therizinosauroidea as the sister taxon to Alxasaurus + Therizinosauridae, although support for this placement is weak.Conclusions/SignificanceThe new specimen adds to the known dinosaurian fauna of the Yellow Cat Member of the Cedar Mountain Formation. If the phylogenetic placement is correct, it also adds to the known diversity of Therizinosauroidea.

Description of Arundel Clay ornithomimosaur material and a reinterpretation ofNedcolbertia justinhofmannias an “Ostrich Dinosaur”: biogeographic implications

“…6.4E in Makovicky, Kobayashi & Currie, 2004 ). Because dromaeosaurids (e.g., Deinonychus ), troodontids (e.g., Geminiraptor ), oviraptorosaurs (e.g., Microvenator ), and therizinosaurs (e.g., Falcarius ) are also known from the Arundel Clay and other North American units of similar Early Cretaceous age ( Weishampel & Young, 1996 ; Lipka, 1998 ; Weishampel et al, 2004 ; Kirkland et al, 2005 ; Weishampel, 2006 ; Senter et al, 2010 ; Senter, Kirkland & Deblieux, 2012 ), comparisons with these forms are warranted before assignment of the humerus to a basal ornithomimosaur like Harpymimus . NHRD-AP 2015.v.103.9 differs from all of these in lacking a moderately developed to well-developed and large deltopectoral crest ( Clark, Maryańska & Barsbold, 2004 ; Makovicky & Norell, 2004 ; Norell & Makovicky, 2004 ; Osmólska, Currie & Barsbold, 2004 ).…”

The Slothful Claw: Osteology and Taphonomy of Nothronychus mckinleyi and N. graffami (Dinosauria: Theropoda) and Anatomical Considerations for Derived Therizinosaurids

“…Since No . mckinleyi was described, three new therizinosaurians have been named from North America: Falcarius utahensis [ 1 ] the most basal therizinosaurian known to date, Nothronychus graffami [ 2 ] the most complete therizinosaurid known to date, and Martharaptor greenriverensis , tentatively referred to Therizinosauria based on highly fragmentary materials [ 20 ]. Although incredibly important from a phylogenetic and biogeographical perspective, both species of Nothronychus have been only preliminarily described [ 2 , 16 ] with the exception of the braincase of No .…”

Living alone or moving in herds? A holistic approach highlights complexity in the social lifestyle of Cretaceous ankylosaurs

“…Furthermore, in a more local context, the largest terrestrial predators known from the localities of the MDAs of Gastonia burgei and the Iharkút nodosaurids are not giants but medium-sized theropods (e.g. Senter et al, 2012; J o u r n a l P r e -p r o o f 2012), and the remains of gigantic predators are rare at the Pinacosaurus MDA sites as well (Dingus et al, 2008). This pattern also weakens the hypothesis that group formation in these ankylosaurs was driven by the presence and/or abundance of large-bodied predators.…”