[D] Yurgovuchia doellingi [sG] [T]
Senter, Kirkland, Deblieux, Madsen, Toth 2012
Cretaceous Early Barremian? Aptian
Saurischia Theropoda Tetanurae Coelurosauria Dromaeosauridae
Cedar Mountain Formation, Yellow Cat Member, Utah, US
The Yellow Cat Member of the Cedar Mountain Formation (Early Cretaceous, Barremian? – Aptian) of Utah has yielded a rich theropod fauna, including the coelurosaur Nedcolbertia justinhofmanni, the therizinosauroid Falcarius utahensis, the troodontid Geminiraptor suarezarum, and the dromaeosaurid Utahraptor ostrommaysorum. Recent excavation has uncovered three new dromaeosaurid specimens. One specimen, which we designate the holotype of the new genus and species Yurgovuchia doellingi, is represented by a partial axial skeleton and a partial left pubis. A second specimen consists of a right pubis and a possibly associated radius. The third specimen consists of a tail skeleton that is unique among known Cedar Mountain dromaeosaurids.
Y. doellingi resembles Utahraptor ostrommaysorum in that its caudal prezygapophyses are elongated but not to the degree present in most dromaeosaurids. The specimen represented by the right pubis exhibits a pronounced pubic tubercle, a velociraptorine trait that is absent in Y. doellingi. The specimen represented by the tail skeleton exhibits the extreme elongation of the caudal prezygapophyses that is typical of most dromaeosaurids. Here we perform a phylogenetic analysis to determine the phylogenetic position of Y. doellingi. Using the resulting phylogeny as a framework, we trace changes in character states of the tail across Coelurosauria to elucidate the evolution of the dromaeosaurid tail.
The new specimens add to the known diversity of Dromaeosauridae and to the known diversity within the Yellow Cat paleofauna. Phylogenetic analysis places Y. doellingi in a clade with Utahraptor, Achillobator, and Dromaeosaurus. Character state distribution indicates that the presence of intermediate-length caudal prezygapophyses in that clade is not an evolutionarily precursor to extreme prezygapophyseal elongation but represents a secondary shortening of caudal prezygapophyses. It appears to represent part of a trend within Dromaeosauridae that couples an increase in tail flexibility with increasing size.
The holotype specimen is UMNH VP 20211. It includes cervical, dorsal, and caudal vertebrae; and the proximal end of a left pubis.
The genus name honors the Ute Tribe of northeastern Utah. It is derived from the Ute word yurgovuch, meaning ‘‘coyote,’’ a predator of similar size to Y. doellingi that currently inhabits the same region. The species name honors Helmut Doelling in recognition of his 50-plus years of geological research and mapping of Utah for the Utah Geological Survey. The Doelling’s Bowl dinosaur sites were first discovered as a result of his providing taped-together color photocopies of his then-unpublished geological maps of the Arches National Park region to JIK in 1990.
Locality and horizon
The specimen comes from Don’s Place, part of the Doelling’s Bowl bone bed in Grand County, Utah. The bone bed is in the lower Yellow Cat Member (Barremian?) of the Cedar Mountain Formation.
Dromaeosaurid theropod; centrum of axis with a single pneumatopore on each side; cranial end of centrum of third cervical vertebra not beveled; cervical rezygapophyses flexed; epipophyses of cervical vertebrae above postzygapophyseal facets; cervico-dorsal vertebrae with hypapophyses and without pneumatopores; cranial faces of centra of proximal caudal vertebrae round; caudal prezygapophyses elongated distal to transition point, but not over the length of a centrum. Pubis without pubic tubercle.