[D] Geminiraptor suarezarum [sG] [T]
Describer
Senter, Kirkland, Bird & Bartlett 2010
Time
Cretaceous Early ?Barremian
Classification
Saurischia Theropoda Tetanurae Coelurosauria Maniraptora Troodontidae
Diet
Carnivore
Fossilsite
Lower Yellow Cat Member, Cedar Mountain Formation, Grand County, Utah, US
Info
Abstract
Background
The theropod dinosaur family Troodontidae is known from the Upper Jurassic, Lower Cretaceous, and Upper Cretaceous of Asia and from the Upper Jurassic and Upper Cretaceous of North America. Before now no undisputed troodontids from North America have been reported from the Early Cretaceous. Methodology/Principal Findings: Herein we describe a theropod maxilla from the Lower Cretaceous Cedar Mountain Formation of Utah and perform a phylogenetic analysis to determine its phylogenetic position.
The specimen is distinctive enough to assign to a new genus and species, Geminiraptor suarezarum. Phylogenetic analysis places G. suarezarum within Troodontidae in an unresolved polytomy with Mei, Byronosaurus, Sinornithoides, Sinusonasus, and Troodon + (Saurornithoides + Zanabazar). Geminiraptor suarezarum uniquely exhibits extreme pneumatic inflation of the maxilla internal to the antorbital fossa such that the anterior maxilla has a triangular cross-section.
Unlike troodontids more closely related to Troodon, G. suarezarum exhibits bony septa between the dental alveoli and a promaxillary foramen that is visible in lateral view. Conclusions/Significance: This is the first report of a North American troodontid from the Lower Cretaceous. It therefore contributes to a fuller understanding of troodontid biogeography through time. It also adds to the known dinosaurian fauna of the Cedar Mountain Formation.
Holotype
The holotype specimen is CEUM (College of Eastern Utah Prehistoric Museum, Price Utah) 7319, a maxilla.
Etymology
The species name refers to Drs. Celina and Marina Suarez, the twin geologists who discovered the Suarez site. The genus name is from the Latin geminae (‘‘twins,’’ in honor of the Suarez sisters) and raptor (‘‘one who seizes or takes by force,’’ a common part of deinonychosaurian genus names).
Locality and horizon
The specimen is from the Suarez site, a dinosaur bonebed (dominated by the therizinosauroid Falcarius) in the lower Yellow Cat Member (Lower Cretaceous: Barremian?) of the Cedar Mountain Formation. The site is in western Grand County, Utah.
Diagnosis
Troodontid possessing a maxilla with extensive pneumatization internal to the antorbital fossa, inflating the bone so that it has a triangular cross-section; a large, craniocaudally elongate maxillary fenestra; a promaxillary fenestra that is visible in lateral view; craniocaudally narrow promaxillary strut and interfenestral strut; small, square dental alveoli with bony septa between them.
Senter, Kirkland, Bird & Bartlett 2010
Time
Cretaceous Early ?Barremian
Classification
Saurischia Theropoda Tetanurae Coelurosauria Maniraptora Troodontidae
Diet
Carnivore
Fossilsite
Lower Yellow Cat Member, Cedar Mountain Formation, Grand County, Utah, US
Info
Abstract
Background
The theropod dinosaur family Troodontidae is known from the Upper Jurassic, Lower Cretaceous, and Upper Cretaceous of Asia and from the Upper Jurassic and Upper Cretaceous of North America. Before now no undisputed troodontids from North America have been reported from the Early Cretaceous. Methodology/Principal Findings: Herein we describe a theropod maxilla from the Lower Cretaceous Cedar Mountain Formation of Utah and perform a phylogenetic analysis to determine its phylogenetic position.
The specimen is distinctive enough to assign to a new genus and species, Geminiraptor suarezarum. Phylogenetic analysis places G. suarezarum within Troodontidae in an unresolved polytomy with Mei, Byronosaurus, Sinornithoides, Sinusonasus, and Troodon + (Saurornithoides + Zanabazar). Geminiraptor suarezarum uniquely exhibits extreme pneumatic inflation of the maxilla internal to the antorbital fossa such that the anterior maxilla has a triangular cross-section.
Unlike troodontids more closely related to Troodon, G. suarezarum exhibits bony septa between the dental alveoli and a promaxillary foramen that is visible in lateral view. Conclusions/Significance: This is the first report of a North American troodontid from the Lower Cretaceous. It therefore contributes to a fuller understanding of troodontid biogeography through time. It also adds to the known dinosaurian fauna of the Cedar Mountain Formation.
Holotype
The holotype specimen is CEUM (College of Eastern Utah Prehistoric Museum, Price Utah) 7319, a maxilla.
Etymology
The species name refers to Drs. Celina and Marina Suarez, the twin geologists who discovered the Suarez site. The genus name is from the Latin geminae (‘‘twins,’’ in honor of the Suarez sisters) and raptor (‘‘one who seizes or takes by force,’’ a common part of deinonychosaurian genus names).
Locality and horizon
The specimen is from the Suarez site, a dinosaur bonebed (dominated by the therizinosauroid Falcarius) in the lower Yellow Cat Member (Lower Cretaceous: Barremian?) of the Cedar Mountain Formation. The site is in western Grand County, Utah.
Diagnosis
Troodontid possessing a maxilla with extensive pneumatization internal to the antorbital fossa, inflating the bone so that it has a triangular cross-section; a large, craniocaudally elongate maxillary fenestra; a promaxillary fenestra that is visible in lateral view; craniocaudally narrow promaxillary strut and interfenestral strut; small, square dental alveoli with bony septa between them.