[D] Kayentavenator elysiae [sG] [T]
Describer
Gay 2010
Time
Jurassic Early Pliensbachian
Classification
Saurischia Theropoda Tetanurae
Diet
Carnivore
Fossilsite
Kayenta Formation, UCMP Locality V82309, Arizona, US
Info
Abstract
The early Jurassic Kayenta Formation of the Colorado Plateau of the American southwest has long been recognized for its important terrestrial vertebrate fauna, which includes the theropod Dilophosaurus wetherilli (Welles, 1970), the prosauropod Massospondylus (Attridge et al., 1987), the primitive thyrophoran Scutellosaurus lawleri (Colbert, 1981), the synapsid Dinnebitodon amarali (Sues, 1986), and the chelonian Kayentachelys (Gafney et al., 1987).
A new theropod, Kayentavenator elysiae, gen. et sp. nov., is described here, representing the first occurrence of the Tetanurae from the Kayenta Formation and the most primitive member of this diverse theropod clade yet found in North America. It should be noted that this specimen was originally assigned to Syntarsus kayentakatae (Rowe, 1989); careful study of the specimen in question shows that this diagnosis is incorrect.
Stratigraphy
The lower Jurassic Kayenta Formation, exposed in Arizona, Utah, Nevada, and Colorado, represents a dry period during the break-up of Pangaea. The Kayenta is characterized by deposits from braided streams flowing from the southeast (Luttrell, 1987), surrounded by localized vegetated areas, with large dune fields covering the areas between streams (Luttrell, 1987). UCMP locality V82309 is located in the Rock Head area of Northern Arizona (exact position on file at the University of California Museum of Paleontology), an area that was characterized by braided streams with scattered dune fields during the deposition of the Sandy Facies of the Kayenta Formation (Luttrell, 1987). This portion of the Kayenta ranges in age from late Sinemurian to early Pliensbachian (189 Ma). This dates Kayentavenator elysiae at approximately the same time as Cryolophosaurus ellitio (Hammer and Hickerson, 1994; Hammer, pers. comm., 2002), from Antarctica.
This discovery has implications for both theropod diversity and evolution, as well as biogeography. The first recorded appearances of this clade occur almost simultaneously, at opposite ends of Pangaea.With the Atlantic rift already occurring by this time in the Jurassic, forming a large geographic barrier between Gondwana and North America, the appearance of the Tetanurae must have occurred earlier than the late Sinemurian/late Pliensbachian. This would place tetanuran origins into the Triassic Period.
Holotype
UCMP 128659, a partial pelvis, femora, proximal tibiae, proximal fibula, and seven vertebrae, from one immature individual.
Etymology
The generic name comes from the Kayenta Formation, where the specimen was found, and the Latin venator for hunter. The specific epitaph honors Elysia Jennett, who has been both exceedingly helpful and supportive to the author during this and other research.
Locality and Horizon
Early Jurassic Kayenta Formation, Northern Arizona. UCMP Locality V82309, which has yielded the type and only known specimen of Kayentavenator elysiae.
Diagnosis
Apomorphies are: Ellipsoid acetabulum, fusion between the greater trochanter and the head of the femur; prominent mediodistal crest that extends 50% of the length of the femur; prominent accessory condyle on the medial femoral condyle; groove in dorsal surface of the femoral head, extending laterally; and highly constricted caudal centra.
Gay 2010
Time
Jurassic Early Pliensbachian
Classification
Saurischia Theropoda Tetanurae
Diet
Carnivore
Fossilsite
Kayenta Formation, UCMP Locality V82309, Arizona, US
Info
Abstract
The early Jurassic Kayenta Formation of the Colorado Plateau of the American southwest has long been recognized for its important terrestrial vertebrate fauna, which includes the theropod Dilophosaurus wetherilli (Welles, 1970), the prosauropod Massospondylus (Attridge et al., 1987), the primitive thyrophoran Scutellosaurus lawleri (Colbert, 1981), the synapsid Dinnebitodon amarali (Sues, 1986), and the chelonian Kayentachelys (Gafney et al., 1987).
A new theropod, Kayentavenator elysiae, gen. et sp. nov., is described here, representing the first occurrence of the Tetanurae from the Kayenta Formation and the most primitive member of this diverse theropod clade yet found in North America. It should be noted that this specimen was originally assigned to Syntarsus kayentakatae (Rowe, 1989); careful study of the specimen in question shows that this diagnosis is incorrect.
Stratigraphy
The lower Jurassic Kayenta Formation, exposed in Arizona, Utah, Nevada, and Colorado, represents a dry period during the break-up of Pangaea. The Kayenta is characterized by deposits from braided streams flowing from the southeast (Luttrell, 1987), surrounded by localized vegetated areas, with large dune fields covering the areas between streams (Luttrell, 1987). UCMP locality V82309 is located in the Rock Head area of Northern Arizona (exact position on file at the University of California Museum of Paleontology), an area that was characterized by braided streams with scattered dune fields during the deposition of the Sandy Facies of the Kayenta Formation (Luttrell, 1987). This portion of the Kayenta ranges in age from late Sinemurian to early Pliensbachian (189 Ma). This dates Kayentavenator elysiae at approximately the same time as Cryolophosaurus ellitio (Hammer and Hickerson, 1994; Hammer, pers. comm., 2002), from Antarctica.
This discovery has implications for both theropod diversity and evolution, as well as biogeography. The first recorded appearances of this clade occur almost simultaneously, at opposite ends of Pangaea.With the Atlantic rift already occurring by this time in the Jurassic, forming a large geographic barrier between Gondwana and North America, the appearance of the Tetanurae must have occurred earlier than the late Sinemurian/late Pliensbachian. This would place tetanuran origins into the Triassic Period.
Holotype
UCMP 128659, a partial pelvis, femora, proximal tibiae, proximal fibula, and seven vertebrae, from one immature individual.
Etymology
The generic name comes from the Kayenta Formation, where the specimen was found, and the Latin venator for hunter. The specific epitaph honors Elysia Jennett, who has been both exceedingly helpful and supportive to the author during this and other research.
Locality and Horizon
Early Jurassic Kayenta Formation, Northern Arizona. UCMP Locality V82309, which has yielded the type and only known specimen of Kayentavenator elysiae.
Diagnosis
Apomorphies are: Ellipsoid acetabulum, fusion between the greater trochanter and the head of the femur; prominent mediodistal crest that extends 50% of the length of the femur; prominent accessory condyle on the medial femoral condyle; groove in dorsal surface of the femoral head, extending laterally; and highly constricted caudal centra.