Planicoxa
Encyclopedia
Planicoxa is a genus
of advanced iguanodont
ian dinosaur
from the Early Cretaceous
of North America. It is known from the partial skeletons of several individual specimens. Its fossils were discovered in Utah
and South Dakota
, United States
.
The type species for the genus is Planicoxa venenica, first described by Tony DiCroce and Kenneth Carpenter
in 2001. Its discovery was made in the Poison Strip Sandstone Member of the Cedar Mountain Formation
in Grand County, Utah
, United States. Planicoxa refers to the flat appearance of the ilium formed by horizontal folding over of the postacetabular process (rear portion of the ilium), the defining characteristic of the genus; venenica, the species name, is Latin for “poison” in reference to the Poison Strip Sandstone Member of the Cedar Mountain Formation where the discovery was made. This new taxon is represented by a well-preserved ilium, femora, tibiae, and vertebrae, as well as other material. The femora are classical ornithopod, but the ilium has a short, horizontal postacetabular process that is functionally an antitrochanter. The discovery of P. venenica adds significant new information to the Barremian-Albian fauna of the Cedar Mountain Formation.
A second species, P. depressa, was created by Carpenter and Wilson (2008) for material previously named Camptosaurus depressus by Charles Gilmore in 1909. That material was collected from the Lakota Formation
near the town of Hot Springs, South Dakota
. It too has the odd flat ilium formed by the horizontal postacetabular process. This species differs from P. venenica in that the ilium is not as arched, has a thicker (more robust) preacetabular process (long, forward projection of the ilium), a shallower acetabular notch (hip-socket), and a proportionally narrower brevis shelf (a shelf for muscles on the inside of the rear part of the ilium). It is known from some vertebrae and two ilia. Isolated iguanodontid bones from the Lakota Formation probably belong to this species. In 2011
, it was assigned to its own genus, Osmakasaurus
.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of advanced iguanodont
Iguanodont
Iguanodonts were herbivorous dinosaurs that lived from the mid-Jurassic to Late Cretaceous. Some members include Camptosaurus, Callovosaurus, Iguanodon, Ouranosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodonts were one of the first groups of dinosaurs to be found...
ian dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
of North America. It is known from the partial skeletons of several individual specimens. Its fossils were discovered in Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
and South Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
.
The type species for the genus is Planicoxa venenica, first described by Tony DiCroce and Kenneth Carpenter
Kenneth Carpenter
Kenneth Carpenter is a paleontologist. He is the museum director of the USU Eastern Prehistoric Museum and author or co-author of a number of books on dinosaurs and Mesozoic life...
in 2001. Its discovery was made in the Poison Strip Sandstone Member of the Cedar Mountain Formation
Cedar Mountain Formation
The Cedar Mountain Formation is the name given to distinctive sedimentary rocks in eastern Utah that occur between the underlying Morrison Formation and overlying Naturita Formation . It is composed of non-marine sediments, that is, sediments deposited in rivers, lakes and on flood plains...
in Grand County, Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, United States. Planicoxa refers to the flat appearance of the ilium formed by horizontal folding over of the postacetabular process (rear portion of the ilium), the defining characteristic of the genus; venenica, the species name, is Latin for “poison” in reference to the Poison Strip Sandstone Member of the Cedar Mountain Formation where the discovery was made. This new taxon is represented by a well-preserved ilium, femora, tibiae, and vertebrae, as well as other material. The femora are classical ornithopod, but the ilium has a short, horizontal postacetabular process that is functionally an antitrochanter. The discovery of P. venenica adds significant new information to the Barremian-Albian fauna of the Cedar Mountain Formation.
A second species, P. depressa, was created by Carpenter and Wilson (2008) for material previously named Camptosaurus depressus by Charles Gilmore in 1909. That material was collected from the Lakota Formation
Lakota Formation
The Lakota Formation is a sequence of rocks from the Barremian epoch from Western North America. Located in South Dakota, the name is derived from the Lakota Native American tribe....
near the town of Hot Springs, South Dakota
Hot Springs, South Dakota
Hot Springs is a city in Fall River County, South Dakota, United States. As of the 2010 census, the city population was 3,711. It is the county seat of Fall River County...
. It too has the odd flat ilium formed by the horizontal postacetabular process. This species differs from P. venenica in that the ilium is not as arched, has a thicker (more robust) preacetabular process (long, forward projection of the ilium), a shallower acetabular notch (hip-socket), and a proportionally narrower brevis shelf (a shelf for muscles on the inside of the rear part of the ilium). It is known from some vertebrae and two ilia. Isolated iguanodontid bones from the Lakota Formation probably belong to this species. In 2011
2011 in paleontology
-Lobopods:-Arachnids:-Insects:-Newly named jawless vertebrates:-Newly named acanthodian:-Newly named cartilaginous fishes:-Newly named bony fishes:-Newly named lepospondyls:-Newly named temnospondyls:-Newly named lissamphibians:...
, it was assigned to its own genus, Osmakasaurus
Osmakasaurus
Osmakasaurus is a genus of herbivorous iguanodontian dinosaur. It is a basal iguanodontian which lived during the lower Cretaceous period in what is now Buffalo Gap of South Dakota, USA. It is known from the Chilson Member of the Lakota Formation. This genus was named by Andrew T. McDonald in 2011...
.