Revised chronostratigraphy of the Lower Chinle Formation strata in Arizona and New Mexico (USA): High-precision U-Pb geochronological constraints on the Late Triassic evolution of dinosaurs

2014 ◽  
Vol 314 (6) ◽  
pp. 981-1008 ◽  
Author(s):  
J. Ramezani ◽  
D. E. Fastovsky ◽  
S. A. Bowring
Keyword(s):  
New Mexico ◽  
High Precision ◽  
Late Triassic ◽  
Chinle Formation ◽  
Geochronological Constraints

scholarly journals The first occurrence of the enigmatic archosaur Crosbysaurus (Heckert 2004) from the Chinle Formation of Southern Utah

2014 ◽  
Author(s):  
Robert J Gay ◽  
Isabella St. Aude
Keyword(s):  
New Mexico ◽  
Close Association ◽  
First Record ◽  
Geographic Range ◽  
Type Locality ◽  
Late Triassic ◽  
Southern Area ◽  
Chinle Formation ◽  
First Occurrence ◽  
Unique Compound

Originally identified as an ornithisichian dinosaur, Crosbysaurus has been found in New Mexico, Arizona, and the type locality in Texas. The genus has been reassessed by other workers in light of revelations about the postcrania of another putative Triassic ornithischian, Revueltosaurus. The understanding of Triassic dental faunas has become more complicated by the extreme convergence between pseudosuchian archosaurus and ornithichian dinosaur dental morphologies. We report here on a new specimen of Crosbysaurus from the Petrified Forest Member of the Chinle Formation at Comb Ridge in southeastern Utah. This new specimen is assigned to Crosbysaurus on the basis of the unique compound posterior denticles, mediolateral width, and curvature. While this specimen, MNA V10666, does not help resolve the affinities of Crosbysaurus it does represent an approximately 250 kilometer extension of the geographic range of this taxon. This is the first record of this taxon in Utah and as such it represents the northernmost known record of Crosbysaurus. This indicates that Crosbysaurus was not limited to the southern area of Chinle/Dockum deposition but instead was widespread across the paleoriver systems of the Late Triassic in western Pangea. The specimen we report on here was found in close association with a typical Late Triassic Chinle fauna, including phytosaurs, metoposaurs, and dinosauromorphs.

scholarly journals The first occurrence of the enigmatic archosauriform Crosbysaurus Heckert 2004 from the Chinle Formation of Southern Utah

2015 ◽  
Author(s):  
Robert J Gay ◽  
Isabella St. Aude
Keyword(s):  
North Carolina ◽  
New Mexico ◽  
Close Association ◽  
First Record ◽  
Geographic Range ◽  
Type Locality ◽  
Late Triassic ◽  
Chinle Formation ◽  
First Occurrence ◽  
Unique Compound

Originally identified as an ornithischian dinosaur, Crosbysaurus harrisae has been found in New Mexico, Arizona, and its type locality in Texas, as well as in North Carolina. The genus has been reassessed by other workers in light of reinterpretations about the postcrania of another putative Triassic ornithischian, Revueltosaurus. The understanding of Triassic dental faunas has become more complicated by the extreme convergence between pseudosuchian archosaurs and ornithischian dinosaur dental morphologies. We report here on a new specimen of Crosbysaurus (MNA V10666) from the Chinle Formation at Comb Ridge in southeastern Utah. This new specimen is assigned to Crosbysaurus sp. on the basis of the unique compound posterior denticles, labiolingual width, and curvature. While MNA V10666 does not help resolve the affinities of Crosbysaurus, it does represent the extension of the geographic range of this taxon for approximately 250 kilometers. This is the first record of the genus Crosbysaurus in Utah and as such it represents the northernmost known record of this taxon. This indicates that Crosbysaurus was not limited to the southern area of the Chinle/Dockum deposition but instead was widespread across the Late Triassic paleoriver systems of western Pangea. The reported specimen was found in close association with a typical Late Triassic Chinle fauna, including phytosaurs, metoposaurs, and dinosauromorphs.

scholarly journals A new rauisuchid (Archosauria, Pseudosuchia) from the Upper Triassic (Norian) of New Mexico increases the diversity and temporal range of the clade

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2336 ◽  
Author(s):  
Emily J. Lessner ◽  
Michelle R. Stocker ◽  
Nathan D. Smith ◽  
Alan H. Turner ◽  
Randall B. Irmis ◽  
...  
Keyword(s):  
United States ◽  
New Mexico ◽  
Upper Triassic ◽  
Late Triassic ◽  
Morphological Evidence ◽  
Ventral Margin ◽  
Close Phylogenetic Relationship ◽  
Chinle Formation ◽  
Geographic Separation ◽  
A New Species

Rauisuchids are large (2–6 m in length), carnivorous, and quadrupedal pseudosuchian archosaurs closely related to crocodylomorphs. Though geographically widespread, fossils of this clade are relatively rare in Late Triassic assemblages. The middle Norian (∼212 Ma) Hayden Quarry of northern New Mexico, USA, in the Petrified Forest Member of the Chinle Formation, has yielded isolated postcranial elements and associated skull elements of a new species of rauisuchid.Vivaron haydenigen. et. sp. nov. is diagnosed by the presence of two posteriorly directed prongs at the posterior end of the maxilla for articulation with the jugal. The holotype maxilla and referred elements are similar to those of the rauisuchidPostosuchus kirkpatrickifrom the southwestern United States, butV. haydenishares several maxillary apomorphies (e.g., a distinct dropoff to the antorbital fossa that is not a ridge, a straight ventral margin, and a well defined dental groove) with the rauisuchidTeratosaurus suevicusfrom the Norian of Germany. Despite their geographic separation, this morphological evidence implies a close phylogenetic relationship betweenV. haydeniandT. suevicus. The morphology preserved in the new Hayden Quarry rauisuchidV. haydenisupports previously proposed and new synapomorphies for nodes within Rauisuchidae. The discovery ofVivaron haydenireveals an increased range of morphological disparity for rauisuchids from the low-paleolatitude Chinle Formation and a clear biogeographic connection with high paleolatitude Pangea.

scholarly journals The first occurrence of the enigmatic archosauriform Crosbysaurus Heckert 2004 from the Chinle Formation of Southern Utah

2015 ◽  
Author(s):  
Robert J Gay ◽  
Isabella St. Aude
Keyword(s):  
North Carolina ◽  
New Mexico ◽  
Close Association ◽  
First Record ◽  
Geographic Range ◽  
Type Locality ◽  
Late Triassic ◽  
Chinle Formation ◽  
First Occurrence ◽  
Unique Compound

Originally identified as an ornithischian dinosaur, Crosbysaurus harrisae has been found in New Mexico, Arizona, and its type locality in Texas, as well as in North Carolina. The genus has been reassessed by other workers in light of reinterpretations about the postcrania of another putative Triassic ornithischian, Revueltosaurus. The understanding of Triassic dental faunas has become more complicated by the extreme convergence between pseudosuchian archosaurs and ornithischian dinosaur dental morphologies. We report here on a new specimen of Crosbysaurus (MNA V10666) from the Chinle Formation at Comb Ridge in southeastern Utah. This new specimen is assigned to Crosbysaurus sp. on the basis of the unique compound posterior denticles, labiolingual width, and curvature. While MNA V10666 does not help resolve the affinities of Crosbysaurus, it does represent the extension of the geographic range of this taxon for approximately 250 kilometers. This is the first record of the genus Crosbysaurus in Utah and as such it represents the northernmost known record of this taxon. This indicates that Crosbysaurus was not limited to the southern area of the Chinle/Dockum deposition but instead was widespread across the Late Triassic paleoriver systems of western Pangea. The reported specimen was found in close association with a typical Late Triassic Chinle fauna, including phytosaurs, metoposaurs, and dinosauromorphs.

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