The record of volcanism in the Brushy Basin Member of the Morrison Formation: Implications for the Late Jurassic of western North America

2015 ◽  
pp. 399-439 ◽  
Author(s):  
Eric H. Christiansen ◽  
Bart J. Kowallis ◽  
Michael J. Dorais ◽  
Garret L. Hart ◽  
Chloe N. Mills ◽  
...  
Keyword(s):  
North America ◽  
Late Jurassic ◽  
Morrison Formation ◽  
Western North America

scholarly journals New Cretaceous lungfishes (Dipnoi, Ceratodontidae) from western North America

2016 ◽  
Vol 91 (1) ◽  
pp. 146-161 ◽  
Author(s):  
Joseph A. Frederickson ◽  
Richard L. Cifelli
Keyword(s):  
New Species ◽  
North America ◽  
Late Jurassic ◽  
Salt Water ◽  
Time Interval ◽  
Morrison Formation ◽  
Western North America ◽  
Fold System ◽  
Species Groups ◽  
New Occurrences

AbstractCeratodontid lungfishes are generally rare, poorly represented elements of North America’s Mesozoic ecosystems, with previously known maximum diversity in the Late Jurassic. Herein we describe four new species of the form genusCeratodus, from the Cretaceous of the Western Interior, considerably expanding fossil representation of post-Triassic dipnoans in North America. To model taxonomic and morphologic diversity, we adopt a four-fold system of phenetically based species groups, named for exemplars from the Morrison Formation.Ceratodus kirklandin. sp. (Potamoceratodus guentherigroup) andC.kempaen. sp. (C.frazierigroup) represent a hitherto unsampled time interval, the Valanginian.Ceratodus nirumbeen. sp. andC.molossusn. sp. extend the temporal ranges of theC.fossanovumandC.robustusgroups upward to the Albian and Cenomanian, respectively. These new occurrences show that ceratodontids maintained their highest diversity from the Late Jurassic through the mid-Cretaceous (Albian–Cenomanian), an interval of ~60 Myr. The existing record suggests that some of the later (mid-Cretaceous) ceratodontids may have been tolerant of salt water; to date, there is no evidence that they aestivated. Only a few occurrences are known from horizons younger than Cenomanian. Demise of ceratodontids appears to be part of a broader pattern of turnover that occurred at the Cenomanian-Turonian boundary in North America.

scholarly journals Cranial anatomy of Allosaurus jimmadseni, a new species from the lower part of the Morrison Formation (Upper Jurassic) of Western North America

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e7803 ◽  
Author(s):  
Daniel J. Chure ◽  
Mark A. Loewen
Keyword(s):  
New Species ◽  
North America ◽  
Phylogenetic Analyses ◽  
Upper Jurassic ◽  
Morrison Formation ◽  
Ventral Margin ◽  
Western North America ◽  
Theropod Dinosaur ◽  
Theropod Dinosaurs ◽  
A New Species

Allosaurus is one of the best known theropod dinosaurs from the Jurassic and a crucial taxon in phylogenetic analyses. On the basis of an in-depth, firsthand study of the bulk of Allosaurus specimens housed in North American institutions, we describe here a new theropod dinosaur from the Upper Jurassic Morrison Formation of Western North America, Allosaurus jimmadseni sp. nov., based upon a remarkably complete articulated skeleton and skull and a second specimen with an articulated skull and associated skeleton. The present study also assigns several other specimens to this new species, Allosaurus jimmadseni, which is characterized by a number of autapomorphies present on the dermal skull roof and additional characters present in the postcrania. In particular, whereas the ventral margin of the jugal of Allosaurus fragilis has pronounced sigmoidal convexity, the ventral margin is virtually straight in Allosaurus jimmadseni. The paired nasals of Allosaurus jimmadseni possess bilateral, blade-like crests along the lateral margin, forming a pronounced nasolacrimal crest that is absent in Allosaurus fragilis.

scholarly journals A Late Jurassic salamander (Amphibia: Caudata) from the Morrison Formation of North America

2005 ◽  
Vol 143 (4) ◽  
pp. 599-616 ◽  
Author(s):  
S. E. EVANS ◽  
C. LALLY ◽  
D. C. CHURE ◽  
A. ELDER ◽  
J. A. MAISANO
Keyword(s):  
North America ◽  
Late Jurassic ◽  
Morrison Formation

scholarly journals An unusually diverse northern biota from the Morrison Formation (Upper Jurassic), Black Hills, Wyoming

2020 ◽  
Vol 7 ◽  
pp. 29-67
Author(s):  
John Foster ◽  
Darrin Pagnac ◽  
ReBecca Hunt-Foster
Keyword(s):  
North America ◽  
Late Jurassic ◽  
Upper Jurassic ◽  
River Channel ◽  
Black Hills ◽  
Morrison Formation ◽  
Vertebrate Fauna ◽  
Type Area ◽  
First Occurrence

The Little Houston Quarry in the Black Hills of Wyoming contains the most diverse vertebrate fauna in the Morrison Formation (Upper Jurassic) north of Como Bluff and the second-most diverse in the entire formation, after Reed’s Quarry 9. The deposit was an occasionally reactivated abandoned river channel, in interbedded green mudstone and laminated green-gray siltstone above a channel sandstone. The dinosaur material is densely distributed and is disarticulated to articulated, with several associated skeletons. The biota contains charophytes, horsetails, a possible seed fern, possible conifers, gastropods, two types of unionoid bivalves, diplostracans (“conchostracans”), a malacostracan, ray-finned fish, lungfish, a frog, salamanders, two types of turtles, rhynchocephalians, a lizard, choristoderes, two types of crocodyliforms, a pterosaur, Allosaurus and several types of small theropods including Tanycolagreus? and probable dromaeosaurids, numerous Camarasaurus and a diplodocine sauropod, a stegosaur, the neornithischian Nanosaurus, and the mammals Docodon, Amblotherium, and a multituberculate. Among these taxa, one of the unionoid bivalves, an atoposaurid crocodyliform, and the species of Amblotherium, which appear to be new and unique to the locality so far. The Docodon material may represent the first occurrence of D. apoxys outside of its type area in Colorado. Additionally, small, unusual theropod tooth types reported here may represent the first Late Jurassic occurrence of cf. Richardoestesia in North America and a possible abelisauroid, respectively.

scholarly journals The real Bigfoot: a pes from Wyoming, USA is the largest sauropod pes ever reported and the northern-most occurrence of brachiosaurids in the Upper Jurassic Morrison Formation

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5250 ◽  
Author(s):  
Anthony Maltese ◽  
Emanuel Tschopp ◽  
Femke Holwerda ◽  
David Burnham
Keyword(s):  
North America ◽  
Late Jurassic ◽  
Articular Surface ◽  
Upper Jurassic ◽  
Morrison Formation ◽  
The Real ◽  
Large Size ◽  
Distal Shaft ◽  
Distal Articular Surface ◽  
Ventral Process

A set of associated left pedal elements of a sauropod dinosaur from the Upper Jurassic Morrison Formation in Weston County, Wyoming, is described here. Several camarasaurids, a nearly complete small brachiosaur, and a small diplodocid have been found at this locality, but none match the exceptionally large size of the pedal elements. Next to the associated pedal elements, an isolated astragalus, phalanx and ungual were found, which match the large metatarsals in size. The elements cannot be ascribed to diplodocids due to the lack of a ventral process of metatarsal I. Moreover, the morphology of metatarsal V has a broad proximal end, with a long and narrow distal shaft, which differs fromCamarasaurus. The size of the material and a medially beveled distal articular surface of metatarsal IV imply an identification as a brachiosaurid. This is the largest pes ever reported from a sauropod dinosaur and represents the first confirmed pedal brachiosaur elements from the Late Jurassic of North America. Furthermore, this brachiosaur material (the pes and the small nearly complete specimen) is the northernmost occurrence of brachiosaurids in the Morrison Formation.

scholarly journals Notes on the cheek region of the Late Jurassic theropod dinosaur Allosaurus

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8493
Author(s):  
Serjoscha W. Evers ◽  
Christian Foth ◽  
Oliver W.M. Rauhut
Keyword(s):  
North America ◽  
19Th Century ◽  
Late Jurassic ◽  
Morrison Formation ◽  
Late 19Th Century ◽  
Theropod Dinosaur ◽  
European Species ◽  
Theropod Dinosaurs ◽  
The Common ◽  
Iconic Status

Allosaurus, from the Late Jurassic of North America and Europe, is a model taxon for Jurassic basal tetanuran theropod dinosaurs. It has achieved an almost iconic status due to its early discovery in the late, 19th century, and due to the abundance of material from the Morrison Formation of the western U.S.A., making Allosaurus one of the best-known theropod taxa. Despite this, various aspects of the cranial anatomy of Allosaurus are surprisingly poorly understood. Here, we discuss the osteology of the cheek region, comprised by the jugal, maxilla, and lacrimal. This region of the skull is of importance for Allosaurus taxonomy and phylogeny, particularly because Allosaurus has traditionally been reconstructed with an unusual cheek configuration, and because the European species Allosaurus europaeus has been said to be different from North American material in the configuration of these bones. Based on re-examination of articulated and disarticulated material from a number of repositories, we show that the jugal participates in the antorbital fenestra, contradicting the common interpretation. The jugal laterally overlies the lacrimal, and forms an extended antorbital fossa with this bone. Furthermore, we document previously unrecorded pneumatic features of the jugal of Allosaurus.

scholarly journals Evidence for niche partitioning among ground-height browsing sauropods from the Upper Jurassic Morrison Formation of North America

2018 ◽  
Vol 5 ◽  
pp. 95-103 ◽  
Author(s):  
Julia McHugh
Keyword(s):  
Computed Tomography ◽  
North America ◽  
Late Jurassic ◽  
Feeding Strategy ◽  
Niche Partitioning ◽  
Upper Jurassic ◽  
Ct Scans ◽  
Close Relative ◽  
Morrison Formation ◽  
High Count

Two tooth-bearing snout fragments from a diplodocid sauropod from the Brushy Basin Member of the Morrison Formation (Upper Jurassic) excavated from the Mygatt-Moore Quarry in Rabbit Valley, Colora­do are described. The Mygatt-Moore Quarry has produced thousands of vertebrate fossils from the Brushy Basin Member, with the diplodocid Apatosaurus cf. louisae and the tetanuran Allosaurus fragilis dominat­ing the assemblage. Additionally, remains of another diplodocid, Diplodocus sp., have been found near the quarry within Rabbit Valley. Both specimens in this study preserve eight teeth per alveolar position, as observed through broken surfaces at the gross anatomical level and also through computed tomography (CT) scans. This is inconsistent with the genus Diplodocus sp., which has been previously shown to have a maximum of six teeth per alveolus. The presence of eight replacement teeth per alveolus has previously only been reported in the Cretaceous rebbachisaurid Nigersaurus taqueti, which has been interpreted to have occupied a similar ground-height browsing feeding strategy to both Diplodocus and Apatosaurus. This is the first report of this type of high-count replacement teeth in a diplodocid sauropod from the Morrison Formation. The high number of replacement teeth in a close relative to the contemporaneous Diplodocus provides evidence for niche partitioning among the contemporary ground-height browsing diplodocid sauropods of the Late Jurassic Period in North America.

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