A limping dinosaur in the Late Jurassic: Pathologies in the pes of the neornithischian Othnielosaurus consors from the Morrison Formation (Upper Jurassic, USA)

Middle to Upper Jurassic strata in the Paradox Basin and Central Colorado trough (CCT; southwestern United States) record a pronounced change in sediment dispersal from dominantly aeolian deposition with an Appalachian source (Entrada Sandstone) to dominantly fluvial deposition with a source in the Mogollon and/or Sevier orogenic highlands (Salt Wash Member of the Morrison Formation). An enigmatic abundance of Cambrian (ca. 527–519 Ma) grains at this provenance transition in the CCT at Escalante Canyon, Colorado, was recently suggested to reflect a local sediment source from the Ancestral Front Range, despite previous interpretations that local basement uplifts were largely buried by Middle to Late Jurassic time. This study aims to delineate spatial and temporal patterns in provenance of these Jurassic sandstones containing Cambrian grains within the Paradox Basin and CCT using sandstone petrography, detrital zircon U-Pb geochronology, and detrital zircon trace elemental and rare-earth elemental (REE) geochemistry. We report 7887 new U-Pb detrital zircon analyses from 31 sandstone samples collected within seven transects in western Colorado and eastern Utah. Three clusters of zircon ages are consistently present (1.53–1.3 Ga, 1.3–0.9 Ga, and 500–300 Ma) that are interpreted to reflect sources associated with the Appalachian orogen in southeastern Laurentia (mid-continent, Grenville, Appalachian, and peri-Gondwanan terranes). Ca. 540–500 Ma zircon grains are anomalously abundant locally in the uppermost Entrada Sandstone and Wanakah Formation but are either lacking or present in small fractions in the overlying Salt Wash and Tidwell Members of the Morrison Formation. A comparison of zircon REE geochemistry between Cambrian detrital zircon and igneous zircon from potential sources shows that these 540–500 Ma detrital zircon are primarily magmatic. Although variability in both detrital and igneous REE concentrations precludes definitive identification of provenance, several considerations suggest that distal sources from the Cambrian granitic and rhyolitic provinces of the Southern Oklahoma aulacogen is also likely, in addition to a proximal source identified in the McClure Mountain syenite of the Wet Mountains, Colorado. The abundance of Cambrian grains in samples from the central CCT, particularly in the Entrada Sandstone and Wanakah Formation, suggests northwesterly sediment transport within the CCT, with sediment sourced from Ancestral Rocky Mountains uplifts of the southern Wet Mountains and/or Amarillo-Wichita Mountains in southwestern Oklahoma. The lack of Cambrian grains within the Paradox Basin suggests that the Uncompahgre uplift (southwestern Colorado) acted as a barrier to sediment transport from the CCT.

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Decomposition of dinosaurian remains inferred by invertebrate traces on vertebrate bone reveal new insights into Late Jurassic ecology, decay, and climate in western Colorado

PeerJ ◽

10.7717/peerj.9510 ◽

2020 ◽

Vol 8 ◽

pp. e9510

Author(s):

Julia B. McHugh ◽

Stephanie K. Drumheller ◽

Anja Riedel ◽

Miriam Kane

Keyword(s):

Late Jurassic ◽

Upper Jurassic ◽

Site Formation ◽

Morrison Formation ◽

Bone Surface ◽

The North ◽

Western Colorado ◽

Burial Rates ◽

Minimum Residence Time ◽

Taphonomic Analysis

A survey of 2,368 vertebrate fossils from the Upper Jurassic Mygatt-Moore Quarry (MMQ) (Morrison Formation, Brushy Basin Member) in western Colorado revealed 2,161 bone surface modifications on 884 specimens. This is the largest, site-wide bone surface modification survey of any Jurassic locality. Traces made by invertebrate actors were common in the assemblage, second in observed frequency after vertebrate bite marks. Invertebrate traces are found on 16.174% of the total surveyed material and comprise 20.148% of all identified traces. Six distinct invertebrate trace types were identified, including pits and furrows, rosettes, two types of bioglyph scrapes, bore holes and chambers. A minimum of four trace makers are indicated by the types, sizes and morphologies of the traces. Potential trace makers are inferred to be dermestid or clerid beetles, gastropods, an unknown necrophagous insect, and an unknown osteophagus insect. Of these, only gastropods are preserved at the site as body fossils. The remaining potential trace makers are part of the hidden paleodiversity from the North American Late Jurassic Period, revealed only through this ichnologic and taphonomic analysis. Site taphonomy suggests variable, but generally slow burial rates that range from months up to 6 years, while invertebrate traces on exposed elements indicate a minimum residence time of five months for carcasses with even few preserved invertebrate traces. These traces provide insight into the paleoecology, paleoclimate, and site formation of the MMQ, especially with regards to residence times of the skeletal remains on the paleolandscape. Comprehensive taphonomic studies, like this survey, are useful in exploring patterns of paleoecology and site formation, but they are also rare in Mesozoic assemblages. Additional work is required to determine if 16.174% is typical of bulk-collected fossils from Jurassic ecosystems in North America, or if the MMQ represents an unusual locality.

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The systematic position of the Late Jurassic alleged dinosaur Macelognathus (Crocodylomorpha: Sphenosuchia)

Canadian Journal of Earth Sciences ◽

10.1139/e05-005 ◽

2005 ◽

Vol 42 (3) ◽

pp. 307-321 ◽

Cited By ~ 19

Author(s):

Ursula B Göhlich ◽

Luis M Chiappe ◽

James M Clark ◽

Hans-Dieter Sues

Keyword(s):

Late Jurassic ◽

Upper Jurassic ◽

Systematic Position ◽

Lower Jurassic ◽

Late Triassic ◽

Morrison Formation ◽

Postcranial Skeleton ◽

Western Colorado ◽

New Material ◽

Limb Posture

Macelognathus vagans was described by O.C. Marsh in 1884, based on a mandibular symphysis from the Upper Jurassic Morrison Formation of Wyoming. Often considered a dinosaur but later tentatively referred to the Crocodylia, its phylogenetic identity has until now been enigmatic. New material of this species from the Morrison Formation of western Colorado demonstrates its affinities with basal crocodylomorphs commonly grouped together as the Sphenosuchia, which are characterized by a gracile postcranial skeleton with erect limb posture. Macelognathus shares features with Kayentasuchus from the Lower Jurassic Kayenta Formation of Arizona and Hallopus, which may be from the Morrison Formation of eastern Colorado. The new material constitutes the youngest definitive occurrence of a sphenosuchian, previously known from the Late Triassic to the Middle or Late? Jurassic.

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

Geology of the Intermountain West ◽

10.31711/giw.v7.pp29-67 ◽

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.

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The Morrison Formation Extinct Ecosystems Project

The UW National Parks Service Research Station Annual Reports ◽

10.13001/uwnpsrc.1996.3269 ◽

1996 ◽

Vol 20 ◽

pp. 20-27

Author(s):

Christine Turner ◽

Fred Peterson ◽

D. Chure ◽

T. Demko ◽

G. Engelmann

Keyword(s):

United States ◽

Late Jurassic ◽

The United States ◽

Upper Jurassic ◽

Morrison Formation

The Morrison Project is a multidisciplinary effort to interpret the ancient ecosystem that was present in the Western Interior of the United States during deposition of the Upper Jurassic Morrison Formation. The project began in June of 1994 and the first two years of research (1994-95, 1995-96) were devoted primarily to identifying problems and gathering information that would form the basis for later interpretations. Efforts during the final year (1996-97) were directed toward resolving remaining problems or conflicting findings and synthesizing the various research endeavors into a reconstruction of the Late Jurassic ecosystem.

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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 ◽

10.7717/peerj.5250 ◽

2018 ◽

Vol 6 ◽

pp. e5250 ◽

Cited By ~ 2

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.

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

Geology of the Intermountain West ◽

10.31711/giw.v5.pp95-103 ◽

2018 ◽

Vol 5 ◽

pp. 95-103 ◽

Cited By ~ 2

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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Anatomy and systematics of the diplodocoid Amphicoelias altus supports high sauropod dinosaur diversity in the Upper Jurassic Morrison Formation of the USA

Royal Society Open Science ◽

10.1098/rsos.210377 ◽

2021 ◽

Vol 8 (6) ◽

pp. 210377

Author(s):

Philip D. Mannion ◽

Emanuel Tschopp ◽

John A. Whitlock

Keyword(s):

Late Jurassic ◽

Phylogenetic Analyses ◽

Upper Jurassic ◽

Phylogenetic Position ◽

Morrison Formation ◽

Growth Series ◽

Distinct Genus ◽

The Usa ◽

Phylogenetic Signature ◽

High Diversity

Sauropod dinosaurs were an abundant and diverse component of the Upper Jurassic Morrison Formation of the USA, with 24 currently recognized species. However, some authors consider this high diversity to have been ecologically unviable and the validity of some species has been questioned, with suggestions that they represent growth series (ontogimorphs) of other species. Under this scenario, high sauropod diversity in the Late Jurassic of North America is greatly overestimated. One putative ontogimorph is the enigmatic diplodocoid Amphicoelias altus , which has been suggested to be synonymous with Diplodocus . Given that Amphicoelias was named first, it has priority and thus Diplodocus would become its junior synonym. Here, we provide a detailed re-description of A. altus in which we restrict it to the holotype individual and support its validity, based on three autapomorphies. Constraint analyses demonstrate that its phylogenetic position within Diplodocoidea is labile, but it seems unlikely that Amphicoelias is synonymous with Diplodocus . As such, our re-evaluation also leads us to retain Diplodocus as a distinct genus. There is no evidence to support the view that any of the currently recognized Morrison sauropod species are ontogimorphs. Available data indicate that sauropod anatomy did not dramatically alter once individuals approached maturity. Furthermore, subadult sauropod individuals are not prone to stemward slippage in phylogenetic analyses, casting doubt on the possibility that their taxonomic affinities are substantially misinterpreted. An anatomical feature can have both an ontogenetic and phylogenetic signature, but the former does not outweigh the latter when other characters overwhelmingly support the affinities of a taxon. Many Morrison Formation sauropods were spatio-temporally and/or ecologically separated from one another. Combined with the biases that cloud our reading of the fossil record, we contend that the number of sauropod dinosaur species in the Morrison Formation is currently likely to be underestimated, not overestimated.

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

Geology of the Intermountain West ◽

10.31711/giw.v5i0.20 ◽

2018 ◽

Vol 5 ◽

pp. 95-103 ◽

Cited By ~ 1

Author(s):

Julia B. 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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DISPERSED PALYNOMORPH AND CUTICLE ASSEMBLAGES FROM THE LATE JURASSIC MORRISON FORMATION, SOUTHEASTERN UTAH: FLORISTIC AND PALEOCLIMATE IMPLICATIONS

10.1130/abs/2018am-322649 ◽

2018 ◽

Cited By ~ 1

Author(s):

Nina L. Baghai-Riding ◽

◽

James I. Kirkland ◽

Kelli C. Trujillo ◽

Kevin R. Chamberlain ◽

...

Keyword(s):

Late Jurassic ◽

Morrison Formation

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