scholarly journals A tyrannosauroid metatarsus from the Merchantville formation of Delaware increases the diversity of non-tyrannosaurid tyrannosauroids on Appalachia

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e4123 ◽  
Author(s):  
Chase D. Brownstein
Keyword(s):  
Phylogenetic Analysis ◽  
North America ◽  
Late Cretaceous ◽  
Fossil Record ◽  
Morphological Features ◽  
The West ◽  
Intermediate Grade

During the Late Cretaceous, the continent of North America was divided into two sections: Laramidia in the west and Appalachia in the east. Although the sediments of Appalachia recorded only a sparse fossil record of dinosaurs, the dinosaur faunas of this landmass were different in composition from those of Laramidia. Represented by at least two taxa (Appalachiosaurus montgomeriensis and Dryptosaurus aquilunguis), partial and fragmentary skeletons, and isolated bones, the non-tyrannosaurid tyrannosauroids of the landmass have attracted some attention. Unfortunately, these eastern tyrants are poorly known compared to their western contemporaries. Here, one specimen, the partial metatarsus of a tyrannosauroid from the Campanian Merchantville Formation of Delaware, is described in detail. The specimen can be distinguished from A. montgomeriensis and D. aquilunguis by several morphological features. As such, the specimen represents a potentially previously unrecognized taxon of tyrannosauroid from Appalachia, increasing the diversity of the clade on the landmass. Phylogenetic analysis and the morphology of the bones suggest the Merchantville specimen is a tyrannosauroid of “intermediate” grade, thus supporting the notion that Appalachia was a refugium for relict dinosaur clades.

scholarly journals A Tyrannosauroid Metatarsus from the Merchantville Formation of New Jersey increases the diversity of non-Tyrannosaurid Tyrannosauroids on Appalachia

2017 ◽  
Author(s):  
Chase D Brownstein
Keyword(s):  
New Jersey ◽  
North America ◽  
Individual Variation ◽  
Fossil Record ◽  
Morphological Features ◽  
Similar Amount ◽  
The West ◽  
Similarities And Differences ◽  
Significant Attention

For almost the entirely of the latter half of the Cretaceous, the continent of North America was divided into two sections, Laramidia in the west and Appalachia in the east. Unfortunately, this latter landmass recorded only a sparse fossil record of dinosaurs, obscuring those forms which must have occupied the eastern portion of North America during this time. Appalachian dinosaur faunas, though obscure, do seem to be different in composition from Laramidian ones. One particular element of Appalachian faunas that has attracted significant attention are the non-tyrannosaurid tyrannosauroids of the continent. Tyrannosauroids on Appalachia, though represented by at least two taxa (Appalachiosaurus montgomeriensis and Dryptosaurus aquilunguis), as well as many partial and fragmentary skeletons and elements, are nevertheless poorly know when compared to their western contemporaries. Here, one specimen, the partial metatarsus of a tyrannosauroid from the Campanian Merchantville Formation of New Jersey, is described in detail. The specimen may be differentiated from Appalachiosaurus montgomeriensis, Dryptosaurus aquilunguis, and an unnamed specimen from the Maastrichtian of New Jersey by several notable morphological features outside the spectrum of individual variation, as well as by factoring in biogeographical considerations. The new specimen thus has significance for representing a new morphotype of tyrannosauroid from Appalachia, suggesting greater diversity of the clade on the landmass. Because of this, tyrannosaur diversity in the Campanian of Appalachia was compared to the diversity of tyrannosaurs in Laramidia during the same period to analyze the similarities and differences between the biogeography of tyrannosaurs on each landmass. The results suggest that Appalachian non-tyrannosaurid tyrannosauroids experienced a similar amount of diversity to tyrannosaurids in Laramidia during the Campanian.

scholarly journals A Tyrannosauroid Metatarsus from the Merchantville Formation of New Jersey increases the diversity of non-Tyrannosaurid Tyrannosauroids on Appalachia

2017 ◽  
Author(s):  
Chase D Brownstein
Keyword(s):  
New Jersey ◽  
North America ◽  
Individual Variation ◽  
Fossil Record ◽  
Morphological Features ◽  
Similar Amount ◽  
The West ◽  
Similarities And Differences ◽  
Significant Attention

For almost the entirely of the latter half of the Cretaceous, the continent of North America was divided into two sections, Laramidia in the west and Appalachia in the east. Unfortunately, this latter landmass recorded only a sparse fossil record of dinosaurs, obscuring those forms which must have occupied the eastern portion of North America during this time. Appalachian dinosaur faunas, though obscure, do seem to be different in composition from Laramidian ones. One particular element of Appalachian faunas that has attracted significant attention are the non-tyrannosaurid tyrannosauroids of the continent. Tyrannosauroids on Appalachia, though represented by at least two taxa (Appalachiosaurus montgomeriensis and Dryptosaurus aquilunguis), as well as many partial and fragmentary skeletons and elements, are nevertheless poorly know when compared to their western contemporaries. Here, one specimen, the partial metatarsus of a tyrannosauroid from the Campanian Merchantville Formation of New Jersey, is described in detail. The specimen may be differentiated from Appalachiosaurus montgomeriensis, Dryptosaurus aquilunguis, and an unnamed specimen from the Maastrichtian of New Jersey by several notable morphological features outside the spectrum of individual variation, as well as by factoring in biogeographical considerations. The new specimen thus has significance for representing a new morphotype of tyrannosauroid from Appalachia, suggesting greater diversity of the clade on the landmass. Because of this, tyrannosaur diversity in the Campanian of Appalachia was compared to the diversity of tyrannosaurs in Laramidia during the same period to analyze the similarities and differences between the biogeography of tyrannosaurs on each landmass. The results suggest that Appalachian non-tyrannosaurid tyrannosauroids experienced a similar amount of diversity to tyrannosaurids in Laramidia during the Campanian.

scholarly journals Prootic anatomy of a juvenile tyrannosauroid from New Jersey and its implications for the morphology and evolution of the tyrannosauroid braincase

2018 ◽  
Author(s):  
Chase D Brownstein
Keyword(s):  
Phylogenetic Analysis ◽  
North America ◽  
Northern Hemisphere ◽  
Late Cretaceous ◽  
Coastal Plain ◽  
Fossil Record ◽  
Atlantic Coastal Plain ◽  
Western Interior Seaway ◽  
Large Predator ◽  
Atlantic Coastal

Among the most recognizable theropods are the tyrannosauroids, a group of small to large carnivorous coelurosaurian dinosaurs that inhabited the majority of the northern hemisphere during the Cretaceous and came to dominate large predator niches in North American and Asian ecosystems by the end of the Mesozoic era. The clade is among the best-represented of dinosaur groups in the notoriously sparse fossil record of Appalachia, the Late Cretaceous landmass that occupied the eastern portion of North America after its formation from the transgression of the Western Interior Seaway. Here, the prootic of a juvenile tyrannosauroid collected from the middle-late Campanian Marshalltown Formation of the Atlantic Coastal Plain is described, remarkable for being the first concrete evidence of juvenile theropods in that plain during the time of the existence of Appalachia and the only portion of theropod braincase known from the landmass. Phylogenetic analysis recovers the specimen as an “intermediate” tyrannosauroid of similar grade to Dryptosaurus and Appalachiosaurus. Comparisons with the corresponding portions of other tyrannosauroid braincases suggest that the Ellisdale prootic is more similar to Turonian forms in morphology than to the derived tyrannosaurids of the Late Cretaceous, thus supporting the hypothesis that Appalachian tyrannosauroids and other vertebrates were relict forms surviving in isolation from their derived counterparts in Eurasia.

scholarly journals A Tyrannosauroid Metatarsus from the Merchantville Formation of New Jersey increases the diversity of non-Tyrannosaurid Tyrannosauroids on Appalachia

2017 ◽  
Author(s):  
Chase D Brownstein
Keyword(s):  
New Jersey ◽  
North America ◽  
Individual Variation ◽  
Fossil Record ◽  
Morphological Features ◽  
Similar Amount ◽  
The West ◽  
Similarities And Differences ◽  
Significant Attention

For almost the entirely of the latter half of the Cretaceous, the continent of North America was divided into two sections, Laramidia in the west and Appalachia in the east. Unfortunately, this latter landmass recorded only a sparse fossil record of dinosaurs, obscuring those forms which must have occupied the eastern portion of North America during this time. Appalachian dinosaur faunas, though obscure, do seem to be different in composition from Laramidian ones. One particular element of Appalachian faunas that has attracted significant attention are the non-tyrannosaurid tyrannosauroids of the continent. Tyrannosauroids on Appalachia, though represented by at least two taxa (Appalachiosaurus montgomeriensis and Dryptosaurus aquilunguis), as well as many partial and fragmentary skeletons and elements, are nevertheless poorly know when compared to their western contemporaries. Here, one specimen, the partial metatarsus of a tyrannosauroid from the Campanian Merchantville Formation of New Jersey, is described in detail. The specimen may be differentiated from Appalachiosaurus montgomeriensis, Dryptosaurus aquilunguis, and an unnamed specimen from the Maastrichtian of New Jersey by several notable morphological features outside the spectrum of individual variation, as well as by factoring in biogeographical considerations. The new specimen thus has significance for representing a new morphotype of tyrannosauroid from Appalachia, suggesting greater diversity of the clade on the landmass. Because of this, tyrannosaur diversity in the Campanian of Appalachia was compared to the diversity of tyrannosaurs in Laramidia during the same period to analyze the similarities and differences between the biogeography of tyrannosaurs on each landmass. The results suggest that Appalachian non-tyrannosaurid tyrannosauroids experienced a similar amount of diversity to tyrannosaurids in Laramidia during the Campanian.

scholarly journals A Tyrannosauroid Metatarsus from the Merchantville Formation of New Jersey increases the diversity of non-Tyrannosaurid Tyrannosauroids on Appalachia

2017 ◽  
Author(s):  
Chase D Brownstein
Keyword(s):  
New Jersey ◽  
North America ◽  
Individual Variation ◽  
Fossil Record ◽  
Morphological Features ◽  
Similar Amount ◽  
The West ◽  
Similarities And Differences ◽  
Significant Attention

For almost the entirely of the latter half of the Cretaceous, the continent of North America was divided into two sections, Laramidia in the west and Appalachia in the east. Unfortunately, this latter landmass recorded only a sparse fossil record of dinosaurs, obscuring those forms which must have occupied the eastern portion of North America during this time. Appalachian dinosaur faunas, though obscure, do seem to be different in composition from Laramidian ones. One particular element of Appalachian faunas that has attracted significant attention are the non-tyrannosaurid tyrannosauroids of the continent. Tyrannosauroids on Appalachia, though represented by at least two taxa (Appalachiosaurus montgomeriensis and Dryptosaurus aquilunguis), as well as many partial and fragmentary skeletons and elements, are nevertheless poorly know when compared to their western contemporaries. Here, one specimen, the partial metatarsus of a tyrannosauroid from the Campanian Merchantville Formation of New Jersey, is described in detail. The specimen may be differentiated from Appalachiosaurus montgomeriensis, Dryptosaurus aquilunguis, and an unnamed specimen from the Maastrichtian of New Jersey by several notable morphological features outside the spectrum of individual variation, as well as by factoring in biogeographical considerations. The new specimen thus has significance for representing a new morphotype of tyrannosauroid from Appalachia, suggesting greater diversity of the clade on the landmass. Because of this, tyrannosaur diversity in the Campanian of Appalachia was compared to the diversity of tyrannosaurs in Laramidia during the same period to analyze the similarities and differences between the biogeography of tyrannosaurs on each landmass. The results suggest that Appalachian non-tyrannosaurid tyrannosauroids experienced a similar amount of diversity to tyrannosaurids in Laramidia during the Campanian.

scholarly journals A remarkable short-snouted horned dinosaur from the Late Cretaceous (late Campanian) of southern Laramidia

2013 ◽  
Vol 280 (1766) ◽  
pp. 20131186 ◽  
Author(s):  
Scott D. Sampson ◽  
Eric K. Lund ◽  
Mark A. Loewen ◽  
Andrew A. Farke ◽  
Katherine E. Clayton
Keyword(s):  
Phylogenetic Analysis ◽  
North America ◽  
Late Cretaceous ◽  
Fossil Record ◽  
Strong Support ◽  
Northern Region ◽  
New Taxon ◽  
Western North America ◽  
Postcranial Skeleton ◽  
Western Interior Seaway

The fossil record of centrosaurine ceratopsids is largely restricted to the northern region of western North America (Alberta, Montana and Alaska). Exceptions consist of single taxa from Utah ( Diabloceratops ) and China ( Sinoceratops ), plus otherwise fragmentary remains from the southern Western Interior of North America. Here, we describe a remarkable new taxon, Nasutoceratops titusi n. gen. et sp., from the late Campanian Kaiparowits Formation of Utah, represented by multiple specimens, including a nearly complete skull and partial postcranial skeleton. Autapomorphies include an enlarged narial region, pneumatic nasal ornamentation, abbreviated snout and elongate, rostrolaterally directed supraorbital horncores. The subrectangular parietosquamosal frill is relatively unadorned and broadest in the mid-region. A phylogenetic analysis indicates that Nasutoceratops is the sister taxon to Avaceratops , and that a previously unknown subclade of centrosaurines branched off early in the group's history and persisted for several million years during the late Campanian. As the first well-represented southern centrosaurine comparable in age to the bulk of northern forms, Nasutoceratops provides strong support for the provincialism hypothesis, which posits that Laramidia—the western landmass formed by inundation of the central region of North America by the Western Interior Seaway—hosted at least two coeval dinosaur communities for over a million years of late Campanian time.

scholarly journals A small azhdarchoid pterosaur from the latest Cretaceous, the age of flying giants

2016 ◽  
Vol 3 (8) ◽  
pp. 160333 ◽  
Author(s):  
Elizabeth Martin-Silverstone ◽  
Mark P. Witton ◽  
Victoria M. Arbour ◽  
Philip J. Currie
Keyword(s):  
North America ◽  
Late Cretaceous ◽  
Fossil Record ◽  
Upper Cretaceous ◽  
Large Species ◽  
Time Of Death ◽  
The West ◽  
New Material ◽  
The Individual ◽  
Continental Interior

Pterosaur fossils from the Campanian–Maastrichtian of North America have been reported from the continental interior, but few have been described from the west coast. The first pterosaur from the Campanian Northumberland Formation (Nanaimo Group) of Hornby Island, British Columbia, is represented here by a humerus, dorsal vertebrae (including three fused notarial vertebrae), and other fragments. The elements have features typical of Azhdarchoidea, an identification consistent with dominance of this group in the latest Cretaceous. The new material is significant for its size and ontogenetic stage: the humerus and vertebrae indicate a wingspan of ca 1.5 m, but histological sections and bone fusions indicate the individual was approaching maturity at time of death. Pterosaurs of this size are exceedingly rare in Upper Cretaceous strata, a phenomenon commonly attributed to smaller pterosaurs becoming extinct in the Late Cretaceous as part of a reduction in pterosaur diversity and disparity. The absence of small juveniles of large species—which must have existed—in the fossil record is evidence of a preservational bias against small pterosaurs in the Late Cretaceous, and caution should be applied to any interpretation of latest Cretaceous pterosaur diversity and success.

scholarly journals Prootic anatomy of a juvenile tyrannosauroid from New Jersey and its implications for the morphology and evolution of the tyrannosauroid braincase

2018 ◽  
Author(s):  
Chase D Brownstein
Keyword(s):  
Phylogenetic Analysis ◽  
North America ◽  
Northern Hemisphere ◽  
Late Cretaceous ◽  
Coastal Plain ◽  
Fossil Record ◽  
Atlantic Coastal Plain ◽  
Western Interior Seaway ◽  
Large Predator ◽  
Atlantic Coastal

Among the most recognizable theropods are the tyrannosauroids, a group of small to large carnivorous coelurosaurian dinosaurs that inhabited the majority of the northern hemisphere during the Cretaceous and came to dominate large predator niches in North American and Asian ecosystems by the end of the Mesozoic era. The clade is among the best-represented of dinosaur groups in the notoriously sparse fossil record of Appalachia, the Late Cretaceous landmass that occupied the eastern portion of North America after its formation from the transgression of the Western Interior Seaway. Here, the prootic of a juvenile tyrannosauroid collected from the middle-late Campanian Marshalltown Formation of the Atlantic Coastal Plain is described, remarkable for being the first concrete evidence of juvenile theropods in that plain during the time of the existence of Appalachia and the only portion of theropod braincase known from the landmass. Phylogenetic analysis recovers the specimen as an “intermediate” tyrannosauroid of similar grade to Dryptosaurus and Appalachiosaurus. Comparisons with the corresponding portions of other tyrannosauroid braincases suggest that the Ellisdale prootic is more similar to Turonian forms in morphology than to the derived tyrannosaurids of the Late Cretaceous, thus supporting the hypothesis that Appalachian tyrannosauroids and other vertebrates were relict forms surviving in isolation from their derived counterparts in Eurasia.

scholarly journals Unusual lizard fossil from the Miocene of Nebraska and a minimum age for cnemidophorine teiids

2020 ◽  
Vol 7 (8) ◽  
pp. 200317 ◽  
Author(s):  
Simon G. Scarpetta
Keyword(s):  
North America ◽  
Fossil Record ◽  
Fission Track ◽  
Divergence Time ◽  
Morphological Features ◽  
New Taxon ◽  
Fossil Material ◽  
Minimum Age ◽  
North And South America ◽  
North And South

Teiid lizards are well represented in the fossil record and are common components of modern ecosystems in North and South America. Many fossils were referred to the cnemidophorine teiid group (whiptails, racerunners and relatives), particularly from North America. However, systematic interpretations of morphological features in cnemidophorines were hampered by the historically problematic taxonomy of the clade, and the biogeography and chronology of cnemidophorine evolution in North America is poorly understood from the fossil record. Few fossil cnemidophorines were identified with an apomorphy-based diagnosis, and there are almost no fossil cnemidophorines that could be used to anchor node calibrations. Here, I describe a cnemidophorine from the Miocene Ogallala Group of Nebraska and diagnose the fossil using apomorphies. In that process, I clarify the systematic utility of several morphological features of cnemidophorine lizards. I refer the fossil to the least inclusive clade containing Aspidoscelis , Holcosus and Pholidoscelis . The most conservative minimum age of the locality of the fossil is a fission-track date of 6.3 Ma, but mammal biochronology provides a more refined age of 9.4 Ma, which can be used as a minimum age for the crown cnemidophorine clade in divergence time analyses. The fossil indicates that a cnemidophorine lineage that does not live in Nebraska today inhabited the area during the Miocene. I refrain from naming a new taxon pending discovery of additional fossil material of the lineage to which the fossil belonged.

scholarly journals A new Late Cretaceous iguanomorph from North America and the origin of New World Pleurodonta (Squamata, Iguania)

2017 ◽  
Vol 284 (1847) ◽  
pp. 20161902 ◽  
Author(s):  
David G. DeMar ◽  
Jack L. Conrad ◽  
Jason J. Head ◽  
David J. Varricchio ◽  
Gregory P. Wilson
Keyword(s):  
North America ◽  
Late Cretaceous ◽  
Fossil Record ◽  
New World ◽  
Cladistic Analysis ◽  
Arid Environment ◽  
New Taxon ◽  
Low Latitude ◽  
Anatomical Features ◽  
Parietal Foramen

Iguanomorpha (stem + crown Iguania) is a diverse squamate clade with members that predominate many modern American lizard ecosystems. However, the temporal and palaeobiogeographic origins of its constituent crown clades (e.g. Pleurodonta (basilisks, iguanas, and their relatives)) are poorly constrained, mainly due to a meagre Mesozoic-age fossil record. Here, we report on two nearly complete skeletons from the Late Cretaceous (Campanian) of North America that represent a new and relatively large-bodied and possibly herbivorous iguanomorph that inhabited a semi-arid environment. The new taxon exhibits a mosaic of anatomical features traditionally used in diagnosing Iguania and non-iguanian squamates (i.e. Scleroglossa; e.g. parietal foramen at the frontoparietal suture, astragalocalcaneal notch in the tibia, respectively). Our cladistic analysis of Squamata revealed a phylogenetic link between Campanian-age North American and East Asian stem iguanomorphs (i.e. the new taxon + Temujiniidae). These results and our evaluation of the squamate fossil record suggest that crown pleurodontans were restricted to the low-latitude Neotropics prior to their early Palaeogene first appearances in the mid-latitudes of North America.

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