Tracking the Initial Diversification of Asterids: Anatomically Preserved Cornalean Fruits from the Early Coniacian (Late Cretaceous) of Western North America

Abstract The timing of non-avian dinosaur decline is one of the most debated subjects in dinosaur palaeontology. Dinosaur faunas from the last few million years of the Mesozoic appear far less diverse than those from earlier in the Cretaceous, a trend that could suggest non-avian dinosaur extinction occurred gradually. However, the limited nature of the latest Cretaceous dinosaur record outside western North America has obscured patterns in dinosaur diversity just before the extinction. Here, I describe two associated skeletons and several isolated fossils recovered from the New Egypt Formation of New Jersey, a latest Maastrichtian unit that underlies the K–Pg boundary. The larger skeleton appears to be a small-bodied adult from a lineage outside Hadrosauridae, the dominant group of these animals during the Maastrichtian, that persisted along the eastern coast of North America. Smaller specimens are identifiable as juvenile hadrosauromorphs. These results substantiate an important assemblage of herbivorous dinosaurs from the poorly-known Cretaceous of eastern North America. The marine depositional setting for these skeletons demonstrates that proposed ecosystem preferences among hadrosauromorphs may be biased by post-mortem transportation, and the adult skeleton has implications for assessing the proposed relictual nature of Late Cretaceous eastern North American vertebrates.

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The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA)

10.7287/peerj.preprints.2746v2 ◽

2017 ◽

Cited By ~ 1

Author(s):

Andrew A. Farke ◽

George E. Phillips

Keyword(s):

North America ◽

Late Cretaceous ◽

Depositional Environment ◽

Upper Cretaceous ◽

Eastern North America ◽

Western North America ◽

Western Interior Seaway ◽

Double Root ◽

Union County ◽

Dentary Tooth

Ceratopsids (“horned dinosaurs”) are known from western North America and Asia, a distribution reflecting an inferred subaerial link between the two landmasses during the Late Cretaceous. However, this clade was previously unknown from eastern North America, presumably due to limited outcrop of the appropriate age and depositional environment as well as the separation of eastern and western North America by the Western Interior Seaway during much of the Late Cretaceous. A dentary tooth from the Owl Creek Formation (late Maastrichtian) of Union County, Mississippi, represents the first reported occurrence of Ceratopsidae from eastern North America. This tooth shows a combination of features typical of Ceratopsidae, including a double root and a prominent, blade-like carina. Based on the age of the fossil, we hypothesize that it is consistent with a dispersal of ceratopsids into eastern North America during the very latest Cretaceous, presumably after the two halves of North America were reunited following the retreat of the Western Interior Seaway.

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The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Late Cretaceous, Mississippi, USA)

10.7287/peerj.preprints.2746v1 ◽

2017 ◽

Author(s):

Andrew A. Farke ◽

George E. Phillips

Keyword(s):

North America ◽

Late Cretaceous ◽

Depositional Environment ◽

Eastern North America ◽

Western North America ◽

Western Interior Seaway ◽

Double Root ◽

Union County ◽

Dentary Tooth

Ceratopsids (“horned dinosaurs”) are known from numerous specimens in western North America and Asia, a distribution reflecting the inferred subaerial link between the two landmasses during the Late Cretaceous. However, this clade was previously unknown from eastern North America, presumably due to limited outcrop of the appropriate age and depositional environment as well as the separation of eastern and western North America by the Western Interior Seaway during much of the Late Cretaceous. A dentary tooth from the Owl Creek Formation (late Maastrichtian) of Union County, Mississippi, represents the first reported occurrence of Ceratopsidae from eastern North America. This tooth shows a combination of features typical of Ceratopsidae, including a double root and a prominent, blade-like carina. Based on the age of the fossil, we hypothesize that it is consistent with a dispersal of ceratopsids into eastern North America during the very latest Cretaceous, after the two halves of North America were reunited following the retreat of the Western Interior Seaway.

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The first reported ceratopsid dinosaur from eastern North America (Owl Creek Formation, Upper Cretaceous, Mississippi, USA)

PeerJ ◽

10.7717/peerj.3342 ◽

2017 ◽

Vol 5 ◽

pp. e3342 ◽

Cited By ~ 7

Author(s):

Andrew A. Farke ◽

George E. Phillips

Keyword(s):

North America ◽

Late Cretaceous ◽

Depositional Environment ◽

Upper Cretaceous ◽

Eastern North America ◽

Western North America ◽

Western Interior Seaway ◽

Double Root ◽

Union County ◽

Dentary Tooth

Ceratopsids (“horned dinosaurs”) are known from western North America and Asia, a distribution reflecting an inferred subaerial link between the two landmasses during the Late Cretaceous. However, this clade was previously unknown from eastern North America, presumably due to limited outcrop of the appropriate age and depositional environment as well as the separation of eastern and western North America by the Western Interior Seaway during much of the Late Cretaceous. A dentary tooth from the Owl Creek Formation (late Maastrichtian) of Union County, Mississippi, represents the first reported occurrence of Ceratopsidae from eastern North America. This tooth shows a combination of features typical of Ceratopsidae, including a double root and a prominent, blade-like carina. Based on the age of the fossil, we hypothesize that it is consistent with a dispersal of ceratopsids into eastern North America during the very latest Cretaceous, presumably after the two halves of North America were reunited following the retreat of the Western Interior Seaway.

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The Late Cretaceous paleomagnetic field in North America: a South American perspective

Canadian Journal of Earth Sciences ◽

10.1139/e11-051 ◽

2011 ◽

Vol 48 (11) ◽

pp. 1483-1488 ◽

Cited By ~ 11

Author(s):

Rubén Somoza

Keyword(s):

North America ◽

Rigid Body ◽

Late Cretaceous ◽

Paleomagnetic Data ◽

South American ◽

Western North America ◽

Reference Field ◽

American Perspective ◽

Paleomagnetic Pole

Determining the Late Cretaceous paleomagnetic pole for North America has been difficult because of the lack of suitable rocks of that age in cratonic areas to provide the necessary data. As an alternative, different studies have appealed to paleomagnetic data from rocks in western North America. Using paleopoles from stable areas in neighboring continents, it is suggested that the available Late Cretaceous paleomagnetic record in western North America should be analyzed in terms of rigid body deformations rather than be used to represent the cratonic reference field.

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