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opennotspecifiedDec 2002View details →

Figure 3 in Late Cretaceous dinosaurs from the Denver Basin, Colorado

Figure 3, facing page, right panel. Another holotype by Cope (1874a) from Bijou Creek is Polyonax mortuarius (AMNH 1568). A, dorsal centrum; B, bone fragment; C, fibula (misidentified as a horn by Hatcher, 1907); and D-I, bone fragments. Compare with Cope (1875) pl. 2 figs. 3-5, pl. 3 figs. 1-4. Scale in cm.

opennotspecifiedDec 2002View details →

Figure 2 in Late Cretaceous dinosaurs from the Denver Basin, Colorado

Figure 2, facing page, left panel. Some of first dinosaur specimens to be described from Denver Basin include these of holotype of Cionodon arctatus (AMNH 3951), described by Cope (1874a). Specimens were collected along Bijou Creek. A and B, proximal ends of metatarsals; C, distal end of metatarsal III; andD, E, F, maxillary fragments. Compare with Cope (1875) pl. 1, pl. 2 figs. 1-4. Scale in cm.

opennotspecifiedDec 2002View details →

Figure 5 in Late Cretaceous dinosaurs from the Denver Basin, Colorado

Figure 5. Famous "Bison" alticornis horn cores from bluffs along South Platte River, opposite confluence with Cherry Creek in lateral (A) and anterior (B) views. Had Marsh attempted to reconstruct the horns as bison, the skull would have looked as in C.

opencc-by-4.0Feb 2020View details →

Laramide orogenesis driven by Late Cretaceous weakening of the North American lithosphere

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Fig. 29 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 29. Daspletosaurus sp. (TMP 94.143.1). Left palatine (and part of pterygoid) in lateral (A), medial (B), anterior (C), and ventral (D) views.

Fig. 24 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 24. Daspletosaurus sp. (TMP 94.143.1). Left quadratojugal in lateral (A), medial (B), and posterior (C) views.

Fig. 27 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 27. Daspletosaurus sp. (TMP 94.143.1). Middle ear region of left side of braincase in ventrolateral view.

Fig. 18 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 18. Daspletosaurus sp. (TMP 94.143.1). Front of skull in lateral (A), dorsal (B) and anterior views.

Fig. 12 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 12. Albertosaurus sarcophagus (TMP 81.10.1). Left ectopterygoid in dorsal (A) and ventral (B) views.

Fig. 4 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 4. Gorgosaurus libratus (TMP 91.36.500). Dorsal view of back of left mandible showing articular and part of surangular.

Fig. 11 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 11. Albertosaurus sarcophagus (TMP 81.10.1). Right palatine in lateral (A) and medial (B) views.

Fig. 9 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 9. Albertosaurus sarcophagus (TMP 81.10.1). Left quadratojugal in lateral (A) and medial (B) views.

Fig. 14 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 14. Albertosaurus sarcophagus (TMP 81.10.1). Left surangular in lateral (A) and medial (B) views.

Fig. 21 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 21. Daspletosaurus sp. (TMP 94.143.1). Parietals in dorsal (A), left lateral (B), ventral (C), and posterior (D) aspects.

Fig. 7 in Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

Fig. 7. Albertosaurus sarcophagus (TMP 81.10.1). Specimen drawing of top of skull in dorsal (A), lateral (B), and ventral (C) views.

opencc-zeroSep 2020View details →

Data from: Aragonite bias exhibits systematic spatial variation in the late Cretaceous Western Interior Seaway, North America

Preferential dissolution of the biogenic carbonate polymorph aragonite promotes preservational bias in shelly marine faunas. Whilst field studies have documented the impact of preferential aragonite dissolution on fossil molluscan diversity, its impact on regional and global biodiversity metrics is debated. Epicontinental seas are especially prone to conditions which both promote and inhibit preferential dissolution, which may result in spatially extensive zones with variable preservation. Here we present a multi-faceted evaluation of aragonite dissolution within the late Cretaceous Western Interior Seaway of North America. Occurrence data of molluscs from two time intervals (Cenomanian-Turonian boundary, early Campanian) are plotted on new high-resolution paleogeographies to assess aragonite preservation within the seaway. Fossil occurrences, diversity estimates and sampling probabilities for calcitic and aragonitic fauna were compared in zones defined by depth and distance from the seaway margins. Apparent range sizes, which could be influenced by differential preservation potential of aragonite between separate localities, were also compared. Our results are consistent with exacerbated aragonite dissolution within specific depth zones for both time slices, with aragonitic bivalves additionally showing a statistically significant decrease in range size compared to calcitic fauna within carbonate-dominated Cenomanian-Turonian strata. However, we are unable to conclusively show that aragonite dissolution impacted diversity estimates. Therefore, whilst aragonite dissolution is likely to have affected the preservation of fauna in specific localities, time averaging and instantaneous preservation events preserve regional biodiversity. Our results suggest that the spatial expression of taphonomic biases should be an important consideration for paleontologists working on paleobiogeographic problems.

opencc-zeroAug 2019View details →

Data from: Polymorphism in Late Cretaceous phylloceratid ammonoids: evidence from ontogenetic trajectories of septal spacing

The ontogenetic trajectories of septal spacing between succeeding chambers of two phylloceratid ammonoids, Hypophylloceras subramosum and Phyllopachyceras ezoense, from the Haboro and Kotanbetsu areas, north‐western Hokkaido, Japan, were analysed. The ontogenetic trajectories of septal spacing of H. subramosum demonstrate a general trend with large intraspecific variation: two cycles of increasing to decreasing spacing followed by almost constant spacing. The large intraspecific variation can be subdivided into three types, making this species polymorphic. The ontogenetic trajectories of septal spacing of P. ezoense also show intraspecific variation, but with a different trend: one cycle of increasing to decreasing spacing and an increasing trend after that. The intraspecific variation can be subdivided into two types, which suggests that this species is dimorphic, possibly sexually dimorphic. Dimorphism is supported by two observations: (1) the difference in the ontogenetic trajectories of septal spacing is only seen in the later ontogenetic stages; and (2) the two types co‐occur with comparable abundance throughout all stratigraphic horizons. Detailed analyses of ontogenetic trajectories of septal spacing may reveal polymorphism in other ammonoid clades.

opencc-zeroDec 2015View details →

Data from: New record of Egertonia (Elopiformes, Phyllodontidae) from the Late Cretaceous of South India

We report a new occurrence of the phyllodontid teleost fish Egertonia from the Late Cretaceous Kallamedu Formation of the Cauvery Basin, South India. This is the oldest occurrence of Phyllodontidae in India, and only the second Cretaceous Gondwanan occurrence of this genus, following a toothplate previously described from the Late Cretaceous Maevarano Formation, Madagascar. The presence of phyllodontid fish supports a fluvial–deltaic or brackish environment for the lower part of the Kallamedu Formation, a rich deposit including typically Gondwanan taxa, such as simosuchid crocodiles, bothremydid turtles and abelisaurid dinosaurs, as well as an anomalous troodontid dinosaur. Egertonia adds another taxon of primarily Laurasian distribution to the Kallamedu fauna and further expands the list of taxa known from the Late Cretaceous of both India and Madagascar, strengthening the degree of faunal similarity between the two landmasses in the latest Cretaceous.

opencc-zeroDec 2011View details →

Data from: Different modes of migration among Late Cretaceous ammonoids in northwestern Hokkaido, Japan: evidence from the analyses of shell whorls

The thickness ratios of shell whorls (= whorl breadth / shell diameter) in the ammonoids Damesites sugata, Hypophylloceras subramosum, and Gaudryceras tenuiliratum from the Late Cretaceous outer shelf deposits in the Kotanbetsu area of northwestern Hokkaido, Japan, were examined in order to determine their mode of migration. The thickness ratios of D. sugata differ significantly with depth on the outer shelf environment, but show no significant difference laterally at a similar depth. These results suggest that D. sugata did not frequently migrate to different depths on the outer shelf environment, but tended to live and migrate laterally at a similar depth on the outer shelf. The thickness ratios of H. subramosum and G. tenuiliratum show no significant difference between different depths on the outer shelf environment nor for lateral direction at a similar depth. This suggests that H. subramosum and G. tenuiliratum frequently migrated at different depths on the out er shelf environment and laterally at a similar depth. There is no difference in hatchling diameters in all the examined species at different depths on the outer shelf environment, suggesting that the thickness ratios became manifest after the post-hatchling stage due to limited migration, which would have been in a nektobenthic habitat. The various modes of migration in the study area are reconstructed in this study, suggesting a diversified paleoecology of Late Cretaceous ammonoids.