Here we describe a new hesperornithiform specimen from the Upper Cretaceous Kanguk Formation of D... more Here we describe a new hesperornithiform specimen from the Upper Cretaceous Kanguk Formation of Devon Island, Nunavut, Canada. This specimen (NUVF 286) is referred to cf. Hesperornis sp. based on size and shape of femora and teeth preserved with other skeletal elements. Previous osteohistologic analyses indicate a subadult ontogenetic stage at the time of death. This new cf. Hesperornis specimen includes the first teeth associated with a high-latitude hesperornithiform, allowing for comments on the trophic behavior of these birds. Paleoecological reconstructions based on current knowledge of polar assemblages and comparisons to modern birds suggest that high-latitude hesperornithiform birds may have had more varied diets than previously assumed.
Large plant-eating dinosaurs are usually presumed to have been strictly herbivorous, because thei... more Large plant-eating dinosaurs are usually presumed to have been strictly herbivorous, because their derived teeth and jaws were capable of processing fibrous plant foods. This inferred feeding behavior offers a generalized view of dinosaur food habits, but rare direct fossil evidence of diet provides more nuanced insights into feeding behavior. Here we describe fossilized feces (coprolites) that demonstrate recurring consumption of crustaceans and rotted wood by large Late Cretaceous dinosaurs. These multiliter coprolites from the Kaiparowits Formation are primarily composed of comminuted conifer wood tissues that were fungally degraded before ingestion. Thick fragments of laminar crustacean cuticle are scattered within the coprolite contents and suggest that the dinosaurian defecators consumed sizeable crustaceans that sheltered in rotting logs. The diet of decayed wood and crustaceans offered a substantial supply of plant polysaccharides, with added dividends of animal protein and calcium. Nevertheless, it is unlikely that the fossilized fecal residues depict year-round feeding habits. It is more reasonable to infer that these coprolites reflected seasonal dietary shifts-possibly related to the dinosaurs' oviparous breeding activities. This surprising fossil evidence challenges conventional notions of herbivorous dinosaur diets and reveals a degree of dietary flexibility that is consistent with that of extant herbivorous birds.
A new Cretaceous ootaxon (eggshell type) from the Kaiparowits Formation of Grand Staircase-Escala... more A new Cretaceous ootaxon (eggshell type) from the Kaiparowits Formation of Grand Staircase-Escalante National Monument is among a growing number of very small eggs described from the Mesozoic. Analyses of two partial eggs (~ 17.7 mm in diameter) and 29 eggshell fragments reveal that this new ootaxon exhibits nodose ornamentation with distinctive branching pore canals that open atop the nodes. Its two-layered microstructure consists of a mammillary layer and a continuous layer with rugged grain boundaries between calcite grains. Although the exact identity of the egg producer is unknown, the eggshell microstructure and small size is consistent with a small-bodied avian or non-avian theropod. The specific combination of small egg size, branching pores, two-layered microstructure, and dispersituberculate ornamentation preserved in this new ootaxon is unique among theropod eggs. This underscores that both eggshell and skeletal fossils of Cretaceous theropods can display a mosaic of tran...
Tiny sinuous trace fossils have been found within probable gut contents of an exceptionally prese... more Tiny sinuous trace fossils have been found within probable gut contents of an exceptionally preserved specimen of a hadrosaurid dinosaur,Brachylophosaurus canadensis, from the Judith River Formation of Montana. Approximately 280 examples of the trace fossils were observed in 19 samples of gut region material. The tubular structures typically are about 0.3 mm across. Many have thin calcareous linings or layers, and some exhibit fine surficial striae. At least two dozen of these trace fossils share walls with adjacent tubular traces, and this association can extend for several millimeters. While the trace fossils share some characteristics with fine rhizoliths, these features are most consistent with tiny burrows, or possibly body impressions, of worms (vermiform organisms) of uncertain biologic affinity. Such trace fossils have not been reported previously, and herein described asParvitubulites striatusn. gen. n. sp. Either autochthonous (parasites) or allochthonous (scavengers) worm...
Multiple associations of fossil snails with dinosaur coprolites demonstrate that snails and dinos... more Multiple associations of fossil snails with dinosaur coprolites demonstrate that snails and dinosaurs not only shared ancient habitats but were trophically linked via dinosaur dung. Over 130 fossil snails representing at least seven different taxa have been found on or within herbivorous dinosaur coprolites from the Upper Cretaceous Two Medicine Formation of Montana. The terrestrial snail Megomphix is the most common taxon, but three other terrestrial taxa (Prograngerella, Hendersonia and Polygyrella) and three aquatic snails (Lioplacodes, ?Viviparus and a physid) also occur in coprolites. At least 46% of the shells in the faeces are whole or nearly so, indicating that most (if not all) of the snails were not ingested by dinosaurs, but were post-depositional visitors to the dung pats. The sizeable, moist and microbially enriched dinosaur faeces would have provided both food and roosting sites for the ancient snails, and the large number of snail–coprolite associations reflect recurring, opportunistic exploitation of dung.The terrestrial taxa in the coprolites suggest that this Late Cretaceous locality included sufficiently moist detrital or vegetative cover for snails when dinosaur dung was not present. The aquatic snails probably entered the faeces during flood events. Dinosaur dung would have provided an abundant but patchy influx of resources that was probably seasonally available in the ancient environment.
The broad biogeographic distribution of Hesperornis fossils in Late Cretaceous Western Interior S... more The broad biogeographic distribution of Hesperornis fossils in Late Cretaceous Western Interior Seaway deposits has prompted questions about whether they endured polar winters or migrated between mid- and high latitudes. Here, we compare microstructures of hesperornithiform long bones from Kansas and the Arctic to investigate whether migration or Late Cretaceous polar climate affected bone growth. We also examine modern penguin bones to determine how migration and climate may influence bone growth in birds with known behaviours. Histological analysis of hesperornithiform samples reveals continuous bone deposition throughout the cortex, plus an outer circumferential layer in adults. No cyclic growth marks, zonation or differences in vasculature are apparent in the Hesperornis specimens. Comparatively, migratory Adélie and chinstrap penguin bones show no zonation or changes in microstructure, suggesting that migration is not necessarily recorded in avian bone microstructure. Non-migratory gentoos show evidence of rapid bone growth possibly associated with increased chick growth rates in high-latitude populations and large body size. The absence of histological evidence for migration in extinct Hesperornis and extant pygoscelid penguins may reflect that these birds reached skeletal maturity before migration or overwintering. This underscores the challenges of using bone microstructure to infer the effects of behaviour and climate on avian growth.
Over 20 specimens of the new genus and species Nunavutospongia irregulara, an irregular stump-lik... more Over 20 specimens of the new genus and species Nunavutospongia irregulara, an irregular stump-like to columnar, or fan- to blade-shaped, hexactinosid hexactinellid sponge, have been recovered from exposures of the Upper Cretaceous upper Kanguk Formation on Devon Island, Nunavut Territory, in the Canadian High Arctic. The species and genus are characterized by dermal surfaces with prominent radial, irregularly vertical, rib-like flanges that have a single linear series of separated oscula perforating their rounded crests. The thin, but persistent dermal layer of fused hexactine-based spicules has rays thicker than those of the similarly fused endosomal, quadrangularly arranged, hexactines of the principal skeleton. Ostia of coarse exhalant canals, and finer inhalant canals, are extensively and uniformly developed, but irregularly placed, in the dermal layer. A thin, less prominent, gastral layer of thickened spicules lines the short, internally tapered spongocoel openings. The skeleton exposed in the commonly upward-arcuate base of each sponge has a radiate structure that does not have significant ostia. The new genus is tentatively included in the Family Cribrospongiidae Roemer, 1864, within the Order Hexactinosa Schrammen, 1903. The specimens were found in unconsolidated fine-grained glauconitic sediments along with other fossils such as fish teeth, bird bones, lingulids, coprolites, and wood. The sedimentology, stratigraphic context, and co-occurrence with fossil wood suggest that these sponges inhabited the neritic zone. As such, they would have been subject to polar light regimes, because paleogeographic reconstructions indicate that Devon Island was above the Arctic Circle during the Late Cretaceous. The distribution of the specimens suggests that they were solitary sponges that used their arcuate bases to colonize sandy substrates or biotic debris.
The widespread mass extinctions at the end of the Cretaceous caused world-wide disruption of ecos... more The widespread mass extinctions at the end of the Cretaceous caused world-wide disruption of ecosystems, and faunal responses to the one-two punch of severe environmental perturbation and ecosystem collapse are still unclear. Here we report the discovery of in situ terrestrial fossil burrows from just above the impact-defined Cretaceous-Paleogene (K/Pg) boundary in southwestern North Dakota. The crisscrossing networks of horizontal burrows occur at the interface of a lignitic coal and silty sandstone, and reveal intense faunal activity within centimeters of the boundary clay. Estimated rates of sedimentation and coal formation suggest that the burrows were made less than ten thousand years after the end-Cretaceous impact. The burrow characteristics are most consistent with burrows of extant earthworms. Moreover, the burrowing and detritivorous habits of these annelids fit models that predict the trophic and sheltering lifestyles of terrestrial animals that survived the K/Pg extinction event. In turn, such detritus-eaters would have played a critical role in supporting secondary consumers. Thus, some of the carnivorous vertebrates that radiated after the K/Pg extinction may owe their evolutionary success to thriving populations of earthworms.
An exceptionally preserved subadult specimen (JRF 115H) of a hadrosaurid, Brachylophosaurus canad... more An exceptionally preserved subadult specimen (JRF 115H) of a hadrosaurid, Brachylophosaurus canadensis, from the Judith River Formation near Malta, Montana, contains abundant plant fragments concentrated within the body cavity. We examined the taphonomy of the carcass and analyzed the gut-region material to test whether the organic remains represent fossilized gut contents. The dinosaur was buried in a fluvial channel setting, and the excellent articulation, integument impressions, and lack of scavenging indicate rapid burial. The organic material occupies a volume of at least 5750 cm3, and comparable material is not found outside the carcass. The carcass contents include 63% clay, 16% undetermined matrix, 12% organic matter, and 9% larger inorganic clasts—mostly 50–100 um quartz grains. Most of the organics appear to be mm-scale leaf fragments. The most parsimonious explanation for the presence and composition of the gut-region material is that much of the plant fossils represent reworked brachylophosaur ingesta influenced by flowing water that entered through openings in the carcass and introduced clay. The evidence strongly suggests that the hadrosaurid ate significant quantities of leaves and processed them into small pieces. This study provides baseline information for analyzing other cases of putative gut contents in herbivorous dinosaurs.
METHODS The chapters included in the first part of the volume review a variety of methods that ca... more METHODS The chapters included in the first part of the volume review a variety of methods that can be applied to study the fossil record of prédation. Various direct and indirect indicators of prédation are available to paleontologists, including trace fossils, coprolites, gut contents, exceptional preservational events, taphonomic patterns, and indirect evidence provided by functional morphology and phylogenetic affinities (Kowalewski). Because of the highly disparate nature of the data itself, variable research goals, and even personal ...
Here we describe a new hesperornithiform specimen from the Upper Cretaceous Kanguk Formation of D... more Here we describe a new hesperornithiform specimen from the Upper Cretaceous Kanguk Formation of Devon Island, Nunavut, Canada. This specimen (NUVF 286) is referred to cf. Hesperornis sp. based on size and shape of femora and teeth preserved with other skeletal elements. Previous osteohistologic analyses indicate a subadult ontogenetic stage at the time of death. This new cf. Hesperornis specimen includes the first teeth associated with a high-latitude hesperornithiform, allowing for comments on the trophic behavior of these birds. Paleoecological reconstructions based on current knowledge of polar assemblages and comparisons to modern birds suggest that high-latitude hesperornithiform birds may have had more varied diets than previously assumed.
Large plant-eating dinosaurs are usually presumed to have been strictly herbivorous, because thei... more Large plant-eating dinosaurs are usually presumed to have been strictly herbivorous, because their derived teeth and jaws were capable of processing fibrous plant foods. This inferred feeding behavior offers a generalized view of dinosaur food habits, but rare direct fossil evidence of diet provides more nuanced insights into feeding behavior. Here we describe fossilized feces (coprolites) that demonstrate recurring consumption of crustaceans and rotted wood by large Late Cretaceous dinosaurs. These multiliter coprolites from the Kaiparowits Formation are primarily composed of comminuted conifer wood tissues that were fungally degraded before ingestion. Thick fragments of laminar crustacean cuticle are scattered within the coprolite contents and suggest that the dinosaurian defecators consumed sizeable crustaceans that sheltered in rotting logs. The diet of decayed wood and crustaceans offered a substantial supply of plant polysaccharides, with added dividends of animal protein and calcium. Nevertheless, it is unlikely that the fossilized fecal residues depict year-round feeding habits. It is more reasonable to infer that these coprolites reflected seasonal dietary shifts-possibly related to the dinosaurs' oviparous breeding activities. This surprising fossil evidence challenges conventional notions of herbivorous dinosaur diets and reveals a degree of dietary flexibility that is consistent with that of extant herbivorous birds.
A new Cretaceous ootaxon (eggshell type) from the Kaiparowits Formation of Grand Staircase-Escala... more A new Cretaceous ootaxon (eggshell type) from the Kaiparowits Formation of Grand Staircase-Escalante National Monument is among a growing number of very small eggs described from the Mesozoic. Analyses of two partial eggs (~ 17.7 mm in diameter) and 29 eggshell fragments reveal that this new ootaxon exhibits nodose ornamentation with distinctive branching pore canals that open atop the nodes. Its two-layered microstructure consists of a mammillary layer and a continuous layer with rugged grain boundaries between calcite grains. Although the exact identity of the egg producer is unknown, the eggshell microstructure and small size is consistent with a small-bodied avian or non-avian theropod. The specific combination of small egg size, branching pores, two-layered microstructure, and dispersituberculate ornamentation preserved in this new ootaxon is unique among theropod eggs. This underscores that both eggshell and skeletal fossils of Cretaceous theropods can display a mosaic of tran...
Tiny sinuous trace fossils have been found within probable gut contents of an exceptionally prese... more Tiny sinuous trace fossils have been found within probable gut contents of an exceptionally preserved specimen of a hadrosaurid dinosaur,Brachylophosaurus canadensis, from the Judith River Formation of Montana. Approximately 280 examples of the trace fossils were observed in 19 samples of gut region material. The tubular structures typically are about 0.3 mm across. Many have thin calcareous linings or layers, and some exhibit fine surficial striae. At least two dozen of these trace fossils share walls with adjacent tubular traces, and this association can extend for several millimeters. While the trace fossils share some characteristics with fine rhizoliths, these features are most consistent with tiny burrows, or possibly body impressions, of worms (vermiform organisms) of uncertain biologic affinity. Such trace fossils have not been reported previously, and herein described asParvitubulites striatusn. gen. n. sp. Either autochthonous (parasites) or allochthonous (scavengers) worm...
Multiple associations of fossil snails with dinosaur coprolites demonstrate that snails and dinos... more Multiple associations of fossil snails with dinosaur coprolites demonstrate that snails and dinosaurs not only shared ancient habitats but were trophically linked via dinosaur dung. Over 130 fossil snails representing at least seven different taxa have been found on or within herbivorous dinosaur coprolites from the Upper Cretaceous Two Medicine Formation of Montana. The terrestrial snail Megomphix is the most common taxon, but three other terrestrial taxa (Prograngerella, Hendersonia and Polygyrella) and three aquatic snails (Lioplacodes, ?Viviparus and a physid) also occur in coprolites. At least 46% of the shells in the faeces are whole or nearly so, indicating that most (if not all) of the snails were not ingested by dinosaurs, but were post-depositional visitors to the dung pats. The sizeable, moist and microbially enriched dinosaur faeces would have provided both food and roosting sites for the ancient snails, and the large number of snail–coprolite associations reflect recurring, opportunistic exploitation of dung.The terrestrial taxa in the coprolites suggest that this Late Cretaceous locality included sufficiently moist detrital or vegetative cover for snails when dinosaur dung was not present. The aquatic snails probably entered the faeces during flood events. Dinosaur dung would have provided an abundant but patchy influx of resources that was probably seasonally available in the ancient environment.
The broad biogeographic distribution of Hesperornis fossils in Late Cretaceous Western Interior S... more The broad biogeographic distribution of Hesperornis fossils in Late Cretaceous Western Interior Seaway deposits has prompted questions about whether they endured polar winters or migrated between mid- and high latitudes. Here, we compare microstructures of hesperornithiform long bones from Kansas and the Arctic to investigate whether migration or Late Cretaceous polar climate affected bone growth. We also examine modern penguin bones to determine how migration and climate may influence bone growth in birds with known behaviours. Histological analysis of hesperornithiform samples reveals continuous bone deposition throughout the cortex, plus an outer circumferential layer in adults. No cyclic growth marks, zonation or differences in vasculature are apparent in the Hesperornis specimens. Comparatively, migratory Adélie and chinstrap penguin bones show no zonation or changes in microstructure, suggesting that migration is not necessarily recorded in avian bone microstructure. Non-migratory gentoos show evidence of rapid bone growth possibly associated with increased chick growth rates in high-latitude populations and large body size. The absence of histological evidence for migration in extinct Hesperornis and extant pygoscelid penguins may reflect that these birds reached skeletal maturity before migration or overwintering. This underscores the challenges of using bone microstructure to infer the effects of behaviour and climate on avian growth.
Over 20 specimens of the new genus and species Nunavutospongia irregulara, an irregular stump-lik... more Over 20 specimens of the new genus and species Nunavutospongia irregulara, an irregular stump-like to columnar, or fan- to blade-shaped, hexactinosid hexactinellid sponge, have been recovered from exposures of the Upper Cretaceous upper Kanguk Formation on Devon Island, Nunavut Territory, in the Canadian High Arctic. The species and genus are characterized by dermal surfaces with prominent radial, irregularly vertical, rib-like flanges that have a single linear series of separated oscula perforating their rounded crests. The thin, but persistent dermal layer of fused hexactine-based spicules has rays thicker than those of the similarly fused endosomal, quadrangularly arranged, hexactines of the principal skeleton. Ostia of coarse exhalant canals, and finer inhalant canals, are extensively and uniformly developed, but irregularly placed, in the dermal layer. A thin, less prominent, gastral layer of thickened spicules lines the short, internally tapered spongocoel openings. The skeleton exposed in the commonly upward-arcuate base of each sponge has a radiate structure that does not have significant ostia. The new genus is tentatively included in the Family Cribrospongiidae Roemer, 1864, within the Order Hexactinosa Schrammen, 1903. The specimens were found in unconsolidated fine-grained glauconitic sediments along with other fossils such as fish teeth, bird bones, lingulids, coprolites, and wood. The sedimentology, stratigraphic context, and co-occurrence with fossil wood suggest that these sponges inhabited the neritic zone. As such, they would have been subject to polar light regimes, because paleogeographic reconstructions indicate that Devon Island was above the Arctic Circle during the Late Cretaceous. The distribution of the specimens suggests that they were solitary sponges that used their arcuate bases to colonize sandy substrates or biotic debris.
The widespread mass extinctions at the end of the Cretaceous caused world-wide disruption of ecos... more The widespread mass extinctions at the end of the Cretaceous caused world-wide disruption of ecosystems, and faunal responses to the one-two punch of severe environmental perturbation and ecosystem collapse are still unclear. Here we report the discovery of in situ terrestrial fossil burrows from just above the impact-defined Cretaceous-Paleogene (K/Pg) boundary in southwestern North Dakota. The crisscrossing networks of horizontal burrows occur at the interface of a lignitic coal and silty sandstone, and reveal intense faunal activity within centimeters of the boundary clay. Estimated rates of sedimentation and coal formation suggest that the burrows were made less than ten thousand years after the end-Cretaceous impact. The burrow characteristics are most consistent with burrows of extant earthworms. Moreover, the burrowing and detritivorous habits of these annelids fit models that predict the trophic and sheltering lifestyles of terrestrial animals that survived the K/Pg extinction event. In turn, such detritus-eaters would have played a critical role in supporting secondary consumers. Thus, some of the carnivorous vertebrates that radiated after the K/Pg extinction may owe their evolutionary success to thriving populations of earthworms.
An exceptionally preserved subadult specimen (JRF 115H) of a hadrosaurid, Brachylophosaurus canad... more An exceptionally preserved subadult specimen (JRF 115H) of a hadrosaurid, Brachylophosaurus canadensis, from the Judith River Formation near Malta, Montana, contains abundant plant fragments concentrated within the body cavity. We examined the taphonomy of the carcass and analyzed the gut-region material to test whether the organic remains represent fossilized gut contents. The dinosaur was buried in a fluvial channel setting, and the excellent articulation, integument impressions, and lack of scavenging indicate rapid burial. The organic material occupies a volume of at least 5750 cm3, and comparable material is not found outside the carcass. The carcass contents include 63% clay, 16% undetermined matrix, 12% organic matter, and 9% larger inorganic clasts—mostly 50–100 um quartz grains. Most of the organics appear to be mm-scale leaf fragments. The most parsimonious explanation for the presence and composition of the gut-region material is that much of the plant fossils represent reworked brachylophosaur ingesta influenced by flowing water that entered through openings in the carcass and introduced clay. The evidence strongly suggests that the hadrosaurid ate significant quantities of leaves and processed them into small pieces. This study provides baseline information for analyzing other cases of putative gut contents in herbivorous dinosaurs.
METHODS The chapters included in the first part of the volume review a variety of methods that ca... more METHODS The chapters included in the first part of the volume review a variety of methods that can be applied to study the fossil record of prédation. Various direct and indirect indicators of prédation are available to paleontologists, including trace fossils, coprolites, gut contents, exceptional preservational events, taphonomic patterns, and indirect evidence provided by functional morphology and phylogenetic affinities (Kowalewski). Because of the highly disparate nature of the data itself, variable research goals, and even personal ...
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