Introduction National park units have at times been referred to as “ecological islands.” More rec... more Introduction National park units have at times been referred to as “ecological islands.” More recently, such units have begun to be viewed as ecological mosaics rather than separate island units as managers of publicly owned, federally managed lands have increasingly gained an appreciation for park boundaries and their relationships to particular biological issues. It is often apparent to these managers that individual park boundaries may not fully encompass appropriate habitat areas for managing biological resources. As a result, partnerships have been sought within and between land management agencies to best accommodate the needs of these biological resources. In order to understand the natural world of today, one must examine the past. Studies such as those discussed below show that fossils are more than oddities of the rock record; they represent the record of life that has evolved on this planet. They are the means to test the scale and robustness of ecological principles obse...
<p>Ontogenetic stages of nasal boss development in <i>Pachyrhinosaurus</i> (Sta... more <p>Ontogenetic stages of nasal boss development in <i>Pachyrhinosaurus</i> (Stage 1 youngest), based upon descriptions and inferences of Currie et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065802#pone.0065802-Currie1" target="_blank">[4]</a>.</p
Faunal abundance and fossil size and shape data from microvertebrate localities in the Upper Cret... more Faunal abundance and fossil size and shape data from microvertebrate localities in the Upper Cretaceous Judith River Formation of south-central Montana illustrate that even when located in similar sedimentary facies, concentrations of vertebrate microfossils may exhibit strikingly different taphonomic profiles. Degrees of microfossil size and shape sorting may vary even among sites from the same sedimentary facies. In some instances, such variations may make it impossible to disregard taphonomic causes for differences sites exhibit in paleofaunal abundances. To limit the possibility that taphonomically generated faunal differences might be mistaken for true differences in paleoecology, comparisons of paleofaunal abundances should be restricted to microvertebrate sites both from similar sedimentary facies and with similar profiles of fossil sizes and shapes.
Faunal abundance and fossil size and shape data from microvertebrate localities in the Upper Cret... more Faunal abundance and fossil size and shape data from microvertebrate localities in the Upper Cretaceous Judith River Formation of south-central Montana illustrate that even when located in similar sedimentary facies, concentrations of vertebrate microfossils may exhibit strikingly different taphonomic profiles. Degrees of microfossil size and shape sorting may vary even among sites from the same sedimentary facies. In some instances, such variations may make it impossible to disregard taphonomic causes for differences sites exhibit in paleofaunal abundances. To limit the possibility that taphonomically generated faunal differences might be mistaken for true differences in paleoecology, comparisons of paleofaunal abundances should be restricted to microvertebrate sites both from similar sedimentary facies and with similar profiles of fossil sizes and shapes.
We report on the first record of a pterosaur from Alaska. This record consists of a single manus ... more We report on the first record of a pterosaur from Alaska. This record consists of a single manus track from the lower part of the Upper Cretaceous Cantwell Formation in Denali National Park, Alaska, United States, making this the northernmost occurrence for this group of reptiles. The specimen is from deposits that record a low-lying floodplain with small lakes and ponds, dissected by small channels that fed a larger tributary stream on an active fan lobe. The dominant vegetation was comprised of conifers with an understory of ferns and horsetails.
Mid-Cenozoic marine mammals of Alaska were isolated from the Arctic Ocean by Beringia and were th... more Mid-Cenozoic marine mammals of Alaska were isolated from the Arctic Ocean by Beringia and were thus part of a far North Pacific ecosystem. The amphicynodontid ?Kolponomos, a neocete whale, and a desmostylian were found in the latest Oligocene or earliest Miocene (approximately 23 Ma) Dutch Harbor Member of the Unalaska Formation, Aleutian Chain, Alaska. The Unalaska desmostylian is more derived than Cornwallius but more primitive than Desmostylus. Derived desmostylians are known from the early middle Miocene (16-15 Ma) Bear Lake Formation on the Alaska Peninsula and the Narrow Cape Formation on Kodiak Island. The Miocene Yakatat Formation has produced sparse mammal remains but records the onset of montane glaciation in southern Alaska.
FLAIG, Peter P. 1, HASIOTIS, ST 2, VAN DER KOLK, Dolores A. 1, and FIORILLO, Anthony 3,(1) Bureau... more FLAIG, Peter P. 1, HASIOTIS, ST 2, VAN DER KOLK, Dolores A. 1, and FIORILLO, Anthony 3,(1) Bureau of Economic Geology, University of Texas at Austin, Jackson School of Geosciences, 10100 Burnet Rd, Austin, TX 78758, peter. flaig@ beg. utexas. edu,(2) ...
Hadrosaurid fossils from the Liscomb Bonebed (Prince Creek Formation, North Slope, Alaska) were t... more Hadrosaurid fossils from the Liscomb Bonebed (Prince Creek Formation, North Slope, Alaska) were the first dinosaur bones discovered from the Arctic. While the Prince Creek Formation hadrosaurids were long identified as Edmontosaurus, a member of the sub-clade Hadrosaurinae, they were recently assigned to a newly-erected taxon, Ugrunaaluk kuukpikensis. However, taxonomic status of the new taxon is ambiguous largely due to the immature nature of the specimens upon which it was based. Here we reexamine cranial elements of the Prince Creek Formation hadrosaurine in order to solve its taxonomic uncertainties. The Prince Creek Formation hadrosaurine possesses a short dorsolateral process of the laterosphenoid, one of the diagnostic characters of Edmontosaurus. The Prince Creek Formation hadrosaurine also shows affinity to Edmontosaurus regalis in the presence of a horizontal shelf of the jugal. Our morphological comparisons with other North American Edmontosaurus specimens and our phylogenetic analyses demonstrate that the Prince Creek Formation hadrosaurine should be reassigned to Edmontosaurus. Because the Prince Creek Formation Edmontosaurus shows differences with lower latitude Edmontosaurus in a dorsoventrally short maxilla, presence of a secondary ridge on the dentary teeth, and the absence of the transverse ridge between basipterygoid processes of the basisphenoid, we consider that the Prince Creek Formation Edmontosaurus should be regarded as Edmontosaurus sp. until further discoveries of mature hadrosaurines from the Prince Creek Formation Bonebed and/or equivalently juvenile Edmontosaurus specimens from the lower latitudes allow direct comparisons. The retention of the Prince Creek Formation hadrosaurine as Edmontosaurus re-establishes a significant latitudinal distribution for this taxon. Despite the large latitudinal distribution of the taxon, the morphological disparity of Edmontosaurus is small within Hadrosaurinae. The small morphological disparity may be related to the relatively low latitudinal temperature gradient during the latest Cretaceous compared to present day, a gradient which might not have imposed significant pressure for much morphological adaptations across a broad latitudinal range.
Compared to the osteological record of herbivorous dinosaurs from the Late Cretaceous Prince Cree... more Compared to the osteological record of herbivorous dinosaurs from the Late Cretaceous Prince Creek Formation of northern Alaska, there are relatively fewer remains of theropods. The theropod record from this unit is mostly comprised of isolated teeth, and the only non-dental remains known can be attributed to the troodontid cf. Troodon and the tyrannosaurid Nanuqsaurus. Thus far, the presence of members of Dromaeosauridae has been limited to isolated teeth. Here we describe a symphyseal portion of a small dentary with two ziphodont teeth. Based on tooth shape, denticle morphology, and the position of the Meckelian groove, we attribute this partial dentary to a saurornitholestine dromaeosaurid. The fibrous bone surface, small size, and higher number of mesial denticles compared to distal ones point to a juvenile growth stage for this individual. Multivariate comparison of theropod teeth morphospace by means of principal component analysis reveals an overlap between this dentary and Saurornitholestinae dromaeosaurid morphospace, a result supported by phylogenetic analyses. This is the first confirmed non-dental fossil specimen from a member of Dromaeosauridae in the Arctic, expanding on the role of Beringia as a dispersal route for this clade between Asia and North America. Furthermore, the juvenile nature of this individual adds to a growing body of data that suggests Cretaceous Arctic dinosaurs of Alaska did not undergo long-distance migration, but rather they were year-round residents of these paleopolar latitudes.
Re-examination of the cranial osteology of the Arctic Alaskan hadrosaurine with implications for its taxonomic status, 2020
Hadrosaurid fossils from the Liscomb Bonebed (Prince Creek Formation, North Slope, Alaska) were t... more Hadrosaurid fossils from the Liscomb Bonebed (Prince Creek Formation, North Slope, Alaska) were the first dinosaur bones discovered from the Arctic. While the Prince Creek Formation hadrosaurids were long identified as Edmontosaurus, a member of the sub-clade Hadrosaurinae, they were recently assigned to a newly-erected taxon, Ugrunaaluk kuukpi-kensis. However, taxonomic status of the new taxon is ambiguous largely due to the immature nature of the specimens upon which it was based. Here we reexamine cranial elements of the Prince Creek Formation hadrosaurine in order to solve its taxonomic uncertainties.
New Frontiers in Paleopedology and Terrestrial Paleoclimatology: Paleosols and Soil Surface Analog Systems
ABSTRACT The Cretaceous (Early Maastrichtian), dinosaur-bearing Prince Creek Formation (Fm.) expo... more ABSTRACT The Cretaceous (Early Maastrichtian), dinosaur-bearing Prince Creek Formation (Fm.) exposed along the Colville River in northern Alaska records high-latitude, alluvial sedimentation and soil formation on a low-gradient, muddy coastal plain during a greenhouse phase in Earth history. We combine sedimentology, paleopedology, palynology, and paleontology in order to reconstruct detailed local paleoenvironments of an ancient Arctic coastal plain. The Prince Creek Fm. contains quartz-and chert-rich sandstone and mudstone-filled trunk and distributary channels and floodplains composed of organic-rich siltstone and mudstone, carbonaceous shale, coal, and ash-fall deposits. Compound and cumulative, weakly developed soils formed on levees, point bars, crevasse splays, and along the margins of floodplain lakes, ponds, and swamps. Abundant organic matter, carbonaceous root traces, Fe-oxide depletion coatings, and zoned peds (soil aggregates with an outermost Fe-depleted zone, darker-colored Fe-rich matrix, and lighter-colored Fe-poor center) indicate periodic waterlogging, anoxia, and gleying, consistent with a high water table. In contrast, Fe-oxide mottles, ferruginous and manganiferous segregations, bioturbation, and rare illuvial clay coatings indicate recurring oxidation and periodic drying of some soils. Trampling of sediments by dinosaurs is common. A marine influence on pedogenesis in distal coastal plain settings is indicated by jarosite mottles and halos surrounding rhizoliths and the presence of pyrite and secondary gypsum. Floodplains were dynamic, and soil-forming processes were repeatedly interrupted by alluviation, resulting in weakly developed soils similar to modern aquic subgroups of Entisols and Inceptisols and, in more distal locations, potential acid sulfate soils. Biota, including peridinioid dinocysts, brackish and freshwater algae, fungal hyphae, fern and moss spores, projectates, age-diagnostic Wodehouseia edmontonicola, hinterland bisaccate pollen, and pollen from lowland trees, shrubs, and herbs record a diverse flora and indicate an Early Maastrichtian age for all sediments in the study area. The assemblage also demonstrates that although all sediments are Early Maastrichtian, strata become progressively younger from south to north. A paleoenvironmental reconstruction integrating pedogenic processes and biota indicates that polar woodlands with an angiosperm understory and dinosaurs flourished on this ancient Arctic coastal plain that was influenced by seasonally(?) fluctuating water table levels and floods. In contrast to modern polar environments, there is no evidence for periglacial conditions on the Cretaceous Arctic coastal plain, and both higher temperatures and an intensified hydrological cycle existed, although the polar light regime was similar to that of the present. In the absence of evidence of cryogenic processes in paleosols, it would be very difficult to determine a high-latitude setting for paleosol formation without independent evidence for paleolatitude. Consequently, paleosols formed at high latitudes under greenhouse conditions, in the absence of ground ice, are not likely to have unique pedogenic signatures.
The Late Cretaceous (Campanian-Maastrichtian) Prince Creek Formation is the most dinosaur-rich hi... more The Late Cretaceous (Campanian-Maastrichtian) Prince Creek Formation is the most dinosaur-rich high latitude formation in the world, but there is little detailed work that integrates paleontological sites with sedimentology, paleopedology and palynology. Facies associations of the Prince Creek Formation near the Kikak-Tegoseak dinosaur site, indicate that, overall, the depositional environment was a low-energy, swampy alluvial/coastal plain. Facies associations include fine-grained lakes, lake margins, levees, crevasse splays and paleosols on floodplains, and coarser-grained, ripple cross-laminated, non-migrating channel deposits. Rare, multi-story, sheet sandstones are present in nearby areas. Organic-rich siltstones and thin coaly shales are common. Overbank mudstones and siltstones contain root traces, drab colors, blocky structures, Fe-oxide mottles and siderite nodules indicating the presence of abundant, poorly drained paleosols. Redoximorphic features, such as ferruginous voi...
The collection and dissemination of vertebrate ichnological data is struggling to keep up with te... more The collection and dissemination of vertebrate ichnological data is struggling to keep up with techniques that are becoming commonplace in the wider palaeontological field. A standard protocol is required to ensure that data is recorded, presented and archived in a manner that will be useful both to contemporary
The northernmost record of Metatheria, Unnuakomys hutchisoni gen. et sp. nov., is described from ... more The northernmost record of Metatheria, Unnuakomys hutchisoni gen. et sp. nov., is described from the Pediomys Point locality in Upper Cretaceous (lower Maastrichtian) strata of the Prince Creek Formation cropping out along the Colville River on the North Slope of Alaska, USA (70°N). Based on over 60 specimens (including tooth-bearing dentaries and a maxillary fragment), the new taxon is unusual in having two well-developed stylar cusps in the C position flanking the deepest part of the ectoflexus. To examine the relationship between U. hutchisoni and other metatherians, U. hutchisoni was scored into the taxon character matrix of other studies. Our results corroborate prior studies that suggest the new Alaskan pediomyid. However, in contrast to other studies, we do not recover a sister-group relationship between U. hutchisoni and Pediomys elegans. Rather, our study suggests that U. hutchisoni is more closely allied with Aquilan species Iqualadelphis lactea and ?Aquiladelphis laurae. Teeth of U. hutchisoni greatly outnumber those recovered from other mammals at Pediomys Point, like Late Cretaceous localities in the Western Interior where metatherians are among the most abundant mammalian fossils. However, what differs between Late Cretaceous mid-latitude localities and the assemblage from the North Slope of Alaska is metatherian richness. Whereas other studies have reported up to a dozen species of metatherians from Late Cretaceous mid-latitude North American assemblages, to date all the metatherian teeth collected from Pediomys Point appear to belong to just U. hutchisoni. A sampling bias may play a role in this pattern. This can be tested through additional collection from the Prince Creek Formation. However, the abundance of U. hutchisoni at Pediomys Point implies that this tiny metatherian thrived in an environment well above the Arctic Circle whose climatic extremes may have acted as a biogeographical filter to other metatherians. As the first mammal to be described from the Prince Creek Formation, U. hutchisoni provides support for the existence of a northern high-latitude early Maastrichtian faunal province identified by others on the basis of its distinctive dinosaurian fauna – the Paaŋaqtat Province. http://zoobank.org/urn:lsid:zoobank.org:pub:0EF38E01-2FF4-4698-A3AD-97CF2EE6847A
We report details of a unique association of hadrosaur and therizinosaur tracks found in the Late... more We report details of a unique association of hadrosaur and therizinosaur tracks found in the Late Cretaceous lower Cantwell Formation, Denali National Park, central Alaska Range, Alaska. This rock unit is now well-documented as a source of thousands of fossil footprints of vertebrates such as fishes, pterosaurs, and avialan and non-avialan dinosaurs. The lower Cantwell Formation in this area consists of numerous fining-upward successions of conglomerates and pebbly sandstones, cross-stratified and massive sandstones, interbedded sandstones and siltstones, organic-rich siltstones and shales, and rare, thin, bentonites, typically bounded by thin coal seams, and it contains a diverse fossil flora. We report the first North American co-occurrence of tracks attributable to hadrosaurs and therizinosaurs in the lower Cantwell Formation. Although previously un-reported in North America, this association of hadrosaur and therizinosaur tracks is more characteristic of the correlative Nemegt F...
The collection and dissemination of vertebrate ichnological data is struggling to keep up with te... more The collection and dissemination of vertebrate ichnological data is struggling to keep up with techniques that are becoming commonplace in the wider palaeontological field. A standard protocol is required to ensure that data is recorded, presented and archived in a manner that will be useful both to contemporary
Introduction National park units have at times been referred to as “ecological islands.” More rec... more Introduction National park units have at times been referred to as “ecological islands.” More recently, such units have begun to be viewed as ecological mosaics rather than separate island units as managers of publicly owned, federally managed lands have increasingly gained an appreciation for park boundaries and their relationships to particular biological issues. It is often apparent to these managers that individual park boundaries may not fully encompass appropriate habitat areas for managing biological resources. As a result, partnerships have been sought within and between land management agencies to best accommodate the needs of these biological resources. In order to understand the natural world of today, one must examine the past. Studies such as those discussed below show that fossils are more than oddities of the rock record; they represent the record of life that has evolved on this planet. They are the means to test the scale and robustness of ecological principles obse...
<p>Ontogenetic stages of nasal boss development in <i>Pachyrhinosaurus</i> (Sta... more <p>Ontogenetic stages of nasal boss development in <i>Pachyrhinosaurus</i> (Stage 1 youngest), based upon descriptions and inferences of Currie et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065802#pone.0065802-Currie1" target="_blank">[4]</a>.</p
Faunal abundance and fossil size and shape data from microvertebrate localities in the Upper Cret... more Faunal abundance and fossil size and shape data from microvertebrate localities in the Upper Cretaceous Judith River Formation of south-central Montana illustrate that even when located in similar sedimentary facies, concentrations of vertebrate microfossils may exhibit strikingly different taphonomic profiles. Degrees of microfossil size and shape sorting may vary even among sites from the same sedimentary facies. In some instances, such variations may make it impossible to disregard taphonomic causes for differences sites exhibit in paleofaunal abundances. To limit the possibility that taphonomically generated faunal differences might be mistaken for true differences in paleoecology, comparisons of paleofaunal abundances should be restricted to microvertebrate sites both from similar sedimentary facies and with similar profiles of fossil sizes and shapes.
Faunal abundance and fossil size and shape data from microvertebrate localities in the Upper Cret... more Faunal abundance and fossil size and shape data from microvertebrate localities in the Upper Cretaceous Judith River Formation of south-central Montana illustrate that even when located in similar sedimentary facies, concentrations of vertebrate microfossils may exhibit strikingly different taphonomic profiles. Degrees of microfossil size and shape sorting may vary even among sites from the same sedimentary facies. In some instances, such variations may make it impossible to disregard taphonomic causes for differences sites exhibit in paleofaunal abundances. To limit the possibility that taphonomically generated faunal differences might be mistaken for true differences in paleoecology, comparisons of paleofaunal abundances should be restricted to microvertebrate sites both from similar sedimentary facies and with similar profiles of fossil sizes and shapes.
We report on the first record of a pterosaur from Alaska. This record consists of a single manus ... more We report on the first record of a pterosaur from Alaska. This record consists of a single manus track from the lower part of the Upper Cretaceous Cantwell Formation in Denali National Park, Alaska, United States, making this the northernmost occurrence for this group of reptiles. The specimen is from deposits that record a low-lying floodplain with small lakes and ponds, dissected by small channels that fed a larger tributary stream on an active fan lobe. The dominant vegetation was comprised of conifers with an understory of ferns and horsetails.
Mid-Cenozoic marine mammals of Alaska were isolated from the Arctic Ocean by Beringia and were th... more Mid-Cenozoic marine mammals of Alaska were isolated from the Arctic Ocean by Beringia and were thus part of a far North Pacific ecosystem. The amphicynodontid ?Kolponomos, a neocete whale, and a desmostylian were found in the latest Oligocene or earliest Miocene (approximately 23 Ma) Dutch Harbor Member of the Unalaska Formation, Aleutian Chain, Alaska. The Unalaska desmostylian is more derived than Cornwallius but more primitive than Desmostylus. Derived desmostylians are known from the early middle Miocene (16-15 Ma) Bear Lake Formation on the Alaska Peninsula and the Narrow Cape Formation on Kodiak Island. The Miocene Yakatat Formation has produced sparse mammal remains but records the onset of montane glaciation in southern Alaska.
FLAIG, Peter P. 1, HASIOTIS, ST 2, VAN DER KOLK, Dolores A. 1, and FIORILLO, Anthony 3,(1) Bureau... more FLAIG, Peter P. 1, HASIOTIS, ST 2, VAN DER KOLK, Dolores A. 1, and FIORILLO, Anthony 3,(1) Bureau of Economic Geology, University of Texas at Austin, Jackson School of Geosciences, 10100 Burnet Rd, Austin, TX 78758, peter. flaig@ beg. utexas. edu,(2) ...
Hadrosaurid fossils from the Liscomb Bonebed (Prince Creek Formation, North Slope, Alaska) were t... more Hadrosaurid fossils from the Liscomb Bonebed (Prince Creek Formation, North Slope, Alaska) were the first dinosaur bones discovered from the Arctic. While the Prince Creek Formation hadrosaurids were long identified as Edmontosaurus, a member of the sub-clade Hadrosaurinae, they were recently assigned to a newly-erected taxon, Ugrunaaluk kuukpikensis. However, taxonomic status of the new taxon is ambiguous largely due to the immature nature of the specimens upon which it was based. Here we reexamine cranial elements of the Prince Creek Formation hadrosaurine in order to solve its taxonomic uncertainties. The Prince Creek Formation hadrosaurine possesses a short dorsolateral process of the laterosphenoid, one of the diagnostic characters of Edmontosaurus. The Prince Creek Formation hadrosaurine also shows affinity to Edmontosaurus regalis in the presence of a horizontal shelf of the jugal. Our morphological comparisons with other North American Edmontosaurus specimens and our phylogenetic analyses demonstrate that the Prince Creek Formation hadrosaurine should be reassigned to Edmontosaurus. Because the Prince Creek Formation Edmontosaurus shows differences with lower latitude Edmontosaurus in a dorsoventrally short maxilla, presence of a secondary ridge on the dentary teeth, and the absence of the transverse ridge between basipterygoid processes of the basisphenoid, we consider that the Prince Creek Formation Edmontosaurus should be regarded as Edmontosaurus sp. until further discoveries of mature hadrosaurines from the Prince Creek Formation Bonebed and/or equivalently juvenile Edmontosaurus specimens from the lower latitudes allow direct comparisons. The retention of the Prince Creek Formation hadrosaurine as Edmontosaurus re-establishes a significant latitudinal distribution for this taxon. Despite the large latitudinal distribution of the taxon, the morphological disparity of Edmontosaurus is small within Hadrosaurinae. The small morphological disparity may be related to the relatively low latitudinal temperature gradient during the latest Cretaceous compared to present day, a gradient which might not have imposed significant pressure for much morphological adaptations across a broad latitudinal range.
Compared to the osteological record of herbivorous dinosaurs from the Late Cretaceous Prince Cree... more Compared to the osteological record of herbivorous dinosaurs from the Late Cretaceous Prince Creek Formation of northern Alaska, there are relatively fewer remains of theropods. The theropod record from this unit is mostly comprised of isolated teeth, and the only non-dental remains known can be attributed to the troodontid cf. Troodon and the tyrannosaurid Nanuqsaurus. Thus far, the presence of members of Dromaeosauridae has been limited to isolated teeth. Here we describe a symphyseal portion of a small dentary with two ziphodont teeth. Based on tooth shape, denticle morphology, and the position of the Meckelian groove, we attribute this partial dentary to a saurornitholestine dromaeosaurid. The fibrous bone surface, small size, and higher number of mesial denticles compared to distal ones point to a juvenile growth stage for this individual. Multivariate comparison of theropod teeth morphospace by means of principal component analysis reveals an overlap between this dentary and Saurornitholestinae dromaeosaurid morphospace, a result supported by phylogenetic analyses. This is the first confirmed non-dental fossil specimen from a member of Dromaeosauridae in the Arctic, expanding on the role of Beringia as a dispersal route for this clade between Asia and North America. Furthermore, the juvenile nature of this individual adds to a growing body of data that suggests Cretaceous Arctic dinosaurs of Alaska did not undergo long-distance migration, but rather they were year-round residents of these paleopolar latitudes.
Re-examination of the cranial osteology of the Arctic Alaskan hadrosaurine with implications for its taxonomic status, 2020
Hadrosaurid fossils from the Liscomb Bonebed (Prince Creek Formation, North Slope, Alaska) were t... more Hadrosaurid fossils from the Liscomb Bonebed (Prince Creek Formation, North Slope, Alaska) were the first dinosaur bones discovered from the Arctic. While the Prince Creek Formation hadrosaurids were long identified as Edmontosaurus, a member of the sub-clade Hadrosaurinae, they were recently assigned to a newly-erected taxon, Ugrunaaluk kuukpi-kensis. However, taxonomic status of the new taxon is ambiguous largely due to the immature nature of the specimens upon which it was based. Here we reexamine cranial elements of the Prince Creek Formation hadrosaurine in order to solve its taxonomic uncertainties.
New Frontiers in Paleopedology and Terrestrial Paleoclimatology: Paleosols and Soil Surface Analog Systems
ABSTRACT The Cretaceous (Early Maastrichtian), dinosaur-bearing Prince Creek Formation (Fm.) expo... more ABSTRACT The Cretaceous (Early Maastrichtian), dinosaur-bearing Prince Creek Formation (Fm.) exposed along the Colville River in northern Alaska records high-latitude, alluvial sedimentation and soil formation on a low-gradient, muddy coastal plain during a greenhouse phase in Earth history. We combine sedimentology, paleopedology, palynology, and paleontology in order to reconstruct detailed local paleoenvironments of an ancient Arctic coastal plain. The Prince Creek Fm. contains quartz-and chert-rich sandstone and mudstone-filled trunk and distributary channels and floodplains composed of organic-rich siltstone and mudstone, carbonaceous shale, coal, and ash-fall deposits. Compound and cumulative, weakly developed soils formed on levees, point bars, crevasse splays, and along the margins of floodplain lakes, ponds, and swamps. Abundant organic matter, carbonaceous root traces, Fe-oxide depletion coatings, and zoned peds (soil aggregates with an outermost Fe-depleted zone, darker-colored Fe-rich matrix, and lighter-colored Fe-poor center) indicate periodic waterlogging, anoxia, and gleying, consistent with a high water table. In contrast, Fe-oxide mottles, ferruginous and manganiferous segregations, bioturbation, and rare illuvial clay coatings indicate recurring oxidation and periodic drying of some soils. Trampling of sediments by dinosaurs is common. A marine influence on pedogenesis in distal coastal plain settings is indicated by jarosite mottles and halos surrounding rhizoliths and the presence of pyrite and secondary gypsum. Floodplains were dynamic, and soil-forming processes were repeatedly interrupted by alluviation, resulting in weakly developed soils similar to modern aquic subgroups of Entisols and Inceptisols and, in more distal locations, potential acid sulfate soils. Biota, including peridinioid dinocysts, brackish and freshwater algae, fungal hyphae, fern and moss spores, projectates, age-diagnostic Wodehouseia edmontonicola, hinterland bisaccate pollen, and pollen from lowland trees, shrubs, and herbs record a diverse flora and indicate an Early Maastrichtian age for all sediments in the study area. The assemblage also demonstrates that although all sediments are Early Maastrichtian, strata become progressively younger from south to north. A paleoenvironmental reconstruction integrating pedogenic processes and biota indicates that polar woodlands with an angiosperm understory and dinosaurs flourished on this ancient Arctic coastal plain that was influenced by seasonally(?) fluctuating water table levels and floods. In contrast to modern polar environments, there is no evidence for periglacial conditions on the Cretaceous Arctic coastal plain, and both higher temperatures and an intensified hydrological cycle existed, although the polar light regime was similar to that of the present. In the absence of evidence of cryogenic processes in paleosols, it would be very difficult to determine a high-latitude setting for paleosol formation without independent evidence for paleolatitude. Consequently, paleosols formed at high latitudes under greenhouse conditions, in the absence of ground ice, are not likely to have unique pedogenic signatures.
The Late Cretaceous (Campanian-Maastrichtian) Prince Creek Formation is the most dinosaur-rich hi... more The Late Cretaceous (Campanian-Maastrichtian) Prince Creek Formation is the most dinosaur-rich high latitude formation in the world, but there is little detailed work that integrates paleontological sites with sedimentology, paleopedology and palynology. Facies associations of the Prince Creek Formation near the Kikak-Tegoseak dinosaur site, indicate that, overall, the depositional environment was a low-energy, swampy alluvial/coastal plain. Facies associations include fine-grained lakes, lake margins, levees, crevasse splays and paleosols on floodplains, and coarser-grained, ripple cross-laminated, non-migrating channel deposits. Rare, multi-story, sheet sandstones are present in nearby areas. Organic-rich siltstones and thin coaly shales are common. Overbank mudstones and siltstones contain root traces, drab colors, blocky structures, Fe-oxide mottles and siderite nodules indicating the presence of abundant, poorly drained paleosols. Redoximorphic features, such as ferruginous voi...
The collection and dissemination of vertebrate ichnological data is struggling to keep up with te... more The collection and dissemination of vertebrate ichnological data is struggling to keep up with techniques that are becoming commonplace in the wider palaeontological field. A standard protocol is required to ensure that data is recorded, presented and archived in a manner that will be useful both to contemporary
The northernmost record of Metatheria, Unnuakomys hutchisoni gen. et sp. nov., is described from ... more The northernmost record of Metatheria, Unnuakomys hutchisoni gen. et sp. nov., is described from the Pediomys Point locality in Upper Cretaceous (lower Maastrichtian) strata of the Prince Creek Formation cropping out along the Colville River on the North Slope of Alaska, USA (70°N). Based on over 60 specimens (including tooth-bearing dentaries and a maxillary fragment), the new taxon is unusual in having two well-developed stylar cusps in the C position flanking the deepest part of the ectoflexus. To examine the relationship between U. hutchisoni and other metatherians, U. hutchisoni was scored into the taxon character matrix of other studies. Our results corroborate prior studies that suggest the new Alaskan pediomyid. However, in contrast to other studies, we do not recover a sister-group relationship between U. hutchisoni and Pediomys elegans. Rather, our study suggests that U. hutchisoni is more closely allied with Aquilan species Iqualadelphis lactea and ?Aquiladelphis laurae. Teeth of U. hutchisoni greatly outnumber those recovered from other mammals at Pediomys Point, like Late Cretaceous localities in the Western Interior where metatherians are among the most abundant mammalian fossils. However, what differs between Late Cretaceous mid-latitude localities and the assemblage from the North Slope of Alaska is metatherian richness. Whereas other studies have reported up to a dozen species of metatherians from Late Cretaceous mid-latitude North American assemblages, to date all the metatherian teeth collected from Pediomys Point appear to belong to just U. hutchisoni. A sampling bias may play a role in this pattern. This can be tested through additional collection from the Prince Creek Formation. However, the abundance of U. hutchisoni at Pediomys Point implies that this tiny metatherian thrived in an environment well above the Arctic Circle whose climatic extremes may have acted as a biogeographical filter to other metatherians. As the first mammal to be described from the Prince Creek Formation, U. hutchisoni provides support for the existence of a northern high-latitude early Maastrichtian faunal province identified by others on the basis of its distinctive dinosaurian fauna – the Paaŋaqtat Province. http://zoobank.org/urn:lsid:zoobank.org:pub:0EF38E01-2FF4-4698-A3AD-97CF2EE6847A
We report details of a unique association of hadrosaur and therizinosaur tracks found in the Late... more We report details of a unique association of hadrosaur and therizinosaur tracks found in the Late Cretaceous lower Cantwell Formation, Denali National Park, central Alaska Range, Alaska. This rock unit is now well-documented as a source of thousands of fossil footprints of vertebrates such as fishes, pterosaurs, and avialan and non-avialan dinosaurs. The lower Cantwell Formation in this area consists of numerous fining-upward successions of conglomerates and pebbly sandstones, cross-stratified and massive sandstones, interbedded sandstones and siltstones, organic-rich siltstones and shales, and rare, thin, bentonites, typically bounded by thin coal seams, and it contains a diverse fossil flora. We report the first North American co-occurrence of tracks attributable to hadrosaurs and therizinosaurs in the lower Cantwell Formation. Although previously un-reported in North America, this association of hadrosaur and therizinosaur tracks is more characteristic of the correlative Nemegt F...
The collection and dissemination of vertebrate ichnological data is struggling to keep up with te... more The collection and dissemination of vertebrate ichnological data is struggling to keep up with techniques that are becoming commonplace in the wider palaeontological field. A standard protocol is required to ensure that data is recorded, presented and archived in a manner that will be useful both to contemporary
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Papers by Tony Fiorillo