Late Cretaceous Dinosaur Research Articles

Cranial histology of pachycephalosaurs (Ornithischia: Marginocephalia) reveals transitory structures inconsistent with head-butting behavior

Abstract Modern histological techniques allow paleontologists to investigate the internal microstructure of bone tissue. We apply high resolution images of histological thin sections from an ontogenetic series (not conspecific) of pachycephalosaurid frontoparietal domes to test the hypothesis that these Late Cretaceous dinosaurs used their heads as battering rams, analogous to the behavior of the bighorn sheep, Ovis canadensis, or as a thermoregulatory device. Our analysis reveals that the internal structure of the pachycephalosaur dome is a dynamic tissue that reflects the changeable expansion and vascularity of the dome throughout ontogeny. The radiating structures within the frontoparietal dome, used previously to support “head-butting” hypotheses, are unexpectedly transitory, diminishing in mature individuals and nearly absent in adult skulls where head-butting behavior is presumed to occur. The unique architecture of the pachycephalosaurid dome is dividable into three distinct Zones. We demonstrate t...

Quo Vadis? Paleoenvironmental and Diagenetic Constraints on Late Cretaceous Dinosaur Skin from Western North America

Quo Vadis? Paleoenvironmental and Diagenetic Constraints on Late Cretaceous Dinosaur Skin from Western North America

An Early Late Cretaceous Dinosaur Tracksite in Central Yukon Territory, Canada

Dinosaur tracks were first reported from the coal-bearing clastic sequences of the Ross River Block in 1999 by members of a University of Alaska Museum field party, and track sites were confirmed by a joint Alaska-Yukon team in 2000. This fault-bounded sedimentary block is 3 kilometers west of Ross River, in the Yukon Territory. The discovery was followed by two years of field mapping and collection. This research has resulted in the documentation of 251 individual tracks at two separate but stratigraphically related sites, as well as a short (four-footprint) trackway at one of the sites. Six ichnogenera were identified. Ornithomimipus, Amblydactylus, and Gypsichnites were recognized at one site. At a stratigraphically higher site, four ichnogenera were documented including Tetrapodosaurus, Irenesauripus, Amblydactylus, and Columbosauripus. This ichno-assemblage is compared with those of Aptian to Cenomanian age from Alberta, British Columbia, and Alaska. The discovery of unequivocal dinosaur evidence in a small structural inlier in the Tintina Trench that was previously assumed to be Eocene in age resulted in a restudy of the palynology and biostratigraphy of this coal-bearing sequence and the recent assignment of a middle Albian to early Cenomanian age to the upper part of the dinosaur-bearing interval.

A new eucryptodiran turtle from the Late Cretaceous of North America (Dinosaur Provincial Park, Alberta, Canada)

ABSTRACT The holotype of Judithemys sukhanovi gen et. sp. nov. from the Late Cretaceous (Campanian) Dinosaur Park Formation of Alberta, Canada, has been included in four cladistic analyses. New material allows for a more complete description of this taxon. Judithemys sukhanovi is represented by 65 specimens (most very fragmentary) including one virtually complete skeleton (the holotype) and several partial shells. It differs from all other “macrobaenids” in the combination of wide vertebral scales, absence of central plastral fontanelles, and lack of strongly upturned peripherals. The morphology of Judithemys reiterates a suite of characters (large size, well-differentiated neurals reduced to eight, and greater overlap of the twelfth marginal scales onto the second suprapygal) common to Late Cretaceous–Paleocene “macrobaenids” and distinct from Early Cretaceous members. Judithemys and “Clemmys” backmani are close in morphology, geography, and stratigraphie position and are possibly closely related phylogenetically. A preliminary phylogenetic analysis supports the hypothesis that Judithemys is not part of the crown group.

Late Cretaceous dinosaurs from the Denver Basin, Colorado

Late Cretaceous dinosaurs have been known from the Denver Basin, Colorado, since the mid-1860s. Most of the fossils are scrappy, although several fragmentary skeletons are known. Most recently discovered specimens are the result of salvage work at construction sites in the Denver metropolitan area. Dinosaurs from the Denver Basin include Triceratops , Torosaurus , Edmontosaurus , Thescelosaurus , Edmontonia , Pachycephalosaurus , Tyrannosaurus , a dromaeosaurid, and Ornithomimus . All of these taxa are also known from the Lance, Hell Creek, and Scollard Formations to the north and are known collectively as the Lancian fauna. Thus, these Late Cretaceous dinosaurs from Colorado are the southeastern-most extension of the Lancian fauna. Furthermore, there may be ecological segregation of some taxa based on their facies distribution, with Thescelosaurus and Torosaurus restricted to the wetter lowlands and Ornithomimus and possibly Pachycephalosaurus to the better drained uplands.

Late Cretaceous dinosaurs from the Denver Basin, Colorado

Late Cretaceous dinosaurs from the Denver Basin, Colorado

Tail-Drag Marks and Dinosaur Footprints from the Upper Cretaceous Toreva Formation, Northeastern Arizona

Other| October 01, 2002 Tail-Drag Marks and Dinosaur Footprints from the Upper Cretaceous Toreva Formation, Northeastern Arizona GRACE V. IRBY; GRACE V. IRBY 1Department of Geology, Museum of Northern Arizona, Flagstaff, AZ 86001 Search for other works by this author on: GSW Google Scholar L. BARRY ALBRIGHT, III L. BARRY ALBRIGHT, III 1Department of Geology, Museum of Northern Arizona, Flagstaff, AZ 86001 Search for other works by this author on: GSW Google Scholar PALAIOS (2002) 17 (5): 516–521. https://doi.org/10.1669/0883-1351(2002)017<0516:TDMADF>2.0.CO;2 Article history accepted: 12 Apr 2002 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation GRACE V. IRBY, L. BARRY ALBRIGHT; Tail-Drag Marks and Dinosaur Footprints from the Upper Cretaceous Toreva Formation, Northeastern Arizona. PALAIOS 2002;; 17 (5): 516–521. doi: https://doi.org/10.1669/0883-1351(2002)017<0516:TDMADF>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract The first Late Cretaceous dinosaur tracksite recorded from Arizona, preserving over 100 footprints, also preserves sinuous grooves here interpreted to be impressions left by the tail of a large vertebrate as it dragged through sediment now assigned to the Toreva Formation. Although no footprints are preserved that can be referred unambiguously to the individual or individuals that produced the tail-drag marks, the dynamic nature of the surface upon which the tracks were made, likely a river or stream shoreline, could have easily resulted in their disturbance or obliteration. As best as can be determined on the basis of a depauperate marine fauna from the lower part of the unit, and on the basis of a substantial hiatus that separates the lower and upper parts, the site is probably middle Coniacian in age. These tracks and drag marks add significantly to the exceptionally rare record of terrestrial vertebrates known from the Toreva Formation. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A TEST FOR DECLINING DIVERSITY

A common problem in applied ecology is to determine whether the diversity of a biological community declines along a gradient. This note describes a statistical test for such a decline. The test is based on a combination of nonlinear optimization and a parametric bootstrap. An illustration involving late Cretaceous dinosaur diversity is presented.

Late Campanian southern dinosaurs, Aguja Formation, Big Bend, Texas

One of the southernmost North American late Campanian microvertebrate assemblages was collected from the upper Aguja Formation, Big Bend National Park, Texas. The dinosaurs provide additional evidence that distinct southern and northern terrestrial vertebrate provinces occurred contemporaneously during this time due to latitudinal differences in temperature and rainfall. Southern areas, such as west Texas, were warm dry, with non-seasonal climates, and with open-canopy woodlands; they appear to be less fossil-rich and less diverse than northern areas. Nine dinosaurs are present, based on isolated teeth: pachycephalosaurid; hadrosaurid; ceratopsian; tyrannosaurid; Saurornitholestes cf. langstoni (Sues, 1978); Richardoestesia cf. gilmorei (Currie et al., 1990); a new species of Richardoestesia, which is named here; and a undetermined theropod unlike any previously described. Previous reports of Troodon sp. from the Talley Mt. and Terlingua microsites are mistaken; they are a pachycephalosaurid. Many of the dinosaur teeth are small, and are probably from juveniles or younger individuals, evidence that dinosaurs nested in the area. Paleoecologically, the upper Aguja was probably more similar to the lower and more inland faunas of the Scollard Formation (~66 Ma) of Alberta than to contemporaneous northern faunas: both had drier, open environments and lower dinosaur abundance. This connection between climate and dinosaur abundance suggests that climatic factors were important in the Late Cretaceous dinosaur extinctions.

LATE CAMPANIAN SOUTHERN DINOSAURS, AGUJA FORMATION, BIG BEND, TEXAS

One of the southernmost North American late Campanian microvertebrate assemblages was collected from the upper Aguja Formation, Big Bend National Park, Texas. The dinosaurs provide additional evidence that distinct southern and northern terrestrial vertebrate provinces occurred contemporaneously during this time due to latitudinal differences in temperature and rainfall. Southern areas, such as west Texas, were warm dry, with non-seasonal climates, and with open-canopy woodlands; they appear to be less fossil-rich and less diverse than northern areas. Nine dinosaurs are present, based on isolated teeth: pachycephalosaurid; hadrosaurid; ceratopsian; tyrannosaurid; Saurornitholestes cf. langstoni (Sues, 1978); Richardoestesia cf. gilmorei (Currie et al., 1990); a new species of Richardoestesia, which is named here; and a undetermined theropod unlike any previously described. Previous reports of Troodon sp. from the Talley Mt. and Terlingua microsites are mistaken; they are a pachycephalosaurid. Many of the dinosaur teeth are small, and are probably from juveniles or younger individuals, evidence that dinosaurs nested in the area. Paleoecologically, the upper Aguja was probably more similar to the lower and more inland faunas of the Scollard Formation (~66 Ma) of Alberta than to contemporaneous northern faunas: both had drier, open environments and lower dinosaur abundance. This connection between climate and dinosaur abundance suggests that climatic factors were important in the Late Cretaceous dinosaur extinctions.

Video review:Walking with Dinosaurs

We present the first systematic study of Ca isotopes (δ44/40Ca) in Late Triassic to Late Cretaceous dinosaur bones and teeth (enamel and dentin) from sympatric herbivorous and carnivorous dinosaurs. The samples derive from five different localities, and data from embedding sediments are also presented. Additional δ44/40Ca in skeletal tissues from modern reptiles and birds (avian dinosaurs) were measured for comparison in order to examine whether the original Ca isotopic composition in dinosaur skeletal apatite was preserved or might have changed during the diagenesis and fossilization process.δ44/40Ca of fossil skeletal tissues range from −1.62‰ (Tyrannosaurus rex enamel) to +1.08‰ (Brachiosaurus brancai bone), while values in modern archosaur bones and teeth range from −1.63‰ (caiman enamel) to −0.37‰ (ostrich bone). The average δ44/40Ca of the three types of fossil skeletal tissue analyzed – bone, dentin and enamel – show some systematic differences: while δ44/40Ca in bone exhibits the highest values, while δ44/40Ca in enamel has the lowest values, and dentin δ44/40Ca falls in between. Values of δ44/40Ca in the remains of herbivorous dinosaurs (0.1–1.1‰) are generally higher than those of bones of modern mammalian herbivores (−2.6‰ to −0.8‰) and from modern herbivorous archosaurs, which exhibit intermediate δ44/40Ca (−0.8‰ to −0.4‰). These systematic isotopic shifts may reflect physiological differences between dinosaurs, mammals and reptiles representing different taxonomic groups of vertebrates.Systematic offsets in skeletal apatite δ44/40Ca between herbivorous and carnivorous dinosaurs are not obvious, indicating a lack of a clear-cut Trophic Level Effect (TLE) shift between herbivores and carnivores in dinosaurs. This observation can be explained if the carnivorous dinosaurs in this study fed mainly on soft tissues from their prey and did not ingest hard (calcified) tissue to much extent. The most striking indication that the primary δ44/40Ca is actually preserved in most of the fossil teeth is a difference in δ44/40Ca of about 0.35 ± 0.10‰ (1SD) between dentin and enamel, based upon 11 of 16 analyzed dentin-enamel pairs. This difference is close to that found in modern reptiles (0.28 ± 0.05‰), and strongly suggests that this tell-tale signature is a primary feature of the fossilized dinosaur material as well. Furthermore, simple mass balance calculations show that changes of the original δ44/40Ca in bones and teeth by diagenetically-formed calcium-bearing minerals are either small or would require implausible high original δ44/40Ca values in the skeletal apatite.

The carbon isotopic characteristics of dinosaur eggshell fossils in Late Cretaceous from Xixia Basin and their significance

This paper studies the Late Cretaceous dinosaur eggshell fossils from the Xixia Basin, Henan Province, by microscopy and carbon isotope method. Careful observation under microscope revealed that all dinosaur eggshell fossils consist of primary calcite and secondary calcite. The content of the former is about 60.5% and the latter 39.5% according to image analysis. The °13C values of secondary carbonate mineral filling within the dinosaur eggs in the strata range from −5.63‰ to −5.68‰, with an average value of −5. 65‰. The δ13C values of sixteen dinosaur eggshell fossils are in the range from −5.88‰ to −7.79‰ Then we calculated the δ13C values of primary carbonate minerals, ranging from −6.03‰ to −9.19‰ Based on the δ13C values of the primary carbonate, the ancient food type and food proportion of dinosaurs were deduced. The dinosaur’s food proportions of C3 plant and C4 plant are 61% and 39%, respectively. Finally, it is inferred that the palaeoclimate in the Xixia Basin should be a warm—sub-humid—sub-arid climate in the subtropical zone of the Xixia Basin.

Life and death in a Late Cretaceous dune field, Nemegt basin, Mongolia

For more than 70 years, red sandstones of the Gobi Desert have yielded abundant articulated skeletons of Late Cretaceous dinosaurs, lizards, and mammals. At Ukhaa Tolgod, structureless sandstones are the only fossiliferous facies, and we present new evidence for deposition on dune-sand–sourced alluvial fans that were built at the margins of stabilized eolian bedforms during mesic climatic episodes. In laterally and vertically adjacent large-scale eolian cross-strata in which skeletons are absent, we have found abundant tracks of dinosaurs that walked on sparsely vegetated dunes that were active under xeric conditions. Our study of calcareous concretions in vaguely bedded eolian sandstones suggests that bedding was nearly destroyed by burrowing invertebrates and trampling dinosaurs. The accumulation of illuvial clays and pedogenic calcite in these sediments reduced infiltration of rainwater and, with attendant climatic change and heavy rainfall events, led to fan development.

Late Cretaceous dinosaur eggshells from the Tremp Basin, southern Pyrenees, Lleida, Spain

Late Cretaceous dinosaur eggshell assemblages from six localities of the Tremp basin (Southern Pyrenees, Lleida, Spain) are studied and compared with those of Southern France, to correlate their temporal succession. Fontllonga 6 reveals the most diverse eggshell assemblage known so far, with seven oospecies, among which one new structural type (Pseudogeckoolithus nodosus new genus and species), a new Ratite-type eggshell (Ageroolithus fontllongensis new genus and species) and a new Prismatoolithidae are described; four other taxa are shared with Southern France. The correlation of both Spanish and French eggshell successions allows us to recognize three main periods characterised by different eggshell assemblages: a lower assemblage with Megaloolithus petralta, M. aureliensis, Prismatoolithus tenuis and P. matellensis from the French Lower Rognacian and the Spanish sites Fontllonga 6 and Moro; a middle one with M. siruguei from the Middle Rognacian and Biscarri; and a late one from the Late Rognacian with M. mammilare (from Abella and Bastus) and M. pseudomamillare (from Suterranya). Some contradictions appear when comparing results with paleomagnetism and charophyte correlations but the eggshell correlations are consistent with other stratigraphic studies.

Late Cretaceous dinosaurs from the foothills of the Pyrenees

Late Cretaceous dinosaurs from the foothills of the Pyrenees

Late Cretaceous Dinosaurs of the Southeastern United States : ABSTRACT

Late Cretaceous Dinosaurs of the Southeastern United States : ABSTRACT

The Metabolic Status of Some Late Cretaceous Dinosaurs

Analysis of the nasal region in fossils of three theropod dinosaurs ( Nanotyrannus, Ornithomimus, and Dromaeosaurus ) and one ornithischian dinosaur ( Hypacrosaurus ) showed that their metabolic rates were significantly lower than metabolic rates in modern birds and mammals. In extant endotherms and ectotherms, the cross-sectional area of the nasal passage scales approximately with increasing body mass M at M 0.72 . However, the cross-sectional area of nasal passages in endotherms is approximately four times that of ectotherms. The dinosaurs studied here have narrow nasal passages that are consistent with low lung ventilation rates and the absence of respiratory turbinates.

Age Determinations for Late Cretaceous Dinosaur Sites in the New Jersey Coastal Plain

Age Determinations for Late Cretaceous Dinosaur Sites in the New Jersey Coastal Plain

Parataxonomic classification of Late Cretaceous Dinosaur eggshells from India

Parataxonomic classification of Late Cretaceous Dinosaur eggshells from India

Late Cretaceous dinosaurs from the Blufftown Formation in western Georgia and eastern Alabama

Fragmentary bones and teeth of three Late Cretaceous dinosaur taxa occur along both sides of the Georgia-Alabama border, in the extreme southeastern Coastal Plain Province. The localities lie in the middle and upper Blufftown Formation, in nearshore marine deposits.Exogyrassp. and calcareous nannofossils give a late Santonian through mid-Campanian age range. Taxa determined are: Hadrosauridae, genus and species indeterminate; Ornithomimidae, genus and species indeterminate; andAlbertosaurus? sp.