Diversity of turtles across the cretaceous/tertiary boundary in Northeastern Montana

The abundant chelonian faunas of the Hell Creek and Tullock formations of McCone and Garfield counties, Montana, span the Cretaceous/Tertiary boundary and provide a basis for assessing extinction and changes in diversity. Over three thousand specimens were counted on a modified minimum number basis from 510 localities. The Lancian (Maastrichtian) part of the Hell Creek Formation contains at least 19 genera and subgenera of turtles and probably a greater but undetermined number of species and comprises the most diverse fossil turtle fauna known from a single rock unit. At least 15 generic level taxa survive into the Puercan (early Paleocene) part of the overlying Tullock Formation and only one new genus appears. The magnitude of the change in diversity across the Cretaceous/Tertiary boundary is less than or compaable to examples within the Tertiary and is readily explained by moderate ecological changes.     

Fruits of icacinaceae (tribe iodeae) from the late paleocene of Western north america

The Icacinaceae occur pantropically today, but are well represented by fossil fruits of the warm Early Middle Eocene, when tropical plants that currently occupy low latitudes were more widely distributed in higher latitudes. Members of this family are first known in the Late Cretaceous; however, fossil fruits of tribe Iodeae are quite rare before the Eocene. In this paper we describe the first formally recognized Late Paleocene icacinaceous taxa from western North America. We name two new species of Icacinicarya based on anatomically preserved fruits and establish a new genus, Icacinicaryites, for impressions with a strong similarity to Icacinicarya that lack anatomical preservation. These new records from the Almont/Beicegel Creek flora in North Dakota and several localities in Wyoming, Colorado, and Montana complement records known from the Early Eocene of England and document an increased diversity of Iodeae and related forms in the Paleogene of western North America.     

A NEW SPECIES OF ISCHYODUS (CHONDRICHTHYES: HOLOCEPHALI: CALLORHYNCHIDAE) FROM UPPER MAASTRICHTIAN SHALLOW MARINE FACIES OF THE FOX HILLS AND HELL CREEK FORMATIONS, WILLISTON BASIN, NORTH DAKOTA, USA

Abstract:  A new species of chimaeroid, Ischyodus rayhaasi sp. nov., is described based primarily upon the number and configuration of tritors on palatine and mandibular tooth plates. This new species is named in honour of Mr Raymond Haas. Fossils of I. rayhaasi have been recovered from the Upper Maastrichtian Fox Hills Formation and the Breien Member and an unnamed member of the Hell Creek Formation at sites in south-central North Dakota and north-central South Dakota, USA. Ischyodus rayhaasi inhabited shallow marine waters in the central part of the Western Interior Seaway during the latest Cretaceous. Apparently it was also present in similar habitats at that time in the Volga region of Russia. Ischyodus rayhaasi is the youngest Cretaceous species of Ischyodus known to exist before the Cretaceous/Tertiary extinction, and the species apparently did not survive that event. It was replaced by Ischyodus dolloi , which is found in the Paleocene Cannonball Formation of the Williston Basin region of North Dakota and is widely distributed elsewhere.     

Unexpected resilience of species with temperature-dependent sex determination at the Cretaceous-Palaeogene boundary

It has been suggested that climate change at the Cretaceous-Palaeogene (K-Pg) boundary, initiated by a bolide impact or volcanic eruptions, caused species with temperature-dependent sex determination (TSD), including dinosaurs, to go extinct because of a skewed sex ratio towards all males. To test this hypothesis, the sex-determining mechanisms (SDMs) of Cretaceous tetrapods of the Hell Creek Formation (Montana, USA) were inferred using parsimony optimizations of SDMs on a tree, including Hell Creek species and their extant relatives. Although the SDMs of non-avian dinosaurs could not be inferred, we were able to determine the SDMs of 62 species; 46 had genotypic sex determination (GSD) and 16 had TSD. The TSD hypothesis for extinctions performed poorly, predicting between 32 and 34 per cent of survivals and extinctions. Most surprisingly, of the 16 species with TSD, 14 of them survived into the Early Palaeocene. In contrast, 61 per cent of species with GSD went extinct. Possible explanations include minimal climate change at the K-Pg, or if climate change did occur, TSD species that survived had egg-laying behaviour that prevented the skewing of sex ratios, or had a sex ratio skewed towards female rather than male preponderance. Application of molecular clocks may allow the SDMs of non-avian dinosaurs to be inferred, which would be an important test of the pattern discovered here.     

Mammalian Faunal Dynamics During the Last 1.8 Million Years of the Cretaceous in Garfield County, Montana

This study provides an analysis of biotic change in successive mammalian communities during the last 1.8 million years of the Cretaceous (67.3–65.58 Ma) from the Hell Creek Formation in Garfield County, Montana. Results show changes in relative abundances of species, mean individual body size, and to some extent taxonomic composition through the Hell Creek Formation. These results are interpreted as “normal” mammalian responses to fluctuating temperatures during the latest Cretaceous. By contrast, the extinction of 22–27 mammalian species at or near the Cretaceous-Tertiary (K-T) boundary cannot be explained by the coincident cooling interval alone. At the scale of temporal resolution available, these fossil data are inconsistent with an extended gradual pattern of extinction (linear-response) and are most consistent with either a non-linear response pattern for the K-T extinction, resulting from the accumulated stress of multiple long- and short-term environmental perturbations (e.g., climate change, sea-level regression, volcanism, an extraterrestrial impact), or a single, short-term cause (an extraterrestrial impact).     

Proteaceae Leaf Fossils: Phylogeny,Diversity, Ecology and Austral Distributions

Foliar fossils of Proteaceae are reviewed, and useful specimens for interpreting evolution, and past and present distributions and environments are discussed. There are no definite Cretaceous occurrences. However, there is evidence of extant lineages dating from the Paleocene onwards, including tribe Persoonieae of subfamily Persoonioideae and each of the four tribes of subfamily Grevilleoideae. High diversity and abundance characterizes the Australian fossil record, including sclerophyllous and xeromorphic forms, but there is little evidence of the prominent extant subfamily Proteoideae. New Zealand had a much higher diversity of Proteaceae than at present, including Oligo-Miocene species of open vegetation. The South American leaf fossil record is not extensive. However, the fossil records of Embothrieae and Orites are consistent with the distributions of their extant relatives in South America and Australia being the result of vicariance. Overall, there is a need for more research on placing Proteaceae leaf fossils in a phylogenetic context.     

Evidence of plant–insect interaction in the Early Cretaceous Flora from the Crato Formation,Araripe Basin,Northeast Brazil

The analysis of insect-plant interaction can be provide paleoecological and paleoenvironmental important data for understanding the co-evolution between plants and insects. Since the appearance of the first evidence of leaves damaged by insects, these organisms have evolved together. In the Araripe Basin, the Crato Formation stands out by having abundance and diversity of fossils species of plants and insects. In this work they are documented interaction records in specimens of ferns, gymnosperms and angiosperms, showing a wide variety of types of interactions. Here we analyze 56 fossil specimens from the collections of the Museum of Paleontology and the Laboratory of Paleontology of the Universidade Regional do Cariri. The types of damage identified in this study is insect galls, leaf margin feeding (herbivory), leaf mines, oviposition of insects and skeletonization, which are present in 19 specimens. This analysis in search for evidences of plant–insect interaction contributes with new interaction patterns for the Crato Formation. Although the low sample rate, the new registers for plant-insect association were compared to records from different cretaceous basins. This suggests new possibilities in the studies for ecological relations and coevolutionary plant-insect during the Cretaceous. In addition, a new type of damage is identified in a pteridophyte.     

A New Large-Bodied Oviraptorosaurian Theropod Dinosaur from the Latest Cretaceous of Western North America

The oviraptorosaurian theropod dinosaur clade Caenagnathidae has long been enigmatic due to the incomplete nature of nearly all described fossils. Here we describe Anzu wyliei gen. et sp. nov., a new taxon of large-bodied caenagnathid based primarily on three well-preserved partial skeletons. The specimens were recovered from the uppermost Cretaceous (upper Maastrichtian) Hell Creek Formation of North and South Dakota, and are therefore among the stratigraphically youngest known oviraptorosaurian remains. Collectively, the fossils include elements from most regions of the skeleton, providing a wealth of information on the osteology and evolutionary relationships of Caenagnathidae. Phylogenetic analysis reaffirms caenagnathid monophyly, and indicates that Anzu is most closely related to Caenagnathus collinsi, a taxon that is definitively known only from a mandible from the Campanian Dinosaur Park Formation of Alberta. The problematic oviraptorosaurs Microvenator and Gigantoraptor are recovered as basal caenagnathids, as has previously been suggested. Anzu and other caenagnathids may have favored well-watered floodplain settings over channel margins, and were probably ecological generalists that fed upon vegetation, small animals, and perhaps eggs.     

江汉盆地渔洋组上部的古新世孢粉组合

20世纪70至80年代,几乎所有关于江汉盆地跑马岗组和渔洋组的古生物文献都将其时代确定为晚白垩世。李伟同在深入地研究了跑马岗组标准剖面上的轮藻化石后提出跑马岗组大部分属于古新统。取自层位与跑马岗组相当的渔洋组上段上部的岩芯样品经分析后获得了丰富的孢粉化石。这一组合总的面貌与王大宁等获得的晚白垩世渔洋组的第三组合区别明显,而与古近纪的新沟嘴组的第四组合相似处很多。在该孢粉植物群中,常见于当地的晚白垩世分子,如希指蕨孢属、克拉梭粉属、江汉粉属、刺参粉属、鹰粉属等没有或极少见到。而在本组合常见的南岭粉属、五边粉属、漆树粉属等多出现在我国南方古新世地层中。因此,其时代很有可能为古新世。如果是这样,渔洋组上部有可能跨越了白垩系和古近系界线。从当前孢粉植物群含有很多亚热带成分以及麻黄粉属以及胡颓子粉属、忍冬粉属等看,它反映了江汉盆地当时偏干旱的亚热带气候。     

Mine and gall predation as top down regulation in the plant–insect systems from the Cretaceous of Negev, Israel

Fossil evidence of predation on leaf mines and galls opens the way to analyzing regulatory circuits in plant–insect interaction systems and assessing their evolutionary advancement. In the Cretaceous (mid-Turonian) flora of Negev, Israel, predation traces vary from the entire gall or mine excisions to minute punctures and slits over the mine tracks. Bite marks on the borders of predation holes representing different mouthpart morphologies may show how diverse the predators were. The efficiency of predation as a top down regulation force is attested on the basis of the gall and mine abundance, gall morphologies, mine configurations, co-occurrence of different mine types on leaves, and temporary mining. In turn, the regulation efficiency is considered as a criterion of evolutionary advancement of the plant–insect community as a whole. It is suggested that the coeval Cretaceous coastal and inland communities differed in the relative significance of top-down regulation.     

A new kinosternoid from the Late Cretaceous Hell Creek Formation of North Dakota and Montana and the origin of the <Emphasis Type="Italic">Dermatemys mawii</Emphasis> lineage

A nearly complete turtle shell from the Late Cretaceous (Maastrichtian) Hell Creek Formation of Slope County, North Dakota, represents the most complete remains to date of a Mesozoic kinosternoid turtle and a new species, Hoplochelys clark nov. sp. The new taxon is diagnosable from other representatives of Hoplochelys by the plesiomorphic placement of the humeral/femoral sulcus behind the hyo/hypoplastral suture and the autapomorphic development of an interrupted median (neural) keel. All six previously named Paleocene (Puercan and Torrejonian) representatives of Hoplochelys lack diagnostic characters and are synonymized as Hoplochelys crassa. A phylogenetic analysis reveals that Hoplochelys spp. and Agomphus pectoralis are most parsimoniously placed within Kinosternoidea along the phylogenetic stem of the extant Mesoamerican River Turtle Dermatemys mawii, extending that taxon’s stem lineage from the early Eocene to the late Maastrichtian. The two primary crown lineages of Kinosternoidea are thus known from the Mesozoic and split prior to the late Campanian. The presence of a thickened cruciform plastron, true costiform processes, only three inframarginals, and the reduction of the medial contact of the abdominals are synapomorphies of Chelydroidea, the clade formed by Chelydridae and Kinosternoidae.     

Multiple lineages of lice pass through the K-Pg boundary

For modern lineages of birds and mammals, few fossils have been found that predate the Cretaceous-Palaeogene (K-Pg) boundary. However, molecular studies using fossil calibrations have shown that many of these lineages existed at that time. Both birds and mammals are parasitized by obligate ectoparasitic lice (Insecta: Phthiraptera), which have shared a long coevolutionary history with their hosts. Evaluating whether many lineages of lice passed through the K-Pg boundary would provide insight into the radiation of their hosts. Using molecular dating techniques, we demonstrate that the major louse suborders began to radiate before the K-Pg boundary. These data lend support to a Cretaceous diversification of many modern bird and mammal lineages.     

No post-Cretaceous ecosystem depression in European forests? Rich insect-feeding damage on diverse middle Palaeocene plants,Menat, France

Insect herbivores are considered vulnerable to extinctions of their plant hosts. Previous studies of insect-damaged fossil leaves in the US Western Interior showed major plant and insect herbivore extinction at the Cretaceous–Palaeogene (K–T) boundary. Further, the regional plant–insect system remained depressed or ecologically unbalanced throughout the Palaeocene. Whereas Cretaceous floras had high plant and insect-feeding diversity, all Palaeocene assemblages to date had low richness of plants, insect feeding or both. Here, we use leaf fossils from the middle Palaeocene Menat site, France, which has the oldest well-preserved leaf assemblage from the Palaeocene of Europe, to test the generality of the observed Palaeocene US pattern. Surprisingly, Menat combines high floral diversity with high insect activity, making it the first observation of a ‘healthy’ Palaeocene plant–insect system. Furthermore, rich and abundant leaf mines across plant species indicate well-developed host specialization. The diversity and complexity of plant–insect interactions at Menat suggest that the net effects of the K–T extinction were less at this greater distance from the Chicxulub, Mexico, impact site. Along with the available data from other regions, our results show that the end-Cretaceous event did not cause a uniform, long-lasting depression of global terrestrial ecosystems. Rather, it gave rise to varying regional patterns of ecological collapse and recovery that appear to have been strongly influenced by distance from the Chicxulub structure.     

IN SITU CERCIDIPHYLLUM-LIKE SEEDLINGS FROM THE PALEOCENE OF ALBERTA,CANADA

Fossil seedlings and seeds of an extinct Cercidiphyllum-like plant occur in the Paskapoo Formation (Late Paleocene) at Joffre Bridge near Red Deer, Alberta. Cotyledon and early seedling leaf stages are preserved in growth position. Morphological details of seedlings and seeds support a close relationship between the Paleocene fossils and extant Cercidiphyllum, and suggest that during the Upper Cretaceous and Tertiary (Paleogene) Cercidiphyllum-like plants were important early colonizers of open flood-plain environments.     

Mineralized soft-tissue structure and chemistry in a mummified hadrosaur from the Hell Creek Formation,North Dakota (USA)

An extremely well-preserved dinosaur (Cf. Edmontosaurus sp.) found in the Hell Creek Formation (Upper Cretaceous, North Dakota) retains soft-tissue replacement structures and associated organic compounds. Mineral cements precipitated in the skin apparently follow original cell boundaries, partially preserving epidermis microstructure. Infrared and electron microprobe images of ossified tendon clearly show preserved mineral zonation, with silica and trapped carbon dioxide forming thin linings on Haversian canals within apatite. Furthermore, Fourier transform infrared spectroscopy (FTIR) of materials recovered from the skin and terminal ungual phalanx suggests the presence of compounds containing amide groups. Amino acid composition analyses of the mineralized skin envelope clearly differ from the surrounding matrix; however, intact proteins could not be obtained using protein mass spectrometry. The presence of endogenously derived organics from the skin was further demonstrated by pyrolysis gas chromatography mass spectrometry (Py-GCMS), indicating survival and presence of macromolecules that were in part aliphatic (see the electronic supplementary material).     

Obituary: Ron K. Pickerill (1947–2018)

Recently discovered tracks in alluvial sediments of the Late Paleocene Bullion Creek Formation of western North Dakota have been identified as belonging to the large eusuchian crocodile Borealosuchus formidabilis and an associated small arthropod. They are described as two new ichnotaxa. The first of these, Borealosuchipus hanksi igen. et isp. nov., is based on a partly complete trackway having fore- and hind-footprints as well as body marks preserved in hyporelief. These tracks are directly associated with numerous body fossils including articulated bones which provide strong implications for their probable origin. The second specimen, Koupichnium pentapodus isp. nov., is founded on a trackway of a small invertebrate in which a series of five pairs of footprints are arranged along a midline drag mark which is continuous throughout the length of its trackway. This trackway shares features with other fossils as well as living arthropod trackways in which four small feet and a larger posterior hind “pusher” foot are present. The two described new ichnotaxa represent the first recognized tracks from the Wannagan Creek local fauna.     

Dinosaur census reveals abundant Tyrannosaurus and rare ontogenetic stages in the Upper Cretaceous Hell Creek Formation (Maastrichtian), Montana, USA

Background

A dinosaur census recorded during the Hell Creek Project (1999–2009) incorporates multiple lines of evidence from geography, taphohistory, stratigraphy, phylogeny and ontogeny to investigate the relative abundance of large dinosaurs preserved in the Upper Cretaceous Hell Creek Formation of northeastern Montana, USA. Overall, the dinosaur skeletal assemblages in the Hell Creek Formation (excluding lag-influenced records) consist primarily of subadult or small adult size individuals. Small juveniles and large adults are both extremely rare, whereas subadult individuals are relatively common. We propose that mature individuals of at least some dinosaur taxa either lived in a separate geographic locale analogous to younger individuals inhabiting an upland environment where sedimentation rates were relatively less, or these taxa experienced high mortality before reaching terminal size where late stage and often extreme cranial morphology is expressed.

Methodology/Principal Findings

Tyrannosaurus skeletons are as abundant as Edmontosaurus, an herbivore, in the upper Hell Creek Formation and nearly twice as common in the lower third of the formation. Smaller, predatory dinosaurs (e.g., Troodon and dromaeosaurids) are primarily represented by teeth found in microvertebrate localities and their skeletons or identifiable lag specimens were conspicuously absent. This relative abundance suggests Tyrannosaurus was not a typical predator and likely benefited from much wider food choice opportunities than exclusively live prey and/or specific taxa. Tyrannosaurus adults may not have competed with Tyrannosaurus juveniles if the potential for selecting carrion increased with size during ontogeny.

Conclusions/Significance

Triceratops is the most common dinosaur and isolated skulls contribute to a significant portion of this census. Associated specimens of Triceratops consisting of both cranial and postcranial elements remain relatively rare. This rarity may be explained by a historical collecting bias influenced by facies and taphonomic factors. The limited discovery of postcranial elements may also depend on how extensive a fossil quarry is expanded after a skull is collected.     

Evidence of temporary mining in the Cretaceous fossil mine assemblage of Negev, Israel

Temporary mining is a peculiar behavioral trait in leaf parasites requiring adaptations of consecutive larval stages to the endophytic and ectophytic life. The first fossil evidence for the origin of the trait comes from the Cretaceous (Turonian) plant–insect locality of the Negev Desert containing rich trace assemblages of leaf parasites, including blotch mines with leaf pieces cut out for case construction, as well as attached larval cases. The host plants are deciduous broadleafs or aquatic angiosperms with emergent leaves, suggesting that initial acquisition of the habit might have been related to leaf abscission and the risk for the larva being chocked in the mine during floods. Unlike tracks of permanent miners, temporary mines never co‐occur on leaves with other type mines, which attests to their effect of enhancing plant resistance. Mine predation appears to have been widespread in the Cretaceous biotic community, suggesting a possibility of top‐down regulation of mining habits at this early stage of their evolutionary development.     

Early penguin fossils, plus mitochondrial genomes, calibrate avian evolution

Testing models of macroevolution, and especially the sufficiency of microevolutionary processes, requires good collaboration between molecular biologists and paleontologists. We report such a test for events around the Late Cretaceous by describing the earliest penguin fossils, analyzing complete mitochondrial genomes from an albatross, a petrel, and a loon, and describe the gradual decline of pterosaurs at the same time modern birds radiate. The penguin fossils comprise four naturally associated skeletons from the New Zealand Waipara Greensand, a Paleocene (early Tertiary) formation just above a well-known Cretaceous/Tertiary boundary site. The fossils, in a new genus (Waimanu), provide a lower estimate of 61-62 Ma for the divergence between penguins and other birds and thus establish a reliable calibration point for avian evolution. Combining fossil calibration points, DNA sequences, maximum likelihood, and Bayesian analysis, the penguin calibrations imply a radiation of modern (crown group) birds in the Late Cretaceous. This includes a conservative estimate that modern sea and shorebird lineages diverged at least by the Late Cretaceous about 74 +/- 3 Ma (Campanian). It is clear that modern birds from at least the latest Cretaceous lived at the same time as archaic birds including Hesperornis, Ichthyornis, and the diverse Enantiornithiformes. Pterosaurs, which also coexisted with early crown birds, show notable changes through the Late Cretaceous. There was a decrease in taxonomic diversity, and small- to medium-sized species disappeared well before the end of the Cretaceous. A simple reading of the fossil record might suggest competitive interactions with birds, but much more needs to be understood about pterosaur life histories. Additional fossils and molecular data are still required to help understand the role of biotic interactions in the evolution of Late Cretaceous birds and thus to test that the mechanisms of microevolution are sufficient to explain macroevolution.     

Cretaceous/Paleogene Floral Turnover in Patagonia: Drop in Diversity,Low Extinction,and a Classopollis Spike

Nearly all data regarding land-plant turnover across the Cretaceous/Paleogene boundary come from western North America, relatively close to the Chicxulub, Mexico impact site. Here, we present a palynological analysis of a section in Patagonia that shows a marked fall in diversity and abundance of nearly all plant groups across the K/Pg interval. Minimum diversity occurs during the earliest Danian, but only a few palynomorphs show true extinctions. The low extinction rate is similar to previous observations from New Zealand. The differing responses between the Southern and Northern hemispheres could be related to the attenuation of damage with increased distance from the impact site, to hemispheric differences in extinction severity, or to both effects. Legacy effects of the terminal Cretaceous event also provide a plausible, partial explanation for the fact that Paleocene and Eocene macrofloras from Patagonia are among the most diverse known globally. Also of great interest, earliest Danian assemblages are dominated by the gymnosperm palynomorphs Classopollis of the extinct Mesozoic conifer family Cheirolepidiaceae. The expansion of Classopollis after the boundary in Patagonia is another example of typically Mesozoic plant lineages surviving into the Cenozoic in southern Gondwanan areas, and this greatly supports previous hypotheses of high latitude southern regions as biodiversity refugia during the end-Cretaceous global crisis.