Terminal Cretaceous Research Articles

The diversity of teleost fishes during the terminal Cretaceous and the consequences of the K/Pg boundary extinction event – CORRIGENDUM

The diversity of teleost fishes during the terminal Cretaceous and the consequences of the K/Pg boundary extinction event – CORRIGENDUM

The diversity of teleost fishes during the terminal Cretaceous and the consequences of the K/Pg boundary extinction event

Abstract The Late Cretaceous was a time of blossoming teleost diversification that came to a sudden restriction and partial termination during the extinction event at the Cretaceous–Paleogene (K/Pg) boundary. Among the dominant and diverse Late Cretaceous teleost groups prior to the K/Pg boundary event were certain pelagic Aulopiformes (e.g., Ichthyotringoidei and Enchodontoidei) and a large variety of basal Acanthomorpha whose relationships are difficult to determine. The skeletal record diminishes during the late Campanian and is low in the Maastrichtian and Paleocene, constituting the so-called ‘Patterson’s Gap’. Recent studies of fossil otoliths, however, have significantly increased the number of taxa recognised for this time inerval, but most of the putative extinct forms lack adequate calibration with otoliths found in situ in articulated skeletons. However, the otolith assemblages do confirm the presence of great morphological diversity among Aulopiformes and Acanthomorpha incertae sedis that became extinct at the K/Pg boundary. In the present review, we elucidate the effect of the K/Pg boundary from an otolith perspective and categorise extinct lineages and survivors. It is interesting to recognise that several of the surviving lineages are represented by groups that probably originated during the Late Cretaceous but were not particularly common up to the K/Pg boundary and began to expand rapidly and diversify during the early Paleogene. Such lineages probably took advantage to populate void ecospace that may have opened following the extirpation of previously dominant lineages. During the early Paleogene, the otolith record shows that the Ophidiiformes and perciforms s. lat. were the ones that diversified the most rapidly and became the most abundant, and in certain areas associated with the Gadiformes.

Vapor-Plume Deposits, K–Pg Boundary Outcrop in the Village of Armenia, Belize

Accretionary impact spherules, some as large as 3.1 cm in diameter, occur within a fine-grained carbonate layer (an impactoclastic calcisiltite), which lies atop the terminal Cretaceous (latest Maastrichtian) paleosol in an outcrop located at the village of Armenia in central Belize. This fine-grained layer is interpreted as the vapor plume deposit from the Chicxulub impact structure and is composed of pulverized and comminuted carbonate mixed with clay. The accretionary impact spherules were formed by the aggradation of the vapor plume’s fine solid particles during turbulent flight over a distance of about 520 km from Chicxulub’s southern rim. These impact spherules, which are remarkably well-preserved, exhibit a nucleus of either rock or glass and one to three concentric coatings of finely-comminuted carbonate target rock. Coatings on individual spherules are non-graded and display fine-scale components such as silt inclusions, crystal-filled radial fractures, and microconglomerate layers.

Triple oxygen isotopes in intertrappean fossil woods: Evidence of higher tropical rainfall during Deccan volcanism

Despite several attempts, the effects of volcanism and greenhouse gas emission on climate (e.g., rainfall) over India across the Cretaceous/Palaeogene Boundary (66.1 ± 0.01 Ma) remain a contentious issue. Inferences from conventional isotopic, palaeosol, floral analysis, and palaeoclimate models are contradictory ranging from much lower- to higher-than-today rainfall during this high CO2 atmosphere. To resolve this, robust tracer of triple oxygen isotopic ratios (ẟ18O-∆′17O) of silicified fossil woods from Deccan intertrappean lacustrine sediments, central India were analysed for retrieving the silicification temperature and ambient fluid (water) isotopic composition. Under certain assumptions and uncertainty, triple oxygen isotope data indicate that the fluids were derived from a mixture of meteoric and hydrothermal water. The meteoric water end member possibly had a low ẟ18OVSMOW value (∼− 12 ± 2‰) compared to the modern mean monsoon rainwater (∼− 5‰) which implies a substantially higher rainfall than today (∼1760 ± 200 to 1860 ± 200 mm/year) in the terminal Cretaceous India. This result supports the prediction of elevated precipitation by the recent new generation of global coupled models that consider various feedbacks and ocean dynamics, at a high CO2 atmosphere. It is also consistent with the paleo-botanical evidence but far exceeds the amount predicted by the older paleoclimate models pertaining to the Cretaceous period.

New age constraints support a K/Pg boundary interval on Vega Island, Antarctica: Implications for latest Cretaceous vertebrates and paleoenvironments

AbstractA second K/Pg boundary interval in the northern sector of the Antarctic Peninsula on Vega Island has been proposed, yet current temporal resolution of these strata prohibits direct testing of this hypothesis. To not only test for the existence of a K/Pg boundary on Vega Island but also provide increased age resolution for the associated vertebrate fauna (e.g., marine reptiles, non-avian dinosaurs, and avian dinosaurs), the Vega Island succession was intensively re-sampled. Stratigraphic investigation of the Cape Lamb Member of the Snow Hill Island Formation, and in particular, the overlying Sandwich Bluff Member of the López de Bertodano Formation, was conducted using biostratigraphy, strontium isotope stratigraphy, magnetostratigraphy, and detrital zircon geochronology. These data indicate a Late Campanian–early Maastrichtian age for the Cape Lamb Member and present three possible correlations to the global polarity time scale (GPTS) for the overlying Sandwich Bluff Member. The most plausible correlation, which is consistent with biostratigraphy, detrital zircon geochronology, sequence stratigraphy, and all but one of the Sr-isotope ages, correlates the base of the section to C31N and the top of the section with C29N, which indicates that the K/Pg boundary passes through the top of the unit. A second, less plausible option conflicts with the biostratigraphy and depends on a series of poorly defined magnetic reversals in the upper part of the stratigraphy that also correlates the section between C31N and C29R and again indicates an inclusive K/Pg boundary interval. The least likely correlation, which depends on favoring only a single Srisotope age at the top of the section over biostratigraphy, correlates the section between C31N and C30N and is inconsistent with an included K/Pg boundary interval. Although our preferred correlation is well supported, we failed to identify an Ir-anomaly, spherules/impact ejecta, or other direct evidence typically used to define the precise position of a K/Pg boundary on Vega Island. This study does, however, confirm that Vegavis, from the base of the Sandwich Bluff Member, is the oldest (69.2–68.4 Ma) phylogenetically placed representative of the avian crown clade, and that marine vertebrates and non-avian dinosaurs persisted in Antarctica up to the terminal Cretaceous.

Oriental freshwater mussels arose in East Gondwana and arrived to Asia on the Indian Plate and Burma Terrane

Freshwater mussels cannot spread through oceanic barriers and represent a suitable model to test the continental drift patterns. Here, we reconstruct the diversification of Oriental freshwater mussels (Unionidae) and revise their taxonomy. We show that the Indian Subcontinent harbors a rather taxonomically poor fauna, containing 25 freshwater mussel species from one subfamily (Parreysiinae). This subfamily most likely originated in East Gondwana in the Jurassic and its representatives arrived to Asia on two Gondwanan fragments (Indian Plate and Burma Terrane). We propose that the Burma Terrane was connected with the Indian Plate through the Greater India up to the terminal Cretaceous. Later on, during the entire Paleogene epoch, these blocks have served as isolated evolutionary hotspots for freshwater mussels. The Burma Terrane collided with mainland Asia in the Late Eocene, leading to the origin of the Mekong’s Indochinellini radiation. Our findings indicate that the Burma Terrane had played a major role as a Gondwanan “biotic ferry” alongside with the Indian Plate.

Calcareous dinoflagellate cyst distribution across the K/Pg boundary at DSDP site 577, Shatsky Rise, western North Pacific Ocean

An analysis of calcareous dinoflagellate cysts has been carried out on sixteen samples from across the K/Pg boundary interval from Deep Sea Drilling Project Site 577 situated on Shatsky Rise in the western North Pacific. This is the first time that a detailed study of this microfossil group has been undertaken from deep sea sediments of Late Cretaceous–early Paleocene age in the North Pacific realm. Eight species of calcareous dinoflagellate cysts were found to comprise low diversity assemblages of which half are representative of extant taxa. The most pronounced bioevent is that of Cervisiella operculata reaching its highest proportions at the K/Pg boundary transition underscoring the utility and cosmopolitan distribution of the species with its acme as a marker for the earliest Danian. We also identify an indirect sea surface paleotemperature signal as represented by variance in wall thickness in two distinct morphotypes of Thoracosphaera heimii (morphotypes A and B). The cyst concentrations and relative abundances of these taxa are interpreted to reflect the late Maastrichtian warming event and subsequent late Maastrichtian cooling phase prior to the interval of gradual warming in the early Danian marked by the opportunistic capitalization of Cervisiella operculata during a time of ocean recovery following the terminal Cretaceous.

The first <i>in situ</i> collection of a mosasaurine from the marine Breien Member of the Hell Creek Formation in south-central North Dakota, USA

The upper Maastrichtian Breien Member situated within the lower portion of the Hell Creek Formation in south-central North Dakota records one of the last transgressions of the Western Interior Seaway (WIS) during the terminal Cretaceous. A fragmentary articular-prearticular complex and isolated vertebra belonging to a mosasauroid were recovered in 2016 from sandstones and mudstones deposited in a nearshore marine paleoenvironment within the southern arm of the bisected WIS. The medially-rotated retroarticular process on the articular-prearticular complex, the shape of the glenoid fossa, along with the morphology of the isolated vertebra, facilitate a conservative referral to a large-bodied mosasaurine such as Mosasaurus or Prognathodon. The rocks of the Breien Member provide paleontologists a unique glimpse of intracontinental marine ecosystems immediately prior to the end of the Cretaceous Period. This discovery provides additional evidence that the latest Maastrichtian marine fauna is a continuation of the fauna preserved in the underlying Fox Hills Formation and that the marine faunal turnover that gave rise to the subsequent Cannonball Sea fauna recorded in Paleocene rocks in North Dakota occurred at the Cretaceous-Paleogene boundary.

Planktonic Foraminiferal Endemism at Southern High Latitudes Following the Terminal Cretaceous Extinction

AbstractAustral planktonic foraminiferal assemblages from immediately above the Cretaceous/Paleogene (K/Pg) boundary at Ocean Drilling Program Hole 690C (Maud Rise, Weddell Sea) and International Ocean Drilling Program Hole U1514C (southeast Indian Ocean) show a much different record of post-extinction recovery than anywhere outside the circum-Antarctic region. Species of Woodringina and Parvularugoglobigerina, genera with well-documented evolutionary successions within the early Danian P0 and Pα biozones at tropical/subtropical and mid-latitude localities, are absent from southern high latitude sequences. This study proposes new criteria for biostratigraphic correlation of the lowermost Danian Antarctic Paleocene AP0 and AP1 Zones using stratophenetic observations from Scanning Electron Microscope images of lower Danian planktonic foraminifera at deep-sea sites in the southern South Atlantic and southern Indian Ocean. The small but distinctive species Turborotalita nikolasi (Koutsoukos) is a highly reliable index species for the lowermost Danian as it consistently occurs immediately above the K/Pg boundary at multiple southern high latitude sites, which is consistent with its distribution at middle and low latitudes. Also useful for cross-latitude correlation is Parasubbotina neanika n. sp., which first appears within the lowermost Danian worldwide. The geographic distribution of the New Zealand species Antarcticella pauciloculata (Jenkins) and Zeauvigerina waiparaensis (Jenkins), as well as Eoglobigerina maudrisensis n. sp. from just above the K/Pg in the southern South Atlantic and southern Indian Ocean, helps define the extent of the Austral Biogeographic Province and provides evidence for marine communication via marine seaways across Antarctica. While An. pauciloculata was previously considered a benthic species, new stable isotope evidence demonstrates that it lived a planktonic mode of life. It is possible this species evolved from a benthic ancestor and that the benthic to planktonic transition occurred through an intermediate tychopelagic lifestyle at a time when calcareous plankton were less abundant as a result of the terminal Cretaceous mass extinction.

A high-resolution record of environmental changes from a Cretaceous-Paleogene section of Seymour Island, Antarctica

A high-resolution sedimentological and palynological study was performed in combination with biomarker-based organic geochemical temperature proxies TEX86 and MBT′/CBT, on a 7.4-m-thick continuous section straddling the Cretaceous-Paleogene (K-Pg) boundary at Seymour Island, at the northern tip of the Antarctic Peninsula. The K-Pg interval of the Seymour Island section was deposited in a deltaic/estuarine system with considerable sedimentary input from the erosion of a distant volcanic arc at the Antarctic Peninsula, combined with ash fallouts from explosive volcanic eruptions. The Maastrichtian interval represents the prodelta of a delta prograding in a marginal marine setting, whereas the Paleocene interval was deposited in more open, shallow marine conditions, following sea-level rise and shoal submergence above the K-Pg boundary. Dinocyst biostratigraphy indicates that in the studied section the K-Pg boundary is represented by a gentle erosive surface, 30 cm below a partially-indurated, marker sandstone bed. The dinoflagellate assemblages show quantitative changes across the boundary. Representatives of Manumiella group together with abundant Palambages dominate the assemblages in the lower part of the section, i. e. below the K-Pg boundary. There is an evident peak of Fibrocysta/Ifecysta/Cordosphaeridium just above the boundary. In the upper part of the section, Senegalinium reaches relatively high abundance together with Impletosphaeridium clavus. While relatively high concentrations of soil-derived organic matter inhibit the use of the TEX86 paleothermometer to reconstruct sea surface temperatures, the MBT′/CBT paleothermometer indicates warm mean annual air temperatures for the latest Cretaceous (16.0–16.5 °C). These high temperatures, coinciding with the lowest abundance of the high-latitude pollen taxon Nothofagidites, may reflect the terminal Cretaceous Deccan Traps-warming pulse. Fluctuating temperatures followed in the early Paleocene, characterized by ~2 degrees drop in air temperatures, coincident with the maximum percentage of the high-latitude angiosperm Nothofagidites spp. and the cold-water dinocyst taxon Impletosphaeridium clavus. The recognition of ecological signals of disturbances and their relationship with short-term climatic and environmental changes, provides new insights related to the effect of the impact at the high-latitude K-Pg boundary of Antarctica.

Diminutive fleet-footed tyrannosauroid narrows the 70-million-year gap in the North American fossil record

To date, eco-evolutionary dynamics in the ascent of tyrannosauroids to top predator roles have been obscured by a 70-million-year gap in the North American (NA) record. Here we report discovery of the oldest Cretaceous NA tyrannosauroid, extending the lineage by ~15 million years. The new taxon—Moros intrepidus gen. et sp. nov.—is represented by a hind limb from an individual nearing skeletal maturity at 6–7 years. With a ~1.2-m limb length and 78-kg mass, M. intrepidus ranks among the smallest Cretaceous tyrannosauroids, restricting the window for rapid mass increases preceding the appearance of colossal eutyrannosaurs. Phylogenetic affinity with Asian taxa supports transcontinental interchange as the means by which iconic biotas of the terminal Cretaceous were established in NA. The unexpectedly diminutive and highly cursorial bauplan of NA’s earliest Cretaceous tyrannosauroids reveals an evolutionary strategy reliant on speed and small size during their prolonged stint as marginal predators.

Diverse Plant-Insect Associations from the Latest Cretaceous and Early Paleocene of Patagonia, Argentina

. Little is known about the recovery of terrestrial ecosystems after the end-Cretaceous extinction outside of the Western Interior of North America, relatively close to the 66 Ma bolide impact crater in Chicxulub, Mexico. A previous report showed that in Patagonia, Argentina, insect damage on fossil leaves decreased from the latest Cretaceous to early Paleocene but recovered to pre-extinction levels within ca. four million years. Here, we present the first detailed study of these Patagonian plant-insect associations, key components of terrestrial food webs, during the latest Cretaceous and three time slices from the early Paleocene recovery. The lithologic units studied are the uppermost Cretaceous portion of the Lefipan Formation and the Danian Salamanca and Penas Coloradas formations in Chubut, Argentina. Seven functional feeding groups are present throughout: hole feeding, margin feeding, skeletonization, surface feeding, piercing and sucking, mining, and galling. Fifty damage types (DTs) were present at Maastrichtian localities, and 39–48 were found at Danian localities. Plant-insect associations that apparently went locally extinct at the end of the Cretaceous include several gall, mine, and piercingand-sucking DTs. Based on our preliminary leaf morphotypes, host plants did not provide refuge for specialized insect herbivores across the K/Pg boundary. Despite a decrease in insect damage diversity after the bolide impact, Danian floras hosted a rich array of DTs, including specialized damage such as mines and galls. Many of these early Paleocene DTs were not found in the terminal Cretaceous, providing evidence for a rapid recovery of plant-insect associations regionally.

The fossil flip-leaves (Retrophyllum, Podocarpaceae) of southern South America.

The flip-leaved podocarp Retrophyllum has a disjunct extant distribution in South American and Australasian tropical rainforests and a Gondwanic fossil record since the Eocene. Evolutionary, biogeographic, and paleoecological insights from previously described fossils are limited because they preserve little foliar variation and no reproductive structures. We investigated new Retrophyllum material from the terminal Cretaceous Lefipán, the early Eocene Laguna del Hunco, and the early/middle Eocene Río Pichileufú floras of Patagonian Argentina. We also reviewed type material of historical Eocene fossils from southern Chile. Cretaceous Retrophyllum superstes sp. nov. is described from a leafy twig, while Eocene R. spiralifolium sp. nov. includes several foliage forms and a peduncle with 13 pollen cones. Both species preserve extensive damage from sap-feeding insects associated with foliar transfusion tissue. The Eocene species exhibits a suite of characters linking it to both Neotropical and West Pacific Retrophyllum, along with several novel features. Retrophyllum araucoensis (Berry) comb. nov. stabilizes the nomenclature for the Chilean fossils. Retrophyllum is considerably older than previously thought and is a survivor of the end-Cretaceous extinction. Much of the characteristic foliar variation and pollen-cone morphology of the genus evolved by the early Eocene. The mixed biogeographic signal of R. spiralifolium supports vicariance and represents a rare Neotropical connection for terminal-Gondwanan Patagonia, which is predominantly linked to extant Australasian floras due to South American extinctions. The leaf morphology of the fossils suggests significant drought vulnerability as in living Retrophyllum, indicating humid paleoenvironments.

Triggering of the largest Deccan eruptions by the Chicxulub impact: Comment

The environmental crisis responsible for the terminal Cretaceous extinctions has been linked with either episodes of Deccan volcanism or the Chicxulub impact (see Bhandari et al., 1996; Keller et al., 2009; Schulte et al., 2010; Schoene et al., 2015). Richards et al. (2015) proposed a connection between the two events and suggested that there was a change in the Deccan magmatic system as a result of the impact that occurred on the other side of Earth (more than 13,000 km away). They suggested that the seismic waves resulting from the Chicxulub impact could have affected the magmatic system responsible for Deccan volcanism.

A new mawsoniid coelacanth (Actinistia) from the Upper Cretaceous of Southern France

Axelrodichthys megadromos sp. nov. is a coelacanth described based on a single specimen collected in the lower Campanian site of Ventabren motorway, Southern France. The new species is referred to the mawsoniids because of the ornamentation of the skull roof and of the proportionally wide supraorbital series. The specimen belongs to the Mawsonia-Axelrodichthys complex based on features present on the lower jaw and on the basisphenoid. The new species is referred to the genus Axelrodichthys because of proportions of its parietonasal shield and because of the arrangement of the posterior parietals relative to the supraorbitals. Autapomorphic characters, in particular on the parasphenoid, justify the inclusion of the specimen in a new species. The occurrence of a mawsoniid in the Ibero-Amorican Island that formed part of the European Archipelago in the terminal Cretaceous is an evidence of a dispersal event from the southern land masses. The occurrence of A. megadromos in the Campanian-Maastrichtian represents the last occurrence of mawsoniids worldwide, after a gap in the fossil record of about 30 million years. This belated occurrence of Axelrodichthys extends the time range of this genus to approximately 40myr and suggests that this genus, together with its sister genus Mawsonia, were organisms with a slow morphologic evolution.

A Mummified Duck-Billed Dinosaur with a Soft-Tissue Cock’s Comb

Among living vertebrates, soft tissues are responsible for labile appendages (combs, wattles, proboscides) that are critical for activities ranging from locomotion to sexual display [1]. However, soft tissues rarely fossilize, and such soft-tissue appendages are unknown for many extinct taxa, including dinosaurs. Here we report a remarkable "mummified" specimen of the hadrosaurid dinosaur Edmontosaurus regalis from the latest Cretaceous Wapiti Formation, Alberta, Canada, that preserves a three-dimensional cranial crest (or "comb") composed entirely of soft tissue. Previously, crest function has centered on the hypertrophied nasal passages of lambeosaurine hadrosaurids, which acted as resonance chambers during vocalization [2-4]. The fleshy comb in Edmontosaurus necessitates an alternative explanation most likely related to either social signaling or sexual selection [5-7]. This discovery provides the first view of bizarre, soft-tissue signaling structures in a dinosaur and provides additional evidence for social behavior. Crest evolution within Hadrosaurinae apparently culminated in the secondary loss of the bony crest at the terminal Cretaceous; however, the new specimen indicates that cranial ornamentation was in fact not lost but substituted in Edmontosaurus by a fleshy display structure. It also implies that visual display played a key role in the evolution of hadrosaurine crests and raises the possibility of similar soft-tissue structures among other dinosaurs.

Theropod teeth from the upper Maastrichtian Hell Creek Formation “Sue” Quarry: New morphotypes and faunal comparisons

Isolated teeth from vertebrate microfossil localities often provide unique information on the biodiversity of ancient ecosystems that might otherwise remain unrecognized. Microfossil sampling is a particularly valuable tool for documenting taxa that are poorly represented in macrofossil surveys due to small body size, fragile skeletal structure, or relatively low ecosystem abundance. Because biodiversity patterns in the late Maastrichtian of North American are the primary data for a broad array of studies regarding non-avian dinosaur extinction in the terminal Cretaceous, intensive sampling on multiple scales is critical to understanding the nature of this event. We address theropod biodiversity in the Maastrichtian by examining teeth collected from the Hell Creek Formation locality that yielded FMNH PR 2081 (the Tyrannosaurus rex specimen “Sue”). Eight morphotypes (three previously undocumented) are identified in the sample, representing Tyrannosauridae, Dromaeosauridae, Troodontidae, and Avialae. Notice...

The 3d relief models and structure of the Earth’s upper crust in the Amur region

The analysis of 3D relief models of the lower Amur region and several adjacent areas suggested that the structure of the region is related to the horizontal tectonic layering of the upper part of the Amur plate. When it was dislocated to the northwest at the terminal Cretaceous, some fragments of the upper layers were displaced not strictly synchronously but with some lag relative to the whole plate. This scenario was responsible for the formation of the main morphostructural elements of the region: river valleys, mountain ranges, and graben series. These inferences are supported by field observations and some geological data. The proposed hypothesis can also be applied for several other regions.

Factors responsible for catastrophic extinction of marine organisms at the Mesozoic-Cenozoic boundary

The mass death of organisms at the Cretaceous-Tertiary boundary (KT boundary) resulted in the extinction of approximately half of marine genera. Some taxa had degraded by the end of the Cretaceous to become eventually extinct either before or precisely at the KT boundary. Most of them became extinct imme� diately at this boundary. The terminal Cretaceous was marked by changes in many environmental processes, which influenced the biota. These included tectonic events, powerful basalt eruptions, falls of large asteroids (impact events), anoxia, transgressions and regressions, cooling and warming episodes, and the chemistry of the atmosphere and seawater. All these factors, except for impact events, could stimulate degradation of some groups of organisms, not their extinction. The Cretaceous-Tertiary boundary was marked by major impact events, which are reflected in the occurrence of the Chicxulub, Shiva, Boltysh, Silverpit, and, probably some other impact craters. Some known craters were left by asteroids at that time or slightly earlier. At least as many asteroids undoubtedly fell into the ocean. The combination of many factors in the terminal Cretaceous harm� ful for organisms and seemingly unrelated to each other may be likely explained only by a single supreme cause beyond the Solar System.

Cretaceous Extinctions: Multiple Causes

![Figure][1] Deccan plateau basalts. Lava from Deccan volcanism formed distinct layering. CREDIT: GSFC/NASA In the Review “The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene boundary” (P. Schulte et al. , 5 March, p. [1214][2]), the terminal Cretaceous