A New Small Pterosaur From Late Cretaceous North America

As the Cretaceous fossil record enters its final two stages - the Campanian and Maastrichtian - several unusual things seem to happen in the world of flying reptiles. Firstly, we see the end result of a steady drop off in pterosaur diversity leaving only azhdarchids - those often long-necked, long faced animals that we cover here with some regularity - with a strong, widespread fossil record. It's known that nyctosaurids and (thanks to recent discoveries) perhaps pteranodontids survived until the very end of the Mesozoic in at least two locations, but azhdarchids are globally distributed and dominate the pterosaur fossil record at this time. The overwhelming precedence of azhdarchids in the Late Cretaceous is an anomaly: at no other point in the pterosaur fossil record does one clade feature so prominently.

Secondly, Campanian and Maastrichtian pterosaurs are, without exception, pretty big animals. Many species from this time are renowned for their gigantic size: it's these stages which give us the famous 10 m wingspan, 250 kg colossi like Quetzalcoatlus, Arambourgiania and Hatzegopteryx, as well as a number of other giant azhdarchids which are too poorly known for generic titles. Coinciding with the evolution of the giants is a loss of small pterosaur taxa - those animals less than 2.5 m across the wings which are present, more-or-less, throughout the rest of pterosaur history. This shift in body size is sometimes interpreted as pterosaurs demonstrating 'Cope's Rule', the somewhat controversial proposal that species evolve towards large body size over time (Hone and Benton 2007; Benson et al. 2014). It's argued by some that competition from birds may be the driver behind this trend, as early avians fought small flying reptiles for ecological space and ultimately forced pterosaurs into larger sizes (e.g. Benson et al. 2014). Note that this concept is not without its detractors, including myself - I won't go into my reasons now but I plan to outline them here eventually.

Whether you agree with the bird-pterosaur competitive displacement hypothesis or not, we can't disagree that the end of the Cretaceous is almost entirely devoid of small pterosaur remains. Only a handful of specimens record small pterosaurs in the Campanian and Maastrichtian, and they're all tricky to work with. Aside from being highly fragmentary, some are controversially identified (such as Piksi barbarulna, an alleged small pterosaur from the Two Medicine Formation - see Agnolin and Varricho 2012 for the pro-pterosaur case) and others represent probable juvenile individuals (Godfrey and Currie 2005). Whatever it signifies, the lack of diminutive pterosaur specimens from the close of the Mesozoic is a real phenomenon of our fossil record, and any new specimen of a small, latest Cretaceous flying reptile has to be something to get excited about.

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Murusraptor barrosaensis: a new megaraptorid Theropod From Cretaceous Argentina

A new species of megaraptorid dinosaur discovered in Patagonia may help discern the evolutionary origins of the megaraptorid clade, according to a study published July 20, 2016 in the open-access journal PLOS ONE by Rodolfo Coria from the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina, and Phillip Currie from the University of Alberta, Canada.

The Patagonian region of Argentina has previously proven to be rich in fossils from the Late Cretaceous epoch, including a number of megaraptorids, a clade whose carnivorous diet gave rise to their name meaning 'giant thieves'. These medium-sized theropod dinosaurs, including South American genera Megaraptor, Orkoraptor, and Aerosteon as well as genera from Australia and Japan, have characteristically large claws and air-filled, birdlike bones.

The fossilized partial skeleton of a megaraptorid dinosaur analyzed in this study was discovered in Sierra Barrosa, in northwest Patagonia and represents one of the most complete megaraptorids found, with an unusually intact braincase. With unique skull features, the dinosaur, which they named Murusraptor barrosaensis, is a new species in the megaraptorid clade. This specimen appears to be immature, but the authors suggest that the species is larger and slenderer than Megaraptor and comparable in size with Aerosteon and Orkoraptor. While sharing many features with the other species, Musuraptor has distinctive facial features not previously seen amongst megaraptorids, as well as unusually shaped hip bones.

While phylogenetic analysis could not clearly determine evolutionary relationships, the authors note that these fossils provide new anatomical information which might help to resolve current debates as to whether the megaraptorids are a clade of the allosauroid or the coelurosaurid theropods.

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Mercury Increased in Three Different Spikes From Deccan Traps Across the K-T/K-Pg Boundary

Mercury enrichment and Hg isotopes in Cretaceous–Paleogene boundary successions: Links to volcanism and palaeoenvironmental impacts

Authors:

Sial et al

Abstract:

We investigate the use of Hg as a proxy for volcanism by studying four distal and two proximal sections in relation to the Deccan volcanic center, straddling the Cretaceous–Paleogene (KPg) boundary at (a) Højerup (Denmark), Bottaccione and Padriciano (Italy), (b) Meghalaya and Jhilmili (India), and (c) Bajada del Jagüel (Argentina). Hg sequestration by organic matter results in constant Hg/TOC ratio and linear correlation between Hg content of the sediments and total organic carbon (TOC).

Elevated Hg concentrations that deviate from this linear relationship represent most likely true Hg anomalies and these notable Hg/TOC spikes (all TOC <1 al="" also="" and="" are="" at="" between="" biozone="" bottaccione="" boundary="" cf2="" clear="" correlation="" foraminiferal="" found="" h="" hg="" i="" ii="" iii="" in="" jerup="" jhilmili="" kpg="" meghalaya="" no="" occurs="" p1a="" planktic="" section.="" sections="" spike="" sub="" subzone="" the="" within="">2

O₃ exists in any of the studied sections. The Hg anomalies probably result from strong volcanic episodes of the Deccan phase-2 (started 250 kyr before the KPg boundary and lasted for 750 kyr) that exhaled sulfuric aerosols, carbon dioxide and other toxic agents which reached a critical threshold, represented in true Hg enrichments in the paleoenvironments. The possibility that Hg enrichments resulted from anoxia scavenging on the seafloor and penetration downward into sediments is not supported in the stratigraphic record of Mo/Al ratios redox proxy.<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within="">

<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within=""> Hg isotopes were analyzed in samples from all KPg boundary sections in this study and from Bidart, France, the latter for comparison. Hg isotopes yielded δ202Hg values ranging from −1 to −2‰ and Δ201Hg signatures from 0 to 0.05‰ (spike II in Højerup, Bottaccione and Meghalaya KPg boundary layers) consistent with volcanic emission of Hg (0 to −2‰). The δ202Hg in spike I in Meghalaya and Padriciano and spike III in Jhilmili is consistent with volcanic emission of Hg. Two samples from Bajada del Jagüel and four from Bidart, however, display isotope signals compatible with volcanic emission/chondrite Hg. The results of three other samples are characteristic for reworked sediment, soil and/or peat. Most of the data show small positive Δ201Hg, in favor of long-term atmospheric transport prior to deposition, supporting a volcanic origin for the Hg. The present study broadens, therefore, the potential use of Hg as stratigraphic marker and, moreover, confirms that in the critical KPg transition, Hg was enriched in paleoenvironments at three distinct stages during the Deccan phase-2.
<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within="">

<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within="">

New Remains of Late Cretaceous Giant Bird Gargantuavis philoinos Found in France

New remains of the giant bird Gargantuavis philoinos from the Late Cretaceous of Provence (south-eastern France)

Authors:

Buffetaut et al

Abstract:

Two incomplete pelves of the giant bird Gargantuavis philoinos are described from Late Cretaceous deposits at Fox-Amphoux (Var, south-eastern France). They consist of synsacra with attached parts of the ilia. One of them has undergone considerable dorsoventral compression, which makes it very similar in appearance to the holotype pelvis of Gargantuavis philoinos from Campagne-sur-Aude (Aude, southern France). The second specimen has suffered some lateral distortion but is uncrushed dorsoventrally. Because of this, its avians characters (including an arched synsacrum and widespread pneumatisation) are especially clear. These new specimens confirm the avian nature of Gargantuavis and reveal new details about its pelvic anatomy, but provide little new evidence about its systematic position within Aves. The geographical distribution and general rarity of Gargantuavis are discussed.

Marine Biota was Brought into Songliao Lake by Marine Incursions During the Late Cretaceous

Late Cretaceous marine fossils and seawater incursion events in the Songliao Basin, NE China

Authors:

Xi et al

Abstract:

The Songliao Basin is the largest non-marine oil-bearing basin in China. Because of the absence of substantial evidence, the hypothesis of seawater incursion events into the Songliao Basin remains controversial. The presence of marine fossils could provide direct proof to support this supposition. Here, we report new discoveries of foraminifera, calcareous nannofossils, brackish dinoflagellates, and other marine and brackish-water fossils to support the suggestion of seawater incursion events in the Songliao Basin. Relatively abundant benthic and planktonic foraminifera, calcareous nannofossils, marine and brackish-water dinoflagellates, fish, and bivalves have been discovered in Members 1 and 2 of the Nenjiang Formation, a few foraminifera and brackish-water dinoflagellates have been found in the lower Qingshankou Formation, and just a few brackish-water bivalves have been found in the uppermost Qingshankou Fm. Based on the presence of marine molecular fossils and other evidence, we suggest that relatively large seawater incursion events occurred during the sedimentation of the lower Nenjiang Fm., relatively smaller seawater incursions occurred during the deposition of the lower Qingshankou Fm., and possibly a very small seawater incursion occurred during the sedimentation of the uppermost Qingshankou Fm. These seawater incursion events in the Songliao Basin were controlled by regional tectonic activity, evolution of the palaeo Songliao Lake, and global sea level change. These periodic seawater incursions brought marine biota into the palaeo Songliao Lake.

Yubaartar zhongyuanensis: a Large multituberculate mammal From Late Cretaceous China

Largest known Mesozoic multituberculate from Eurasia and implications for multituberculate evolution and biology

Authors:

Xu et al

Abstract:

A new multituberculate, Yubaartar zhongyuanensis gen. and sp. nov., is reported from the Upper Cretaceous of Luanchuan County, Henan Province, China. The holotype of the new taxon is a partial skeleton with nearly complete cranium and associated lower jaws with in situ dentitions. The new species is the southern-most record of a Late Cretaceous multituberculate from outside of the Mongolian Plateau in Asia and represents the largest known Mesozoic multituberculate from Eurasia. The new specimen displays some intriguing features previously unknown in multituberculates, such as the first evidence of replacement of the ultimate upper premolar and a unique paleopathological case in Mesozoic mammals in which the animal with a severely broken right tibia could heal and survive in natural condition. The phylogenetic analysis based on craniodental characters places Yubaartar as the immediate outgroup of Taeniolabidoidea, a group consisting of a North American clade and an Asian clade. This relationship indicates at least a faunal interchange of multituberculates before the K-Pg transition. The new evidence further supports the hypothesis that disparity in dental complexity, which relates to animal diets, increased with generic richness and disparity in body size, and that an adaptive shift towards increased herbivory across the K-Pg transitional interval.

A Late Cretaceous Crocodilian Nest was Hidden in a Sauropod Nest in India

Crocodilian Nest in a Late Cretaceous Sauropod Hatchery from the Type Lameta Ghat Locality, Jabalpur, India

Authors:

Srivastava et al

Abstract:

The well-known Late Cretaceous Lameta Ghat locality (Jabalpur, India) provides a window of opportunity to study a large stable, near shore sandy beach, which was widely used by sauropod dinosaurs as a hatchery. In this paper, we revisit the eggs and eggshell fragments previously assigned to lizards from this locality and reassign them to crocodylomorphs. Several features point to a crocodilian affinity, including a subspherical to ellipsoidal shape, smooth, uneven external surface, discrete trapezoid shaped shell units with wide top and narrow base, basal knobs and wedge shaped crystallites showing typical inverted triangular extinction under crossed nicols. The crocodylomorph eggshell material presented in this paper adds to the skeletal data of these most probably Cretaceous-Eocene dryosaurid crocodiles.

Local PaleoTemperatures Varied Between 17.7 C (64 F) to 42.3 C (109 F) at Late Cretaceous Coastal Laos

Reconstruction of Late Cretaceous coastal paleotemperature from halite deposits of the Late Cretaceous Nongbok Formation (Khorat Plateau, Laos)

Authors:

Zhang et al

Abstract:

Cretaceous evaporites of the Maha Sarakhan Formation in Thailand (e.g., the Nongbok Formation, Laos) have been studied for almost a century as the huge potash deposits in the world. The consistently high local paleotemperatures should lead to huge salt deposits during the evaporation process. Primary fluid inclusions in halite can provide surface brine water temperatures directly and quantitatively. Until now, there have been no data published from paleotemperature of primary fluid inclusions of Cretaceous halite. The non-marine halite from the Cretaceous Nongbok Formation (Laos) precipitated from shallow brine waters with temperatures of 17.7–42.3 °C.

The Environment of the High Arctic During the Late Cretaceous

Environmental Constraints on Terrestrial Vertebrate Behaviour and Reproduction in the High Arctic of the Late Cretaceous

Authors:

Herman et al

Abstract:

Reconstructions of temperature and moisture regimes based on fossil leaves, combined with tree ring studies, detail the light regime, length of the growing season, and summer and winter temperatures of the Late Cretaceous Arctic. Such constraints have important implications for dinosaur feeding and reproductive behaviour, and the capacity to reside year-round in near-polar environments.

At the highest palaeolatitudes where dinosaurs have been found (82-85 °N) winter darkness lasted for ~ 120 days and the spring and autumn twilight periods for ~ 15 days. A mostly cloud and mist-shrouded environment witnessed a mean annual temperature (MAT) of 6-7 °C, a warm month mean temperature (WMMT) of 14.5 ± 3.1 °C and a cold month mean temperature (CMMT) of -2 ± 3.9 °C. Growth rings in wood suggest summer temperatures frequently fell below + 10 °C. Winter temperatures as low as -10 °C were likely for short periods. Spring bud break in late February to early March and leaf fall in early October limited the time when fresh food was available in any quantity to not more than 6 months.

The diversity of Arctic dinosaur body sizes implies a range of overwintering strategies but year-round residency requires reproduction. Burrowing and enclosed nest building no doubt facilitated overwintering for small animals, but for larger dinosaurs shelter was problematical. No dinosaur egg remains have yet been found as far north as 82° palaeolatitude, but they occur 6° further south in the Early Maastrichtian Kakanaut Formation, Northeastern Russia. Here the winter darkness was shorter (45 days), and the temperature regime warmer (MAT 10 °C, WMMT 19 °C, CMMT + 3 °C). The growing season (temperatures greater than 10 °C) was ~ 6.3 months and fresh food was available in quantity for slightly longer. These summer temperatures constrain the thermal regime of nest environments and suggest sophisticated nest management and possibly brooding strategies for the necessary rapid incubation and hatching before the onset of winter.

The Evolution of the Dental Formula of Late Cretaceous Eutherian Mammals

Evolutionary transition of dental formula in Late Cretaceous eutherian mammals

Authors:

Averianov et al

Abstract:

Kulbeckia kulbecke, stem placental mammal from the Late Cretaceous of Uzbekistan, shows a transitional stage of evolution in the dental formula from five to four premolars. A non-replaced dP3/dp3 may occur as individual variation. In other specimens, the lower premolars are crowded with no space for development of dp3. As is evident from the CT scanning of one juvenile specimen, the development of dp3 started in a late ontogenetic stage and was confined to the pulp cavity of the developing p2. This dp3 would have been resorbed in a later ontogenetic stage, as the roots of p2 formed. The initial stage of reduction of the third premolar can be traced to stem therians (Juramaia and Eomaia), which have both dP3 and P3 present in the adult dentition. Further delay in the development of dP3/dp3 led to the loss of the permanent P3/p3 (a possible synapomorphy for Eutheria). The dP3/dp3 was present during most of the adult stages in the Late Cretaceous stem placentals Zhelestidae and Gypsonictops. This tooth is totally absent in basal taxa of Placentalia, which normally have at most four premolars.

Late Cretaceous Hadrosaurs Confirmed to Herd

Herd structure in Late Cretaceous polar dinosaurs: A remarkable new dinosaur tracksite, Denali National Park, Alaska, USA

Authors:

Fiorillo et al

Abstract:

The discovery of a new tracksite of mostly hadrosaurid dinosaur footprints, made by a herd living in an ancient high-latitude continental ecosystem, provides insight into the herd structure and behavior of northern polar dinosaurs and perspective on populations of large-bodied herbivores in an Arctic greenhouse world. This tracksite occurs in the Upper Cretaceous Cantwell Formation in the Alaska Range (Denali National Park, Alaska, United States), and it is the largest tracksite known from this far north. Preservation of the tracksite is exceptional: most tracks, regardless of size, contain skin impressions and they co-occur with well-preserved plant fossils and invertebrate trace fossils of terrestrial and aquatic insects. Statistical analyses of the tracks show that individuals of four different age classes of hadrosaurids lived together in a large social group. Our research results independently corroborate the growth curve for hadrosaurids proposed by paleohistologists that suggests that these dinosaurs experienced a period of rapid growth early in their life history.

Late Cretaceous Polar (?) Forests of Southern New Zealand Were Deciduous

The Distinct foliar physiognomy of the Late Cretaceous forests of New Zealand – probably deciduous

Author:

Pole

Abstract:

Three features of leaf physiognomy: craspedodromous venation, compound teeth and a lobed leaf outline, figure prominently in the Late Cretaceous vegetation of southern New Zealand. These make it distinctly different from typical extant, predominantly evergreen forests and some deciduous vegetation. The physiognomy of the Late Cretaceous vegetation at the assemblage level shows more similarity with predominantly deciduous forests of the Northern Hemisphere, in terms of the proportions of these characters in the flora. At the taxon level, combinations of characters found in fossils are very similar to and in some cases restricted to, widespread extant Northern Hemisphere deciduous taxa, but also to rarer components of evergreen forests. It may not be possible to categorically determine whether any one fossil was deciduous. The distinctly different assemblage-level foliar physiognomy implies a distinctly different ‘lifestyle’ for the New Zealand forests that bordered Gondwana in the Late Cretaceous. It is highly likely that this physiognomy reflects an important deciduous component. This is unexpected as for at least part of this time New Zealand was apparently below (north of) the Polar Circle with a temperate and everwet climate.