Introducing Asfaltovenator vialidadi

Skeletal reconstruction and postcranial anatomy of Asfaltovenator vialidadi, MPEF PV 3440. From Rauhut and Pol, 2019.

During the Jurassic (201-145 mya) the breakup of the supercontinent Pangaea continued and accelerated with the opening of the North Atlantic by the rifting of Africa and North America, giving rise to the supercontinents of Laurasia and Gondwana. The sea level rise flooded continental areas around Pangaea, forming huge epicontinental seas, especially in northern Africa and eastern Laurasia (modern China). The world was predominantly warm with at least four times the present level of atmospheric CO2. The period is also characterized by the explosive adaptive radiation of dinosaurs.

By the Mid-Jurassic, Gondwana, the southern margen of supercontinent Pangea started to break up in different blocks: Antarctica, Madagascar, India, and Australia in the east, and Africa and South America in the west. During this period, the Tetanurae reached a global distribution. Tetanuran theropods comprise the majority of Mesozoic predatory dinosaurs, including Allosaurus and Tyrannosaurus, and the lineage leading to extant birds. Unfortunatelly, the fragmentary nature of the earliest known members of this group difficults our understanding of their early radiation. Asfaltovenator vialidadi gen. et sp. nov., a new basal tetanuran from the Middle Jurassic of Argentina, shed new ligth on the early radiation of this group. The generic name refers from Cañadón Asfalto Formation, the site where the fossil was found, and venator, a Greek word for hunter. The specific name honors the Administración de Vialidad Provincial of Chubut and the Dirección Nacional de Vialidad, for their aid to the Museo Paleontológico Egidio Feruglio.

Cranial anatomy of Asfaltovenator vialidadi. From Rauhut and Pol, 2019.

Discovered in 2002 by Leandro Canesa, the holotype (MPEF PV 3440) includes an almost complete skull and a partial skeleton. The skull is high and slightly arched, similar to that of other allosauroids and reached 75–80 cm long. The estimated body length of the holotype is 7–8 m, which makes Asfaltovenator comparable in size to the well-known Allosaurus.

Asfaltovenator shows an unusual mosaic of tetanuran characters. Megalosauroid characters include a pronounced kink in the anterodorsal margin of the maxillary ascending process, a medially closed maxillary fenestra, a deep posterior groove on ventral process of postorbital, and a broad fossa below the occipital condyle. Allosauroid characters include the presence of a pronounced supranarial fossa, the nasal participation in the antorbital fossa, presence of pneumatic foramina in the nasal, and lateral nasal crests.

 

llustration of the Asfaltovenator (Credit: Gabriel Lio/Conicet)

Tetanurae has been tradionally divided in three major clades: Megalosauroidea, Coelurosauria, and Allosauroidea. The phylogenetic analysis of A. vialidadi suggest that Allosauroidea  and Megalosauroidea have a common ancestor that they do not share with coelurosaurs. The new study also suggest that the Pliensbachian-Toarcian extinction event as a potential driver of tetanuran radiation.

 

References:

Rauhut, Oliver W. M.; Pol, Diego (2019), Probable basal allosauroid from the early Middle Jurassic Cañadón Asfalto Formation of Argentina highlights phylogenetic uncertainty in tetanuran theropod dinosaurs https://www.nature.com/articles/s41598-019-53672-7

Carrano, M. T., Benson, R. B. J., & Sampson, S. D. (2012). The phylogeny of Tetanurae (Dinosauria: Theropoda). Journal of Systematic Palaeontology, 10(2), 211–300. doi:10.1080/14772019.2011.630927

Deforestation: A Lesson from the Permian Extinction

Satellite photo of Amazon fires. Credit: NASA

The recent fires at Amazonas, Gran Canaria (Spain), Australia, and Indonesia sparked international outcry. Climate change makes forests hotter and drier, thus more likely to sustain uncontrolled fires. But fires are also linked with deforestation. Almost 1 million km2 of Amazon forest has already been deforested, and a recent study indicates that the number of active fires in this August was actually three times higher than 2018. Deforestation is a threat to biodiversity and ecosystems stability. It also leads to the loss of cultural diversity, the alteration of the hydrological cycle and climate systems.

The geological records show that large and rapid global warming events occurred repeatedly during the course of Earth history. The End-Permian extinction event (EPE) serves as a powerful deep-time analogue for modern deforestation and diversity loss, with as much as 95% of the marine animal species and a similarly high proportion of terrestrial plants and animals going extinct . This great crisis ocurred about 252 million years ago (Ma) during an episode of global warming. A recent study focussed on the Sydney Basin, Australia, shows how the typical Permian temperate forest communities disappeared abruptly, followed by a short ‘dead zone’ characterized only by charcoal, wood fragments, and fungi, signatures of an interval of wildfire and saprotrophic breakdown of organic matter.

Global paleogeographic map for the Permian-Triassic transition showing the location of the Siberian Traps Large Igneous Province. From Vajda et al., 2019

Two palynological events marked the end-Permian Event: the ‘algal/fungal/acritarch event’ (a bloom of Reduviasporonites, and of acritarchs in marine environments); and the ‘spore-spike event’. The first event in post-extinction continental deposits has contributed to a continuing debate as to whether the EPE interval was marked by eustatic sea-level rise. The ‘spore-spike event’ indicates that many plant groups survived in regional refugia, possibly at higher altitudes, or in coastal settings where conditions were consistently cooler or wetter. Some of those survivors constituted the pioneer vegetation during the Early Triassic.

During the EPE the woody gymnosperm vegetation (cordaitaleans and glossopterids) were replaced by spore-producing plants (mainly lycophytes) before the typical Mesozoic woody vegetation evolved. Glossopterids were the prime contributors of biomass to the vast Permian coal deposits of Gondwana, therefore their disappearance had major implications for ecosystem structure. The very rapid appearance of drought-tolerant plant associations (dominated by conifers and the seed fern Lepidopteris) in the macroflora of the Sydney Basin, may represent immigration of drought-adapted biota from other regions of Pangea.

Spores and pollen identified in the post-extinction mudstone at the Frazer Beach section. From Vajda et al., 2019

The palynological record suggests that wooded terrestrial ecosystems took four to five million years to reform stable ecosystems, while spore-producing lycopsids had an important ecological role in the post-extinction interval. The disappearance of the Glossopteris that dominated the cool Permian wetland forest of Gondwana, had  enormous consequences for landscape coverage, ecosystem structure, food webs, and caused substantial perturbations to the hydrological and carbon cycles of the entire biosphere.

Since the industrial revolution, the wave of animal and plant extinctions that began with the late Quaternary has accelerated. Australia has lost almost 40 percent of its forests, and almost 20% of the Amazon has disappeared in last five decades.Calculations suggest that the current rates of extinction are 100–1000 times above normal, or background levels. If we want to stop the degradation of our planet, we need to act now.

 

References:

V. Vajda et al. (2020), End-Permian(252Mya) deforestation, wildfires and flooding—An ancient biotic crisis with lessons for the present, Earth and Planetary Science Letters 529 (2020) 115875 https://doi.org/10.1016/j.epsl.2019.115875

Jos Barlow et al, Clarifying Amazonia’s burning crisis, Global Change Biology (2019). DOI: 10.1111/gcb.14872

Introducing Lajasvenator

Preserved elements of Lajasvenator ascheriae. From Coria et al., 2019

The Cretaceous beds of Patagonia have yielded the most comprehensive record of Cretaceous theropods from Gondwana and includes at least five main theropod lineages: Abelisauroidea, Carcharodontosauridae, Megaraptora, Alvarezsauridae, and Unenlagiidae. The best represented theropod clades in the Late Cretaceous terrestrial strata of the Neuquén Basin are the Abelisauroidea and the Carcharodontosauridae. Most discoveries come from continental units of ages ranging from Barremian to Maastrichtian. The lowest levels of the Cretaceous are well exposed in the marine and terrestrial deposits of the Mulichinco and Bajada Colorada formations.
The Carcharodontosauridae includes the largest land predators in the early and middle Cretaceous of Gondwana, like the popular Giganotosaurus carolinii, and in some way, they were considered as ecological equivalents to the Laurasian tyrannosauroids. The group evolved large skulls surpassing the length of the largest skull of Tyrannosaurus rex; and some derivaded forms had heavily sculptured facial bones. Another common trait is the fusion of cranial bones. Lajasvenator ascheriae, a new specimen from the Valanginian Mulichinco Formation, represents the oldest Cretaceous carcharodontosaurid from South America. The name derived from the Lajas, the city near where the specimen was found; and venator, a Latin word for hunter. The specific name honors Susana Ascheri, owner of the land where the fossil was discovered.

The holotype (MLL-PV-005) of this medium-sized theropod is an incomplete but partially articulated skeleton that includes a partial skull, partially articulated presacral vertebral series, four articulated caudal vertebra and fragments of the pelvic girdle. A second specimen (MLL-PV-Pv-007) includes the anterior ends of both dentaries, a quadratojugal, and fragments of cervical vertebrae, ribs and a possible tarsal bone. The holotype of Lajasvenator was collected in 2010 during fieldwork at Pilmatué. The second specimen was recovered in 2012.

Lajasvenator exhibits anterior projections on cervical prezygapophyses, lip-like crests on the lateral surfaces of cervical postzygapophyses, and bilobed anterior processes on cervical ribs. The phylogenetic analysis indicates that Lajasvenator is clearly nested in a basal position within Carcharodontosauridae.

References:

Coria, R.A., Currie, Currie, P.J., Ortega, F., Baiano, M.A., An Early Cretaceous, medium-sized carcharodontosaurid theropod (Dinosauria, Saurischia) from the Mulichinco Formation (upper Valanginian), Neuquén Province, Patagonia, Argentina, Cretaceous Research (2019) https://doi.org/10.1016/j.cretres.2019.104319
Novas, F.E., et al., Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia, Cretaceous Research (2013), http://dx.doi.org/10.1016/j.cretres.2013.04.001

Gnathovorax cabreirai and the origin of predatory dinosaurs

Skull of Gnathovorax cabreirai. From Pacheco et al., 2019

Herrerasauridae is a basal clade of predatory, obligatorily bipedal dinosaurs recorded from the Upper Triassic of Argentina and Brazil (although are putative records of herrerasaurids from the mid-late Norian strata of Europe and North America). The clade unequivocally comprises three species: Herrerasaurus ischigualastensis, Sanjuansaurus gordilloi, both from the Ischigualasto Formation of Argentina, and Staurikosaurus pricei, from the lower portion of the Santa Maria Formation of southern Brazil. Now, a new specimen from the Santa Maria Formation shed light into poorly understood aspects of the Herrerasauridae anatomy.

Named Gnathovorax cabreirai, the new dinosaur was found in 2014 at the Marchezan site, municipality of São João do Polêsine, Rio Grande do Sul, Brazil. The generic name means “jaws inclined to devour”. The specific name honors Dr. Sérgio Furtado Cabreira, the palaeontologist that found the specimen. The Santa Maria Formation in southern Brazil, comprises a succession of Middle to Late Triassic sedimentary rocks that have been long renowned for their rich tetrapod fossils including one of the oldest (and the best preserved) associations of dinosaur and dinosaur precursor.

Photographs and reconstruction of the braincase and endocast of Gnathovorax cabreirai. From Pacheco et al., 2019.

Gnathovorax lived around 230 million years ago and measured about three meters in length. The holotype (CAPPA/UFSM 0009) is an almost complete and partially articulated skeleton. The skull is almost entirely preserved. Among other characters, Gnathovorax presents three premaxillary teeth; an additonal fenestra between the maxilla and premaxilla contact; two well defined laminae in the antorbital fossa of the maxilla, with a depression between them. The proximal portion of the femur lacks a caudomedial tuber. The tibia equals 90% of the femoral length and there are three phalanges in pedal digit V.

The study of the internal anatomy of the skull through CT-scanning reveals several aspects of the neuroanatomy of this group. The presence of a well-developed floccular fossa lobes of the cerebellum is related to motor control of the eye and head, which in turn may be related to the predatory habit of the group.

References:
Pacheco C, Müller RT, Langer M, Pretto FA, Kerber L, Dias da Silva S. 2019. Gnathovorax cabreirai: a new early dinosaur and the origin and initial radiation of predatory dinosaurs. PeerJ 7:e7963 https://doi.org/10.7717/peerj.7963

Meet Ferrisaurus sustutensis, the iron lizard from the Sustut River.

 

Preserved elements of the holotype of Ferrisaurus sustutensis. From Arbour and Evans, 2019.

In 1971, during uranium and thorium exploration in the Sustut Basin of northern British Columbia, Canada, Kenny F. Larsen registered above-background levels of radiation from a talus slope near the confluence of Birdflat Creek and the Sustut River. The source of this radiation were the fossil remains of an unknow dinosaur. Larsen, an economic geologist, donated the bones to the Dalhousie University (Halifax, NS) in 2004. Later, the specimen was accessioned into the collection of the Royal British Columbia Museum in Victoria, BC.

Initially described as a pachycephalosaur or a basal ornithopod similar to Thescelosaurus, a new study determined that the remains belongs to a new genus and species: Ferrisaurus sustutensis. The holotype (RBCM P900) includes portions of the pectoral girdles, left forelimb, left hindlimb, and right pes. The name derived from Latin ferrum (=iron) and Greek sauros (=lizard), referencing to the specimen’s discovery along a railway line. The specific name honors its provenance near the Sustut River and within the Sustut Basin.

Pedal elements of Ferrisaurus sustutensis compared to other Laramidian small-bodied ornithischians. From Arbour and Evans, 2019.

Despite the lack of cranial material Ferrisaurus can be placed within leptoceratopsids based on several aspects of the preserved phalanges. Leptoceratopsids were short-frilled, hornless ceratopsians that lived in Campanian–Maastrictian aged dinosaur assemblages from Asia and North America. Ferrisaurus measured about 1.75 metres in length and 150 kilograms in weight and is similar in size to large specimens of Leptoceratops and Cerasinops.

 

References:

Arbour VM, Evans DC. 2019. A new leptoceratopsid dinosaur from Maastrichtian-aged deposits of the Sustut Basin, northern British Columbia, Canada. PeerJ 7:e7926 https://doi.org/10.7717/peerj.7926

Arbour, V. M., & Graves, M. C. (2008). An ornithischian dinosaur from the Sustut Basin, north-central British Columbia, Canada. Canadian Journal of Earth Sciences, 45(4), 457–463. doi:10.1139/e08-009 

Halloween special VII: A story of Darkness and Climate Change.

In April of 1815 the eruption of Mount Tambora released two million tons of debris and sulphur components into the atmosphere. The following year was known as “the year without summer”. The eruption produced famine, riots, and disease outbreak. Charles Lyell describes the eruption in his Principles of Geology: “Great tracts of land were covered by lava, several streams of which, issuing from the crater of the Tomboro Mountain, reached the sea. So heavy was the fall of ashes, that they broke into the Resident’s house at Bima, forty miles east of the volcano, and rendered it, as well as many other dwellings… The darkness occasioned in the daytime by the ashes in Java was so profound, that nothing equal to it was ever witnessed in the darkest night.”

The 1815 eruption of Tambora volcano (Sumbawa island, Indonesia) was the largest volcanic eruption in the last 500 years. The dust, gas, rock and pyroclastic flows hitted the surronding sea hard enough to set off moderate-sized tsunami that struck the shores of various islands in the Indonesian archipelago. Over 71 000 people died during, or in the aftermath of, the eruption near Sumbawa and the island of Lombok. The nothern hemisphere experienced severe weather. Summer temperatures across much of western and central Europe were 1–2°C cooler than the average for the period 1810–1819.

The Villa Diodati. Image from Finden’s Landscape & Portrait Illustrations to the Life and Works of Lord Byron, vol. 2 (London: John Murray, 1832).

The event inspired the great romantic poet Lord Byron to wrote “Darkness”:

I had a dream, which was not all a dream.
The bright sun was extinguish’d, and the stars
Did wander darkling in the eternal space,
Rayless, and pathless, and the icy earth
Swung blind and blackening in the moonless air;
Morn came and went—and came, and brought no day,
And men forgot their passions in the dread…”
The poem, with a vision of an icy Earth full of desolation and despair was published in 1816. At the time, after a failed marriage, scandalous affairs and huge debts, Byron left England and never returned. He traveled to Switzerland whith his physician, Dr John William Polidori, where he met up with Percy Bysshe Shelley and Mary Wollstonecraft Godwin (she married Shelley later that year) at the Villa Diodati on the banks of Lake Geneva. The meeting was organized by Clare Clairmont, Mary’s step-sister and a former lover of Lord Byron, because Shelley wanted to meet the great poet.
Years later, Mary Shelley wrote about their stay at Geneva: “it proved a wet, ungenial summer, and incessant rain often confined us for days to the house. Some volumes of ghost stories translated from the German into French, fell into our hands. There was the History of the Inconstant Lover, who, when he thought to clasp the bride to whom he had pledged his vows, found himself in the arms of the pale ghost of her whom he had deserted. There was the tale of the sinful founder of his race, whose miserable doom it was to bestow the kiss of death on all the younger sons of his fated house, just when they reached the age of promise.” 

Illustration from the frontispiece of the 1831 edition of Frankestein.

Byron proposed a ghost story contest. They all agreed. Byron wrote a short, fragmentary vampire tale. Shelley wrote a tale inspired by his childhood. Polidori used Byron’s tale and wrote The Vampyre. The story was first published in April 1819 in Henry Colburn’s New Monthly Magazine. Byron himself was the model for the vampire character, Lord Ruthven. The story was an immediate popular success and influenced Bram Stoker’s Dracula.
Mary’s contribution was Frankenstein: “I busied myself to think of a story, —a story to rival those which had excited us to this task. One which would speak to the mysterious fears of our nature, and awaken thrilling horror—one to make the reader dread to look round, to curdle the blood, and quicken the beatings of the heart.”
As in “Darkness”, Frankenstein deal with desolation and despair. Both are notable examples of the narrative of the climate disaster and the trauma unfolding around them in the Tambora years of 1816-18.
Mount Tambora continued rumbling intermittently at least up to August 1819. Once it was similar in stature to Mont Blanc. And of course, Mer de Glace, on the slope of the mountain, is where Victor Frankenstein reunited with his Creature: “From the side where I now stood Montenvers was exactly opposite, at the distance of a league; and above it rose Mont Blanc, in awful majesty…. The sea, or rather the vast river of ice, wound among its dependant mountains, whose aerial summits hung over its recess….” (Mary Shelley, Frankenstein, 1818)
References:
Oppenheimer, C. (2003). Climatic, environmental and human consequences of the largest known historic eruption: Tambora volcano (Indonesia) 1815. Progress in Physical Geography, 27(2), 230–259. doi:10.1191/0309133303pp379ra
Shelley, Mary. (1818) Frankenstein or, The Modern Prometheus. [via Gutenberg Project.]
Polidori, John. (1819) The Vampyre and Other Tales of the Macabre. [via Gutenberg Project.]

Mutagenesis in land plants during the end-Triassic mass extinction

 

A basaltic lava flow section from the Middle Atlas, Morocco. From Wikimedia Commons.

During the last 540 million years five mass extinction events shaped the history of the Earth. The End-Triassic Extinction at 201.51 million years (Ma) is probably the least understood of these events. Most mammal-like reptiles and large amphibians disappeared, as well as early dinosaur groups. In the oceans, this event eliminated conodonts and nearly annihilated corals, ammonites, brachiopods and bivalves. In the Southern Hemisphere, the vegetation turnover consisted in the replacement to Alisporites (corystosperm)-dominated assemblage to a Classopollis (cheirolepidiacean)-dominated one.

The mass extinction event was likely caused by the eruption of the Central Atlantic Magmatic Province (CAMP), a large igneous province emplaced during the initial rifting of Pangea. Data indicates that magmatic activity started c. 100,000 years before the endTriassic event and continued in pulses for 700,000 years. The CO2 emissions caused global warming. The SO2 emissions on mixing with water vapour in the atmosphere, caused acid rain, which in turn killed land plants and caused soil erosion.

A normal fern spore compared with mutated ones from the end-Triassic mass extinction event. Image credit: S LINDSTRÖM, GEUS

Volcanoes are also a primary source of mercury (Hg) in the global atmosphere. Mercury can cause morphologically visible abnormalities in plants and their reproductive cells (spores and pollen). A new study led by Sofie Lindström of the Geological Survey of Denmark and Greenland analized various types of abnormalities in the reproductive cells of ferns, with focus in two morphogroups: LTT-spores (laevigate, trilete fern spores with thick exine), and LCT-spores (laevigate, circular, trilete spores). The LTT-spores were produced primarily by the fern families Dipteridaceae, Dicksoniaceae, and Matoniaceae, while LCT spores were primarily produced by ferns belonging to Osmundaceae and Marattiales.

The elevated concentrations of mercury (Hg) in sedimentary rocks in North America, Greenland, England, Austria, Morocco, and Peru are linked to CAMP eruptions. This pulse of mercury also correlate with high occurrences of abnormal fern spores, indicating severe environmental stress and genetic disturbance in the parent plants. Three negative organic C-isotope excursions (CIEs) have being recognized at the end-Triassic: the Marshi, the Spelae, and the top-Tilmanni CIEs. Malformations in LTT-spores first occur sporadically in the lower pre-Marshi interval. LCT-spores are present but are generally rare in this interval. During the Spelae CIE, the occurrences of moderate to severe malformations increased and aberrant forms can encompass as much as 56% of the counted LTT-spores. This interval is associated with marked global warming, recorded by stomatal proxy data.

 

 

References:

Sofie Lindström et al. Volcanic mercury and mutagenesis in land plants during the end-Triassic mass extinction, Science Advances (2019). DOI: 10.1126/sciadv.aaw4018}

Grasby, S. E., Them, T. R., Chen, Z., Yin, R., & Ardakani, O. H. (2019). Mercury as a proxy for volcanic emissions in the geologic record. Earth-Science Reviews, 102880. doi:10.1016/j.earscirev.2019.102880

Ocean acidification and the end-Cretaceous mass extinction

Heterohelix globulosa foraminifera isolated from the K-Pg boundary clay at Geulhemmerberg in the Netherlands. Image credit: Michael J. Henehan/PNAS

The Cretaceous–Paleogene extinction that followed the Chicxulub impact was one of the five great Phanerozoic mass extinctions. Three-quarters of the plant and animal species on Earth disappeared, including non-avian dinosaurs, pterosaurs, marine reptiles, ammonites, and planktonic foraminifera. The impact released an estimated energy equivalent of 100 teratonnes of TNT, induced earthquakes, shelf collapse around the Yucatan platform, and widespread tsunamis that swept the coastal zones of the surrounding oceans. The event also produced high concentrations of dust, soot, and sulfate aerosols in the atmosphere. Global forest fires might have raged for months. Photosynthesis stopped and the food chain collapsed. The impacto also caused sudden ocean acidification, impacting marine ecosystems and the carbon cycle. Around the time of the impact, 23,000 to 230,000 cubic miles of magma erupted out of the mid-ocean ridges, all over the globe. One of the largest eruptive events in Earth’s history. This pulse of global marine volcanism played an important role in the environmental crisis at the end of the Cretaceous. Marine volcanism also provides a potential source of oceanic acidification, but a new study by Yale University indicates that the sudden ocean acidification was caused by the Chicxulub bolide impact (and not by the volcanic activity) that vaporised rocks containing sulphates and carbonates, causing sulphuric acid and carbonic acid to rain down. The evidence came from the shells of planktic and benthic foraminifera.

Foraminifera are crucial elements for our understanding of past and present oceans. Their skeletons take up chemical signals from the sea water, in particular isotopes of oxygen and carbon. Over millions of years, these skeletons accumulate in the deep ocean to become a major component of biogenic deep-sea sediments. Ocean acidification in the geological record is often inferred from a decrease in the accumulation and preservation of CaCO3 in marine sediments, potentially indicated by an increased degree of fragmentation of foraminiferal shells. In the early 1990’s it was recognised that the boron isotopic composition of marine carbonates was determined largely by ocean pH. Usingy the boron isotope-pH proxy to planktic and benthic foraminifera, the new study determinated the ocean pH drop following the Chicxulub impact.

The Cretaceous/Palaeogene extinction boundary clay at Geulhemmerberg Cave. Image credit: Michael J. Henehan

The boron isotope composition of carbonate samples obtained from a shallow-marine sample site (Geulhemmerberg Cave, The Netherlands) preserved sediments from the first 100 to 1000 years after the asteroid’s impact. The data from the Geulhemmerberg Cave indicate a marked ∼0.25 pH unit surface ocean acidification event within a thousand years. This change in pH corresponds to a rise in atmospheric partial pressure of CO2 (pCO2) from ∼900 ppm in the latest Maastrichtian to ∼1,600 ppm in the immediate aftermath of bolide impact.

Ocean acidification was the trigger for mass extinction in the marine realm. Acidification affects the biogeochemical dynamics of calcium carbonate, organic carbon, nitrogen, and phosphorus in the ocean and interferes with a range of processes including growth, calcification, development, reproduction and behaviour in a wide range of marine organisms like planktonic coccolithophores, foraminifera, echinoderms, corals, and coralline algae. Additionaly, ocean acidification can intensify the effects of global warming, in a dangerous feedback loop.

Anthropogenic climate change and ocean acidification resulting from the emission of vast quantities of CO2 and other greenhouse gases pose a considerable threat to ecosystems and modern society. Since the Industrial Revolution the pH within the ocean surface has decreased ~0.1 pH and is predicted to decrease an additional 0.2 – 0.3 units by the end of the century. This underlines the urgency for immediate action on global carbon emission reductions.

 

 

References:

Michael J. Henehan el al., “Rapid ocean acidification and protracted Earth system recovery followed the end-Cretaceous Chicxulub impact,” PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1905989116

Kump, L.R., T.J. Bralower, and A. Ridgwell. 2009. Ocean acidification in deep time. Oceanography 22(4):94–107, https://doi.org/10.5670/oceanog.2009.100.

 

The Last Mammoths

Mammuthus primigenius, Royal British Columbia Museum. From Wikipedia Commons

During the Late Pleistocene and early Holocene, most of the terrestrial megafauna became extinct. It was a deep global-scale event. The extinction was notably more selective for large-bodied animals than any other extinction interval in the last 65 million years. Among them, the mammoths offers a very complete fossil record, and their evolution is usually presented as a succession of chronologically overlapping species, including (from earliest to latest) M. meridionalis (southern mammoths), M. trogontherii (steppe mammoths), and M. columbi (Columbian mammoths) and M. primigenius (woolly mammoths).

Wrangel Island coast. From Wikipedia Commons

From Siberia to Alaska, mammoths were widespread in the northern hemisphere and their remains inspired all types of legends. Their lineage arose in Africa during the late Miocene, and first appeared in Europe almost three million years ago. The iconic M. primigenius arose in northeastn Siberia from the steppe mammoth (Mammuthus trogontherii) and their extinction has inspired an impressive body of literature. Multiple explanatory hypotheses have been proposed for this event: climatic change, overhunting, habitat alteration, and the introduction of a new disease.

The world’s last population of woolly mammoths lived on Wrangel Island going extinct around 4,000 years ago. In contrast the mammoth population from Russia disappeared about 15,000 years ago, while the mammoths of St. Paul Island in Alaska disappeared 5,600 years ago. The Wrangel Island was a part of Beringia, an ancient landmass, that included the land bridge between Siberia and Alaska. Global sea level transgression at the end of the Pleistocene isolated Wrangel Island from the mainland and broke up Beringia. Palynological and isotopic evidence suggest that present climatic conditions and floral composition were established right after the Pleistocene-Holocene transition.

A mammoth tooth on the riverbank on Wrangel Island. Image credit; Juha Karhu/University of Helsinki

Tooth specimens are about 90% of all the mammoth material for Wrangel Island. The multi-isotopic evidence (carbon, nitrogen and sulfur in collagen) measured on Wrangel Island mammoths supports the idea that this relict population mantained a typical mammoth ecology despite climate change and decreasing genetic diversity. It has been suggested that the extinction of the Wrangel Island mammoths was possibly caused by a short-term crisis, possibly linked to climatic anomalies, however the anthropogenic influence should not be dismissed despite lack of tangible evidence of hunting.

 

References:

Laura Arppe, Juha A. Karhu, Sergey Vartanyan, Dorothée G. Drucker, Heli Etu-Sihvola, Hervé Bocherens. Thriving or surviving? The isotopic record of the Wrangel Island woolly mammoth population. Quaternary Science Reviews, 2019; 222: 105884 DOI: 10.1016/j.quascirev.2019.105884

Meet Ferrodraco lentoni, the Iron Dragon

Ferrodraco lentoni gen. et sp. nov. holotype. Scale bar = 50 mm. From Pentland et al., Scientific Reports.

Pterosaurs were the first flying vertebrates. From the Late Triassic to the end of the Cretaceous, the evolution of pterosaurs resulted in a variety of eco-morphological adaptations, as evidenced by differences in skull shape, dentition, neck length, tail length and wing span. Their reign extended to every continent, but due to the fragile nature of their skeletons the fossil record of pterosaurs is rather patchy, with most occurrences limited to fragmentary remains. The newly described Ferrodraco lentoni, from the Winton Formation (Cenomanian–lower Turonian), is the most complete pterosaur specimen ever found in Australia. Previously, and only based on fossil skull fragments, two other species of pterosaurs were described from Australia: Mythunga camara and Aussiedraco molnari.

Discovered in 2017, the holotype specimen AODF 876 (Australian Age of Dinosaurs Fossil) includes a partial skull, five partial neck vertebrae, and bones from both the left and right wings. The wingspan of Ferrodraco was approximately 4 m, with a skull probably reaching 60 cm in length. The generic name comes from the Latin language: ferrum (iron), in reference to the ironstone preservation of the holotype specimen, and draco (dragon). The species name, lentoni, honours former Winton Shire mayor Graham Thomas ‘Butch’ Lenton.

Ferrodraco lentoni gen. et sp. nov. holotype rostral sections AODF 876. Cross-section. Scale bar = 20 mm. From Pentland et al., Scientific Reports.

Based on several cranial synapomorphies, including the presence of a mandibular groove, smooth and blade-like premaxillary and mandibular crests, and spike-shaped teeth, Ferrodraco falls within the clade Anhangueria. This group has also been recorded in the Early Cretaceous of Brazil, China and England. It has been suggested that anhanguerians went extinct at the end of the Cenomanian. This interval was characterised by an increase in atmospheric and oceanic surface temperatures, a global oceanic anoxic event, and marine transgression. Given that Ferrodraco was recovered from a locality northeast of Winton, which is considered as early Turonian in age, the new specimen potentially represents a late-surviving member of the anhanguerians.

 

References:

Adele H. Pentland et al., Ferrodraco lentoni gen. et sp. nov., a new ornithocheirid pterosaur from the Winton formation (cenomanian-lower turonian) of Queensland, Australia, DOI: 10.1038/s41598-019-49789-4