“Lucifer’s Hammer killed the dinosaurs”

Lucifer’s Hammer Hardcover (1977)

The end of the Mesozoic era at ca. 66 million years ago (Ma) is marked by one of the most severe biotic crisis in Earth’s history: the Cretaceous-Paleogene (K-Pg) mass extinction. During the event, three-quarters of the plant and animal species on Earth disappeared, including non-avian dinosaurs, pterosaurs, marine reptiles, ammonites, and planktonic foraminifera. Two planetary scale disturbances were linked to this mass extinction event: the eruption of the Deccan Traps large igneous province, and the collision of an asteroid of more than 10 km in diameter with the Yucatan Peninsula.

“Lucifer’s Hammer”, written by Larry Niven and Jerry Pournelle, was the first major science fiction novel to try to deal realistically with the planetary emergency of an impact event. It was published in 1977. Almost at the same time, the discovery of anomalously high abundance of iridium and other platinum group elements in the Cretaceous/Palaeogene (K-Pg) boundary led to the hypothesis that an asteroid collided with the Earth and caused one of the most devastating events in the history of life.

Gravity anomaly map of the Chicxulub impact structure (From Wikimedia Commons)

“Lucifer’s Hammer killed the dinosaurs,” said US physicist Luis Alvarez, in a lecture on the geochemical evidence he and his son found of a massive impact at the end of the Cretaceous period. A year later, Pemex (a Mexican oil company) identified Chicxulub as the site of this massive asteroid impact. The crater is more than 180 km (110 miles) in diameter and 20 km (10 miles) in depth. 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 combination of dust and aerosols precipitated a severe impact winter in the decades after 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.

The Deccan traps

Early work speculated that the Chicxulub impact triggered large-scale mantle melting and initiated the Deccan flood basalt eruption. Precise dating of both, the impact and the flood basalts, show that the earliest eruptions of the Deccan Traps predate the impact. But, the Chicxulub impact, and the enormous Wai Subgroup lava flows of the Deccan Traps continental flood basalts appear to have occurred very close together in time. Marine volcanism also provides a potential source of oceanic acidification, but a recemt 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. More recently, a new study focused on carbon cycle modeling and paleotemperature records shows that the Chicxulub impact was the primary driver of the end-Cretaceous mass extinction.The global temperature compilation reveals that ~50% of Deccan Trap CO2 outgassing occurred well before the impact. Additionalty, the Late Cretaceous warming event attributed to Deccan degassing is of a comparable size to small warming events in the Paleocene and early Eocene.

References:
P.M. Hull et al., “On impact and volcanism across the Cretaceous-Paleogene boundary,” Science (2019). Vol. 367, Issue 6475, pp. 266-272 https://science.sciencemag.org/content/367/6475/266

Alvarez, L., W. Alvarez, F. Asaro, and H.V. Michel. 1980. Extraterrestrial cause for the Cretaceous-Tertiary extinction: Experimental results and theoretical interpretation. Science 208:1095–1108.

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

Top fossil discoveries of 2019.

This was a turbulent year. The recent fires at Amazonas, Gran Canaria (Spain), Australia, and Indonesia sparked international outcry. Climate emergency movement took centre stage and Greta Thunberg become a household name as the face of the climate activism. Carl Sagan once said “You have to know the past to understand the present.”As the climate crisis escalates many studies published this year highlights the relation between mass extinctions and climate change.

Nevertheless, 2019 was another remarkable year for paleontology. Among the most striking fossil discoveries are China’s Qingjiang biota that document the Cambrian explosion; the nearly complete skull of Australopithecus anamensis, the oldest known species in a hominid genus that includes Australopithecus afarensis; and the world’s oldest fossilised forest found at an abandoned quarry in Cairo, New York. My top list (with a profound bias towards vertebrate paleontology) includes:

  • Moros intrepidus

Moros intrepidus. Credit: Jorge Gonzalez

Moros intrepidus, a diminutive tyrannosauroid, from Cenomanian-aged terrestrial deposits of western North America. The holotype (NCSM 33392), preserves a partial right hind limb including portions of the femur, tibia, second and fourth metatarsals, and phalanges of the fourth pedal digit. According to the histological analysis, M. intrepidus exhibits a moderate growth rate, similar to Guanlong, a more primitive tyrannosauroid from the Late Jurassic of China. By contrast, large-bodied, tyrannosaurines from the last stages of the Cretaceous, like Gorgosaurus, were already triple their masses at similar ages. M. intrepidus suggests that North American tyrannosauroids were restricted to small sizes for a protracted period of ~15 million years and at some point at the Turonian, they embarked on a trend of rapid body size increases, to became the top predators of the Cretaceous.

  • Bajadasaurus pronuspinax

Bajadasaurus pronuspinax gen. et sp. nov., from the Early Lower Cretaceous of Bajada Colorada Formation in Northern Patagonia, Argentina, was discovered in 2013, by a team of paleontologists from CONICET, Fundación Félix de Azara, Universidad Maimónides, and Museo Paleontológico Ernesto Bachmann. The holotype, MMCh-PV 75, includes a nearly complete skull (left maxilla, left lacrimal, both prefrontals, both frontals, both parietals, both postorbitals, both squamosals, left quadratojugal, both pterygoids, both quadrates, supraoccipital, exoccipital-opisthotic complex, basioccipital, basisphenoid, both prootics, both laterosphenoids, both orbitosphenoids, both dentaries, left surangular, both angulars, both splenials, left prearticular, left articular, isolated upper tooth row), both proatlases, atlantal neurapophyses, axis and the fifth cervical vertebra.

  • Iberodactylus andreui

Comparison of the rostrum of Iberodactylus andreui gen. et sp. nov. (MPZ-2014/1) with a cast of a skull of Hamipterus tianshanensis. From Holgado et al., 2019)

Iberodactylus andreui is a pterosaurs from the Lower Cretaceous of Spain. The holotype (MPZ-2014/1) consists of the anterior portion of the rostrum (~198 mm in length), and includes a partially preserved premaxillary crest, and a fragment of the maxillary bone with several fragmentary teeth. The specimen preserved its original 3D shape, although exhibits frequent fractured bones, that added to the eroded bone surfaces, reveal an external thing layer of cortical bone of 1.5 mm. The robustness and height of the premaxillary crest, suggest that MPZ-2014/1 may represent a male specimen. The most striking feature of MPZ-2014/1 is the premaxillary crest. This crest exhibits well-developed elongated, sub-vertical striae and sulci, anteriorly curved, a combination that is quite similar to Hamipterus tianshanensis from the Berriasian-Albian of China.

  • Suskityrannus hazelae

Partial skeleton of Suskityrannus hazelae. Image credit: Virginia Tech.

Suskityrannus hazelae is a small-bodied species phylogenetically intermediate between the oldest, smallest tyrannosauroids and the gigantic, last-surviving tyrannosaurids. The holotype specimen (MSM P4754) includes a partially articulated skull, and fragments of the braincase. The postcranial includes two cervical vertebrae with cervical rib fragments, , a trunk centrum, part of a sacral centrum, and distal portions of left metatarsals II–IV. The paratype (MSM P6178) includes the anterior portion of right dentary; left frontal, partial left postorbital, cervical, trunk, partial sacral and caudal vertebrae; isolated neural arches; partial left scapula; manual ungual fragments; partial pubes, femora, tibiae, fibulae and astragali; partial right pes; and bone fragments.

  • Notatesseraeraptor frickensis

Notatesseraeraptor frickensis at the Sauriermuseum Frick.

Notatesseraeraptor frickensis, from the Late Triassic of Switzerland, is a basal member of Dilophosauridae, a clade that comprises Dilophosaurus, and Cryolophosaurus. The specimen belong to an immature individual of length 2.6–3.0 m, and it was collected in 2006 from Gruhalde clay pit in Frick (Aargau, Switzerland), a place well known for its abundant, articulated Plateosaurus material. The cranium is proportionally long and low as is commonly found in traditional coelophysoid-grade neotheropods. The postcranial skeleton includes two articulated forelimbs, 13 dorsal, four sacral and four proximal caudal vertebrae; cervical, dorsal and sacral ribs; chevrons; gastralia; and even stomach contents ( a well-preserved maxilla of the rhynchocephalian Clevosaurus).

  • Ferrodraco lentoni

Ferrodraco lentoni gen. et sp. nov. holotype. From Pentland et al., Scientific Reports.

Ferrodraco lentoni, from the Winton Formation (Cenomanian–lower Turonian), is the most complete pterosaur specimen ever found in Australia. 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. 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.

  • Adratiklit boulahfa

Isolated cervical vertebra referred to Adratiklit boulahfa. From Maidment et al., 2019.

Adratiklit boulahfa, from the Middle Jurassic of Morocco, is the oldest stegosaur ever found. The holotype (NHMUK PV R37366) of Adratiklit boulahfa is a dorsal vertebra. Referred specimens include three cervical vertebrae (NHMUK PV R37367 and NHMUK R37368, the latter specimen consisting of a series of two articulated bones), a dorsal vertebra (NHMUK PV R37365) and a left humerus (NHMUK PV R37007). Stegosauria is a clade of ornithischian dinosaurs and the closest relative to Ankylosauria; together they form the Eurypoda. These armored dinosaurs were diverse and abundant throughout the Late Jurassic and Cretaceous in Laurasia; but their remains are extremely rare in Gondwana. It has been suggested that Isaberrysaura mollensis from the Jurassic of Argentina might be a stegosaur. Additionally fragmentary discoveries of possible eurypodans have been made in Australia, New Zealand, India and Madagascar, while some eurypodan trackways have been identified in Morocco, Bolivia and Brazil.

  • Gnathovorax cabreirai.

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

Gnathovorax cabreirai 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. 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.

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

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

Asfaltovenator vialidadi, a new basal tetanuran from the Middle Jurassic of Argentina, shed new ligth on the early radiation of this group. 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. 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 was a potential driver of tetanuran radiation.

  • A postcard from the Cretaceous

Nullotitan glaciaris gen. et sp. nov. Cervical vertebra (MACN Pv 18644) in left lateral (A), dorsal (B), posterior (C), right lateral (D), and longitudinal section (E) views

The Chorrillo Formation ((Upper Cretaceous) in the southern region of the Argentine Patagonia yielded an extraordinare fossil assemblage. Plants, palynomorphs, invertebrates and vertebrates constitutes an amazing window into de Cretaceous. Dinosaur remains include the elasmarian (basal Iguanodontia) Isasicursor santacrucensis gen. et sp. nov; the large titanosaur Nullotitan glaciaris gen. et sp. nov., small Megaraptoridae indet., and fragments of sauropod and theropod eggshells.

References:

Zanno, L.E, Tucker, R.T., Canoville, A., Avrahami, H.M., Gates, T.A., Makovicky, P.J. (2019), Diminutive fleet-footed tyrannosauroid narrows the 70-million-year gap in the North American fossil record, Communications Biology, DOI: 10.1038/s42003-019-0308-7

Gallina, Pablo A., Apesteguía, Sebastián, Canale, Juan I., Haluza, Alejandro (2019), A new long-spined dinosaur from Patagonia sheds light on sauropod defense system, Scientific Reports volume 9, Article number: 1392 DOI: https://doi.org/10.1038/s41598-018-37943-3

Borja Holgado, Rodrigo V. Pêgas, José Ignacio Canudo, Josep Fortuny, Taissa Rodrigues, Julio Company & Alexander W.A. Kellner, 2019, “On a new crested pterodactyloid from the Early Cretaceous of the Iberian Peninsula and the radiation of the clade Anhangueria”, Scientific Reports 9: 4940

Sterling J. Nesbitt et al. A mid-Cretaceous tyrannosauroid and the origin of North American end-Cretaceous dinosaur assemblages. Nature Ecology & Evolution, published online May 6, 2019; doi: 10.1038/s41559-019-0888-0

Marion Zahner; Winand Brinkmann (2019). “A Triassic averostran-line theropod from Switzerland and the early evolution of dinosaurs”. Nature Ecology & Evolution. doi:10.1038/s41559-019-0941-z

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

Maidment, Susannah C. R.; Raven, Thomas J.; Ouarhache, Driss; Barrett, Paul M. (2019-08-16). “North Africa’s first stegosaur: Implications for Gondwanan thyreophoran dinosaur diversity”. Gondwana Research. 77: 82–97. doi:10.1016/j.gr.2019.07.007
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

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
Novas, F., Agnolin, F., Rozadilla, S., Aranciaga-Rolando, A., Brissón-Eli, F., Motta, M., Cerroni, M., Ezcurra, M., Martinelli, A., D’Angelo, J., Álvarez-Herrera, G., Gentil, A., Bogan, S., Chimento, N., García-Marsà, J., Lo Coco, G., Miquel, S., Brito, F., Vera, E., Loinaze, V., Fernandez, M., & Salgado, L. (2019). Paleontological discoveries in the Chorrillo Formation (upper Campanian-lower Maastrichtian, Upper Cretaceous), Santa Cruz Province, Patagonia, Argentina. Revista del Museo Argentino de Ciencias Naturales, 21(2), 217-293.

Christmas edition: Geologizing with Dickens, part III.

Charles Dickens at his desk, by George Herbert Watkins (National Portrait Gallery. From Wikimedia Commons)

It was the best of times. In the nineteenth century England, the Industrial Revolution started a time of important social and political change. London became the financial capital of the world. Several scientific societies were forming, such as the Geological Society of London, while fascinating discoveries revealed part of the history of our planet. But it was also the worst of time. England was ruled by an elite, meanwhile most of the people were poor. Churches provided schools for poor children and infant mortality was high. During these difficult times, Charles Dickens revitalized the tradition of Christmas and to Victorian England, Dickens was Christmas.  He had only 31, when began to write A Christmas Carol. The novella tells the story of  Ebenezer Scrooge, a bitter old man who finds salvation through the visits of the three Ghosts of Christmas (Ghost of Christmas Past, Ghost of Christmas Present, and Ghost of Christmas Yet to Come).

Charles Dickens also contributed to the popularity of geology in the nineteenth century. For him, the ideal science was Geology. In his review of Hunt’s Poetry of Science, he wrote: “Science has gone down into the mines and coal-pits, and before the safety-lamp the Gnomes and Genii of those dark regions have disappeared … Sirens, mermaids, shining cities glittering at the bottom of quiet seas and in deep lakes, exist no longer; but in their place, Science, their destroyer, shows us whole coasts of coral reef constructed by the labours of minute creatures; points to our own chalk cliffs and limestone rocks as made of the dust of myriads of generations of infinitesimal beings that have passed away; reduces the very element of water into its constituent airs, and re-creates it at her pleasure…” (London Examiner, 1848).

Hawkins’ Sydenham Studio. From Wikimedia Commons.

When the Crystal Palace was opening at Sydenham, Dickens addressed the sculptor Benjamin Waterhouse Hawkings to ensure that the dinosaurs he had named, including the megalosaurus, and the iguanodon, were accurately recreated. In Bleak House and Dombey and Son, Dickens encourage readers to perceive the scene of the city as a geological fragment of a much broader spatial and temporal vision. In Bleak House the dinosaurs uncovered by the railway in Dombey and Son move centre stage: “Implacable November weather. As much mud in the streets as if the waters had but newly retired from the face of the earth, and it would not be wonderful to meet a Megalosaurus, forty feet long or so, waddling like an elephantine lizard up Holborn Hill.” 

Among his friends were Richard Owen and Sir Roderick Murchison. Murchinson’s wife, Charlotte, was a very close friend of Mary Anning, the most famous fossilist of the time. Mary has been called “the Princess of Palaeontology”  by the German explorer Ludwig Leichhardt and scientists like William Buckland or Henry de la Beche owe their achievements to Mary’s work. She discovered (along with her brother Joseph) the first specimens of what would later be recognized as Ichthyosaurus, the first complete Plesiosaurus, the first pterosaur skeleton outside Germany, and a fossil fish, with characteristics intermediate between sharks and rays, called Squaloraja (unfortunately, the specimen was lost in the destruction of the Bristol Museum by a German bombing raid in November, 1940)

Skull of an ichthyosaur painted with fossil sepia by Elizabeth Philpot.

Mary Anning was born on Lyme Regis on May 21, 1799. Her father was a carpenter and an amateur fossil collector who died when Mary was eleven. By the age of 27, Mary was the owner of a little shop: Anning’s Fossil Depot. Many scientist and fossil collectors from around the globe went to Mary´s shop. She was friend of Henry De la Beche, the first director of the Geological Survey of Great Britain, who knew Mary since they were both children and lived in Lyme Regis. De la Beche was a great supporter of Mary’s work. She also corresponded with Charles Lyell, William Buckland and Mary Morland, Adam Sedgwick and Sir Roderick Murchison. It’s fairly to say that Mary felt secure in the world of men, and a despite her religious beliefs, she was an early feminist. In an essay in her notebook, titled Woman!, Mary writes: “And what is a woman? Was she not made of the same flesh and blood as lordly Man? Yes, and was destined doubtless, to become his friend, his helpmate on his pilgrimage but surely not his slave…”

The article published in All the Year Round in 1865, about the life of Mary Anning. From the Internet Archive

In 1865, Charles Dickens wrote an article about Mary Anning’s life in his literary magazine “All the Year Round”, where emphasised the difficulties she had overcome: “Miss Anning wrote sadly enough to a young girl in London: “I beg your pardon for distrusting your friendship. The world has used me so unkindly, I fear it has made me suspicious of every one.” 

Mary Anning, ‘the greatest fossilist the world ever knew’, died of breast cancer on 9 March, 1847, at the age of 47. She was buried in the cemetery of St. Michaels. In the last decade of her life, Mary received three accolades. The first was an annuity of £25, in return for her many contributions to the science of geology. The second was in 1846, when the geologists of the Geological Society of London organized a further subscription for her. The third accolade was her election, in July 1846, as the first Honorary Member of the new Dorset County Museum in Dorchester. About her life and legacy Dickens wrote: “Her history shows what humble people may do, if they have just purpose and courage enough, toward promoting the cause of science. The inscription under her memorial window commemorates “her usefulness in furthering the science of geology” (it was not a science when she began to discover, and so helped to make it one), “and also her benevolence of heart and integrity of life.” The carpenter’s daughter has won a name for herself, and has deserved to win it.” 

References:

Dickens, Charles, 1812-1870, `Mary Anning, the Fossil-Finder’, All the year round, Volume XIII, Magazine No. 303, 11 February 1865, Pages: 60-63

A. BUCKLAND, ‘“The Poetry of Science”: Charles Dickens, Geology and Visual and Material Culture in Victorian London’, Victorian Literature and Culture, 35 (2007), 679–94 (p. 680).

A. BUCKLAND. Novel Science: Fiction and the Invention of Nineteenth-Century Geology. Chicago, IL and London: University of Chicago Press, 2013. 400 pp. 9 plts. $45.00. ISBN 978-0-226-07968-4

 

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 was 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