A brief introduction to the T. rex Family Tree.

“Sue” specimen, Field Museum of Natural History, Chicago

Tyrannosaurus rex is the most iconic dinosaur of all timeIt was discovered in the Hell Creek Formation by Barnum Brown in 1902, and later described  by Henry Fairfield Osborn in 1905. Osborn actually named two large Hell Creek tyrannosaurids, T. rex and Dynamosaurus imperiosus. He later realized that Dynamosaurus imperiosus and Tyrannosaurus rex were synonymous, but Tyrannosaurus has priority, as it preceded Dynamosaurus in the description (Osborn, 1906).

T-rex and its closest relatives, known as tyrannosaurids, comprise the clade Tyrannosauroidea, a relatively derived group of theropod dinosaurs, more closely related to birds than to other large theropods such as allosauroids and spinosaurids, that originated in the Middle Jurassic, approximately 165 million years ago. All tyrannosaurs were bipedal predators characterized by premaxillary teeth with a D-shaped cross section, fused nasals, extreme pneumaticity in the skull roof and lower jaws, a pronounced muscle attachment ridge on the ilium, and an elevated femoral head (Brusatte et al., 2010). For most of their evolutionary history, tyrannosauroids were mostly small-bodied animals and only reached gigantic size during the final 20 million years of the Cretaceous.

Skulls of the basal tyrannosauroids Guanlong (A), Dilong (B); Skulls of juvenile (C) and adult (D)Tyrannosaurus. (Adapted from Brusatte et. al., 2010)

Skulls of the basal tyrannosauroids Guanlong (A), Dilong (B); Skulls of juvenile (C) and adult (D)Tyrannosaurus. (Adapted from Brusatte et. al., 2010)

During the past 15 years, new discoveries from Russia, Mongolia and China helped to build the Tyranosaurs family tree. The oldest and most basal tyrannosaurs comprise a subclade, Proceratosauridae, which includes Kilesksus, Gualong, and Proceratosaurus. They were small-bodied animals no larger than a human, with elaborate cranial crests, extremely elongated external naris, a short ventral margin of the premaxilla, and depth of the antorbital fossa ventral to the antorbital fenestra is greater than the depth of the maxilla below the ventral margin of the antorbital fossa (Rauhut et al., 2010; Averianov et al., 2010).

Kileskus artistotocus, from the Middle Jurassic (167 mya), was discovered in 2010 in Western Siberia, by Alexander Averianov on the basis of an associated maxilla and premaxilla, a mandible fragment, and some possible associated postcranial elements. The cranial crest is currently unknown for Kileskus.

Pedal ungual phalanx of Kileskus aristotocus. Abbreviations: ft – flexor tubercle; lgr – lateral groove. Scale bar = 1 cm (From Averianov et. al.; 2010)

Pedal ungual phalanx of Kileskus aristotocus. Abbreviations: ft – flexor tubercle; lgr – lateral groove. Scale bar = 1 cm (From Averianov et. al.; 2010)

Guanlong wucaii, from the Late Jurassic of China, was first described in 2006. The generic name is derived from the Chinese Guan (crown) and long (dragon). The specific epithet wucaii (five colours) referred to the colours of rock of the Wucaiwan area where the fossil was found. The most striking trait of Guanlong is the complex nasal crest consisting of a highly pneumatic median crest that is about 1.5 mm thick for most of its length, and four supporting lateral laminae (Xu et al., 2006).

Proceratosaurus bradleyi, discovered in Gloucestershire, England in 1910 and described by Arthur Smith Woodward, it was originally thought to be an ancestor of Ceratosaurus. Some of the characters uniting Proceratosaurus with Guanlong are the  strongly  enlarged  nares, and a midline cranial crest or horn  on  the  nasals (Rauhut et al., 2010).

Guanlong wucaii. (Image adapted from Xu et al., 2006)

Guanlong wucaii. (Image adapted from Xu et al., 2006)

The giant, feathered tyrannosaur Yutyrannus huali, lived during the early Cretaceous period in what is now Northeastern  China. It was discovered in 2012 by Chinese palaeontologist Xing Xu. Yutyrannus weighed about 1,400 kilograms and  was at least 8 metres in length, and shares some features, particularly of the cranium, with derived tyrannosauroids, but is similar to other basal tyrannosauroids in possessing a three-fingered manus and a typical theropod pes.

Dilong paradoxus, also described by Xu, was discovered in 2004. This small tyrannosauroid shows a mosaic of characters, including a derived cranial structure resembling that of derived tyrannosauroids and a primitive postcranial skeleton similar to basal coelurosaurians. And at least one specimen was preserved with remnants of protofeathers.

Yutyrannus skeleton (From Wikimedia Commons)

Yutyrannus skeleton (From Wikimedia Commons)

Eotyrannus lengi, from the Early Cretaceous of the Isle of Wight, United Kingdom, was described in 2001. The holotype of Eotyrannus are estimated to have measured about 4 m (13 ft) long. However, as it is believed to have been juvenile, an adult specimen might have been somewhat larger.

Qianzhousaurus sinensis, was discovered in 2014 in China. Nicknamed “Pinocchio rex”, this long-snouted tyrannosaurids along with Alioramus, shows that these type of tyrannosaurids were widely distributed in Asia.

Nanuqsaurus hoglund, was a small dinosaur discovered in Alaska in 2014. The name is the combination ofnanuqthe Iñupiaq word for polar bear and the Greek ‘sauros’ (lizard). The specific name, hoglundi, honors the Texas philanthropist Forrest Hoglund.

Skull of Qianzhousaurus sinensis (Image credit: Junchang Lü et al.)

Skull of Qianzhousaurus sinensis (Image credit: Junchang Lü et al.)

Until recently, all tyrannosaurs fossils were limited to Asia and North America, but the latest discoveries suggest a more  cosmopolitan distribution during their early evolution.  Tyrannosaurs more derived than Eotyrannus, exhibit a purely Asian or North American distribution, which indicates an increasing Laurasian-Gondwanan provincialism during the final stages of the Age of Dinosaurs (Brusatte et al., 2010).

References:

Averianov, A., Krasnolutskii, S., Ivantsov, S. 2010. A new basal coelurosaur (Dinosauria: Theropoda) from the Middle Jurassic of Siberia. Proceedings of the Zoological Institute RAS 314, 1: 42–57.

Brusatte SL, Norell MA, Carr TD, Erickson GM, Hutchinson JR, et al. (2010) Tyrannosaur paleobiology: new research on ancient exemplar organisms. Science 329: 1481–1485. doi: 10.1126/science.1193304

Fiorillo AR, Tykoski RS (2014) A Diminutive New Tyrannosaur from the Top of the World. PLoS ONE 9(3): e91287. doi:10.1371/journal.pone.0091287

Loewen MA, Irmis RB, Sertich JJW, Currie PJ, Sampson SD (2013) Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans. PLoS ONE 8(11): e79420. doi:10.1371/journal.pone.0079420

RAUHUT, O. W. M., MILNER, A. C. and MOORE-FAY, S. (2010), Cranial osteology and phylogenetic position of the theropod dinosaur Proceratosaurus bradleyi (Woodward, 1910) from the Middle Jurassic of England. Zoological Journal of the Linnean Society, 158: 155–195. doi: 10.1111/j.1096-3642.2009.00591.x

Xu X., Clark, J.M., Forster, C. A., Norell, M.A., Erickson, G.M., Eberth, D.A., Jia, C., and Zhao, Q. (2006). “A basal tyrannosauroid dinosaur from the Late Jurassic of China”, Nature 439 (7077): 715–718. doi:10.1038/nature04511

Marie Stopes and her legacy as paleobotanist.

Marie Stopes (1880-1958)  by George Bernard Shaw. (LSE Archives Image Record, 1921)

Marie Stopes (1880-1958) photographed by George Bernard Shaw. (LSE Archives Image Record, 1921).

George Bernard Shaw once wrote: “All progress is initiated by challenging current conceptions”. Those words describe exactly what Marie Stopes did during her entire life. Her book,  Married Love (1918), is considered one of the most influential of the 20th century. A dedicated feminist, her views on birth control and contraception drew to her the hostile attentions of conservative forces in British Society, and Stope’s ideas were attacked through an assault of her own character. But in addition to her well-known work on birth control and women’s rights, she was a prolific poet, playwright and a paleobotanist.

Marie Charlotte Carmichael Stopes was born in Edinburgh, Scotland, on October 15, 1880. Her father, Henry Stopes, a brewer, architect and amateur paleontologist and archeologist, amassed the largest private collection of fossils and ancient stone tools in Britain. Her mother, Charlotte Carmichael, wrote British Freewomen: Their Historical Privilege. The book, published in 1894, was a great influence in the early twentieth century British women’s suffrage movement. They were both members of the British Association for the Advancement of Science.

Marie Stopes (From Wikimedia Commons)

Marie Stopes (From Wikimedia Commons)

Just before her twentieth birthday, Marie enrolled at University College London where she studied botany and geology. She graduated with honours after only two years and received the Gold Medal in Botany. At UCL she was employed by Francis Wall Oliver as a postgraduate research assistant on his pteridosperm project with Dukinfield Henry Scott. Shortly after, she went to study at the University of Munich, and received a Ph.D. in palaeobotany in 1904. She was the only female student among 5.000 men. During that time, she worked on the internal anatomy of cycad seed. In August 1904, Marie got her first academic job at the Victoria University of Manchester. She became more interested in Carboniferous coal balls. These concretions of calcite, dolomite, siderite, and pyrite, occur at many localities in northern England and preserved in beautiful anatomical detail the structure of the plants that formed the coal.

In 1907, she convinced the Royal Society to fund an excursion to Japan. During her work, she found what were then the earliest known flowers and fossil insects from the Cretaceous period. In 1910, she was commissioned by the Geological Survey of Canada to determine the age of the Fern Ledges, a geological structure at Saint John, New Brunswick. She proved that the rocks were Carboniferous and not Devonian or Silurian as others had earlier argued (Falcon-Lang, 2008).

In 1957 Marie Stopes was diagnosed with cancer. She died on October 2, 1958.

References:

FALCON-LANG, H.J. & MILLER, R.F. 2007. Marie Stopes and the Fern Ledges of Saint John, New Brunswick. In Burek, C.V. (ed.) The Role of Women in the History of Geology. Special

Falcon-Lang, H.J., 2008. Marie Stopes: Passionate about Palaeobotany. Geology Today, 24: 132-136.

William Garrett, 2007,  Marie Stopes: Feminist, Eroticist, Eugenicist,  Lulu.com.

Stephanie Green (2013). The Public Lives of Charlotte and Marie Stopes. London: Pickering & Chatto.

 

Ecosystem instability in the Late Triassic and the early evolution of dinosaurs.

The Late Triassic Petrified Forest Member of the Chinle Formation (Photo from AASG)

The Late Triassic Petrified Forest Member of the Chinle Formation (Photo from AASG)

Dinosaurs likely originated in the Middle Triassic and the first unequivocal dinosaur fossils are known from the late Carnian, but much about the geological and temporal backdrop of early dinosaur history remains poorly understood. A key question is why early dinosaurs were rare and species-poor at low paleolatitudes throughout the Late Triassic Period, for at least 30 million years after their origin.

The oldest well-dated identified dinosaurs are from the late Carnian (approx. 230 Ma) of the lower Ischigualasto Formation in northwestern Argentina. Similarly, the Santa Maria and Caturrita formations in southern Brazil preserve basal dinosauromorphs, basal saurischians, and early sauropodomorphs. In North America, the oldest dated occurrences of vertebrate assemblages with dinosaurs are from the Chinle Formation, but are less abundant and species rich compared to those from South America. The fact that those assemblages were at moderately high paleolatitudes during the Late Triassic, and the North American assemblages were near the paleoequator supports the hypotheses for a diachronous rise of dinosaurs across paleolatitudes (Irmis et al., 2011).

A reconstructed scene from the Late Triassic (Norian) of central Pangea. (Credit: image from Brusatte, S. L. 2008)

A reconstructed scene from the Late Triassic (Norian) of central Pangea. (Image from Brusatte, S. L. 2008, Dinosaurs, Quercus Publishing, London).

The Late Triassic is marked by a return to the “hothouse” condition of the Early Triassic, with two greenhouse crisis that may also have played a role in mass extinctions and long-term evolutionary trends (Retallack, 2013). The paleoclimate was a very arid with intense evaporation rate. Although there was at least one time of significant increase in rainfall known as the “Carnian Pluvial Event”, possibly related to the rifting of Pangea. Now, a multiproxy study  suggests  that fluctuating aridity in tropical and subtropical Pangea could explain why Triassic dinosaur faunas at low latitudes are restricted to small, slower growing carnivorous forms, whereas large-bodied herbivores, including sauropodomorph dinosaurs, are absent at low paleolatitudes during the Late Triassic “hothouse.” The palynomorphs recovered from sediments of the Chinle Formation indicate a major change from a seed fern-dominated (Alisporites) assemblage with accessory gymnosperms to one dominated by conifers and seed ferns in the lower portion of the Petrified Forest Member. In addition, the extensive charcoal record in the Petrified Forest Member provides evidence of paleo-environmental variability and aridity. 

 

References:

Jessica H. Whiteside, Sofie Lindström, Randall B. Irmis, Ian J. Glasspool, Morgan F. Schaller, Maria Dunlavey, Sterling J. Nesbitt, Nathan D. Smith, and Alan H. Turner. 2015. Extreme ecosystem instability suppressed tropical dinosaur dominance for 30 million years. PNAS: doi:10.1073/pnas.1505252112

Brusatte, S. L., Nesbitt, S. J., Irmis, R. B., Butler, R. J., Benton, M. J., and Norell, M. A. 2010. The origin and early radiation of dinosaurs. Earth-Science Reviews, 101, 68-100

Holz, M., Mesozoic paleogeography and paleoclimates – a discussion of the diverse greenhouse and hothouse conditions of an alien world, Journal of South American Earth Sciences (2015), doi: 10.1016/j.jsames.2015.01.001

Nesbitt,  S. J., Irmis,  R. B, Parker,  W. G. (2007) A critical re-evaluation of the Late Triassic di-nosaur taxa of North America. J Syst Palaeontology 5(2):209243

Sellwood, B.W. & Valdes, P.J. 2006. Mesozoic climates: General circulation models and the rock Record. Sedimentary Geology 190:269–287.

 

The real Jurassic World.

Global paleogeographic reconstruction of the Earth in the late Jurassic period 150 Ma. From Wikimedia Commons

Global paleogeographic reconstruction of the Earth in the late Jurassic period 150 Ma. Credit: Dr Ron Blakey

The transition from Triassic to Early Jurassic is marked by a major biotic crisis in the marine and terrestrial realms. In the oceans, this event eliminated conodonts and nearly annihilated corals, ammonites, brachiopods and bivalves. In land, most mammal-like reptiles and large amphibians disappeared, as well as early dinosaur groups. 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 and the diversification of the cycads.

The Early Jurassic climate was characterized by a global warming, with average summer temperatures that exceeded  35°C in low-latitude regions of western Pangaea where eolian sandstones testify to the presence of vast deserts (Holz, 2015). The early Toarcian Oceanic Anoxic Event  (T-OAE; ∼183 mya) is considered as one of the most severe of the Mesozoic era. It’s associated with a major negative carbon isotope excursion, mass extinction, marine transgression and global warming (Huang, 2014, Ullmann et al., 2014). The T-OAE has been extensively studied in the past three decades although there is no consensus about the causes or triggering mechanisms behind this event.

Painting of a late Jurassic Scene on one of the large island in the Lower Saxony basin in northern Germany (From Wikimedia Commons)

Painting of a late Jurassic Scene on one of the large island in the Lower Saxony basin in northern Germany (From Wikimedia Commons)

After the extinction of many carnivorous crurotarsan lineages (phytosaurs, ornithosuchids, rauisuchians) at the Triassic–Jurassic boundary, theropod dinosaurs increased their diversity and exhibit a greater range of morphological disparity. Sauropodomorphs also achieved a worldwide distribution and become more graviportal and increased their body size. The presence of early armored dinosaurs (thyreophorans) in North America, Asia, and Europe, but their absent from the southern African record, suggests some degree of provinciality in early ornithischian faunas (Brusatte et al., 2010).

By the Mid-Jurassic, Gondwana started to break up in different blocks: Antarctica, Madagascar, India, and Australia in the east, and Africa and South America in the west, with relatively warm sea-surface conditions (26–30◦C) from Mid-Jurassic (∼160Ma) to the Early Cretaceous (∼115Ma) in the Southern Ocean.  There was a drastic climatic decline during the Late Callovian. This decline in temperature lasted about 2.6My and is know as the “Callovian Ice Age”. It has been interpreted in terms of an inverse greenhouse effect, triggered by drawdown of CO2 consequent upon excess carbón burial (Dromart et al, 2003).  The Puchezh-Katunki impact crater in Russia is prior to the Callovian extinction event and is not considered as a factor for this biotic extinction event.

During the Late Jurassic, North America completed its separation from Gondwana, and Gondwana was split into a northern and southern continent by the rift system opening the proto-Indian Ocean. The geological and geochemical record suggest that low-latitude environments were arid and tropical ever-wet conditions were absent. Maximum plant diversity was concentrated at midlatitudes, whith forests dominated by a mixture of conifers, cycadophytes, pteridosperms, ferns, and sphenophytes.

References:

Brusatte, S. L., Nesbitt, S. J., Irmis, R. B., Butler, R. J., Benton, M. J., and Norell, M. A. 2010. The origin and early radiation of dinosaurs. Earth-Science Reviews, 101, 68-100

Holz, M., Mesozoic paleogeography and paleoclimates – a discussion of the diverse greenhouse and hothouse conditions of an alien world, Journal of South American Earth Sciences (2015), doi: 10.1016/j.jsames.2015.01.001

Jenkyns, H. C. (2010), Geochemistry of oceanic anoxic events, Geochem. Geophys. Geosyst., 11, Q03004, doi: 10.1029/2009GC002788.

Sellwood, B.W. & Valdes, P.J. 2006. Mesozoic climates: General circulation models and the rock Record. Sedimentary Geology 190:269–287.

Corwin Sullivan et al. 2014. The vertebrates of the Jurassic Daohugou Biota of northeastern China. Journal of Vertebrate Paleontology, vol. 34, no. 2; doi: 10.1080/02724634.2013.787316

A Permian lagerstätte from Antarctica.

 

Vertebraria solid-stele and polyarch roots colonised by fungal spores (From Slater et al., 2014)

Vertebraria solid-stele and polyarch roots colonised by fungal spores (From Slater et al., 2014)

A lagerstätte (German for ‘storage place’) is a site exhibiting an extraordinary preservation of life forms from a particular era. The term was originally coined by Adolf Seilacher in 1970. One of the most notable  is Burgess Shale in the Canadian Rockies of British Columbia. The site, discovered by Charles Walcott in 1909, highlight one of the most critical events in evolution: the Cambrian Explosion (540 million to 525 million years ago). The factors that can create such fossil bonanzas are: rapid burial (obrution), stagnation (eutrophic anoxia), fecal pollution (septic anoxia), bacterial sealing (microbial death masks), brine pickling (salinization), mineral infiltration (permineralization and nodule formation by authigenic cementation), incomplete combustion (charcoalification), desiccation (mummification) and freezing. The preservation of decay-resistant lignin of wood and cuticle of plant leaves  is widespread, but exceptional preservation also extends to tissues.

The Toploje Member chert of the Prince Charles Mountains preserves the permineralised remains of a terrestrial ecosystem before the biotic decline that began in the Capitanian and continued through the Lopingian until the Permo-Triassic transition (Slater et al., 2014). During the late Palaeozoic and early Mesozoic, Antarctica occupied a central position within Gondwana and played a key role in floristic interchange between the various peripheral regions of the supercontinent.

permian

Singhisporites hystrix, a megaspore with ornamented surface.

The fossil micro-organism assemblage includes a broad range of fungal hyphae and reproductive structures. The macrofloral diversity in the silicified peats is relatively low and dominated by the constituent dispersed organs of arborescent glossopterid and cordaitalean gymnosperms.  The fossil palynological assemblage includes a broad range of dispersed bisaccate, monosaccate, monosulcate and polyplicate pollen. The roots (Vertebraria), stems (Australoxylon) and leaves (Glossopteris) of the arborescent glossopterid exhibited feeding traces caused by arthropods, but the identification is  difficult since plant and arthropod cuticles look similar in thin section. Tetrapods are currently unknown from Permian strata of the Prince Charles Mountains as either body fossils or ichnofossils (McLoughlin et al., 1997, Slater et al., 2014).

Times of exceptional fossil preservation are coincident with mass extinctions, oceanic anoxic events, carbon isotope anomalies, spikes of high atmospheric CO2, and transient warm-wet paleoclimates in arid lands (Retallack 2011). The current greenhouse crisis delivers several factors that can promote exceptional fossil preservation, such as eutrophic and septic anoxia, microbial sealing, and permineralization.

References:

Benton, M.J., Newell, A.J., (2013), Impacts of global warming on Permo-Triassic terrestrial ecosystems. Gondwana Research.

Rees, P.M., (2002). Land plant diversity and the end-Permian mass extinction. Geology 30, 827–830.

Retallack, G., (2011), Exceptional fossil preservation during CO2 greenhouse crises?, Palaeogeography, Palaeoclimatology, Palaeoecology 307: 59–74.

Slater, B.J., et al., (2014), A high-latitude Gondwanan lagerstätte: The Permian permineralised peat biota of the Prince Charles Mountains, Antarctica, Gondwana Research. http://dx.doi.org/10.1016/j.gr.2014.01.004

Seilacher, A., (1970) “Begriff und Bedeutung der Fossil-Lagerstätten: Neues Jahrbuch fur Geologie und Paläontologie“. Monatshefte (in German) 1970: 34–39.

Alcide d’Orbigny and the beginning of foraminiferal studies.

Alcide_Dessalines_d'Orbigny_1802

Alcide Dessalines d’Orbigny , 1802. From Wikimedia Commons

During the eighteenth and nineteenth centuries, Paris was a busy place for science. In 1794 the Reign of Terror ended with the establishment of a new government that was more supportive of the sciences. The old Royal Botanical Garden and the affiliated Royal Museum were reorganized as the Muséum national d’histoire naturelle. The new institution fostered many brilliant scientists, including Cuvier, Lamarck, and St. Hilaire. Among those remarkable men was Alcide Dessalines d’Orbigny, considered the founder of micropaleontology and biostratigraphy. He worked in natural history, geology, paleontology, anthropology, linguistics, taxonomy and systematics.

Alcide d’Orbigny was born in Couëron (Charente-Maritime) on September 6th, 1802. In his early youth, he developed a life interest in the study of a group of microscopic animals that he named ‘Foraminifera’ and established the basis of a new science, micropaleontology. He started at an early age working with his father, a doctor, who introduced him to the study of microscopic shells they collected from La Rochelle, a major port on the coast of France. However, Bartolomeo Beccari, was the first to study these tiny shells that could only be observed under the microscope. Beccari analysed in detail the outer and inner structure of the shell, recognising the concamerations and the coiled structure, and attributed these organisms to microscopic ‘Corni di Ammone’, continuing with the enduring confusion between ammonites and foraminifera that started in 1565 when Conrad Gesner described the nummulites collected in the surroundings of Paris. Also Giovanni Bianchi (known by the pseudonym Jaco Planco) in his work De conchis minus notis’ (1739) describes numerous microforaminifera that are found in abundance on the shoreline of Rimini and assigns them the name ‘Corni di Ammone’.

Cover of De conchis minus notis and foraminifera of Rimini’s seaside figured by Bianchi (1739, Table I) and attributed by the author to microscopic specimens of ‘Cornu Ammonis’.

Cover of De conchis minus notis and foraminifera of Rimini’s seaside figured by Bianchi (1739, Table I) and attributed by the author to microscopic specimens of ‘Cornu Ammonis’.

On November 7, 1825, d’Orbigny presented to the Académie des Sciences, the results of his observations in a work entitled ‘Tableau méthodique de la classe des Céphalopodes’. It’s clear that d’Orbigny also considered this group of  microscopic shells as belonging to the Cephalopods. But he was the first to divide the Cephalopods into two zoological orders:  the ‘Siphonifères‘ with intercameral siphon and ‘Foraminifères’ characterized by openings (or foramina) located in the septa separating two consecutive chambers. To illustrate his work, d’Orbigny prepared 73 plates of drawings and made models of 100 of his foraminiferal species that he sculpted in a very fine limestone.

There is a long gap between the publication of his pioneering work and his other works dedicated to foraminifera because of his long journey to South America documented in the nine volumes of his ‘Voyage dans l’Amérique Méridionale’ (1835–1847). In 1835, Félix Dujardin discovered that foraminiferans were not cephalopods, but single-celled organisms. This important discovery led d’Orbigny to exclude the foraminifera from the Cephalopods. In a work published in 1839, he traced the history of foraminiferal studies and considered them as a class for the first time, dividing the history of their study in four periods culminating with the revelation of their unicellular nature.

Operculina, showing the details of d’Orbigny’s drawings intended for the Tableau.

Operculina, showing the details of d’Orbigny’s drawings intended for the Tableau.

In the volume dedicated to the recent foraminifera collected in South America he pointed out the influence of currents, temperature and depth on their distribution patterns. In Mémoire sur les foraminifères de la craie blanche du bassin de Paris published in 1840, d’Orbigny demonstrated that foraminifera could be used for classifying geological strata.

D’Orbigny‘s legacy was extraordinary with thousands of species described, the occurrences of fossils documented chiefly in France, as well as his outstanding Le Voyage dans l’Amérique méridionale published between 1835-1847, and covering the biology, ethnology, anthropology, paleontology, and other aspects of Chile, Peru, Argentina, Uruguay, and especially Bolivia.

In 1853, Napoleon III created the Chair of Paleontology in the Muséum national d’Histoire naturelle in his honour. After his death on June 30, 1857, the collection of d’Orbigny, which includes more than 14,000 species and over 100,000 specimens not counting innumerable foraminifera stored in assorted glass bottles, was auctioned by his family. The collection was bought by the Muséum National d’Histoire Naturelle, in 1858 and registered in the catalogue of the Paleontology Laboratory of this institution.

 

References:

d’Orbigny, A. 1826. Tableau méthodique de la classe des Céphalopodes. Annals des Sciences Naturelles, 1st Series, 7: 245-314.
Dujardin, F. 1835a. Observations sur les Rhizopodes et les Infusoires, Comptes Rendus, de l’Académie des Sciences, 1: 338-340.

Heron-Allen, E. (1917) Alcide d’Orbigny, his life and his work. Journal of the Royal Microscopic Society, ser. 2, 37, 1–105, 433–4.

Seguenza G. 1862. Notizie succinte intorno alla costituzione geologica dei terreni terziarii del distretto di Messina. Messina: Dalla Stamperia di Tommaso Capra. 84 pp.

Vénec-Peyré, M-T, 2004, Beyond frontiers and time: the scientific and cultural heritage of Alcide d’Orbigny (1802–1857), Marine Micropaleontology 50, 149 – 159.

The Middle Permian mass extinction.

The Kapp Starostin Formation, Festningen section, Spitsbergen. The uppermost of the 3 yellow limestone beds records the Middle Permian mass extinction (Credit: Photographer: Dierk Blomeier. For David P.G. Bond and colleagues, GSA Bulletin, 2015.)

The Kapp Starostin Formation, Festningen section, Spitsbergen. The uppermost of the 3 yellow limestone beds records the Middle Permian mass extinction (Photo Credit: Dierk Blomeier. For David P.G. Bond and colleagues, GSA Bulletin, 2015.)

Extinction is the ultimate fate of all species. The fossil record indicates that more than 95% of all species that ever lived are now extinct. Individuals better adapted to environments are more likely to survive and when a species does fail, it is called a background extinction. Occasionally extinction events reach a global scale, with many species of all ecological types dying out in a near geological instant. These are mass extinctions. They were originally identified in the marine fossil record and have been interpreted as a result of catastrophic events or major environmental changes that occurred too rapidly for organisms to adapt.  Mass extinctions are probably due to a set of different possible causes like basaltic super-eruptions, impacts of asteroids, global climate changes, or continental drift.

George Cuvier, the great French anatomist and paleontologist, was the first to suggested that periodic “revolutions” or catastrophes had befallen the Earth and wiped out a number of species. But under the influence of Lyell’s uniformitarianism, Cuvier’s ideas were rejected as “poor science”. The modern study of mass extinction did not begin until the middle of the twentieth century. One of the most popular of that time was “Revolutions in the history of life” written by Norman Newell in 1967.

The fossil record shows that biodiversity in the world has been increasing dramatically for 200 million years and is likely to continue. The two mass extinctions in that period (at 201 million and 66 million years ago) slowed the trend only temporarily. Genera are the next taxonomic level up from species and are easier to detect in fossils. The Phanerozoic is the 540-million-year period in which animal life has proliferated. Chart created by and courtesy of University of Chicago paleontologists J. John Sepkoski, Jr. and David M. Raup.

Biodiversity in the fossil record.  (From Wikimedia Commons)

Over the last 3 decades, mass extinction events  have become the subject of increasingly detailed and multidisciplinary investigations. In 1982, Jack Sepkoski and David M. Raup used a simple form of time series analysis at the rank of family to distinguish between background extinction levels and mass extinctions in marine faunas, and identified five major extinction events in Earth’s history: at the end of the Ordovician period, Late Devonian, End Permian, End Triassic and the End Cretaceous. These five events are know as the Big Five. The most recently identified mass extinction occurred during the Middle Permian, about  262 million years ago, and it was first recognised in the marine realm as a turnover among foraminifera, with fusulinaceans among the principal casualties. The crisis also affected numerous other shallow-marine taxa, including corals, bryozoans, brachiopods, bivalves and ammonoids. Until now, all detailed studies have focused on equatorial sections, especially those of South China. That extinction coincide with the Emeishan large igneous province. But, new data indicates that at the same time there was two severe extinctions amongst brachiopods in northern boreal latitudes in the Kapp Starostin Formation of Spitsbergen, an island roughly 890 km north of the Norwegian mainland.

Fusulinids from the Topeka Limestone  (Upper Carboniferous of Kansas, USA) From Wikimedia Commons

Fusulinids from the Topeka Limestone (Upper Carboniferous of Kansas, USA) From Wikimedia Commons

The Kapp Starostin Formation contains cool-water boreal faunas that include abundant siliceous sponges, brachiopods, and bryozoans. The widespread and near-total loss of carbonates across the Boreal Realm also suggests a role for acidification in the crisis.  This extinction predates the end-Permian mass extinction, because a subsequent recovery of brachiopods and especially bivalves is seen in the Late Permian. This post-extinction fauna disappears 10 m below the top of the Kapp Starostin Formation and thus fails to survive until the end of the Permian (Bond et al., 2015). This is a true mass extinction because the new data suggest that about 50 per cent of all marine species died during the event.

Oceanic oxygen depletion represents a potent cause of extinction in marine settings, and is often linked with volcanic activity, warming, and transgression. However,  the role of anoxia in the wider Capitanian extinction scenario remains enigmatic. Volcanically induced effects are multiple and include acidification.

brachi

Brachiopods from the Kapp Starostin Formation (Image adapted from Bond et al., 2015)

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 foraminifera, planktonic coccolithophores, pteropods and other molluscs,  echinoderms, corals, and coralline algae. 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. But, recently, a variety of trace-element and isotopic tools have become available to infer past seawater carbonate chemistry.

Undoubtedly, the proximity of the End Permian extinction, makes difficult to determine if these events are separate or are part of a the same event.

References:

David P.G. Bond, Paul B. Wignall, Michael M. Joachimski, Yadong Sun, Ivan Savov, Stephen E. Grasby, Benoit Beauchamp and Dierk P.G. Blomeier, 2015, An abrupt extinction in the Middle Permian (Capitanian) of the Boreal Realm (Spitsbergen) and its link to anoxia and acidification, Geological Society of America Bulletin, doi: 10.1130/B31216.1

Wignall, P.B., Bond, D.P.G., Kuwahara, K., Kakuwa, Y., Newton, R.J., and Poulton, S.W., 2010, An 80 million year oceanic redox history from Permian to Jurassic pelagic sediments of the Mino-Tamba terrane, SW Japan, and the origin of four mass extinctions: Global and Planetary Change, v. 71, p. 109–123, doi:10.1016/j.gloplacha .2010.01.022.

Wignall, P.B., Bond, D.P.G., Newton, R.J., Haas, J., Hips, K., Wang, W., Jiang, H.-S., Lai, X.-L., Sun, Y.-D., Altiner, D., Védrine, S., and Zajzon, N., 2012, The Capitanian (Middle Permian) mass extinction in western Tethys: A fossil, facies and δ13C study from Hungary and Hydra Island (Greece): Palaios, v. 27, p. 78–89, doi:10.2110/palo.2011.p11-058r.

The long reign of terror

ferwen:

A post written by me and Jan Freedman about the fascinating history of the “Terror birds”.

Originally posted on TwilightBeasts:

Something has survived.

Bold capital letters spell out the above chilling sentence on the back cover to Michael Crichton’s sequel to Jurassic Park. No blurb. No description of the novel. Those three words say enough.

That short, simple, yet powerful sentence could be used for one of the most famous events in geological history: the K-T extinction. This is now formally known as the K-Pg extinction and heralds the end of the Cretaceous Period and the beginning of the Paleogene Period. It still marks the same asteroid impact that happened 66 million years ago and the end of the non-avian dinosaurs. But something has survived. The avian dinosaurs we see every single day: birds.

In Paleogene park: something has survived.

This may seem a little over the top. But we are not talking about blue tits, or blackbirds. There were once bigger avian dinosaurs running extremely…

View original 1,934 more words

Ocean acidification and the end-Permian mass extinction

 

Permian Seafloor Photograph by University of Michigan Exhibit Museum of Natural History.

Permian Seafloor
Photograph by University of Michigan Exhibit Museum of Natural History.

About one third of the carbon dioxide released by anthropogenic activity is absorbed by the oceans. But the CO2 uptake lowers the pH and alters the chemical balance of the oceans. This phenomenon is called ocean acidification, and is occurring at a rate faster than at any time in the last 300 million years (Gillings, 2014; Hönisch et al. 2012). 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, pteropods and other molluscs,  echinoderms, corals, and coralline algae. Rapid additions of carbon dioxide during extreme events in Earth history, including the end-Permian mass extinction (252 million years ago) and the Paleocene-Eocene Thermal Maximum (PETM, 56 million years ago) may have driven surface waters to undersaturation.

Flow chart summarizing proposed cause-and-effect relationships during the end-Permian extinction (From Bond and Wignall, 2014)

Flow chart summarizing proposed cause-and-effect relationships during the end-Permian extinction (From Bond and Wignall, 2014)

The end-Permian extinction is the most severe biotic crisis in the fossil record, 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 occurred about 252 million years ago (Ma) during an episode of global warming.  The cause or causes of the Permian extinction remain a mystery but new data indicates that the extinction had a duration of 60,000 years and may be linked to massive volcanic eruptions from the Siberian Traps. The same study found evidence that 10,000 years before the die-off, the ocean experienced a pulse of light carbon that most likely led to a spike of carbon dioxide in the atmosphere. Volcanism and coal burning also contribute gases to the atmosphere, such as Cl, F, and CH3Cl from coal combustion, that suppress ozone formation.

Image that shows field work in the United Arab Emirates. Credit: D. Astratti

Image that shows field work in the United Arab Emirates. Credit: D. Astratti

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. But, recently, a variety of trace-element and isotopic tools have become available to infer past seawater carbonate chemistry. The boron isotope composition of carbonate samples obtained from a shallow-marine platform section at Wadi Bih on the Musandam Peninsula, United Arab Emirates, allowed to reconstruct seawater pH values and atmospheric pCO2 concentrations and obtain for the very first time, direct evidence of ocean acidification in the Permo-Triassic boundary. The evidence indicates that the first phase of extinction was coincident with a slow injection of carbon into the atmosphere, and ocean pH remained stable. During the second extinction pulse, however, a rapid and large injection of carbon caused an abrupt acidification event that drove the preferential loss of heavily calcified marine biota (Clarkson et al, 2015).

The increasing evidence that the end-Permian mass extinction was precipitated by rapid release of CO2 into Earth’s atmosphere is a valuable reminder for an immediate action on global carbon emission reductions.

 

References:

Clarkson MO, Kasemann SA, Wood RA, Lenton TM, Daines SJ, Richoz S, Ohnemueller F, Meixner A, Poulton SW, Tipper ET. Ocean acidification and the Permo-Triassic mass extinction. Science, 2015 DOI: 10.1126/science.aaa0193

Feng, Q., Algeo, T.J., Evolution of oceanic redox conditions during the Permo-Triassic transition: Evidence from deepwater radiolarian facies, Earth-Sci. Rev. (2014), http://dx.doi.org/10.1016/j.earscirev.2013.12.003

Hönisch, A. Ridgwell, D. N. Schmidt, E. Thomas, S. J. Gibbs, A. Sluijs, R. Zeebe, L. Kump, R. C. Martindale, S. E. Greene, W. Kiessling, J. Ries, J. C. Zachos, D. L. Royer, S. Barker, T. M. Marchitto Jr., R. Moyer, C. Pelejero, P. Ziveri, G. L. Foster, B. Williams, The geological record of ocean acidification. Science 335, 1058–1063 (2012).

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

Seth D. Burgess, Samuel Bowring, and Shu-zhong Shen, High-precision timeline for Earth’s most severe extinction, PNAS 2014, doi:10.1073/pnas.1317692111

 

The Megafauna extinction in South América.

 

Megatherium americanum Cuvier, 1796. Museo Argentino de La Plata.

Megatherium americanum Cuvier, 1796. Museo Argentino de La Plata.

During the Pleistocene and the 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. Multiple explanatory hypotheses have been proposed for this event: climatic change, over hunting, habitat alteration, and the introduction of a new disease. Traditionally, the focus of research and debate has been on the Eurasian and North American extinctions. In North America, two mammalian orders (Perissodactyla, Proboscidea) were eliminated completely. At the species level, the extinction was total for mammals larger than 1000 kg and greater than 50% for size classes between 1000 and 32 kg. Early observations confirm that extinctions could be severe even in relatively climatically stable regions where the vegetation changed little. In South America the event was  more severe, with the loss of 50 megafaunal genera. Three orders of mammals disappeared (Notoungulata, Proboscidea, Litopterna), as did all megafaunal xenarthrans and at the species level, the extinction was total for mammals larger than 320 kg (Koch and Barnosky, 2006).

“Descuartizando un gliptodonte. Escenas de la vida del hombre primitivo” (Quartering a glyptodont. Scenes from the life of primitive man). Painting by Luis de Servi. Museo de la Plata).

“Descuartizando un gliptodonte. Escenas de
la vida del hombre primitivo” (Quartering a
glyptodont. Scenes from the life of primitive man). Painting by Luis de Servi, Museo de la Plata.

Before the Great American Biotic Interchange, about 3 million years ago, the largest mammals in South America were mainly endemic notoungulates, litopterns and xenarthrans. But, during the interchange, many other megamammals and large mammals arrived to South America. The late Pleistocene in this region is first characterized by a rapid cooling. During the Pleistocene-Holocene transition pollen sequences suggest a change to sub-humid climatic conditions. In addition to rapid climate change, the extinctions are seen as the result of habitat loss, reduced carrying capacity for herbivores, resource fragmentation or disturbances in the co-evolutionary equilibrium between plants, herbivores, and carnivores. The death event of the gomphothere population in Águas de Araxá (Brazil)  about 55,000 years ago, is probably an example of individuals that were suffering with the climate changes during the Late Pleistocene.

Paleontological and archaeological data indicate that extinctions seem more common after the human arrival and during the rapid climate change between 11.200 and 13.500 years. This pattern suggests that a synergy of human impacts and rapid climate change—analogous to what is happening today — may enhance extinction probability (Prado et al., 2015).

 

References:

J.L. Prado et al. (2015). “Megafauna extinction in South America: A new chronology for the Argentine Pampas.” Palaeogeography, Palaeoclimatology, Palaeoecology 425: 41–49

Alroy, John. (2001). “A Multispecies Overkill Simulation of the End-Pleistocene Megafaunal Mass Extinction.” Science 292:1893-1896

Koch PL, Barnosky AD (2006) Late Quaternary extinctions: State of the debate. Annu Rev Ecol Evol Syst 37:215–250.

Prescott GW, Williams DR, Balmford A, Green RE, Manica A. (2012) Quantitative global analysis of the role of climate and people in explaining late Quaternary megafaunal extinctions. Proc. Natl Acad. Sci. USA 109,45274531

Barnosky AD, Lindsey EL.(2010) Timing of Quaternary megafaunal extinction in South America in relation to human arrival and climate change