Brief introduction to Paleobiology of South American titanosaurs.

 

Argentinosaurus huinculensis reconstruction at Museo Municipal Carmen Funes, Plaza Huincul, Neuquén, Argentina. PLoS ONE. From Wikimedia Commons.

Argentinosaurus huinculensis reconstruction at Museo Municipal Carmen Funes, Plaza Huincul, Neuquén, Argentina. PLoS ONE. From Wikimedia Commons.

Titanosaurus were a diverse group of sauropod dinosaurs represented by more than 30 genera, which included all descendants of the more recent common ancestor of Andesaurus  and Saltasaurus (Wilson and Upchurch, 2003). They were important terrestrial herbivores during the Jurassic and the Cretaceous periods. The group exhibits a worldwide distribution and  some of them, were the largest animals to ever walk the Earth: Argentinosaurus, Futalognkosaurus, and Puertasaurus surpassed lengths of 30m and masses of 70 tons.

The discoveries in Patagonia of embryos, eggs (Chiappe et al., 1998, 2001; Salgado et al., 2005; García et al., 2010) and exceptionally articulated specimens show the importance of the South American record for understanding the phylogeny and paleobiology of titanosaurs.

Paleoenvironmental reconstruction of the egg-bearing lower section of the Anacleto Formation at Auca Mahuevo and Los Barreales localities. From Garrido 2010

Paleoenvironmental reconstruction of the egg-bearing lower section of the Anacleto Formation at Auca Mahuevo and Los Barreales localities. From Garrido 2010

The hundreds of eggs containing embryos found in the outcrops of the Anacleto Formation at Auca Mahuevo and Los Barreales corroborated the hypothesis that sauropods were oviparous. The eggs were relatively small (10–25 cm of diameter) and were found  in excavated nests. The embryos from Auca Mahuevo present an ‘egg-tooth’-like structure which is more frequent in altricial birds (García, 2007a, 2008). If we assume that titanosaurs followed a sequence of ontogenetic stages similar to modern birds, these embryos would correspond with the stage 36-37, within the 42 prenatal stages established for birds.

The titanosaur embryos discovered in Auca Mahuevo are exclusively represented by cranial material. Comparing the skull of adults titanosaurs with the embryos from Auca Mahuevo, it seem evident that the Patagonian dinosaurs experienced a deep ontogenetic modification in this part of the skeleton.

Ontogenetic variation in titanosaurian skull morphology. From García et al, 2014.

Ontogenetic variation in titanosaurian skull morphology: aof, antorbital fenestra; en, external nares; f, frontal; j, jugal; l, lacrimal; mx, maxilla; o, orbit; paof, preantorbital fenestra; pmx, premaxilla; qj, quadratojugal; vn, ventral notch. From García et al, 2014.

The rostral portion of the embryonic skull never surpasses 50% of the total skull length while adult sauropods possess a relatively elongated skull. The premaxillae of  the embryos have extremely short nasal processes contrary to those of adult titanosaurs. It’s possible that the remodeling of the premaxillae in the ontogeny has implicated the elongation of the nasal process as well, which in turn would be related to the ontogenetic retraction of the external nares (García et al, 2014). The type of teeth is basically similar in the embryos and those of the few known adult titanosaur skulls, which may be indicative of the same basic diet.

The brain morphology shows a tendency to the reduction of the midbrain and the olfactory tract and bulbs. Titanosaurs also exhibit a reduction of the anterior semicircular canal of the inner ear and a robustness of the labyrinth in comparison with other sauropods.

Shoulder and pelvic girdle architecture of titanosaurs suggests a broader posture than that other sauropods, which is related to a shift in the specific muscular attachments that would counteract the wide posture of the limbs (García et al, 2014).

The ichnological record offers valuable information about different strategies of titanosaur locomotion and behavior. Most of the trackways are parallel and show the same direction of travel which is indication that titanosaurs moved in social groups.

References:

GARCÍA, Rodolfo A. et al. PALEOBIOLOGY OF TITANOSAURS: REPRODUCTION, DEVELOPMENT, HISTOLOGY, PNEUMATICITY, LOCOMOTION AND NEUROANATOMY FROM THE SOUTH AMERICAN FOSSIL RECORD, doi:10.5710/AMGH.16.07.2014.829. Ameghiniana, [S.l.], jul. 2014. ISSN 1851-8044

Sellers WI, Margetts L, Coria RA, Manning PL (2013) March of the Titans: The Locomotor Capabilities of Sauropod Dinosaurs. PLoS ONE 8(10): e78733. doi:10.1371/journal.pone.0078733

The early history of ammonite studies in Italy.

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Ammonites figured by Aldrovandi on his Musaeum Metallicum.

Since antiquity, ammonites has been associated with myths, legends, religion and even necromancy. You can find reference to these fossils in the works of Emilio Salgari, Sir Walter Scott, Friedrich Schiller and Johann Wolfgang von Goethe.

From the sixteenth to the late eighteenth centuries, the study of ammonites in Italy was crucial in the debate about the real nature of fossil remains. Leonardo describes the ammonites of the Veronese mountains in the code Hammer (formerly Codex Leicester), folio 9, where he identified these fossils as lithified remains of organisms.

Ulisse Aldrovandi describes several specimens of ammonites in his Musaeum Metallicum.  Aldrovandi supported the idea of the inorganic origin of fossils, although he often compared them with existing animals. He recognized some resemblance between ammonites and snakes so he used the term ‘Ophiomorphites’ (or snake-shaped stone).

Ammonites illustration of the Metallotheca Vaticana of Michele Mercati.

Ammonites illustration of the Metallotheca Vaticana of Michele Mercati. Two examples of the ammonites described: Calliphylloceras and Phylloceras

In 1574, Michele Mercati organises the famous Metallotheca Vaticana, where describes several ammonites. But he fully embraces the inorganic interpretation of fossils, a real setback with respect to the pioneering hypothesis previously formulated by Leonardo da Vinci. Mercati treats the fossils with he generic term ‘Lapides idiomorphoi’ (stones equipped with proper shape).

In the seventeenth century, the Italian painter Agostino Scilla  compiled an enormous body of evidence, well reasoned and convincing, in favour of the organic nature of fossils found on hills and mountains (Romano, 2014). . However, there is no mention of ammonites is his work. Paolo Silvio Boccone (1633–1704) a Sicilian naturalist and botanist, also supported of the organic nature of fossils. In ‘Recherches et Observations Naturelles’ (1674), he wrote that ammonites – at that time called ‘Corne d’Ammone’ or ‘Corne de Belier’-  represent models (internal) while the original shells of organisms must have  been ‘calcined’ or ‘pulverised’.

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’.

In the first half of the eighteenth century, Bartolomeo Beccari began to study tiny shells that could only be observed under the microscope and classified these organisms as microscopic ‘Corni di Ammone’, continuing with the enduring confusion between cephalopods 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’. This confusion between cephalopods and foraminifera persisted until the French naturalist Alcide d’Orbigny, after 6 years of analysis, arrived to the correct conclusion that these microscopic organisms are a distinct order to which he gave the name of Foraminifera.

References:

Marco Romano, From petrified snakes, through giant ‘foraminifers’, to extinct cephalopods: the early history of ammonite studies in the Italian peninsula, Historical Biology 2014, http://dx.doi.org/10.1080/08912963.2013.879866

Vai, G.B. and Cavazza,W. (Eds) 2003. Four Centuries of the Word Geology, pp. 1–315. Ulisse Aldrovandi 1603 in Bologna. Minerva Edizioni; Bologna.

The Megaraptor mystery.

 

A. Cranial reconstruction of Megaraptor namunhuaiquii. B. skull of Dilong paradoxus. Scale bars equal 2 cm. From Porfiri et al. 2014.

A. Cranial reconstruction of Megaraptor namunhuaiquii. B. skull of Dilong paradoxus. Scale bars equal 2 cm. From Porfiri et al. 2014.

The Cretaceous beds of Patagonia posses the most comprehensive record of  non-avian theropods  from Southern Hemisphere. Megaraptora  is a clade represented by Megaraptor, Orkoraptor and Aerosteon, and characterized by the formidable development of their manual claws on digits I and II and the transversely compressed and ventrally sharp ungual of the first manual digit (Novas et al, 2013).

For years, Megaraptor has been alternatively interpreted as belonging to different theropod lineages: as basal coelurosaurians (Novas,1998), basal tetanurans (Calvo et al.,2004; Smith et al., 2008), and allosauroids closely related with carcharodontosaurids (Smith et al., 2007; Benson et al., 2010; Carrano et al., 2012).

The main reason for so many different interpretations is the incomplete nature of most available megaraptorid skeletons and the little information about their cranial anatomy. But the partially preserved skeleton of a juvenile specimen of Megaraptor namunhuaiquii allows to make for the first time a reconstruction of the skull and body of megaraptorids.

Right maxilla of Megaraptor namunhuaiquii in medial view. Scale bar 3 cm. From Porfiri et al. 2014.

Right maxilla of Megaraptor namunhuaiquii in medial view. Scale bar equal 3 cm. From Porfiri et al. 2014.

The data gathered from the specimen indicates that Megaraptorids had an elongated skull, with a gracile snout bearing small teeth, a gracile S-shaped neck, and a very wide and deep thorax, with gastralia similar in size to dorsal ribs. The pectoral girdle supported elongate and robust forelimbs, with large and sharp unguals on digits I and II, and the hindlimbs were gracile and slender.

Based on that information, the researchers found that Megaraptor and related taxa  are nested within Coelurosauria and Tyrannosauroidea.  They  found 14 synapomorphies between megaraptorans and  tyrannosauroids like several foramina on the premaxillary body, extremely long and straight prenarial process of the premaxilla, incisiviform premaxillary teeth with a D-shaped cross-section, and supratemporal fossae separated by a sharp sagittal median crest on frontals.

The study also shows that tyrannosaurs followed two distinct trajectories in the northern and southern continents. While in megaraptorids the forelimbs became powerful and with large-clawed hands (Calvo et al., 2004), in tyrannosaurids the overall trend was towards forelimb reduction (Brusatte et al., 2010b). However, both evolutionary trends present a common pattern which is the reduction of the third manual digit (Porfiri et al. 2014)

 

References:

Porfiri, J. D., Novas, F. E., Calvo, J. O., Agnolín, F. L., Ezcurra, M. D. & Cerda, I. A. 2014. Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation. Cretaceous Research 51: 35-55.

Benson, R.B.J., Carrano, M.T., Brusatte, S.L., 2010. A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic. Naturwissenschaften 97, 71-78.

Novas, F.E., 2009. The Age of Dinosaurs in South America. Indiana University Press, Bloomington, pp. 1-536

Novas, F.E., 1998. Megaraptor namunhuaiquii gen. et. sp. nov., a large-clawed, Late Cretaceous Theropod from Argentina. Journal of Vertebrate Paleontology 18, 4-9.

The Late Quaternary megafauna extinction: the human factor

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Mammuthus primigenius, Royal British Columbia Museum. From Wikipedia Commons

During the Pleistocene and the early Holocene,  most of the terrestrial megafauna became extinct. It was a deep global-scale event. Multiple explanatory hypotheses have been proposed for this event: climatic change, over hunting, habitat alteration, the introduction of a new disease and an extra-terrestrial impact.

There’s no evidence to support the last two hypothesis, but the patterns exhibited by the Late Quaternary megafauna extinction (LQE) indicated a close link with the geography of human evolution and expansion. This relation and the extinction magnitude is particularly strong in Australia and the Americas. South America exhibits high extinction levels, forming a strong contrast to sub-Saharan Africa where the extinction level was minimal in spite of similar glacial–Holocene climate changes (Sandom et al, 2014).

Fossil Toxodon on display at Bernardino Rivadavia Natural Sciences Museum.

Fossil Toxodon on display at Bernardino Rivadavia Natural Sciences Museum.

Although most Australian extinctions occurred prior to the LQE, it has been argued that modern humans caused the Australian megafauna extinctions either via fire-driven vegetation changes  or hunting.

In North America,  early observation confirms that extinctions could be severe even in relatively climatically stable regions where the vegetation changed little.

Eurasia shows a more complicated story, where human palaeobiogeography alone accounts for 64%  of the variation in extinction, while some data pointed the climate change as the main cause in the decline of late Pleistocene megafaunal.

The case of Africa fits well to the extinction pattern expected from hominin palaeobiogeography.  Also, the current low diversity in large mammals in many continental areas could be considered as an anthropogenic phenomenon, not a natural one, with important implications for nature management (Sandom et al, 2014)

Jean-Baptiste Lamarck(1744- 1829) and  Jacques Boucher de Crèvecœur de Perthes (1788 - 1868) (From Wikimedia Commons)

Jean-Baptiste Lamarck(1744- 1829) and Jacques Boucher de Crèvecœur de Perthes (1788 – 1868) (From Wikimedia Commons)

In the nineteenth century, french naturalist Jean-Baptiste Lamarck  suggested that humans had caused past extinctions, but Lyell rejected his ideas because he believed the extinctions occurred before humans were present. But after visiting stratigraphic excavations in the Somme River valley conducted by  Boucher de Perthes, Lyell wrote, “That the human race goes back to the time of the mammoth and rhinoceros (Siberian) and not a few other extinct mammals is perfectly clear.…”

Other authors like Alfred Russell Wallace and Louis Agassiz argued for mass glaciation as the cause of past extinctions.

Today, the debate remains although the new evidence indicate that human impacts were essential to precipitate the event.

References:

Sandom C, Faurby S, Sandel B, Svenning J-C. 2014 Global late Quaternary megafauna extinctions linked to humans, not climate change. Proc. R. Soc. B 281: 20133254. http://dx.doi.org/10.1098/rspb.2013.3254

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, 4527– 4531. (doi:10.1073/pnas. 1113875109)

Grayson DK. 1984. Nineteenth-century explanations of Pleistocene extinctions: a review and analysis. See Martin & Klein 1984, pp. 5–39

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

Mary Somerville, Queen of Science.

 

(From Wikimedia Commons)

Mary Somerville (1780- 1872) (From Wikimedia Commons)

Mary Somerville, née Mary Fairfax, was born on December 26, 1780,  in Jedburgh Scotland. She has been called  “Queen of Nineteenth Century Science.”  She was also the first English geographer. Her book “Physical Geography” (1848) was the first textbook on the subject in English and her most popular work. It was published three years after the first volume of Alexander von Humboldt’s “Cosmos”.

She had virtually no formal education but she had a very inquisitive mind. Her interest in mathematics was encouraged by her uncle, Dr. William Somerville, who later became her father in law.

In 1807, she was forced to married to Captain Samuel Greig and went to live to London. Her husband died three years later and Mary returned to Scotland and began to study astronomy and mathematics.  In 1811 she won a prize for her solution to a problem in the  journal “The Mathematical Repository.”

She married to her cousin William Somerville in 1812. He was an army doctor and unlike her first husband encouraged her to continuing writing and studying science.  The couple moved to London where they  became members of the scholarly and literary society of the time.

She was a friend of John Herschel, Charles Lyell, Alexander von Humboldt, William Buckland, Lord Henry Brougham,  and Roderick  and Charlotte Murchison. In her autobiography, Mary Somerville wrote about Charlotte: “Mrs Murchison was an amiable accomplished woman, drew prettily and what was rare at the time she had studied science, especially geology and it was chiefly owing to her example that her husband turned his mind to those pursuits in which he afterwards obtained such distinction.”

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Self-portrait by Mary Somerville, Somerville College, University of Oxford

She presented a paper entitled “The Magnetic Properties of the Violet Rays of the Solar Spectrum” to the Royal Society in 1826.

In 1827, Lord Brougham asked her to translate La Place’s “Traité de Mécanique céleste” for the Society for the Diffusion of Useful Knowledge. She not only translated but she added explanations and illustrations to the text. The book was a success and became a text for young mathematicians at Trinity College.

In 1833, she and Caroline Herschel were elected honorary members of the Royal Astronomical Society, the first time women had won that recognition.  Her second book, “The Connection of the Physical Sciences” was published in 1834.

At the age of sixty eight she published “Physical Geography”. The book was dedicated to her mentor John Herschel. In the first page of “Physical Geography” she explains her aim in her scientific writings by quoting Francis Bacon: “No natural phenomenon can be adequately studied in itself alone, but to be understood must be considered as it stands connected with all of nature”.

In “Physical Geography”, she included geology and the distribution of animal and vegetable life. She also sought to understand the various transformation processes involved.

She signed a petition presented to the University of London in 1862 praying that women might be allowed to sit for degree examinations, but the petition was rejected.

In 1869 she was awarded with the first gold medal of the Royal Geographical Society and published her last scientific book: Molecular and Microscopic Science. She died three years later, on November 28 in Naples, Italy.

Mary Somerville was an outstanding scientist and her scientific writings contributed to popularize science, one of the most important cultural projects of Victorian Britain.

 

 

References:

Kathryn A. Neeley, Mary Somerville: Science, Illumination, and the Female Mind, Cambridge University Press, 2001

BUREK, C. V. & HIGGS, B. (eds) The Role of Women in the History of Geology. Geological Society, London, Special Publications, 281, 1–8. DOI: 10.1144/SP281.1.

Buckland, Adelene: Novel Science : Fiction and the Invention of Nineteenth-Century Geology, University of Chicago Press, 2013.

Marie Sanderson and Mary Somerville, Mary Somerville: Her Work in Physical, Geography, Geographical Review Vol. 64, No. 3 (July 1974), pp. 410-420.

Palynological reconstruction of the Antarctic Cretaceous-Paleocene climate.

Artist’s impression of the eastern flank of the Antarctic Peninsula during theMaastrichtian (Artist: James McKay, University of Leeds.)

Artist’s impression of the eastern flank of the Antarctic Peninsula during the Maastrichtian (From Bowman et al, 2014, Artist: James McKay, University of Leeds.)

Past fluctuations in global temperatures are crucial to understand Earth’s climatic evolution. During the Late Cretaceous the global climate change has been associated with episodes of outgassing from major volcanic events, orbital cyclicity and tectonism before ending with the cataclysm caused by a large bolide impact at Chicxulub, on the Yucatán Peninsula, Mexico.
The Antarctic Peninsula is an area of specific interest to modern and past climatic studies, as it seems particularly sensitive to change (Kemp et al., 2014). Most of the studies are focused on Seymour Island which has one of the most expanded Cretaceous–Paleogene successions known. The K-Pg boundary occurs in the uppermost part of the López de Bertodano Formation, where it is marked by a minor iridium anomaly.

The terrestrial palynomorph record at the López de Bertodano Formation was divided into six phases. The first one contains an assemblage dominated by Nothofagidites spp. and Podocarpidites spp., with aquatic fern spores (Azolla spp., Grapnelispora sp.) and rare freshwater algal spores, suggesting a cool and relatively humid period.

 

Two examples of grains pollen from the Lopez de Bertodano Formation: Podocarpidites sp. (left) and Nothofagidites asperus (right)

Two examples of grains pollen from the Lopez de Bertodano Formation: Podocarpidites sp. (left) and Nothofagidites asperus (right). From Bowman et al, 2014.

In the phase two the increased abundance of Phyllocladidites mawsonii implies a gradual increase in humidity. During phase three, bryophytes began to increase. The phase four is characterised by relatively high abundances of Podocarpidites spp. and relatively low levels of Nothofagidites spp.
The phase 5 is characterised by a rapidly changing sequence of abundance peaks of different taxa, which may indicate a successional turnover in forest composition. The phase six suggests a return to a cool climatic conditions with high abundances of Araucariacites australis and Nothofagidites at the top of the section. It seems that Araucariaceae were capable of surviving long periods of adverse climatic conditions during the Early Pleistocene, but most modern araucarians have subtropical to mesothermal climatic preferences.

The nature of vegetational change in the south polar region suggests that terrestrial ecosystems were already responding to relatively rapid climate change prior to the K–Pg catastrophe. The composition of the terrestrial palynoflora indicates that the Maastrichtian climate fluctuated from cool, humid conditions, through a rapid warming about 2 million years prior to the K–Pg event – which is consistent with the evidence from the marine palynomorph record –  followed by cooling conditions in the earliest Danian.

 

Two examples of spores from the  Lopez de Bertodano Formation: Grapnelispora sp. (left) and Azolla sp.(right).

Two examples of spores from the Lopez de Bertodano Formation: Grapnelispora sp. (left) and Azolla sp.(right). From Bowman et al, 2014.

 

Reference:

Vanessa C. Bowman, Jane E. Francis, Rosemary A. Askinb, James B. Riding, Graeme T. Swindles, Latest Cretaceous–earliest Paleogene vegetation and climate change at the high southern latitudes: palynological evidence fromSeymour Island, Antarctic Peninsula, Palaeogeography, Palaeoclimatology, Palaeoecology, 408. 26-47. 10.1016/j.palaeo.2014.04.018
David B. Kemp, Stuart A. Robinson, J. Alistair Crame, Jane E. Francis, Jon Ineson, Rowan J. Whittle, Vanessa Bowman, and Charlotte O’Brien, A cool temperate climate on the Antarctic Peninsula through the latest Cretaceous to early Paleogene, Geology (2014) doi: 10.1130/G35512.1

 

Lessons from the past: Climate change and the Classic Maya collapse.

 

Temple I on The Great Plaza and North Acropolis seen from Temple II in Tikal, Guatemala. From Wikimedia Commons

Temple I on The Great Plaza and North Acropolis seen from Temple II in Tikal, Guatemala. From Wikimedia Commons

The earth’s climate has already reached a tipping point. Glaciers  from the Greenland and Antarctic Ice Sheets are fading away, dumping 260 billion metric tons of water into the ocean every year. The ocean acidification is occurring at a rate faster than at any time in the last 300 million years, and  the patterns of rainfall and drought are changing and undermining food security which have major implications for human health, welfare and social infrastructure. These atmospheric changes follow an upward trend in anthropogenically induced CO2 and CH4.

The first scientists that explored the relationship between carbon dioxide concentrations in the atmosphere and global warming were Svante Arrhenius and Thomas Chamberlain at the end of the nineteenth century. Now, the current rate of increase of CO2 emissions has no precedent in the geological record and there is no perfect analogue from the past for the temporal evolution of future climate. However, we still can learn from historical and archeological records how societies had responded in the past to the unintended consequences of human action on the environment.

Rainfall record for the Maya region (Kennett et al., 2012)

Human activity took precedence over natural climate change as the driving force behind plant and animal extinctions with the advent of agriculture and the domestication of animals. There are several cases in the past where anthropogenic environmental change has caused the collapse of economic, social and political systems. A good example of that is the collapse of Classic Maya political centers between AD 750 and 1000.

Paleoecological records indicate that the transition to agriculture was a fundamental turning point in the environmental history of Mesoamerica. Tropical forest were reduced by agricultural expansion associated with growing human populations. Also soil loss associated with deforestation and erosion was one of the most consequential environmental impacts associated with population expansion in the Maya lowlands (Kennett, 2013). This environmental crisis ended with the collapse of the Classic Maya society.

Today the most politically unstable countries are also places where environmental degradation affected food production and water supply. Other human societies have succumbed to climate change – like the Akkadians –  while others have survived by changing their behavior in response to environmental change. We have opportunity to protect the future of our own society by learning from the mistakes of our ancestors. International cooperation is one of the keys.  As Trevor Manuel, a South African government minister and co-chair of the Global Ocean Commission stated: “Governments must respond as urgently as they do to national security threats – in the long run, the impacts are just as important”.

 

References:

Kennett, D.J., Beach, T.P., Archeological and environmental lessons for the Anthropocene from the Classic Maya collapse. Anthropocene (2014), http://dx.doi.org/10.1016/j.ancene.2013.12.002

M. Morlighem, E. Rignot, J Mouginot, H. Seroussi, and E. Larour. Deeply incised submarine glacial valleys beneath the Greenland Ice Sheet. Nat. Geosci., 2014

Malcolm McMillan, Andrew Shepherd, Aud Sundal, Kate Briggs, Alan Muir, Andrew Ridout, Anna Hogg, Duncan Wingham. Increased ice losses from Antarctica detected by CryoSat-2. Geophysical Research Letters, 2014; DOI: 10.1002/2014GL060111

D. J. Lunt, H. Elderfield, R. Pancost, A. Ridgwell, G. L. Foster, A. Haywood, J. Kiehl, N. Sagoo, C. Shields, E. J. Stone, and P. Valdes, Introduction: Warm climates of the past: a lesson for the future? (2013), Phil. Trans. R. Soc. A 28, doi: 10.1098/rsta.2013.0146

Mary Anning’s contribution to French paleontology.

 

mary anning cuvier

Portraits of Mary Anning (1799–1847) and Georges Cuvier (1769-1832). From Wikimedia Commons.

Mary Anning was born on Lyme Regis on May 21, 1799.  She 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. 

George Cuvier, the famous French paleontologist also benefited with Mary Anning’s discoveries. He acquired several ichthyosaur specimens and a plesiosaur specimen  found by her. The study of these fossils allowed him to apply his comparative anatomical method and to support his catastrophist theory.

When George Cuvier went to England in 1818, he took the opportunity to examine at the remains of a marine reptile  that had been previously described by Sir Everard Home. The specimen, an ichthyosaur, was unearthed by Joseph and Mary Anning in 1811. Cuvier rapidly managed to get casts and fine specimens of all marine reptiles discovered in England, especially those made in Lyme Regis by the Anning family.

BECHE_Mary_Annings

Sketch of Mary Anning by Henry De la Beche. From Wikimedia Commons.

In December 1823, Mary made another amazing discovery. She found the first complete Plesiosaurus skeleton. She immediately wrote to William Buckland,  the famous English geologist and paleontologist, describing the strange specimen.

The unexpected proportions of the neck, raised the suspicions of Cuvier, who wrote to William Conybeare suggesting that the find was a fake produced by combining fossil bones from different animals. William Buckland and Conybeare sent a letter to Cuvier including anatomical details, an engraving of the specimen and a sketch made by Mary Morland (Buckland’s wife) based on Mary Anning’s own drawings and they convinced Cuvier that this specimen was a genuine find. From that moment, Cuvier treated Mary Anning as a legitimate and respectable fossil collector and cited her name in his publications.

In May 1824, Cuvier sent geologist Constant Prévost to England for an official geological trip, supported by the administration of the Palaeontology Gallery of the Muséum National d’Histoire Naturelle. In June 1824 Prévost – accompanied by Charles Lyell-   went to Lyme Regis and met Mary Anning. He bought a plesiosaur for £10 and sent it to Paris. Cuvier included the  engraving of his plesiosaur in a third edition of his “Discours sur les révolutions de la surface du globe”. 

A sketch of a Plesiosaur by Mary Anning, 1824.

A sketch of a Plesiosaur by Mary Anning, 1824. From original manuscripts held at the Natural History Museum, London. © The Natural History Museum, London

References:

Peggy Vincent, Taquet Philippe, Valentin Fischer, Bardet Nathalie, Falconnet Jocelyn, Godefroit Pascal, Mary Anning’s legacy to French vertebrate palaeontology,  Geological Magazine, January 2014,

The Winter of Our Discontent: short-term cooling following the Chicxulub impact.

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The K-T impact by Don Davis.

The Cretaceous–Paleogene extinction that followed the  Chicxulub impact was one of the five great Phanerozoic  mass extinctions. The impact released an estimated energy equivalent of 100 teratonnes of TNT and produced high concentrations of dust, soot, and sulfate aerosols in the atmosphere. Model simulations suggest that the amount of sunlight that reached Earth’s surface was reduced by approximately 20%.This decrease of sunlight caused a drastic short-term global reduction in temperature. This phenomenon is called “impact winter”.

Cold and darkness lasted for a period of months to years.  Photosynthesis stopped and the food chain collapsed. This period of reduced solar radiation may only have lasted several months to decades. Three-quarters of the plant and animal species on Earth disappeared. Marine ecosystems lost about half of their species while freshwater environments shows low extinction rates, about 10% to 22% of genera.

Three factors can be associated with the impact winter in marine and fresh water enviroments. First, starvation caused by the stop of photosynthesis. Second, the loss of dissolved oxygen. Third, the low temperatures. The flux of organic detritus to the sea floor also

A paleogeographic map of the Gulf of Mexico at the end of the Cretaceous (From Vellekoop, 2014)

Three factors can be associated with the impact winter in marine and fresh water environments. First, starvation caused by the stop of photosynthesis. Second, the loss of dissolved oxygen. Third, the low temperatures. Because the late Cretaceous climate was warm, a major challenge for aquatic organisms, especially in inland waters, may have been the persistence of low temperatures. Additionally, the vapour produced by the impact  could have led to global acid rain and a dramatic acidification of marine surface waters.

Fossil evidence for this impact winter was recovered in the Brazos River region of Texas.  The biostratigraphy of the section presents the Ir anomaly, and impact-related tsunami beds. The age of the outcrops was updated using  planktonic foraminifera and  dinocysts.

The “impact winter”  model is supported by a migration of cool, boreal dinoflagellate species into the subtropic Tethyan realm directly across the K–Pg boundary interval and the ingression of boreal benthic foraminifera into the deeper parts of the Tethys Ocean, interpreted to reflect millennial timescale changes in ocean circulation following the impact (Vellekoop, 2014).

References:

Johan Vellekoop, Appy Sluijs, Jan Smit, Stefan Schouten, Johan W. H. Weijers, Jaap S. Sinningh Damsté, and Henk Brinkhuis, Rapid short-term cooling following the Chicxulub impact at the Cretaceous–Paleogene boundary, PNAS (2014) doi: 10.1073/pnas.1319253111

Douglas S. Robertson, William M. Lewis, Peter M. Sheehan and Owen B. Toon, K-Pg extinction patterns in marine and freshwater environments: The impact winter model, Journal of Geophysical Research: Biogeosciences, JUL 2013, DOI: 10.1002/jgrg.20086.

The Bernissart Dinosaurs.

 

Mounting of the first complete Iguanodon specimen (specimen “Q,” RBINS R51, the holotype of I. bernissartensis) in the St. Georges Chapel. From Wikipedia Commons.

Mounting of the first complete Iguanodon specimen in the St. George’s Chapel. From Wikipedia Commons.

In 1882, Mary Ann Mantell, wife of doctor Gideon Mantell, found large fossilized teeth near to a quarry in Whiteman’s Green,Cuckfield. Her husband, an amateur paleontologist, sent the teeth to Georges Cuvier. At first, Cuvier suggested that the remains were from a rhinoceros, but in a letter from 1824 admitted his mistake and determined that the remains were reptilian and quite possibly belonged to a giant herbivore. A year later, Mantell described them and named them Iguanodon (“iguana tooth”) because their resemblance with  those of living iguanas.

For the  Crystal Palace exhibition in London, in 1854, the Iguanodon was reconstructed as large quadruped resembling a rhinoceros and for more than twenty years, that was the official image of the Iguanodon. But  all that changed on February 28, 1878, when Jules Créteur and Alphonse Blanchard, two  mine workers, accidentally discovered some fossil remains  in a coal mine at Bernissart, Belgium.

Mary Mantell and the lithographed of an Iguanodon teeth.

Mary Mantell and the lithographed of an Iguanodon teeth.

Both miners were put in charge of  the exploration of the gallery. They found more fragmentary bones and teeth. On April, the  fossils were sent to geologist François-Léopold Cornet and  Pierre-Joseph Van Beneden, professor of paleontology at Leuven University. Van Beneden identified the teeth as belonging to the dinosaur Iguanodon. The discovery was communicated to Edouard Dupont, director of the Musée royal d’Histoire naturelle de Belgique (MRHNB).

Almost immediately, Louis De Pauw, head preparer at the MRHNB, went to Bernissart to explore the site. He reported that the walls of the exploration gallery were completely covered by fossil bones, plants, and fishes. To preserve the fossils, De Pauw created a very efficient excavation method: each skeleton was carefully exposed and its position in the mine recorded on plan diagrams. Every skeleton was divided into manageable blocks approximately 1 metre square, protected by a coat of plaster of Paris and then sketched and cataloged  before being transported to Brussels.

Drawing by G. Lavalette in 1883 of Iguanodon bernissartensis discovered in the Sainte-Barbe pit.

Drawing by G. Lavalette in 1883 of Iguanodon bernissartensis discovered in the Sainte-Barbe pit.

In 1879, fourteen  complete skeletons of iguanodontids were recovered, including  two Bernissartia (a dwarf crocodile) skeletons, one “Goniopholis” (larger crocodile) skeleton, two turtles, and innumerable fishes and plant remains.

Louis Dollo, who was an assistant naturalist at the Royal Belgian Institute of Natural Sciences in 1882, devoted himself to the study of the Iguanodons. Between 1882 and 1923, he published many preliminary notes on the Bernissart iguanodonts. He identified Iguanodon as an ecological equivalent of the giraffe with a kangaroo-like posture, using its tail and hind legs tripod-like. 

But in 1980, British paleontologist D. Norman published a monograph on Iguanodon bernissartensis and an analysis of the skeleton revealed that the vertebral column was surrounded by a network of ossified tendons distributed along the spine, which indicates that the more natural pose of the backbone was horizontal. Also, because of the  structure of the pectoral girdle, the ratios of the forelimb and hind limb lengths, the strongly fused carpal bones, and the presence of hoof-like unguals on the middle three digits of the hand, Iguanodons possibly had a quadrupedal posture.

The Bernissart iguanodons, mounted in the MRHNB in the early 1930s. (From Godefroit, 2012)

The Bernissart iguanodons, mounted in the MRHNB in the early 1930s. (From Godefroit, 2012)

After three years of excavations at Bernissart, the Belgian government were faced financial problems and the excavations were stopped. In 1883, the first mounted specimen was exhibited in the interior court of Nassau Palace and in 1891, the iguanodons were transported to the Royal Museum of Natural History in Leopold Park.

During World War I, the German forces that occupied the city reopened the mine and the prominent Otto Jaekel was sent to supervise the excavations.  After the war, further attempts to reopen the mine were hindered by financial problems and were finally stopped in 1921 when the mine was flooded.

References:  

Godefroit, P. , Bernissart Dinosaurs and Early Cretaceous Terrestrial Ecosystems. Indiana University Press (2012)

Sanz, José Luis,  Cazadores de Dragones, Editorial Ariel (2007).