Mary Anning’s contribution to French paleontology.

 

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.

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. 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.

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.

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 in the St. George’s Chapel. From Wikipedia Commons.

In 1822, 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.

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.

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)

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).

Poirot and the mysterious case of the Permian extinction.

 

Siberian flood-basalt flows in Putorana, Taymyr Peninsula.(From Earth science: Lethal volcanism, Paul B. Wignall, 2011, Nature 477, 285–286 )

On the winter of 1934 during travel across Europe on board of the Orient Express Hercules Poirot, the famous Belgian detective faced the most intriguing and defiance case of his career: the murder of Mr. Ratchett. During the investigation Poirot reveals the real identity of the victim and the horrible crime that he committed in the past. Poirot also discovered that everyone on the coach had motives to kill Ratchett. With the help of Mr. Bouc, an acquaintance of Poirot and director of the company operating the Orient Express, Poirot arrives at two conclusions: first, a stranger boarded the train and murdered Ratchett; second, that all 13 people on the coach were complicit in the murder.

When Agatha Christie created this complicated plot in 1934, she never heard about the most perfect and yet mysterious death scene of all time: the Permo-Triassic extinction event. But that wasn’t her fault. Despite Cuvier’s  notable remarks about massive periodic catastrophes or “revolutions” found in the fossil record, scientists only started to focus on the massive extinctions in the middle of the twentieth century.

Western Pangea during the Late Permian (From Scotesse, 2010)

The end-Permian extinction is the most severe biotic crisis in the fossil record. This great crisis occurred about 252 million years ago (Ma) during an episode of global warming. The extinction had a duration of 60,000 years. For years there was a great debate about the cause or multiple causes of this catastrophic event, so Douglas Erwin, in 1993,  used Poirot’s second hypothesis to explain the Permo-Triassic event.  He called this hypothesis “The Murder on the Orient Express Model”. But what forces converged to wipe out almost 97% of species on Earth?

At the Permian Period, almost all land masses were reunited in one single supercontinent: Pangea, which stretched from the northern to the southern pole. Due to the formation of this supercontinent, the habitable marine area was reduced and the climate showed severe extremes with great seasonal fluctuations between wet and dry conditions. Ten thousand years before the extinction event there was a spike of carbon dioxide in the atmosphere, that  led to ocean acidification and warmer temperatures.

The permian triassic boundary at Meishan, China (Photo: Shuzhong Shen)

Massive volcanic eruptions in Siberia covered more than 2 millions of km 2 with lava flows, releasing more carbon in the atmosphere and high amounts of fluorine and chlorine increasing the climatic inestability. Warmer oceans, possibly had melted frozen methane located in marine sediments which pushed the global temperatures to higher levels.

Recently, a study analyzing rock samples from Meishan, China, pointed a new suspect: a microbe, called Methanosarcina. This microbe is related to a superexponential burst in the carbon cycle and a spike the availability of nickel. But, some scientist remain sceptical about when Methanosarcina actually evolved.

We are close to find the answer to the Great Dying, but thus far, the best possible explanation for this severe extinction still is: THEY ALL DID IT!

References:

Agatha Christie, Murder on the Orient Express (1934), Collins Crime Club.

Douglas H. Erwin, Extinction: How Life on Earth Nearly Ended 250 Million Years Ago, Princeton University Press, 2006

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

Daniel H. Rothman, Gregory P. Fournier, Katherine L. French, Eric J. Alm, Edward A. Boyle, Changqun Cao, and Roger E. Summons (2014) “Methanogenic burst in the end-Permian carbon cycle,” PNAS doi: 10.1073/pnas.1318106111