Early studies of South American Fossils.

 

Megatherium americanum, MACN.

Megatherium americanum on display at the MACN.

The first notices of South American fossils were reported by early Spanish explorers. These fossils were interpreted as the remains of an ancestral race of giant humans erased from the face of the Earth by a divine intervention. In the second half of the sixteenth century, Fray Reginaldo de Lizarraga (1540-1609), referred in his writings to those “graves of giants” found in Córdoba, Argentina. In 1760, the English Jesuit Thomas Falkner, discovered the first remains of a glyptodon. He wrote: “I myself found the shell of an animal, composed of little hexagonal bones, each bone an inch in diameter at least; and the shell was near three yards over. It seemed in all respects, except it’s size, to be the upper part of the shell of the armadillo; which, in these times, is not above a span in breadth.” (1774, p. 54-55).  However, the first formal description of a gliptodonte was performed in 1838, by English naturalist Sir Richard Owen.

In 1766, by order of Juan de Lezica y Torrezuri (1709-1783), Mayor of Buenos Aires, fossil remains recovered in Arrecifes, were sent to Spain. Previously to the trip, three surgeons, Matías Grimau, Juan Parán and Ángel Casteli, analyzed the bones to determine if these were humans. In Spain, scholars of the Real Academia de la Historia, stated that the remains were not human, conjecturing that those bones resembled those of a quadruped, and perhaps an Elephant. The scholars were right, the remains in question belonged to mastodons, extinct relatives of elephants.

Portrait of  Manuel Torres by Francisco Fortuny.

Portrait of Manuel Torres by Francisco Fortuny.

In 1787, Fray Manuel de Torres found near the banks of the Lujan River,  the skeletal remains of a gigantic mammal. He carefully documented this extraordinary finding. On April 29, 1787, he sent a letter to the Viceroy Francisco Nicolás Cristóbal del Campo, Marqués de Loreto, with details of his work. In 1789, the specimen was sent to the Cabinet of Natural History in Madrid where was illustrated by Juan Bautista Brú de Ramón (1740-1799). This is the real starting point of paleontological studies in the Rio de la Plata.

In 1795, Philippe-Rose Roume (1724-1804), a French officer, sent Bru’s illustrations to the Institut de France, with a little description of the skeleton. A year later, George Cuvier (1769-1832) published the first scientific work on a South American fossil. He assigned the fossil the scientific name Megatherium americanum. Cuvier also studied fossils from Bolivia, Chile, Colombia, and Ecuador, among which he recognized three morphotypes, designated informally as “mastodonte a dents étroites”, “mastodonte Cordillierès” and “mastodonte humboldien”. Cuvier (1823) later formally named them Mastodon angustidens, Mastodon andium and Mastodon humboldti, respectively (Fernicola et al, 2009).

References:

PASQUALI, Ricardo C  y  TONNI, Eduardo P. Los hallazgos de mamíferos fósiles durante el período colonial en el actual territorio de la Argentina. Ser. correl. geol.[online]. 2008, n.24 [citado  2014-12-08], pp. 35-43 . Disponible en: . ISSN 1666-9479.

Fernicola, J. C., Vizcaino, F, and de Iuliis, G. (2009), ‘The Fossil Mammals collected by Charles Darwin in South America during his travels on board the HMS Beagle’, Revista de la Asociatión Geológica Argentina. 64 (1), 147-59.

Fariña, Richard A.; Vizcaíno, Sergio F.; De Iuliis, Gerry (2013). Megafauna. Giant Beasts of Pleistocene South America. Indiana University Press.

The Anthropocene defaunation process.

 

Richard Owen stands next to the largest of all moa, Dinornis maximus (now D. novaezealandiae). From Wikimedia Commons.

Richard Owen stands next to the largest of all moa, Dinornis maximus (now D. novaezealandiae). From Wikimedia Commons.

In 2000,  Paul Crutzen proposed use the term Anthropocene to designate the last two hundred years of human history and to mark the end of the current Holocene geological epoch. Although there is no agreement on when the Anthropocene started, it has been defined, primarily, by significant and measurable increases in anthropogenic greenhouse gas emissions from ice cores and other geologic features including synthetic organic compounds, radionuclides and ocean acidification.

Another marker for the Anthropocene is the current biodiversity crisis. The term defaunation was created to designate the declining of top predators and herbivores triggered by human activity, that results in a lack of agents that control the components of the ecosystems vegetation.

Global population declines in mammals and birds represented in numbers of individuals per 10,000 km2 for mammals and birds (From Dirzo et al., 2014)

Global population declines in mammals and birds (From Dirzo et al., 2014).

Since the industrial revolution, the wave of animal and plant extinctions that began with the late Quaternary has accelerated. Calculations suggest that the current rates of extinction are 100–1000 times above normal, or background levels. We are in the midst of  the so called “Sixth Mass Extinction”.

Although anthropogenic climate change is playing a growing role, the primary drivers of modern extinctions seem to be habitat loss, human predation, and introduced species (Briggs, 2011). The same drivers that contributed to ancient megafaunal and island extinctions.

SConsequences of defaunation (From Dirzo et al., 2014)

The consequences of defaunation (From Dirzo et al., 2014)

 

One of the most famous and well-documented extinctions come from Madagascar. Pygmy hippos, giant tortoises, and large lemurs went extinct due to human hunting or habitat disturbance.  A very interesting study by Burney et al. (2003) tracked the decline of coprophilous Sporormiella fungus spores in sediments due to reduced megafaunal densities after the human arrival on the island. Another well documented case is the Moa extinction in New Zealand. Recent radiocarbon dating and population modeling suggests that their disappearance occurred within 100 years of first human arrival. A large number of  land birds across Oceania suffered a similar fate beginning about 3500 years ago.

Some biologist predict that the sixth extinction  may result in a 50% loss of the plants and animals on our planet by AD 2100, which would cause not only the collapse of ecosystems but also the loss of food economies, and medicinal resources.

References:

Richard N. Holdaway, Morten E. Allentoft, Christopher Jacomb, Charlotte L. Oskam, Nancy R. Beavan, Michael Bunce. An extremely low-density human population exterminated New Zealand moa. Nature Communications, 2014; 5: 5436 DOI: 10.1038/ncomms6436

Rodolfo Dirzo et al., Defaunation in the Anthropocene, Science 345, 401 (2014); DOI: 10.1126/science.1251817

Braje, T.J., Erlandson, J.M., Human acceleration of animal and plant extinctions: A Late Pleistocene, Holocene, and Anthropocene continuum. Anthropocene (2013), http://dx.doi.org/10.1016/j.ancene.2013.08.003

 

 

The plant fossil record and the extinction events.

Odontopteris lingulata, seed fern from the Late  Late Pennsylvanian to Early Permian. (Image Credit: Taylor et al, 2009)

Odontopteris lingulata, seed fern from the Late Late Pennsylvanian to Early Permian. (Image Credit: Taylor et al, 2009)

Mass extinctions has shaped the global diversity of our planet several times during the geological ages. 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.

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, Frasnian (Late Devonian), Permian, Triassic and Cretaceous. But the plant fossil record reveals a different pattern of major taxonomic extinctions compared with marine organisms. The first of them took place at the Carboniferous-Permian transition, which is interpreted as result of the collapse of the tropical wetlands in Euramerica. The second mass extinction corresponds to the end-Permian event.

Glossopteris sp., seed ferns, Permian - Triassic - Houston Museum of Natural Science (From Wikimedia Commons)

Glossopteris sp., seed ferns, Permian – Triassic – Houston Museum of Natural Science (From Wikimedia Commons)

At the late Carboniferous the characteristic wetland families disappeared (e.g. Flemingitaceae, Diaphorodendraceae, Tedeleaceae, Urnatopteridaceae, Alethopteridaceae, Cyclopteridaceae, Neurodontopteridaceae). The downfall of rainforests probably reflects the complexity of the environmental changes that were taking place during the late Moscovian-early Sakmarian time interval (DiMichele et al., 2006, Sahney et al., 2010). This collapse probably drove the rapid diversification of Carboniferous tetrapods (amphibians and reptiles) in Euramerica (Sahney et al., 2010).

During the end-Permian Event, the woody gymnosperm vegetation (cordaitaleans and glossopterids) were replaced by spore-producing plants (mainly lycophytes) before the typical Mesozoic woody vegetation evolved. The palynological record suggests that wooded terrestrial ecosystems took four to five million years to reform stable ecosystems, while spore-producing lycopsids had an important ecological role in the post-extinction interval.

Schematic illustration comparing the three extinction events analized (From Vajda and Bercovici, 2014)

Schematic illustration comparing the three extinction events analized (From Vajda and Bercovici, 2014)

At the end-Triassic event,  the vegetation turnover in the Southern Hemisphere  consisted in the replacement to Alisporites (corystosperm)-dominated assemblage to a Classopollis (cheirolepidiacean)-dominated one.

The end-Cretaceous biotic crisis had a significant effect on marine and terrestrial faunas, and caused localized loss of species diversity in vegetation. Patagonia shows a reduction in diversity and relative abundance in almost all plant groups from the latest Maastrichtian to the Danian, although only a few true extinctions occurred (Barreda et al, 2013). 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.

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

Two examples of grains pollen: Podocarpidites sp. (left) and Nothofagidites asperus (right)

A key factor for plant resilience is the time-scale: if the duration of the ecological disruption did not exceed that of the viability of seeds and spores, those plant taxa have the potential to recover (Traverse, 1988).

References:

Cascales-Miñana, B., and C. J. Cleal, 2014, The plant fossil record reflects just two great extinction events. Terra Nova. vol. 26, no. 3, pp. 195–200. DOI: 10.1111/ter.12086

Bambach, R.K., Knoll, A.H. and Wang, S.C., 2004. Origination, extinction, and mass depletions of marine diversity. Paleobiology, 30, 522–542.

Mayhew, Peter J.; Gareth B. Jenkins, Timothy G. Benton (January 7, 2008). “A long-term association between global temperature and biodiversity, origination and extinction in the fossil record”. Proceedings of the Royal Society B: Biological Sciences 275 (1630): 47–53.

Sahney, S., Benton, M.J. & Falcon-Lang, H.J. (2010). “Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica” (PDF). Geology 38 (12): 1079–1082. doi:10.1130/G31182.1.

 

Halloween special II: Lovecraft, Paleobotany and The Shadow Out of Time.

Howard Phillips Lovecraft_in_1915_(2)

Howard Phillips Lovecraft in 1915.

Howard Phillips Lovecraft was born on August 20, 1890 in Providence, Rhode Island. He was one of the most influential writers of the twentieth century.  Despite leaving school without graduating, in his writings, evidences an extensive knowledge of archaeology, astronomy, geology, and paleontology. As an amateur astronomer, Lovecraft attended several lectures from leading astronomers and physicists of his time. He  explicitly stated in a letter to a friend that Yuggoth is in fact the then recently discovered Pluto. This was one of the key aspects in Lovecraft’s literature: to reject the old spiritual world and use the advance of science as a source of inspiration.

“The Shadow Out of Time” (1935) was H. P. Lovecraft’s last major story. It’s told from the perspective of Nathaniel Wingate Peaslee, a professor of political economy at Miskatonic University. During five years, this man suffers a bizarre form of amnesia  followed by vivid dreams of aliens cities in ancient landscapes.  Later, Peaslee discovered that a small number of people throughout history suffered the same type of amnesia. They were possessed by the Great Race, a group of cone shaped creatures who developed the technique of swapping minds with creatures of another era with the purpose of learn the secrets of the Universe.

Lepidodendrom leaf cushions preserved in a Mazon Creek nodule. (Taylor et al., 2009)

Lepidodendrom leaf cushions preserved in a Mazon Creek nodule. (Image Credit: Taylor et al, 2009)

Peaslee describes the gardens that surround the cities of his visions with detail. There was calamites, cycads, trees of coniferous aspect, and small, colourless flowers.

Calamites was a genus of tree-sized, spore-bearing plants that lived during the Carboniferous and Permian periods (about 360 to 250 million years ago), closely related to modern horsetails. They reached their peak diversity in the Pennsylvanian and were major constituents of the lowland equatorial swamp forest ecosystems. The Cycadales are an ancient group of seed plants that can be traced back to the Pennsylvanian. Cycads have a stem or trunk that commonly looks like a large pineapple and composed of the coalesced bases of large leaves.  Today’s cycads are found in the tropical, subtropical and warm temperate regions of both the north and south hemispheres.

While angiosperm fossil pollen first appears in the Early Cretaceous, molecular data suggest that the first occurrence was in the early Permian (~275 Ma) to late Triassic (228-217 Ma). Recently, a new study describe six distinct pollen types that have angiosperm-like features from the Triassic of Switzerland.

sigillaria

Transverse section of Sigillaria approximata stem (Image Credit: Taylor et al, 2009)

Peaslee’s visions become more and more vivid:

The far horizon was always steamy and indistinct, but I could see that great jungles of unknown tree-ferns, calamites, lepidodendra, and sigillaria lay outside the city, their fantastic frondage waving mockingly in the shifting vapours.”

Lepidodendron was a tree-like (‘arborescent’) tropical plant, related to the lycopsids. The name of the genus comes from the Greek lepido, scale, and dendron, tree, because of the distinctive diamond shaped pattern of the bark. The name Lepidodendron is a generic name given to several fossil that clearly come from arborescent lycophytes but are difficult to assign to one species. Fossil remains indicate that some trees attained heights in excess of 40 m and were at least 2m in diameter at the base. They were dominant components of swamp ecosystems in the Carboniferous and frequently associated with Sigillaria, another extinct genus of tree-sized lycopsids from the Carboniferous Period. The absence of extensive branching and the structure of the leaf bases are the principal feature that distinguish Sigillaria from other lycopsids (Taylor et al, 2009). Sigillariostrobus is the name assigned to the reproductive organs or cones of Sigillaria. Unlike Lepidodendron cones, which were attached attached individually near the tip of the branches, Sigillaria cones occurred in clusters attached in certain places along the upper stem.

Later, on an expedition to Australia, Peaslee – accompanied by Professor William Dyer, leader of the Miskatonic Antarctic expedition of 1930-1931- discovered a manuscript written by himself eons ago when he was a captive mind of the Great Race.

References:

H. P. Lovecraft, The Dreams in the Witch House and Other Weird Stories, Penguin Books, 2004.

Joshi, S. T. (2001). A dreamer and a visionary: H.P. Lovecraft in his time. Liverpool University Press, 302.

N. Taylor, Edith L. Taylor, Michael Krings: “Paleobotany: The Biology and Evolution of Fossil Plants”. 2nd ed., Academic Press 2009.

Kathy Willis, Jennifer McElwain, The Evolution of Plants, Oxford University Press, 2013

Hochuli, P. A., and Feist-Burkhardt, S.. (2013). Angiosperm-like pollen and Afropollis from the Middle Triassic (Anisian) of the Germanic Basin (Northern Switzerland). Frontiers in Plant Science. 4. doi: 10.3389/fpls.2013.00344

Mignon Talbot and the forgotten women of Paleontology.

 

Sin título

Mignon Talbot  (From Turner et al, 2010)

 

The nineteenth century was the “golden age” of Geology, and women began to play an important role in the advance of this field of science. They collected fossils and mineral specimens, and were allowed to attend scientific lectures, but they were barred from membership in scientific societies. It was common for male scientists to have women assistants, often their own wives and daughters. A good example of that was Mary Lyell (1808–1873), daughter of the geologist Leonard Horner and the wife of eminent geologist Charles Lyell. But for most of men, the participation of women in geology and paleontology was perceived as a hobby.

Mary Anning (1799-1847), was a special case. She was the most famous woman paleontologist of her time, and found the first specimens of what would later be recognized as Ichthyosaurus, the first complete Plesiosaurus, the first pterosaur skeleton outside Germany and suggested that the “Bezoar stones” were fossilized feces. Scientists like William Buckland or Henry de la Beche owe their achievements to Mary’s work. William Buckland himself, persuaded the British Association for the Advancement of Science and the British government to award her an annuity of £25, in return for her many contributions to the science of geology.

Thanks to the pioneer work of these women,the twenty century saw the slow but firm advance of women from the periphery of science towards the center of it. Unfortunately, most of these early female scientists were forgotten and none of them reached the fame of their most illustrious predecessor, Miss Mary Anning.

Podokesaurus holyokensis holotype (From Wikimedia Commons)

Podokesaurus holyokensis holotype (From Wikimedia Commons)

Mignon Talbot was born in Iowa, on August 16, 1869. She studied geology at Ohio State University. In 1904 she received a Ph.D. from Yale and then joined at Mount Holyoke College, where she became Professor of Geology and Geography until her retirement in 1935. During her years at the faculty, she amassed a large collection of invertebrates fossil, but published few technical papers. In 1910, she became the first woman to find and describe a dinosaur: Podokesaurus holyokensis (swift-footed saurian). In 1911, she published a scientific description of the fossil. She wrote: “In a bowlder of Triassic sandstone which the glacier carried two or three miles, possibly, and deposited not far from the site of Mount Holyoke College, the writer recently found an excellently preserved skeleton of a small dinosaur the length of whose body is about 18 cm. The bowlder was split along the plane in which the fossil lies and part of the bones are in o half and part in the other. These bones are hollow and the whole  framework is very light and delicate“.  At the time, she was mentored in her investigation by Richard Swan Lull, who suggested that this dinosaur was insectivorous (although, Talbot identified it as a herbivore at a meeting of the Paleontological Society in December 1910). Unfortunately, in 1916, a fire destroyed the science hall and the only specimen of Podokesaurus holyokensis. She died on July 18, 1950.

Tilly Edinger (Photo,Museum of Comparative Zoology, Harvard University, Cambridge, MA)

Tilly Edinger (Photo,Museum of Comparative Zoology, Harvard University, Cambridge, MA)

Johanna Gabrielle Ottilie  “Tilly” Edinger was born on November 13, 1897 in Frankfurt, Germany. She was the youngest daughter of the eminent neurologist Ludwig Edinger and Dora Goldschmidt. She studied at Universities of Heidelberg, Frankfurt, and Munich. In 1921, she received her Ph. D at the University of Frankfurt. When she was preparing her doctoral dissertation about the palate of the Mesozoic marine reptile Nothosaurus, Edinger encountered a skull with a natural brain cast. Her early research was mostly descriptive and she was influenced by the work of Louis Dollo and Friedrich von Huene. In 1929,  she published Die fossilen Gehirne (Fossil Brains), the book that established Edinger’s membership in the German and international paleontological communities. She briefly worked at British Museum of Natural History after the events that followed the infamous “Kristallnacht” (Night of the Broken Glass). In 1940, with the support of Alfred S. Romer, she moved to Massachusetts to take a position at the Harvard Museum of Comparative Zoology. Shortly after, she was the first and only woman who attend the founding meeting of the Society of Vertebrate Paleontology (SVP). By the early 1950s, she was not only the major contributor to the field of paleoneurology but also the mentor to a younger generation that was following in her footsteps. She died on 27 May 1967 in Cambridge, Massachusetts.

References:

Susan Turner, Cynthia V. Burek and Richard T. J. Moody, Forgotten women in an extinct saurian (man’s) world, Geological Society, London, Special Publications 2010, v. 343, p. 111-153

Buchholtz, Emily A.; Seyfarth, Ernst-August (August 2001), “The Study of “Fossil Brains”: Tilly Edinger (1897–1967) and the Beginnings of Paleoneurology”, Bioscience 51 (8)

Kass-Simon, Gabrielle; Farnes, Patricia; Nash, Deborah, eds. (1999). Women of science : righting the record. Bloomington, Indiana: Indiana Univ. Press.

Talbot, M., 1911, Podokesaurus holyokensis, a new dinosaur of the Connecticut Valley: American Journal of Science, v. 31, p. 469-479

 

The Poetry of the Ice Age.

Joseph Mallord William Turner Source of the Arveron in the Valley of Chamouni Savoy 1816 (Image from The Tate Gallery)

Joseph Mallord William Turner
Source of the Arveron in the Valley of Chamouni Savoy
1816 (Image from The Tate Gallery)

Glaciers occupy a privileged site between narrative and science. Percy Shelley’s “Mont Blanc: Lines Written in the Vale of Chamonix“ (1816) used the landscape as a metaphor to analyze the relationship between the human mind and the universe.

Far, far above, piercing the infinite sky,
Mont Blanc appears,— still, snowy, and serene —
Its subject mountains their unearthly forms
Pile around it, ice and rock; broad vales between
Of frozen floods, unfathomable deeps,
Blue as the overhanging heaven, that spread
And wind among the accumulated steeps.

And of course, Mer de Glace, on the slope of the mountain, is where Victor Frankenstein reunited with his Creature: “…From the side where I now stood Montenvers was exactly opposite, at the distance of a league; and above it rose Mont Blanc, in awful majesty…. The sea, or rather the vast river of ice, wound among its dependant mountains, whose aerial summits hung over its recess….” (Mary Shelley, Frankenstein, 1818)

Johann Wolfgang von Goethe,  one of the world’s greatest poets, was also a great naturalist. More important, he was the very first to believe in an ice age. Jean de Charpentier (1786- 1855)  in Essai sur les glaciers presented Goethe’s theories of glacial transport (Charpentier, 1841, p . v).

Jean Louis Agassiz in 1870 (From Wikimedia Commons)

Jean Louis Agassiz in 1870 (From Wikimedia Commons)

In 1837, Karl Friedrich Schimper, a  German botanist and geologist, wrote a poem to commemorate Galileo’s birthday, Die Eiszeit: fur Freunde gedruckt am Geburtstage Galilei.  The expression Eiszeit—“ice age”— appeared for the first time in this poem. One of its stanzas says:

Last vestige of the primal ice,
more ancient than the Alps!
Primal ice of yore, when the might of frost
buried mountain high even the South,
enveloped mountain and sea alike!

Karl Schimper was born in Mannheim, Germany, on February 15th, 1803. During the summer of 1835, he was studying mosses which were growing on erratic boulders in the alpine upland of Bavaria and came to the conclusion that ice must have been the means of transport for the boulders.

Based on the works of Schimper and de Charpentier,  Louis Agassiz (1801–1873) presented his “Discours de Neuchatel,” at the annual meeting of the Swiss Society of Natural Sciences on July 24, 1837. In this seminal work, he proposed that the Earth had been subject to a past ice age.

References:

Kate Flint, The Victorians and the Visual Imagination, Cambridge University Press, 2000.

Tobias Krüger, Discovering the Ice Ages: International Reception and Consequences for a Historical Understanding of Climate, BRILL, 2013.

A brief introduction to Dinosaur Herbivory.

 

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 (Artist: James McKay, University of Leeds.)

Dinosaurs had diverse feeding mechanisms that strongly influenced their ecology and evolution. Herbivory probably evolved independently in derived silesaurids and various dinosaur groups. Although in the early Late Triassic, dinosaur herbivores were rare, by the early Middle Jurassic until the end of the Cretaceous, they became the dominant vertebrate herbivores.

Herbivory  requires numerous physiological, anatomical, and behavioral adaptations,  including cranial modifications and specialization of the gastrointestinal tract. On the contrary, plants have developed certain features to dissuade herbivores, and evolved to compensate the effects of herbivory by extending growing periods, delaying leaf senescence, and improving nutrient and water availability to surviving leaves (Barret, 2014). Notwithstanding, some plants attract herbivores to enable seed dispersal or pollination, usually by producing fleshy fruits or nectar. The sum of these factors lead to diverse mutualistic interactions between plants and vertebrate herbivores.

Possible interactions between anatomical and physiological traits in herbivorous dinosaurs. From Barret, 2014

Possible interactions between anatomical and physiological traits in herbivorous dinosaurs. From Barret, 2014

The evolution of sauropod herbivory was intimately associated with increased body size and quadrupedal locomotion. In Gondwanan faunas, titanosaurian sauropods were the principal herbivorous dinosaurs.

Several anatomical features enabled sauropods to ingest and digest massive quantities of vegetation (approximately up to 40 kg per day), much of it probably low in nutritional quality. Their long necks helped them to reach vegetation inaccessible to other herbivores, and their large bodies enabled the slower passage of plants through the gut with longer periods of gut fermentation, which allowed that enzymes chemically degrade very hard plants or large amounts of foliage, without employ other mechanical methods for breaking down food (although, is very common found sauropod skeletons with gastroliths).

Differences in body size, skull morphology, neck length, mobility, and dental features probably allowed coexisting sauropods to target different food sources and feed in distinct ways. Bonitasaura, a small sauropod from the Late Cretaceous of Argentina, may have been adapted for feeding on harder vegetation close to the ground. This is very different to the usual image of sauropods browsing high in the treetops and may have been a common feeding strategy among sauropods (Brusatte, 2012).

Triassic cycadophytes from Argentina: A) Pseudoctenis spatulata Du Toit; B) Taeniopteris Brongniart . From Cúneo et al, 2010

Triassic cycadophytes from Argentina: A) Pseudoctenis spatulata Du Toit; B) Taeniopteris Brongniart . From Cúneo et al, 2010

There were profound changes in floral composition and structure during the Mesozoic, including the rise of ferns, cycadophytes, and conifers during the Triassic and Jurassic, followed by the sharp decline of cycadophyte abundance and richness in the Early Cretaceous, and the origin and subsequent diversification of angiosperms. All these floral events have been linked to changes in dinosaur ecology, but currently the evidence for coevolutionary interactions between plants and dinosaurs is weak.

Reference:

Paul Barret, Paleobiology of Herbivorous Dinosaurs, Annu. Rev. Earth Planet. Sci. 2014. 42:207–30, DOI: 10.1146/annurev-earth-042711-105515

Brusatte SL, Benton MJ, Ruta M, Lloyd GT. 2008. The first 50 Myr of dinosaur evolution: macroevolutionary pattern and morphological disparity. Biol. Lett. 4:733–36

Langer MC, Ezcurra MD, Bittencourt JS, Novas FE. 2010. The origin and early evolution of dinosaurs. Biol. Rev. 85:55–110

Martínez RN, Sereno PC, Alcober OA, Colombi CE, Renne PR, et al. 2011. A basal dinosaur from the dawn of the dinosaur era in southwestern Pangaea. Science 311:206–10

Tiffney BH. 1992. The role of vertebrate herbivory in the evolution of land plants. Palaeobotanist 41:87–97

Brief introduction to the Toarcian oceanic anoxic event.

Early Jurassic reconstruction (From Wikimedia Commons)

Early Jurassic reconstruction (From Wikimedia Commons)

In Earth history there have been relatively brief intervals when a very significant expansion of low-oxygen regions occurred throughout the world’s oceans. In mid-1970s the discovery of black shales at many drill sites from the Atlantic, Indian, and the Pacific Ocean led to the recognition of widespread anoxic conditions in the global ocean spanning limited stratigraphic horizons. In 1976, Schlanger and Jenkyns termed these widespread depositional black shale intervals “Oceanic Anoxic Events” (Takashima et al, 2006). This was one of the greatest achievement of the DSDP (Deep Sea Drilling Project).

The Toarcian OAE, Weissert OAE, OAE 1a, and OAE 2 are global-scale anoxic events associated with prominent positive excursions of δ13C and worldwide distribution of black shales. Two models have been proposed to explain it: the stagnant ocean model (STO model) and the expanded oxygen-minimum layer model (OMZ model). Deep-water warming may have also contributed to a decrease in oxygen solubility in the deep ocean and may have triggered the dissociation of large volumes of methane hydrate buried in sediments of the continental margins.

Time scale [Gradstein et al., 2005] illustrating the stratigraphic position and nomenclature of OAEs (From Jenkyns, 2010).

Time scale [Gradstein et al., 2005] illustrating the stratigraphic position and nomenclature of OAEs (From Jenkyns, 2010).

In the Jurassic and Cretaceous oceans, the calcareous nannoplankton was the most efficient rock-forming group, for that reason the characterization of calcareous nannofloras in OAE intervals are used to improve our understanding of the marine ecosystem and biological processes such as photosynthesis (biological pump) and biomineralisation (carbonate pump) that affect the organic and inorganic carbon cycle, as well as adsorption of atmospheric CO2 in the oceans (Erba, 2013). Calcareous nannoplankton represent a major component of oceanic phytoplankton, ranging in size  from 0.25 to 30 μm. The first records are from the Late Triassic. Their calcareous skeletons can be found in fine-grained pelagic sediments in high concentrations and the biomineralization of coccoliths is a globally significant rock-forming process.

The early Toarcian Oceanic Anoxic Event  (T-OAE; ∼183 mya) in the Jurassic Period 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 general consensus about the causes or triggering mechanisms behind this event. During the peak of the perturbation corresponding to this event, calcareous nannofossils collapsed.

 

Schizosphaerella punctulata (adapted from Clémence, 2014)

Schizosphaerella punctulata (adapted from Clémence, 2014)

Schizosphaerella is a nannofossil of uncertain biological affinities with a large globular test with two interlocking sub-hemispherical valves formed from a geometric arrangement of equidimensional crystallites with an average value of 10.5 μm in the major axis. During the Early Jurassic, suffered a major drop in abundance, and a reduction in size. The average values drastically decrease down to 8.3 μm around the interval corresponding to the T-OAE. This event is know as ‘Schizosphaerellid crisis’, ‘calcareous nannofossil crisis’ or ‘disappearance event’ (Erba 2004, Clémence, 2014). Four main hypotheses have been proposed to account for the nannoplankton biocalcification crisis through the early Toarcian: (1) a strong stratification of the water column and the development of an oxygen-minimum zone; (2) the discharge of low salinity arctic waters through the Laurasian seaway; (3) high values in atmospheric pCO2; and (4) a rapid warming (Clémence, 2014).

Results from the Paris Bassin as in other localities indicates that the increasing greenhouse conditions may have caused acidification in the oceans, hampering carbonate bio-mineralisation, and provoking a dramatical loss in the CO2 storage capacity of the oceans. The CO2 induced changes in seawater chemistry likely affected the calcification potential of both neritic and pelagic systems, as evidenced by drops of platform-derived carbonate accumulation and drastic reductions in size of the main carbonate producer Schizosphaerella.

The better understanding of the Mesozoic ocean-climate system and the formation of OAEs would help us to predict environmental and biotic changes in a future greenhouse world.

References:

Marie-Emilie Clémence: Pattern and timing of the Early Jurassic calcareous nannofossil crisis.  Palaeogeography, Palaeoclimatology, Palaeoecology, 2014/doi: 10.1016/j.palaeo.2014.06.022.

Elisabetta Erba, Calcareous nannofossils and Mesozoic oceanic anoxic events, Marine Micropaleontology 52 (2004) 85 – 106

Bown, P.R., Lees, J.A., Young, J.R., (2004), Calcareous nannoplankton evolution and diversity through time. In: Thierstein, H.R., Young, J.R. (Eds.), Coccolithophores From Molecular Processes to Global Impact. Springer, Amsterdan, pp. 481–508.

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

 

Ancient Greek theater and the past Mediterranean climate.

Theatre of Dionysos, Athens, Greece. From Wikimedia Commons

Theatre of Dionysos, Athens, Greece. From Wikimedia Commons

Ancient manuscripts, paintings and plays  provide valuable information to help modern scientists to reconstruct the climate of the past. The information recovered from these ancient sources are mainly focused on extreme events with a great impact in society like droughts or floods, and other less dramatic conditions. For instance, the analysis of the writings of scholars and historians in Iraq during the Islamic Golden Age between 816 and 1009 AD revealed an increase of cold events in the first half of the 10th century  immediately before the Medieval Warm Period. It’s also possible analyze  volcanic eruptions in the past by studying the colouration of the atmosphere in paintings that portrayed sunsets in the period 1500–1900 AD.

The analysis of the writings of Aeschylus, Sophocles, Euripides and Aristophanes during the Golden Age (5th and 4th centuries B.C) provides a valuable insight into the Mediterranean climate of the time.

A vase illustrating a Lenaia celebration. (Image from the Naples National Archaeological Museum, Italy.)

A vase illustrating a Lenaia celebration. (Image from the Naples National Archaeological Museum, Italy.)

Halcyon days occur in Greece, especially in Attica, and in southeastern Europe in the middle of winter between 15 January and 15 February, during which the halcyon birds were supposed to lay their eggs . The Halcyon days has its origins in an ancient myth. Halcyon was the daughter of Aeolus, the God of the Winds. She was married to Ceyx the King of Thessaly. After his brother died, Ceyx embarked on a voyage across the sea to consult the oracle of Apollo. He died in a storm and Halcyon threw herself into the waters to reunite with him. The gods amazed by her love and devotion, transformed Ceyx and Halcyon into kingfishers. Then, Zeus decreed that the winter sea stay calm for a period of 14 days so that the birds could keep their eggs safe in the winter.

Euripides in Medea wrote about the pleasant and harmonious climate: “Men celebrate in song how Aphrodite, filling her pail at the streams of the fair flowing Cephisus, blew down upon the land temperate and sweet breezes“.

The comedies of Aristophanes, often invoke the presence of the halcyon days. In Birds he mentioned the ‘skiadeion’, a kind of umbrella used solely to protect people from the sunlight rather than rain. Also, the drawn from the paintings on vessels showing that the clothes worn in Lenaia (an annual Athenian festival with a dramatic competition) were not designed for rainy weather.

 

 

 

Reference:

Christina Chronopoulou, A. Mavrakis, ‘Ancient Greek drama as an eyewitness of a specific meteorological phenomenon: indication of stability of the Halcyon days.’ Weather, DOI: 10.1002/wea.2145

Domínguez-Castro F, Vaquero JM, Marín M et al. 2012. How useful could Arabic documentary sources be for reconstructing past climate? Weather 67(3): 76–82. doi:10.1002/wea.83

Zerefos CS, Gerogiannis VT, Balis D, Zerefos SC, Kazantzidis A. 2007. Atmospheric effects of volc anic eruptions as seen by famous artists and depicted in their paintings. Atmos. Chem. Phys. 7: 4027–4042.

Haeckel and the legacy of early radiolarian taxonomists.

Ernst Haeckel and his assistant Nicholas Miklouho-Maclay, photographed in the Canary Islands in 1866. From Wikimedia Commons.

Ernst Haeckel and his assistant Nicholas Miklouho-Maclay, photographed in the Canary Islands in 1866. From Wikimedia Commons.

In the nineteenth century, the study of radiolarians was the domain of German scientists. These early German workers laid the foundation for all future work with this group of organisms, both living and fossil.

Christian Gottfried Ehrenberg (1795–1876) made a series of special monographs from 1838 to 1875 and named the group Polycystina. He described a half-dozen species of both Spumellaria and Nassellaria. Ehrenberg’s microscopic researches also included diatoms and  fossil cyst of dinoflagellates. His book “Mikrogeologie” (1854) has many illustrations of a great number of microfossils.

Many of Ehrenberg’s early radiolarian species descriptions come from Neogene biosiliceous sediments of Italy. Despite the fact he worked before the concept of type specimens for species had become established, Ehrenberg not only documented most of his species with published figures, but preserved the original material and microscope preparations for future generations of scientists to study (Lazarus 2014).

Christian Gottfried Ehrenberg and Johannes Müller. Source: Museum für Naturkunde, Berlin and Humboldt Universität, Berlin.

Christian Gottfried Ehrenberg and Johannes Müller. Source: Museum für Naturkunde,
Berlin and Humboldt Universität, Berlin.

Johannes Müller (1801–1858), one of the most famous German biologists of his generation, published three substantial papers on radiolarians. He described a total of 69 species, including both polycystines and acantharians. As a professor on Berlin’s Medical Faculty, he  influenced a great number of students. Among them were Ernst Haeckel (1834-1919) and Rudolf Virchow (1821-1902).

Like  Ehrenberg, Müller never believed that species had evolved over time, and he died before the publication of Charles Darwin’s Origin of Species.

After Müller’s death, E. Haeckel focused on the group last studied by his friend and professor: the radiolarians. With a copy of Müller’s paper and a wealth of material available off Messina, Haeckel began the first of his major studies of nature.

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In 1862, Haeckel made the first complete  classificatory system for the Radiolaria and produced finely detailed drawings of them in his book: “Die Radiolarien”. He dedicated this monograph to Müller. In this work, he  included polycystines, phaeodarians and acantharians.

In 1864, Haeckel sent to Darwin, two folio volumes on radiolarians. The gothic beauty of these drawings impressed Darwin. He wrote to Haeckel that “were the most magnificent works which I have ever seen, and I am proud to possess a copy from the author”.

Haeckel became the most famous champion of Darwinism in Germany and he was so popular that, previous to the First World War, more people around the world learned about the evolutionary theory through his work “Natürliche Schöpfungsgeschichte” (The History of Creation: Or the Development of the Earth and its Inhabitants by the Action of Natural Causes) than from any other source. His study of radiolarians established Haeckel as a young scientist of importance. Later, Haeckel focused his research in the more general aspects of evolution and development.

Ernst Haeckel's ''Kunstformen der Natur'' (1904), showing Radiolarians of the order Stephoidea. From Wikimedia Commons.

Ernst Haeckel’s ”Kunstformen der Natur” (1904), showing Radiolarians of the order Stephoidea. From Wikimedia Commons.

Along with many other scientists, Haeckel was asked by the managers of the Challenger Expedition soon after the ship’s return to examine and report on the expedition’s collections specifically for radiolarians, sponges and jellyfish. Haeckel’s Report on Radiolaria took him almost a decade.

His final report was published in 1887 and summarized and subsumed all prior work on radiolarians up to that point, including, for example, many of Ehrenberg’s species and genera. But while Ehrenberg eschewed higher taxa, except for a minimally adequate number of obvious, high-level groupings, Haeckel did the opposite thing and introduced a much enlarged and substantially more complex higher-level taxonomy for the radiolaria generating numerous duplicate lower-level categories, including species, which led to an unusually large percentage of Haeckel’s named species being ignored as redundant or meaningless (Lazarus, 2014).

In 1904, Haeckel published his master work “Kunstformen der Natur” (Art Forms of Nature) and helped to popularize radiolarians among scientists and the general audience.

Radiolaria illustration from the Challenger Expedition 1873–76. From Wikimedia Commons.

Radiolaria illustration from the Challenger Expedition 1873–76. From Wikimedia Commons.

Karl Alfred Ritter von Zittel (1839-1904), was a prominent German paleontologist.  His early research was in minerals and petrography. In 1876, he published “Ueber einige fossile Radiolarien aus der norddeutschen Kreiden. Zeitschrift der deutschen geologischen Gesellschaft” where he described Mesozoic radiolarians in northern Germany. Many of the species names proposed by Zittel are still valid today.

David Rüst (1831–1916) published 10 papers on radiolarians. Although he was not the first to describe Mesozoic radiolarians, he was certainly the most prolific describing over 900 new species of fossil radiolarians from Mesozoic and even Palaeozoic rocks from Europe and North America.

 

References:

David Lazarus, The legacy of early radiolarian taxonomists, with a focus on the species published by early German workers, Journal of Micropalaeontology 2014, v.33; p3-19.

Robert J. Richards, The Tragic Sense of Life: Ernst Haeckel and the Struggle over Evolutionary Thought, (2008), University of Chicago Press.