The Age of Fucoids

Chondrites bollensis. Originally was designated as a “fucoid”. Osgood (1975)

The 19th century marks the beginning of the systematic study of trace fossils. In his classic review about the history of Ichnology, Osgood (1975)  recognize three different stages: the “Age of Fucoids”, the”Age of Controversy” and the” Development of the Modern Approach” (1).

The first one correspond to the middle 19th Century, when the botanical point of view, about the origin of the trace fossils was dominant. The second, implied the rupture of this paradigm using analogies with modern traces and correspond to the later part of the 19th century. The “Development of the Modern Approach” started with the establishment of the Senckenberg Laboratory and extended from 1925 to 1953.

More recently, Pemberton et al. (2007) and Baucon (2010) added two more stages to Osgood’s classical view: an “Age of  Naturalists” (2) and a “Modern Era of Ichnology” extending from 1953 to the present day.(3)

Adolphe Brongniart. From WikimediaCommons.

According to Osgood, the “Age of Fucoids” began in 1823 when the French botanist Adolphe Brongniart published Observations sur les Fucoïdes, et sur quelques autres plantes marines fossiles.

Adolphe Brongniart  is considered one of the most prominent botanists of the 19th century and he earned the title of “father of Paleobotany”. He established the botanical genus “Fucoides” which included a variety of fossils like Cruziana and Rusophycus.

Cruziana, fossil trails of Trilobites. From Wikimedia Commons

Rusophycus (the resting trace of trilobite) from the Upper Cambrian of Poland. From Wikimedia Commons

Among the authors that described trace fossils during that time as the remains of fossil plants are  Paul Lebesconte, Oswald Heer and Gaston de Saporta. Osgood attributed to this botanical perspective the slow development of invertebrate ichnology.

The legacy of the “Age of Fucoids” included the establishment of some ichnogenera that are still valid like Scolicia, Paleodictyon, Rhizocorallium and Zoophycus.

Swedish paleontologist Alfred Nathors. From Wikimedia Commons.

The “Age of Fucoids” ended in 1881 when the Swedish paleontologist, Alfred Nathorst, refuted almost all the fucoids as plant fossils. J. W. Dawson, Edward Hitchcock, J. F. James and C. J. Sane also questioned the classification of Fucoids. That was the beginning of the “Age of Controversy”.

References:

(1) Osgood R.G., 1975 – The history of invertebrate ichnology. In:Frey R.W. (ed.), The Study of Trace Fossils. Springer Verlag, New York: 3-12

(2) Baucon, A. 2010. Da Vinci’s Paleodictyon: the fractal beauty of traces. Acta Geologica Polonica, 60 (1), 3–17.

(3) Pemberton et al., 2007b – The Antecedents of Invertebrate Ichnology in North America: the Canadian and Cincinnati Schools. In: Miller III, W. (ed.), Trace Fossils. Concepts, Problems, Prospects. Elsevier, AmsterdamOxford: 14-31.

Da Vinci and the birth of Ichnology.

Leonardo da Vinci: Self-portrait. From WikimediaCommons.

Leonardo di ser Piero da Vinci was born on April 15, 1452 in Vinci, a town in the lower valley of the Arno River. He is the archetype of the Renaissance Man: artist, architect, musician, mathematician, engineer, inventor, anatomist, naturalist and geologist. A true polymath. He is considered one of the greatest painters of all time. His paintings are cultural icons. But there was a less known aspect of Leonardo’s talent: the Ichnology. In 2010, Andrea Baucon published a paper entitled: Leonardo da Vinci, the Founding Father of Ichnology, where he explores the many contributions of Leonardo to this field of science (1).

During the Renaissance, many intellectuals showed interesting in the study of traces, like Ulisse Aldrovandi the man who coined the term “geology”(2). Those men realized the patterns and the beauty behind the traces, but considered them as natural curiosities with an inorganic origin. So Ichnology began as an aesthetic appreciation of the traces and only became a systematically structured science in the 19th century. But unlike Aldrovandi, Leonardo made very insightful appreciations about the nature of the traces: He correctly interprets trace fossils as biogenic structures left by living organisms and used as complementary of his theory on marine body fossils.

Leonardo da Vinci, La valle dell’Arno, 1473. Pen and ink, Florence: Uffizi Museum. Photo Credit: Art Resource, NY.

The majority of Leonardo’s scientific observations were in the Leicester Codex, a collection of writings from the 16th Century. In the Codex, Leonardo writes that marine shells found on the mountains corresponded to living animal and they have been “petrified” with marine sediments and refutes all the assumptions of the biblical Deluge. He also studied the locomotion of mollusks and the biogenic structures produced by living animals comparing them with ichnofossils. Leonardo also refers to trace fossils as an evidence for past marine environments. Several excerpts from the Codex also indicate that Leonard uses many ichnological principles that are still valid today. This is particularly interesting:

“Come nelle falde, infra l’una e l’altra si trovano ancora
gli andamenti delli lombrici, che caminavano infra esse
quando non erano ancora asciutte”.
(Among one and another rock layer, there are the traces of
the worms that crawled in them when they were not yet dry)

(Leonardo da Vinci, Leicester Codex, folio 10v)

The above description reflects how Leonardo understood the  diagenesis of sedimentary layers and taphonomy of trace fossils.

Leonardo’s Paleodictyon.

Paleodictyon is a burrow system composed of a hexagonal mesh, and   particularly common in the Arno Valley, where Leonardo was born.  Unfortunately, the drawing was not  accompanied by any description (3).

Detail of Leonardo’s Paleodictyon. Baucon (2010), Acta Paleontológica Polónica.

Leonardo never received a formal education in Latin or Mathematics and he wrote in Italian. For that reason, Leonardo writings were ignored by the scholars of the time, but five centuries after his death, Leonardo still surprises us.

 

References:

(1) Baucon, A. (2010). Leonardo da Vinci, The Founding Fatheer of Ichnology,  PALAIOS, 25 (6), 361-367 DOI: 10.2110/palo.2009.p09-049r

(2) 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.

(3) Baucon, A. 2010. Da Vinci’s Paleodictyon: the fractal beauty of traces. Acta Geologica Polonica, 60 (1), 3–17.

The enigmatic acritarchs.

Acritarchs are a heterogeneous and polyphyletic group of organic-walled microfossils of unknown affinity, consisting of a central cavity enclosed by a wall of single or multiple layers, with a great variability of shapes and ornamentations. The wall is made by sporopollenine or a very similar compound and the size range is about 5 to 200 micrometers.

Palaeozoic acritarchs. Images from the Natural History Museum database.

The term was first introduced by Evitt in 1963 and means “undecided origin” (from the Greek akritos = undecided, and arche = origin”), and replaced the older group “hystricosphaerid”(1).

When Evitt (1961, 1963) and Wall (1965) proved that many Mesozoic “hystrichosphaerids” were in fact dinoflagellate cysts, the remaining forms of the hystrichosphaerids were classified as “acritarch”.

Based on their morphology, acritarchs are divided in nine groups.

Diagram showing the different group of Acritarchs. Imagen from UCL.

The first record of acritarcs belongs to the Proterozoic (1400 mya) and the range extends to the present time, although the highest point correspond to the early Paleozoic.

Those early forms were almost spherical with a simple opening mechanism in many cases.

Leiosphaeridia sp., an unornamented spheroidal acritarch from the Proterozoic. Copyright © 2006 The Royal Society

During the Cambrian, acritarchs reached a more complexity of forms, and become especially diverse during the Ordovician.

Some acritarchs showing the diversity of forms within the group. Images from UCL.

Because their size, abundance and diversity, as well as widespread distribution, acritarchs are very useful in biostratigraphic correlation and paleoenviromental reconstructions. For instance, the Cambrian/Ordovician system boundary in Arctic Russia was established using acritarchs (3).

Skiagia ornata, from the Early Cambrian. Image from the Museum of Geology, University of Tartu.

But the diversity of the acritarchs rapidly declined at the end of the Devonian and became a modest group during the Carboniferous and Permian.

After the Early Jurassic, acritarchs are scarce and replaced ecologically by the dinoflagellates and many forms considered before as acritarchs are  now clasified as prasinophytes or other green algae.

References:

(1)  Evitt, W.R. 1963. A discussion and proposals concerning fossil dinoflagellates, hystrichospheres and acritarchs. Proceedings of the National Academy of Sciences of the United States of America. Washington, 49(2-3): 158-164.

(2)  Traverse, A. (1988), Paleopalynology. Unwin Hyman

(3)  Moczydlowska, M. y Stockfors, M. 2004. Acritarchs from the Cambrian-Ordovician boundary interval on Kolguev Island, Arctic Russia.Palynology 28: 15-73

Born on this day: Sophie Germain

Portrait of Sophie Germain, from Wikimedia Commons.

 

Sophie Germain was born in Paris on April 1, 1776. She was the second of three daughters of a Parisian silk merchant, Ambroise-François Germain.
From an early age, she showed her passion for knowledge and read the works of Newton and Euler. But her family, like many others at that time, considered that being an intellectual was not appropriately for girls.
She was not allowed from attending to the École Polytechnique because of her gender, but she was able to get the lecture notes for several of the courses.
Sophie was particularly interested in Mathematics. Using the pseudonym of Monsieur LeBlanc, submitted a paper to J. L. Lagrange. He was quite impressed with the essay and wanted to meet the author. After the initial surprise about the true identity of Monsieur LeBlanc, Lagrange eventually became Sophie’s mentor and a moral support for her work.
She was fascinated with the number theory and corresponded with Carl Friedrich Gauss. He guided her research and in 1816, she became the first woman to win a prize from the Paris Academy of Sciences with her paper: ‘Memoir on the Vibrations of Elastic Plates’.
She continued to work in mathematics and philosophy until her death.
On June 27, 1831, at the age of 55, Sophie Germain died after a battle against breast cancer.
Six years after her death, received an honorary degree from the University of Göttingen.

Reference:

Gray, Mary W. “Sophie Germain.” Complexities: Women in Mathematics. Ed. Bettye Anne Case and Anne M. Leggett. United Kingdom: Princeton University Press, 2005. 68-75.