A
Selected Chronological Bibliography of Biology and Medicine
Part 1A
Compiled by James Southworth
Steen, Ph.D.
Delta State University
Dedicated to my loving family
This document celebrates those secondary authors and laboratory technicians
without whom most of this great labor of discovery would have proved
impossible.
Please forward any editorial
comments to: James S. Steen, Ph.D., Professor Emeritus, DSU Box 3262,
Cleveland, MS 38733. jsteen08@bellsouth.net
“Reason was born, as it has
since now discovered, into a world already wonderfully organized, in which it
found its precursor in what is called life, its seat in an animal body of
unusual plasticity, and its function in rendering that body’s volatile
instincts and sensations harmonious with one another and with the outer world
on which they depend.” George Santayana (1132).
“In all human affairs … there is a single dominant factor—time. To
make sense of the present state of science, we need to know how it got like
that: we cannot avoid an historical account…To extrapolate into the future we
must look backwards a little into the past.” John M. Ziman (1431).
"The proper concern of
natural science is not what God could do
if he wished, but what he has done; that is, what happens in the world
according to the inherent causes of nature." Albertus Magnus; Alberti
Magni; Albert the Great (DE) (581; 1114).
"Admitting that vital phenomena rest upon
physico-chemical activities, which is the truth, the essence of the problem is
not thereby cleared up; for it is no chance encounter of physico-chemical
phenomena which constructs each being according to a pre-existing plan, and
produces the admirable subordination and the harmonious concert of organic
activity.
There is an arrangement in the living being, a
kind of regulated activity, which must never be neglected, because it is in
truth the most striking characteristic of living beings. . . .
Vital phenomena possess indeed their rigorously
determined physico-chemical conditions, but, at the same time, they subordinate
themselves and succeed one another in a pattern and according to a law which
pre-exists; they repeat themselves with order, regularity, constancy, and they
harmonize in such manner as to bring about the organization and growth of the
individual, animal or plant.
It is as if there existed a pre-established
design of each organism and of each organ such that, though considered
separately, each physiological process is dependent upon the general forces of
nature, yet taken in relation with the other physiological processes, it
reveals a special bond and seems directed by some invisible guide in the path
which it follows and toward the position which it occupies.
The simplest reflection reveals a primary
quality, a quid proprium of the living being, in this pre-established
organic harmony.” Claude Bernard (FR) (169).
c. 13.75 G (giga annum= billion years)
Georges Henri Joseph Édouard
Lemaitre (BE) proposed that the
universe began as a primal atom, an
incredibly dense egg containing all
the material for the universe within a sphere about 30 times larger than our
Sun. This primal atom rapidly
expanded for c. 10-20 G scattering matter and energy in all directions (337; 761; 816; 817). This theory is now known popularly
as the Big Bang Theory, a phrase
coined by Fred Hoyle (GB) in a moment of facetiousness, during a radio broadcast (679). Note: Alexander
Friedmann (RU) proposed an expanding universe as early as 1922 (145). Note: Today, most
physicists and cosmologists conceive of the primal atom as having been
smaller than Lemaitre's!
On February 12, 2003, Charles L. Bennett (US) and a team from the
National Aeronautics and Space administration (NASA) and the Goddard Space
Flight Center in Maryland announced that the age of the universe is 13.7 G with
a one percent margin for error (275; 342).
Eleanor Margaret Burbidge (US), Geoffrey R. Burbidge (US), William
A. Fowler (US), and Fred Hoyle (GB) suggested that the heavier elements are
formed in supernova explosions (248).
Lawrence Hugh Aller (US) concluded that nucleosyntheses in stellar
interiors generates carbon, nitrogen, oxygen, phosphorus, and other biogenic
elements (47).
c. 5 G
c. 4.55 G
Clair Cameron Patterson (US), George Tilton (US), and Mark Ingham
(US) used uranium decay in rocks from Earth and in meteorites that struck Earth
to date our solar system at 4.55 G (1020-1022).
c. 4.4-3.9 G
Samuel A. Bowring (US) and Ian S. Williams (US) identified the
oldest rocks found on Earth as granite-like rocks called gneiss from the Acasta Gneiss Complex near Great Slave Lake,
Northwest Territory, Canada. Their age was determined to be 4.03 G. The Isua
Supracrustal rocks in West Greenland are a close second at 3.7 to 3.8 G. These
rocks were dated using the uranium 235 to lead 207 method (206).
Alessandro Morbidelli (IT), John Chambers (US), Jonathan I. Lunine
(US), Jean-Marc Petit (IT), Francois Robert (FR), Giovanni B. Valsecchi (IT),
and Kim E. Cyr (US) proposed
that as the solar system formed, Jupiter's powerful gravity perturbed asteroids
to accrete into larger and larger objects resulting in terrestrial
"embryos" near the size of Mars. These "embryos were tossed into
very unstable elliptical orbits with the result that some collided with Earth
thereby delivering the water that now fills Earth's oceans. These events
occurred when Earth was about half its present size (933).
Alexander Ivanovich Oparin (RU) postulated that a long chemical
evolution in the oceans preceded the appearance of life on Earth (970-972).
John Burdon Sanderson Haldane (GB-IN), Harold Clayton Urey (US)
and John Desmond Bernal (GB) also forwarded the same hypothesis (167; 599; 1308). This is often called the heterotroph
hypothesis of the origin of life.
Preston Ercelle Cloud, Jr. (US) and Stanley Lloyd Miller (US) made
the argument that the Earth’s primitive atmosphere was virtually devoid of
oxygen (308; 924).
Kenneth M. Towe (US) made a compelling case that the Earth’s early
atmosphere contained significant quantities of oxygen (1298).
John Desmond Bernal (GB), Peter C. Sylvester-Bradley (GB), S.
Ichtiaque Rasool (US), Donald M. Hunten (US), William M. Kaula (US), Egon T.
Degens (DE), Kenneth M. Towe (US), Edward Anders (US), Gustaf Olaf Arrhenius
(SE-US), Bibhas Ranjan De (US), Hannes Olof Gosta Alfvén (SE-US), Anne Benlow
(GB), Arthur Jack Meadows (GB), Manfred A. Lange (DE), and Thomas J. Ahrens
(US) proposed that on the primitive Earth, impact accretions from
extraterrestrial objects represented a significant source of atmospheric and
biogenic elements (59; 88; 157; 168; 418; 786; 1076; 1257; 1297).
James F. Kasting (US), James B. Pollack (US), and David Crisp (US)
concluded that to keep the oceans from freezing on the primitive Earth a global
"greenhouse" was necessary. This "greenhouse" would have
offset the effects of a faint young Sun which was dimmer than todays by 25-30%.
Climate models confirm that 100-1,000 times the present atmospheric level of
carbon dioxide would have been necessary to produce the ancient
"greenhouse" effect (734).
Arvid Gustaf Högbom (SE) suggested that Earth's primitive
atmosphere resulted from gradual, episodic, or rapid volcanic out-gassing and
weathering (658).
Steffen L. Thomsen (DE), Claude J. Allègre (FR), Thomas Staudacher
(FR), and Philippe Sarda (FR) determined that early catastrophic out-gassing
occurred on the young Earth (46; 1289). This would have released significant
amounts of nitrogen, carbon dioxide, carbon monoxide, methane, water, hydrogen,
sulfur dioxide, and hydrogen sulfide.
James C.G. Walker (US) and Peter Brimblecombe (GB) found that
abundant aqueous ferrous iron occurring in an oceanic hydrothermal system
resulted in the precipitation of otherwise highly insoluble iron sulfides. This
suggests that on the primitive Earth such a system would have served as a
highly effective sink for hydrogen sulfide (1359).
Bernard J. Wood (GB) and David Virgo (US) presented evidence that
Earth's primitive atmosphere was poised at a redox state buffered close to the
fayalite-quartz-magnetite system, which is consistent with a neutral redox
atmosphere and characteristic of basalts throughout the geological record (1409).
James F. Kasting (US), Donald R. Lowe (US), and John P. Grotzinger
(US) used greenhouse calculations and the sedimentary record to suggest that
prior to 3.8 G the Earth’s surface was a warm (80-100˚C), with a
bicarbonate-rich ocean at a pH perhaps as low as 6 (588; 734; 841).
Juan Oró (ES-US), Aubrey P. Kimball (US), Richard Reed Fritz (US),
and Fenil Master (US) synthesized amino acids from formaldehyde and
hydroxylamine under primitive Earth conditions (977).
Juan Oró (US), E. Stephen-Sherwood (US), and Aubrey P. Kimball
(US) synthesized adenine, thymine, amino acids, and other biochemical compounds
from HCN in a primitive Earth environment (975; 976; 1238).
David W. Deamer (US) and Richard M. Pashley (AU) found
membrane-forming non-polar molecules within the Murchison carbonaceous
chondritic meteorite (415).
Keith A. Kvenvolden (US), James G. Lawless (US), Katherine Pering
(US), Etta Peterson (US), Jose Flores (US), Cyril Ponnamperuma (LK-US), Isaac
R. Kaplan (US), Carleton Moore (US) and John R. Cronin (US) examined the
Murchison carbonaceous chondritic meteorite and found racemic mixtures of 74
different amino acids: Eight that are present in proteins, eleven with other
biological roles (including, quite surprisingly, some neurotransmitters), and
fifty-five that have been found almost exclusively in extraterrestrial samples (348; 776; 777).
Joan Oró (US), E. Stephen-Sherwood (US), Joseph Eichberg (US), and
Dennis E. Epps (US) reported the synthesis of phospholipids under primitive
Earth conditions (978).
Joseph P. Pinto (US), G. Randall Gladstone (US), Yuk Ling Yung
(US), Akiva Bar-Nun (IL), Sherwood Chang (US), and James F. Kasting (US) showed
that photochemistry in an atmosphere containing carbon dioxide or a mixture of
carbon monoxide and carbon dioxide yielded formaldehyde as a major product (118; 733; 1035).
Stanley Lloyd Miller (US), in Harold Clayton Urey’s (US)
laboratory, showed that a wet mixture of methane, hydrogen, and ammonia exposed
to electrical discharge for a while, formed traces of organic compounds,
including organic acids and amino-acids regarded as exclusive components of
living things (923).
William S. Brinigar (US), David B. Knaff (US), and Jui H. Wang
(US) mixed a porphyrin, AMP, and inorganic phosphate with an imidazole group as
a catalyst. Exposure of the mixture to ultraviolet or visible light resulted in
the direct synthesis of ATP (220).
Christopher Reid (GB), Leslie Eleazer Orgel (GB-US), and Cyril
Ponnamperuma (LK-US) have shown that random processes can form nucleotides and
dinucleotides. They have also demonstrated the formation of ATP through the
ultimate agency of solar energy (1086).
William R. Hargreaves (US), Sean J. Mulvihill (US), and David W.
Deamer (US) found that fatty acids and glycerol combine spontaneously to
produce phospholipids when heated to dryness at 65°C, as they might have been
in an evaporating tide pool along a primitive sea (608).
John Desmond Bernal (GB) proposed that one way in which organic
subunits may spontaneously combine into larger molecules is by adsorption of
the reacting molecules onto the highly ordered negatively charged
aluminosilicates of clays. The clay surface performs a catalytic function (166; 167).
Alexander Graham Cairns-Smith (GB), P. Ingram (GB), and Gregory L.
Walker (GB) also proposed that under primitive Earth conditions organic
polymers could have condensed on extremely thin layers of negatively charged
aluminosilicates separated by layers of water (252).
Sidney Walter Fox (US), Kaoru Harada (JP), and Allen Vegotsky (US)
showed how amino acids can be heated under Earth conditions to form proteinoids
or "thermal proteins," which when placed in water self-organize into
microspheres or protocells, possible precursors of the contemporary living cell
(511-514).
Noam Lahav (IL), David White (US), and Sherwood Chang (US)
experimentally produced peptide bonds under conditions where clay, water, and
amino acids were subjected to cyclic variations in temperature and water
content (780).
James R. Hawker, Jr. (US) and Juan Oró (US) synthesized peptides
under plausible primitive Earth conditions (618).
E. Stephen-Sherwood (US), A. Joshi (US), and Juan Oró (US)
produced polynucleotide polymers under primitive Earth conditions (1237).
A. Mar (US), Jason P. Dworkin (US) and Juan Oró (US) synthesized
uridine diphosphate glucose, cytidine diphosphate choline, other phosphorylated
metabolic intermediates, the coenzymes adenosine diphosphate glucose (adPG),
guanosine diphosphate glucose (GDPG), and cytidine diphosphoethanolamine
(CDP-ethanolamine) under primitive Earth conditions (877; 878).
Carl R. Woese (US), Francis Harry Compton Crick (GB), and Leslie
Eleazer Orgel (GB-US) suggested that it would have been possible in a pre-DNA
world to have a primitive replicating and catalytic apparatus devoid of both
DNA and proteins and based solely on RNA molecules, i.e., an RNA world
(345; 973; 1403).
Jennifer A. Doudna (US) and Jack W. Szostak (US) found that the Tetrahymena ribozyme could splice
together multiple oligonucleotides aligned on a template strand to yield a
fully complementary product strand. This reaction demonstrates the feasibility
of RNA-catalyzed RNA replications and supports the RNA world hypothesis (443).
Bruce Michael Alberts (US), Walter Gilbert (US), and Antonio
Lazcano (MX) proposed that DNA and proteins were derived from RNA-based cells
or cell-like units (34; 558; 789).
Antonio Lazcano (MX) postulated that DNA evolved to replace RNA as
the repository of hereditary information because, 1) DNA is much more resistant
to harsh environmental conditions, 2) DNA is less prone to mutations which
cannot be repaired, 3) cytosines in DNA are not as prone to spontaneously
deaminate to uracil as they are in RNA, and 4) the duplex nature of DNA offered
redundancy, which when coupled with repair mechanisms had a distinct advantage
over simplex RNA without a repair mechanism (790).
Carl R. Woese (US) originally described the progenote as the last common ancestor for archaebacteria (Archaea),
eubacteria (Bacteria), and eukaryotes (Eucarya). It contained informational
polymers, could synthesize polypeptides, and was still evolving a link between
genotype and phenotype (1404; 1405).
Francis Harry Compton Crick (GB), Sydney Brenner (ZA-GB), Aaron
Klug (ZA-GB), and George Pieczenik (US) proposed that the assignment of codons to particular amino acids was
simply an historical accident, there being no special reasons why a particular codon stands for a given amino acid (346).
J. William Schopf (US), John M. Hayes (US), and Malcolm R. Walter
(US), speculated that life on Earth might have arisen as early as 3.9 G (1161).
Norman Harold Horowitz (US) and Jerry S. Hubbard (US) proposed how
complex sequential metabolic pathways may have arisen as the result of
selective pressure. The retrograde model.
Suppose that a contemporary cellular pathway makes a required
substance such as an amino acid through the sequence A to B to C to D to E, in
which A is a simple inorganic substance and E is the final organic product.
Initially E was plentiful in the environment and was absorbed directly by
primitive aggregates. Later, as E became scarce because of use, chemical
selection favored pre-cells that could make E from D, a slightly less complex
organic substance still found in abundance in the environment. As D became
exhausted, selection favored assemblies that developed the pathway C to D to E,
in which the even simpler substance C could be absorbed and used as raw
material to make D. This process continued until the entire synthetic pathway,
based on an essentially inexhaustible inorganic substance, was established (672; 673).
Karl O. Stetter (DE) concluded that the origin of life probably
took place under conditions of high temperature because the hyperthermophiles
are grouped around and occupy all the deepest branches of the three-kingdom
phylogenetic scheme. He also concluded that an anaerobic hyperthermophilic
autotroph was very likely the original cell type
(1239).
Günter Wächtershäuser (DE) presented a hypothesis supporting
chemoautotrophy as the first form of metabolism to appear within life forms on
the primitive Earth. He argued that these life forms were coatings that adhered
to the positively charged surfaces of pyrite, a mineral composed of iron and
sulfur. The formation of pyrite from hydrogen sulfide provides a source of
electrons as an energy source (1350).
c. 3.5 G
Mark E. Barley (AU), John S.R. Dunlop (AU), Joseph John Edmund
Glover (AU), David I. Groves (AU), and Roger Buick (AU) concluded from their
studies of sedimentary rocks in Western Australia that near 3.5 G there existed
a shallow marine environment dominated by episodic island volcanism and
hydrothermal activity (124; 591).
Stanley M. Awramik (US), J. William Schopf (US), Malcolm R. Walter
(US), and Bonnie M. Packer (US) found rock bearing 3.5 G microfossils within
early Archean (Gk. archaios=ancient)
stromatolites (101; 1159; 1163). The microfossils were interpreted to
be prokaryotes and to represent the oldest fossils known (1162).
Brian W. Logan (AU), Richard Rezak (US), and Robert N. Ginsburg
(US) discovered living cryptozoon and associate stromatolites at Shark Bay,
Western Australia (834; 835; 1044; 1045).
Harald Furnes (NO), Neil R. Banerjee (CA), Karlis Muehlenbachs
(CA), Hubert Staudigel (US), and Maarten De Wit (NL) found tiny holes in
volcanic glass. They believe microorganisms etched these tiny holes, c. 3.5 G (529).
Norman Richard Pace, Jr. (US) indicated that the Archaea and
Bacteria diverged from one another near the time that life arose on Earth. This
changed the notion of evolutionary unity among prokaryotes. The phylogenetic
data support the very early appearance of the eukaryotic nuclear line of
descent. The Eucarya is as old as the prokaryotic lines Archaea and Bacteria.
The idea that eukaryotes resulted from the fusion of two prokaryotes and are
late arrivals on the evolutionary stage (1-1.5 G) is incorrect (991).
Carl R. Woese (US) proposed that the halophilic archaebacteria
(Archaea) are a group of aerobic or microaerophilic organisms that evolved from
a strictly anaerobic and nonhalophilic methanogen ancestor. Woese also
constructed a trifurcated, unrooted, universal evolutionary tree in which all
known organisms can be grouped in one of three major lineages: eubacteria
(Bacteria), the archaebacteria (Archaea), and the eukaryotic (Eucarya)
nucleocytoplasm. This is often referred to simply as the three-kingdom scheme (1405).
Mitchell Lloyd Sogin (US), John H. Gunderson (US), Hillie J.
Elwood (US), Rogelio A. Alonso (US), and Debra A. Peattie (US) determined that
the 16S-like rRNA of the diplomonad Giardia
lamblia has retained many of the features that may have been present in the
common ancestor of eukaryotes (Eucarya) and prokaryotes (Archaea or Bacteria).
They concluded that it represents the earliest-branching eukaryotic lineage (1220).
Mitchell Lloyd Sogin (US) declared that some microbial lineages
seem never to have had mitochondria and chloroplasts, so may have diverged from
the eukaryotic (Eucarya) line of descent prior to the incorporation of the
organelles (1219).
c. 3.235 G
Birger Rasmussen (AU) discovered pyritic filaments, the probable
fossil remains of thread-like microorganisms, in a 3,235-million-year-old
deep-sea volcanogenic massive sulfide deposit from the Pilbara Craton of
Australia (1075). Note: From their mode of occurrence, the microorganisms
were probably thermophilic chemotropic prokaryotes, which inhabited
sub-sea-floor hydrothermal environments. They represent the first fossil
evidence for microbial life in a Precambrian submarine thermal spring system
and extend the known range of submarine hydrothermal biota by more than 2,700
million years. Such environments may have hosted the first living systems on
Earth, consistent with proposals for a thermophilic origin of life. See, Corliss, 1981.
c. 2.7 G
Roger E. Summons (AU), Linda L. Jahnke (AU), Janet M.
Hope (AU), Graham A.
Logan (AU), Jochen J. Brocks (AU), and Roger Buick (AU) found
molecular fossils of biological lipids preserved in 2,700-million-year-old
shales from the Pilbara Craton, Australia. This makes these the oldest known biomolecules. The
presence of abundant 2 alpha-methylhopanes, which are characteristic of
cyanobacteria, indicates that oxygenic photosynthesis evolved well before the
atmosphere became oxidizing. The presence of steranes, particularly cholestane
and its 28- to 30-carbon analogs, provides persuasive evidence for the
existence of eukaryotes 500 million to 1 billion years before the extant fossil
record indicates that the lineage arose (222; 1250).
c. 2.5
The Proterozoic Era (Gk. proteros=early;
zoe=life) extended from 2.5 G to 544
Ma. It is considered to represent the most recent Era of the Precambrian Time.
c. 2.1 G
Preston Ercelle Cloud, Jr. (US) proposed a working model of the
primitive Earth in which he related atmospheric-geologic-biologic history of
the Precambrian (307).
Stanley A. Tyler (US) and Elso Sterrenberg Barghoorn (US) reported
the discovery of fossil microscopic organisms in an outcropping of
mid-Precambrian rocks called the Gunflint Iron formation near Lake Superior in
Ontario. Most of these fossils resemble present day bacteria and cyanobacteria.
This was the first indisputable evidence of Precambrian life (1305). Barghoorn, Tyler, and Preston Ercelle Cloud, Jr. (US) later
confirmed these findings and discussed their significance (122; 306). Note:
Other Precambriam fossil sites include: the Fig Tree Group, Africa; the
Bulawayan Formation, Africa; the Gunflint Iron Formation, Minnesota/Canada; the
Belcher Group, Hudson Bay; Bitter Springs, Australia; and the Ediacaran Sites,
Australia.
Tsu-Ming Han (US) and Bruce N. Runnegar (AU-US) found fossils of
the multi-cellular Grypania spiralis
(probably an alga) in the 2.1 G Negaunee Iron Formation in Michigan, U.S.A. (606).
Malcom R. Walter (US), Du Rulin (US), and Robert Joseph Horodyski
(US) had previously discovered multi-cellular fossils (c.1.4 G) in old Greyson
Shale, lower Belt Supergroup, in Montana, US, and from the similarly aged
Gaoyuzhuang Formation, upper Changcheng Group, in the Jixian section, Northern
China. The organism was identified as Grypania
spiralis, a coiled ribbon-like creature. It was judged to most likely have
been a multi-cellular eukaryotic alga (1362). Shale is rock formed by condensation of layers of clay or mud,
along with phytoplankton and other debris, deposited at the bottoms of lakes or
ocean basins.
Konstantin Sergejewitsch Mereschkowsky (RU) proposed the theory of
the symbiotic origin of the eukaryotic cell and introduced the term symbiogenesis to signify the emergence
of new species with identifiably new physiologies and structures as a
consequence of stable integration of symbionts.
It stated that the chloroplast and mitochondria of eukaryotic cells had their
origins from endosymbiotic
cyanobacteria and aerobic bacteria, respectively, whose ancestors were once
captured and incorporated by a primitive, anaerobic, heterotrophic host. Many
others would later refine this theory (269; 270; 749; 750; 880; 916).
c. 2 G
J. William Schopf (US) Elso Sterrenberg Barghoorn (US), Morton D.
Maser (US), and Robert O. Gordon (US) found microscopic formations that looked
very much like traces of cyanobacteria in 2-billion-year-old rock called
Gunflint chert. The find was near Lake Superior in Canada (1160). Cherts are rocks composed of minute interlocking grains of
silica, occurring as the mineral quartz (SiO2).
Elso Sterrenberg Barghoorn (US) and J. William Schopf (US)
discovered fossils of microorganisms in stromatolitic cherts of the
Neoproterozoic Bitter Springs Formation of the Amadeus Basin of Central
Australia (121; 1156).
Other Precambrian fossil sites include: the Fig Tree Group, Africa;
the Bulawayan Formation, Africa; the Gunflint Iron Formation, Minnesota/Canada;
the Belcher Group, Hudson Bay; Bitter Springs, Australia; and the Ediacaran
Sites, Australia.
c. 1.8 G- 600 M (mega annum = million years)
Zh Zhang (CN) discovered large (40-200 micrometer) spherical
microfossils 1.8 to 1.9 billion years old in sedimentary rocks from China.
These microfossils were interpreted to be the earliest known eukaryotes
(Eucarya) (1428).
c. 1.4 G
c. 1 G
The ultraviolet absorbing ozone layer in Earth's atmosphere began
to appear. High in the atmosphere, some oxygen (O2) molecules
absorbed energy from the Sun's ultraviolet rays and split to form single oxygen
atoms. These atoms combined with remaining oxygen (O2) to form ozone
(O3) molecules, which are very effective at absorbing UV rays. Most
microorganisms had already evolved ways to protect themselves from ultraviolet
radiation, e.g. DNA repair systems, ultraviolet absorbing pigments, and outer
skeletons (1302).
Joseph Felsenstein (US) created evolutionary trees using rRNA
sequences and a maximum likelihood approach. He concluded that the Plantae,
Animalia, and Fungi along with two new evolutionary assemblages (alveolates and stramenophiles) diverged nearly simultaneously (487). Alveolates include
dinoflagellates, apicomplexans, and ciliated protozoans. The stramenopiles include brown algae,
labyrinthulids, chrysophytes, xanthophytes, diatoms, and oomycetes (1019).
Elso Sterrenberg Barghoorn (US) and J. William Schopf (US) discovered
fossils of microorganisms in stromatolitic cherts of the Neoproterozoic Bitter
Springs Formation of the Amadeus Basin of central Australia (121; 1156). Cherts are rocks composed of minute interlocking grains of
silica, occurring as the mineral quartz (SiO2).
Other Precambrian fossil sites include: the Fig Tree Group,
Africa; the Bulawayan Formation, Africa; the Gunflint Iron Formation,
Minnesota/Canada; the Belcher Group, Hudson Bay; Bitter Springs, Australia; and
the Ediacaran Sites, Australia.
Gerard Peter Kuiper (NL-US) proposed that the Earth’s early atmosphere
was rich in hydrogen and helium most of which would drift into space over the
next 1 billion years and be replaced by a secondary atmosphere rich in heavier
gases (772).
c. 700 M
J. William Schopf (US), Bonnie M. Packer (US), Roger Buick (AU),
and Stanley M. Awramik (US) presented evidence for a well-established community
of oxygenic photssynthesizers (100; 245; 1163).
Charles Doolittle Walcott (US) identified pillar shaped masses of
thinly layered limestone rock in Precambrian strata from the Grand Canyon in
Western North America. Although he did not understand their significance as
fossils he later interpreted these pillar like structures of limestone as
fossilized reefs laid down by algae (cyanobacteria) (1352). These pillar-like structures called cryptozoon (hidden life) are now called stromatolites.
Charles Doolittle Walcott (US) described an important clue in the
search for Precambrian life when he discovered fossils in Precambrian
carbon-rich shales on the slopes of a prominent butte deep within the Grand
Canyon. The shales belonged to what is known as the Chuar Group of strata, so,
Walcott named the fossils Chuaria. Chuaria is now known to be an unusually
large, originally spheroidal, single-celled planktonic alga, i.e., a megasphaeromorph acritarch. Walcott's specimens were indeed authentic fossils, the
first true Precambrian organisms where cellular detail is recorded (1353).
c. 635 M
Roger Mason (GB) Tina Negus (GB) and other school children
discovered in Charnwood Forest, England the Precambrian fossil remains of what
may very well be the oldest known multicellular animal (later named Charnia).
Trevor D. Ford (GB) reported this discovery. The position of the clade for this organism in the tree of life
remains uncertain (508).
Jonathan B. Antcliffe (GB) and Martin D.
Brasier (GB) note that Charnia
is both temporally and geographically the most widespread Ediacaran fossil (66).
Guy M. Narbonne (CA) and James G.
Gehling (AU) report that the greatest abundance of specimens of Charnia, which
are also the oldest reliably dated Ediacaran fossils, are found along the
southeast coast of Newfoundland (950). Note: Other Precambrian fossil
sites include: the Fig Tree Group, Africa; the Bulawayan Formation, Africa; the
Gunflint Iron Formation, Minnesota/Canada; the Belcher Group, Hudson Bay;
Bitter Springs, Australia; and the Ediacaran Sites, Australia.
c. 600 M
Reginald Claude Sprigg (AU) discovered Precambrian metazoan
fossils in the Pound Quartzite at Ediacara Hills and in the Flinders Ranges of
South Australia. At the time of discovery, he thought these fossils were from
the Cambrian (1228; 1229).
Ilya Bobrovskiy (AU), Janet M. Hope (AU), Andrey Ivantsov (RU),
Benjamin J. Nettersheim (DE), Christian Hallmann (DE), Jochen J. Brooks (AU)
used lipid biomarkers obtained from Dickinsonia fossils and
found that the fossils contained almost exclusively cholesteroids, a marker
found only in animals. Thus, Dickinsonia were basal animals. This
supports the idea that the Ediacaran biota may have been a precursor to the
explosion of animal forms later observed in the Cambrian, about 500 million
years ago (185).
Martin Fritz Glaessner (CZ-AU) and Mary Wade (AU) determined
fossils in the Ediacara Hills of South Australia (Ediacaran fauna) to be late
Precambrian in age, making them the oldest-known multi-celled organisms (561-564).
Mary L. Droser (US) and James G. Gehling (AU) believe they have
found the earliest fossil evidence for sexual reproduction in Funisia, an
Ediacaran "animal". Its relationship to other animals is unknown (444).
c. 590-550 M
The Cambrian Period of the Paleozoic Era extended from 590 M to
505 M.
The word Cambrian is taken from Cambria, the Latin name for modern Wales. Other fossil rich
Cambrian sites include: Chengjiang, China; the Wheeler Formation in Utah; and
the Croixan Series in Minnesota/Wisconsin.
With one exception (the phylum Bryozoa), every metazoan phylum
with hard parts, and many that lack hard parts, made their first appearances in
the Cambrian. However, Cambrian marine life was quite different from modern biotas; the dominant invertebrates with
hard parts were trilobites, inarticulate brachiopods, archaeocyathids, and problematic conical fossils known as hyolithids. Many Early Cambrian
invertebrates are known only from small
shelly fossils - tiny plates and scales and spines and tubes and so on,
many of which were pieces of the skeletons of larger animals (1171). Note: This publication
initiated the early Paleozoic time scale. Many Cambrian fossils are found in
shale (a rock formed by condensation of layers of clay or mud, along with
phytoplankton and other debris, deposited at the bottoms of lakes or ocean
basins).
The Phanerozoic Eon (Gk. phaneros=visible;
zoe=life) extends from 544 M to the
present. It contains three eras, the Paleozoic, the Mesozoic, and the Cenozoic.
c. 541 M
Alexandr Petrovich Karpinsky (RU) recorded his classic work on
Paleozoic fossil sharks of the family Edestidae (730; 732).
c. 513 M
Charles Doolittle Walcott (US), in 1909, discovered a rich
assemblage of algae and invertebrate fossils from the Middle Cambrian Period of
the Paleozoic Era in the Burgess shale located in Yoho National Park in the
Rocky Mountains, near Field, British Columbia, Canada (1354). Note: The word Cambrian is taken from a Latin form of the
Welsh name for Wales. Other fossil rich Cambrian sites include Chengjiang,
China, the Wheeler Formation in Utah, and the Croixan Series in Minnesota-Wisconsin.
(Shale is rock formed by condensation of layers of clay or mud, along with
phytoplankton and other debris, sedimented at the bottoms of lakes or ocean
basins.)
Harry Blackmore Whittington (GB), in 1966, began re-examining
Burgess Shale fossils originally identified by Charles Doolittle Walcott (US)
as early as 1909. Over the next two decades, Whittington, with the assistance
of his graduate students Simon Conway-Morris (GB) and Derek Briggs (GB),
eventually overturned Walcott's theories that these organisms all belonged to
modern phyla and proposed that most of the specimens are much more complex than
originally believed, and have left no living relatives (330; 1381; 1382).
c. 505 M
Charles Lapworth (GB), from his extensive analysis of graptolite
fossils in Scotland, proposed the Ordovician System of strata to resolve the
Murchison-Sedgwick conflict over their overlapping claims for their Silurain
and Cambrian systems (788). The Ordovician (from the name of an ancient British tribe, the
Ordovices) Period of the Paleozoic Era extended from 505 M until 438 M. At the
end of the Cambrian, sea levels fell, causing extinctions. It was in the
Ordovician that the first animals with backbones arose, the Agnatha, these jawless fishes were the
first animals with true bony skeletons. The Ordovician is best known for the
presence of its diverse marine invertebrates, including, corals, graptolites,
trilobites, brachiopods, and the conodonts
(early vertebrates). A typical marine community consisted of these animals,
plus red and green algae, primitive fish, cephalopods, corals, crinoids, and
gastropods. More recently, there has been found evidence of tetrahedral spores
that are like those of primitive land plants, suggesting that plants invaded
the land at this time.
The Ordovician Period ended with a mass extinction. About 25% of
all families did not make it into the Silurian.
Classic fossil-bearing rocks of the Ordovician Period include:
Whiterock Formation, Utah; and the Nevada Cincinnatian Series, Ohio/Indiana/
Kentucky.
c. 466 M
444-359 M
Thomas Chrowder Chamberlain (US) was the first to suggest a
continental freshwater origin of vertebrates during the Silurian and Devonian
time (279). Currently most scholars support a marine origin for vertebrates.
c. 439 M
Roderick Impey Murchison (GB) defined and named the
Silurian Period commemorating the Silures, an ancient tribe that had inhabited
the type area in the Welsh borderland region (946). The Silurian Period of the
Paleozoic Era lies between approximately 438 mya and 408 mya. No new major
groups of organisms appeared at this time, with old groups flourishing or
declining. It is at this time that our first good evidence of life on land is
preserved, including the earliest fossils of vascular plants and relatives of
spiders and centipedes. The insects arose in the Silurian, probably becoming
the first animal forms to venture out of the water. Increased ozone from
photosynthetic water plants provided protection from ultraviolet rays, making
the terrestrial environment hospitable to those organisms that could prevent
desiccation. Coral reefs made their first appearance during this time, and the
Silurian was also a remarkable time in the evolution of fishes. Not only does
this period mark the wide and rapid spread of jawless fish, but also the highly
significant appearances of both the first known freshwater fish as well as the
first fish with jaws.
Classic Fossil-Bearing rocks of the
Silurian Period include: Wadi Ram in Jordon; Brandon Bridge in Wisconsin; and
the Brownsport Group in Tennessee.
c. 429.5 M
c. 420 M
Dianne Edwards (GB) and E. Catherine W. Rogerson (GB) discovered Cooksonia pertonii near Brecon Beacons,
England in 420 M rock (456; 457). William H. Lang (GB) had earlier
positioned it as the earliest known land-living vascular plant found in England
and one of the earliest in the world (784).
c. 414 M
Leif Størmer (NO) reported that arthropods likely
invaded the land during late Silurian and early Devonian times (1245; 1246).
c. 408 M
Adam Sedgwick (GB) and Roderick Impey Murchison (GB) presented
researches on certain rocks in Devonshire, England, which had a distinctive
fossil assemblage that led them to propose a new division of the geological
time scale—the Devonian. Sedgwick and Murchison first used Devonian in a
publication (1172). This represents the discovery of the Devonian Period—408 M to
360 M—of the Paleozoic Era.
William Lonsdale (GB), in 1837, suggested from a study of the fossils
of the South Devon limestones that they would prove to be of an age
intermediate between the Carboniferous and Silurian systems. It was Lonsdale
who coined the term Devonian, commemorating Devon county, England (839).
The Devonian seas were dominated by brachiopods, such as the spiriferids, and by tabulate and rugose
corals, which built large bioherms,
or reefs, in shallow waters. Encrusting red algae also contributed to reef
building. In the Lower Devonian, ammonoids appeared, leaving us large limestone
deposits from their shells. Bivalves, crinoid and blastoid echinoderms,
graptolites, and trilobites were all present, though most groups of trilobites
disappeared by the close of the Devonian. The Devonian is also notable for the
rapid diversification in fish. Benthic armored fish are common by the Early
Devonian. These early fish are collectively called ostracoderms and include a number of different groups. By the
Mid-Devonian, placoderms, the first
jawed fish, appear. Many of these grew to large sizes and were fearsome
predators. Of the greatest interest to us is the rise of the first sarcopterygiians, i.e., the lobe-finned
fish, which eventually produced the first tetrapods just before the end of the
Devonian. By the Devonian Period, life was well underway in its colonization of
the land. Before this time, there is no organic accumulation in the soils,
causing these soil deposits to be a reddish color. This is indicative of the
underdeveloped landscape, probably colonized only by bacterial and algal mats.
By the start of the Devonian, however, early terrestrial vegetation had begun
to spread. These plants did not have roots or leaves like the plants most
common today, and many had no vascular tissue at all. They probably spread
largely by vegetative growth and did not grow much more than a few centimeters
tall. These plants included the now extinct zosterophylls
and trimerophytes. The early fauna
living among these plants were primarily arthropods: mites, trigonotarbids, wingless insects, and myriapods, though these early faunas are
not well known. By the Late Devonian, lycophytes,
sphenophytes, ferns, and progymnosperms had evolved. Most of
these plants have true roots and leaves, and many are rather tall plants. The
progymnosperm Archaeopteris was a
large tree with true wood. It is the oldest such tree known and produced some
of the world's first forests. This rapid appearance of so many plant groups and
growth forms has been called the Devonian
Explosion. Along with this diversification in terrestrial vegetation
structure, came a diversification of the arthropods.
Rocks rich in Devonian fossils include: Silica Shale in Ohio;
Bundenbach in Germany; Cleveland Shale in Ohio; and the Rhynie in Scotland.
Kesava Mukund Lele (GB) and John Walton (GB) reported that the
earliest plant stomata appeared in Zosterophyllum
myretonianum. These were more like stomata found in modern moss
sporophytes. The type found in vascular plants appeared 4-5 M (815).
Tamara Anastasevna Ishchenko (RU) and R.N. Shylokov (RU)
discovered fossil Marchantiales in Lower Middle Devonian material from the
USSR. This provided evidence that some major bryophyte divisions were well
established by the Lower Devonian and that the bryophytes in general must have
played a part in the initial colonization of land by plants (699).
Alexandr Petrovich Karpinsky (RU) reported research on Devonian
algae, the so-called charophytes. His study of the contemporary charophytes
showed their closeness to extinct Devonian forms and indicated that they likely
had a common ancestor (731; 732).
Jennifer A. Clack (GB) and Michael I. Coates (GB) reported on
fossil specimens of the Devonian fish-like Acanthostega
gunneri they collected during 1987 in Greenland. Their work strongly
suggested that legs appeared in tetrapods well before they abandoned water and
not vice-versa as had been suggested by the popular dry pond theory first
articulated by Alfred Sherwood Romer (US) (299; 310-312).
Hagen Hass (DE), Thomas N. Taylor (US), Winfried Remy (PL-DE), and
Hans Kerp (DE) found fossil hyphae in association with wood decay and fossil
chytrids and Glomales-Endogenales representatives associated with plants of the
Rhynie Chert from the Devonian Period (408-360 mya) (616; 1087; 1088; 1266; 1267). These findings strongly suggest that
the ability to form an arbuscular-mycorrhizal symbiosis occurred early in the
evolution of vascular plants.
c. 396 M
John William Dawson (CA) discovered fossil plant remains (Psilophyton princeps) in Middle and
Lower Devonian rocks from the Gaspé Peninsula in Eastern Canada (365; 366).
Thore Gustaf Halle (SE), Robert Kidston (GB), and William H. Lang
(GB) later found similar confirming fossils in the Rhynie Chert and established
the order Psilophytes (601; 751).
Harlan Parker Banks (US) subsequently split the Psilophytes into
three divisions: Rhyniophytina (Rhyniophyta), Zosterophyllophyta, and
Trimerophytina (Trimerophytophyta) (117). One of the most famous Early Devonian land plant localities is
Rhynie in Aberdeenshire, Scotland. The Rhynie Chert is one of the most
important fossil plant occurrences because it represents the oldest and most
completely preserved terrestrial ecosystem. The Rhynie Chert has been radiometrically
dated at 396 mya (Pragian). Plant
remains show excellent cellular preservation. Three groups of plants are
represented: the Rhyniophytes, the Zosterphyllophytes and a lycopod.
c. 387 M
c. 375 M
c. 360 M
The Carboniferous Period of the Paleozoic Era occurred from about
360 to 286 mya. The term carboniferous
comes from England and refers to the rich deposits of coal that occur there.
These deposits of coal occur throughout Northern Europe, Asia, and Midwestern
and Eastern North America. William Daniel Conybeare (GB) and William Phillips
(GB) named the Carboniferous Period
in their Outlines of Geology of England
and Wales (331). The term carboniferous
is used throughout the world to describe this period, although it has been
separated into the Mississippian
(Lower Carboniferous, 360 mya to 323 mya) and the Pennsylvanian (Upper Carboniferous, 323 mya to 286 mya) in the
United States. This separation was adopted to distinguish the coal-bearing
layers of the Pennsylvanian from the mostly limestone Mississippian and is a
result of differing stratigraphy on the different continents. The Pennsylvanian
was named in 1858 by Henry Darwin Rogers (US), and the Mississippian named by
Alexander Winchell (US) in 1870; both these divisions were given system/period
status in Geology by Thomas Chrowder
Chamberlin (US) and Rollin D. Salisbury (US) (281; 1102; 1397). In addition to having the ideal
conditions for the beginnings of coal, several major biological, geological,
and climatic events occurred during this time. One of the greatest biological
evolutionary innovations of the Carboniferous was the amniote egg, which
allowed for the further exploitation of the land by certain tetrapods. The
amniote egg prevented the desiccation of the embryo inside thus allowing the
ancestors of birds, mammals, and reptiles to reproduce on land. There was also
a trend towards mild temperatures during the Carboniferous, as evidenced by the
decrease in lycopods and large insects and an increase in the number of tree
ferns.
Geologically, the Late Carboniferous collision of Laurussia (present-day
Europe and North America) into Godwanaland (present-day Africa and South
America) produced the Appalachian mountain belt of Eastern North America and
the Hercynian Mountains in the United Kingdom. A further collision of Siberia
and Eastern Europe created the Ural Mountains.
The stratigraphy of the Lower Carboniferous can be easily
distinguished from that of the Upper Carboniferous. The environment of the
Lower Carboniferous in North America was heavily marine when seas covered parts
of the continents. As a result, most of the mineral found in Lower
Carboniferous is limestone, which is composed of the remains of crinoids,
lime-encrusted green algae, or calcium carbonate shaped by waves. The North
American Upper Carboniferous environment was alternately terrestrial and
marine, with the transgression and regression of the seas caused by glaciation.
These environmental conditions, with the vast amount of plant material provided
by the extensive coal forests allowed the production of coal. Plant material did
not decay when the seas covered them. Pressure and heat built up over the
millions of years to transform the plant material to coal.
Rocks rich in Carboniferous fossils include: Mazon Creek,
Illinois, Joggins Formation, Nova Scotia, Edinburgh Coal Beds, Scotland, and
Anthracite Coal Beds, Eastern United States.
Andrew C. Scott (GB) and William Gilbert Chaloner (GB) provided
the earliest fossil record of a gymnosperm, conifers from the Upper
Carboniferous (1170).
John Walton (GB) presented evidence of mosses and liverworts from
the Carboniferous deposits in England (1363).
c. 340 M
Erik Andersson Stensiö (SE) and Gunnar Säve-Söderbergh (SE), of
the 1929-1930 Danish scientific expeditions, found ichthyostegid fossils in the
upper Devonian sediments in eastern Greenland. They appear to be intermediate
between lobe-finned rhipidistians (Osteolepis) and early amphibians. These are
the oldest known fossils that can be classified as amphibians (1142; 1236).
c. 335 M
Stan Wood (GB) discovered the 20 cm long fossilized remains of Westlothiana lizziae in East Kirkton,
West Lothian, Scotland (near Edinburgh). Tim R. Smithson (GB), Robert Lynn
Carroll (GB), Alec L. Panchen (GB), S. Mahala Andrews (GB), Roberta L. Paton
(GB), and Jennifer Alice Clack (GB) clarified its taxonomic status and
concluded that it might be the oldest known reptile and thus the oldest known
amniote (995; 1016; 1217; 1218).
c. 286 M
The Permian Period of the Paleozoic Era (from Perm, a Russian
province) lasted from 286 to 248 M. The Period was first defined by Roderick
Impey Murchison (GB) (947). The distinction between the Paleozoic and the Mesozoic is made
at the end of the Permian in recognition of a large mass extinction of life on
Earth. It affected many groups of organisms in many different environments, but
it affected marine communities the most by far, causing the extinction of most
of the marine invertebrates of the time. Some groups survived the Permian mass
extinction in greatly diminished numbers, but they never again reached the
ecological dominance they once had, clearing the way for another group of sea
life. On land, a relatively smaller extinction of diapsids and synapsids
cleared the way for other forms to dominate and led to what has been called the
Age of Dinosaurs. Also, the great
forests of fern-like plants shifted to gymnosperms, plants with their offspring
enclosed within seeds. Modern conifers, the most familiar gymnosperms of today,
first appear in the fossil record of the Permian. In all, the Permian was the
last of time for some organisms and a pivotal point for others, and life on
earth was never the same again.
The global geography of the Permian included massive areas of land
and water. By the beginning of the Permian, the motion of the Earth's crustal
plates had brought much of the total land together, fused in a supercontinent
known as Pangea. Many of the continents of today in somewhat intact form met in
Pangea (only Asia was broken up at the time), which stretched from the northern
to the southern pole. Most of the rest of the surface area of the Earth was
occupied by a corresponding single ocean, known as Panthalassa, with a smaller
sea to the east of Pangea known as Tethys.
Models indicate that the interior regions of this vast continent
were probably dry, with great seasonal fluctuations, because of the lack of the
moderating effect of nearby bodies of water, and that only portions received
rainfall throughout the year. The ocean itself still has little known about it.
There are indications that the climate of the Earth shifted at this time, and
that glaciation decreased, as the interiors of continents became drier.
Rocks rich in Permian fossils include: Glass Mountains, Texas; Abo
Formation, New Mexico; Kuperschiefer, Germany; and Glossopteris flora in
Gondwana localities.
Paul B. Wignall (GB) and Richard J. Twitchett (GB) presented data
on rocks from Spitsbergen and the equatorial sections of Italy and Slovenia
indicating that the world's oceans became anoxic at both low and high
paleolatitudes in the Late Permian. Such conditions may have been responsible
for the mass extinction at this time. This event affected a wide range of shelf
depths and extended into shallow water well above the storm wave base (1387).
Samual A. Bowring (US), Douglas H. Erwin (US), Yugan G. Jin (CN),
Mark W. Martin (US), Kathleen Davidek (US), and Wei Wang (CN) reported that
uranium/lead zircon data from Late Permian and Early Triassic rocks from south
China place the Permian-Triassic boundary at 251.4 ± 0.3 million years ago.
Biostratigraphic controls from strata intercalated with ash beds below the
boundary indicate that the Changhsingian pulse of the end-Permian extinction,
corresponding to the disappearance of about 85 percent of marine species,
lasted less than 1 million years (205). Note:
Seth D. Burgess (US), Samuel A. Bowring (US), and Shu-zhong Shen (CN) refined
the date of the Permian extinction to between 251.941 ± 0.037 and 251.880 ± 0.031
Mya (249).
Svetoslav Georgiev (US), Holly J. Stein (US), Judith L. Hannah
(US), and Bernard Bingen (NO), Hermann M. Weiss (NO), and Stefan Piasecki (DK)
presented evidence that hot acidic Late Permian seas stifled life in record
time (549).
Andrei Vasilevich Martynov (RU) discovered the oldest undoubted
Coleoptera (beetles) fossils in Upper Permian deposits in North Russia (894).
Francis Wall Oliver (AU) and Dunkinfield Henry Scott (GB)
discovered evidence for the seed of Lyginodendron,
which led to the removal of the Cycadofilices from the Pteridophyta (ferns,
horsetails, and club-mosses) and their inclusion with the gymnosperms (966).
“We now know that the true ferns were only present in the coal
measures in small and archaic forms (Coenopteridales)
very unlike living ferns and most likely all the conspicuous fern-like leaves
of that era belonged to seed plants” (876).
Charles H. Sternberg (US) discovered the fossil remains of a
creature showing both amphibian and reptilian characteristics. Ferdinand Broili
(DE) would name it Seymouria baylorensis
for Seymour, Texas in Baylor County (223).
Samuel Wendell Williston (US) and Ermine Cowles Case (US)
described Seymouria and other
labyrinthodont amphibian and reptile fossils from the Permian beds of Texas and
New Mexico (263; 1392-1394).
251.9 M
Yadong Sun (CN), Michael M. Joachimski (DE), Paul B.
Wignall (GB), Chunbo Yan (CN), Yanlong Chen (AT), Haishui Jiang
(CN), Lina Wang (CN), and Xulong Lai (CN) suggested that the "Siberian
Traps" are the primary cause of the Permian–Triassic extinction
event, the most severe extinction event in the geologic record (1252). Note: The "Siberian
Traps" is a large region of volcanic rock, known as
a large igneous province, in Siberia, Russia. The massive
eruptive event that formed the traps is one of the largest known
volcanic events in the last 500 million years. The eruptions continued
for roughly two million years and spanned the Permian–Triassic boundry, or
P–T boundary, which occurred around 251.9 million years ago.
c. 248 M
Friedrich August von Alberti (DE) first used the term Triassic
(Trias) when he named the three-division sequence of sandstone: 1) variegated
(Bunter) sandstone, 2) shell (Muschelkalk) sandstone, and 3) Keuper sandstone (1337). The Triassic Period of the Mesozoic Era was a time of transition
following a mass extinction of life, with the survivors of that event spreading
and recolonizing.
The organisms of the Triassic can be considered to belong to one
of three groups: holdovers from the Permo-Triassic extinction, new groups which
flourished briefly, and new groups which went on to dominate the Mesozoic
world. The holdovers included the lycophytes,
glossopterids, and dicynodonts. While those that went on to
dominate the Mesozoic world include modern conifers, cycadeoids, and the
dinosaurs.
Rocks rich in Triassic fossils include: the Moenkopi Formation,
Arizona; Ischigualasto Badlands, Argentina; Newark Supergroup, Eastern U.S.A.;
Djadochta, Mongolia; and the Chinle Formation, Arizona.
Thomas M. Harris (GB) presented excellent evidence of mosses in
the Triassic of England (611; 612).
c. 245 M
S. Blair Hedges (US) and Laura L. Polong (US), Ying Cao (JP),
Michael D. Sorenson (US), Yoshinori Kumazawa (JP), David P. Mindell (US), and
Masami Hasegawa (JP) reported in a study of both nuclear DNA and mitochondrial
DNA that the turtle is anapsid and the closest living relative of the
crocodile. The results apparently establish a phylogenetic joining of
crocodilians with turtles and place squamates at the base of the tree. This
work presents molecular time estimates to support a Triassic origin for the
major groups of living reptiles and supports the previous findings of James E.
Platz (US), J. Michael Colon (US), John A.W. Kirsch (US), Gregory Christian
Mayer (US), Rafael Zardoya (ES), and Axel Meyer (DE) (258; 623; 756; 1043; 1425).
c. 223 M
During the Carnian-Norian mass extinction event whole categories
of animals abruptly vanished from the fossil record. Dinosaurs flourished,
probably filling niches left empty when earlier successful types of animals
suddenly were wiped out. Within a few million years, dinosaur remains accounted
for 25 to 60 percent of the fossils. By 202 million years before the present,
dinosaurs were diverse, sometimes gigantic, and dominant among land animals.
Paul E. Olsen (US), Dennis V. Kent (US), Hans-Dieter Sues (US),
Christian Koeberl (AT), Heinz Huber (US), Alessandro Montanari (IT), Emma C.
Rainforth (US), Sarah J. Fowell (US), Michael J. Szajna (US), and Brian W.
Hartline (US) located a crater of the proper size and age to mark the landfall
of an asteroid which could have had a devastating effect on many life forms.
Manicouagan in Quebec, Canada is the site of the asteroid crater credited with
eliminating competitors of early dinosaurs (967).
c. 213 M
Alexandre-Theodore Brongniart, Jr. (FR) named the Jurassic Period
Jurassique in 1829 for extensive limestone deposits in the Jura Mountains of
Switzerland (224). This period was characterized by Great plant-eating dinosaurs
roaming the earth, feeding on lush growths of ferns and palm-like cycads and bennettitaleans . . . smaller but
vicious carnivores stalking the great herbivores . . . oceans full of fish,
squid, and coiled ammonites, plus great ichthyosaurs and long-necked
plesiosaurs . . . vertebrates taking to the air, like the pterosaurs and the
first birds . . . this was the Jurassic Period, beginning 213 million years ago
and lasting for 70 million years of the Mesozoic Era.
Rocks rich in Jurassic fossils include: the Lias Formation,
England; Navajo Sandstone, Arizona; Solnhofen Limestone, Germany; and the
Morrison Formation, Colorado/Utah/Wyoming.
c. 200 M
S. Blair Hedges (US), Patrick H. Parker (US), Charles G. Sibley
(US), and Sushi Kumar (US) used a comprehensive set of genes that exhibit a
constant rate of substitution to estimate the time at which avian and mammalian
orders diverged. Their estimates of divergence times averaged about 50-90%
earlier than those predicted by the classical methods and show that the timing
of these divergences coincides with the Mesozoic fragmentation of emergent land
areas. This suggests that continental breakup may have been an important
mechanism in the ordinal diversification of birds and mammals (622).
Albert Charles Seward (GB) and Jane Gowan (GB) found fossil
records indicating that the ginkgo or maidenhair tree, Ginkgo biloba, has existed on Earth since the Liassic (early
Jurassic) period meaning it has inhabited earth longer than any other tree;
200-176 M (7; 110; 363; 854; 1190).
Randolph T. Major (US) found that resistance of Ginkgo biloba L. to pests accounts in
part for the longevity of this species (866).
c. 195 M
Mary Anning (GB) was celebrated as the outstanding fossil
collector of her time. Among the many fossils collected and prepared by her are
the first ichthyosaur skeleton and the first plesiosaur skeleton known to the
English community. The ichthyosaur fossil was probably discovered sometime
between 1809 and 1811, when Mary was only 10 to 12 years old. And while Mary
did find the majority of the remains, her brother had discovered part of the
animal twelve months earlier. Most of Mary's finds ended up in museums and
personal collections without credit being given to her as the discoverer of the
fossils (1294). Note: Ichthyosaurs flourished c. 200-190M. Pleisosaurs
flourished c. 203-66 M.
c. 180 M
Hermann von Meyer (DE) gave the name Archaeopteryx (Archeopteryx)
to a fossil discovered in fine sandstone, Jurassic strata, of a quarry near
Solenhofen, Bavaria in 1861. It appeared to be intermediate in character
between reptiles and birds. The Natural History Section of the British Museum
purchased the specimen that was described by Richard Owen (GB) (990). In 1876 another fossil Archaeopteryx
was discovered. This fossil, which now resides in the Humboldt Museum für
Naturkunde in Berlin, is of such rare quality and importance that Dr. Alan
Feduccia says it, “may well be the most important natural history specimen in
existence, comparable perhaps in scientific and even monetary value to the
Rosetta stone” (486; 1173).
William Buckland (GB) published Notice on the Megalosaurus or giant fossil lizard of Stonesfield.
This was the first time a dinosaur fossil was described and named (the term dinosaur did not yet exist). In the same
science meeting where he described Megalosaurus Buckland also announced the
first fossil mammal from the Age of Reptiles (243). Note: Megalosaurus was later dated to the Middle Jurassic period.
Note: In 1822, Gideon Algernon
Mantell (GB) found the fossilized tooth of a Cretaceous animal he would
characterize as herbivorous, reptilian, and tens of feet long; he would name it
Iguanodon. After he prepared a paper reporting Iguanodon for the Royal Society
the aforementioned William Buckland urged Mantell to delay, consequently it was
Buckland not Mantell who first published on a dinosaur discovery. The Iguanodon
is dated to late Jurassic.
Gideon Algernon Mantell (GB), as an amateur paleontologist,
discovered and described from Cretaceous England many fossilized animals
including: Megalosaurus, Iguanodon, Pelorosaurus, the first discovered
brachiosaur, and Hylaeosaurus (874; 875).
George Poinar, Jr. (US) found members of an ancient genus of the Leishmania parasite, Paleoleishmania, in fossilized sand flies dating back to the early
Cretaceous period (1055).
161-145 M
Othniel Charles Marsh (US) introduced and briefly described Apatosaurus ajax, (now known to be
synonymous with Brontosaurus) (888; 889). Two years later he described and
introduced Brontosaurus, thinking
they were different animals (890). Note: Apatosaurus means “deceptive lizard”; Brontosaurus means “thunder lizard”
c. 160 M
Qiang Ji (CN), Zhe-Xi Luo (US),
Chong-Xi Yuan (CN), John R. Wible (US), Jian-Ping Zhang (CN), and Justin A.
Georgi (US) described Juramaia sinensis, a small shrew-like mammal
that lived in China 160 million years ago during the Jurassic. Juramaia is
the earliest known fossil of eutherians–the group that evolved to include all
placental mammals, which provide nourishment to unborn young via a placenta (710).
Shundong Bi (CN), Xiaoting Zheng (CN),
Xiaoli Wang (CN), Natalie E. Cignetti (US), Shiling Yang (CN), and John R.
Wible (US) report a new Jehol eutherian, Ambolestes zhoui, with a
nearly complete skeleton that preserves anatomical details that are unknown
from contemporaneous mammals, including the ectotympanic and hyoid apparatus.
This new fossil demonstrates that Sinodelphys is a eutherian,
and that postcranial differences between Sinodelphys and the
Jehol eutherian Eomaia—previously thought to indicate separate
invasions of a scansorial niche by eutherians and metatherians—are instead
variations among the early members of the placental lineage (172).
c. 150 M
George Reber Wieland (US) researched plant material derived from
the Upper Jurassic and Lower Cretaceous beds of Maryland, Dakota, and Wyoming
where he discovered the hermaphroditic nature of the bennettitean flower and recognized an affinity between the mesozoic
cycadophyta and the angiosperms. The angiosperm with which he specially
compared the fossil type was the Tulip tree (Liriodendron) and certainly there is a remarkable analogy with the
magnoliaceous flowers, and with those of related orders such as Ranunculaceae
and the water lilies (1384).
Thomas Henry Huxley (GB) was the first to propose that birds
originated from dinosaurs. All dinosaurs he examined had strong ornithic
characteristics in the tetraradiate arrangement of the ilium, ischium, pubis,
and femur. He combined the reptiles and birds into Sauropsida (689-691).
Wyn G. Jones (AU), Ken D. Hill (AU), and Jan M. Allen (AU)
reported the 1994 discovery by David Noble (AU) in the Wollemi National Park in
Australia of Wollemia nobilis, a new
living genus and species in the Araucariaceae. This type of pine may be 150
million years old (719).
Karl F. Hirsch (US), Kenneth L. Stadtman (US), Wade E. Miller
(US), and James H. Madsen, Jr. (US) discovered a fossilized dinosaur egg
that contains the oldest known animal embryo of any kind, probably the embryo
of an allosaur from about 150 mya. X-rays of the egg detected an embryo less
than 2 cm long (652).
c. 144 M
Jean-Baptiste-Julien d' Omalius d'Halloy (BE) first used the term Terrain Cretace (Cretaceous Period) in
1822 to describe chalk and greensand of northern France (968; 969). The Cretaceous is usually noted for being the last portion of
the Age of Dinosaurs, but that does
not mean that new kinds of dinosaurs did not appear then. It is during the
Cretaceous that the first ceratopsian
and pachycepalosaurid dinosaurs
appeared. During this time, we find the first fossils of many insect groups,
modern mammal and bird groups, and the first flowering plants. The breakup of
the world-continent Pangaea, which began to disperse during the Jurassic,
continued. This led to increased regional differences in floras and faunas
between the northern and southern continents. The end of the Cretaceous brought
the end of many previously successful and diverse groups of organisms, such as
non-avian dinosaurs and ammonites. This laid open the stage for those groups
which had previously taken secondary roles to come to the forefront. The
Cretaceous was thus the time in which life as it now exists on Earth came
together. Cretaceous deposits occur in Wealden of England and Belgium; Early
Cretaceous of Niger in Africa; Late Cretaceous of Egypt; Cloverly Formation of
Montana; Early Cretaceous of Mongolia; and Early Cretaceous lacustrine deposits
of Lioning Province, China.
Jean-Jacques Pouech (FR) was the first naturalist to discover
dinosaur eggshells. The material was Late Cretaceous rock from the Pyrenees
Mountains (1058).
Henry Fairfield Osborn (US) described the Tyrannosaurus rex that Barnum Brown (US) discovered in 1902 in
Hell Creek, Montana (980).
Mary Higby Schweitzer (US), Zhiyong Suo (US), John M. Asara (US), Mark A. Allen (US), Fernando Teran Arce (US), and John R. Horner (US) performed multiple analyses of Tyrannosaurus rex fibrous cortical and medullary tissues remaining after demineralization. The results indicate that collagen I, the main organic component of bone, has been preserved in low concentrations in these tissues. The findings were independently confirmed by mass spectrometry. They propose a possible chemical pathway that may contribute to this preservation. The presence of endogenous protein in dinosaur bone may validate hypotheses about evolutionary relationships, rates, and patterns of molecular change and degradation, as well as the chemical stability of molecules over time (1167).
c. 135 M
Kenneth A. Kermack (GB), Patricia M. Lees (GB), and Frances
Mussett (GB) described the Early Cretaceous fossil Aegialodon dawsoni as the oldest known fossil to be a common ancestor
to the marsupials and placentals (746).
c. 125-130 M
c. 120 M
Robert Ashley Couper (GB) presented fossil evidence for the
earliest undisputed angiosperm pollen. It is from the Bargeman stage (late early
Cretaceous) (340).
Sushi Kumar (US) and S. Blair Hedges (US) presented evidence that
at least five lineages of placental mammals arose more than 100 million years
ago, and most of the modern orders seem to have diversified before the
Cretaceous/Tertiary extinction of the dinosaurs (773).
c. 108-115 M
c. 100 M
c. 83-70 M
Ferdinand Vandeveer Hayden (US) and Fielding Bradford Meek (US),
near the confluence of the Missouri and the Judith Rivers, collected unusual
teeth later determined by paleontologist Joseph Leidy (US) to be
those of the dinosaurs Trachodon, Troodon and Deinodon, making
the 1854 expedition by Hayden and Meek the first in North America to
uncover dinosaur remains (812).
Joseph Leidy (US) reported the findings by John Estaugh Hopkins (US), in 1838, and William Parker Foulke (US), in 1858, of the first relatively complete dinosaur skeleton. Leidy named this creature found in New Jersey, Hadrosaurus foulkii