Fossils Part 2

Fossilization (Taphonomy)

Critical part of the process known as taphonomy, or the study of remains of organisms after they die (the word was derived from the Greek taphos, meaning grave-burial, and nomos, meaning law). The concept was introduced to paleontology in 1940 by the prominent Russian paleontologist and science fiction author Ivan Efremov (also spelled Yefremov) to describe the study of the transition of organic remains, including entire intact bodies, dissembled parts or products, from the biosphere to the lithosphere, meaning the eventual conversion of living organisms to fossil assemblages.

The motivation behind the study of taphonomy is to better understand biases present in the fossil record. Although fossils may seem to some to be ubiquitous in sedimentary rocks, they are actually somewhat rare. Paleontologists cannot draw the most accurate conclusions about the lives and ecology of the fossilized organisms without identifying and understanding the processes involved in their fossilization. Therefore, taphonomy includes the organism’s life-history, type-location of death, decomposition, post-mortem transport (if any), burial, compaction, and other chemical, biologic, or physical activities that affect the remains of an organism. Recognition of taphonomic processes that have taken place leads to a more complete understanding of paleoecology and even the life-history of a once-living organism.

Since most of those who study geoscience know that the world is very old and that many billions of animals have lived and died between the time when plants and animals first appeared, why is the environment not simply awash in fossils? Here’s the answer in a nutshell: because for organisms death is guaranteed while preservation is not.

To understand that answer we have to focus on the underlying problem: how does anything become fossilized? And that’s where taphonomy comes in, by elucidating critical elements in the taphonomic process: life—death—preservation—survival—discovery. The fossilization process starts with life (as many young student observers of tenured university faculty and administrators approaching retirement will readily attest) because the way an organism lives provides a bias with respect to its potential for preservation.

Organisms living in or in close proximity to lacustrine or tidal marsh environments have much greater chances of having their remains rapidly covered with sediments and fossilized than do condors or mountain goats living in a desert far from most sources of rapid burial and sedimentation. As an example of a life having high fossilization potential, imagine a shore bird falling dead in a near-shore environment where its feathers are weighed down with clay-rich water and that night and the next many nights it is covered with an inch or more of sand, silt or mud until it is buried under several yards of moist, heavy materials. Moreover, an animal’s position in the food web also affects its fossilization potential since organisms at the bottom of the web are far more numerous than the top predators.

Real World Examples of animals whose lives and deaths and preservation contributed to very high fossilization potentials are those so remarkably preserved in the Burgess Shale and the recently discovered nearly complete fossil skeleton of an ancient aquatic bird in the Gansu area of China, Gansus yumenensis.[1] How and where an organism dies also affects its fossilization potential. For example, a zebra dying on the South African veldt stands next to no chance of being preserved since either predators or scavengers (including those that crush and eat the bones) would clean up its remains like hungry teenagers disappearing a fast-food meal. But the chances of fossilization of a clam or a crab dying at the beach are considerably greater.

Preservation encompasses ways an organism’s remains survive after death and its transition into a fossil. Rapid burial is the best method to ensure transition into the preservation stage and is a common process at the Earth’s surface that occurs on a regular basis (again, the Burgess Shale is a wonderful example). Floods, mass wasting episodes, storms, and volcanic eruptions can deposit sediments over periods of time ranging from minutes to days. A well-known historical example is the sudden volcanic ash fall that buried Pompeii and Herculaneum.

Fun Stuff: Actual examples of what might humorously be called “fossil” graffiti preserved on the walls of the two Roman cities include:

“Atimetus got me pregnant.”

“I fucked a lot of girls here.”

“Phileros is a eunuch.”

“Once you are dead, you are nothing.”

“May I always and everywhere be as potent with women as I was here.”

Back to more serious stuff. Not all types of landscapes are preserved equally in the geological record, leading to a heavy bias towards shallow, near-shore marine and lacustrine environments. In addition, not all periods of geological history are preserved equally, witness the paucity of fossils from periods earlier than the Cambrian. Recent Earth history is far better preserved if only because not as much time has elapsed during which erosion or destruction via heat and pressure can occur. Burial also protects the dead organism from being consumed by higher or lower food chain organisms and from mechanical (abrasion and break-up) and chemical (decay and disintegration) processes. Although in the vast majority of cases decay is an inevitable part of death, organisms with hard parts (shell, bone, claws, teeth) have a much higher preservation potential than organisms that are entirely soft-bodied or that possess fragile hard parts.

Preservation comes in various types. An unaltered state is the rarest form of preservation in the far greater majority of the geologic record in which fossils are found but is more frequent in recently formed sedimentary environments. Types of unaltered preservation where even the soft body parts are preserved include: mummification, encasement in tar or other hydrocarbons (as can be seen at the Rancho La Brea Pits in Los Angeles), encasement in amber (such as frogs, insects, or leaves), encasement in sediment, and freezing, as in the case of an 18,000-year-old frozen Siberian woolly mammoth that was on display at the 2005 World Exposition in Aichi, Japan. However, most commonly only the hard skeletal materials are preserved after decomposition of soft body parts.

Preservation by means of molds and casts entails creation of a type of replica of the organism’s hard parts. In general, a mold is an impression of a bone or shell in lithified sediment, forming a mirror image of the original part. Molds can be internal, an impression of the inside surface of skeletal hard parts, or external, an impression of the outside surface. A cast is formed when a mold is filled with fine sediment and is therefore a true replica not a mirror image of the original hard part.

A common form of preservation involves dissolution and replacement or recrystallization (alteration) of original hard materials by chemical or physical means. Replacement, sometimes on a molecule by molecule basis, most often occurs when various minerals, typically contained in percolating groundwater, fill in voids after dissolution of original skeletal material. Common secondary replacement minerals include silica (SiO₂) and pyrite (FeS₂). The process of the physical re-arrangement of crystalline structure of skeletal material is known as recrystallization, which is a common phenomenon in shells that were originally aragonite or calcite (both forms of calcium carbonate—CaCO₃).

Carbonization or the formation of carbon films is another type of fossilization and is typical for such organisms as plants and insects. After an organism (most typically a plant) dies, internal volatile organic compounds disperse and leave behind residues that form a coal-like black carbon film that preserves the outline and sometimes considerable organic details. Those thin films of carbon are often found on planes of sandstone or shale.

Permineralization or petrifaction is a type of preservation in which the soft tissue of the organism has decomposed and the remaining hard parts are flooded with groundwater saturated with secondary minerals, especially calcium carbonate (calcite) or silicate that precipitates out and fills the gaps/pores/interstitial spaces of the dead organism but does not replace existing material. Minute details are often well preserved, even down to the cellular level. Cementation occurs with time and pressure as secondary minerals lithify to form a rock (fossil) in the place of the original bone, teeth, shell, or wood, preserving an amazing amount of detail. Real World Example: A great and very popular illustration of this form of fossilization is petrified wood, as can be seen in the Petrified Forest National Park in northern Arizona. Vietnam produces the largest commercial quantities of black and brown petrified wood sold globally as well as some of the largest individual pieces. For example, in 2002 a 6.7 meter long rock with a diameter of 40-50 cm, was found in Hon Khoi, Vietnam, which is located about 50 miles north of Cam Ranh Bay.

Author’s Note: The celebrated mystery author Patricia Cornwell brought worldwide attention to human taphonomy in her best-selling 1994 novel, The Body Farm, in which she discussed the very real Anthropological Research Facility at the University of Tennessee—Knoxville, which is engaged in an effort to apply principles of physical anthropology to the study of human decomposition, or what is called forensic taphonomy. Check out the book, it contains a fictional but well-written account of the work of William Bass, founder of the decay research facility.

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[1] Hai-lu You, et al. 2006. Nearly Modern Amphibious Bird from the Early Cretaceous of Northwestern China, Science 312(5780): 1640-1643.

Fossils Part 1

Fossil

Organic remains or traces of once living organisms preserved in rocks and minerals over time through a variety of methods, including casts, tracks, impressions, and lithified body parts. Real World Examples: Many paleontologists believe that a particularly inhospitable stretch of the Gobi Desert, near the Mongolian provincial capital of Ukhaa Tolgod, is home to the world’s richest and most diverse deposits of dinosaur and early mammal remains from 80 mya, a critical time for life in the Cretaceous.

In the last decade or so, paleontologists estimate that they have found 1,000 mammal skulls, which amounts to 90 percent of all the recovered mammalian specimens from the Cretaceous, and bones from 1,000 lizards, not to mention the fossilized remains of many different kinds of dinosaur and their nests and eggs. For most of us moderately educated common folk, the most famous fossils are those of the larger dinosaurs, especially such those scare-your-wits-out carnivores like Tyrannosaurus rex.

However, many budding geoscientists have been excited by the discovery of a giant snake, named Titanoboa cerrejonensis, by its discoverers. The size of the snake's vertebrae suggests it weighed about 2,500 pounds and measured 42.7 feet from nose to tail tip. Geoscientists from the University of London discovered the fossil in the Cerrejon Coal Mine in northern Colombia, South America, in 2008. The geoscientists used the snake's size to estimate the Earth's temperature during the time it lived in tropical South America (somewhere between 58 to 60 million years ago). Paleontologists have long known an age's average temperature roughly correlates with the size of its cold-blooded animals. By their estimate, a snake of Titanoboa's size would have required an average annual temperature of 86° to 93° F to survive. By comparison, today's average yearly temperature of Cartagena, Colombia, is 82.4° F.

Another fairly recent fossil that has excited students was the 2001 discovery of the bones of a 110 million years-old, 40-foot crocodile by researchers at Yale University and at the University of Chicago in the Cretaceous rocks in central Niger, Africa, in what is part of the Tenere Desert. It was estimated that the crocodile, named Sarcosuchus imperator by the researchers, weighed about 16,000 pounds. Measurements from three adult skulls resulted in an estimate of total adult body length to be between 39 and 42 feet long.

Fossil Assembly (Lagerstätte)

Lagerstätte is a German word meaning “resting place” or “storage place” that recently has been borrowed by paleontologists and applied to fossil locations of extraordinary richness or completeness (plural: lagerstätten). A lagerstätte is a spectacular rarity and a few dozen are scattered through the Earth and are more valuable to science than the rarest and most precious gems. Paleontologists define Konservat-Lagerstätten (conservation Lagerstätten) as locations known for the exceptional preservation of fossilized organisms, including soft parts preserved as impressions, casts, or “shadows.” Those locations are examples of incomplete biological recycling where anoxic conditions (oxygen-free mud) sufficiently suppressed bacterial decomposition for the initial casts of soft body parts to be recorded.

Konzentrat-Lagerstätten (concentration Lagerstätten) are defined as fossil deposits with concentrations of disarticulated organic hard parts, such as a bone bed. They are less spectacular in scale and scope than the more famous Konservat-Lagerstätten. Deposits with a high concentration of fossils that represent an in-situ community, such as reefs or oyster beds, are not considered Lagerstätten. However good they may be, lagerstätten still have preservational biases, in that certain fossils are not preserved in the sedimentary beds due to a variety of adverse environmental conditions, especially but not only geochemical in nature.

Real World Examples: Perhaps the best known lagerstätten for most Americans is the Rancho La Brea Pits in Los Angeles, which has the best studied assemblages of Pleistocene vertebrates, including over 135 species of birds and 60 species of mammal, including woolly mammoths and mastodons, grey and dire wolves, long-horned bison, ground sloths, saber-toothed cats, and many other recently extinct creatures that were fossilized by the hundreds in tar.

Another incredible location is the Burgess Shale in the Canadian Rockies in Yoho National Park, British Columbia, where the Cambrian Explosion is so beautifully documented. Even more important with regard to its significant assemblage of Cambrian Exploxion fossils is the Chengjiang Biota in the Maotianshan Shales of Yunnan Province, China, near the city of Kunming. The Chengjiang Biota is extraordinarily diverse, including many excellently-preserved soft-bodied fossilized organisms and has been designated by paleontologists as arguably the most significant exceptional preservation above the Precambrian-Cambrian boundary.

The justly famous Solnhofen Limestone beds in Bavaria, Germany, are located halfway between Nuremberg and Munich, where the famous dinosaur-bird, Archaeopteryx, was first found in feathered and toothful splendor. The assemblage includes sea jellies, the wings of dragonflies, the imprints of stray feathers, and many terrestrial plants. The range of fossils, some of which are truly spectacular, preserved in sticky carbonate muds that trapped insects and even a few small dinosaurs, provides a comprehensive picture of a local Jurassic ecosystem with over 600 identified species, including 29 kinds of pterosaur ranging from the size of a sparrow to four feet in length.

Perhaps the most famous fossil in the world is the Solnhofen Limestone's Berlin specimen of Archaeopteryx. With its reptilian-like teeth and tail with the feathers of a bird, it was the ideal “missing link” Darwin’s supporters took pride in pointing to as irrefutable proof of his theory of evolution. The Messel Pit near Darmstadt, Germany, is one of the richest Konservat-Lagerstätten in the world, with more than 10,000 finds to date from the Middle Eocene Period (Geiseltalian), about 50 mya. The Pit provides the best preserved evidence of Geiseltalian flora and fauna ever discovered. Many of the fossils not only feature extensive preservation of structural integrity but also such soft body parts as feathers, fur, and "skin shadows." In May 2009, scientists from Norway, Germany, and the U.S. published research on what is certainly one of the most famous fossils from the Messel Pit, a 95 percent preserved primitive primate fossil (named Darwinius masillae and nicknamed Ida, pronounced Ee-da) that may either be an evolutionary link connecting prosimians (lemurs) and anthropoids (apes, monkeys, and humans) or an evolutionary dead end. Since the dust has yet to settle on that particular argument, interested students should watch developments in the literature.

Since the 1990s, what is perhaps the world's largest deposit of dinosaur bones has been identified inside a 1,500-foot long, 80-foot deep ravine in the City of Zhucheng in Shandong province on China’s eastern coast. The site contains certainly one of the world’s greatest deposits of dinosaur fossils, at least in terms of sheer volume, with more than 8,000 individual fossils identified as of 2012, with many more sure to be found. Among the more significant fossils found there are Gigantoraptor, Guanlong, Incisivosaurus, Limusaurus, Meilong, and Microraptor, Zhuchengtyrannus magnus.

Kinds of Fossil

The remains of plants and animals may be preserved through a variety of natural processes including mummification, freezing, molds and casts, impression, petrifaction, mineral replacement, carbonization, and direct preservation of teeth, bones, and shells in animals of relatively recent origin. Other less common kinds of fossil include coprolites (fossilized excrement), burrows (tubes made in silt or mud by animals such as worms), and gastroliths (stomach stones used in the stomachs of extinct reptiles to grind food). A trace fossil, such as a mold or cast or other evidence of life, is also known as an ichnofossil.

Real World Examples: Fossils of different Tyrannosaurus species have been found in the Lance Formation of Eastern Wyoming; the Hell Creek Formation of Eastern Montana, Southwestern North Dakota, and Northwestern South Dakota; the Livingston Formation of Montana; the Javelina Formation of Big Bend Texas; the Laramie Formation of Colorado; the McRae Formation of New Mexico; the Scollard and Willow Creek formations of Alberta, Canada; and the Frenchman Formation of Saskatchewan, Canada. And while you're in Canada, you should visit Dinosaur Provincial Park, which occupies an area of 73 square kilometers along the Red Deer River near the center of southern Alberta. One of the largest concentrations of dinosaur footprints known in North America can be found in the Connecticut Valley. Many different types of fossil track impressions have been found in the Valley's sandstone of the early Jurassic period (200 mya). Two thousand Eubrontes tracks (a large three toed dinosaur that was closely related to the western genus, Dilophosarus) were discovered on a single layer of rock. Some of the best examples are preserved at Dinosaur State Park in Rocky Hill, a few miles south of Hartford, Connecticut. Another type of footprint was discovered at Laetoli, Tanzania, in 1978 by a team led by Mary Leakey that may have been made about 3.6 millions years ago by hominids who were members of the species, Australopithecus afarensis. The track is among the longest made by early hominids and is still among the most controversial, owing to scientific disagreement as to which group of hominids made the footprints in what was then loose volcanic ash. But in terms of shear numbers, probably more Americans have visited Petrified Forest National Park in northern Arizona than any other fossil location in the U.S., with its fascinating fragments and even large logs of fossilized wood, which is actually a molecule by molecule replacement of organic matter with silica.

Fossiliferous

Rock in which fossils are profuse, for example, crinoids, brachiopods, and other marine invertebrates.

Fresh Water Trends and Issues

Fresh water is any water that is not salty or contaminated. Inland lakes, ponds, rivers, wetlands and groundwater constitute the fresh water biome but are less than one percent of the total global water supply. Author’s Note: Although most of the world’s fresh water is stored in glaciers and icecaps (about 7,000,000 cubic miles), mainly in the polar regions and in Greenland, that water is not readily available to human consumption so is not considered in this post. Fresh water ecosystems are critical to terrestrially based flora and fauna, including humans, because they provide water for natural habitat, agriculture, drinking, energy, food processing, industry, recreation, transportation, and many other cultural and economic enterprises. According to the United Nations Environment Programme (UNEP), although most of the world is not running out of fresh water, a number of nations and regions face chronic fresh water shortages that are likely to worsen as the result of unsustainable withdrawal rates arising from increasing demands, inefficient use or management, changing climatic and precipitation patterns, difficulty in finding new water resources, and pollution and source water contamination (including both surface-water and groundwater).

Anyone possessing even a modest knowledge of world climate patterns knows that fresh water is not uniformly distributed. Deserts and semi-arid regions are by definition water-deficient. However, even areas with moderate to high amounts of natural annual precipitation can suffer from shortages of fresh, drinking water. Those shortages can and do affect national and regional security by causing human health problems, increasing conflicts between competing users, and damaging ecosystem health all of which alone or in combination may result in ecosystem collapse, population displacement, increases in mortality and potentially resulting in conditions that approach chaos and societal collapse. In 2002, the UNEP issued a chilling statement: “If present consumption patterns continue, two out of every three persons on Earth will live in water-stressed conditions by the year 2025.”

Real World Examples: It’s easy to point to various African countries, China (whose two great rivers, the Yangtze and the Huang, are basically so polluted that they no longer supply drinking water), India, Indonesia, or even England, suffering as it is under a ten-year drought, as having chronic and systemic water shortages and numerous other challenges in the provision of fresh water to their people. It’s also easy to hold up Russia as a horrific example of a nation where environmental damages to its fresh water supplies are so severe that the word chaos is not too harsh a description. However, rather than searching the world for the worst examples of countries or regions where fresh water supply is problematic, it may be more instructive to stay closer to home and examine the American experience.

We don’t have to look too hard to find fresh water problems all throughout the Great Plains, where drawdown of the Ogallala Aquifer has resulted in decreasing agriculture since the 1970s. Or in Clark County and Las Vegas, Nevada, where out of control urban growth from the 1960s to the present all but requires the mining of fossil groundwater throughout much of the southern part of the State so that gaming-inspired development can continue. Historical Background: The Colorado River Compact is a 1922 agreement among seven Southwestern states (Colorado, New Mexico, Utah, Wyoming, Nevada, Arizona, and California) in the basin of the Colorado River governing allocation of rights to the River’s water among the parties of the interstate compact. In recent years, the Compact has become the focus of great concern following a protracted decrease in rainfall in the Southwest. Specifically, the amount of water allocated was based on an expectation that the River’s average annual flow was 16.4 million acre feet. Recent tree ring studies, however, concluded that the long-term average water flow of the Colorado is significantly less. Estimates have included 13.2 million acre feet, 13.5 million acre feet, and 14.3 million acre feet per year. Many analysts have concluded that the Compact was negotiated in a period of abnormally high rainfall and that the recent dry conditions are not a drought but a return to historically typical patterns. The decrease in rainfall has led to widespread dropping of reservoir levels, particularly at Lake Powell, where the exposure of long-inundated canyons has increased calls for the permanent removal of the reservoir.

Author’s Rant: Several years ago, the U.S. began pressuring Canada to sell some portion of its abundant fresh water resources, despite that fact that massive diversions would likely prove environmentally disastrous, especially for the Canadians but also for Americans since exotic organisms could be introduced to our ecosystems. Of course, that fresh water infusion would certainly not create the best opportunity for Americans to curb our already profligate water use. For very informative expositions of why and how the alarming water transformations have occurred, see the following materials.

Fred Pearce, When the Rivers Run Dry: Water — The Defining Crisis of the Twenty-First Century, Boston: Beacon Press, 2006;

Alex MacLean, Over: The American Landscape at the Tipping Point, New York: Abrams Books, 2008;

Pacific Institute, The World’s Water 2008-2009, Washington, D.C.: Island Press, 2010.

For something a little dated but still absolutely on-point, see Marc Reisner’s classical, Cadillac Desert: The American West and its Disappearing Water, New York: Penguin, 1993.

Web devotees should consult: “Fresh water Ecoregions of the World” (FEOW), a cooperative venture of the Nature Conservancy and the World Wildlife Federation at www.feow.org; Aaron Wolf’s “Transboundary Fresh water Disputes Database” at http:ly/osu_TFDD; or the USGS’s authoritative “Water Use in the United States” http://water.usgs.gov/watuse/. For directly related information, see desertification, global water shortage, salinization, and sustainable development.

American Justice

I watched a national news program recently that dealt with a man who had been tried and convicted of murdering his wife. He was sentenced to life in prison despite no evidence or witness testimony tying him to his wife's death. Seven years ago his defense team realized that a critical piece of evidence in the possession of the country sheriff contained stains that could be tested for DNA. They were confident the analysis would demonstrate their client’s innocence.

The county prosecutor fought the testing from 2005 to 2010, repeatedly and publicly disparaging the tests as “irrelevant”, “silly”, and “grasping at straws”. The only reason he finally released the evidence to a lab was because he was ordered to do so by the state Court of Appeals. The DNA tests found the blood of the dead woman as well as that of a man whose DNA matched that of a convicted offender in a national DNA database who was not then incarcerated and whose DNA was found on the body of another woman murdered two years after the first victim. By the time of his release from prison by court order, the wrongly convicted husband had served 25 years.

Most people realize that the American system of justice is imperfect. Prosecutors, defense attorneys, police detectives, judges, and jurors are human and subject to err. We make mistakes, no doubt.

What concerns me is not only that an innocent man was convicted but that the prosecutor fought so hard to prevent potential evidence from being tested. The prosecutor who fought the DNA testing claims he did so with honest intentions. According to that prosecutor, his five-year, sustained opposition to DNA testing was done in good faith. Frankly, although I'm not a lawyer and know little about criminal law, that seems very, very hard to believe. In fact, I do not believe that claim.

My nephew is a microbiologist who for years was in charge of a major national lab division where dozens of DNA samples are analyzed every day of the year. At a qualified lab and in the hands of trained technicians, the procedure is complex but not extraordinarily difficult.

So, why did the prosecutor fight so hard to disallow DNA testing and as a direct result keep a wrongly convicted man in prison for another seven years? Exactly how was justice served by that opposition? I have no answers to those very disturbing questions.

The U.S. Supreme Court has ruled (Imbler v. Pachtman) that prosecutors have absolute immunity from civil lawsuits over how they mishandled criminal cases in court, no matter how critical, intentional, or obvious those abuses. That immunity applies even when prosecutors intentionally failed to disclose evidence that could have demonstrated someone's innocence or when they deliberately violated rules designed to ensure trials are fair to the accused.

Prosecutors at every level know they can commit misconduct with impunity since their powers are basically unchecked. And if readers think that prosecutors who engage in deliberate misconduct can be disbarred or prosecuted, a 2010 study by USA Today found that of 201 documented cases of federal prosecutor misconduct, no disbarments or convictions resulted. None.

So, the next time you read about a prosecutor claiming he acted in “good faith” my advice is to be more than a little skeptical.