Up until 1947, it was believed that the Cambrian Explosion marked the first true abundance of multicellular life. However, this was discovered to be untrue after Sir Douglas Mawson and R.C. Sprigg mistakenly came across numerous "fossil jellyfish" in the Ediacara Hills while observing what was originally believed to be sandstones belonging to the lowest strata of the Cambrian. At first, these finding were dismissed as "fortuitous inorganic markings."(AAS Biographical Memoirs.) Several years later however, other discoveries of segmented worms, worm tracks, and impressions of two other assemblages that bear no resemblance to any known organism, living or extinct, prompted the South Australian Museum and the University of Adelaide to undertake a joint investigation of the region. Further studies by M. F.
Glaessner, a paleontologist at Adelaide showed that the fossils were found well below the oldest Cambrian strata and that the strata actually dated from the Precambrian era. Several thousand specimens have since been collected in the Ediacara Hills. All the fossils collected were soft-bodied animals and their tissues were strengthened by spicules-needles of calcium carbonate that functioned as their support. The Ediacaran organisms were marine animals, some crawled, some were attached to the sea floor and others would swim or just freely float. Their impressions were molded in the moving sands that washed over the mud flats and were preserved as casts in the sandstone.
It is difficult to conceive how fossils of delicate soft-bodied animals could be preserved given the evidence of strong currents in the strata. However, extensive research has provided an explanation. Most of the animals settled on mud patches out of the water during calm currents. Some of these patches dried between tides and developed deep cracks.
The next shifting current would then cover these cracks with a layer of sand and the lower surfaces preserved the mud in the form of perfect casts. (Glaessner 67)The nature of these soft-bodied fossils justifies the characterization of the Precambrian as the "age of the jellyfish," however the term jellyfish only refers to a number of diverse forms, which belong to the Phylum Cnideria. (Glaessner 64) Six principle forms of animals have been discovered. The first are the rounded, discoidal impressions, resembling th...
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...nimals. Gregory Retallack, a paleontologist from the University of Oregon, suggests that these fossils were lichens.
Retallack's argument rests on the fact that the impressions were buried five kilometers under ground. He believes the fossils should have been crushed by the weight of the overlying sediment. But Retallack observed that the fossils "were as compaction resistant as some kinds of fossil tree trunks!" Because of this, Retallack concludes that these forms weren't animals, rather lichens made up of sturdy molecules such as chitin. Further evidence of this interpretation can be found in the Ediacaran organism's growth patterns and microscopic structure. (Woodmorappe 1) Despite these controversial implications many paleontologists still believe the Ediacaran animals are in fact ancestors of the animals in the existing phyla. This controversy might not be resolved until the discovery of fossils providing more information.. (Levin 267) Charles Darwin found himself in this same situation some 150 years ago. Just as he was befuddled by the absence of the ancestors of the Cambrian animals, we are puzzled by the absence of direct ancestors of these Ediacaran fossils.
Ceratopsians and Pachycephalosaurs are closely related in their characteristics. Ceratopsians processed a saddle-shaped boney frill that extended from the skull to the neck and typically had horns over the nose and eyes. The most popular was the triceratops, which could reach over 26 feet and weigh in excess of twelve metric tons. Their frills served as two major functions. It protected the vulnerable neck from being harmed. The second major function that the frill provided was due to the fact that the frill contained a network of blood vessels on its underside, which were used as a means to get rid of excess heat. The Pachycephalosaurs were considered to be bipedal. They were also found to have thick skulls, flattened bodies, and tail that were covered in an array of body rods. Pachycephalosaurs were thought to have been more than fifteen feet long and processed a skull that was surrounded by a rounded dome of solid bone. It was thought that they used their heads in combat or mating contests, but that was disproved fairly recently, which I will discuss later in the paper. Both Ceratopsians and Pachycephalosaurs were “bird-hipped” and both of these suborders contained a backwards pubic bone. Both were Marginocephilia, or “fringed heads”, which is one of three clads under the Orinthiscia order. They were also herbivore dinosaurs that inherited their fringe at the back of the skull from earlier ancestors.(2) Their classi...
For instance, the whale, the biggest mammal that lives in the water, was found to have had legs and used to dwell on land millions of years ago. While in Pakistan, Phil Gingrich, a geologist and paleontologist, came across a fossil that resembled that of a wolf but had a “bump” on the back of the skull which was found to part of an inner ear,
First, the reading states that skin decomposed into fibers and preserved as lines in the fossils. The professor opposes this point by saying that there is no fine lines on the fossils of other animals have buried in the same site. That means that the fine lines didn't come from the volcanic ash, but from the feathers of the aniamls.
...however, with further research, it came to light that this was not just a “unique species” but an entire phyla that was new to science (Adler 2013). Why a new phyla? “What made the creatures seem new is they have no living descendants. They represent entire lineages, major branches on the tree of life, left behind by evolution…” (Adler 2013). While other lineages did survive-actually a collateral predecessor of the vertebrates, and that means us! (Adler 2013).
The team of scientists consisted of a biogeologist, geochemist, and tectonic geologist with the common goal of understanding the coevolution of life and environ...
Darwin took copious notes, captured insects and animals and selected plants. These he preserved in jars and took them back to England where he thought about the implications of what he had seen. for almost three decades. What occurred to him was a simple notion: animals, plants, insects, fishes, etc., which were obviously related differed slightly and these differences seemed to be tied in with their ability to survive. Differences, which he called "adaptations," were often related to geographical factors. He also saw something similar in fossils: certainly some fish, sea shells, etc., that died and were covered up by sand, gradually turned to stone, and were caught forever in fossil form. There seemed to b...
The early tetrapods were the first vertebrates to actually walk the solid earth. They began their conquest of land in the Paleozoic era around 360 million years ago. The question many paleontologists have been asking for a long period of time is whether the anatomy for locomotion on land was developed in water for swimming purposes, or if it was adapted after the creatures became terrestrial. Recent findings of fossils indicate that the transformations of the aquatic creatures happened underwater in order to help them survive in the changing world. When looking for answers, they had to examine forearm, hip, wrist, finger, and other bones, as well as the lungs or gills of the early tetrapod fossils. This information is critical in understanding the history and the process of growth and change. It aids in learning about human evolution.
While in graduate school, Stephen Gould met fellow graduate student Niles Eldredge and they both began to study the many snail fossils. In a New York Times article Stephen Jay Gould, 60, is Dead; Enlivened Evolutionary Theory (2002), it is stated that “the two students could not find the gradual, continuous change in fossil forms that they were taught was the stuff of evolution. Instead they found sudden appearances of new fossil forms followed by long periods in which these organisms chang...
was found by scientists who were legally excavating a dig site. The scientist wanted to study the
...nd Stromatoporoids (a kind of sponge with a layered skeleton) were common rock builders of the Northern Hemisphere. Moss was common in shallow seas. Among the arthropods, the giant eurypterids (sea scorpions) have been found in the Old Red Sandston facies (see image above). The first insect was part of a group of wingless insects that feed off of debris and soil. Conodonts were vertebrate animals abundant in marine life. Many of the fish were heavily armored and the earlier fish (agnathans) had no jaws and were mud eaters and scavengers. Chondrichthians are sharklike fishes that were first found in the Middle Devonian. In terms of plants, many vascular plants emerged and a varied flora was established. There is evidence of algae, bryophytes, and charophytes. Algae and fungi also existed. As previously stated, the first known forests are from the Devonian Period.
Whales are considered to be intelligent mammals, but they live in the water despite the fact that mammals evolved on land. Paleontologist Phil Gingerich has been studying the evolution of whales since 1978. In 1978, he and his team discovered a rock in Pakistan with a skull on the inside. The skull appeared to be a wolf-like animal upon first sight, but Gingerich noticed the distinct whale ear on the skull. The skull, which had characteristics of both whales and other mammals, was that of a common ancestor of the whale known as Pakicetus. Many scientists believe that Pakicetus resembled the seal in its appearance. Pakicetus could not be considered a whale, since its backbone and limbs do not have similar features to those of a whale. Therefore, it is considered an ancestor of the whale, since it has some features of the whale and some unique features (or features of other mammals). Today’s whales have mammalian characteristics, which prove that they have evolved from a common ancestor of the mammal. A whale’s fin also has traits that are common of many species. The fin seems to be similar to that of a fish, but the bones on the inside of the fin are similar to those on a bird’s wing, a monkey’s arm, and a frog’s limb. This seems to be proof that these organisms, and many others, all evolved from a common ancestor. Other proof that whales have evolved over time lies in Egypt in the Valley of Whales, where over 400 fossils of whales currently lie. The desert used to be a large sea that was home to a few kinds of whales. In the Valley of Whales, Gingerich discovered the Basilosaurus, which had small hind legs, toes, and a mobile knee and lived 35-41 million years ago. This fossil is considered to be a transitional fossil, since it ha...
regions of the earth can indicate which rock layer is older than the other. Trilobite fossils
The Burgess Shale Fauna is a fauna that was constructed based on a group of fossils that were initially found, in the Burgess Shale area in the Canadian Rockies (Gould, 1989). They are a very important group of fossils as “modern multicellular animals make their first unprotected appearance in the fossil record some 570 million years ago” through this group (Gould, 1989, pp. 24). Moreover the Burgess Shales are known to have preserved the soft parts of animals enabling us to get a better understanding of life at the time.
There are several theories about how the Cambrian Explosion started. There were major changes in marine environments and chemistry from the late Precambrian into the Cambrian, and these also may have impacted the rise of mineralized skeletons among previously soft-bodied organisms. One theory as to what happened is that oxygen in the atmosphere, with the contribution of photosy...
With its abundance of genera, the Burgess Shale is one of the world’s most important fossil fields. It’s discovery in 1909 led to over 100 years of paleontological study in the Canadian Rockies, a majority of which has been carried out in two quarries known as the Walcott and Raymond quarries (Hagadorn, 2002). Though he was originally in search of trilobites in the Burgess Shale Formation, paleontologist Charles Walcott also discovered a diverse group of soft- and hard-bodied fossils, from algae and sponges to chordates and cirripeds (Hagadorn, 2002). Soft-bodied fossils are incredibly rare due to their delicate structure and susceptibility to decay, so it is hard-bodied fossils that more regularly occur in fossil findings. However over 75,000 soft-bodied specimens have been found in the Burgess Shale formation (Hagadorn, 2002). These specimens are preserved in layers of shale formed from deposits of fine mud. One of the most significant species discovered is the Pikaia gracilens. Believed to be an early chordate, the Pikaia gracilens existed very close to the beginning of the evolutionary path that ultimately lead to humans (McGraw-Hill Encyclopedia, 2006).