NATS 1540 Study Guide - Final Guide: Paleogene, Herbivore, Laurasia

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8 Feb 2016
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Dinosaur Discovery: IGUANODON
The story of Iguanodon covers almost the entire history of scientific research on dinosaurs and also the entire history of the
science now known as paleontology
This animal illustrates the progress of scientific investigation on dinosaurs
The first bona fide records of the fossil bones that were later to be named Iguanodon date back to 1809
oThey compromise indeterminable broken fragments of vertebrae, the lower end of a large, very distinctive tibia
collected from a quarry at Cuckfield in Sussex – fossils collected by William Smith
Georges Cuvier
oWas a naturalist in Paris (naturalist – a philosopher-scientist who worked on a wide range of subjects associated
with the natural world [Earth, its rocs and minerals, fossils and all living organism])
o1808: Cuvier redescribed a renowned gigantic fossil reptile collected from a chalk quarry in Holland – the creature,
originally mistaken for a crocodile, was identified correctly by Cuvier as an enormous marine lizard
oThe effect of this revelation (the existence of an unexpectedly gigantic fossil lizard of a former time in Earths
history) was profound – it encouraged the search and discovery of other giant extinct “lizards”
Gideon Algernon Mantell
oHe dedicated all his spare time to completing a detailed report on the geological structure and fossils in his native
Weald (part of Kent) district
oHe sent some of his precious specimens to Cuvier in Paris for identification
oAt first, Mantell’s discoveries were dismissed as fragments of recent animals (i.e. rhino’s)
oIn the collection of the Royal College of Surgeons in London, he was shown the skeleton of an iguana, a
herbivorous lizard that had recently been discovered in South American – the teeth were similar in general shape to
those of his fossils and indicated to Mantell that they belonged to an extinct, herbivorous, giant relative of the living
iguana
oMantel published a report on the new discovery in 1825 and the name chosen for this fossil creature was Iguanodon
(meaning: ‘iguana tooth’)
These early discoveries confirmed the existence of an ancient world inhabited by improbably large lizards
The ‘Invention’ of Dinosaurs
Richard Owen
oStudied medicine, but concentrated in particular on anatomy
oDuring the 1830s, he was able to persuade the British Association to grant him money to prepare a detailed review
of all that was then known of British fossil reptiles – resulted in the publication of a stream of large, well-illustrated
volumes:
One in 1840 on mostly marine fossils
Another in 1842 on the remainder, including Mantell’s Iguanodon
Remarkable because of Owen’s invention of the new tribe of sub-order of Dinosauria
Identified three dinosaurs: Iguanodon, Hylaeosaurus, Mgalosaurus
Owen suggested that they were large, but in the region of 9-12 meters
Progressionists noted that the fossil record seemed to show that life had become progressively more complex: the earliest
rocks showed the simplest forms of life, while more recent rocks showed evidence of more complex creatures
Dinosaurs and several other groups of organisms provided evidence that life on Earth did not demonstrate an increase in
complexity over time – the REVERSE:
oDinosaurs were anatomically reptiles (members of the general group of egg-laying, cold-blooded, scaly vertebrates),
however, the reptiles living today were a degenerate group of creatures when compared to Owen’s magnificent
dinosaurs that had lived during Mesozoic times
Reconstructing Iguanodon
In 1878 remarkable discoveries were made at a coal mine in the small village of Bernissart in Belgium. The colliers suddenly
struck a seam of shale (soft, laminate clay) and began to find what appeared to be large pieces of fossil wood. On closer
inspection, the wood turned out to be fossil bone and the gold “fool’s gold” (iron pyrites). A few fossil teeth were also
discovered among the bones, and these were identified as similar to those described as belonging to Iguanodon.
oThere were 40 skeletons of the dinosaur Iguanodon excavated as well as a huge number of other animals and plants
whose remains were preserved in the same shales
The complete dinosaur skeletons unearthed in Bernissart proved finally that Owen’s model of dinosaurs such as Iguanodon
was incorrect
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oAs Mantell had suspected, the front limbs were not as large and strong as the back legs, while the animal had a
massive tail, and the overall proportions of a giant kangaroo
By the late 1860s, a series of new discoveries had been made that added considerably to the debate over the relationships of
dinosaurs to other animals
oArchaeopteryx – ‘ancient wing’
The earliest well preserved fossil bird had been discovered in Germany
It had well preserved impressions of feathers – the key identifier for any bird, forming a halo in the matrix
around its skeleton
It had 3 long fingers ending in sharp claws on each hand, teeth in its jaws and a long bony tail
oCompsognathus – ‘pretty jaw’
Another small well preserved skeleton found in the same quarries in Germany
It bore no feather impressions and its arms were far too short to have served as wings
It was a small, predatory dinosaur
Charles Darwin
oPublished On the Origin of Species in 1859
oSuggested a mechanism – natural selection – by which such transmutations might occur and how new species
appear on Earth
oNoted that although fossils provided material proof of evolution during the history of life on Earth, the geological
succession of rocks and the fossil record contained within in it, was lamentably incomplete
Thomas Huxley
o1870s he proposed that birds and dinosaurs were not only anatomically similar, but used this evidence to support the
theory that birds had evolved from dinosaurs
Careful anatomical study of the full skeleton of Iguanodon revealed that it had a hip structure known as ornithischian (‘bird-
hipped’)
oIt also had long back legs that tended in massive, but bird-like, three toed feet
oAlso had a rather bird-like curved neck, and the tips of its upper and lower jaws were toothless and covered by a
bird-like horny beak or bill
Louis Dollo
oHe was regarded as the architect of a new style of paleontology that became known as palaeobiology
oHe demonstrated that paleontology should be expanded to investigate the biology and by implication ecology and
behavior of the extinct creatures
In the mid-1920s to mid-1960s paleontology and the study of dinosaurs unexpectedly stagnated
oThe excitement of early discoveries was succeeded by more the spectacular ‘bone wars’ that gripped American
during the last three decades of the 19th century
oThese centered on a furious and sometimes violent race to discover and name new dinosaurs
oThe ‘war’ resulted in a frenzy of scientific publications naming dozens of new dinosaurs (i.e. Brontosaurus,
Stegosaurus, Triceratops, Diplodocus)
More new dinosaurs were continually being discovered and named from various places around the world, and although they
created dramatic centerpieces in museums, paleontologists seemed to be doing little more than adding new names to the
roster of extinct creatures
oThe theory of extinction based on ‘racial senescence’ arose during this time: the general thesis was that dinosaurs
had lived for so long that their genetic constitution was imply exhausted and no longer capable of generating the
novelty necessary for the group as a whole to survive. This supported the idea that dinosaurs were merely an
experiment in animal design and evolution that the world had eventually passed by
Mendel’s work was elegantly merged with Darwin’s theory in order to created “neodarwinism” in the 1930s
oNeodarwinism clarified matters enormously, Mendelian genetics provided a degree of mathematical rigor to the
theory, and the revitalized subject rapidly spawned new avenues of research
Dinosaur Palaeobiology: A New Beginning
1960s-70s the study of fossils began to re-emerge
The catalyst for this re-awakening was a younger generation of evolutionarily minded scientists eager to demonstrate that the
evidence from the fossil record was far from being a Darwinian ‘closed book’
The Discovery of ‘Terrible Claw’
John Ostrom
oHe was prospecting for fossils in Cretaceous rocks near Bridger, Montana and collected the fragmentary remains of
a new and unusual predatory dinosaur
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oHe described the new dinosaur and named it Deinoychus (‘terrible claw’) in recognition of a wickedly hooked,
gaff-life claw on its hind foot
Was a medium sized (2-3 meters in length), predatory dinosaur belonging to a group of known as theropods
oHe was far more interested in understanding the biology of this puzzling animal than in simply listing its skeletal
features
Deinonychus:
oBipedal
oFeet were unusual: three large toes on each, only two were designed to be walked upon (inner toe was held clear off
the ground)
oThe front part of the animal was counterbalanced at the hip by a long tail. This tail was flexible and muscled near
the hips, becoming very narrow and stiffened by bundles of thin, bony rods along the rest of its length
oThe chest was short and compact, and supported very long arms that ended in sharply clawed three-fingered hands
that swiveled on wrists that allowed the hands to be swung in a raking arc
oThe neck was slender and curved, but supported a very large head, which was equipped with long jaws, lined with
sharp, curved and saw-edged teeth, very large eye sockets that seem to point forward
Deducing the Biology and Natural History of Deinonychus
The forensic perspective:
oThe jaws and teeth confirm that this was a predator capable of slicing up and swallowing its prey
oThe eyes were large, pointed forward and would have offered a degree of stereoscopic vision, which would be ideal
for judging distance accurately (very useful for catching fast-movements in three-dimensional space)
This explains the relatively large brain: the optic lobes would need to be large to process lots of complex
visual information so that the animal could respond quickly, and the motor areas of the brain would need to
be large and elaborate to process the higher brain commands and then coordinate the rapid muscular
responses of the body
oThe narrowness of each foot suggests that its sense of balance must have been well developed
oThe ‘terrible claw’ on each foot was clearly an offensive weapon, evidence of the animal’s predatory lifestyle
oThe long arms and sharply clawed hands would be effective grapples for holding and ripping its prey in either of
these
oThe long, whip-like tail may have served as a cantilever – the equivalent of a tightrope walker’s pole to aid in
balance – when slashing with one foot
Useful when chasing fast moving prey
The Traditional View of Dinosaurs
Throughout the earlier part of the 20th century, it was widely assumed that dinosaurs were a group of extinct reptiles
To demonstrate this view was correct:
oRoy Chapman Andrews had discovered hat Mongolian dinosaurs laid shelled eggs
oLouis Dollo had identified impressions of their scaly skins
oTHEREFORE, their overall physiology would be expected to resemble that of living reptiles
Robert Bakker
oArgued that there was compelling evidence that dinosaurs were more similar to today’s mammals and birds
Mammals and birds are regarded as ‘special’ because they can maintain high activity levels that are
attributed to their ‘warm blooded’ or endothermine physiology
Living endotherms maintain a high and constant body temperature, have highly efficient lugs to maintain
sustained aerobic activity levels, are capable of being highly active whatever the ambient temperature and
are able to maintain large and sophisticated brains
oReported that thin sections of dinosaur bone, when viewed under a microscope, showed evidence of a complex
structure and rich blood supply that would have allowed a rapid turnover of ital. minerals between bone and blood
plasma (exactly paralleling that seen in modern mammals)
oThe range of evidence he used is:
Dinosaurs had legs arranged pillar-like beneath the body, rather than legs that sprawl out sideways from the
body (as seen in lizards and crocodiles)
Some dinosaurs had complex, bird-like lungs, which would have permitted them to breathe more efficiently
(was would be necessary for a highly energetic creature)
Dinosaurs could (based on their proportions of their limbs) run at speed (unlike any lizards or crocodiles)
oSince dinosaurs were in his opinion, large, endothermic and ‘naked’ (they were scale-covered and had neither hair
nor feathers to keep heir bodies warm), they were unable to survive a period of rapid climatic cooling and therefore
died out
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