NATS 1540 Midterm: Dino Midterm Review
Course CodeNATS 1540
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Dinosaurs as birds
Dromaeosaurian (Droma like Dramaesaurian ! Lol) theropods
‘thinning’ of the tail: the tail becomes very narrow and stiffened by bundles of long, thin bones, the only
flexible part being close to the hips
thin, pole-like tail may well have been valuable as a dynamic stabilizer to assist with the capture of fast-
moving and elusive prey
dramatically changed the pose of these animals because it was no longer a heavy, muscular cantilever for
the front half of the body. If no other changes had been made to its posture, such a dinosaur would have
been unbalanced and constantly pitch forward on to its nose
To compensate for the loss of the heavy tail , bodies of these theropods were subtly altered:
pubic bone rotated backwards so that it lay parallel to the ischium
also seen in
This layout of hip bones, with the pubis rotated backward, is seen in living and fossil birds as well as
the gut and associated organs could be swung backwards to lie beneath the hips
change shifted the weight of the body backwards, and compensated for the loss of the heavy
•long arms and three-clawed hands were important for catching and subduing their prey and needed
to be very powerful
•shorten the chest in front of the hips
•chest shows signs of being stiffened
•chest strengthened to help securely anchor the arms and shoulders to withstand the large forces
associated with grappling and subduing prey
reflects the predatory habits of these animals
Birds also have a short, and greatly stiffened, chest region to withstand the forces associated with anchoring
the powerful flight muscles.
early bird-like fossil exhibits many maniraptoran theropod features:
•tail is a long and very thin set of vertebrae that anchored the tail feathers on either side
•hip bones are arranged with the pubis pointing backward and downward
•front of the chest there is a boomerang-like furcula
•jaws are lined with small, spiky teeth, rather than a more typical bird-like horny beak
•the arms are long, jointed so that they can be extended and folded just as in theropods
•hands are equipped with three sharply clawed fingers that in their arrangement and proportions are
identical to those seen in maniraptoran theropods
These dinosaours were thought to be warm blooded due to :
1. Many of these feathered dinosaurs were small-bodied (20–40 centimetres long)
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small animals have a relatively large surface area and lose body heat to the environment very quickly ;
insulation using filaments (which mimic the fur seen on the bodies of living mammals) and downy feathers
are likely to have been a necessity if these creatures generated internal body heat
2. Possession of an outer insulatory layer to the skin would have made basking difficult, if not
impossible, because the insulatory layer would have inhibited their ability to gain heat from the sun.
Basking is the ectotherm’s (cold-blooded) way of gaining body heat, so a furry or feathered lizard is
a biological impossibility.
CHAPTER 8 - The Future of Research on the Past
K-T extinctions: the end of dinosaurs
•none were to be found in rocks younger than the end of the Cretaceous period (approximately 65
Ma). In fact, it came to be recognized that the very end of the Cretaceous Period, leading into the
Tertiary Period (now universally referred to as the K-T boundary) marked a major time of change.
Many species became extinct and were replaced in the Early Tertiary by a diversity of new forms:
the K-T boundary therefore seemed to represent a major punctuation in life and consequently a
•Late Cretaceous times; a multiplicity of sea creatures, ranging from giant marine reptiles
(mosasaurs, plesiosaurs, and ichthyosaurs), to the hugely abundant ammonites, as well as a great
range of chalky planktonic organisms; while in the air the flying reptiles (pterosaurs) and
enantiornithine birds disappeared forever.
•detailed studies of the ecological make-up of the time zones closest to the K-T boundary. The
consensus suggested that there was a shift to progressively more seasonal/variable climatic
conditions at the end of the Cretaceous Period
•mirrored in the decline of those animals and plants less able to cope with more stressful climatic
conditions. This was linked, rather inconclusively, to tectonic changes towards the close of the
Cretaceous Period; these included marked sea-level rises and greatly increased continental
•general impression was that the world was slowly changing in character, and this eventually
culminated in a dramatic faunal and floral turnover.
•changes in plankton diversity at the K-T boundary. It seemed logical to assume that the interval
between the Late Cretaceous and Early Tertiary might simply represent a longish period of ‘missing’
time – a genuine gap in the continuity of the fossil record
•could measure the amount of cosmic dust that was accumulating in boundary sediments in order to
be able to provide an estimate of the extent of this presumed geological gap
•found that the boundary layer, which was represented by a thin band of clay, contained enormous
quantities of cosmic debris that could only be explained by the impact and subsequent vaporization
of a gigantic meteorite
•Considering the effect of the impact of such a giant meteorite, they further proposed that the huge
debris cloud generated (containing water vapour and dust particles) after the impact would have
shrouded the Earth completely for a significant period of time
•Shrouding the Earth in this way would have shut down photosynthesis of land plants and planktonic
organisms, and triggered the simultaneous collapse of terrestrial and aquatic ecosystems
•1980s, more and more teams of researchers were able to identify cosmic debris and violent impact-
related signals in K-T boundary sediments from the four corners of the globe.
•some of the Caribbean islands, such as Haiti, deposits of sediments at the K-T boundary not only
showed the impact signal, but immediately above this an enormous thickness of breccia (broken
masses of rock that had been thrown together). This, as well as the greater thicknesses of the
meteorite debris layer and its chemical signature, prompted the suggestion that the meteorite had
impacted somewhere in the shallow sea in this area
•1991, the announcement was made that researchers had identified a large subterranean meteorite
impact crater, which they called Chicxulub, on the Yucatán Peninsula of Mexico. The crater itself
had been covered by 65 million years of sediment, and had only been visualized by studying
seismic echoes of the Earth’s crust (rather like the principle of underground radar). The crater
appeared to be approximately 200 kilometres across and coincided with the K-T boundary layer
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RESULTS OF THE IMPACT
•‘target’ rocks (shallow sea deposits) and their behaviour under high-pressure shock, have shed
light on the early phases of the impact and its environmental effects
•the meteorite would have impacted on a sea floor that was naturally rich in water, carbonate, and
sulphate; this would have propelled as much as 200 gigatons each of sulphur dioxide and water
vapour into the stratosphere.
•fossil record certainly suggests that floral extinctions were particularly severe in this area, but more
work elsewhere is needed before this pattern can be verified
•within a few months light levels and temperatures would have begun to rebound because of the
thermal inertia of the oceans, and the steady fall-out of particulate matter from the atmosphere
•sulphur dioxide and water in the atmosphere would have combined to produce sulphuric acid
aerosols, and these would have severely reduced the amount of sunlight reaching the Earth’s
surface for between 5 and 10 years. These aerosols would have had the combined effects of
cooling the Earth to near freezing and drenching the surface in acid rain.
•Clearly these estimates are based only on computer models, which may be subject to error.
However, even if only partly true, the general scope of the combination of environmental effects
following the impact would have been genuinely devastating, and may well account for many
aspects of the terrestrial and marine extinctions that mark the end of the Cretaceous Period.
•One set of interpretations of the core data indicates that the impact crater may have been made as
many as 300,000 years before the K-T boundary. The interval is represented by 0.5 metres of
•evidence has been used to propose that the end Cretaceous event was not focused on a single
large meteorite impact, but several large impacts that occurred right up to the K-T boundary – the
cumulative effect of which may have caused the pattern of extinctions.
•Clearly these new findings indicate that more research and more debate will undoubtedly take
place in years to come. Not least among these are the data concerning massive volcanic activity
that coincided with the end Cretaceous events
Dinosaur research now and in the near future
•Many research programmes in palaeobiology can be planned, and indeed have an intellectually
satisfying structure to them, in order to explore specific issues or problems
•serendipity also plays a significant role: it can lead research in unexpected directions that could not
have been anticipated at the outset
•can also be influenced strongly by spectacular new discoveries – nobody in the early 1990s would
have been able to predict the amazing ‘dinobird’ finds that were made in China in 1996
•technological advances in the physical and biological sciences also play an increasingly important
part in research, allowing us to study fossils in ways that were, again, unimaginable just a few
•To take advantage of many of these opportunities it is important to have at hand people who share
a number of characteristics. Above all, they need to have an abiding interest in the history of life on
Earth and naturally inquisitive temperaments. They also need some training in a surprisingly wide
range of areas. While there is still an importance in the individual scientist working and thinking
creatively in some degree of isolation, it is increasingly the case that multidisciplinary teams are
needed to bring a wider range of skills to bear on each problem, or each new discovery, in order to
tease out the information that will move the science a little further forward.
•We, as a human race, could simply chose to ignore the history of life on Earth, as can be
interpreted, in part at least, through the study of fossils.
•We as humans currently dominate most ecosystems, either directly or indirectly, but we have only
risen to this position over the past 10,000 years of life on Earth.
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