Feathered Dinosaur and Birds Team Members: Amanda, Brian, Carrie, Melinda, Melissa, Niel, Sabrina, and Wendy Introduction This report explores the connection between dinosaurs, namely theropods, and modern birds. In our exploration we will be examining topics covering: feathered dinosaurs, the origin of feathers including there evolution, what is a bird and what is known about the first “bird”, the transition from theropods to birds, and the origin of birds that link them to the theropods. There is a paleontologist saying that we've come to agree with, “If it acts like a bird, and has the structure like a bird, it must be a dinosaur.” 1. Feathered Dinosaurs A. What do we know about the evolution of the feathered dinosaurs; what are some of the discoveries of feathered dinosaurs and who discovered them? - Melinda, Niel? Feathered dinosaurs –Niel In the search for the connection between birds and dinosaurs, it is important to investigate the dinosaurs that have been found with feathers. One of the great discoveries that has linked dinosaurs to birds is the fact that in China a dromaeosaur was found that has remiges. “Remiges are like the flight feathers of birds, with a central stiffening vein fro m which branched fibres radiate”(Xing Xu). This discovery shows that not only were there feathered dinosaurs, but some of them may have been capable of flight. In China, there have been discoveries of at least two other dinosaurs that are thought to of had feathers, Scansoriopteryx and Epidendrosaurus; these two are “the first undoubtedly arborial (tree- climbing) dinosaurs” (Xing Xu). There is a lot that is not confirmed about these dinosaurs, everything from the time they were alive to the possibility that they were not of the same species. Oviraptorosaurs are thought to of had feathers because of how the bodies were shaped (Xing Xu,). Nomingia, one type of Oviraptorosaur, has a short tail that is similar to that of birds; the main similarity is the “pygostyle” (Xing Xu). This structure is used in modern bird to turn the tail feathers because the pygostyle has this specific use some scientists think that the Nomingia had feathers.
Transcript
Feathered Dinosaur and Birds
Team Members: Amanda, Brian, Carrie, Melinda, Melissa, Niel, Sabrina,
and Wendy
Introduction This report explores the connection between dinosaurs, namely theropods, and modern
birds. In our exploration we will be examining topics covering: feathered dinosaurs, the
origin of feathers including there evolution, what is a bird and what is known about the
first “bird”, the transition from theropods to birds, and the origin of birds that link them to
the theropods. There is a paleontologist saying that we've come to agree with, “If it acts
like a bird, and has the structure like a bird, it must be a dinosaur.”
1. Feathered Dinosaurs
A. What do we know about the evolution of the feathered dinosaurs; what are some of
the discoveries of feathered dinosaurs and who discovered them? - Melinda, Niel?
Feathered dinosaurs –Niel
In the search for the connection between birds and dinosaurs, it is important to investigate
the dinosaurs that have been found with feathers. One of the great discoveries that has
linked dinosaurs to birds is the fact that in China a dromaeosaur was found that has
remiges. “Remiges are like the flight feathers of birds, with a central stiffening vein from
which branched fibres radiate”(Xing Xu). This discovery shows that not only were there
feathered dinosaurs, but some of them may have been capable of flight. In China, there
have been discoveries of at least two other dinosaurs that are thought to of had feathers,
Scansoriopteryx and Epidendrosaurus; these two are “the first undoubtedly arborial (tree-
climbing) dinosaurs” (Xing Xu). There is a lot that is not confirmed about these dinosaurs,
everything from the time they were alive to the possibility that they were not of the same
species. Oviraptorosaurs are thought to of had feathers because of how the bodies were
shaped (Xing Xu,). Nomingia, one type of Oviraptorosaur, has a short tail that is similar to
that of birds; the main similarity is the “pygostyle” (Xing Xu). This structure is used in
modern bird to turn the tail feathers because the pygostyle has this specific use some
scientists think that the Nomingia had feathers.
2. Origin of Feathers
B. What do we know about why feathered dinosaurs evolved the way they did, and what
are the ideas about the origin of feathers? -- Brian
It is safe to say that everyone that is able to see can tell you what the average bird looks
like. They have two wings, two feet, a beak, and lots of feathers. Though birds have a
specific type of skeletal structure, the one thing that makes them truly unique is their
feathers. No other creature currently living has feathers, making feathers an evolutionary
novelty. This novelty can be dated back to the Late Jurassic, but is hypothesized to be
older still - just no fossil or well enough preserved fossils exists currently to establish a
firm missing link in the transition from the reptilian scales that belong to the dinosaurs to
the feathers on the birds we know of today. Though we may not be able to date the time
frame that feathers first began developing we can track the evolutionary process of
feathers from fossils found in both Germany and China, where some of the oldest
specimens of fossilized feathers have been discovered.
The first theropod discovered with feathers, and also one of the most studied, is
Archaeopteryx from the Bavaria, who was fully covered in feathers. Since the time of this
discovery many others have been found, even some that are older. Though Archaeopteryx
is from the Late Jurassic much of the recent study has been from fossils found in the
Liaoning Province in northeast China. These records are primarily from the Early
Cretaceous (110-139.4 million years ago), where fossils of dinosaurs that are closely
related to birds and of real birds have been found. One of the unique features of fossils
from this area is that not only are the bones preserved but so too are feathers and other
soft parts.
The evolution of feathers was once though to of been a divergence from scales. This does
not seem likely as they are not directly homologous (made of the same base compounds).
Instead a five step process is currently the accepted evolutionary process that helped
develop the first feathers.
Graphic from Mark A. Norell and Xing Xu article “Feather Dinosaurs” found in the Annual Review of
Earth and Planetary Science; 2005; 33 Platinum Full text Periodicals pg. 277.
1. The process starts off with hollow tubes forming from follicles, or the adaption from
scales to having follicles.
2. The calamus (tubes) adapted into having a series of barbs (similar to the feathery part
of a feather) along them.
3. The barbs organized along a rachis (the central shaft of a feather that extends from the
calamus).
4. The development of barbules, which gives feathers the ability to self organize and
allows the barbs to adhere to one another.
5. Is the further development of general feathers into more specific feather, for example
the different flight feathers.
Though this process is the most accepted it is also hypothesized that the above process
was not quite this straight forward. Many other divergences could have taken place to
include regression to previous stages. With the fossil record still being incomplete it is
hard to be certain what the exact time scale of this progression would have been, and how
many other processes were tried by nature before true feathers were formed. It is also
uncertain how the initial formation of feathers led to the formation of more specialized
feather that in turn led to flight, or the other various special function that modern feather
cater to.
Current thoughts on why feathers evolved: Though none of the theories as to why the dinosaurs, particularly the theropods,
developed feathers can be proved at this time, they can prove to be an interesting topic
for discussion and thought.
1. The development of feathers was much like the development of hair in mammals;
it would help keep the dinosaurs warm.
2. Everything from the barbs to the feathers themselves were found attractive and
help the dinosaurs with them mate. This over the many generations would have
weeded out all of those without feathers in that species.
3. Some scientists have proposed the idea that feathers evolved to assist some of the
smaller theropods in catching insect prey.
4. Smaller theropods might of developed feathers to maintain body temperature,
since many types of them were believed to be miniaturizing.
5. Genetic mutations may have been the cause and not a natural process for the
original formation of feathers. This has been experimented with by introducing
an outside agent to get the scales on a birds feet be feathery. This is a valid
theory sense both dinosaurs and crocodilians are related.
Picture of Sinornithosaurus fossils.
Close up photo showing the barbules and calamus Sinornithosaurus.
Above graphics from Xing Xu, Zhong-he Zhou, and Richard O. Prum article “Branched integumental
structures in Sinornithosaurus and the origin of feathers” Found in “Nature, Vol 40, 8 March 2001.
3. Early Bird Extinction
C. Amanda
The question of early birds and there relation to dinosaurs and why birds are living today
and the dinosaurs are extinct is one of many debates. There is a lot of research and many
suggestions that focus on the different reasons why birds are not extinct and the dinosaurs
of 65 million years ago are. The extinction of dinosaurs was not a single catastrophic
event but a series of events. There are 335 known species of dinosaurs and no one species
lived longer than two million years. After each group of dinosaurs became extinct a new
group would arise. Sixty five million years ago, a new group did not replace the
dinosaurs from the Cretaceous. Some believe this to be the last of the dinosaurs but others
have found that they are not extinct, but are still alive today.
The theory that dinosaurs are not completely extinct is a very controversial issue. Many
believe that the last dinosaurs to die out 65 million years ago were in fact replaced by a
new group, birds. This theory has very strong support, but a frequently studied draw back
is; how come birds survived and the dinosaurs did not? There are two scenarios that
researchers have concocted. The first is that birds signify a branch of the dinosaur
ancestry that survived the extreme cretaceous extinction and evolved into the birds of
today. The second scenario could be that birds and dinosaurs had a common ancestor that
gave dominance to both groups, following the theory of natural selection. This second
idea continues to present that birds were never dinosaurs, yet are actually the closest
living species in relation to the dinosaurs.
4. Early Birds
A. What is a bird and what do we know about the "first bird"? – Carrie
Birds are warm-blooded vertebrates belonging to the class Aves. They possess feathers
and have modified forelimbs that form wings, although their wings are not always used
for flight. In addition to these and other skeletal features, ovulating female birds have
medullary bone. This specialized bone prevents severe calcium loss during egg formation
and has also been found in theropod dinosaurs. Birds lay hard-shelled amniotic eggs, and
have a hard bill that covers the jaw. They also have a four-chambered heart and a highly
efficient respiratory system.
Birds are thought to have evolved from the theropod dinosaurs. The ancestors of birds
were terrestrial, bipedal, carnivorous or omnivorous, and also possessed features
commonly thought of as belonging to birds, like a wishbone and feathers. They also
shared the elongated forelimb and lateral flexing wrist found in later birds, as well as
other features like hollow bones whose origins predated flight. The closest living
relatives to modern birds are Crocodilians, and the closest non-avian dinosaur relation is
thought to have been the Dromaeosaurs.
The oldest member of the class Aves, and earliest recognized bird, is Archaeopteryx.
Several well-preserved specimens from a variety of species of Archaeopteryx are known
from the Late Jurassic. Archaeopteryx was approximately the size of a medium-sized
modern bird, like a pigeon or dove. At the time that Archaeopteryx were alive, the sites
where they have been found were part of a marine lagoon. The lagoon was surrounded by
a series of low, subtropical and semi-arid islands that were probably shrub covered, but
do not show evidence of trees.
Archaeopteryx had several skull and skeletal features that link them to modern birds, but
it also retained many intermediate or theropod-like features. There is some controversy
over whether or not Archaeopteryx was in fact a flight-capable Dromaeosaur, but these
arguments have been refuted by the presence of derived characteristics that are shared
with birds.
Archaeopteryx feathers were asymmetrically vaned, indicating flight. Archaeopteryx
lacked the muscle attachments to have been a strong flier, but it is believed that they were
capable of down-stroke wing flapping and gliding. Due to the preservation conditions, it
is unclear whether or not the head and body were entirely covered by feathers or not, but
well-preserved wing and tail feathers have been found.
Its feet were not adapted for perching. Archaeopteryx possessed a short, hyper-extendable
toe two like its Dromaeosaur relations, but also had the reversed, or partially reversed,
toe one like modern perching birds. This most likely indicates that they were generalist,
capable of ground or arboreal movement.
Although it is not known whether Archaeopteryx is the direct ancestor of modern birds, it
is clear that birds, and flight, were evolving at this time. Typically avian foot features are
found in the fossil record shortly after Archaeopteryx, and characteristics of flight, such
as the wing, show rapid change whereas those of the skeleton and skull evolved more
slowly.
5. Evolution of birds and wings.
C. What do we know about why birds evolved the way they did, what are the ideas for
the origin of flight, how did the birds (avian dinosaurs) survive the big extinction while
the (non-avian) dinosaurs did not? -- Wendy
The earliest known fossil bird is Archaeopteryx which is from the late Jurassic period. It
had a flat sternum and teeth which separate it from modern birds. Like modern birds, it
had feathers, hollow bones, and reduced fingers. Birds are an extremely diverse species
and therefore it is important to trace the oldest ancestor to eliminate recent modifications
when trying to determine their development. The ability to fly allows birds to travel to
every part of the globe and allows for hummingbirds, ostridges and penguins in the same
species. Current research questions whether the Archaeopteryx was the earliest bird or a
cross between a dinosaur and a bird as it had dominant features of both. Another
possibility for the oldest bird ancestor is the gansus yumenensis which was recently
discovered in China. These were able to fly and swim and possessed feathers but lacked
hollow bones.
There are many theories about why wings and therefore flight developed. One of the
theories was that wings were developed as a defensive strategy to allow a quick escape
from predators or to free up the hind legs for use as a weapon. This could have resulted in
the development of wings to assist in leaping, and flying could have been a by product of
this. A second but equally likely theory was the need to reach food sources. This could
have involved reaching flying or speedy prey, or allowed them access to new and
untapped food sources, first with the aid of wings and then by flight.
A debate is ongoing concerning how flight began. It is between the theories of tree to tree
“gliding” flying as the first type of flight in the evolved dinosaurs/birds versus flight from
the ground up. Either one could have resulted in wings developing by gliding or leaping
ancestors flapping their wings to gain thrust. Recent research shows that the likelihood of
both theories is relevant, but neither can yet be proven definitively.
6. Transition from Feathered Dinos to Early Birds
A. How do we connect the "first bird" and the "early birds" to the feathered dinosaurs? --
Sabrina
Facts have proven that birds are the descendants of dinosaurs, but how exactly did this
happen and how are they linked? Let’s look at connections between the first bird and the
feathered dinosaurs.
The first non-avian feathered dinosaurs were found more than a hundred years after the
discovery of Archaeopetryx, in the early 1990’s. Most of the non-avian dinosaurs have
been discovered in China, but they have also been found in both eastern and western
regions of the United States, Europe, North Africa, Asia, South America, Antarctica and
Madagascar.
It has been suggested that although Archaeopteryx is believed to be the first bird, that it’s
species did not evolve and become the birds of today.
It is now felt that the Aves descended from Coelurosurian Theropods, specifically from a
clade called Maniraptora. This group is believed to have appeared in the late Jurassic,
and was only named just over 20 years ago, in 1986 by Jacques Gauthier.
It was in the 1960’s that scientist John Ostrum revived the idea of birds being
descendants of dinosaurs. Today we know that there are over 100 similarities between
birds and Theropod dinosaurs.
It is also believed that Dromaeosaurids and Troodontids form the clade
Deinonychosauria, whose members are the sister taxon to birds.
7. The Origin of Birds
B. What do we know about flying dinosaurs (birds) having evolved from a subgroup of
the carnivorous non-flying dinosaurs, the theropods -- Melissa
Archaeopteryx lithographica, by many is considered to be the first bird. Found in
southern Germany in Jurassic strata, its age is estimated to be about 150 million years
old. Paleontologists have long accepted that Archaeopteryx was a transitional form
between birds and reptiles. Some scientists believe that it resembles its ancestors, the
Maniraptora, more then its modern bird relatives.
Maniraptora are a group of theropod (bipedal) dinosaurs that many paleontologists
conclude is where birds first derived from during the Jurassic, about 150 mya.
Maniraptoran groups include but are not limited to; Aves (birds), Dromaeosaurs (raptor
