Table of Contents
Volunteer Basics ................................................................................................................................1
Exhibition Overview ...........................................................................................................................4
Dinosaurs in the Exhibition.................................................................................................................6
Fossils and Fossilization.................................................................................................................... 26
Dinosaurs of San Diego County ......................................................................................................... 27
Categorization of Fossils ................................................................................................................... 29
Excavating a Fossil ........................................................................................................................... 31
Godwana ......................................................................................................................................... 32
Geologic Time Scale ......................................................................................................................... 35
Evolution ......................................................................................................................................... 38
Page 1
Volunteer Basics
The following information is just basic background on fossils and dinosaurs. Let the exhibition be your
main source of information. If you read every panel you will know more than any visitor. Enjoy!
The exhibition runs from Saturday, February 25 through Monday September 4, 2017.
Reporting for Service
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Please wear dark pants (jeans are okay), white shirt, your photo ID, and your “Ask Me” button.
After working three shifts, you’ll be eligible for a free Game of Bones t-shirt from the Museum
store and you can wear that for the remainder of the exhibition. If you wish to get something
else in the store that’s okay but it needs to be the same price as the t-shirt. Just go up to the
counter and say, “Janet said I could have this shirt after three shifts.”
Sign in the log at the north visitor desk and say hi to the VSAs.
Come to the volunteer room and leave your personal items in a locker. There are locks for your
use. The keys are located on the wall near the door. Take the key with you.
Please log your volunteer hours in Volgistics at the beginning of your shift. You may include
travel time to and from the Museum.
On your first day, plan on coming a little early or staying a little late so that you can thoroughly
explore the exhibition. This guide doesn’t cover everything that is in the exhibition.
Explore the rest of the museum so you are familiar with the exhibitions and where they are
located.
Scheduling
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You may add yourself to any opening in the Dinosaurs schedule on Volgistics.
Shifts are 10 AM–1 or 1–4 PM.
A weekly shift for a minimum of three months is the desired commitment.
Volunteer Roles in the Exhibition
There are many ways you can interact with the visitors. You may use the interpretative cart which is
filled with fossils and some fun dinosaur toys to attract the little ones. Or you can roam throughout the
exhibition assisting the little ones with the dinosaur search. Whatever makes you feel most comfortable
is fine.
Logistics for Interpretative Cart
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The cart will be stored in the hallway behind the Emergency Exit door between the two
restrooms in the exhibition hall.
Please use care when moving the cart.
Please station the cart inside the exhibition hall. The visitor service staff will be taking tickets in
the lobby area. We don’t want to interfere with ticket taking.
Unless you are relieved by another volunteer, please return the cart to the storage area.
Please be gentle with the objects and keep them in your control at all times. You can allow the
visitor to handle the objects but keep a watchful eye.
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Tips for Interacting with Guests
From the Science Museum of Minnesota
Greet and connect with our visitors
Say “hello” or “welcome” to visitors. Use open body language, smile and make eye contact. Look like
you are friendly and available to answer their questions or to work with them on some activity. Share
your enthusiasm for the museum.
Be a good listener
Be interested in what visitors tell you, and let their curiosity and responses drive the conversation
forward. Ask questions rather than lecturing with a lot of facts. You can help them reflect on their own
ideas and form their own opinions. If visitors aren’t interested in an extended conversation, that’s fine.
Use a variety of approaches
Work on learning how to talk to and work with visitors of all ages. Familiar examples can help explain
abstract concepts. Use vocabulary that is age appropriate and still scientifically accurate. To encourage
learning, have younger kids repeat back a word or phrase you taught them. Different styles of
interaction might be needed for small groups vs. large groups as well.
Ask questions
Try to use questions that have more than one answer. “What do you mean by that?” “Why do you think
that?” “How did you come to that conclusion?” “So let me see if I’ve got what you’re saying…” “
When you ask questions, let the visitor think for a few moments before you rephrase the question or
give the answer.
Offer positive and encouraging responses
With kids, recognize their answers, “You are right!” “Good thinking!” When visitors are having trouble
articulating their thoughts, you might say, “That’s an interesting idea. Why do you think that?” or “Have
you thought about…?” Offer them an opportunity to reflect further.
Share accurate information
You can offer additional information or a different perspective, but maintain a neutral position on
issues. If you aren’t sure about something, it’s OK to say, “I don’t know. That’s a great question!” Ask
other staff or volunteers if they know the answer.
Thank visitors
Wrap up the conversation whenever it has run its course. A brief interaction is fine! You can offer
suggestions of other exhibits in the museum that they might find interesting. “It was nice talking to you
today. Hope to see you again soon!” “Enjoy your museum visit.”
When using the interpretative cart
Be mindful of your set up. As volunteers, you may think you need lots of materials out for visitors to look
at or use; however, too many materials can be difficult to manage, which results in items breaking or
going missing. And visitors can be overwhelmed by a huge amount of materials and consequently, they
will be deterred from approaching you.
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Things to avoid
Do not share political or religious opinions. Fossils and what they tell us about evolution may generate
some controversy with a visitor. Explain to them we are a scientific institution and as such, teach
evolution. If a visitor is agitated or complains, please find the security officer in the exhibition. See
Museum’s position on evolution on page 38.
Other exhibitions
Give them clear directions when explaining where things are located in the Museum.
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Photo Ark (4th floor)
Extraordinary Ideas from Ordinary People: A History of Citizen Science (3rd floor)
Skulls (3rd floor)
Fossil Mysteries (2nd floor)
Coast to Cactus in Southern California (2nd floor)
Water: A California Story (1st floor)
Encourage them to visit other museums and gardens in Balboa Park.
Logging Your Volunteer Hours
Recording the number of hours you work as a volunteer is an important part of your service. These
volunteer hours play a critical role when the Museum applies for grants and submits proposals to
donors. Each year 750 volunteers contribute over 58,000 hours. The only way we can know how many
hours is by asking you to log them.
There is a computer in the volunteer room you can use each time you work your shift. If you forget to
log your hours, you can log them from home. Here are the instructions:
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Go to the Museum’s website www.sdnhm.org.
Choose the Join + Give Menu and click on Volunteer.
Click on the link that says “Already a Volunteer? Login here.”
Sign in using the email address you listed on your application. Your temporary password is
welcome. You will be asked to change it the first time you log in.
Choose Dinosaurs as your assignment.
You may include your travel time in your hours.
You may record your mileage for tax purposes (You may deduct mileage to and from your
volunteer work).
Adding Yourself to the Schedule
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Log into Volgistics as above.
Choose Check Your Schedule.
Choose show openings in Dinosaurs.
You may select any day with the Help Wanted sign.
Choose Schedule Me and then click continue to confirm.
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Exhibition Overview
Entrance / lobby: Welcome to Ultimate Dinosaurs
Fully-articulated Skeleton
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Cryolophosaurus (cast) [cry-o-LOAF-o-SOR-us]
Section 1: Triassic Period / 250-200 Million Years Ago
The Supercontinent of Pangaea and the Origin of Dinosaurs
Dinosaurs evolved during a time when the Earth’s land masses were grouped together as the equatorial
super-continent known as Pangaea. As a result, early dinosaur communities, dominated by coelophysoid
theropods and prosauropods, were widely distributed throughout the Triassic and the early Jurassic
periods.
The Ischigualasto Formation in Argentina contains some of the oldest known dinosaur remains and is
our best window into the origin of dinosaurs. This section of the exhibition features fossils of some of
these early dinosaurs, including the carnivores Eoraptor and Herrerasaurus, and the herbivore
Pisanosaurus.
Although dinosaurs first evolved in the Triassic, they were not the dominant land animals during this
period. A number of other large groups of vertebrate such as the rhynchosaurian, crocodilian, and
crurotarsan reptiles and the therapsid synapsids, were more numerous, and may have preyed upon
some of these early dinosaurs.
Fully-articulated Skeletons
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Eoraptor (cast) [ee-oh-RAP-tor]
Herrerasaurus (cast) [her-RARE-uh-SAWR-us]
Pisanosaurus (cast) [pye-SAN-uh-SAWR-us]
Supplementary Fossil and Cast List
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Lystrosaurus (cast; skull) [Liss-tro-sore-us]
Mesosaurus #1 (cast; stereosternum) [Mes-oh-sore-us]
Mesosaurus #2 (cast) [Mes-oh-sore-us]
Glossopteris #1 (cast) [glo-sop'te-ris]
Glossopteris #2 (cast) [glo-sop'te-ris]
Megatherium (original fossil) [Meg-ah-fee-ree-um]
Glyptodon (original fossil) [Glip-toe-don]
Section 2: Jurassic Period / 200-145 Million Years Ago
The Dinosaurs Take Over
Just before the beginning of the Jurassic Period, many animals that competed with the early dinosaurs
were wiped out, victims of a global, mass extinction event. This opened up new ecological opportunities
for the surviving dinosaurs, which expanded into new ecological roles and habitats across the globe.
New dinosaur groups evolved during this time, and by the late Jurassic, sauropods dominated the
landscape, replacing the earlier prosauropods as the major herbivores. Early theropods like
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Cryolophosaurus gave way to new groups of carnivores, including the tyrannosauroids, abelisaurs, and
allosauroids. Other new dinosaur groups that evolved during the Jurassic included the herbivorous
ornithopods and ceratopsians.
During the Jurassic, in the first stage of continental break-up, the supercontinent of Pangaea divided
near the equator to form a northern land mass (Laurasia) and a southern land mass (Gondwana).
Fully-articulated Skeletons
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Ouranosaurus (cast) [ooh-RAN-uh-SAWR-us]
Malawisaurus (cast) [ma-LAHW-wee-SAWR-us]
Suchomimus (cast) [Su-ko-mie-mus]
Supplementary Fossil and Cast List
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Nigersaurus (cast; skull) [Nee-jer-sore-us]
Carcharodontosaurus (cast; skull) [Car-kah-roe-don-to sore-us]
Hamadaosuchus (cast; skull) [Ham-odd-ow-soo-kus]
Elosuchus (cast; skull) [El-oh-soo-kus]
Aegisuchus (cast; skull) [Ay-je-soo-kus]
Onchopristis (original fossil) [On-cho-priss-tis]
Ceratodus (original fossil) [Seh-rah-toe-dus]
Lepidotes #1 (original fossil; skull) [Lep-ih-doe-teez]
Lepidotes #2 (original fossil; scale) [Lep-ih-doe-teez]
Suchomimus (tactile bronze cast; tooth) [Su-ko-mie-mus]
Suchomimus (tactile bronze cast; claw) [Su-ko-mie-mus]
Section 3: Cretaceous Period / 145-65 Million Years Ago
Gondwana Fragments
During the Cretaceous Period, the southern supercontinent of Gondwana began to fragment under the
unrelenting forces of plate tectonics, ultimately forming the present-day continents of South America,
Africa, Australia, and Antarctica—plus India and Madagascar. This section of the exhibition is organized
geographically into three major sub-sections, Africa, Madagascar, and South America, and profiles
Cretaceous southern dinosaurs whose fossil remains have been found on these landmasses.
Throughout the Cretaceous period, the global climate was relatively warm, sea levels were high, and
vast regions of the continents were covered by shallow seas. As the continental pieces of Gondwana
drifted apart, the isolation created distinctive ecosystems in which the respective dinosaur communities
evolved.
Fully-articulated Skeletons
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Majungasaurus (cast) [mah-JUNG-ah-tho-lus]
Masiakasaurus (cast) [Mah-shee-ah-kah-sore-us]
Rapetosaurus (cast) [Rah-pay-too-sore-us]
Simosuchus (cast) [Sim-o-su-kus]
Rahonavis (cast) [Rae-hoe-nay-viss]
Amargasaurus (cast) [A-mar-gah-sore-us]
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Buitreraptor (cast) [Bwee-tree-trap-tor]
Carnotaurus (cast) [Car-no-tore-us]
Austroraptor (cast) [Aw-stro-rap-tor]
Supplementary Fossil and Cast List
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Majungasaurus (tactile bronze cast; bones) [mah-JUNG-ah-tho-lus]
Majungasaurus (tactile bronze cast; teeth) [mah-JUNG-ah-tho-lus]
Spinosaur (original fossil; tooth) [Spine-oh-sore]
Sauropod (original fossil; tooth) [sawr-uh-pod]
Crocodilian (original fossil; osteoderm) [krok-uh-dil-ee-uh n]
Carcharodontodaurus (original fossil; tooth) [Car-kah-roe-don-to sore-us]
Sauropod (tactile original fossil; vertebra large) [sawr-uh-pod]
Sauropod (tactile original fossil; vertebra small) [sawr-uh-pod]
Theropod (tactile original fossil; partial tibia) [theer-uh-pod]
Argentinosaurus (cast; vertebrae) [AHR-gen-TEEN-uh-SAWR-us]
Futalognkosaurus (cast; leg) [Foo-tah-lonk-oh-sore-us]
Amargasaurus (model; embryo) [A-mar-gah-sore-us]
Amargasaurus (original fossil; femur) [A-mar-gah-sore-us]
Titanosaur (cast; femur) [Ty-tan-oh-sore-us]
Section 4: Late Cretaceous Period / 100-65 Million Years Ago
Southern and Northern Hemispheres
The final section of the exhibition will illustrate the difference between northern hemisphere and
southern hemisphere dinosaurs by presenting a dramatic hypothetical face-off between the megapredators Tyrannosaurus rex (from the north) and Giganotosaurus (from the south). During the Late
Cretaceous, the familiar tyrannosaurs were the dominant carnivores in North America, while the planteating hadrosaurs (duck-bills) and ceratopsians (horned dinosaurs) were the dominant herbivores.
This contrasts with the Gondwana fauna, where the dominant carnivores were Giganotosaurus and its
relatives and the sauropods (long extinct in the north) were the dominant plant-eaters.
Fully-articulated Skeletons
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Giganotosaurus (cast) [Gee-gah-note-oh-sore-us]
Supplementary Fossil and Cast List
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Giganotosaurus (tactile bonze cast, tooth) [Gee-gah-note-oh-sore-us]
Tyrannosaurus rex (tactile bronze cast, tooth) [tye-RAN-uh-SAWR-us]
Dinosaurs in the Exhibition
There are many full size replicas, in the exhibition. There are also many actual fossils. Anything that is in
a protected case is a fossil. Everything else is a replica.
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Giganotosaurus carolinii (Jig-uh-not-oh-sore-us)
Fully-articulated Skeleton
Giganotosaurus lived 99 million years ago in what is now Argentina during the Late Cretaceous period.
At over 43 feet long and weighing about 6-8 tons, Giganotosaurus was a theropod that rivaled even
T.rex in size. Indeed at the time of its discovery, it was famous for being “bigger than T.rex”, but both of
these theropods have since been surpassed in size by Spinosaurus. Giganotosaurus was a member of the
carcharodontosaurid family, which evolved out of the allosauroids. Allosaurs were one of the dominant
theropod groups throughout the globe back in the Jurassic period, but by the Cretaceous period, they
had largely been outcompeted by the tyrannosaurs. While the tyrannosaurs dominated in the Northern
Hemisphere during the Cretaceous, the carcharodontosaur and abelisaur families were left to dominate
the South where the tyrannosaurs could not reach. Giganotosaurus was the top predator of South
America during the Cretaceous (the similarly sized Carcharodontosaurus meanwhile, reigned supreme in
Africa), and it specialized in hunting similarly gigantic prey. It had thin, bladelike teeth for leaving deep
gashes and wounds in the flanks of large sauropod dinosaurs. This is in stark contrast to T.rex, which had
thick, banana-shaped teeth and bone crushing jaws for killing heavily armored herbivores.
Giganotosaurus has been hypothesized by some as a group hunter that worked together to bring down
large prey. This is based on fossil evidence of a related Argentinian theropod called Mapusaurus, which
has been found in groups of several individuals of various ages. Whether this is a sign of family groups,
or predatory attack mobs similar to those of modern Komodo Dragons is a topic of much debate.
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Tyrannosaurus rex (Tie-ran-oh-sore-us rex)
Fully-articulated Skeleton
T.rex lived 65 million years ago during the Late Cretaceous period. Once thought to be the largest of the
carnivorous dinosaurs, T.rex is actually dwarfed by several other carnivorous dinosaurs such as
Giganotosaurus and Spinosaurus. It is native to North America, unlike the rest of the animals in this
exhibition. T.rex grew to reach lengths of over 42 feet long and weighed up to 6 tons. Even more
impressive was its bite force, which was strong enough to crush the bones and armor of large herbivores
such as Triceratops and Ankylosaurus, which it specialized in hunting. Its teeth were thick and robust like
road spikes rather than the blade-like teeth of Giganotosaurus and Carcharodontosaurus, which
preferred to hunt the less heavily armored, but still massive, titanosaurs that were native to their
habitats.
Herrerasaurus ischigualastensis (Her-air-uh-sore-us)
Fully articulated Skeleton
This dinosaur was about 20 feet long and weighed about 770 pounds. Living about 230 million years ago
during the Late Triassic period in what is now Argentina, Herrerasaurus was one of the earliest
dinosaurs. In fact, it was so early in the evolutionary lineage of dinosaurs that scientists had trouble
classifying it for the longest time. Was it a theropod like Giganotosaurus and T.rex? Was it an early
ancestor of the long-necked sauropod dinosaurs? Was it primitive enough to be an ancestor to
both? Was it even a dinosaur at all!?! Thankfully, more complete fossils found in 1988 gave scientists
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more concrete evidence that it was indeed a theropod. No matter what it is though, Hererrasaurus is
important to our understanding of the beginnings of the dinosaur dynasty.
Cryolophosaurus ellioti (Cry-oh-loaf-oh-sore-us)
Fully-articulated Skeleton
Cryolophosaurus was 20 feet long and weighed about 1000 pounds. It was a theropod native to the Early
Jurassic period about 194-188 million years ago, and lived in what is now Antarctica. This is where
Cryolopohosaurus gets its name, which means “frozen crested lizard,” with its other namesake being the
trademark crest on its head. This same crest has lead scientists to nickname the creature “Elvisaurus,”
due to its crest resembling Elvis Presley’s pompadour hairstyle. The purpose of its unique crest may have
been strictly for mating displays, as a crest such as this would have been quite fragile. Even though it
lived in Antarctica, the name “frozen crested lizard” is a bit misleading. Antarctica was much closer to
the equator during the early Jurassic, and was a temperate forest rather than the frozen wasteland it is
today. Indeed, Antarctica was once rich with biodiversity, as Cryolophosaurus shared its habitat with the
prosauropod dinosaur Glacialisaurus, early pterosaurs, and many other creatures that wouldn’t dream
of inhabiting the frozen continent today.
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Austroraptor cabazai (Ah-stroh-rap-tor)
Fully-articulated Skeleton
Austroraptor was a dromaeosaur (what most people know simply as “raptors”) native to Late
Cretaceous Argentina, about 70 million years ago. At about 16 feet long and 660 pounds, Austroraptor
was one of the largest raptors, being rivaled in size only by Utahraptor from Utah, Achillobator from
Mongolia, and the recently discovered Dakotaraptor from South Dakota. Austroraptor is part of a
subfamily of dromaeosaurs that are exclusively found in the Southern Hemisphere called the
unenlagiines, which is a primitive dromaeosaur branch that became geographically isolated to the South
early in dromaeosaur evolution.
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Rahonavis ostromi (Rah-hoh-nay-vis)
Fully-articulated Skeleton
Rahonavis was native to Madagascar about 70 million years ago in the Late Cretaceous period. It was
once widely thought to be an unenlagiine dromaeosaur just like Austroraptor, but this consensus has
since been challenged. Many scientists now consider this diminutive dinosaur to now be closer to
modern birds than any of the extinct dinosaurs (but it is still technically a dinosaur either way, just as
modern birds are). Rahonavis had wing feathers, and may even have been capable of flight. Due to
having a skeletal structure still similar to other dromaeosaurs however, this flight would have been
clumsier and less graceful than that of modern birds. Rahonavis, whether it is closer to a raptor or a bird,
is an important link in the evolutionary chain between dinosaurs and birds.
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Carnotaurus sastrei (Car-no-tore-us):
Full articulated skeleton
Living approximately 70 million years ago in Late Cretaceous Argentina, Carnotaurus was a member of
the abelisaur family, which was a group found almost exclusively in the Southern Hemisphere and
included other genera such as Rugops of Africa, and Majungasaurus of Madagascar (which is also
present in this exhibit). Abelisaurs as a group were notorious for their short, compact skulls, and arms
that were so small that they made those of T.rex look impressive in comparison. Carnotaurus was 25-30
feet long and weighted about one and a half tons. Its name means “meat eating bull,” after the horns
protruding above its eyes. The purpose of these horns has been debated by scientists, because unlike
Cryolophosaurus, its headgear was more durable. The horns may have been used during conflicts
between rivals similar to modern rams, or even used as weapons to batter smaller prey with. Its strong
neck muscles would have allowed Carnotaurus to use its upper jaw like a hatchet and its horns as a
bludgeoning tool. Carnotaurus specialized in medium to small prey despite its large size, as it had a
relatively weak jaw but it was also extremely fast. Indeed, at estimated top speeds of up to 35 miles per
hour, Carnotaurus was one of the fastest of the large theropods, but it had lackluster directional control.
All of these predatory adaptations and drawbacks combined made Carnotaurus, more so than any
raptor dinosaur, the true cheetah of the Mesozoic era.
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Majungasaurus crenatissimus (Mah-jung-uh-sore-us)
Fully-articulated Skeleton
Like Carnotaurus, Majungasaurus was a member of the abelisaur family. Another similarity it has with
Carnotaurus is the presence of distinctive headgear, but in this case, it’s a single knob-like horn on top of
the skull rather than two horns above the eyes. It was 23 feet long and weighed over one and a half
tons. It lived in Madagascar during the Late Cretaceous period about 70 million years ago. It was a top
predator in Madagascar at the time, and would have preyed on sauropods such as Rapetosaurus (also
on display in this exhibit). Evidence suggests that it would have fed upon its own kind as well, as teeth
marks made by other Majungasaurus have been observed on the bones of this dinosaur. Even though
Majungasaurus looks nothing like a bird (unlike its contemporary Rahonavis), it too is an important case
study in the link between dinosaurs and birds. The vertebrae of Majungasaurus had spaces for air sacs
that helped improve respiration, which is a feature that would later be used by modern birds to help
them fly. Majungasaurus is proof that the entire theropod lineage, not just the small raptor-like ones,
had set the stage for bird evolution to take place.
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Masiakasaurus knopfleri (Mah-shee-ah-kah-sore-us)
Fully-articulated Skeleton
Definitely one of the more bizarre dinosaurs in this exhibit, Masiakasaurus was a theropod that was
about 6 feet long and lived 70 million years ago in Late Cretaceous Madagascar. Its most distinctive
feature was its downward curving jaw, which scientists have been debating over for a while now. Some
scientists believe that the long sharp teeth and downward curve of the bottom jaw allowed
Masiakasaurus to grasp fish. Other scientists cite the relative rarity of fish in the habitat of this strange
theropod, and believe that Masiakasaurus used its jaw to help it hunt burrowing animals instead. Even
more interesting about this dinosaur is its namesake. Masiakasaurus knopfleri means “Knopfler’s vicious
lizard,” as it was named after musician/composer Mark Knopfler, who composed music for various films
such as The Princess Bride.
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Amargasaurus cazaui (Uh-mar-ga-sore-us)
Fully-articulated Skeleton
Amargasaurus was a sauropod dinosaur that lived in Argentina during the Early Cretaceous period about
125 million years ago. It was not one of the larger sauropods, reaching a measly 30 feet long (measly
compared to giants like Brachiosaurus and Apatosaurus at least) and weighing in at just under 3 tons.
What sets Amargasaurus apart from other sauropods is not its size, but the distinctive vertebral spines
running along its neck. The function of these spines is still being debated to this day. Were they support
beams for a neck sail that was used primarily for display to mates and rivals? Were they lethal spines
used for defense against predators? Were they for something else entirely? Only time and more fossil
evidence can answer a question like this, and it’s just one of many examples of how fossils can often
raise more questions than answers.
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Malawisaurus dixeyi (Mah-la-wee-sore-us)
Fully-articulated Skeleton
Malawisaurus was named after the location of its discovery in Malawi, Africa. It was a 52 foot long
member of the titanosaur family of sauropods, and lived about 125 million years ago during the Early
Cretaceous period. Titanosaurs were a family of sauropods that were mainly known from the Southern
Hemisphere, with the exception of Alamosaurus, which lived in Texas. The titanosaurs were an
incredibly diverse group of sauropods that came in a wide range of sizes. So while Malawisaurus was no
slouch in the size department, it paled in comparison to other titanosaurs such as Argentinosaurus,
which could have exceeded 100 feet in length. Malawisaurus was most similar to its South American
counterpart Saltasaurus, since both were medium-sized titanosaurs that had dermal ossicles (a small
piece of calcified material) that would have adorned the skin on their backs. These dermal ossicles are
also found in the giant ground sloths that once lived here in California, and may have served as an extra
protective layer against predators.
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Rapetosaurus krausei (Rah-pete-oh-sore-us)
Fully-articulated Skeleton
At a maximum length of about 50 feet, Rapetosaurus, was one of the largest animals to have lived in
Madagascar 70 million years ago in the Late Cretaceous period. Its remains are based only on one
juvenile specimen that was about 25 feet long, but scientists have used its ontogeny to extrapolate the
species’ full size. It coexisted with other dinosaurs from Madagascar such as Masiakasaurus and
Majungasaurus, the latter animal being its most likely predator (hence the mount in this exhibit
depicting this probable hunting scenario).
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Buitreraptor gonzalezorum (Bwee-treh-rap-tor)
Fully-articulated Skeleton
One of the smaller dromaeosaurs, roughly the size of a rooster, this diminutive predator lived 94 million
years ago in what is now Argentina during the Late Cretaceous period. While it was most closely related
to Austroraptor and other Unenlagiine dromaeosaurs, Buitreraptor had an elongated snout that made it
resemble its more famous counterparts such as Velociraptor. Before the discovery of Buitreraptor,
scientists once thought that raptor dinosaurs were exclusive to the Northern Hemisphere. Now
scientists believe that dromaeosaurs first evolved in the Northern Hemisphere continents then migrated
down south just before the continents that once made up Pangaea started to break up even further.
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Simosuchus clarki (Sim-oh-soo-kus)
Fully-articulated Skeleton
Simosuchus was about 2 and a half feet long and lived about 70 million years ago in Late Cretaceous
Madagascar. This bizarre crocodylomorph’s name translates to “pug-nosed crocodile” due to its
unusually short snout. In fact, the short snout and leaf-shaped teeth within most likely meant that this
animal was an herbivore, which made it even more unusual amongst crocodylomorphs. To further
differentiate it from other crocs, its short, stiff tail also meant that it could not swim either. To
compensate for this lack of swimming ability, Simosuchus had more extensive armor than most crocs,
with armor plating even covering its legs.
19
Ouranosaurus nigeriensis (Ooh-rahn-oh-sore-us)
Fully-articulated Skeleton
Ouranosaurus was about 25 feet long and weighed about two and a half tons. It lived in Niger about 112
million years ago in the Early Cretaceous Period. Its name means “brave lizard,” and it’s an herbivore
related to Iguanodon and the duck-billed hadrosaurs. In fact, it even had the same thumb-spike
possessed by Iguanodon, which may have been used for defense. Its most distinctive feature is the
elongated neural spines that scientists are still debating over to this day. Is it a “sail” that was used for
thermoregulation, or a large hump like that of a camel or bison? It was a contemporary of Suchomimus
and Nigersaurus, both of which are also on display here.
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Suchomimus tenerensis (Soo-koh-mime-us)
Fully-articulated Skeleton
Suchomimus lived in Niger about 112 million years ago in the Early Cretaceous Period. It was about 36
feet long at full size, and could have weighed about 3–5 tons. Its name means “crocodile mimic” due to
its crocodile-like snout that was also present in other members of the Spinosaurid family. With relatively
short hind legs, hooked claws, and pointed, backward curving teeth, Suchomimus was thought to have
fed mainly on fish, which is also thought to have been a lifestyle shared by its larger and more famous
cousin Spinosaurus. In a hot, dry place like Africa, a diet of mainly fish sounds unfeasible, but back in the
Cretaceous, Niger was a lush, swampy habitat. This just goes to show how drastically environments can
change over the time.
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Eoraptor lunensis (Ee-oh-rap-tor)
Fully-articulated Skeleton
Eoraptor lived 230 million years ago in Argentina during the Late Triassic period. Its name means “dawn
thief,” and as that name implies, it was notable for being one of the earliest dinosaurs known. It was
only 3 feet long and weighed about 20 pounds. Don’t let the “raptor” part of the name fool you, as it
lived long before any of the dromaeosaurs had evolved. This small dinosaur had heterodont dentition
that implied an omnivorous diet. It was a contemporary of Herrerrasaurus and Pisanosaurus, which are
both also on display here.
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Pisanosaurus mertii (Pie-san-oh-sore-us)
Fully-articulated Skeleton
Pisanosaurus lived 230 million years ago in Argentina during the Late Triassic Period. This dinosaur was
also one of the oldest, and is thought by scientists to have been the first Ornithischian (bird-hipped)
dinosaur, meaning that it gave rise to various dinosaur groups such as the duck-billed hadrosaurs, the
horned ceratopsian dinosaurs, and the spiny stegosaurs among other groups. It was a small herbivore, at
just 3 feet long and weighing about 20 pounds. It may have been prey for the top predator at the time,
Hererrasaurus, which was fittingly enough, one of the earliest theropods. This relationship between
these two genera was the first iteration of an evolutionary arms race that would last for the next 160
million years until the end of the dinosaurs’ reign. Case in point, the descendants of Herrerrasaurus and
Pisanosaurus would later fight to the death in the form of Tyrannosaurus rex and Triceratops
respectively.
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Carcharodontosaurus saharicus (Car-car-oh-dont-oh-sore-us)
Fossil
Carcharodontosaurus was a cousin of Giganotosaurus that lived in Egypt up to 100 million years ago
during the Middle to Late Cretaceous period. Like its South American counterpart, it too was a
formidable apex predator at 45 feet long and weighing in at over 6 tons. Its name means “great white
shark toothed lizard” after the thin, blade-like teeth that it used to leave deep gashes and wounds in its
prey. Even though it was an apex predator, it shared its environment with at least two other large
theropods. The first of which, Spinosaurus, is the current record holder for largest carnivore ever to walk
the Earth, but its primary diet of fish prevented it from coming into conflict with the more terrestrial
Carcharodontosaurus too frequently. Deltadromeus was the other predator it coexisted with, but it was
slightly smaller. Like with Giganotosaurus, Carcharodontosaurus would have also specialized in hunting
truly immense titanosaur sauropods such as Paralititan, which were 65 ton fortresses of flesh.
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Argentinosaurus huinculensis (Are-jen-teen-oh-sore-us)
Cast Vertebra
Argentinosaurus lived about 97 million years ago during the Late Cretaceous period. This was a dinosaur
so big that it is only known from partial remains, such as the absolutely enormous backbone on display
here. Estimates currently place this gigantic herbivore at anywhere from 100–130 feet long, and
weighing it in at up to 100 tons. This makes Argentinosaurus one of the largest dinosaurs currently on
record, and quite possibly the largest land animal ever to exist. As its name implies, it lived in Argentina
about 95 million years ago during the Late Cretaceous period. This titan may have been prey for the
large theropod Mapusaurus, which was a cousin of Giganotosaurus and Carcharodontosaurus. Fossil
beds containing several differently aged specimens of Mapusaurus in close association have led
scientists to suggest that Mapusaurus and its cousins may have worked in groups to take down immense
sauropods such as Argentinosaurus. If this hypothesis is true, such a sight would have surely been a real
life giant monster battle worthy of a Godzilla film.
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Nigersaurus taqueti (Nee-zher-sore-us)
Cast of Skull
Nigersaurus was a bizarre sauropod dinosaur that lived up to 115 million years ago during the Early to
Late Cretaceous period. As its name implies, it lived in Niger, Africa, and it was up to 30 feet long and 4
tons in weight. Its most distinguishing feature was the shape of its mouth, which was broad and curved
downward. This was believed to have been an adaptation for low-level browsing, and this hypothesis is
supported by the fact that its horizontally oriented inner ear structure required it to keep its head
pointed down and closer to the ground. It coexisted with dinosaurs such as Suchomimus, and
Ouranosaurus, which are both on display here as well. Since grass did not evolve until later in the
Cretaceous, Nigersaurus would have most likely fed on low-lying ferns, horsetails, and flowering plants.
Fossils and Fossilization
Thomas Deméré, Ph. D., SDNHM Curator of Paleontology
What is a fossil?
Fossils are the remains and/or traces of prehistoric life. The critical factor is age. Fossils have to be older
than 10,000 years, the generally accepted temporal boundary marking the end of the last Pleistocene
glacial event. Fossil remains include bones, teeth, shells, and wood. Fossil traces include footprints,
burrows, impressions, molds, casts, and coprolites (a piece of fossilized dung).
How deep do you have to dig to find fossils?
Fossils are found in the sedimentary rock layers in which they were originally buried. So, the question
really is, where do these layers occur? The sea cliffs at Torrey Pines State Reserve provide excellent
exposures of 48–50 million year old fossil-bearing sedimentary rocks. The fossils in these rocks occur
right at the surface because erosion has done the "digging" for us.
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Where can I see fossils in San Diego County?
Since fossils occur in sedimentary rock layers, wherever sedimentary rocks are found there is a potential
for fossil discovery. As mentioned above, the sea cliffs at Torrey Pines State Reserve offer good
opportunities to observe fossils. These fossils generally consist of Eocene-aged (48–50 million years old)
shells of estuarine snails and oysters. Because the fossils are in a state reserve there is no collecting
allowed. However, this protection ensures that we and future generations will continue to be able to
discover and enjoy these paleontological remains.
Did dinosaurs ever live in San Diego County?
Yes. Dinosaur remains have been found in Cretaceous-aged (70–75 million years old) sedimentary rocks
as exposed at Sunset Cliffs, La Jolla Bay, and Carlsbad. The types of dinosaurs represented by these local
fossils include hadrosaur (duck-billed dinosaur) and nodosaur (armored dinosaur).
How do you know how old a particular fossil is?
The age of a fossil can be determined by several means. One method, called superposition, is based on
the position of a fossil in a stacked sequence of sedimentary rock layers. The fossils in the lowest layers
are older than the fossils in the upper layers. This method does not give an absolute age for the fossil,
only a relative age (older or younger). Absolute age of a fossil is determined by radiometric dating—a
method that relies on the natural radioactivity of certain elemental isotopes. Different isotopes have
different rates of radioactive decay and these rates are constant. This constancy of decay rates serves as
a "radiometric clock" that allows geochronologists to analyze samples and measure the relative
quantities (ratios) of "parent" to "daughter" isotopes. These ratios provide a means for determining
when the "radiometric clock" started and therefore the age of the rock layers associated with the fossil.
Dinosaurs of San Diego County
Thomas Deméré, Ph. D., SDNHM Curator of Paleontology
There are few reports of dinosaurs being found in our state and, surprisingly, five of those reports have
dealt with discoveries made here in San Diego County—one in La Jolla, one in Sunset Cliffs, and three in
Carlsbad. All of the San Diego dinosaur fossils have been found in sedimentary rocks of the Point Loma
Formation of late Cretaceous age, approximately 75 million years old. These rocks are generally equal in
age to the famous dinosaur-producing rocks of the Red Deer River region in southern Alberta, Canada.
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Hypothetical reconstruction of the Carlsbad nodosaur, by Brad Riney
Although many different species of dinosaurs have been found and described from the Red Deer River
region, only two kinds of dinosaurs are presently known from the San Diego area. These include an
indeterminate species of hadrosaur (duck-billed dinosaur), probably closely related to Lambeosaurus or
Saurolophus, and an indeterminate species of nodosaur (armored dinsoaur), probably closely related to
Panaplosaurus.
The first dinosaur find in San Diego County was made by Museum paleontologist Brad Riney, then a
junior high school student. This hadrosaur fossil material was an incomplete back vertebra from the sea
cliffs of La Jolla, found in 1967. Later hadrosaur discoveries include a femur collected in 1983 from a
Carlsbad construction site, a series of 13 tail vertebrae collected in 1986 from the Carlsbad Research
Center in Carlsbad, and a surf-worn fragment of a lower jaw collected in 1989 from the beach along
Sunset Cliffs.
The nodosaur fossil material was collected in 1987 and consists of a partial skeleton including pelvic
bones, back legs, incomplete front legs, ribs, dermal (formed in the skin) armor, and teeth. The Carlsbad
nodosaur probably approached 4 meters (13 feet) in length and in life was covered by a dense armor of
bone that actually formed in the skin. This dermal armor consisted of thick shoulder patches, low keeled
spinal plates, and an interlocking mosaic of polygonal pelvic ossicles. Nodosaurs were plant eaters
related to the familiar club-tailed ankylosaurs and distantly related to Stegosaurus, with its large dorsal
plates and tail spikes. The Carlsbad specimen is the first record of a nodosaur from California.
Geology is the primary reason that dinosaurs are so rare in our state. Here in California, the sedimentary
rocks of the correct age to contain dinosaurs were almost all deposited in the sea, and not on land. Since
dinosaurs did not live in the ocean (the large marine reptiles of the Mesozoic were not dinosaurs, but
were very different types of reptiles that included pleisosaurs, ichthyosaurs, and mosasaurs), their
remains are not typically preserved there. Fortunately, however, the occasional carcass would get
carried into the sea, probably as the result of an accidental drowning in a storm-swollen stream or river
that flowed into the ocean. Similar events have been observed today in the African wilderness where
herds of migrating wildebeest leave numerous bloated carcasses floating downstream after a major
river crossing.
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Categorization of Fossils
From the Science Museum of Minnesota
Paleontologists categorize fossils based on the manner in which they were preserved. Categories of
fossils include: fossils of whole or parts of an animal, trace fossils that show an animal was there, and
chemical fossils where minerals replace the biological parts of a plant or animal.
Actual, Original Remains: Body Fossils
Complete preservation of an entire organism is very rare, but it can happen. For example, some “Ice
Age” mammals, such as mammoths, have been found frozen in ice. No animals older than these are
found preserved this way, since temperatures have changed so much over geologic time. Small
creatures, like insects, or plant remains, may become trapped in tree resin that then hardens to form
amber. In regions where tar has seeped to the surface of the earth (such as the La Brea Tar Pits in Los
Angeles), the bones of animals trapped in the tar have been remarkably well preserved. In Alberta
Canada, a mummified Edmontosaurus (a duck-billed dinosaur) was discovered and reported in
December 2013. This discovery showed preserved impressions of soft tissue and provided the first
evidence the scaly animal had a fleshy head ornaments—kind of like a rooster’s comb.
Replacement or Permineralization
Often times, the remains of organisms are "petrified," or become like stone. (Petrified means “turned to
stone.”) This occurs when ground water, containing minerals, seeps into the pores of the wood or bone.
This can happen to various degrees. Sometimes, with bones, the original mineral content of the bone
(hydroxyapatite) remains, and only the organic parts (collagen and water) are replaced. In petrified
wood or plants, the organic material is replaced by silica. Petrified wood typically forms when silica-rich
ash from a volcanic eruption rapidly buries a forest. Pyrite (iron sulfide) is another mineral that replaces
organic material; such fossils are referred to as “pyritized.” Color varies on fossils too. Fossil shark teeth
found on the Atlantic Ocean are black; they have absorbed minerals from the area soils. In contrast,
fossil shark teeth from Morocco are tan/brown in color. Un-fossilized shark teeth are white or creamcolored.
Carbonization
In very fine-grained rocks, the liquid or gaseous components of the organic material may be driven off,
leaving a thin film of carbon that gives a delicate representation of the original organism. Carbonized
fossils often reveal fine details, or even the soft parts of animals, as with the fossil fish from Green River,
Wyoming, the animals preserved in the Burgess Shale or the feathers preserved in fossils like
Archaeopteryx.
Trace Fossils: Natural Molds and Casts
A shell or other hard part of an organism that has been buried in sediments, may be later dissolved by
percolating water, leaving behind a mold or space in the rock bearing an impression of the organism.
Later filling of the cavity by other sediments or minerals forms a cast. You can imagine the mold itself as
a "jello" mold, and the cast as the "jello" itself. Trace fossils include footprints, burrows and coprolites.
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What Conditions Favor Fossilization?
Not every creature that dies becomes a fossil. In fact, it is a rare exception; scientists estimate that far
less than 0.1 percent of the earth's former inhabitants are preserved at all. After death, most animals
are either scavenged by other animals or are decomposed by bacteria and other microorganisms.
Exposed remains are also subjected to the weathering elements of temperature, wind and water. Many
factors play a role in determining whether an organism becomes a fossil. Listed below are factors
favoring fossil preservation.
Taphonomy is the study of decaying organisms (plants and animals) and how they become part of the
fossil record.
Rapid Burial
If an organism is buried soon after death, it might avoid the effects of scavengers and decay and become
a fossil. How quickly something becomes buried depends on location. Animals that live in or near water
are much more likely to be preserved because sediments settle through the water and bury them. A
land animal might become trapped in muddy or swampy sediments or be buried in volcanic ash.
Organisms preserved in volcanic ash often retain exceptional details.
Dying in a place devoid of oxygen.
An organism cannot fossilize unless it is buried. Left on the surface with plenty of oxygen, an organism’s
body will decompose. Organisms are best preserved in anoxic (oxygen deprived) conditions, for example
in waters with poor circulation, the deep ocean, stagnant lake bottoms or bogs. The lower oxygen level
slows decay. Burial is faster under the sea than on land too.
Having Hard Parts
Preservation is much more common if the creature has “hard parts” like bones, teeth or a shell since
these parts can endure the elements longer for fossilization to occur. Soft parts, on the other hand, can
decay, be eaten by scavengers, get crushed during compaction, or dissolve by chemical reactions. Hard
parts too can be crushed. Today, about 30% of animals have “hard parts,” and these animals are
represented in the fossil record far more than animals like insects and jellyfish that lack bones or teeth.
Only in unusual circumstances are soft-bodied animals preserved. Graham Young, who has studied fossil
jellyfish around the world notes, their fossilization is a rare thing. “There is simply too much scavenging,
burrowing, and wave and current energy, for delicate carcasses to be preserved. Preservation is more
likely in muddy tidal flats or lagoons.” Young further notes, “One of the issues with soft body
preservation is that we are dealing with the dead remains of creatures that have been through the
taphonomic mill, subject to physical processes and to some subset of the fabulous range of microbial
putrefaction and fermentation.” (Young, “Recognizing Fossil Jellyfish” and “What You See is What You
Get. Sometimes.”) Science Museum of Minnesota, February 2014 13
Kristi Curry Rogers, a paleontologist at Macalester College in St. Paul, Minnesota notes, “The key to
getting fossilized is getting buried before surface processes (like scavenging, weathering, etc.) can
destroy your remains. In Madagascar, there was a lot of death (which can overwhelm scavengers so that
they might miss parts of your body), and there were seasonal rains that mobilized sediment that quickly
buried the dead so that they were effectively removed from any additional degradation. That plus there
has been very little tectonic activity in Madagascar, so the bones were never deeply buried, heated up
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or subjected to any subsequent to any subsequent post-burial vagaries.” (Personal email, December 15,
2013)
What Other Information Can We Learn by “Reading” Evidence in Rocks and Fossils?
Fossils Found in Association
A fossil snail shell alone cannot necessarily tell you if the snail lived in soil, fresh water, or in the ocean.
But if you find it in rock alongside fossils of bivalves, coral, and fish, it is safe to assume you have found a
marine (ocean-dwelling) snail.
Sedimentary Structures
Rocks with ripple marks or mud cracks are "non-fossils" formed by natural processes; these can also
provide clues about the ancient environment. For lithified ripple marks, the size, shape, and direction of
the ripples can indicate the velocity of the water as well as the direction the water was flowing. Mud
cracks preserved in a rock indicate that the sediments were exposed to wet and dry conditions.
Trace Fossils
Trace fossils (also called ichnofossils) are features such as burrows, foot prints, tracks or coprolites
(fossil feces) created by ancient life; but they are not the remains of the organism itself. They record an
animal’s movement or feeding, and they are useful in interpreting paleo-environments. An ichnologists
is one who specializes in trace fossils; they have named and classified many types of trace fossils and the
associated ancient environments.
Animals burrowing in the muddy sea floor often form narrow, elongated passageways, and sometimes it
is possible to tell what animals made them. If burrow-like marks in the rock taper to a point or branch,
they may be the traces of roots, and the rock was probably an ancient soil.
Excavating a Fossil
Whale Fossil found in Chula Vista
Thomas Deméré, Ph. D., SDNHM Curator of Paleontology
On 30 March 1998, paleontologists from the San Diego Natural History Museum excavated the partial
skull of a fossil baleen whale (Cetacea: Mysticeti) from ancient marine sandstones in southwestern San
Diego County, California. The sandstone layer that contained the fossil is part of the San Diego
Formation, a sedimentary rock unit that was deposited in this area during the latter part of the Pliocene
Epoch, approximately 2 to 3 million years ago.
The fossil specimen was unearthed by grading equipment at the Otay Ranch, Village 1 residential
development site in eastern Chula Vista, California. Paleontologists Richard Cerutti, John Pfanner, and
Pat Sena discovered the partial skull as they were following in the wake of a bulldozer. When the
bulldozer struck the buried fossil, the top of the braincase was removed. It was the smear of fossil bone
that attracted the attention of the paleontologists. Initial examination of the half buried skull revealed
that it was generally intact and worth collecting.
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Collection of the specimen followed conventional field methods
for large fossil vertebrates. The skull was first assessed as to the
degree of damage. Broken or weakened pieces of bone were
stabilized using special hardeners (e.g., glyptal or cyanoacrylate
glue). The perimeter of the specimen was then defined by
probing around it using hand tools (dull kitchen knives, putty
knives, and ice picks). Initial excavation was then begun around
the perimeter using picks and shovels. When the excavation
reached the point where the specimen was isolated in a matrixsupported pedestal from the rest of the outcrop, the pedestal
was then slightly undercut at its base to form an overhanging lip.
Damp newsprint was then placed on the upper surface of the
block. A solution of 20 minute Plaster-of-Paris was then mixed
and 5-10 inch-wide strips of burlap cloth soaked in the solution.
The strips were then lifted out of the plaster solution and laid
across the block to dry.
Because of the size of the specimen, three layers of plaster-soaked burlap "bandages" were formed on
the block. During the plaster work this jacket was also reinforced with metal stakes. Once the plaster
hardened, the remainder of the supporting pedestal was undercut and the plaster jacket turned over.
Hand digging tools were then used to remove any excess matrix from the bottom (now top) of the block.
When all layers of plaster were completely hardened the completed plaster jacket was then labeled with
a field number and north arrow, removed from the field, and transported to the Museum.
Once the plaster-jacketed specimen was in the Museum the next step was to expose the fossil by
removing as much of the enclosing sandstone matrix as possible. Fortunately, the sandstone that the
specimen was buried in is a damp, friable sand that is very easy to dig. As the matrix is removed from
the fossil we are discovering that the bone is quite brittle in places. These areas are cleaned as much as
possible with small knives and paint brushes and then hardened with cyanoacrylate glue. So far we have
uncovered the base of the braincase and exposed the glenoid fossae (where the lower jaws articulate
with the skull), the occipital condyles (where the atlas vertebra articulates with the skull), the external
ear canals, and the middle ear bones. The specimen is upside-down in the plaster jacket, which means
that it was right-side-up when we found it in the field and that 3 million years ago it was laying rightside-up on the sea floor while it was being buried by sand.
Godwana
Science Museum of Minnesota
Gondwana is an assemblage of the modern-day southern hemisphere landmasses: South America,
Africa, Madagascar, India, Antarctica, and Australia. The original landmass of Gondwana, a southern
supercontinent, formed during the Precambrian and broke up during the Mesozoic. The continents
share common features: fossils and stratigraphy; and during the early 20th century, geologists
recognized that the continents fit together like one big jigsaw puzzle. But it wasn’t until after World War
II when oceanographers mapping the oceans discovered new oceanic lithosphere (the relatively nonrigid 100-150 km think layer of the earth constituting of the crust and the top part of the mantle) in the
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middle of the ocean. This discovery led to the theory of “continental drift,” now called “plate tectonics.”
(the continents don’t “drift”). This theory helped scientists explain the distribution of contemporary life
as well as plant and animal fossils found on distant continents.
http://www.cms.fu-berlin.de/geo/fb/elearning/geolearning/en/gondwana/introduction/index.html
http://pubs.usgs.gov/gip/dynamic/historical.html
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Breakup of the supercontinent Pangaea, a prominent figure in the theory of continental drift, the
forerunner to the theory of plate tectonics. http://pubs.usgs.gov/gip/dynamic/historical.html
Key events in the timeline for the breakup of Gondwana
225–250 million years ago: The one giant landmass of Pangaea existed
200 million years ago: Pangaea starts to break apart forming Gondwana in the southern hemisphere and
Laurasia in the northern hemisphere
150 million years ago: Gondwana continue to split from Laurasia
125 million years ago: India completely separated from Antarctica
115 million years ago: Madagascar and India broke off from Africa
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100 million years ago: New Zealand separated
88 million years ago: India broke off from Madagascar
65 million years ago: Asteroid strikes the Yucatan and causes global extinction
50 million years ago: India collides with Asia
45 million years ago: Australia completely separated from Antarctica
25 million years ago: Drake Passage opens Science Museum of Minnesota, February 2014 57
Gondwana Stratigraphy
If one examines the stratigraphy (the sequences of rock layers) of South America, Africa, India and
Australia, some similarity appears. Alfred Wegener, who in 1912 proposed the theory of continental
drift, showed that three rock layers appeared on each of the continents (see diagram below). Geologists
have found Glossopteris fossils, an extinct fern
dating back to the Permian (290- 248 Ma) in the
middle layer composed of coal beds, shale and
sandstone and in the layer with glacial debris. The
top layer is composed of basaltic lava flows. These
similar rock layers, now separated by great
distances on different landmasses lent credibility to
Wegener’s ideas of continental drift. In addition,
the abundance of the Glossopteris fossils across the
southern continents indicates they were a
dominant feature of the Gondwana landscape. This
fossil was found among the remains of Antarctic
explorer Robert Scott after his ill-fated British Terra
Nova expedition 1910-1913.
Simplified stratigraphic profile for portions of South America, Antarctica, Australia, Africa and India
(Courtesy of USGS)
Geologic Time Scale
Dividing Earth History into Time Intervals
Geologists have divided Earth's history into a series of time intervals. These time intervals are not equal
in length like the hours in a day. Instead the time intervals are variable in length. This is because geologic
time is divided using significant events in the history of the Earth.
Examples of Boundary "Events"
For example, the boundary between the Permian and Triassic is marked by a global extinction in which a
large percentage of Earth's plant and animal species were eliminated. Another example is the boundary
between the Precambrian and the Paleozoic which is marked by the first appearance of animals with
hard parts.
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Eons
Eons are the largest intervals of geologic time and are hundreds of millions of years in duration. In the
time scale above you can see the Phanerozoic Eon is the most recent eon and began more than 500
million years ago.
Eras
Eons are divided into smaller time intervals known as eras. In the time scale above you can see that the
Phanerozoic is divided into three eras: Cenozoic, Mesozoic and Paleozoic. Very significant events in
Earth's history are used to determine the boundaries of the eras.
Periods
Eras are subdivided into periods. The events that bound the periods are wide-spread in their extent but
are not as significant as those which bound the eras. In the time scale above you can see that the
Paleozoic is subdivided into the Permian, Pennsylvanian, Mississippian, Devonian, Silurian, Ordovician
and Cambrian periods.
Epochs
Finer subdivisions of time are possible and the periods of the Cenozoic are frequently subdivided into
epochs. Subdivision of periods into epochs can be done only for the most recent portion of the geologic
time scale. This is because older rocks have been buried deeply, intensely deformed and severely
modified by long-term earth processes. As a result, the history contained within these rocks cannot be
as clearly interpreted.
http://geology.com/time.htm Contributor: Hobart King
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https://geomaps.wr.usgs.gov/parks/gtime/
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Evolution
The theory of evolution is central to the discussion of dinosaurs especially since we still have dinosaurs
today—birds. They are one of the branches of the tree in the evolution of dinosaurs. Below is the
Museum’s statement on teaching evolution. Let this be your guide when a visitor wishes to engage in a
conversation about evolution. Especially pay attention to the last paragraph concerning intelligent
design.
A Scientific Approach to Teaching Evolution
Approved by the San Diego Society of Natural History Board of Trustees
September 1, 2005
The purpose of this Statement is so that representatives of the Museum can represent the institution
with one voice. However, anyone that is asked a question they are not comfortable answering is invited
to forward the inquirer to Senior Director of Communications Rebecca Handelsman or their supervisor
or department head.
Helpful evolution links: Understanding Evolution, UC Museum of Paleontology and National Center for
Science Education, and Evolution, PBS.
Modern science is constructed under the assumption that natural phenomena are the result of natural
causes, and that any scientific hypothesis on the natural world can be put to a test through systematic
observation or experimentation. The scientific process is based on observable physical evidence, which
is used to test hypotheses. Scientists use tangible facts and replicable experiments to lead us to a better
understanding of how the natural world functions.
The Theory of Evolution plays a fundamental role in our understanding of modern biology. Evolution is
not a hypothetical, unproven fact (as the term "theory" is sometimes used outside the realm of scientific
research), but rather a robust body of knowledge, compiled and tested over the past 250 years, that
serves as the best explanation for the diversity of life we see around us. Like many other scientific
theories (gravity, light or continental drift), it is a coherent set of concepts that can explain and predict
the way nature works on issues as important as the way we feed ourselves, treat our diseases, or take
care of our environment.
A scientific theory has to meet certain criteria: it must be based on the most simple hypotheses; it has to
be based on replicable facts; it has to be testable, and it cannot contradict itself. The Theory of Evolution
meets these criteria; it is a true and valid scientific theory. In contrast, the concept of intelligent design
does not fit these criteria: It assumes the intervention of an un-testable supernatural force, and,
because it is based on an external assumption (the intentional action of an intelligent designer), it is not
based on replicable facts and observations, and hence its tenets cannot be put to a test. The concept of
intelligent design does not deal with the proximate causes of science, but rather with the ultimate
meaning of existence—an issue of faith.
Just as most scientists do not (and should not) interfere with other persons' spiritual beliefs, scientific
research cannot (and should not) be ruled by religious beliefs. Promoting spiritual teachings as a
respected scientific theory would imply a serious breach in the boundary between individual religious
spirituality (the subjective exploration of the inner spirit and the ultimate meaning of existence) and the
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collective construction of knowledge (the systematic and objective scientific exploration of the natural
world).
The quandary of an intelligent designer should be treated as a spiritual and religious question; a
legitimate and fundamental question for most persons, but definitely not a scientific one.
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