Chapter 3

LESSON 1 Evidence from the Fossil Record

Essential Question Pictures of the Past How are fossils used to learn about the history of To the untrained eye, fossils might look like ordinary rocks. But to a trained scientist, they are much more than that. They paint a picture life on Earth? of past organisms and environments that often look different from current organisms and environments. Warm Up When a Moroccan fossil collector showed scientist Nizar Ibrahim a box What clues about the of fossils, Ibrahim knew one of them was special. Years later he would past can you get from realize just how special it was. In 2014 the fossil collector led Ibrahim a fossil? and his team to the site where the fossil was found. It was in the middle of the Moroccan Sahara Desert. The team unearthed several more fossils. The fossils came from a dinosaur called Spinosaurus. They Vocabulary were about 100 million years old. biodiversity Spinosaurus was a large predatory dinosaur. The first Spinosaurus chordate fossils were discovered by Ernst Stromer in Egypt in 1912, but the fossils were destroyed during World War II. Since that time, Spinosaurus cyanobacteria had eluded scientists. microfossil Ibrahim and his team dug up many Spinosaurus bones. With the help paleontologist of Stromer’s original drawings, they used the bones to reconstruct the Spinosaurus skeleton. The skull was shaped like a crocodile’s, with sharp, cone-shaped teeth. Its back had a structure like a sail on top of it. Its hip bones were narrow. The bones in its feet were shaped like paddles. The scientists made an incredible conclusion: Spinosaurus could swim. This would be the first dinosaur known to live in water.

u In the paragraph above, underline the sentences giving evidence that Spinosaurus lived in water.

u Spinosaurus was an enormous predatory dinosaur. It lived in North Africa’s prehistoric rivers and swamps.

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Interpreting the Fossil Record MATERIALS Ask a question. What can you learn from fossils in rock layers? diagram of fossils in rock layers Use the diagram of fossils in rock layers found on page AP3 to complete the activity. The diagram shows fossils found in rock layers at a dig site.

1. Sequence Which fossils are oldest? Which are youngest? Put the fossil types in order.

Oldest Youngest

2. Analyze How has life at the dig site changed over time? How do you know?

3. Infer How might the environment have changed between layers B and D? Use fossil evidence from the diagram to support your answer.

Fossils Give Clues

Scientists like Nizar Ibrahim are paleontologists. A paleontologist is a scientist who studies fossils to learn what past organisms looked like and how they lived. Fossils also provide evidence about how living things and environments have changed.

When paleontologists find a fossil, they note the location of the fossil site. They may remove the fossil for further study. This requires slow and careful work. Paleontologists observe the rock layer in which a fossil occurs. They may record notes about it. They may record information about rock layers above or below the fossil, too. The location and layer of rock in which the fossil was found allow paleontologists to determine the age of the fossil.

u What tools might a paleontologist use to study fossils at a fossil site?

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Nizar Ibrahim

Nizar Ibrahim is a German/Moroccan paleontologist. He is best known for his discovery of a Spinosaurus skeleton in Morocco. Ibrahim has made other discoveries, too. He discovered a large flying dinosaur named Alanqa saharica. These dinosaur fossils are unlike any others in the world. Ibrahim has also discovered prehistoric fish, crocodile, and turtle fossils in the Moroccan Sahara Desert. The fossils give additional clues about the past environment. The area where Spinosaurus was found was once a tropical river ecosystem. Spinosaurus lived among several other large, meat-eating dinosaurs. Ibrahim’s discoveries help people understand the river ecosystem that occurred long ago in North Africa.

Ibrahim wants to document the biodiversity of African dinosaurs. Much of what people currently know about dinosaurs comes from fossil discoveries in Europe and North America. Those areas have been explored more extensively than Africa. By studying Mesozoic-era fossils in Africa, Ibrahim hopes to have a more accurate view of the fossil record.

In addition to studying dinosaurs, Ibrahim wants to improve scientific research. He wants to promote a better understanding of science in Morocco and around the world. He believes this can happen by inspiring the next generation of explorers and scientists. He creates museum exhibits using a variety of media to engage public interest in paleontology.

u What evidence suggests the Moroccan Sahara Desert was a river ecosystem during the Mesozoic era?

u How have Ibrahim’s discoveries changed ideas about dinosaur biodiversity during the Mesozoic era?

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