Article
T. Rex Illustration by Franco Tempesta; Shutterstock.com (All Other Images)

Will T. rex Have to Share the Crown?

Some researchers say there was more than one Tyrannosaurus species

By Susan Cosier
From the September 2022 Issue

Learning Objective: Students will round numbers related to T. rex fossils to the nearest 10 or 100.

Lexile: 1160L; 850L

Tyrannosaurus rex was believed to be the only dinosaur species of its kind. But recently, a group of scientists suggested that this dino (whose name means “tyrant lizard king”) was actually three separate species.

The scientists studied differences in the size and shape of fossilized T. rex bones and teeth. Their findings, the researchers say, suggest the animal we know as T. rex should include the original species plus two more—T. imperator, which means “emperor,” and T. regina, which means “queen.”

Tyrannosaurus rex was believed to be the only dinosaur species of its kind. Its name means “tyrant lizard king”! But recently, a group of scientists suggested that this dinosaur was actually three separate species.

The scientists studied differences in the size and shape of fossilized T. rex bones and teeth. The researchers think the animal we know as T. rex should include the original species plus two more. Those two other species would be T. imperator and T. regina. The word imperator means “emperor.” The word regina means “queen.”

These massive meat eaters lived between 90 million and 66 million years ago, toward the end of a period called the Cretaceous. “In principle, there is no reason to think that Tyrannosaurus didn’t go through a couple of species during the last few million years of the Cretaceous,” says Thomas Holtz. He’s a scientist at the University of Maryland who was not involved with the study.

Rethinking our understanding of T. rex might seem strange for some dino fans. But it’s normal for science to change. Triceratops and Brontosaurus, for example, have gone through  name changes. In fact, for much of human history, people didn’t realize that fossilized bones could be the remains of long-dead creatures!

These big meat eaters lived between 90 million and 66 million years ago. That was near the end of a period called the Cretaceous. “In principle, there is no reason to think that Tyrannosaurus didn’t go through a couple of species during the last few million years of the Cretaceous,” says Thomas Holtz. He’s a scientist at the University of Maryland. Holtz was not part of the study.

Thinking about T. rex as three different species might seem strange for some dinosaur fans. But it’s normal for science to change. Triceratops and Brontosaurus now have different names. For much of human history, people didn’t realize that fossils could be animal bones!

Still, the scientific study on the Tyrannosaurus species “is super controversial,” says the study’s lead author, Gregory Paul.

Until scientists gather more evidence, several experts, including Holtz, believe that T. rex should keep its throne to itself.

Still, the study “is super controversial,” says Gregory Paul. He’s the study’s lead author.

Until scientists find more evidence, Holtz and other experts believe that T. rex should keep its throne to itself.

Now You Try It

Use what you know about rounding to answer the questions below.

Use what you know about rounding to answer the questions below.

Paleontologists unearthedbones from the now-famous T. rex nicknamed Sue 32 years ago.

Round this number the nearest 10.

Paleontologists unearthedbones from the now-famous T. rex nicknamed Sue 32 years ago.

Round this number the nearest 10.

Grid showing the tens and the ones position of a number

Fossil hunters found the first T. rex skeleton 120 years ago.

Round this number to the nearest 100.

Fossil hunters found the first T. rex skeleton 120 years ago.

Round this number to the nearest 100.

Grid showing the tens and ones position of a number

A complete T. rex had 380 known bones. Sue’s partial skeleton has 250 bones, making it the most complete T. rex skeleton ever found. Write those numbers in the chart.

Round each number to the nearest 100.

A complete T. rex had 380 known bones. Sue’s partial skeleton has 250 bones, making it the most complete T. rex skeleton ever found. Write those numbers in the chart.

Round each number to the nearest 100.

A grid showing the hundreds, tens, and ones position regarding the complete T. Rex and Sue

T. rex had about 60 bone-crunching teeth. What’s the greatest number of teeth that would round to 60 when rounding to the nearest 10?

T. rex had about 60 bone-crunching teeth. What’s the greatest number of teeth that would round to 60 when rounding to the nearest 10?

video (2)
video (2)
Activities (8)
Answer Key (1)
video (2)
video (2)
Activities (8)
Answer Key (1)
Step-by-Step Lesson Plan

1. SPARK ENGAGEMENT.

Play the video "Dino Scientist." Then, before or after reading the article, spark a discussion based on the following questions.

  • How many different dinosaurs can you name? List a few features about each one.
  • When might a paleontologist need to use numbers that are not exact?

2. INTRODUCE THE MATH CONCEPT AND VOCABULARY.

  • Display a blank place value chart with hundreds, tens, and ones columns. Has anyone used a chart like this before? (Answers may vary.) This is a place value chart. It separates the digits of large numbers by their place value.
  • How could a place value chart help us in math? (Answers will vary. Possible answers: making sure you put your digits in the right place; writing a number in expanded form; determining the value of a digit)
  • Draw your own place value chart for the number 145. If you added a 0 to the end of this number, what number would you have? (1,450) How would your place value chart change? (You would need to add a thousands column and move each digit one place value to the left.)
  • Today we will use place value charts to help us round numbers to the nearest 10 or 100.
  • Play the math video "All About Rounding" and/or review the skills slide deck "Rounding Strategies."

3. WORK THROUGH THE "WHAT TO DO" BOX.

  • In which place values did the digits change when 107 was rounded to the nearest 10? (tens and ones places)
  • Why was 133 rounded down to 130? (The 3 in the ones place was less than 5, so it rounds down.)
  • What is another number that would round to 110? (105, 106, 108, 109, 111, 112, 113, or 114)
  • If you wanted to round these numbers to the nearest 100, which place value would you look at? (tens place)

4. REINFORCE WITH MATH PRACTICE.

Have students complete questions 1 through 4 on page 9.

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