Mammal Skull Versus Reptile: What are the differences?

Author	Grade Level	Time Frame	Featured Picture
Becca Mussetter De Laveaga Elementary School Santa Cruz, CA	3rd Grade	Minimum three days with flexibility on amount of time per day.

DRIVING QUESTION

If you find a fossilized skull, what clues tell you if it is a mammal or reptile?

LEARNING GOALS

Learning goals are for students to collect, analyze and interpret data found in 3D printed fossil skulls. Students will be able to understand what type of information fossils can provide, including the environment where animals lived and the type of food they ate. In addition, they will have a better understanding of how much information can be found from past events regardless of size and or/time periods.

COLLABORATIONS

Students will be placed in groups of 4.  Each member of the group will have a job: illustrator, note-taker, measurement specialist, and findings reporter.  The illustrator will be responsible for drawing scientific illustrations of the skulls.  The note-taker will record observations by the group.  The measurement specialist will measure skulls and possibly skull parts.  The findings reporter will record the most important findings of the group to report out to the other scientists.

STEM INTEGRATION

Science: Students will be looking at fossils of mammals and reptiles.
Technology | Engineering: Student will be using 3D printed models, they will understand the printing process, and the meaning of “hands-on” and accessible.
Mathematics: Students will be using measurement tools for data collection.

ASSESSMENT

Students will be assessed throughout the activity based on their “job”.  In order to be effective, students must be engaged and active learners. The teacher can look at each student’s job to check for understanding along the way.  The final assessment will be the student’s creation of a fictional reptile or mammal skull.  The skull can be created from clay or illustrated. The model must state whether it is a reptile or mammal, and must have evidence of the differences.  For example, a reptile should have the cone shaped teeth and extra cavities seen in the fossil skulls. Students must also communicate to the class why they designed their fossilized skull the way that they did.  Using reasons and evidence gathered from the observation stage is critical.

The final assessment will be the student’s creation of a fictional reptile or mammal skull.  The skull can be created from clay (Crayola Model Magic works well) or an illustration. The model must state:

• Is the creation a reptile or mammal?
• What evidence do you have to support your identification?

For example, a reptile should have the cone shaped teeth and may even have the extra cavities seen in the 3D fossil skulls.  Students should be able to communicate to their class why they designed their fossilized skull the way that they did. Using reasons and evidence gathered from the observation stage is critical.

Students will be assessed throughout the activity based on their “job”.  In order to be effective, students must be engaged and active learners. The teacher can look at each student’s job to check for understanding along the way.  The final assessment will be the student’s creation of a fictional reptile or mammal skull.  The skull can be created from clay or illustrated. The model must state whether it is a reptile or mammal, and must have evidence of the differences.  For example, a reptile should have the cone shaped teeth and extra cavities seen in the fossil skulls. Students must also communicate to the class why they designed their fossilized skull the way that they did.  Using reasons and evidence gathered from the observation stage is critical.

ANCHORING EVENT & PROCEDURE

There are a number of skeletal differences between reptiles and mammals. For one, reptiles have a mouth filled with several teeth which are uniform in size and shape. By contrast, mammals tend to have teeth which vary greatly in size and shape. In reptiles, the lower jaw is comprised of several different bones. In mammals, however, the lower jaw is comprised of only one bone – the dentary. The classic reptilian skull also has a small hole, or “third eye” – a trait not found in mammals.

Have students work with a group of fossilized skulls (3D printed models).  Tell students that paleontologists found these skulls but lost the labels.  Tell them that some of them are reptiles and some are mammals.  Students will then work together to write down observable differences and similarities in the fossils. Their job is to figure out which are reptiles and which are mammals.

Third grade students would not be expected to know the specific reasons and differences among the skulls. However, a third grader can observe and record what they see.  They may not be able to identify all the differences but they will find key differences between the reptiles and mammals.  This is an important start to their growth as a young scientist.

DAY 1:
ENGAGE
Students will be placed in groups and with a set of fossilized skulls.  These skulls will be 3D printed models. Explain to student groups that the paleontologists who found these fossils, just sent some breaking news.  Half of the skulls were reptiles, and half were mammals.  The labels were lost and students need to work together to figure out which skull belongs to which group.

EXPLORE

Give students time to observe the teeth and skulls.  Students should be working on their assigned job:

• Scientific Illustrator- Will sketch a detailed picture of each specimen using pencil
• Note Taker- Will write down observations that group members make
• Measurement Specialist- Will be in charge of measuring the skull and/or teeth
• Findings Reporter- This student will report out the group’s findings

This activity should be a time when students can explore and are not worried about wrong answers.  They are working together, asking questions, and taking notes. Even though it is tempting, do not tell students which skulls are mammal or reptile.  Let them sort, process and think based on their own observations.

Every observation is welcome. Students should be given measuring tape and calipers so that they can make measurement comparisons among the skulls.

DAY 2:
EXPLAIN

Have students get into their groupings from Day 1.  Give students about 5 minutes to review what findings they are going to share with the class.  If students did not have enough time to finish their jobs, you can always give more time. 

The Findings Reporters will take turns reporting out to the “other scientists” what their group observed.  The teacher may want to chart similarities and differences between groups.   After the all groups have had a chance to share their observations, groups will go back and discuss possible reasons and explanations:

What differences were common?
Why do you think there were these differences?
What similarities were reported?
What might explain these similarities?
As a class, chart each skull and whether or not it was classified as a mammal or reptile. 

ELABORATE

After student groups have all had a chance to share their observations, groups will go back and discuss possible reasons and explanations.  What differences were common?  Why do you think there were differences?  What similarities were reported?  What might explain these similarities

DAY 3:
EVALUATE

STANDARDS

NEXT GENERATION SCIENCE STANDARDS (NGSS)

3-LS4-1 Biological Evolution: Unity and Diversity
Analyze and interpret data from fossils to provide evidence of the organisms and the environments in which they lived long ago.

COMMON CORE STATE STANDARDS (CCSS)

Solve problems involving measurement and estimation.
CCSS.Math.Content.3.MD.A.1

Represent and interpret data.
CCSS.Math.Content.3.MD.B.3

Conduct short research projects that build knowledge about a topic.
CCSS.ELA-Literacy.W.3.7

Recall information from experiences or gather information from print and digital sources; take brief notes on sources and sort evidence into provided categories.
CCSS.ELA-Literacy.W.3.8

ISTE: Creative Communicator
Students communicate clearly and express themselves creatively for a variety of purposes using the platforms, tools, styles, formats and digital media appropriate to their goals.

Knowledge Constructor
Students critically curate a variety of resources using digital tools to construct knowledge, produce creative artifacts and make meaningful learning experiences for themselves and others.

RESOURCES & MATERIALS

• Calipers and measuring tape
• Paper, notepads, pencils
• Poster board or chart paper
• Video | Skull detectives: Understanding Mammal Skulls
• 3D printed models

This is a great video to watch after the investigation.  It will pose questions and provide information for students to ask the next guiding questions, “How do we differentiate between mammal skulls?”

3D Printed Skulls

Half should be reptile and half mammal.
I recommend having enough for each group to have 4 skulls.
If this is not possible, groups can take turns visiting the skull station.

Suggested Skulls

Scientific Name	Common Name	Link to Database	Screen Shot
Hyaene hyaena	Hyaena	africanfossils.org/fauna/striped-hyaena?o=1
Colobus abyssinicus	White Colobus monkey	africanfossils.org/fauna/om-9008?o=1
Diceros bicornis	Black Rhinoceros (modern)	africanfossils.org/fauna/diceros-bicornis?o=1
Papio anubis	Olive baboon	africanfossils.org/fauna/papio-anubis?o=1
Crocodylus cataphractus	African Slender-snouted Crocodile	africanfossils.org/fauna/knmer-929?o=1
	Common caiman	thingiverse.com/thing:251979
Tyrannosaurus rex	T-rex	thingiverse.com/thing:308335
	Alligator Skull	thingiverse.com/thing:1350760
Pogona	Bearded dragon	thingiverse.com/thing:1087009
Cordylus namakuiyus	Kaokoveld Girdled Lizard	morphosource.org/Detail/SpecimenDetail/Show/specimen_id/4626
Sphenodon punctatus	Tuatara	morphosource.org/Detail/SpecimenDetail/Show/specimen_id/3383
Xenosaurus rectocollaris	Pallid knob-scaled lizard	morphosource.org/Detail/SpecimenDetail/Show/specimen_id/4893

Database Tips

africanfossils.org

This virtual lab showcases a spectacular collection of fossils and artifacts found mostly at Lake Turkana in East Africa. The digital collection of animals, human ancestors, as well as ancient stone tools offers a unique tool for scholars and enthusiasts to explore and interact with the collection online. It also provides an opportunity to download models for 3-D printing as well as to comment and share images of your favorite printed fossil objects on our forum. Once you create a username and password through africanfossils.org, you can download STL files.

thingiverse.com

Thingiverse is very user friendly.  Even though there many models that are not scientific or have been scanned from an actual specimen, the ease of printing makes it worthwhile to explore.

morphosource.org

Morphosource is an excellent site for fossils.  This site required one extra step.  The files are not STL, and most 3D printers will use STL files. Most of the files will be on PLY format, but there is an easy way to convert. 1) Download the open source software, MeshLab to convert the files to STL. 2) From MeshLab, import your PLY file, and then export as STL (Binary).

KEY ACADEMIC AND/OR SCIENTIFIC LANGUAGE

• Mammal: any of a class (Mammalia) of warm-blooded higher vertebrates (as placentals, marsupials, or monotremes ) that nourish their young with milk secreted by mammary glands, have the skin usually more or less covered with hair, and include humans.
• Reptile: a vertebrate animal of a class that includes snakes, lizards, crocodiles, turtles, and tortoises. They are distinguished by having a dry scaly skin and typically laying soft-shelled eggs on land.
• Fossil: mineralized or otherwise preserved remains or traces (such as footprints) or impressions of animals, plants, and other organisms. (from Wikipedia glossary); Evidence of past life on earth. Can include the preserved hard and soft parts of plants and animals, tracks and burrows, whole organisms preserved intact in amber or tar, and fossilized dung. Any evidence of life constitutes a fossil.
• Paleontologist: a scientist who studies fossils. If your basement is filled with fossils found while out on hikes, then you’re an amateur paleontologist. Paleontology breaks down to the Greek for “ancient” (paleo), “being” (onto-), and “study” (-logy).
• Caliper: an instrument for measuring external or internal dimensions, having two hinged legs resembling a pair of compasses and in-turned or out-turned points.
• Skull: framework of bone or cartilage enclosing the brain of a vertebrate; the skeleton of a person’s or animal’s head.
• Dentary bone: the mandible of a vertebrate, or homologous bone in the lower jaw of ancestral and related animals, which holds teeth.

PRIOR KNOWLEDGE

This lesson is meant to occur in the middle or end of the fossil unit. Students should already know what a fossil is.  Students should also be aware of what reptiles and mammals are. Understanding life cycles of different animals is part of the third-grade standards.