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The Permian Period
How did some reptiles start developing features that would one day lead to mammals?

Meet the Permian Period! This was a time long before dinosaurs when the world was home to a wild variety of animals, both with backbones and without. This lesson helps your learner understand one of the most important ways scientists organize life: whether an animal has a backbone or not. It's a foundational concept that will help them see how all living things are connected and classified.

S2S_Lesson18 by Selene

Key Ideas

  • The Permian Period lasted from about 299 to 252 million years ago.
  • Scientists classify animals by shared physical traits.
  • Vertebrates have internal skeletons that support body weight and movement. Invertebrates lack backbones and rely on other structures for support.
  • During the Permian, both vertebrates and invertebrates filled important ecological roles.
  • Body structure influenced how animals moved, fed, and survived in Permian environments.

Spines
  • DK's Science as You've Never Seen it Before:
✏️  Notebooking Activity
Make a list of vertebrates and invertebrates from this period. For each type of organism, think about why their body structure helps them.

Cosmic CalendarWhere we are: December 23
We reach December 23rd, eight days from the end of the calendar. Read the script below before the lesson.

Read aloud: December 23rd on our Cosmic Calendar. The Permian Period, roughly 299 to 252 million years ago. Reptiles are diversifying and spreading across the land. And among them are a group called synapsids, sometimes called mammal-like reptiles, that are the distant ancestors of every mammal alive today, including us. We are eight days from the end of the calendar. The dinosaurs haven’t appeared yet. Mammals haven’t appeared yet. Humans are still a tiny blip in the very last moments of December 31st. But right now, on December 23rd, the animals that will eventually become mammals are already out there, surviving, evolving, waiting for their moment. That moment is almost here.

Timeline EntriesLabel the next page in your timeline “Reptiles & Mammal-Like Creatures: 320 Million Years Ago”. The workbook prompt asks learners to draw a sail-backed Dimetrodon basking in the Permian sun.

Discussion Questions
  1. What is a backbone? 
    Sample answer: A structure inside the body that helps support it.
  2. What is a vertebrate? 
    Sample answer: An animal with a backbone.
  3. Why do scientists group animals by body traits? 
    Sample answer: To understand how animals are alike and different.
  4. Why is having a backbone helpful for animals living on land? 
    Sample answer: It helps support body weight and allows stronger movement.
Digging Deeper
  • How can studying Permian animals help scientists understand life today? 
    Sample answer: It shows how body plans evolved and persisted over time.

Vocabulary
  • Synapsid — A group of vertebrates (including early mammal-like reptiles and eventually mammals) with a specific skull opening behind the eye.
  • Therapsid — Advanced mammal-like reptiles of the Permian and Triassic periods; direct ancestors of mammals.
  • Scales — Thin, overlapping plates covering the skin of reptiles, providing protection and waterproofing.
  • Warm-Blooded — Describes animals that regulate their own body temperature internally, regardless of the outside environment.
  • Cold-Blooded — Describes animals that rely on external heat sources to regulate body temperature; most reptiles are cold-blooded.
  • Permian — The final period of the Paleozoic Era (about 299-252 million years ago), ending in the worst mass extinction in history.
  • Fossil Record — The collection of all known fossils and their placement in rock layers, used to trace the history of life on Earth.

Species to ResearchThe Permian saw reptiles and mammal-like creatures dominate the land. Here are some species to research:
  • Dimetrodon — A sail-backed synapsid often mistaken for a dinosaur; actually more closely related to mammals than to reptiles.
  • Edaphosaurus— Another sail-backed herbivore from the Permian; the sail may have helped regulate body temperature.
  • Gorgonops— A large, saber-toothed therapsid; one of the top predators of the late Permian.
  • Lystrosaurus— A barrel-bodied therapsid herbivore; survived the Great Dying and dominated early Triassic landscapes worldwide.
  • Moschops— A large, thick-skulled Permian herbivore; related to the lineage that would eventually lead to mammals.

SCIENTIST SPOTLIGHT: Alejandro OteroAlejandro Otero is an Argentine paleontologist who studies the evolution of early reptiles and the ancestors of mammals, called therapsids, in South America. His work is part of a broader shift in paleontology toward recognizing that some of the most important evolutionary transitions happened in the Southern Hemisphere, not in Europe or North America where most early researchers worked. South America and Africa were part of the supercontinent Gondwana during the Permian and Triassic, and they have yielded fossils that are rewriting the story of how reptiles diversified and how the mammal lineage began. Otero represents a generation of Latin American scientists who are leading the field from within their own countries rather than sending their specimens abroad.

Website:
https://explorers.nationalgeographic.org/directory/alejandro-otero 

Digging Deeper Activity:
Find Argentina on a map and then find where it would have been on Pangaea or Gondwana during the Permian period. Why does the location of a fossil matter for understanding how animals spread across the ancient world? Research one therapsid fossil found in South America and write a brief description of it.

Sources and More Information:

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