Wow! Wing-backed "dinosaur" Dimetrodons were not really dinosaurs, but more related to Mammals!

When is a dinosaur not a dinosaur? When it's a Synapsida. Today's blog will tell you what that means, and why I just learned that a "dinosaur" I've known about since I was a kid is more related to mammals than reptiles! I'm currently reading a book called "The Rise of Mammals" by Steve Brusatte and that's where I learned the Dimetrodon was a link to the first true mammals. You'll learn about that and how the Permian Period led to a mass extinction. 

(Image: Restoration of Dimetrodon grandis by Bogdanov. CC BY-SA 3.0)

Wing-backed "dinosaur" Dimetrodons were not really dinosaurs, but more related to Mammals! 

Often confused for a dinosaur, Dimetrodon is actually a prehistoric synapsid, making it more closely related to mammals (including humans) than to a Tyrannosaurus Rex. 

WHAT IS A SYNAPSIDA? It's a group of living things characterized by a single opening behind the eye socket in the skull. This lineage eventually led to the evolution of mammals. Because of this, Dimetrodon provides critical insights into the early development of mammalian traits, such as specialized jaw muscles and complex dental structures.

Riley Black of Smithsonian Magazine explained it this way: "There is a single large hole there called the temporal fenestra, and it was the place where some of the lower jaw muscles attached to the skull. The number of these holes in this part of the skull can immediately tell a paleontologist what kind of animal they are looking at. Dinosaurs have two holes in the same area and are called diapsids. The possession of just one of these holes defines a group of vertebrates called synapsids, the group to which modern mammals (including you and I) belong. As odd as it may seem, this means that Dimetrodon is a distant relative of ours."

This predator ruled the Earth roughly 295 to 272 million years ago during the Early Permian period—finishing its reign nearly 40 million years before the first dinosaurs ever appeared.

(Photo: Dimetrodon Skull. Credit: Wikimedia.Jeff Kubina Columbia, Maryland) 

ABOUT THE DIMETRODON

The Back Sail: Its most striking feature is a large dorsal sail formed by elongated neural spines extending from its vertebrae. While paleontologists once believed it was strictly for thermoregulation (warming up in the sun), current theories also suggest it served as a display to attract mates or intimidate rivals.

Unique Teeth: Its name means "two measures of teeth." Unlike the uniform teeth of reptiles, Dimetrodon possessed heterodont dentition— that is, different types of teeth used for different tasks, such as sharp canines for piercing and serrated teeth for shearing flesh.

Size:  Depending on the species, Dimetrodon could grow between 5.6 to 15 feet (1.7 and 4.6 meters) in length and weighed as much as 550 pounds (250 kg). It walked with a sprawling, four-legged gait similar to a modern crocodile.

What Dimetrodon's Ate:  A variety of prey including freshwater fish, amphibians like Eryops, and early land-dwelling herbivores.

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ABOUT THE PERMIAN PERIOD- and WHY the "Great Extinction" 

The Permian Period, occurring 299–251 million years ago as the final, critical phase of the Paleozoic Era, saw the assembly of the supercontinent Pangea, massive climatic extremes, and the formation of the Permian Basin. It concluded with Earth's most severe mass extinction, wiping out over 95% of marine life and initiating a new era of life. 

Key Aspects of the Permian Period:

• Significance: It was a defining turning point in Earth's history, transitioning from a cooler early climate to extreme heat, arid deserts, and the assembly of the supercontinent Pangea (all continents combined into 1 massive landmass), which profoundly affected global weather patterns and habitats.
• The End Extinction: The Permian ended with the "Great Dying" (approx. 251.9 million years ago), the largest extinction event in history. 
• Causes likely involved massive volcanic eruptions in the Siberian Traps, releasing carbon dioxide and causing catastrophic global warming, ocean acidification, and oxygen depletion
  .  This d
  rastically altered from high-oxygen to low-oxygen levels, contributing to the mass extinction.
• Geography: Almost all landmasses gathered into the C-shaped supercontinent Pangea, surrounded by the global ocean, Panthalassa.