What Makes A Dinosaur?

What Makes A Dinosaur?

Thanks to 23andMe for sponsoring this video!
Due to a revolution in our understanding of the tree of life, birds are dinosaurs, while dimetrodons are not.

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FYI: We try to leave jargon out of our videos, but if you want to learn more about this topic, here are some keywords to get your googling started:

Systema Naturae: A 1735 book by Carl Linnaeus that outlined his hierarchical classification of animals.
Plagiuri: an early,now disused, biological subclassification of fish used by Linnaeus that also included dolphins and whales.
Anthropomorpha: a defunct taxon established by Linnaeus for genera Homo (humans), Simia (monkeys and apes in general) and Bradypus (sloths).
Cladogram: A branching diagram showing the evolutionary relationship between species.
Dimetrodon: An extinct carnivorous synapsid related to early mammals.
Plesiosaur: An extinct marine reptile with a long neck related to modern snakes.

Species featured in this video:
Brown-throated sloth (Bradypus variegatus)
Sperm Whale (Physeter macrocephalus)
Atlantic salmon (Salmo salar)
Flathead Grey Mullet (Mugil cephalus)

Credits (and Twitter handles):
Script Writer: David Goldenberg (@dgoldenberg)
Script Editor: Emily Elert (@eelert)
Video Illustrator: Ever Salazar (@eversalazar)
Video Director: Kate Yoshida (@KateYoshida)
Video Narrator: Kate Yoshida (@KateYoshida)
With Contributions From: Henry Reich, Alex Reich, Peter Reich
Music by: Nathaniel Schroeder:


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If you liked this week’s video, we think you might also like:
– After her great video on Dimetrodon The Brain Scoop’s Emily Graslie started a blog devoted to the dinosaur confusion in modern toys:

– A new Nature paper suggesting our evolutionary history of dinosaurs might be very wrong


Angielczyk, K. (2009). Dimetrodon is not a Dinosaur: Using Tree Thinking to Understand the Ancient Relatives of Mammals and their Evolution. Evolution: Education and Outreach 2:257–271. Retrieved from:

Romero, A. (2012). When Whales Became Mammals: The Scientific Journey of Cetaceans From Fish to Mammals in the History of Science. New Approaches to the Study of Marine Mammals. Chapter 1. Retrieved from:

Switek, B. (2010). Why a Pterosaur is Not a Dinosaur. Smithsonian. Retrieved from:

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