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Your Holiday Dinosaur

Use and Abuse of the Fossil Record

Penny Higgins

December 2, 2014

Most vertebrate paleontologists agree that modern birds evolved from dinosaurs. To paleontologists, there is no simple bird-dinosaur dichotomy. Rather there is a continuum of animals that are at first, clearly dinosaurs (like Tyrannosaurus and Velociraptor), then at the end are clearly birds, like all the modern birds that we see. We recognize lots of ‘in between’ animals, like Archaeopteryx that appear to be at once both bird and dinosaur.

To simplify, many, including me, refer to birds as dinosaurs. Sometimes, we add the term ‘avian’ or ‘non-avian’ to the front of dinosaur, to distinguish between modern, flying birds and their relatives, and the big scary ones that went extinct 65 million years ago.

The interesting outcome is that what this means is that, at least in the United States, we traditionally have a huge family meal on the fourth Thursday of November, in which we consume vast quantities of roasted dinosaur meat.

All right, but how do we know that?

If you’re like me, you need only go outside and hang out with the chickens to realize that these are just feathered versions of the velociraptors from the original Jurassic Park movie.

Yeah, but maybe they based those off of chickens.

I can do better than that, I promise. What is presented here is a re-hashing of what is already available here, at the University of California Museum of Paleontology’s website.

They start with a simple turkey skeleton and explain some of its dinosaurian features:

The skeleton of the Wild Turkey, Meleagris gallipavo. Here is the basic skeleton. Credit: University of California Museum of Paleontology. Copyright 1994-2014 by the Regents of the University of California, all rights reserved. Used with permission.The skeleton of the Wild Turkey, Meleagris gallipavo. Here is the basic skeleton. Credit: University of California Museum of Paleontology. Copyright 1994-2014 by the Regents of the University of California, all rights reserved. Used with permission.

I’ll be expanding on this using this nice summary of the similarities between birds and dinosaurs prepared by Thomas Holtz, based on the skeletal drawing above.

The skeleton of the Wild Turkey, adapted to show dinosaurian features. In black is the basic skeleton. Red arrows highlight characteristics shared between birds and dinosaurs. Credit: Skeleton from UCMP Copyright 1994-2014 by the Regents of the University of California, all rights reserved. Used with permission.; Red highlights: Thomas Holtz (@TomHoltzPaleo on Twitter)The skeleton of the Wild Turkey, adapted to show dinosaurian features. In black is the basic skeleton. Red arrows highlight characteristics shared between birds and dinosaurs. Credit: Skeleton from UCMP Copyright 1994-2014 by the Regents of the University of California, all rights reserved. Used with permission.; Red highlights: Thomas Holtz (@TomHoltzPaleo on Twitter)

There are a lot of terms here that might be a little overwhelming, so I’d like to summarize them first. We’ll go step by step, highlighting the evolution and relationships between birds and dinosaurs.

First, let’s consider the taxonomy – the scientific names. These are listed from most inclusive (the biggest groups) to the most specific (smaller groups – subsets of the next group up).

We can illustrate these relationships in the following drawing. Bigger boxes are larger taxonomic divisions and include more animals. The divisions get smaller and smaller as we move toward modern birds, Aves (in darkest red).

Aves - G.E. Lodge (T.M. Keesey) Public Domain Pygostylia - Changchengornis hengdaoziensis - Matt Martyniuk CC 3.0 NC-SA-By Eumaniraptora - Archaeopteryx - T.M.Keesey Public Domain Maniraptora - Jianchangosaurus yixianensis - Hanyong Pu, Yoshitsugu Kobayashi, Junchang Lü, Li Xu, Yanhua Wu, Huali Chang, Jiming Zhang, Songhai Jia & T. Michael Keesey CC 3.0 By Neotetanurae - Sciurumimus albersdoeferi - Gareth Monger CC 3.0 By Theropoda - Tyrannosaurus rex - Scott Hartman CC 3.0 NC-SA-By Theropoda - Eodromaeus murphi - Conty (Modified) CC 3.0 By Apatosaurus - Scott Hartman CC 3.0 NC-SA-By Pterosauria - Preondactylus buffarinii - Mark Witton CC NC-SA-By Ornithodira - Dromomeron romeri - Nobu Tamura CC 3.0 By Crocodylia - Crocodylus porosus - Steven Traver Public Domain Archosauromorpha - Prolacerta broomi - T.M. Keesey Public DomainAves – G.E. Lodge (T.M. Keesey) Public Domain
Pygostylia – Changchengornis hengdaoziensis – Matt Martyniuk CC 3.0 NC-SA-By
Eumaniraptora – Archaeopteryx – T.M.Keesey Public Domain
Maniraptora – Jianchangosaurus yixianensis – Hanyong Pu, Yoshitsugu Kobayashi, Junchang Lü, Li Xu, Yanhua Wu, Huali Chang, Jiming Zhang, Songhai Jia & T. Michael Keesey CC 3.0 By
Neotetanurae – Sciurumimus albersdoeferi – Gareth Monger CC 3.0 By
Theropoda – Tyrannosaurus rex – Scott Hartman CC 3.0 NC-SA-By
Theropoda – Eodromaeus murphi – Conty (Modified) CC 3.0 By
Apatosaurus – Scott Hartman CC 3.0 NC-SA-By
Pterosauria – Preondactylus buffarinii – Mark Witton CC 3.0 NC-SA-By
Ornithodira – Dromomeron romeri – Nobu Tamura CC 3.0 By
Crocodylia – Crocodylus porosus – Steven Traver Public Domain
Archosauromorpha – Prolacerta broomi – T.M. Keesey Public Domain

Features of all of these groups are seen in the turkey. Let’s go through and explain them all.

Archosauroformes

antorbital fenestra in a dinosaurThe antorbital fenestra in a dinosaur. Credit: Steveoc86 CC 2.0 By-SA

Archosaurs include organisms like modern crocodilians, all dinosaurs, and birds. Modern lizards, snakes, and turtles are not archosaurs.

Euparkeria, an Archosauriform: Credit: Nobu Tamura CC 2.5 By: Euparkeria, an early Archosauriform: Credit: Nobu Tamura CC 2.5 By

 

Ornithodira

Alligator cervial-to-dorsal vertebrae transitionAlligator cervial-to-dorsal vertebrae transition. Vertebrae are very similar, only really distinct by having ribs (dorsal vertebrae only). Four cervical vertebrae to the left, five dorsal to the right.
Cervical-to-dorsal vertebrae transition in a duckCervical-to-dorsal vertebrae transition in a duck. Notice the change in the shape of the vertebrae. Five complete cervical vertebrae to the left, three dorsal vertebrae to the right.

 

Dinosauromorpha

 

Dinosauria

 

Theropoda

 

Neotheropoda

Pigeon furculum, also known as the wishbone. Credit: Toony CC 3.0 By-SA Pigeon furculum, also known as the wishbone. Credit: Toony CC 3.0 By-SA

The furculum of a dinosaur looks a little different than a turkey wishbone. But it’s there!

The furculm of Tyrannosaurus. Credit: Conty, Dinoguy2 CC 2.5 By-SA The furculm of Tyrannosaurus. Credit: Conty, Dinoguy2 CC 2.5 By-SA

 

 Tetanuridae

 

Avetheropoda

 

Maniraptoriformes

 

Maniraptora

pelvis of a duckThe pelvis of a duck, showing the backward pointing pubis and pygostyle.

 

Eumaniraptora

 

Pygostylia

pygostyleThe pygostyle, where the tail feathers attach in a bird.

 

Ornithothoraces

Structure of the wing bones of a modern bird. Credit: Shyamal CC 2.5 SA-ByStructure of the wing bones of a modern bird. Credit: Shyamal CC 2.5 SA-By
Wing of a duck.Wing of a duck.
Foot of a duck showing the fusion of the tarsus and metatarsus (what appears as a single bone above the toes)Foot of a duck showing the fusion of the tarsus and metatarsus (what appears as a single bone above the toes)
Pigeon. Metatarsal I is part of the backward pointing toe. It is very close to the other toes, rather than higher on the foot.Pigeon. Metatarsal I is part of the backward pointing toe. It is very close to the other toes, rather than higher on the foot.

 

Euornithes

 

Carinatae

Pigeon keeled sternum. Credit: Toony CC 3.0 SA-by Pigeon keeled sternum. Credit: Toony CC 3.0 SA-by

 

Aves

Your turkey shares all of these characteristics in common with various groups of dinosaurs. By extension, one could argue that all birds are dinosaurs.

A fun way to look at some of these relationships can be seen here, in this wonderful summary of the Origins of ‘Avian’ Characteristics (by Albertonykus on DeviantArt)

I invite you to discuss this over dinner this Thanksgiving or Christmas. I might do so myself. Maybe then the family will leave me alone.

Penny Higgins

Penny Higgins's photo

Dr. Pennilyn (Penny) Higgins is a Research Associate in the Department of Earth and Environmental Sciences at the University of Rochester. Most of her research revolves around studying the chemistry of fossil mammal teeth to learn about the environments in which the animals lived and what they might have been eating while living there. She is particularly interested in episodes of rapid climate change in the geologic record. In addition to doing research and managing a geochemistry laboratory, Penny also teaches courses in introductory geology and paleontology at the University of Rochester. When she's not in the office or laboratory, Penny can be spotted writing fiction, practicing the western martial arts, or just screwing around on Twitter.