This has picked up popularity in recent years, since Jurassic Park featured one of its key characters, paleaontologist Dr Alan Grant theorized that birds came from dinosaurs and compared the dinosaurs he saw in the flesh to modern birds.
Part of this was based on fact. However, it’s less that birds are descendants of dinosaurs and more like…
Birds ARE Dinosaurs
Birds evolved from the theropod line of dinosaurs, which included the mighty and probably most famous dinosaur Tyrannosaurus rex, Velociraptor and other meat-eating beasts.
But to say birds are descended from dinosaurs is like saying humans are descended from mammals. We are descended from mammals, but it makes more sense to say we are mammals, of the primate lineage!
How Do We Know Birds Evolved from Dinosaurs?
There are several factors that point toward birds being part of Dinosauria, the family of dinosaurs in the animal kingdom, Animalia.
First of all, and probably the easiest to see, are the similarities between avian dinosaurs and birds.
Similarities Between Birds and Dinosaurs
Birds have scales and dinosaurs had feathers. Feathers are a kind of modified scale and you trace them back to the Jurassic Period. The tissue that grows scales in reptiles is similar to tissue that allows birds to grow feathers. And there is mounting evidence that a lot of dinosaurs, particularly the theropods, had proto feathers. Even the Triceratops and other herbivores may have had some kind of proto feather, fur-like coat somewhere along their bodies!
Then there are. Birds and dinosaurs lay and laid eggs, respectively. Some dinosaur species may have given birth to live young, but as far as we can tell, they all laid eggs. This indicates a common ancestor between birds, dinosaurs and reptiles.
A lot of dinosaur eggs were hard-shelled, as are modern birds. They were also made up of calcium and carbon which make eggs more difficult to crack thanks to these elements creating hard crystal structures.
Missing Link Between Birds and Dinosaurs
Calling something a “missing link” is a bit simplistic but it does help to visualize the gaps and connections between groups of extinct and non-extinct species or groups of animals.
The Archaeopteryx itself probably wasn’t an ancestor of modern birds, but it really highlights the similarities between the Maniraptoran dinosaurs, a group very similar to the Dromaeosaur group. Basically modern birds are akin to the small to medium raptors, such as Velociraptor and Deinonychus. Take a look at the Cassowary and its claws to see just how dinosaur-like modern birds are…
The Archaeopteryx was first discovered in Germany. There have been twelve specimens or fossils discovered so far, and has been found preserved in such a good condition that you can clearly see the feathers it had!
Plus one look shows just how bird-like this creature is.
The fossilized Archaeopteryx to the right shows that it could likely pass for either dinosaur or modern bird, and if it could be replicated or seen when alive, I doubt we could tell the difference.
Some things that make it dinosaur are the bony tail and teeth, and some things that make it modern bird are feathers and the evolution of its wings, which were very different from the flying reptiles of the time, such as Pteranodon. It also had a wish bone, an adaptation to strengthen the chest whilst flying.
This transitional species was also rather small, being 51cm long (20″) and weighed between 1.8-2.2lbs).
The Theory of Evolution
In 1859, Charles Darwin published his famous book, On the Origin of Species. The first Archeopteryx was discovered in the 1860’s and lends itself as a brilliant example of how some groups of animals, over a long, long time span, can change so much they become an entirely different species or group of species incapable of breeding with the original organisms due to natural selection placed upon them.
The Archaeopteryx lived in the late Jurassic Period, between 150.8 and 148.5 million years ago. Although discovered in Germany, at the time this would have been around the equator and a similar climate to today’s Florida.
Having lived in the Jurassic Period, this shows just how far back modern birds go back as their traits were taking root.
There were bird-like dinosaurs like Archaeopteryx and dinosaur-like birds such as Alcmonavis poeschli, shown below, but ultimately only one of these two groups survived the third and final devastating extinction event that was the end of the Cretaceous and now we get to see them everywhere we go, our very own modern-day dinosaurs!
Once the majority of the dinosaurs were wiped out along with most of the planet, the remaining groups, including the birds, mammals, reptiles, etc. could then explode into new niches and opportunites once the meteoric dust settled. Being small. agile creatures, it may have helped that birds have relatively short lifespans and can reproduce faster than larger animals, which may have allowed the shorter generation gaps to aid in adapting to new environments.
