Are Chickens Reptiles? Are Chickens Dinosaurs?

You might have been surprised to discover that birds are actually descendants of dinosaurs. They have evolved for millions of years from the earliest dinosaur species and have survived because of their ability to fly and search for food all over the world. Does this also include chickens?

Are Chickens Dinosaurs?

Chickens are not dinosaurs. They are descendants of dinosaurs and are considered a distinct group of animals, all on their own. They are actually loosely related to one specific species of dinosaur, the T-Rex. Scientists studied the amino-acid sequence found in collagen from the fossils of a T-Rex and discovered that this dinosaur had a sequence that was similar to a chicken.

In fact, there are certain similarities between what we know about dinosaurs and modern-day chickens. For example, both chickens and dinosaurs have similar bone structures.

In addition, numerous dinosaurs actually had feathers. While these were not used for flight, they helped to regulate the animal’s body temperature.

To help understand the relationship between the T-Rex and chickens a little better, we need to get more scientific. Chickens and all birds are classed into the suborder Theropoda. Tyrannosaurs also fall into this suborder. This suborder is part of the kingdom of Animalia and the phylum Chordata.

Essentially, this is the Linnean classification system that was developed by biologists way back in the 1730s. This system classified all living beings based on their characteristics and physical features.

Painting courtesy of Luis Rey.CC BY 2.5, via Wikimedia Commons

Characteristics Of The Suborder Theropoda

To understand how chickens and dinosaurs could be related, let’s look at the primary characteristics of Theropods.

  • Hollow bones. Both tyrannosaurs and birds, including chickens, have hollow bones.
  • Three-toed feet with claws. Once again, chickens and tyrannosaurs share this characteristic.
  • A wishbone. This is also a common characteristic shared by chickens and tyrannosaur dinosaurs.

While both chickens and dinosaurs share these characteristics, others only apply to dinosaurs, like sharp and recurved teeth that were used for eating flesh. In this case, chickens have beaks and no teeth.

Additionally, some dinosaurs evolved to have a type of bat wing. This consisted of membranes that were stretched between the toes to allow the creature to glide down from the branches of trees. One such creature was the Yi Qi, whose remains were discovered in China around 160 million years ago.

But we can go even further down this classification chain and recognize a suborder or clade called Coelurosauria. Both chickens and tyrannosaurs belong to this clade. One common characteristic found in Coelurosaurs is that they have feathers. 

Going further down the classification chain, we learn that there are also subgroups within the Coelurosauria clade. One of these is Tyrannosauroidea which is comprised of all the tyrannosaur dinosaurs, while another is Maniraptoriformes which is comprised of all birds, including chickens.

All of this tells us that chickens and all other birds, and dinosaurs are loosely related. In fact, scientists seem to agree that birds and chickens descended from dinosaurs.

Why Chickens Are Modern-Day Descendants of Dinosaurs

Scientific research has shown us that around 66 million years ago, the earth was hit by a catastrophe that wiped out almost all living creatures except for a small group of therapods.

It is believed that a large asteroid or comet hit the Earth around the Gulf of Mexico. This saw the birth of the Cretaceous-Paleogene event that caused the extinction of many plants, mammals, insects, fish, and lizards. 

As the earth recovered slowly, the small group of therapods and any other remaining animals started to spread around the world and evolved over time to become the species that we know today. In fact, it is believed that domestic chickens are descended from the red junglefowl found in Asia.

Are Chickens Reptiles?

While many people see dinosaurs as reptiles, you might be wondering whether chickens can also be classed as reptiles. Chickens are not reptiles. Chickens are classified as birds. They are actually in a group of their own called fowls. And they do share some characteristics with both reptiles and mammals.

How Are Reptiles Classified?

Here are some of the more common characteristics that classify reptiles based on the Linnaean system:

  • Reptiles are vertebrates and have scales
  • They lay eggs with a tough or hard shell
  • Reptiles have a bony internal skeleton
  • They have internal lungs

If we look at these characteristics, except for the egg-laying, we would instantly say that chickens are definitely not reptiles. Similarly, reptiles are cold-blooded, while chickens are warm-blooded.

But, in the 1940s, a new classification system was created. This is referred to as the Phylogenetic system. This system classifies all animals merely based on their ancestry rather than their physical characteristics.

Earlier, we learned that chickens are actually descendants of dinosaurs, and their origin could be traced back to these creatures. In the same vein, reptiles can also be traced back to ancient dinosaurs. From this, we could conclude that chickens might just be able to be classed as reptiles.

However, chickens and birds belong to the clade Archosauria while reptiles belong to a variety of different clades, as explained below:

  • Squamata – snakes, iguanas, geckos
  • Testudines – turtles
  • Crocodylomorpha – crocodiles

Using this form of classification, we now learn that reptiles do not form a clade of their own because “reptile” is not a valid phylogenetic group. So, we could conclude that birds are not reptiles even though they share a similar ancestry.

The Evolution Of The Modern-Day Chicken

Evolution is a varied and interesting topic to explore and can help us to understand how chickens became what we know them to be today.

To start with, evolution has to have a living ancestor, and we now know that chickens had dinosaur ancestors. In fact, chickens are more closely related to dinosaurs than they are to reptiles.

This is because reptiles evolved around 320 million years ago, while mammals (warm-blooded animals) evolved around 40 million years later. Lots of other evolutionary branches were created over the following 120 million years until the catastrophe hit the earth 66 million years ago, which wiped out many, many living creatures.

If you remember, we noted earlier that the only group to survive was a small group of theropods. These theropods continued to evolve to become the birds that we know today. In fact, modern bird species started to evolve around 10 million to 15 million years after the dinosaurs became extinct.

Scientists have concluded that some ancient birds lost their dinosaur teeth and formed bills around 116 million years ago. This allowed them to adapt to their current environment and is the basis of all evolution that can be seen in both animals and plants.

Exploring The History Of Domestic Chickens

The history of today’s domestic chickens can be traced back to around 10,000 years ago with their ancestor, the Red Junglefowl. This bird was found widely in Southeast Asia and Oceania.

Domestic chickens became widespread rather quickly because they provided a good source of fresh eggs and meat without competing with humans for food. 

This, of course, spurred on the necessity to develop breeds that showed certain characteristics or physical traits that were favored by both commercial producers and domestic chicken owners.

The first Standard of Excellence for chicken breed characteristics was published in 1874 by the American Poultry Association. This was followed by the introduction of breeds such as the Brahmas, who were slow in maturing and not the greatest egg producers.

It was then discovered that lighter breeds, such as the Leghorns, Minorcas, and Anconas, were much better at egg production than their larger cousins. However, these smaller birds did not provide enough meat.

So, breeders developed other breeds, such as the Rhode Island Red, White Wyandotte, and Barred Rock, who were both decent in size and good at egg production.

Of course, these days, it’s the hybrids that outshine most of the pure breeds when it comes to annual egg production. Many of these birds can easily produce over 300 eggs per year. These birds can be traced back to 1936 when Henry A. Wallace, the founder of the Pioneer hybrid seed company, decided that producing hybrid hens could produce better layers. 

Are Chickens Reptiles Or Dinosaurs Or Both?

This brings us to the debate of whether chickens are reptiles or dinosaurs, or both. Scientists have now firmly established that chickens are descendants of dinosaurs, especially when they compare the DNA sequences from the fossils of certain dinosaurs with those from modern-day chickens.

However, whether chickens are also reptiles seems to be a highly contested argument. While some experts agree that chickens share ancestry with reptiles, according to their lack of shared characteristics, it could generally be concluded that chickens are not reptiles, especially in the sense of how we now classify reptiles as being cold-blooded.

It’s likely that this debate will go on for many years to come.

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