Why Alligators Taste Like Chicken
I have not tasted alligator myself but I have often heard that they “taste like chicken.” Yeah, I know, everything tastes like chicken. With alligators though, this might be more true than we realize. That is because the closest living relative to crocodilians (crocodiles, alligators, caiman, and gharials) are birds, with turtles being close behind. Not snakes, not lizards, or even the tuatara. Birds. This means either crocodilians are birds or birds are reptiles. The popular consensus is that birds are reptiles - and modern-day dinosaurs.
Humans love to put things into neat little categories. Unfortunately, things don’t fit into neat little categories. Unfortunately, life doesn’t work that way. Especially in nature. We have categorized animals into six groups - invertebrates, fish, amphibians, reptiles, birds, and mammals. And each group shares commonalities. Or are there exceptions? Of course, there are exceptions. There are always exceptions and it makes life more complicated than it should be.
Let’s use reptiles as an example since this is a reptile blog. One of the first things people think about is that they’re “cold-blooded” (the fancy term is ectothermic.) It’s more complicated than that. A study published in 2016 found that the Argentine black and white tegu can generate their own heat (endothermic) during mating season and female pythons coil around their eggs and shiver - generating enough heat to keep their eggs seven degrees warmer than the ambient temperature. So there are exceptions to that rule. It is also believed that all reptiles lay eggs....except that it is thought that 20-30% of lizards and snakes give live birth, like all boas, vipers, pit vipers, and blue tongue skinks. And then there are the monotremes. Five species of mammals that lay eggs (the platypus and four species of echidna.) It’s easier to tell snakes from lizards because they have no legs… except for a few species of lizards that also don’t have any legs. Reptiles have skin made up of scales or scutes made up of keratin (like our nails and hair.) Crocodilians and turtles also have osteoderms (bone) underlying their scales. Birds also have scales on their legs and their beaks are bone-covered in a keratin lining. Feathers have also been shown to be modified scales. A study done showed that if alligator embryos are introduced with the gene that creates the feather, they will grow feathers - or at least try to.
Many biologists use two types of classification systems. The Linnaeus system, created by Carolus Linnaeus in the 1730s, is grouped by characteristics regardless of ancestry. Then there is Phylogenetics. Created by Willi Hennig in the 1940s, this system classifies only by ancestry, and characteristics are only used to discover ancestry.
According to Phylogenetics, a reptile would be any animal descended from the original group called reptiles. And way back when, birds were in the original “reptile” group before branching out to form modern-day birds. They are part of a group called “Diapsida” which includes all living reptiles. It formed about 300 million years ago and is used to describe the skull. Diapsids developed two holes in each side of their skull. They include all crocodilians, lizards, snakes, tuatara, turtles, and birds. That was 300 million years ago...in modern times, some diapsids have lost one hole (some lizards,) both holes (snakes and turtles), or have heavily restructured skulls, like birds. But they are all still a part of the diapsids because of their ancestry.
Quick terminology warning:
*clade* - a group of organisms believed to have evolved from a common ancestor.
*archosauria* - literally means “ruling reptiles.” It is a clade of diapsids with birds and reptiles as the only living representatives.
*lepidosauria* - a clade of diapsids that include modern-day lizards and snakes and their ancestors.
There are two primary lineages for reptiles. Lepidosauria contains snakes, lizards, and tuatara. They aren’t discussed here much because they aren’t the closest reptilian relatives of birds.
The second group is Archosauria - the common ancestors of birds, crocodilians, and turtles. They were a very successful group of dinosaurs and are what you think of when you think “dinosaur.” They became dominant during the Jurassic and Cretaceous periods. Paleontologists define them as a “crown group” that includes the most common ancestors of birds and crocodilians and all of their descendants. There are two clades found at the very base of Archosauria. Crocodilians and their extinct ancestors are found in Pseudosuchia. Ornithosuchia are modern-day birds and their extinct relatives, including non-avian dinosaurs and pterosaurs (who are not dinosaurs, actually, but a very close relative).
Though I referenced Jurassic Park here, their representation of dinosaurs is all wrong. Since the release of the movie, it has been suggested that velociraptors and T-Rex had feathers. They have now become cute and fluffy - covered in dino fuzz (yes, that is what scientists are calling it.)
Interesting side note on tortoises - until recently, scientists didn’t know where turtles (turtles, tortoises, and terrapin) fit. The DNA sequences say that they are archosaurs. Anatomical research, particularly biomolecules called microRNA, indicated a closer kinship to Lepidosaurs. It was not until 2014 when researchers revisited and updated the foundation of microRNA, was it discovered that they are indeed archosaurs.
So how are birds, crocodilians, and turtles similar in the modern day?
They all lay eggs. While snakes and lizards may give birth to live young, all crocodilians, turtles, birds, and turtles lay eggs. These eggs are covered in calcium that reduces the amount of oxygen that can pass through the shell. The mineral content and texture of the shells vary from species to species. All eggs come out of a common orifice called the cloaca.
All birds, crocodilians, and turtles hatch out of their eggs assisted by an egg tooth. A hard white thing sticks out on the tip of the beak or snoot to help them break out of the shell and fall off shortly after.
Crocodiles and birds build nests and watch over their young. However, turtles win the archosaur award for being deadbeat parents.
Birds and turtles have beaks and no chompers. The upper mandible is a protrusion of the skull and the lower mandible is attached by a hinge. The shape of the beak (or bill) is determined by their diet. The beaks are overlaid by keratin, which gives its glossy appearance in birds. And like our fingernails, it is replaced when it wears out. Millions of years ago, both birds and turtles had teeth. The oldest known fossil, the Archaeopteryx, definitively a bird, had a set of chompers. Discoveries in Xinjiang, China have found fossils of turtles from 160 million years ago with teeth remnants.
Their skulls are attached to the spine at a single point, known as an occipital condyle. This allows birds and reptiles to rotate their heads better. Or, if it’s an owl, rotate their heads to do some freaky Exorcist thing. Mammals have two occipital condyles.
The lower jawbones are made up of five different pieces instead of just the one that humans have.
Red blood cells (or erythrocytes) contain are nucleated. Mammals have non-nucleated red blood cells.
Both birds and crocodilians have four-chambered hearts. The bird's heart operates more or less like the human heart while crocodilians have a small feature called the “foramen of panizza” that allows some mixing of oxygenated blood with deoxygenated blood. Turtles, like other reptiles, have three-chambered hearts, but scientist consider them to be transitory between a reptile’s three chambers and a bird’s four chambers
Birds and reptiles pee a special way, too. There is less water in their pee and it comes out in white globs called uric acid. For those of you that have wondered what it is while scraping bird droppings off of your car. They still do release some liquid and they still poop like us.
And of course, there are some major differences - appearances for starters. Crocodilians have heavy bones, and a turtle’s bone is so heavy that its shell is a modified rib cage. Birds have hollow bones that help them to fly, a fused collarbone (wishbone,) three front-facing toes, and of course, much prettier modified scales called feathers.
For centuries many scientists hypothesized that birds were reptiles due to anatomical similarities. In 1860, archeologists discovered a very well-preserved fossil of the Archaeopteryx lithographica, a dinosaur that displayed a blend of reptile and bird. Found in Germany and believed to have lived 150 million years ago during the Jurassic period, A. lithographica was about the size of a raven, and though it had a primitive shoulder girdle that would limit its ability to flap its wings, it was believed that they had some ability to fly according to feathers preserved in the fossils. Eureka! The missing link proving that birds and reptiles were closely related was discovered!!
Though in the minority, of course, there are scientists that dispute the whole birds-are-dinosaurs thingymajig. They argue that A. lithographica was not an evolutionary link to dinosaurs but a true bird. Alan Feduccia of the University of North Carolina said: (My opinion of what he said is in asterisks:
Archaeopteryx’s wings and feathers were identical to modern birds. *There is no way to test a fossil and modern bird feathers to see if their composition is identical.*
True birds were found in China that predates the discovery of Archaeopteryx. *I address this below.*
The best evidence that birds don’t come from dinosaurs is woodpeckers. To try and keep it short, woodpeckers have tongues as long as their bodies, excluding their tail feathers, and require a special hyoid apparatus to accommodate that. This is considered an “incredibly complex system” that could not have evolved. Instead, it would have to be designed and created from the start. *I think this is a false equivalency.*
There was no evolutionary evidence that explains bird migration. *How are fossils supposed to show genetic evidence of how birds began to migrate? We don’t even understand how modern-day birds know where to migrate either.*
Modern-day birds also have unique and super-efficient hearts and lungs. *Comparing adaptations of modern-day birds to ancestors that lived 150 million years ago is ridiculous.*
The oldest fossil of a feather looks just like a modern bird feather. *Again, there is no way to test a fossil to determine if it worked like a modern-day feather.*
There was no evidence presented on how flight feathers evolved from scales *How could they know that by looking at a fossil?*
In their conclusion, their argument is that there is no evidence that birds evolved from dinosaurs and that the fossil evidence that does exist shows that Archaeopteryx existed as a true bird at the time of dinosaurs with other true birds. In other words, there is not an intermediary species that connect birds and dinosaurs.
CHINA: Yes, there were fossils found in China that were about ten million years older than Archaeopteryx. This new find is called Aurornis xui. While the study authors argue that Auronis represents the earliest known bird, other scientists like Luis Chiappe, a vertebrate paleontologist at the Natural History of Los Angeles, say that it could just be a bird-like dinosaur. He also states that he doesn’t think it was a true bird, but a very close ancestor, noting that Auronis’ forelimbs were too short to be a true bird and that it was too big to fly. It is not known whether Archaeopteryx could fly and they are much smaller.
Finally, China is not a paragon of honesty and transparency. In 1999, a press conference was held by National Geographic to introduce the fossil of an animal called “Archaeoraptor liaoningensis.” Like Auronis, it was claimed to be a missing link between terrestrial dinosaurs and birds that could fly. Later, National Geographic announced that the fossil could be a composite of more than one fossil. This is quite a common problem in China as most of the fossils found are sold by farmers who found them. The more intact the fossil, the more money they will get. Auronis was an outstanding specimen - almost too good to be true, China did not allow outside access for examination, and was obtained from a farmer. Since it wasn’t discovered by a paleontologist or archeologist in situ, there is a legitimate reason to question the authenticity.
So are birds reptiles or not? That's up to you!
Before I list my sources, don't you hate it when you find cool pictures and you can find no place to fit them into your blog. Here are three pictures of the eyetooth found on birds, turtles, and crocodilians.
Here are my sources....shocking in length, I know. It's all interesting stuff, I can assure you. This mighty source list should explain why this sucker was so long...and show oh how much more I left out!