Crocodiles and birds are completely different animals if you look at them at first glance. However, they have common ancestry which makes them related. Crocodiles belong to the order Crocodilia and birds belong to the class Aves, even though they have many differences, since both are descended from Archosaurs which lived during the Triassic period for over 200 million years ago, they have certain similarities.
Let’s dive deep and get to the details.
How are Archosaurs Connected to Birds and Crocodiles?
Birds and crocodiles both belong to a larger group called Archosauria, which contains all the extinct dinosaurs. The first Archosaurs appeared around 245 million years ago during the Triassic period and they evolved and diversified in their form over the next 135 million years.
Later, they became predominant on land as vertebrates and lived throughout the Mesozoic era. The Archosaurs can be divided into two lineages: Crocodilians and Avemetarsalians, where they share common physical features. The crocodilians included alligators, and crocodiles and the Avemetarsalians included dinosaurs, birds, and pterosaurs. So, there are skeletal similarities seen among crocodiles and birds since they share a recent common ancestry history.
What is the Evolutionary History Between Crocodiles and Birds?
After the emergence of Archosaurs, they diverged in their forms and different animals emerged. Among them were slender, small reptiles called crocodylomorphs, pterosaurs, dinosaurs, and birds. The true form of the crocodile appeared during the late Triassic period around 210 million years ago.
Some significant features of the modern crocodile that you can see are armored skin and elongated snouts, which were also present in the early Crocodilians. The diversification continued throughout the Jurassic period and new marine and terrestrial animals came into being.
During the Jurassic period around 150 million years ago, the birds came into being, formed a group of predatory dinosaurs called theropods, and a clear translation was seen among the birds to dinosaurs. By the end of the Jurassic period, these birds evolved to form flying capability.
What are the Evolutionary Developments that Distinguish Crocodiles and Birds?
Here are the evolutionary developments that can be seen among crocodiles and birds:
- Bones – Birds develop to form hollow, air-filled bones which reduce their weight and help them in their flight whereas crocodile bones are dense.
- Feather – Birds develop feathers whereas crocodiles don’t.
- Beak – Birds have beaks to support their feeding habit, which is hard and made of keratin, whereas crocodiles develop elongated jaws and teeth.
- Heart structure – To meet the metabolic demands, birds evolved into a high-output cardiac system. Birds have four-chambered hearts, however crocodiles have three chambers.
Comparison between Birds and Crocodile
Since the divergence of the birds and crocodiles, 200 million years ago, both these groups have retained certain similarities. A comparison would help you understand the relationship between a crocodile with a bird.
Skeletal and Structural Differences
Crocodiles have 4 legs with five clawed digits on each foot and the birds have their forelimbs modified into wings and the hind limbs are used for walking or perching. Crocodiles have hip sockets that are sideways and birds have hip sockets facing backward. For flexibility, crocodiles have concave interlocked vertebrae, but birds have a rigid frame so they have convex fused vertebrae.
In crocodiles, gastralia are present which is missing in birds. They also have long snouts with teeth whereas birds have large eye sockets and are toothless, instead of teeth. Crocodiles rely on the ribs and belly movement for breathing whereas birds have a complex respiratory system.
Metabolic Differences
Birds have high metabolic rates as they need to support their flight and food-finding habits whereas crocodiles can survive on infrequent meals, and so they require relatively low energy. Birds have the capability of homeostasis, so they can maintain their body temperature and do not need any external heat source. But, crocodiles need external sources to regulate their body temperature.
Reproduction System
Both birds and crocodiles mate during the spring and they have internal fertilization. They build nests for laying eggs which are calcified and hard. The incubation temperature influences the sex determination of the species and it varies from one species to another. The parents take care of the nest and the hatchlings, until they become independent.
Cognitive Capability
Both birds and crocodiles have complex and different brain structures where the brain of a crocodile is relatively smaller compared to its body and they also lack well-developed cerebrum. Birds have larger brains and they have complex cerebral hemispheres. Crocodiles rely on their inherent intuitive behavior and do not have any learned skill, whereas birds can coordinate complex flights, travel long distances, and also have the capability to solve problems and communicate with the flocks.
Sensory Capability
Crocodiles have a reflective layer behind the retina which is called tapetum lucidum and it helps them with night vision. On the other hand, birds also have excellent eyesight and binocular vision but are not quite equipped with the night time. Crocodiles have a strong sense of smell to detect prey underwater, whereas birds do not depend much on this smell but rather on olfactory senses. Interestingly, crocodiles have a sensory dome on the face which helps them to detect water currents or vibrations, similarly, birds have feathers that help them to sense the air current.
Are Birds Related to Alligators?
A recent study revealed that birds and alligators have similar hearing methods due to their prehistoric ancestral connection. Alligators are the closest living relative to birds, rather than lizards.
