Crocodiles Are Surprisingly Close Relatives of Birds
Crocodiles are more closely related to birds than to lizards or snakes, because both belong to the ancient archosaur branch of reptiles.
Details
Crocodiles may look like the classic reptiles, but their evolutionary family tree puts them surprisingly close to birds. Both crocodilians and birds belong to Archosauria, an ancient branch that also includes the extinct dinosaurs and pterosaurs. Lizards, snakes, and tuataras belong to a different major branch of reptile evolution. This means a crocodile shares a more recent common ancestor with a bird than it does with a lizard or snake. The relationship can feel strange because modern birds and crocodilians look dramatically different, while crocodiles resemble other reptiles more closely on the surface. Evolutionary relationships, however, are determined by shared ancestry rather than simple visual similarity. Large-scale genetic studies have helped support the placement of crocodilians and birds together within the archosaurs. Research on crocodilian genomes has also used their relatively slow evolutionary rate to help reconstruct genetic features of their ancient common ancestors. The bigger lesson from the family tree is that familiar labels such as reptile do not always match the branches people intuitively imagine. Birds retain their place within the evolutionary history of reptiles while also representing the surviving lineage of dinosaurs.
More videos
- Why Spider Legs Work Like Tiny Hydraulic Systems
Spiders lack extensor muscles in their major leg joints, so they use blood-like fluid pressure to extend their legs, which curl when that pressure stops.
Tags: Medicine
- Turtles Have Been Around for More Than 200 Million Years
Some of the oldest known turtle fossils date to about 215 million years ago, showing turtles were already around during the Triassic Period.
Tags: Medicine
- Why Crows Cover Themselves in Ants
Crows and many other birds deliberately cover their feathers with ants, a behavior called anting, but scientists still do not know exactly why.
Tags: Medicine
- Scientists Identify About 18,000 New Species Every Year
Scientists identify about 18,000 new species each year, revealing how much of Earth life is still unknown to science.
Tags: Medicine
- Lungfish Are Closer to Humans Than Most Fish
Lungfish are more closely related to humans and other land vertebrates than they are to most familiar fish like salmon and tuna.
Tags: Medicine
- Some Sea Stars Can Regrow an Entire Body From One Arm
Some sea stars can regrow an entire body from a single arm, and one species can split into two males that later become females as they grow.
Tags: Medicine
- Your Body Has More Bacterial Cells Than Human Cells
Your body has roughly 30 trillion human cells and 38 trillion bacteria, so bacteria slightly outnumber human cells, with most concentrated in the gut.
Tags: Medicine
- Sleep Helps Flush Waste From the Brain
In mice, sleep expands the space between brain cells, helping cerebrospinal fluid wash away waste, including proteins linked to Alzheimer’s disease.
Tags: Medicine
- Y Chromosome Loss Becomes Common in Men With Age
By age 70, about 35% of men have lost the Y chromosome from some blood cells, with affected cells ranging from roughly 4% to 70%.
Tags: Medicine
- Humans Are Still Evolving, and It Shows in Surprising Traits
Humans are still evolving, with recent genetic adaptations linked to free-diving, high-altitude living, disease resistance, and digesting milk as adults.
Tags: Medicine
- These Ants Rescue Their Wounded After Termite Battles
Megaponera analis ants rescue injured nestmates after termite battles, carrying them home so they can recover and return to future raids.
Tags: Medicine
- The Tiny Ear Muscle Some People Can Flex on Command
Some people can voluntarily flex a tiny middle-ear muscle called the tensor tympani and hear a low rumbling sound that only they can hear.
Tags: Medicine
