Milk Snake

Associated Smithsonian Expert: George R. Zug, Ph.D.

Zoologist George Zug takes a break from his fieldwork studying reptiles and amphibians while in Myanmar.

Courtesy of Jeremy Jacobs

Dr. George R. Zug is an emeritus research zoologist in the Department of Vertebrate Zoology at the Smithsonian National Museum of Natural History and one of the world's foremost experts on reptiles and amphibians of the Pacific. His current research focuses on the biology and systematics of Asian and Pacific amphibians and reptiles. He first became interested in herpetology as an undergraduate when a professor asked him to join a herpetological expedition to Cuba [pre-Castro]. He majored in biology at Albright College and then went on to obtain a master's degree in zoology at the University of Florida and a doctorate degree in zoology at the University of Michigan. The thing he likes best about studying reptiles and amphibians is excitement of discovery, whether new species or aspects about a species' biology.

Meet our associated expert

This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.

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Textured foot of fan-footed gecko (Ptyodactylus hasselquistii)
Courtesy of Todd Pierson, via CalPhotos, CC-BY-NC-SA


About Squamates (Order Squamata): Body Covering

Squamates, which include lizards and snakes, are named for their scales (squamatus = “scaly”). Their scales, which are part of their skin, are typically overlapping. As squamates grow, they periodically shed (molt) the entire outer layer of skin, in contrast to humans who shed skin in tiny flakes. Snakes rub against rough surfaces to loosen their skin and peel it back off head, limbs, and torso. The skin of squamates tends to be patterned with colors, which may help camouflage (e.g., green tree snakes) or warn predators of toxicity (e.g., coral snakes). Some squamates (e.g., anoles) have surface pigments that allow them to change colors. Scientists have discovered that squamate skin also has intricate textures, visible only through a microscope. Magnification reveals patterns of ridges, pits, or spines. The microscopic, branching hairs on the ridged toes of geckos have been found to help them cling to vertical surfaces, but the functions of many other squamate skin textures are unknown.

Fossil Jurassic marine reptile (Icthyosaur)
Photo by Chip Clark, Smithsonian, National Museum of Natural History

About Reptiles (Class Reptilia): Paleobiology

Reptiles first appeared on Earth about 300 million years ago (during the Pennsylvanian). Before then, all back-boned animals (vertebrates) were tied to the water, living in or near swamps. Their eggs were laid underwater. A set of gradual adaptations, such as thicker, scaly skin, allowed life on land to emerge. The biggest change was the development of an egg containing layers of membranes (amniotic membranes) to retain water, supply food, and store waste for an embryo. Two further innovations – the eggshell and internal fertilization – marked the first reptiles. Fertilization inside the female and shelled, amniotic eggs freed reptiles from aquatic life. They diversified into dinosaurs, crocodiles, lizards, snakes, turtles, tuataras, and birds as they colonized a variety of land habitats. For more than 100 million years, reptiles dominated the Earth. The largest reptiles were wiped out in the extinction event at the end of the Mesozoic, but their smaller descendants live on today.