What Makes Sea Turtles and Land Turtles So Different

Although the phrase ‘turtles all the way down’ is just an expression, turtles really are found all around us. While most people know about sea turtles, many don’t know that there are land turtles that aren’t considered tortoises. Today, we will explore the similarities and differences between sea turtles and land turtles.

Both sea turtles and land turtles are related and belong to the Testudines order. The split between the two, however, occurs around the taxonomic family, with sea turtles divided into a superfamily, Chelonioidea, and land turtles being specifically assigned to the genus Terrapene and Cuora. Land turtles, also known as box turtles, are divided into two groups: those related to American pond turtles and Asian box turtles. Both groups are land-based turtles that are distinct from other land-dwelling Testudines, such as tortoises. Sea turtles live in the ocean, while box turtles live on land. Additionally, the habitats and distribution of these two animals are distinctly different. Let’s take a look at these differences, plus a few more, below.

Taxonomy

There are seven species of sea turtles (all divided into their own genus). Sea turtles, along with all other turtles, tortoises, and terrapins, belong to the Testudines order. Marine-dwelling turtles within this order can all be grouped under the superfamily Chelonioidea. In short, members of the superfamily Chelonioidea are referred to as sea turtles. You can further break sea turtles into two groups: those with hard shells and those with leathery shells.

Land turtles, like sea turtles, belong to the Testudines order. Unlike sea turtles, which belong to the large superfamily Chelonioidea, land turtles are classified into the genera Terrapene and Cuora. Members of the Terrapene genus are called box turtles and are closely related to the American pond turtles. Members of the Cuora genus are called Asian box turtles and are also considered land turtles.

Appendages

One of the easiest ways to tell the difference between a sea turtle and a land turtle is the appendages. Sea turtles have four flippers instead of legs. The two front flippers are generally longer than the two back flippers. Sea turtles use these flippers to swim, forage, and even hold their food. Box turtles, both the American and Asian groups, have legs with claws. Since box turtles are terrestrial, true legs are essential for long-term locomotion. While some box turtles will occasionally venture into swampy regions, true swimming and diving are nearly impossible.

Shells

While both sea turtles and land turtles have shells, they are quite different. Sea turtles have large, expansive shells that help protect them from predators. There are two types of sea turtle shells: hard and leathery. Only one sea turtle species, the leatherback turtle, has a leathery shell. Regardless, neither type of sea turtle is able to retract into its shell if threatened. Box turtles have very hard shells. Additionally, box turtles are able to retract their legs and head into their shells. A special adaptation that box turtles have is the ability to hinge their shells closed, completely protecting themselves from potential predators.

Diet

The diets of sea turtles vary quite a bit. Of the seven species, the loggerhead, Kemp’s ridley, olive ridley, and hawksbill turtles are omnivorous. Their diet includes decapods, grasses, seaweed, sponges, worms, fish, and more. Green sea turtles become totally herbivorous as they mature, leatherback turtles only eat jellyfish, and hawksbill turtles eat mostly sponges. Land turtles are primarily omnivorous and will eat a wide variety of foods, including plants, insects, and small animals. They are known to eat worms, insects, vegetation, fruit, and gastropods.

Distribution

Sea turtles can be found in every ocean of the world, save for the polar regions. Box turtles are native to North America and can now be found across most of the United States, northern Mexico, and the Yucatan Peninsula. The Asian box turtle can be found from China to Indonesia and the Philippines, Southeast Asia, and northern India and Bhutan.

Habitat

As a marine reptile, sea turtles are found exclusively in the oceans of the world. They generally prefer regions near continental shelves but often venture into seaweed growths, shorelines, and coral reefs. Box turtles can live in a wide range of habitats. Generally, the various species of box turtles can be found in forests, grasslands, deserts, and even rainforests.