The term lizard has a specific meaning to scientists, and that meaning does not include turtles. Therefore, turtles are not lizards. Simply put, most species of turtle are reptiles that belong to the taxonomic order Testudines, while lizards are vertebrates belonging to the taxonomic order Lacertilia. The two orders are very distinct from one another both physically and anatomically.
While lizards have dry skin covered in scales (such as on their backs), turtles have soft shells made of bony plates called scutes and their skin is moist underneath those scutes. Turtles also lack an external ear opening like true lizards do; instead they possess a small hole between their eyes which leads directly to their middle ear cavity — a trait more commonly known as an interparietal. Also, while turtles have beak-like structures called jaws, lizards lack these jaw structures and instead have a structure called the retroarticular process that functions to help close the jaw of the reptile.
Although certain species of turtles are sometimes referred to as ‘tortoises’, they are much more closely related to one another than any tortoise is related to other reptiles. In fact, in some cases a turtle may be more closely related to a lizard if it shares similar physical or anatomical traits, rather than an entire order of lizards. For example, many marine turtles possess external ear openings like aquatic lizards do — including sea snakes and even mosasaurs (extinct giant marine lizards). One must look at the physical traits of a reptile to determine its place in the taxonomic order. For instance, soft-shelled turtles do possess large bony plates on their shells like lizards and other reptiles have on their backs.
Some scientists speculate that it may be more appropriate for certain species of turtle to belong within the taxonomic order Squamata, rather than Testudines. However, this idea has not gained much popularity due to how dramatically different those squamate families are from one another (for example: most squamates refer to snakes). Therefore such an arrangement would require entirely new taxonomy depending on what was moved where — making it difficult for scientists and conservationists alike to make clear distinctions between similar animals.
The most widely accepted fact is that turtles are reptiles and lizards are another group of reptiles. Therefore, the terms turtle and lizard can never be interchanged in any context.
I have a big soft spot for turtles. I grew up near a pond that was full of snapping turtles. Now and then I’d see them crawling across our front yard, which was always exciting.
Now I write about turtles for this website as a fun side hobby. Glad you stopped by!