Anapsid facts for kids
An anapsid is a type of amniote (an animal that lays eggs on land, like reptiles, birds, and mammals) whose skull does not have any special openings on the sides behind the eyes. Think of it like a solid, bony box for the brain, with just holes for the eyes, nose, and mouth.
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What is an Anapsid?
The word "anapsid" comes from Greek words meaning "without arch." This refers to the skull structure. Most reptiles, birds, and mammals have one or two openings (called fenestrae) in the bone behind their eye sockets. These openings make the skull lighter and provide space for jaw muscles to expand, allowing for a stronger bite. Anapsids, however, lack these openings.
Early Reptiles and Their Skulls
The anapsid skull design is considered the most basic or "primitive" type for early amniotes. The very first reptiles, which appeared around 360 to 300 million years ago during the Carboniferous period, had anapsid skulls. These ancient creatures were among the first vertebrates to live entirely on land. Their solid skulls were a simple, strong design that worked well for them.
Turtles: A Special Case
For a long time, scientists believed that turtles were true anapsids because their skulls also appear to be solid, without the typical openings seen in other reptiles. However, modern research, especially using genetic studies, suggests that turtles are actually more closely related to diapsids (reptiles with two skull openings, like lizards, snakes, and crocodiles). This means that turtles likely evolved their solid skull shape secondarily, losing the openings that their ancestors once had. So, while their skulls look anapsid, they are not considered "primitive" anapsids in the same way the very first reptiles were.
Other Anapsids
Besides the earliest reptiles, another group that had anapsid skulls were the mesosaurs. These were ancient, aquatic reptiles that lived during the early Permian period. They had long, slender bodies and needle-like teeth, suggesting they ate small fish. Their anapsid skull design was part of their unique body plan.
See also
In Spanish: Anapsida para niños
