Lepidosauria

The Lepidosauria (/ˌlɛpɪdoʊˈsɔːriə/, from Greek meaning scaled lizards) is a superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata is a very large group that includes over 9,000 species of lizards and snakes, making it the most diverse group of non-avian reptiles today.

Rhynchocephalia was once a widespread group of reptiles during the Mesozoic Era, but now it has only one living species: the tuatara (Sphenodon punctatus,). The tuatara is a unique reptile that looks a bit like a lizard and lives only in New Zealand.

Lepidosauria is a special group called a clade because it includes all the descendants of the last common ancestor of squamates and rhynchocephalians. These reptiles have distinctive features, like large keratinous scales that often overlap each other. In modern classifications, Lepidosauria is considered closely related to Archelosauria, a group that includes Testudines (turtles), Aves (birds), and Crocodilia (crocodilians).

Evolution

Lepidosauromorpha, a group of reptiles, separated from their close relatives during the Permian period. The earliest known lepidosaur, a type of rhynchocephalian named Agriodontosaurus, lived in the Middle Triassic about 244 to 241.5 million years ago in what is now the United Kingdom. Another early rhynchocephalian, Wirtembergia, appeared slightly later in the same era. During the Cretaceous period, lizards and snakes (squamates) became very diverse, while rhynchocephalians became less common.

Description

Extant reptiles belong to the clade Diapsida, which means they have two pairs of openings on their skulls behind the eyes. The Lepidosauria group is part of Diapsida and includes two main orders: Squamata and Rhynchocephalia. Squamata is the larger group and includes snakes, lizards, and amphisbaenians. These animals can often lose their limbs; snakes and some lizards have lost theirs completely. They also have a special joint in their upper jaw that lets them eat very large prey.

Lepidosauria members can usually drop their tails to escape predators. When they do, the tail grows back, but it is made of solid cartilage instead of proper bones. Their scales are made of a tough material called keratin and they shed these scales in different ways depending on the species—lizards usually shed in flakes, while snakes shed in one piece. These scales overlap like roof tiles, which helps protect them.

Biology and ecology

Squamates include species that give birth to live young, lay eggs that develop inside the mother’s body, or lay eggs outside the body. A few species can even reproduce without a mate. The tuatara lays eggs that take about 14 months to hatch.

Many lepidosaurs use camouflage to stay safe, either by blending in with their environment or changing skin color. Some can drop their tails to escape danger.

Viperines can sense prey by detecting heat, and some snakes catch prey by coiling around it. Chameleons catch insects with a quick, sticky tongue. Lepidosauria includes herbivores, omnivores, insectivores, and carnivores, with diets ranging from plants to small animals. Larger reptiles often prey on smaller ones, including eggs.

Conservation

Lepidosaur species live in many parts of the world, except in very cold areas. For example, some lizards are found in Florida, Mexico, and the Mediterranean region, while the tuatara lives only on a few rocky islands of New Zealand.

Climate change poses a challenge for animals like the tuatara, which cannot move to cooler places on their own. To protect them, scientists are thinking about moving tuataras to islands with cooler weather. Sadly, animals such as cats and rats brought to New Zealand have reduced tuatara numbers, but removing these animals has helped tuatara populations grow again.

Humans also affect lepidosaur habitats by clearing land for buildings or farming. Some snakes and lizards move closer to homes where they find plenty of insects and mice, but they are often killed by people. In the past, events to kill snakes have reduced some snake populations. Introducing new animals, like mongooses to Jamaica, has also hurt local lizards. However, people are working to protect endangered reptiles through breeding programs and safe areas called refuges. Sadly, some reptiles are still used for making products like shoes and bags, but many people are trying to save these animals.