Skinks

Evolutionary history: Skinks (Scincidae) form one of the largest and most successful evolutionary radiations of lizards. Their history reaches deep into the Cretaceous. A skink preserved in approximately 99-million-year-old Myanmar amber already possessed the overlapping scales and compound osteoderms characteristic of modern members of the family. This combination created a flexible form of dermal armour remarkably early in their evolution. Skinks subsequently spread through an enormous range of terrestrial environments, with major centres of diversity today in Australia, New Guinea, Southeast Asia, Oceania, Madagascar and Africa.

Appearance and lifestyle: Many skinks share a sleek appearance with smooth, overlapping scales and an elongated body, yet the family has repeatedly departed from this familiar form. Limb reduction and complete limb loss evolved independently more than fifty times within skinks, probably more frequently than in any other tetrapod lineage. Their reproductive biology is equally remarkable. Both egg-laying and live-bearing species occur, and viviparity evolved independently in numerous branches of the family. In some skinks, embryos receive substantial maternal nutrition through highly complex placental structures, representing one of the closest evolutionary parallels to mammalian placentation found outside mammals. Some New Guinean skinks possess an even stranger adaptation: extraordinarily high levels of the bile pigment biliverdin give their blood and tissues an intense green colour.

Ecological role: Most skinks are active foragers that prey on insects, arachnids and other small animals, although omnivory and herbivory have also evolved in several lineages. They are important consumers within leaf litter, soil-surface and other terrestrial food webs, while also providing prey for snakes, birds and mammals. More than 1,800 living species are currently recognised in Scincidae, making skinks one of the most species-rich groups of lizards on Earth. Many island and narrow-range species are particularly vulnerable to habitat loss, fragmentation and introduced predators. Protecting natural habitats, controlling invasive species and maintaining legal, traceable captive populations are therefore important both for skink conservation and responsible herpetoculture.