Viviparous lizard

The viviparous lizard (Zootoca vivipara) is a small Eurasian lizard notable for giving birth to live young across much of its range.

Squamata: The reptile order containing lizards and snakes, distinguished by overlapping scales and a movable skull. This is the larger group to which Zootoca vivipara belongs.
Placenta: An organ-like interface through which a developing embryo exchanges substances with a parent. In this lizard, maternal tissues support embryos, though nourishment remains largely yolk-based.
Alpine ecology: The study of ecological processes in high-elevation environments above or near the tree line. Viviparous lizards inhabit cold mountain regions as well as northern lowlands.
Zootoca vivipara vivipara: A subspecies of viviparous lizard found across parts of northern and central Europe. It represents populations associated with live birth across much of the species' range.
Lizard: A diverse group of squamate reptiles, generally with four limbs, external ear openings, and movable eyelids. The viviparous lizard is one small-bodied member of this broad reptile group.
Lecithotrophy: Embryonic nutrition supplied primarily by yolk stored in the egg. The species' live-bearing embryos obtain most of their nutrients from yolk.
Bergmann's rule: An ecogeographical pattern in which body size tends to increase in colder climates among related animals. Its body-size variation can be examined against broad climatic patterns in ectotherms.
Zootoca vivipara carniolica: A subspecies of viviparous lizard associated with parts of the southern Alpine region. It is among the populations known for laying eggs rather than giving birth to live young.
Amniotic egg: A reproductive structure whose membranes protect and nourish an embryo in a fluid-filled environment. The species retains embryos developing within egg membranes, even when birth is live.
Embryonic development: The process by which an embryo grows and differentiates before birth or hatching. Its embryos develop within retained eggs before young are born.

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OvoviviparityCompared with: Some live-bearing lizards exchange nutrients with embryos, blurring older classifications based only on egg retention.