| Dimensions | 12 × 14 × 3 cm |
|---|---|
| Language |
Brown cloth binding with gilt title and decoration on the spine. Gilt horse on the front board.
Though the binding is a little slack, the quality of the coloured illustrations within more than compensate.
Quadrupedalism is a form of locomotion where animals with four legs are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four legs is said to be a quadruped (from Latin quattuor for “four”, and pes, pedis for “foot”). Quadruped animals are found among both vertebrates and invertebrates. Although the words ‘quadruped’ and ‘tetrapod’ are both derived from terms meaning ‘four-footed’, they have distinct meanings. A tetrapod is any member of the taxonomic unit Tetrapoda (which is defined by descent from a specific four-limbed ancestor), whereas a quadruped actually uses four limbs for locomotion. Not all tetrapods are quadrupeds and not all entities that could be described as ‘quadrupedal’ are tetrapods. This last meaning includes certain artificial objects; almost all quadruped organisms are tetrapods (one exception is some raptorial arthropods adapted for four-footed locomotion, such as the Mantodea. Another example is brush-footed butterflies (Nymphalidae), the largest butterfly family with ~6000 species, including the well-known Monarch.
The distinction between quadrupeds and tetrapods is important in evolutionary biology, particularly in the context of tetrapods whose limbs have adapted to other roles (e.g., hands in the case of humans, wings in the case of birds and bats, and fins in the case of whales). All of these animals are tetrapods, but none are quadrupeds. Even snakes, whose limbs have become vestigial or lost entirely, are, nevertheless, tetrapods.

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