| In fish, the retrorse inclination of the myomeres forms a precursor of the differentiation between a deep and a superficial musculature of the trunk. |
| The elongated tapering spine consists of a thin outer layer of enamel-like material, an inner core of vasodentine, and retrorse serrations along the lateral margins. |
| As the bee's proboscis is inserted into the flower it pushes past the retrorse anthers to the nectar at the base of the tube. |
| In many species, the perianth parts are reduced to bristles or setae with retrorse prickle hairs. |
| The dorsal fin has a large spine with retrorse serrations behind. |
