furcula

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furcula
1. (furca) The springing organ of Collembola, which arises from the fourth or fifth abdominal segment. The furcula comprises a single basal portion, the manubrium, which gives rise to two dens, which terminate in lamellate mucrones (see MUCRO). It is bent forwards and beneath the body to engage on a ventral tube or retinaculum, which acts as a catch. When the furcula is released, the energy stored propels the animal upwards and forwards, sometimes in a tumbling fashion.

2. The wishbone of birds and some Therapoda, supposedly formed by the fusion of clavicles and interclavicle.

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