Wyvern is made between the two. Since the sixteenth century, in English, Scottish, and Irish heraldry, the key difference has been that a wyvern has two legs, whereas a dragon has four. However, this distinction is not commonly observed in the heraldry of other European countries, where two-legged dragon-like creatures being called dragons is entirely acceptable. In the modern fantasy genre, there is little differentiation between dragons and wyverns, with two-legged, magical reptilian creatures all likely to be referred to as "dragons" without any differentiation between types. Wyverns, when present as creatures distinct from dragons, tend to appear as less magical
Westland Wyvern (and equally troubled) Blackburn Firebrand. Several second-line squadrons also received Wyverns around this time. Total production was 127 airframes with 124 aircraft completed, as the last three Eagle piston-engined airframes, VR138, -139, and -140, were never completed. The first carrier trials were carried out by the first pre-production Wyvern TF.2 aboard on 21 June 1950. Despite this, when the Wyvern S.4 entered service with 813 Naval Air Squadron in May 1953, it had not obtained clearance for carrier operations, this being obtained only in April 1954. The Wyvern was in service with the Fleet Air Arm from 1954 to 1958.