Former constellation

Former constellations are old historical western constellations that for various reasons are no longer widely recognised or are not officially recognised by the International Astronomical Union (IAU). Prior to 1930, many of these defunct constellations were traditional in one or more countries or cultures. Some only lasted decades but others were referred to over many centuries. All are now recognised only for having classical or historical value. Many former constellations had complex Latinised names after objects, people, or mythological or zoological creatures. Others with unwieldy names were shortened for convenience. For example, Scutum Sobiescianum was reduced to Scutum, Mons Mensae to Mensa, and Apparatus Sculptoris to Sculptor.
Some of the northern sky's former constellations were placed in the less populated regions between the traditional brighter constellations just to fill gaps. In the southern skies, new constellations were often created from about the 15th century by voyagers who began journeying south of the equator. European countries like England, France, the Netherlands, German or Italian states, etc., often supported and popularised their own constellation outlines. In some cases, different constellations occupied overlapping areas and included the same stars. These former constellations are often found in older books, star charts or star catalogues. 
The eighty-eight modern constellation names and boundaries were standardised by Eugene Delporte for the IAU in 1930, under an international agreement, removing any possible astronomical ambiguities between astronomers from different countries. Nearly all former or defunct constellations differ in their designated boundaries inasmuch as they have outlines that do not follow the exact lines of right ascension and declination.
Noteworthy former constellations.
Argo Navis.
Argo Navis is the only constellation from Ptolemy's original list of 48 constellations that is no longer officially recognized. Due to its large size, it was split into three constellations by Nicolas Louis de Lacaille: Carina (the keel), Puppis (the poop deck), and Vela (the sails). The new constellations were introduced in the 1763 star catalog "Coelum Australe Stelliferum", which was published soon after de Lacaille's death.
Quadrans Muralis.
Quadrans Muralis was originally created in 1795, placed in the northern skies between the still-accepted constellations Boötes and Draco. The Quadrantids meteor shower is named after this former constellation.