KATHMANDU, Jan 15 (Reuters) - Nepal's Maoists took their seats in a newly created interim legislature on Monday, capping a landmark peace deal that has seen them move from guerrilla fighters to lawmakers in less than a year, witnesses said. "We have a responsibility to conduct the elections for the constituent assembly," Dev Gurung, a member of the new parliament and a Maoist negotiator, said. "We will work for that." Under a peace deal between the Maoists and mainstream political parties, the interim parliament will prepare for elections to a special assembly -- likely in June -- supposed to draft a permanent new constitution and decide the monarchy's future. Earlier on Monday, the existing House of Representatives dissolved itself after passing an interim constitution, paving the way for the new body, which now includes 83 rebel nominees, making them the second biggest party.