According to Official Guinness Records,
The largest gathering of skeletons is 2,018 and was achieved by Jokers' Masquerade (UK) at Swansea University, Swansea, UK, on 8 October 2011. The event was held in Swansea University and was organised by Jokers Masquerade, a fancy dress company.
For a complete list of 2011 records, please visit 2011 Guinness Records in United Kingdom.