Shiva, as Nataraja, performs the energetic tandava dance which represents the dynamism in the cosmos. Throughout this dance Shiva remains the subduer of Apasmara - personification of ignorance and darkness.
Besides the famous Nataraja pose there are other poses of Shiva as well which are a part of his dance. This statue is one of them.
Shiva sports the usual Damaru (drum) and Kaalagni (flame cup) in his two upper hands. One of his lower hand is raised in Abhaya Mudra (assurance) and the other drops loosely. If you look closely at this hand it will resemble the profile of an elephant from forehead to trunk tip. This is known as Gaja Hasta Mudra.
He dances on Apasmara. Shiva's legs bent at knees form a square and this pose is therefore known as Chatura Tandava Murti.