Simplify the following text for a Grade 9 native English-speaking person.
Original: The clade was defined by Sereno in 1998 as a branch-based clade containing all Maniraptora closer to Neornithes ( which includes all the birds living in the world today ) than to Oviraptor .
Simplified: The clade was defined by Sereno in 1998 as a branch-based clade containing all Maniraptora closer to modern birds than to Oviraptor .