( ( In birds ) ( , ( ( vertebrae ( at ( ( the ( tail end ) ) ( of ( the backbone ) ) ) ) ) ( ( are ( fused ( into ( ( a structure ) ( called ( a pygostyle ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NNS birds))) (, ,) (NP (NP (NN vertebrae)) (PP (IN at) (NP (NP (DT the) (JJ tail) (NN end)) (PP (IN of) (NP (DT the) (NN backbone)))))) (VP (VBP are) (VP (VBN fused) (PP (IN into) (NP (NP (DT a) (NN structure)) (VP (VBN called) (NP (DT a) (NN pygostyle))))))) (. .)))
In birds, vertebrae at the tail end of the backbone are fused into a structure called a pygostyle.
(ROOT (S (NP (NNP Vertebrata)) (VP (VBP are) (VP (VBN characterized) (PP (IN by) (NP (NP (DT the) (NN presence)) (PP (IN of) (NP (NN backbone))))))) (. .)))
Vertebrata are characterized by the presence of backbone.