Which of the following is LEAST accurate regarding paleontology:

W) endothermic mammals thrived during the Cenozoic Era

X) the fossil records of birds is poor because of their thin bones and lack of teeth

Y) the mastodon was a Proboscidian mammal of the Cenozoic Era

Z) trilobites are an important index fossil of the Mesozoic Era
Z) TRIILOBITES ARE AN IMPORTANT INDEX FOSSIL OF THE MESOZOIC ERA