"Extra" in the sense that these beliefs were kept by the Jews but not found in the (39 book) old testament, but nevertheless recorded in the new testament books.
And coming he dwelt in a city called Nazareth: that it might be fulfilled which was said by prophets: That he shall be called a Nazarene. Matthew 2:23
Then Jesus spoke to the multitudes and to his disciples, Saying: The scribes and the Pharisees have sitten on the chair of Moses. Matthew 23:1-2
When Michael the archangel, disputing with the devil, contended about the body of Moses, he durst not bring against him the judgment of railing speech, but said: The Lord command thee. Jude 1:9
Now as Jannes and Mambres resisted Moses, so these also resist the truth, men corrupted in mind, reprobate concerning the faith. 2 Timothy 3:8
Elias was a man passible like unto us: and with prayer he prayed that it might not rain upon the earth, and it rained not for three years and six months. James 5:17