Complex sentence: First appearing in 1610, the Chronicon of Dexter was immensely popular along with the traditions it contained throughout the 17th century--later this was all brought into question when historians and the Catholic hierarchy in Rome declared the work a pious forgery.
Split into simpler sentences: First appearing in 1610, the Chronicon of Dexter was immensely popular along with the traditions it contained throughout the 17th century. Later, this was all brought into question when historians and the Catholic hierarchy in Rome declared the work a pious forgery.