Catriona states that Dracula's name means "Dragon" and that he founded a warrior-clan in the 13th century called the Dracul. In fact, "Dragon" was his father's name (Vlad Dracul), and "Dracula" means "Son of the Dragon." "Dracula" was a member of the Order of the Dragon, but during the 15th century (not the 13th), and he was not the order's founder. The Order of the Dragon was founded in 1408 by the King of Hungary.
Dr. Sweet refers to a vampire bat as being from the desmodus rotundus species. However, that kind of bat was only named as such in 1901, by Oldfield Thomas.
Since the series' action is placed before that, Dr. Sweet should have referred to the bat as Phyllostoma rotundum.