The first crossbow fibulae, from the early 3rd century AD, has short, thin arms, no knobs, a long bow and a short foot. The later crossbow fibulae have been divided into groups by several archeologists including Keller, Prottel and Soupault. Type I, dating to the 3rd and 4th centuries, has small, simple knobs and a foot that is shorter than the bow. Type II, dating to the 4th century, has larger knobs and a foot that is approximately the same length as the bow. Type III, also dating to the 4th century, has a foot that is longer than the bow. There are several variants of the Type III based on the decoration of the foot: dotted circles, chevrons, or curlicues. Another variant, dating to the 4th and 5th centuries, the Bugelkopf type, has no transverse bar, or arms at all but retains the round knob at the head.