The aperture of a snail shell can have many other forms&colon; semicircular, trilobate or auriculate. Three-bladed (trilobate) arrowheads have been found in the United Arab Emirates, dated to 100BCE-150CE. The primitive dental formula is 3.1.4.3, with a trilobate fourth deciduous premolar. Snout very prominent, rounded, somewhat flattened, with trilobate horizontal outline. They possess a three-lobed caudal fin, also called a trilobate fin or a diphycercal tail.