Taxonomy, Morphology & Locomotion

Taxonomy

Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Lamniformes
Family: Alopiidae
Genus: Alopias
Species: Alopias vulpinus
_{(Ichsan et al. 2021)}

^{_{(1. Image from shutterstock)}}

Morphology & Locomotion

One of the most notable things about the Alopias genus is the long whip-like upper caudal fin lobe that extends from their body. This tail can sometimes be as long as their body. With relatively large pectoral and anal fins, and a smaller singular dorsal fin, the fin types in the Alopias genus are truly unique (Knaub et al. 2024).

^{_{(2. Image from Atlantis Dive Resorts)}}

Compared to the common thresher, Alopias vulpinus; big eye threshers or, Alopias superciliosus, are distinguished by their large eyes while pelagic threshers, Alopias pelagicus, are harder to tell the difference with. Pelagic threshers have dark patches of skin above their pectoral fins, lateral cupselts on their teeth, as well as defined labial furrows around their mouth while common threshers do not have any of these features (Ichsan et al. 2021).

A common threshers caudal fin can be used to whip prey over their head or to their side and it is a very different motion from the oscillatory movement used for swimming. Due to the increased stress on the back vertebra when this is happening thresher sharks have different cartilaginous morphology in their tail in comparison to the rest of their body. Posterior vertebrae are smaller, shorter and have more lamellae than anterior vertebrae. This increased lamellae is thought to increase the amount of minerals in the centra of the vertebrae to support the oscillatory motion of swimming, as well as provide support for the body during tail whipping events. Thresher sharks are also seen to have less stiffness in their vertebral centra compared to other lamniformes or carcharhiniformes (Knaub et al. 2024).

Although they do have a thunniform swimming type the caudal fin of thresher sharks means their body is not as streamlined. Which is unlike their lamniformes shark counterparts (Donley et al. 2012).