One of the best ways to really understand the diversity of sharks species is to learn how scientists classify them. This classification system is known as taxonomy. Taxonomy breaks sharks down by their evolutionary traits into seven sub-categories: Kingdom, Phylum, Class, Order, Family, Genus, and Species. Understanding these subcategories is the best way to learn about the types of sharks. So here is a simple guide to understanding different shark classifications:
Kingdom
Kingdom is the highest taxonomic rank and breaks all living creatures down basically into plants, fungus, bacteria, and animals Sharks are an animal, so they are always classified as “animalia.”
Phylum
Phylum is the next classification that breaks animals into 35 categories. Sharks are considered the phyla “Chordates” because they are vertebrates with dorsal nerve cord that connects the brain to the muscles and organs, and gill slits that connect the throat to the neck.
Class
Class is where taxonomic classifications begin to get a lot more specific. All sharks are Chondrichthyes which are defined as cartilaginous fish. There are two subclasses of chondrichthyes: Elasmobranchii and Holocephali. Elasmobranchs include sharks, rays, skates, and sawfish and Holocephali are chimaeras/ghost sharks. The difference between these two subclass is the structure of their gills and how they grow in the embryo. Elasmobranchs have five to seven external gill slits with no gill cover, while Holocephali has four gill slits with a gill cover. These gills are develop during their embryonic phase and grow differently in the womb.
Order
The next level of classification is order. Elasmobranchii break down into eight orders of shark all distinguished by their unique biological traits:
- Carcharhiniformes (Ground Sharks): Ground Sharks have five gill slits, two spineless dorsal fins, an anal fin, nictitating eyelids, a mouth located behind their eyes, and a long snout.
- Heterodontiformes (Bullhead Sharks): Bullhead Sharks have five gill slits, two dorsal fins with spines, an anal fin, no nictitating eyelid, a mouth underneath their head, and a stump snout.
- Hexanchiformes (Frilled/Cow Sharks): Frill Sharks and Cow Sharks have six to seven gill slits on the sides of the head, one spineless dorsal fin, an anal fin, no nictitating eyelid, a mouth at the front bottom of their head, and a blunt snout
- Lamniformes (Mackerel Sharks): Mackerel Sharks have five gill slits, two spineless dorsal fins, an anal fin, no nictitating eyelids, a mouth behind the eyes, and a pointed snout.
- Orectolobiformes (Carpet Sharks): Carpet Sharks have five gill slits, two spineless dorsal fins, an anal fin, no nictitating eyelids, a mouth in front of their eyes, and short snouts.
- Pristiophoriformes (Sawsharks): Sawsharks have five to six gill slits, two spineless dorsal fins, no anal fin, no nictitating eyelid, a mouth underneath the head, and a long snout.
- Squaliformes (Dogfish Sharks): Dogfish Sharks have five gill slits, two spineless dorsal fins, no anal fin, no nictitating membrane, a mouth located underneath the head, and a short snout.
- Squatiniformes (Angel Sharks): Angel Sharks have five gill slits, two spineless dorsal fins, no anal fin, no nictitating eyelid, a mouth at front of the head, and a short snout.
As for the order of Holocephali, the only class that is still alive on the planet today is Chimaeriformes which all have the same biological traits.
Family, Genus, and Species
These orders are then further broken down into family, genus, and species. These categories are based on their environment, their shared physical traits, and their prey and hunting behaviors. Since this is where it begins to get very complicated because there are over 440 known species of sharks, it is better to include them together to really understand shark taxonomy:
Carcharhiniformes are the largest order of sharks and has 227 species:
- Carcharhinidae (Requiem Sharks): 12 genus and 48 species of sharks. including Dusky Sharks, Bull Sharks, Ganges Sharks, and Broadfin Sharks.
- Hemigaleidae (Weasel Sharks): 1 genus and 5 species that are all types of Weasel Sharks.
- Leptochariisae (Barbelled Houndsharks): 1 genus and 1 species.
- Proscyllisae (Finback Catsharks): 1 genus and 6 species.
- Pseudotriakidae (False Catshark): 1 genus and 1 species.
- Scyliorhinidae (Catsharks): 1 genus and 89 species.
- Sphyrnidae (Hammerhead Sharks): 2 genus and 9 species.
- Triakidae (Houndsharks): 1 genus and 34 species including Whiskery Sharks, Leopard Shards, and Smooth-Hound Sharks.
Heterodontiformes are generally only found in the Indian and Pacific Oceans and has 8 total species:
- Heterodontus (Bullhead and Horn Sharks) includes the Horn Shark, Crested Bullhead Shark, Mexican Hornshark, Port Jackson Shark, Galapagos Bullhead Shark, Whitespotted Bullhead Shark, and Zebra Bullhead Shark.
Hexanchiformes are the most ancient order of sharks has 6 total species:
- Chlamydoselachidae (Frilled Sharks): 1 one genus and 2 species.
- Hexanchidae (Cow Sharks): 3 genus and 4 known species, the Bluntnose Sixgill Shark, Bigeye Sixgill Shark, Sharpnose Sevengill Shark, and Broadnose Sevengill Shark.
Lamniformes are probably the best recognized shark and has 17 different species:
- Alopias (Thresher Sharks): 1 genus and 3 species.
- Cetorhinidae (Basking Shark): 1 genus and 1 species.
- Lamnidae (Mackerel Sharks): 3 genus and 5 species including Great White Sharks, Mako Sharks, and Porbeagles.
- Megachasmidae (Megamouth Shark): 1 genus and 1 species.
- Mitsukurina (Goblin Shark): 1 genus and 1 species.
- Odontaspididae (Sandtiger Sharks): 1 genus and 4 species.
- Pseudocarcharias (Crocodile shark): 1 genus and 1 species.
Orectolobiformes has 39 species are generally bottom dwellers but also include the largest shark in the ocean:
- Brachaelurus (Blind Sharks): 1 genus and 2 species.
- Ginglymostoma (Nurse Sharks): 1 genus and 3 species.
- Hemiscyllidae (Bamboosharks): 1 genus and 11 species.
- Orectolobidae (Wobbegongs): 1 genus and 6 species.
- Parascyllidae (Collared Carpetsharks): 1 genus and 7 species.
- Stegostomatidae (Zebra Shark): 1 genus and 1 species.
- Rhincodon (Whale Shark): 1 genus and 1 species.
Pristiophoriformes is a singular order with one family that just includes 2 genus and 7 species of Sawsharks.
Squaliformes are generally the smallest order of sharks and has 126 species:
- Squantinidae (Dogfish Sharks): 1 genus and 67 species including Lanternsharks, the Cookie Cutter Shark, and and Spiny Dogfish.
- Echinorhinidae (Bramble Sharks): 1 genus and 2 species.
- Oxynotidae (Roughsharks): 1 genus and 4 species.
Squatiniformes are also a singular order of sharks that contains 1 family, 1 genus, and 12 species of Angel Sharks.
Though narrowing the types of sharks down from Kingdom to Species can be a tall order, if you generally understand the basic biological traits and the taxonomic classification model, you can understand the biology of sharks just by their names. If you study this basic guide you can then get into more detail and eventually learn every single one of the types of shark on the planet.
