Chondrichthyes Characteristics
- General gnathostome characteristics:
- Jaws (with calcified teeth in extant groups)
- Serially arranged vertebrae
- Pectoral and pelvic girdles support paired fins
- Skeleton composed of cartilage (no bone)
- Heterocercal tail
- Placoid scales
- Claspers on male pelvic fins
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Subclass Holocephali — Chimaeras
Chimaera, Hydrolagus sp.;
Order Chimaeriformes
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Spotted Ratfish, Hydrolagus colliei;
Order Chimaeriformes
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Characteristics
- Enlarged head with beak-like teeth
- Mostly scale-less body
- All but one pair of gill slits covered
- 2 dorsal fins
- Marine; mostly deep water
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Subclass Elasmobranchi — Sharks & Rays
Characteristics
- Retain many primitive gnathostome characteristics
- Body covered in scales
- 5-7 externally visible gill slits
- Ampullae of Lorenzini
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Order Rajiformes
- Skates and rays (539 species)
- Body flattened with enlarged pectoral fin fused to head
- Gill slits on ventral surface
- Eyes located dorsally
- Lack anal fin
- Most are bottom dwellers; some occur in fresh water
- This order is sometimes split into several separate orders
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Southern Sting-Ray, Dasyatis americana; Belize
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Ocellated Sting-Ray, Potamotrygon motoro
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Spotted Eagle Ray, Myliobatis aquila
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Lesser Guitarfish, Rhinobatos annulatus
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Leopard Whipray, Himantura undulata, ventral surface
See also labeled photo.
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Manta Ray, Manta birostris: The world's largest ray, a plankton filter feeder
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Shark Ray, Rhina ancylostoma
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Order Carcharhiniformes
- Ground sharks (217 species)
- Most species-rich order of sharks
- Contains most of the familiar species (such as sand sharks, leopard sharks and hammerheads)
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Sandbar Shark, Carcharhinus plumbeus
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Gray Smoothhound Shark, Mustelus californicus
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Great Hammerhead, Sphyrna mokarran
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Black-tipped Reef Shark, Carcharhinus melanopterus
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Order Orectolobiformes
- Carpet sharks (32 species)
- Mouth is located anterior to eyes
- Nasoral grooves with barbels
- Most are slow moving bottom dwellers
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Nurse Shark, Ginglymostoma cirratum; Belize
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Ornate Wobbegong Shark, Orectolobus ornatus
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Zebra Shark, Stegostoma fasciatum
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Whale Shark, Rhincodon typus; the largest extant fish is a filter feeder of plankton
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Order Squaliformes
- Dogfish sharks (98 species)
- 2 dorsal fins, each with a spine
- Lack anal fin
- Tend to be bottom-dwelling
- All are ovoviviparous
- See also dissection page.
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Dogfish, Squalus sp.; preserved specimen
See also labeled photo.
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Other Shark Orders
- In addition to those shown above, 5-7 other orders of sharks are usually recognized
- You do not need to learn any of these orders
- None of these orders contain more than 20 species
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Sand Tiger Shark, Carcharias taurus;
(Order Lamniformes)
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Largetooth Sawfish, Pristis microdon;
(Order Pristiformes)
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Placoderms
Dunkleosteus; Devonian; North America and Europe; 10m long
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Bothriolepis; Devonian; Worldwide; 30cm long
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Characteristics
- Placoderms are a separate clade of early gnathostomes
- Bony plates on head and anterior body
- Well-developed jaws, but lacked teeth
- 2 pairs of paired fins
- Most were probably bottom dwellers
- Lived from Silurian to Devonian (430-360 mya)
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