Virtual Museum: Cartilagenous Fishes

There has been a lot of debate about where the Acanthodians fit in the fish phylogeny, but recent studies suggest they are ancestors to the Chondrichthyes (cartilagenous fishes). They lacked bony armor plates but had large scales (which include layers of bone-like material) and spines on their fins.

Their internal skeleton was cartilagenous, so fossils showing the entire animal, such as this one of Acanthodes bridgei, are rare.

Taxonomy: Acanthodii; Acanthodiformes; Acanthodidae

Hamilton Quarry, Greenwood Co., KS

Carboniferous Period, Pennsylvanian Epoch

Black Hills Institute Museum, South Dakota

This fossil of Diplacanthus striatus shows the numerous well-developed spines of this group.

Taxonomy: Acanthodii; Diplacanthiformes; Diplacanthidae

Scotland

Devonian Period

Chicago Field Museum

Fossil of Cheiracanthus sp.

Taxonomy: Acanthodii; Acanthodiformes; Cheiracanthidae

Scotland

Devonian Period

Chicago Field Museum

Acanthodes bridgei.

Taxonomy: Acanthodii; Ischnacanthiformes; Ischnacanthidae

Scotland

Devonian Period

Chicago Field Museum

Life model of Acanthodes sp.

Taxonomy: Acanthodii; Acanthodiformes; Acanthodidae

Carboniferous to Permian Periods, 409-284 Ma

Museum of Ancient Life, Utah

Chondrichthyes means "cartilage fish" and reflects their cartilagenous skeleton (jaws can become mineralized but this is not true bone). Unlike more primitive fish, they lack the bony dermal armor plates, so except for their teeth, they rarely fossilize except under rare conditions. There are two major clades of the Chondrichthyes, the elasmobranchi (sharks & skates, covered below) and the Holocephali. This latter group has a few surviving members, the deep-sea chimaeras or ratfishes, but a more extensive fossil record.

Echinochimera melton is one such extinct member of the Holocephali.

Taxonomy: Chondrichthyes; Holocephali; Chimaeriformes; Echinochimaeridae

Central Montana

Carboniferous Period, Mississippian Epoch, Bear Gulch Limestone, 320 Ma

Museum of the Rockies, Montana

Falcatus falcatus is a strange, primitive shark; the male's dorsal fin forms a forward-pointing prong that is hooked through the female's jaw during mating.

Taxonomy: Chondrichthyes; Holocephali; Symmoriida; Falcatidae

Fergus Co., Montana

Carboniferous Period, Mississippian Epoch, Bear Gulch Limestone, 320 Ma

Black Hills Institute Museum, South Dakota

Symmorium reniforme, a large shark-like holocephalan, and may be the female of Stethacanthus (see model below).

Taxonomy: Chondrichthyes; Holocephali; Symmoriida; Symmoriidae

Indiana

Carboniferous Period

Chicago Field Museum

Orodus greggi is another large shark-like holocephalan, reaching up to 4 m long.

Taxonomy: Chondrichthyes; Holocephali; Orodontida; Orodontidae

Indiana

Carboniferous Period

Chicago Field Museum

The fossil tooth whorl of Helicoprion ferrieri. The teeth are never shed, so they roll up in a whorl as new teeth grow in, so that the oldest teeth (when the shark was young) are in the center of the whorl. The whorl sits in the lower jaw and fits into a V-shaped groove in the toothless upper jaw, and may have functioned to extract molluscs from their shell.

Taxonomy: Chondrichthyes; Holocephali; Eugeneodontida; Helicoprionidae

Glass Mountains, Texas

Permian Period

Chicago Field Museum

Life models of Belantsea montana and two small bradydont sharks, Harpagofututor volsellorhinus.

Taxonomy: Chondrichthyes; Holocephali; Petalodontiformes (Belantsea) and Holocephali; Chondrenchelyiformes (bradydonts)

Carboniferous Period

Arizona Museum of Natural History

Life model of Falcatus facatus (the unicorn shark). This is a male; females lack the spine-like dorsal fin.

Taxonomy: Chondrichthyes; Holocephali; Symmoriida

Carboniferous Period, Late Mississippian Epoch, 320 Ma; Montana

Museum of the Rockies, Montana

Life models of Echinochimera meltoni male and two smaller females.

Taxonomy: Chondrichthyes; Holocephali; Chimaeriformes

Carboniferous Period, Late Mississippian Epoch, 320 Ma; Montana

Museum of the Rockies, Montana

Life model of Cladoselache sp.

Taxonomy: Chondrichthyes; Holocephali; Cladoselachiformes

Late Devonian Period

Museum of Ancient Life, Utah

Life model of Symmorium sp. (may be a female Stethacanthus).

Taxonomy: Chondrichthyes; Holocephali; Symmoriida

Carboniferous Period, Pennsylvanian Epoch

Arizona Museum of Natural History

Life models of Stethacanthus, the "ironing board shark." The female is in the foreground and the male, with his distinctive dorsal fin, is in the back.

Taxonomy: Chondrichthyes; Holocephali; Symmoriida; Symmoriidae

Carboniferous Period, Pennsylvanian Epoch, 320 Ma; Montana

Wyoming Dinosaur Center

The Elasmobranchii include the modern sharks, rays, and skates, as well as some primitive forms that are neither true sharks or rays.

This fossil is Xenacanthus sp., a very primitive 'shark' with a prominent dorsal spine.

Taxonomy: Chondrichthyes; Elasmobranchii; Xenacanthida; Orthacanthidae

Germany

Early Permian Period

Wyoming Dinosaur Center

Fossil of Orthocanthus sp. Its cartilage has been replaced by a white mineral.

Taxonomy: Chondrichthyes; Elasmobranchii; Xenacanthida; Orthacanthidae

Pfalz, Germany

Permian Period, 280 Ma

Tucson Gem & Mineral Show

This juvenile Bandringa rayi had a long, flat snout similar to that of a modern paddlefish. It is preserved in an ironstone concretion.

Taxonomy: Chondrichthyes; Elasmobranchii; Bandringidae

Mazon Creek, IL

Carboniferous Period

Chicago Field Museum

The clade Selachii includes all of the modern (true) sharks.

Cat shark, Scyliorhinus sp. This genus persists to this day.

Taxonomy: Chondrichthyes; Elasmobranchii; Selachii; Carcharhiniformes; Scyliorhinidae

Lebanon

Late Cretaceous Period, Cenomanian Stage

Black Hills Institute Museum, South Dakota

Cantioscyllium decipiens is a member of the nurse & carpet shark group.

Taxonomy: Chondrichthyes; Elasmobranchii; Selachii; Orectolobiformes; Ginglymostomatidae

Hjoula, Lebanon

Late Cretaceous Period, Cenomanian Stage, 110 Ma

Tucson Gem & Mineral Show

The clade Batoidea includes all of the modern rays and skates, with broad pectoral fins and flat bodies.

A guitarfish (a kind of ray), Rhinobatos sp., virtually unchanged from moderns species belonging to the same genus.

Taxonomy: Chondrichthyes; Elasmobranchii; Batoidea; Rajiformes; Rhinobatidae

Solnhofen Limestone, Germany

Late Jurassic Period, 150 Ma

Wyoming Dinosaur Center

Another guitarfish, Rhinobatos maronita.

Taxonomy: Chondrichthyes; Elasmobranchii; Batoidea; Rajiformes; Rhinobatidae

Lebanon

Late Cretaceous Period, 98 Ma

Museum of Ancient Life

Pararaja expansa ray.

Taxonomy: Chondrichthyes; Elasmobranchii; Batoidea; Rajiformes; Rajidae

Lebanon

Late Cretaceous Period, Cenomanian Stage

Black Hills Institute Museum, South Dakota

The sting-ray-like skate Cyclobatis major.

Taxonomy: Chondrichthyes; Elasmobranchii; Batoidea; Rajiformes; Cyclobatidae

Lebanon

Late Cretaceous Period, Cenomanian Stage, 98 Ma

Museum of Ancient Life, Utah

A sting-ray, Heliobatis radians.

Taxonomy: Chondrichthyes; Elasmobranchii; Batoidea; Myliobatiformes; Dasyatidae

Wyoming

Early Eocene Epoch, Green River Formation, 50 Ma

Wyoming Dinosaur Center

Another Heliobatis radians sting-ray.

Taxonomy: Chondrichthyes; Elasmobranchii; Batoidea; Myliobatiformes; Dasyatidae

Wyoming

Early Eocene Epoch, Green River Formation, 50 Ma

Wyoming Dinosaur Center

A pregnant stingray, Asterotrygon maloneyi with one embryo.

Taxonomy: Chondrichthyes; Elasmobranchii; Batoidea; Myliobatiformes; Urolophidae

Fossil Lake, Wyoming

Early Eocene Epoch, Green River Formation, 50 Ma

Chicago Field Museum

Micropristis solomonis sawfish had an elongated rostrum (snout) lined with tiny teeth that were used to hunt small fish.

Taxonomy: Chondrichthyes; Elasmobranchii; Batoidea; Rhinopristiformes; Rhinobatidae

Hadjula, Lebanon

Late Cretaceous Period, Cenomanian Stage

Black Hills Institute Museum, South Dakota