Acanthodian Body Scales

GEOL 3213

Many Types of Primitive Paleozoic Bony Fish• Agnathans (“jawless” fish)– Since Cambrian– Ostracoderms had bony

armor plates over head• Gnathostomes– Placoderms– Chondrichthyes

(“cartilaginous”)– Acanthodians (spiny)– Osteichthyes (“bony fish”)

• Figure from Black (1988)

Five Major Categories of Fish• Agnatha• Placoderms• Chondrichthyes• Acanthodians

(Late Ord?-Late Carb.)• Osteichthyes

• Figure from Levin (1999)

Evolutionary Relationships Among Fish• Cladistic

analysis

• Cladogram

• Figure from Prothero (1998)

1

2

34 5

Preserved Squamation

• Permian• Small body scales

• Isolated acanthodian squamation on a bedding surface

Body Scales

Body scales• Isolated individual body scales in sandstone

Scales & Spines• Acanthodian

body scale (Silurian)

• Acanthodian fin spine (Climatius, Silurian)

• Palaeoniscid scale (Permian)

• Shark tooth (Carboniferous)

Typical Acanthodian Skeletal Fossils

• B = body scales• A & C = other scales• D & E = spines that

supported fins• Devonian

Scales & Spines

• Body scales• Spine

• Devonian

Scales• Devonian

Scale• Devonian• Acanthodian scale

Scales• Early Miss.

Acanthodian Scales

• Early Miss.

Acanthodian Scales• Early Miss.• Scales

Acanthodian Scales• Anterior tesserae• Late Miss.

Acanthodian Scales

Acanthodian Scales

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