Cephalaspidomorphi

• Domain Eukarya 
• Kingdom Animalia
• Phylum Chordata
• Subphylum Vertebrata
• Class Cephalaspidomorphi

characteristics of cephalaspidomorphi

• There are TWO different ways to classify:
• 1. including any jawless fish with a dorsal nostril. 
•      Including fish with an armored head (osteostraci) AND lampreys.
• 2. only including jawless fish with head armor (osteostraci).

Evolutionary history

• Lampreys are similar to jawless fish with a head shield in many ways.
• BUT, new evidence suggests they got this way through convergent evolution. 
• Convergent evolution is the process whereby distantly related organisms  
•   evolve similar characteristics independently.
• They are likely the ancestors of jawed fish

basic characteristics

• Cephalaspidomorphi are jawless fish.
• They are vertebrates with a braincase.

Armored fish (osteostraci)

• Osteostraci are all extinct. 
• They are a group of cephalaspidomorphi noted for their head armor.
• Developed paired fins and advanced cranial structure.

Cephalaspis, an Osteostracite

Lampreys, Cephalaspidiomophids

• Lampreys are the only extant species of cephalaspidiomorphi.
• "Lamprey" means "stone-licker"
• Reproduce using external fertilization (eggs fertilized outside body).
• Do NOT have paired fins.
• Some are parasitic; others are free-living.

lampetra fluviatillis

Petromyzon Marinus

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