Examples of fishes that exhibit primitive vs. derived characteristics

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Feature Purpose or limitation if present Example:
Ancient		 Example:
Living fish - Inherited		 Example:
Living fish - Independently developed		 Exmple:
Other animal - Inherited

Features that predate the appearance of the first fish or craniate
Gills Absorb oxygen from water   Nearly all except for fishes with lungs None Amphibians
Notocord         Amphioxous

Primitive characteristics of jawless fishes
Lack of true jaw Limits ability to catch prey Ancestors of:
  Hagfishes
  Lampreys

Extinct:
  Ostracoderms		 Hagfishes
Lampreys		    
Lack of paried fins • Limits ability to control motion Ancestors of:
  Hagfishes
  Lampreys

Extinct:
  Ostracoderms		      
Cannot make bone, enamel, or dentin • Limits ability to protect external body,
• Limits ability to catch prey,
• Limits muscle power due to lack of strong skeleton		        
Possess electrosense     Lampreys
Sharks, Rays, Chimaeras
Lungfishes
Catfishes
   Helps locate prey

Primitive characteristics of jawed fishes
Outwardly asymmetrical tail          
Jaws derived from gill arch          
Skeleton         
Oil in liver used for buoyancy          
Dermal denticles          
Urea maintained in blood          
Pelvic fins towards back (abdominal)          

Characteristics of primitive soft-rayed fishes
Pectoral fins lower on body          
Pelvic fins towards back of body closer to tail          
Presence of adipose fin          
Cycloid scales          

Derived characteristics of spiny-rayed fishes
Pectoral fins higher on body          
Pelvic fins towards front of body closer to head          
Externally symmetrical tail          
Externally symmetrical tail          
Ctenoid scales          

Features of highly derived fishes
Flatfish shape       Flounders