Class Myxini – hagfishes
Spelling:
Myxini. M,Y,X,I,N,I.
Taxonomic Rank: Class
Key Characteristics: Jawless, no vertebrae, keratin tooth plates, slime glands, single semicircular canal
Biological Context: Deep-sea scavengers with primitive traits. Although lacking vertebrae, they possess a cranium and are part of Craniata. Their slime defense and feeding behavior represent early adaptations to benthic scavenging.
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Infraphylum Vertebrata – vertebrates
Spelling:
Vertebrata. V,E,R,T,E,B,R,A,T,A.
Taxonomic Rank: Infraphylum
Key Characteristics: Vertebral column (or homologous structures), braincase, paired sensory organs
Biological Context: Includes all jawless and jawed vertebrates. Vertebral elements provide axial support and protect the spinal cord, enabling more active locomotion and larger body plans.
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Class Petromyzontida – lampreys
Spelling:
Petromyzontida. P,E,T,R,O,M,Y,Z,O,N,T,I,D,A.
Taxonomic Rank: Class
Key Characteristics: Jawless, oral disc with keratin teeth, cartilaginous skeleton, seven pairs of gill openings, two semicircular canals
Biological Context: Some species are parasitic, others filter-feed as larvae. Lampreys are vertebrates with rudimentary vertebrae and represent a transitional form between craniates and jawed vertebrates.