I. Basal Chordates and Early Vertebrates Kingdom Animalia – animals
Spelling:
Animalia . A,N,I ,M,A,L,I,A.
Taxonomic Rank: Kingdom
Key Characteristics: Multicellular, heterotrophic, eukaryotic organisms with specialized tissues and motility at some life stage
Biological Context: Encompasses all animals. Fishes belong here due to their tissue complexity, mobility, and sensory integration. This kingdom is the foundation for all vertebrate evolution.
Phylum Chordata – chordates
Spelling:
Chordata. C,H,O,R,D,A,T,A.
Taxonomic Rank: Phylum
Key Characteristics: Notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail (present at some life stage)
Biological Context: Defines the group containing all vertebrates and their closest relatives. These features support swimming, feeding, and sensory coordination in aquatic environments and are retained or modified in adult vertebrates.
Subphylum Craniata – craniates
Spelling:
Craniata. C,R,A,N,I,A,T,A.
Taxonomic Rank: Subphylum
Key Characteristics: Skull enclosing brain, paired sensory organs, neural crest cells, complex musculature
Biological Context: Includes all vertebrates and hagfishes. Craniates show the first major leap in cephalization and sensory integration, critical for active predation and environmental awareness.
Class *****Conodonta – conodonts
Spelling:
Conodonta. C,O,N,O,D,O,N,T,A.
Taxonomic Rank: Class
Key Characteristics: Tooth-like phosphatic elements, V-shaped myomeres, large paired eyes, mineralized tissues
Biological Context: Extinct jawless vertebrates. Their fossilized elements are key index fossils in stratigraphy. They represent early experimentation with mineralized feeding structures and are considered part of the vertebrate lineage due to their internal anatomy.
*"Ostracoderms" – ostracoderms
Spelling:
Ostracoderms. O,S,T,R,A,C,O,D,E,R,M,S.
Taxonomic Rank: Informal group (includes 4 extinct classes)
Key Characteristics: Bony external armor, jawless, no paired fins, cartilaginous internal skeleton, lateral line system
Biological Context: Extinct paraphyletic group of armored fishes. They pioneered dermal bone and sensory systems, laying groundwork for jawed vertebrates. Their diversity and ecological roles suggest early experimentation with benthic and filter-feeding lifestyles.