Major Groups of Extant Vertebrates
Anamniotes: not monophyletic, generally aquation (fish and amphibians)
Amniotes: monophyletic, generally terrestrial (reptiles, birds, mammals)
Anamniotes Include…
Myxiniformes: hagfishes
Petromycontiformes: lampreys
- Extant and extinct jawless fish
Gnathostomata (vertebrates with jaws)
Gnathostome fishes
Chondrichthyes:
- sharks, rays, skates, and ratfishes
- cartilaginous skeletons
- Neoselachii: extant sharks, skates and rays
- Holocephalii: ratfishes (chimaeras, rabbitfish)
Osteichthyes
bony fishes, but includes all the rest of vertebrates (tetrapods)
Actinopterygii and Sarcopterygii
Actinopterygii
Osteichthyes (bony fishes)
Vast majority of vertebrates = “fish”
Fresh, marine, brackish, hypersaline
oceanic trenches to alpine lakes
32 000 names species
95% Teleostei
Sarcopterygii
Osteichthyes (boney fish)
8 spp. of extant fish
- 2 coelacanths, 4 lungfish
The rest are tetrapods (anamniotes = amphibians; amniotes = reptimes, birds and mammals)
Urodela
salamanders
Amphibians
Within Sarcopterygii
Fossil forms
Lissamphibia:
-Urodela (Salamanders
-Anura (frogs)
-Gymnophiona (caecilians)
dual lifestyle with aquatic larvae, terrestrial adult
Anura
frogs
Gymnophiona
caecilians
Amniota
The rest of tetrapods.
Unique egg with layers from embryo that include amnion
More terrestial with modifications to deal with terrestrial enviro
Amniota modications to deal with terrestrial environemtn
lungs, kidneys to conserve water, increased chambers of heart, thermoregulation
Taxonomy vs. Systematics
Taxonomy: disciple of naming organisms and placing them into a classification
Systematics: disciple of discovering relationships among organisms and organizing them based on those relationships (creating classifications)
Early Classifications
Good vs. bad (edible vs. posionous)
Linnaean System Specified Ranks
Kingdom
Phylum
Class
Order
Family
Genus
Species
King Phillip Can Order Family Ghouls Somehow
2 Problems with Linnaean System
- Non-equivalence of ranks across taxonomic groups (a family of fishes may contain a single spp or more than 1400 spp)
- Not enough ranks to accommodate every taxon that biologists might want to discuss
Classification vs. determining relationships
Classifications are applied to organisms AFTER their relationships have been established
4 Key Principles of Phylogenetic Systematics (Cladistics)
- Evolutionary relationships are presented by a cladogram of diverging branches.
- Supraspecific taxa are groups of closely related spices, correspond to major branches
- The tree is built based on shared derived features
- Ancestors are never specified, but always treated as hypothetical entities corresponding to nodes (branching points)
Apomorphy
Derived feature (newly evolved within the lineage)
Plesiomorphy
Primitive (ancestral) feature
Natural Group
Monophyletic lineage
Synapomorphy/sympleisomorphy
Shared derived or primitive characteristics used to recognize monophyletic groups
Polytomy
More than two branches arise from a node on a cladogram
Unnatural groups
Paraphyletic (multiple lineages share common ancestor but doesn’t include all descendants) or polyphyletic (don’t share ancestor) linages
