Fish Diversity: Osteichthyes, Part 1 Marine Vertebrates: Lecture 2

Fish phylogeny Lungs & lung derivatives

Class Osteichthyes Major features Lung and lung derivatives Ventral, with ventral connection to gut: Remained this way for tetrapod ancesters Dorsal, with ventral connection to gut Early ray-finned fishes Dorsal, with dorsal connection to gut Some ray-finned fishes Physostomous: connection with gut (as seen above) Physoclistous: no connection with gut

Class Osteichthyes Major features Bone: at least some ossification… Lepidotrichia: support of soft rays of fins  segmented and flexible (compare to Ceratotrichia) Scales GanoidCycloidCtenoid

Focus: Subclass Sarcopterygii Lobe-finned fishes Fins linked to pelvic girdle

Focus: Subclass Sarcopterygii Lobe-finned fishes Overview  Similarities with tetrapods Fins articulated with pelvic girdle Jaw and tooth structure similar  Groups Dipnomorpha (lungfishes): freshwater! Actinista (Coelacanths)

Focus: Actinista: Coelacanths Discovery Features: skeleton, osmotic regulation, swim bladder, reproduction

Coelacanth behavior Photo: M. Erdmann

Subclass Actinopterygii Ray-finned fishes

Infraclass Chondrostei Sturgeon

Five rows of bony* scales (ganoid or “rhomboid”)  Secondarily cartilagenous skeletons Some with spiracles/spiracle remnants* Spiral valve present* Heterocercal tail* No teeth (so how do they eat?) Sensory: barbels, electrical sense Long, slow growth; high fecundity Caviar = sturgeon roe

Infraclass Teleostii Most “modern” Actinopterygii are teleosts  23,681 species Derived characters  Bone in scales reduced  No spiracles  Homocercal tail  Other skeletal aspects…