Lec 11 part a Flashcards
Bony fish
Osteichthyes
Bones found as early as
Osteostracans, inherited by placoderms and Osteichthyans
Bone is made of
70 percent hydroxyapatite
30 percent organic materials
Bone can be
Repaired and remodeled
Features of Osteichthyans
Internal skeleton with jaw composed of premaxilla, maxilla, and dentary
Bony operculum externally covers the gills
Bony pectoral girdle that connects to skull and supports pectoral fins
Fin rays with bony spines supporting the fins
Cosmoid scales
Thin enamel and thick dentine on top of two layers of bone
Ganoid scales
Thick enamel (ganoin) on top of one/two layers of bone
Thick ganoin and thin dentine on top of one/two layers of bone
Typically found in lepisosteriforms (gars)
Bony scale
Thin layer of bones without enamel, dentine, or vascularized bone
Majority of scales are embedded in soft tissues, a condition termed imbrication
Continuous layer of integument covering all the scales
Cycloid bony scale
Exposed margin is round
Ctenoid bony scale
Exposed margin has small, comb-like projections (ctenii)
Evolutionary patterns of scales for osteichthyans
Scales towards teleost (derived group of ray-finned fishes)
Scales become thinner, likely improve swimming capacity
Loss of enamel layers
Two clades of Osteichthyes
Actinopterygii (ray-finned)
Sacopterygii (lobe-finned)
Actinopterygii (ray-finned)
Muscles positioned proximally within body wall
Sacopterygii (lobe-finned)
Muscle positioned along the skeletal elements of the fin
Diagnostic features of Actinopterygii
Forebrain developed through eversion
Tribasic paired fins
