Osteichthyes: Bony Fish Flashcards
when did they come about? fossil? habitats? age of fishes?
• Greek - osteo = bone, icthys= fish
• Late silurian (430 mya)- recent
○ Known only from a few fragments in silurian
• Devonian 419 mya - age of fishes
○ All major lineages, extant and extinct, coexisted
○ Both fresh water and marine habitats
bone features?
• Bony skeleton is it unique? (no!
• Other taxa with at least a partial skeleton: some ostracoderms, placoderms, acanthodians
• However, endochondral bone is unique to bony fishes
○ Dermal bone in earlier forms
homologous elements? general characteristics?
- Homologous elements - dermal bone in pectoral girdle of all groups
- Bony operculum
• Hard bony flap covering +protecting gills and aiding gill ventilation
• - Fin rays - supports fins
• Lepidotrichia: bony, bilaterally paired segmented series of flexible elements; support fins
• Dermal in origin - Swim bladder
• Develops as evagination from esophagus
• Primitively served as “lung” then as a buoyancy device - Lateral line system
• Shows homologous patterns of arrangements in groups - Internal fertilization relatively rare
- Bony operculum
two types of swim bladder? which is more advanced?
○ Physostomous
§ Retains connection to pharynx via pneumatic duct
○ Physoclistous
§ No attachment to gut - more advanced
two lineages?
- Actinopterygii (ray finned fishes)
Sarcopterygii (lobe finned fishes)
• Actinopterygian
clades? how do they differ?
• Earliest forms are the extinct paleoniscoids
• General clades: ○ Paleoniscoids (extinct) ○ Polypteriformes (bichars, reedfishes) ○ Acipenseriformes (sturgeons, paddlefishes) ○ Neopterygii (gars, bowfins, modern fish) • Clades differ in ossification; skull and pectoral girdle structure; shape of dorsal and tail fins; presence or absence of spiracle
describe paleoniscoids - scales, jaws, tail, fins
• Represent plesiomorphic states • Parallel bony fin rays • Scales: ganoid, thick, non overlapping • • Amphistylic jaw suspension through two articulations: ○ Anteriorly via a ligament ○ Posteriorly by hyomandibula Heterocercal with distinct fork
describe • Polypteriforms (bichirs and reedfish)
- Africa; freshwater
- Approx 16 species
- Mixture of distinct and primitive traits
- Up to 15 dorsal finlets each with a sharp spine
- Bone like ganoid scales
- Spiracle
- Rudimentary lungs
describe •
• Acipenseriformes (sturgeons & paddlefishes) - stergeon scales?
- Can growlarge
- Many primitive traits
- Similar to cartilaginous fishes in many ways
- Sturgeons
- Approx 25 species, anadromous and freshwater
- Largest freshwater bony fish
- No ganoid scales but plate like bony scales dorsally
- Four sensory barbels around mouth
- Benthic feeding on invertebrates
- Commercially important for eggs and flesh: caviar
- Paddlefishes
- 2 species
- Paddle like snout
- Lacks scales except for small area at the base of the tail
groups of neopterygii
- two groups of primitive neopterygians
- The gars (lepisosteiformes) and
- The bowfin (amiiformes)
- Both have more flexible jaws than paleoniscoids, but less felxible than those of more advanced neopterygians
describe •
• Neopterygii – Gars (Lepisosteiformes)
- 7 species, north and central america
- Medium to large (predatory fish with a distinctive elongated body and long jaws)
- Hard, interlocking, multilayered ganoid scales, which provide protection and are similar to the scales of many extinct paleozoic and Mesozic actinopterygians
describe • Neopterygii – Bowfin (Amiiformes)
• Only 1 species ; eastern us, freshwater
• Meduim (<1m) predatory fish
• Scales are of a single layer of cycloid scales as in teleosts,
-caudal fin is heterocercal and similar to that of more primitive fish
Neopterygii - Teleosts - dominant when? abundant or rare?
- Most abundant and diverse groups of fishes
* Dominant by late cretaceous 66 mya
general features of teleosts?
1. Modifications to jaw structure • Reduced number of jaw bones • Jaw bones joined forming a short tube • Protrusible jaw • • Reduced number of lower jaw bones 2. Lighter, thinner scales • Dermal; no enamel or ganoin • In sockets • Increased in size during growth of fish • 2 types: cycloid and ctenoid es Allows manipulation of food and creates suction 3. Homocercal caudal fin 4. Swim bladder - neutral bouyancy 5. Absence of spiracles
types of scales - teleosts
• Cycloid
○ Thin bony scale with a smooth surface and rounded margins
○ Composed of concentric rings
○
• Ctenoid
○ Thin bony scale with comb like processes (ctenii) on the posterior part and a serrate margin
sarcopterygii fin structure
- Fin structure
• Paired lateral fins supported by muscular fleshy lobe
Central axis of bony axials with radials extending in a feather-like pattern: archipterygium
describe coelacanths
• Actinistia: Coelacanths
• Coelacanth = Hollow spine; referring to hollow
spines of fins
• Mid Devonian – Recent
• Disappeared from fossil record ~135 mya
