ZOO 2090 Lecture Notes - Lecture 5: Aquatic Feeding Mechanisms, Hyomandibula, Premaxilla
ZOO2090 – Fish Skeleton
Agnathan Skull:
• Visceral arches
• Branchial basket
• Without armour: premandibular arch
Placoderm Skull:
Teleost Skull:
• trend toward increased number of skull bones in actinopterygians
• Teleosts skulls are diverse with numerous bones and increased liberation between
elements maneuverable jaws and palate diverse feeding
• New bones resulted from multiplication of centers of ossification within larger bones
e.g. palatoquadrate quadrate, metapterygoid and other bones
• Many joints for a mobile skeleton
• Teleost suction feeding major innovation
o Suction is driven by volume change of the buccal cavity by opening and closing
jaws with maxilla and premaxilla
• Early gnathostomes had wide mouths, far back hinge and upper jaw fused with braincase
• Teleosts have a narrow mouth, hinged moved forward and both upper and lower jaws can
move forward independently of the braincase
• Despite the great diversity of teleosts, the basic pattern of skull bones is preserved
o Opercular
o Premaxilla
o Maxilla
Jaw Suspension: Early Fishes
1. Euautostylic: upper jaw is braced against braincase directly (hyomandibula is not
involved) ; oldest type of jaw suspension (placoderms, acanthodians)
• Jaw palatoquadrate, euautostyly and Meckel’s cartilage
2. Amphistylic: upper jaw is supported by hyomandibula and an anterior ligament
connection with braincase two primary articulation ; early sharks, some bony fish and
rhipistians
Two principle trends:
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Document Summary
Agnathan skull: visceral arches, branchial basket, without armour: premandibular arch. Two principle trends: hyostyly contact with condrocranium (otic capsule) principally through hyomandibula *modern sharks, palatoquadrate can slide forward, increasing gape, autostyly quadrate attaches chondrocranium and jaw directly, with no support from myomandibula *amphibians, reptiles, birds. Axial skeleton: vertebral column is formed by a series of repeating elements: centrum: body, neural arch: protects spinal cord, hemal arch: protects blood vessels (tail vertebrae, processes (apophyses) In early fishes and sarcopterygians, the notochord supports vertebral elements. In most fish, the vertebrae surrounds the notochord. Ligaments between neural arch (space in middle) resists buckling . Appendicular skeleton: *forms basis and constraints for tetrapod skeleton: appendages paired fins or limbs, girdles braces that support the paired appendages, anterior pectoral girdle (or shoulder, posterior pelvic girdle (or hip) Fins: three types of paired fins, lobe fins: fleshy (lungfish, fin-fold fins: broad base (cartilaginous fishes, ray fins: most bony fish.