Cartilaginous Fishes
Class Chondrichthyes
• Cartilaginous endoskeleton - often calcified (never ossified) • Neurocranium (chondrocranium) lacks structure - one solid mass of cartilage • No swimbladder • High concentration of urea in blood helps osmoregulation to maintain water balance • Placoid scales • Ceratotrichia • Embryo encapsulated in leather • Claspers on pelvic fin • Internal fertilization
Class Chondrichthyes Subclass Holocephali Subclass Elasmobranchii †Cohort Paleoselachii Cohort Euselachi
• Cartilaginous fish classification • Cl, SubCl, SubCl, Co,Co
Swimbladder
• Chamber of air that are inside fish bodies that allows them to be neutrally buoyant in water
Phylum Chordata Subphylum Vertebrata Superclass Agnatha Superclass Gnathostomata †Class Placodermi Class Chondrichthyes †Class Acanthodii Class Actinopterygii Class Sarcopterygii
• Classification of Gnathostomata • P, SubP, SupCl, SupCl, C, C, C, C, C
Hyostylic Jaw Suspension
• Jaw suspension in Sharks, rays, and most bony fishes • Otic process and contact lost • Upper jaw loses major direct connection with the chondrocranium • Upper and lower jaws are supported solely by the hyoid arch
Amphistylic Jaw Suspension
• Jaw suspension in primitive sharks • Upper jaw firmly attached to chondrocranium • Hyoid arch attached to chondocranium and lower jaw at otic and orbital processes • Hyoid arch involved in suspension of palatoquadrate and Meckels cartilage
Squaline Oil
• Shark livers are large and contain ________ ___ that helps buoy the shark in water
Ceratotrichia
• Soft, unsegmented fin supports, epidermal origin • Like a keratinized epidermis
Subclass Holocephali
• Subclass of the superorder Rajomorphii • Four gill openings covered by an operculum • Upper jaw fused to cranium (holostylic) • Fused platelike teeth • Persistent notochord • No spiracle or cloaca • Pelvic & head claspers present • Spine at origin of first dorsal • Two Superorders: †Superorder Paraselachimorphi Superorder Holocephalimorphi
†Superorder Paraselachimorphi
• Superorder the Subclass Holocephali • Fossil holocephalans are known as far back as the upper Devonian (bradydonts) • Iniopterygiformes ("Nape Wing Forms") is an extinct order of chimera-like cartilaginous fish that lived from Devonian to Carbon....
Superorder Holocephalimorphi
• Superorder the Subclass Holocephali • Ratfishes, Chimeras • Long tapering body and tapering tail - chimeraform body plan: reduces drag • Pelagic, deep water fishes
Cohort Euselachii
• This Cohort of the Subclass Elasmobranchii • Extinct & extant species: Ctenacanths, Xenacanths, Hybodonts • Many with subterminal mouths • Transition of tooth & jaw suspension type: • Primitive cladodont & hybodont to modern types • Amphistylic to hyostylic
†Cohort Paleoselachii
• This Cohort of the Subclass Elasmobranchii • Lacked claspers & an anal fin • Mouth terminal, not subterminal as in most other lineages • Heavy dorsal fin spines (most) • Amphistylic jaw suspension • Cladodont teeth type
Superorder Squalomorphi
• This Superorder includes sharks as different in form as the Squaliformes (dogfish sharks), Hexanchiformes (six gilled sharks), & Pristiophoriformes (saw sharks) • Order Squaliformes • Order Hexanchiformes • Order Pristiophoriformes
Superorder Galeomorphii
• This Superorder includes sharks... • "typical" pelagic, predatory sharks • Four orders: Order Lamniformes "mackerel sharks" Order Carchariniformes "requiem sharks" Order Orectolobiformes "carpet sharks" Order Heterodondiformes "horn sharks"
Subclass Elasmobranchii
• This subclass... • 5-7 gill slits • Spiracle • Hyostylic or amphistylic jaws • Dorsal fin(s) & spines (if present) rigid • No gas bladder • Vertebral centra replace notochord, often calcified • Multiple rows of teeth with rapid tooth replacement
Superorder Rajomorphii (Batoidea)
• This superorder of the subclass Elasmobranchii • Skate, Benthic Ray, Sawfishes, Guitarfish • Dentition is flattened, molariform for crushing invertebrates, replacement teeth in one row • Freshwater rays that live in the Amazon basin.
