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Early vertebrates and Primitive fish
Descripción
(Early vertebrates/primitive fish) Vertebrate Zoology Mapa Mental sobre Early vertebrates and Primitive fish, creado por Litty Carter el 23/04/2013.
Sin etiquetas
early vertebrates/primitive fish
vertebrate zoology
vertebrate zoology
early vertebrates/primitive fish
Mapa Mental por
Litty Carter
, actualizado hace más de 1 año
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Litty Carter
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Resumen del Recurso
Early vertebrates and Primitive fish
What is a fish?
All vertebrates which aren't tetrapods
Aquatic vertebrate
(appendages - fins)
Gills
Aquatic vertebrate
Paraphyletic group
Skin with scales of dermal region
Early vertebrates
Early Cambrian fossils (535mya)
China - lack mineralised tissues
Heart and fin rays
Mineralised tissue - late Cambrian
CONODONTS
Microfossils made of Apatite: Cambrian-Triassic
Similar to dentine
Diet: Marine algae/inverts
Many vertebrate characteristics
(but no gill slits)
Diffusion?
MINERALISED TISSUE
Agnatha
(Jawless fish)
Hagfish & Lampreys
Hagfish (Myxinoidea)
~ 65 spp (all marine)
Scavengers & predators
Single nasal opening. Single semi-circular canal
Degenerate eyes (skin covered)
Mucoid bag
Skewed sex ratios (100:1)
Eggs with tough covering and attachment hooks
Colonial/semi-colonial
Lampreys (Petromyzontia)
41spp ( ~50% parasitic)
Marine & freshwater
Cartilage pipe around notochord (Arcualia)
Simple digestive system
Well developed kidney
Oral gland anticoagulent
2 semicircular canals
Chloride cells gills : tidal ventilation
No scales
Eel like bodies
No distinct stomach, jaws or vertabrae
Cartilaginous
5-16 pairs of gills
Distinct Brain
Ostracoderms
Anapsids
relationship in flux
Lacked jaws - movable mouth plates
filter feed / soft bodied prey
midline dorsal fins & some pectoral
Extinct: late devonian
Jawless to Jaws
Major evolutionary step: changes in habitat/behaviourresources
1. Ancestral Agnathan: unjointed branchial arches
2. Jointed branchial arches increase ventilation
3. Mouth closing ventilatory jaws
4. Early jawed Gnathostome
Improved locomotion, sensory and ciculatory systems
Silurian -> mid Ordovician
2nd Hox duplication event
Enlarged forebrain
Lateral line system
4 recognised clades
Gnathostomata
Class: Placoderms
Plated skin
Plates hinged
Internal skeleton: bone & cartilage
Plated teeth: Ptyctodontids
Early specimens - no teeth. Later on - true teeth
Primarily marine but some in estuaries and fresh water
Primary benthic - dorsoventrally flattened
External pelvic appendages
Class: Acanthodians
Many short spines and ventral fins
Slender bodied
Mid Ordovician
Scales and heterocercal tail - primarily midwater
No teeth - filter feeders
Class: Condrychthyes (cartilaginous fish)
Subclass: Elasmobranchii
Sharks, skates, rays
Subclass: Holocephali
Chimaeras & ghost fish
Osteichthyes (bony fish)
Class: Sarcopterygii
Lobe finned fish
Class: Actinopterygii
Ray finned fish
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