a history of fishes. 2 evolutionary history fish have adapted to a wide range of environmental...
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A History of Fishes
A History of Fishes 2
Evolutionary History
Fish have adapted to a wide range of environmental parameters• Temperatures -1.8°C - 40°C• pH 4 - 10
• O2 Concentrations 0 - Saturation
• Salinity 0 - 90• Depths 0 - 7000m
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Diversity and Evolution
The diversity of fishes reflects their long evolutionary history
A major challenge to ichthyologists involves unraveling the evolutionary pathways of both extant (living) and extinct taxa
Evolutionary History
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Conodonts
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Ostracoderms
Characteristics:1. Lack of jaws2. Lack of paired fins3. Bony armor4. Internal cartilaginous skeleton
Modern day representatives of this group:• Class Pteraspidomorphi (hagfishes)• Class Cephalaspidomorphi (lampreys)
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Ostracoderms
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Early Jawed fishes
Gnathostomes
• Jaws are probably the greatest advancement in vertebrate evolutionoThis allowed for an explosion in diversity
due to the different prey items that can be processed
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Placoderms
Diverse group with a bizarre appearance
1. Jaws2. Dermal body plates3. Internal skeleton4. Paired fins
Some were over 6 meters in size and possessed a craniovertebral joint
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Placoderms
Dinichthys
Craniovertebral joint
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Placoderms
Gemuendina
Bothriolepis
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Chondrichthyes
Arose during the early Paleozoic and followed a very different line of evolution• Cartilaginous fishes, 2 distinct lines of
evolution, the connection between the two is poorly understood
o Since cartilage does not readily fossilize not a very good fossil record
Characteristics
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Chondrichthyes
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Chondrichthyes
Two distinct evolutionary lines1. Subclass Elasmobranchii
o Sharks, skates, and rays
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Chondrichthyes
Two distinct evolutionary lines2. Subclass Holocephali
o Ratfishes or chimaeras
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Sarcopterygii (Lobe-finned fishes)
Present day lungfishes and coelacanths • This group has paired fins which actually have muscle in the fin
itself It is this class which is believed to have given rise to the
amphibians
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Actinopterygii (Ray-finned fishes)
The most successful of all the modern fishes
1. Triangular dorsal fin2. Paired fins without
fleshy lobes3. Ray-finned
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Actinopterygii (Ray-finned fishes)
Subclass Chondrostei• Sturgeons, and
paddlefishes
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Actinopterygii (Ray-finned fishes)
Subclass Neopterygii• Remaining
23,000+ bony fishes
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Evolutionary Review
Ostracoderms - primitive jawless fishes
No living representatives, possible relatives include hagfish and lamprey
Class Placodermi - first jawed fishes
No apparent descendants
Class Chondrichthyes - cartilaginous fishes
Subclass Holocephali - ratfishes
Subclass Elasmobranchii -sharks, skates, & rays
Class Osteichthyes - bony fishes
Subclass Sarcopterygii - lobe-finned fishes
Present day lungfishes and coelacanth
Subclass Actinopterygii - ray-finned fishes
Infraclass Chondrostei - sturgeons & paddlefishes
Infraclass Neopterygii - remaining bony fishes
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Population Distributions
By volume, 97% of all water on earth is found in the worlds oceans• 58% of all fish species are marine• 41% are freshwater species• 1% move between the two habitats
Marine Habitat• 13% of marine species associate in open
water• 78% live over the continental shelf
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Physical Properties of Water
Water is 800x denser than air!
Water is incompressible
Water is a universal solvent
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Have you hugged your Ichthyologist?
Ichthyology - study of fishes• Describing new taxa • Understanding evolutionary
relationshipsoTaxonomy and systematics
• Ecology, physiology, and behavior
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Nomenclature
The most frustrating aspect of ichthyology is the constant changing of scientific names
These names change for several reasons Changes are necessary as new
information is discovered concerning evolutionary history
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Species Names
Each spp. is assigned a unique two part scientific name• Longnose Dace Rhinichthys cataractae
(Valenciennes 1842)
• Names are usually descriptive in some wayoRhinichthys - nose-fishocataractae - the fast water in which it lives
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