evolution of fish (early fish)

MD. ABU HORAYRA B.Sc (Hons),Zoology. NATURE EYE CO-ORDINATOR JAGANNATH UNIVERSITY DHAKA,BANGLADESH HELP FROM WIKI

WELCOME EARLY FISH

Fish & Early fish: 1. A limbless cold-blooded vertebrate animal with gills and fins and living wholly in water. 2. Early fish from the fossil record are represented by a group of small, jawless, armoured fish known as ostracoderms. Jawless fish lineages are mostly extinct. An extant clade, the lampreys may approximate ancient pre-jawed fish.

WHAT IS FISH AND EARLY FISH?

The earth past history is divided into six eras: 1.Azoic 2.Archaeozoic or Eozoic 3.Proterozoic(Early life) 4.Palaeozoic(Ancient life,First fish in this era at Ordovician periods,230-505 m.y. ago) 5.Mesozoic (Mediaeval life,135-205 m.y. ago) 6.Cenozoic (Recent life,0.025-75 m.y. ago)

GEOLOGICAL TIME SCALE

Paleozoic era divided into 7 periods: 1.Cambrium (505 m.y. ago, 80 m.y. duration,Trilobites present, No fish in this period) 2.Ordovician (425 m.y. ago, 65 m.y. duration, First fish found, probably freshwater, e.g. Arandaspis) 3.Silurian (360 m.y. ago, 35 m.y. duration, Marine arachnids dominant, rise of fish,e.g. spiny shrak)

DISCUSS ABOUT PALAEOZOIC ERA ON THE BASIS OF EARLY FISH

4.Devonian (325 m.y. ago, 45 m.y. duration, Lung fishes, Sharks abundant) 5.Mississippian/Carboniferous (280 m.y. ago, 25 m.y. duration, spread of ancient shark) 6.Pennsylvanian/Carboniferous (255 m.y. ago, 25 m.y. duration, first reptiles ) 7.Permian(230m.y. ago,25 m.y. duration,many ancient animals died out)

DISCUSS ABOUT PALAEOZOIC ERA ON THE BASIS OF EARLY FISH

EARLY FISH ACCORDING TO GEOLOGICAL TIME SCALE…

Paleozoic era 1.Cambrian period: a)Pikaia Pikaia, along with Myllokunmingia and Haikouichthys ercaicunensis immediately below, are all candidates in the fossil record for the titles of "first vertebrate" and "first fish". Pikaia is a genus that appeared about 530 Ma during the Cambrian explosion of multicellular life.

b) Haikouichthys : Haikouichthys (fish from Haikou) is another genus that also appears in the fossil record about 530 Ma, and also marks the transition from invertebrate to vertebrates.


c)Myllokunmingia : Myllokunmingia is a genus that appeared about 530 Ma. It is a chordate, and it has been argued that it is a vertebrate


2)Ordovician period: a)Arandaspis: Arandaspis are jawless fish that lived in the early Ordovician period, about 480–470 Ma. It was about 15 cm (6 in) long, with a streamlined body covered in rows of knobbly armoured scutes. The front of the body and the head were protected by hard plates with openings for the eyes, nostrils and gills.


b)Astraspis: Astraspis (star shield) is an extinct genus of primitive jawless fish related to other Ordovician fishes, such as Sacabambaspis and Arandaspis. Fossils show clear evidence of a sensory structure (lateral line system).


c)Thelodonts: Thelodonts (nipple teeth) are a class of small, extinct jawless fishes with distinctive scales instead of large plates of armour. There is debate over whether these represent a monophyletic grouping, or disparate stem groups to the major lines of jawless and jawed fish


3)Silurian period: a)Anaspida: Anaspida (without shield) is an extinct class of primitive jawless vertebrates that lived during the Silurian and Devonian periods.


b)Osteostraci: Osteostraci ("bony shields") was a class of bony-armored jawless fish that lived from the Middle Silurian to Late Devonian.


c)Spiny shark: Spiny sharks, more formally called "Acanthodians" (having spines), constitute the class Acanthodii. They first appeared by the late Silurian ~420 Ma, and were among the first fishes to evolve jaws. They share features with both cartilaginous fish and bony fish, but they are not true sharks, though leading to them. They became extinct before the end of the Permian ~250 Ma.


d)Placoderms: Placoderms, (plate-like skin), are a group of armoured jawed fishes, of the class Placodermi. The oldest fossils appeared during the late Silurian, and became extinct at the end of the Devonian. Recent studies suggest that the placoderms are possibly a paraphyletic group of basal jawed fishes.


e)Guiyu oneiros: Guiyu oneiros, the earliest known bony fish. It has the combination of both ray-finned and lobe-finned features, although analysis of the totality of its features place it closer to lobe-finned fish


3)Devonian periods:(early) a)Psarolepis: Psarolepis (speckled scale) is a genus of extinct lobe-finned fish that lived around 397 to 418 Ma. Fossils of Psarolepis have been found mainly in South China and described by paleontologist Xiaobo Yu in 1998.


b)Holoptychius: Holoptychius is an extinct genus from the order of porolepiform lobe-finned fish, extant from 416 to 359 Ma. It was a streamlined predator about 50 centimetres (20 in) long (though it could grow up to 2.5 m), which fed on other bony fish. Its rounded scales and body form indicate that it could have swum quickly through the water to catch prey


c)Petalichthyida: The Petalichthyida was an order of small, flattened placoderms that existed from the beginning of the Devonian to the Late Devonian. They were typified by splayed fins and numerous tubercles that decorated all of the plates and scales of their armour.


d)Laccognathus: Laccognathus (pitted jaw) was a genus of amphibious lobe-finned fish that existed 398–360 Ma. They were characterized by the three large pits (fossae) on the external surface of the lower jaw, which may have had sensory functions.[Laccognathus grew to 1–2 metres (3–7 ft) in length. They had very short dorsoventrally flattened heads, less than one-fifth the length of the body


3)Devonian(mid): a)Dipterus: Dipterus (two wings) is an extinct genus of lungfish from 376–361 Ma. It was about 35 centimetres (14 in) long, mostly ate invertebrates, and had lungs, not an air bladder.


c)Cladoselache: Cladoselache was the first abundant genus of primitive shark, appearing about 370 Ma.


c)Pituriaspida: Pituriaspida (hallucinogenic shield) is a class containing two bizarre species of armoured jawless fishes with tremendous nose-like rostrums. They lived in estuaries around 390 Ma.


3)Devonian(late): a)Dunkleosteus: Dunkleosteus is a genus of arthrodire placoderms that existed from 380 to 360 Ma. It grew up to 10 metres (33 ft) long


b)Materpiscis: Materpiscis (mother fish) is a genus of ptyctodontid placoderm from about 380 Ma. Known from only one specimen, it is unique in having an unborn embryo present inside, and with remarkable preservation of a mineralised placental feeding structure (umbilical cord). This makes Materpiscis the first known vertebrate to show viviparity, or giving birth to live young.


4)Carboniferous period: a)Stethacanthidae: As a result of the evolutionary radiation, carboniferous sharks assumed a wide variety of bizarre shapes—including sharks of the family Stethacanthidae.


b)Falcatus: Falcatus is a genus of small cladodont-toothed sharks that lived 335–318 Ma. They were about 25–30 cm (10–12 in) long.They are characterized by the prominent fin spines that curved anteriorly over their heads.


5)Permian period: a)Acanthodes: Acanthodes are an extinct genus of spiny shark.It had gills but no teeth and was presumably a filter feeder.


Mesozoic era(75-205 Ma) 1)Triassic (205 m.y. ago): a) Pachycormiformes: Pachycormiformes are an extinct order of ray-finned fish that existed from the Middle Triassic to the K-Pg extinction (below). They were characterized by serrated pectoral fins, reduced pelvic fins and a bony rostrum.


b)Pholidophorus: Pholidophorus was an extinct genus of teleost, around 40 centimetres (16 in) long, from about 240–140 Ma.


2)Jurassic period(165 Ma): a)Ichthyodectidae: The family Ichthyodectidae (literally "fish-biters") was a family of marine actinopterygian fish. They first appeared 156 Ma during the Late Jurassic and disappeared during the K-Pg extinction event 66 Ma. They were most diverse throughout the Cretaceous period. E.g. Ichthyodectidae,Gillicus arcuatus.


3)Cretaceous period(135 Ma): a)Sturgeon: True sturgeons appear in the fossil record during the Upper Cretaceous. Since that time, sturgeons have undergone remarkably little morphological change, indicating their evolution has been exceptionally slow and earning them informal status as living fossils.


b)Cretoxyrhina: Cretoxyrhina mantelli was a large shark that lived about 100 to 82 million years ago, during the mid Cretaceous period. It is commonly known as the Ginsu Shark. The specimen consisted of a nearly complete associated vertebral column and over 250 associated teeth. shark's skeleton is made of cartilage.


c)Enchodus: Enchodus is an extinct genus of bony fish. It flourished during the Upper Cretaceous and was small to medium in size. One of the genus' most notable attributes are the large "fangs" at the front of the upper and lower jaws


d)Ptychodus: Ptychodus is a genus of extinct hybodontiform shark that lived from the late Cretaceous to the Paleogene.


Cenozoic era: a)Amphistium: Amphistium is a 50-million-year-old fossil fish that has been identified as an early relative of the flatfish, and as a transitional fossil.


a)Megalodon: Megalodon is an extinct species of shark that lived about 28 to 1.5 Ma. It looked much like a stocky version of the great white shark .


THE END

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evolution of fish (early fish)

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