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Riga 1:
[[File:Ostracoderm and placoderm.jpg|right|thumb|250px|I primi pesci fossili: [[ostracodermi]] (sopra) e [[Placodermi]]]]
L'evoluzione dei pesci non è studiata come un singolo evento da quanto la riorganizzazione sistematica dei [[pesci]] ha portato al disconocimento di questi come gruppo monofiletico{{sfn|Lecointre|Le Guyader|2007|ps=}}.
I primi pesci apparvero durante la cosidetta [[esplosione cambriana]], circa 530 milioni di anni fa: questi ritrovamenti [[fossili]] appartengono ad un gruppo di piccoli pesci corazzati senza mascelle, noti come [[ostracodermi]], oggi estinti. Un [[clade]] imparentato ed esistente, comprendente le [[Lampreda|lamprede]]. Le prime mascelle appaiono invece nei [[Placodermi]]. La diversità di questi vertebrati indica il vantaggio evolutivo di una [[bocca]] provvista di mascelle, anche se ancora non è chiaro chiaro se il vantaggio comprenda un morso con maggior resistenza, una respirazione migliorata o una combinazione di entrambi i fattori.
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{{clear}}
Riga 72 ⟶ 56:
{{clear}}
==Pesci senza mascelle==
[[File:Lamprey attached.png|thumb|260px|right|A modern jawless fish, the [[lamprey]], attached to a modern jawed fish]]
[[File:Petromyzon marinus.003 - Aquarium Finisterrae.JPG|thumb|140px|right|{{center|Lamprey mouth}}]]
Riga 85 ⟶ 69:
[[File:Evolution of jawless fish.png|thumb|260px|right|Evolution of [[Agnatha|jawless fishes]]. The diagram is based on [[Michael Benton]], 2005.<ref name="Benton, M. J. 2005 page 73">Benton, M. J. (2005) Vertebrate Palaeontology, Blackwell, 3rd edition, Fig 3.25 on page 73.</ref>]]
{{clade| style=font-size:85%;line-height:70%
|label1=[[Agnatha|'''
|1={{clade
|1=[[Hyperoartia]] (
|2=?†[[Euconodonta]] (
|label3=<span style="color:white;">unnamed</span>
|3={{clade
|1=†[[Pteraspidomorphi]] (
|2=?†[[Thelodonti]] (
|label3=<span style="color:white;">unnamed</span>
|3={{clade
|1=?†[[Anaspida]] (
|label2=<span style="color:white;">unnamed</span>
|2={{clade
|1=†[[Galeaspida]] (
|label2=<span style="color:white;">unnamed</span>
|2={{clade
|1=?†[[Pituriaspida]] (
|2=†[[Osteostraci]] (
|3=[[Gnathostomata|'''
}}
}}
Riga 116 ⟶ 100:
{{clear}}
===<sup>†</sup>
[[File:Euconodonta.gif|thumb|140px|right|{{center|<sup>†</sup>[[Conodonts]] (extinct) resembled primitive jawless eels}}]]
[[Conodont]]s resembled primitive jawless eels. They appeared 495 Ma and were wiped out 200 Ma.{{r|Renzi1996}} Initially they were known only from tooth-like microfossils called ''conodont elements''. These "teeth" have been variously interpreted as filter-feeding apparatuses or as a "grasping and crushing array".{{r|Gabbott1995}} Conodonts ranged in length from a centimeter to the 40 cm ''[[Promissum]]''.{{r|Gabbott1995}} Their large eyes had a lateral position of which makes a predatory role unlikely. The preserved musculature hints that some conodonts (''Promissum'' at least) were efficient cruisers but incapable of bursts of speed.{{r|Gabbott1995}} In 2012 researchers classify the conodonts in the [[Phylum (biology)|phylum]] [[Chordata]] on the basis of their fins with fin rays, [[Chevron (insignia)|chevron]]-shaped muscles and [[notochord]].{{r|Briggs1992}} Some researchers see them as vertebrates similar in appearance to modern [[hagfish]] and [[lamprey]]s,{{r|Milsom2004}} though [[phylogenetic]] analysis suggests that they are more [[derived]] than either of these groups.{{r|Donoghue2000}}
===<sup>†</sup>
[[File:Astraspis desiderata.gif|thumb|140px|right|{{center|<sup>†</sup>[[Ostracoderms]] (extinct) were armoured jawless fishes}}]]
Riga 132 ⟶ 116:
Ostracoderms existed in two major groups, the more primitive [[Heterostraci|heterostracans]] and the [[cephalaspidomorphi|cephalaspids]]. Later, about 420 million years ago, the jawed fish evolved from one of the ostracoderms. After the appearance of jawed fish, most ostracoderm species underwent a decline, and the last ostracoderms became extinct at the end of the [[Devonian period]].<ref>[http://www.cosmosmagazine.com/news/4492/vertebrate-jaw-design-locked-down-early Vertebrate jaw design locked down early]</ref>
==
[[File:Dunkleosteus skull steveoc.jpg|thumb|360px|right|]]
[[File:DunkleosteusSannoble.JPG|thumb|216px|right|
Riga 192 ⟶ 176:
{{clear}}
===<sup>†</sup>
[[File:Evolution of placoderms.png|thumb|260px|right|Evolution of the (now extinct) [[placoderms]]. The diagram is based on [[Michael Benton]], 2005.<ref name="Benton, M. J. 2005 page 73"/>]]
[[File:Coccosteus BW.jpg|thumb|left|<sup>†</sup>[[Placoderm]]s (extinct) were armoured jawed fishes (compare with the ostracoderms above)]]
Riga 207 ⟶ 191:
{{clear}}
===
[[File:Evolution of cartilaginous fishes.png|thumb|260px|right|Radiation of [[cartilaginous fish]]es, derived from work by [[Michael Benton]], 2005.<ref>Benton, M. J. (2005) Vertebrate Palaeontology, Blackwell, 3rd edition, Fig 7.13 on page 185.</ref>]]
{{further2|[[List of transitional fossils#Chondrichthyes]]|[[List of prehistoric cartilaginous fish]]}}
Riga 215 ⟶ 199:
{{clear}}
===
{{further2|[[Osteichthyes]]|[[List of transitional fossils#Bony Fish]]|[[List of prehistoric bony fish]]}}
{{ external media
Riga 251 ⟶ 235:
{{Phanerozoic eon}}
===Pre
{| class="wikitable"
|-
! rowspan=6 style=
| colspan="3" style="text-align:center; background:#ddf8f8;"| [[
|-
| [[File:Pikaia BW.jpg|140px]]
| ''[[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 (biology)|genus]] that appeared about 530 [[mya (unit)|Ma]] during the [[Cambrian explosion]] of multicellular life. [[Pikaia gracilens]] ''(pictured)'' is a [[transitional fossil]] between invertebrates and vertebrates,{{sfn|Dawkins|2004|p=289|ps=: "Obviously vertebrates must have had ancestors living in the Cambrian, but they were assumed to be invertebrate forerunners of the true vertebrates — protochordates. Pikaia has been heavily promoted as the oldest fossil protochordate."}} and may be the earliest known [[chordate]].{{r|Morris1979}}{{r|Morris2012}} In this sense it may have been the original ancestor of fishes. It was a primitive creature with no evidence of eyes, without a well defined head, and less than 2 inches (5 centimetres) long. ''Pikaia'' was a sideways-flattened, leaf-shaped animal which swam by throwing its body into a series of S-shaped, zig-zag curves, similar to movement of snakes. Fish inherited the same swimming movement, but they generally have stiffer backbones. It had a pair of large head tentacles and a series of short appendages, which may be linked to gill slits, on either side of its head. ''Pikaia'' shows the essential prerequisites for [[vertebrates]]. The flattened body is divided into pairs of [[myomere|segmented muscle block]]s, seen as faint vertical lines. The muscles lie on either side of a flexible structure resembling a rod that runs from the tip of the head to the tip of the tail.{{sfn|Palmer|2000|p=66-67}}
|-
| [[File:Haikouichthys 3d.png|140px]]
| ''[[Haikouichthys]]''
| ''[[Haikouichthys]]'' (il cui nome scientifico significa ''
|-
| [[File:Myllokunmingia.png|140px]]
| ''[[Myllokunmingia]]''
| ''[[Myllokunmingia]]'' è un genere apparso circa 530 milioni di anni fa. Apparteneva ai [[Cordata|cordati]], aveva dimensioni minute (28 mm di lunghezza e 6 di altezza) ed è tra le più antiche forme di vita [[vertebrati|vertebrate]].
|-
| [[File:Euconodonta.gif|140px]]
| [[
| [[Conodont]]s ''(cone-teeth)'' resembled primitive eels. They appeared 495 Ma and were wiped out 200 Ma.{{r|Renzi1996}} Initially they were known only from tooth-like microfossils called ''conodont elements''. These "teeth" have been variously interpreted as filter-feeding apparatuses or as a "grasping and crushing array".{{r|Gabbott1995}} Conodonts ranged in length from a centimeter to the 40 cm ''[[Promissum]]''.{{r|Gabbott1995}} Their large eyes had a lateral position of which makes a predatory role unlikely. The preserved musculature hints that some conodonts (''Promissum'' at least) were efficient cruisers but incapable of bursts of speed.{{r|Gabbott1995}} In 2012 researchers classify the conodonts in the [[Phylum (biology)|phylum]] [[Chordata]] on the basis of their fins with fin rays, [[Chevron (insignia)|chevron]]-shaped muscles and [[notochord]].{{r|Briggs1992}} Some researchers see them as vertebrates similar in appearance to modern [[hagfish]] and [[lamprey]]s,{{r|Milsom2004}} though [[phylogenetic]] analysis suggests that they are more [[derived]] than either of these groups.{{r|Donoghue2000}}
|-
| [[File:Thelodonti.gif|140px]]
| [[
| [[Ostracoderms]] ''(shell-skinned)'' are any of several groups of extinct, primitive, jawless fishes that were covered in an armour of bony plates. They appeared in the [[Cambrian]], about 510 million years ago, and became [[extinct]] towards the end of the [[Devonian]], about 377 million years ago. Initially Ostracoderms had poorly formed fins, and paired [[Fish fin|fins]], or limbs, first evolved within this group. They were covered with a bony armour or scales and were often less than 30 cm (1 ft) long.
|-
! rowspan=6 style=
| colspan="3" style="text-align:center; background:#ddf8f8;"| [[
|-
| [[File:
| [[Heterostraci]]
| [[Heterostraci]] è una classe estinta di agnati vertebrati che viveva principalmente in ambienti marini e di estuario. Sono apparsi all'inizio dell'Ordoviciano e si estinse alla fine del Devoniano. Differivano dagli altri pesci senza mandibola del periodo nella disposizione e nell'[[istologia]] delle loro [[scaglia|scaglie]].
|-
| [[File:Astraspis desiderata.gif|center|110px]]
Riga 298 ⟶ 278:
|-
| [[File:Shielia tiati.svg|center|125px]]
| [[
| [[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 [[Monophyly|monophyletic grouping]], or disparate stem groups to the major lines of [[Agnatha|jawless]] and [[Gnathostome|jawed fish]].{{r|Turner1982}} Thelodonts are united by their characteristic "thelodont scales". This defining character is not necessarily a result of shared ancestry, as it may have been [[Convergent evolution|evolved independently by different groups]]. Thus the thelodonts are generally thought to represent a polyphyletic group.{{sfn|Sarjeant|Halstead}} If they are monophyletic, there is no firm evidence on what their ancestral state was.{{sfn|Donoghue|2000|p=206}} These scales were easily dispersed after death; their small size and resilience makes them the most common vertebrate fossil of their time.{{sfn|Turner1999|p=42–78}}{{r|Palaeos: Thelodonti}} The fish lived in both freshwater and marine environments, first appearing during the [[Ordovician]], and perishing during the [[Late Devonian extinction|Frasnian–Famennian extinction event]] of the Late [[Devonian]]. They were predominantly deposit-feeding bottom dwellers, although some species may have been pelagic.
|-
| colspan="3" style="line-height:16px; background:#dddddd;"| <small>The Ordovician ended with the [[Ordovician–Silurian extinction event]] (450–440 Ma). Two events occurred that killed off 27% of all families, 57% of all genera and 60% to 70% of all species.{{r|Baez2006}} Together they are ranked by many scientists as the second largest of the five major extinctions in Earth's history in terms of percentage of [[genus|genera]] that went extinct.</small>
|-
! rowspan=7 style=
| colspan="3" style="text-align:center; background:#ddf8f8;"| [[Silurian]] (443–419 Ma): Many evolutionary milestones occurred during this period, including the appearance of armoured jawless fish, jawed fish, spiny sharks and ray-finned fish.
|-
Riga 319 ⟶ 299:
|-
| [[File:Silurolepis platydorsalis.jpg|140px]]
| [[
| [[
|-
| [[File:Guiyu BW.jpg|140px]]
| ''[[Guiyu oneiros]]''
| ''[[Guiyu oneiros]]''
|-
|
| ''[[Andreolepis]]''
|
|}
===
{{include timeline|Fish}}
Riga 352 ⟶ 332:
:::{| class="wikitable"
|-
| colspan="5" style="text-align:center; background:#ddf8f8;"| [[
|-
| colspan="5" |
|-
! rowspan=18 style=
| rowspan=6 style=
| colspan="3" style="text-align:center; background:#ddf8f8;"| [[
|-
| [[File:Psarolepis BW.jpg|140px]]
Riga 380 ⟶ 360:
| ''[[Laccognathus]]'' ''(pitted jaw)'' was a genus of [[amphibious fish|amphibious]] lobe-finned fish that existed 398–360 Ma.<ref name="ngs">{{cite web|url=http://news.nationalgeographic.com/news/2011/09/110912-ancient-fish-arctic-predator-devonian-fossils-animals-science/|title=Ancient Toothy Fish Found in Arctic—Giant Prowled Rivers|author=[[Christine Dell'Amore|Dell'Amore, C.]]|date=September 12, 2011|publisher=[[National Geographic Society|National Geographic]] Daily News|accessdate=September 13, 2011}}</ref> They were characterized by the three large pits (fossae) on the external surface of the lower jaw which may have had sensory functions.<ref name="avril">{{cite web|url=http://articles.philly.com/2011-09-12/news/30145487_1_tiktaalik-roseae-ted-daeschler/2|title=Fish fossil sheds light on 'Euramerica' phase|author=Tom Avril|date=September 12, 2011|publisher=The Inquirer|accessdate=September 15, 2011}}</ref> ''Laccognathus'' grew to {{convert|1|-|2|m|ft|0}} in length. They had very short dorsoventrally flattened heads, less than one-fifth the length of the body.<ref name="vorobyeva">{{cite journal|author=[[Emiliya Ivanovna Vorobyeva|Vorobyeva, E.I.]]|year=2006|title=A new species of ''Laccognathus'' (Porolepiform Crossopterygii) from the Devonian of Latvia |journal=[[Paleontological Journal|Palaeont. J.]]|volume=40|issue=3|pages=312–322|publisher=Physorg.com|doi=10.1134/S0031030106030129}}</ref> The skeleton was structured so large areas of skin were stretched over solid plates of bone. This bone was composed of particularly dense fibers – so dense that exchange of oxygen through the skin was unlikely. Rather, the dense [[ossification]]s served to retain water inside the body as ''Laccognathus'' traveled on land between bodies of water.<ref name = "witzmann">{{cite journal|author=[[Florian Witzman|Witzman, F.]]|journal=[[Paleodiversity]]|volume=31|issue=5|pages=981–996|year=2011|publisher=The Society of Vertebrate Paleontology|title=A New Species of ''Laccognathus'' (Sarcopterygii, Porolepiformes) from the Late Devonian of Ellesmere Island, Nunavut, Canada}}</ref>
|-
| rowspan=7 style=
| colspan="3" style="text-align:center; background:#ddf8f8;"| [[
|-
| [[File:Dipterus valenciennesi1.jpg|140px]]
Riga 395 ⟶ 375:
| ''[[Coccosteus]]'' ''(seed bone)'' is an extinct genus of [[arthrodire]] [[placoderm]]. The majority of fossils have been found in freshwater sediments, though they may have been able to enter saltwater. They grew up to {{convert|40|cm|in}} long. Like all other arthrodires, ''Coccosteus'' had a joint between the armour of the body and skull. In addition, it also had an internal joint between its neck [[vertebrae]] and the back of the skull, allowing for the mouth to be opened even wider. Along with the longer jaws, this allowed ''Coccosteus'' to feed on fairly large prey. As with all other arthrodires, ''Coccosteus'' had bony dental plates embedded in its jaws, forming a beak. The beak was kept sharp by having the edges of the dental plates grind away at each other.{{sfn|The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals|1999|p=32}}
|-
| [[File:Bothriolepis canadensis 2.jpg|center|120px]]
| ''[[Bothriolepis]]''
|
''[[Bothriolepis]]'' è stato il genere di [[placodermi]] più diffuso nei ritrovamenti fossili, con oltre 100 specie scoperte negli strati rocciosi del Devoniano medio in ogni continente.
|-
| [[File:Pituriaspis doylei.jpg|center|80px]]
Riga 410 ⟶ 386:
| colspan="3" style="line-height:16px; background:#dddddd;"| <small>[[Late Devonian extinction]]: 375–360 Ma. A prolonged series of extinctions eliminated about 19% of all families, 50% of all genera{{r|Baez2006}} and 70% of all species. This extinction event lasted perhaps as long as 20 Ma, and there is evidence for a series of extinction pulses within this period.</small>
|-
| rowspan=5 style=
| colspan="3" style="text-align:center; background:#ddf8f8;"| [[
|-
| [[File:Dunkleosteus
| ''[[Dunkleosteus]]''
| {{ external media
Riga 435 ⟶ 411:
''[[Materpiscis]]'' ''(mother fish)'' is a [[genus]] of [[ptyctodontid]] [[Placodermi|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 [[vivipary|viviparity]], or giving birth to live young.{{r|Long2008}} The specimen was named ''Materpiscis attenboroughi'' in honour of [[David Attenborough]].{{r|BBC2008}}
|-
|
| [[Rhizodont]]s
| [[Rhizodont]]s were an order of lobe-finned fish which survived to the end of the Carboniferous, 377–310 Ma. They reached huge sizes. The largest known species, ''[[Rhizodus|Rhizodus hibberti]]'' grew up to 7 metres in length, making it the largest freshwater fish known.
Riga 442 ⟶ 418:
{{clear}}
===
{{further|Tetrapod#Evolution|List of transitional fossils#Fish to Tetrapods}}
Riga 511 ⟶ 487:
! colspan=4 | Transition from lobe-finned fishes to tetrapods
|-
| [[File:Eusthenopteron model.jpg|140px]]<small>~385 milioni di anni fa</small>
| ''[[Eusthenopteron]]''
| {{ external media
Riga 524 ⟶ 500:
| ''[[Gogonasus]] (snout from Gogo)'' was a lobe-finned fish known from 3-dimensionally preserved 380 million-year-old fossils found in the [[Gogo Formation]]. It was a small fish reaching 30–40 cm (1 ft) in length.<ref>http://dinosaurs.about.com/od/tetrapodsandamphibians/p/gogonasus.htm</ref> Its skeleton shows several tetrapod-like features. They included the structure of its [[middle ear]], and its fins show the precursors of the forearm bones, the [[radius]] and [[ulna]]. Researchers believe it used its forearm-like fins to dart out of the reef to catch prey. ''Gogonasus'' was first described in 1985 by [[John A. Long]]. For almost 100 years ''[[Eusthenopteron]]'' has been the role model for demonstrating stages in the evolution of lobe-finned fishes to tetrapods. ''Gogonasus'' now replaces ''Eusthenopteron'' in being a better preserved representative without any ambiguity in interpreting its anatomy.
|-
| [[File:Panderichthys BW.jpg|140px]]<br /><small>~385 milioni di anni fa</small>
| ''[[Panderichthys]]''
| Adapted to muddy shallows, and capable of some kind of shallow water or terrestrial body flexion locomotion. Had the ability to prop itself up.<ref>Nature: [http://www.nature.com/nature/journal/v438/n7071/edsumm/e051222-13.html The pelvic fin and girdle of ''Panderichthys'' and the origin of tetrapod locomotion]</ref><br /> They had large tetrapod-like heads, and are thought to be the most crownward stem fish-tetrapod with paired fins.
|-
| [[File:Tiktaalik BW.jpg|140px]]<br /><small>~375 milioni di anni fa</small>
| ''[[Tiktaalik]]''
| A fish with limb-like fins that could take it onto land.<ref name=Nature>{{cite journal | journal = [[Nature (journal)|Nature]] | volume = 440 | pages = 757–763 | date = 6 April 2006 | doi = 10.1038/nature04639 | title = A Devonian tetrapod-like fish and the evolution of the tetrapod body plan | url = http://www.nature.com/nature/journal/v440/n7085/abs/nature04639.html | author = Edward B. Daeschler, Neil H. Shubin and Farish A. Jenkins, Jr | pmid = 16598249 | issue = 7085}}</ref> It is an example from several lines of ancient sarcopterygian fish developing adaptations to the oxygen-poor shallow-water habitats of its time, which led to the evolution of tetrapods.<ref name="scientificamerican">[[Jennifer A. Clack]], ''Scientific American'', [http://www.scientificamerican.com/article.cfm?id=getting-a-leg-up-on-land ''Getting a Leg Up on Land''] Nov. 21, 2005.</ref> Paleontologists suggest that it is representative of the [[transitional fossil|transition]] between non-tetrapod vertebrates (fish) such as ''[[Panderichthys]]'', known from fossils 380 million years old, and early tetrapods such as ''[[Acanthostega]]'' and ''[[Ichthyostega]]'', known from fossils about 365 million years old. Its mixture of primitive fish and derived tetrapod characteristics led one of its discoverers, [[Neil Shubin]], to characterize ''Tiktaalik'' as a "[[Tetrapodomorpha|fishapod]]".<ref>John Noble Wilford, ''The New York Times'', [http://www.nytimes.com/2006/04/05/science/05cnd-fossil.html?hp&ex=1144296000&en=fe3427d67e965e46&ei=5094&partner=homepage ''Scientists Call Fish Fossil the Missing Link''], Apr. 5, 2006.</ref><ref name="Shubin 2008">{{cite book|last=Shubin|first=Neil|title=Your Inner Fish|publisher=Pantheon|year=2008|isbn=978-0-375-42447-2}}</ref>
|-
| [[File:Acanthostega BW.jpg|140px]]<br /><small>365 milioni di anni fa</small>
| ''[[Acanthostega]]''
| A fish-like early [[Labyrinthodontia|labyrinthodont]] which occupied weed-filled swamps and changed views about the early evolution of tetrapods.{{r|Clack2005}} [[Polydactyly in early tetrapods|It had eight digits]] on each hand (the number of digits on the feet is unclear) linked by webbing, it lacked wrists, and was generally poorly adapted to come onto land.<ref>"[http://www.devoniantimes.org/Order/re-acanthostega.html Acanthostega gunneri]," ''Devonian Times''.</ref> Sunsequent discoveries revealed earlier transitional forms between ''Acanthostega'' and completely fish-like animals.{{r|Daeschler2006}}
|-
| [[File:Ichthyostega BW.jpg|140px]]<br /><small>374–359 milioni di anni fa</small>
| ''[[Ichthyostega]]''
| {{ external media
Riga 546 ⟶ 522:
Until finds of other early tetrapods and closely related fishes in the late 20th century, ''[[Ichthyostega]]'' stood alone as the transitional fossil between fish and tetrapods, combining a fishlike tail and gills with an amphibian skull and limbs. It possessed lungs and limbs with seven digits that helped it navigate through shallow water in weed-filled swamps.
|-
| [[File:Pederpes22small.jpg|140px]]<br /><small>359–345 milioni di anni fa</small>
| ''[[Pederpes]]''
| ''[[Pederpes]]'' is the earliest known fully terrestrial tetrapod. It is included here to complete the transition of lobe-finned fishes to tetrapods, even though ''Pederpes'' is no longer a fish.
Riga 556 ⟶ 532:
* [http://www.scientificamerican.com/article.cfm?id=fossil-illuminates-evolut Fossil Illuminates Evolution of Limbs from Fins] ''Scientific American'', 2 2 April 2004.
===Post
L'[[Mesozoico|Era Mesozoica]] inizia circa 250 milioni di anni fa sulla scia dell'[[Estinzione di massa del Permiano-Triassico]], la più grande [[estinzione]] della storia della [[Terra]], e finisce circa 65 milioni di anni fa, con l'[[Estinzione di massa del Cretaceo-Paleocene]], un'altra estinzione massiva che uccise i [[dinosauri]] e moltre specie di piante e animali. É spesso definita come l'''età dei rettili'', perché i rettili sono stati i vertebrati dominanti in questa era. Durante il Mesozoico inoltre il maxicontinente [[Pangea]] si divide gradualmente in continenti più piccoli. Il clima alterna periodi molto caldi a periodi più freddi, ma nel complesso la Terra era più calda di quanto non lo sia oggi.
{| class="wikitable"
|-
! rowspan=5 style=
| colspan="3" style="text-align:center; background:#ddf8f8;"| [[Carboniferous]] (359–299 Ma): [[Shark]]s underwent a major [[evolutionary radiation]] during the [[Carboniferous]].<ref name=goldsharks/> It is believed that this evolutionary radiation occurred because the decline of the [[Placodermi|placoderms]] at the end of the Devonian period caused many [[Niche (ecology)|environmental niches]] to become unoccupied and allowed new organisms to evolve and fill these niches.<ref name=goldsharks/>
|-
Riga 580 ⟶ 555:
| [[File:Falcatus.jpg|140px]]
| ''[[Falcatus]]''
|
|-
| [[File:Orodus sp1DB.jpg|140px]]
| ''[[Orodus]]''
| ''[[Orodus]]''
|-
! rowspan=3 style=
| colspan="3" style="text-align:center; background:#ddf8f8;"| [[
|-
| [[File:Acanthodes BW.jpg|140px]]
Riga 593 ⟶ 568:
| ''[[Acanthodes]]'' are an extinct genus of [[Acanthodii|spiny shark]].<ref>{{cite journal|year=1880|title=Proceedings of the Royal Physical Society of Edinburgh|volume= V.|pages=p115|url=http://books.google.com/?id=69kKAAAAIAAJ&pg=PA115&dq=Acanthodes+extinct|doi=10.1111/|author1=Edinburgh, Royal Physical Society of}}</ref> It had [[gill]]s but no [[teeth]],<ref name="Nicholson">{{cite book|last=Nicholson|first=Henry Alleyne|coauthors=Richard Lydekker|title=A Manual of Palaeontology|year=1889|url=http://books.google.com/?id=MoAXAAAAYAAJ&pg=PA966&dq=Acanthodes+pectoral+fins|page=966}}</ref> and was presumably a [[filter feeder]].<ref name=EoDP/> ''Acanthodes'' had only two skull bones and were covered in cubical scales. Each paired [[pectoral fin|pectoral]] and [[pelvic fin]]s had one spine, as did the single [[anal fin|anal]] and [[dorsal fin]]s, giving it a total of six spines, less than half that of many other spiny sharks.<ref name=EoDP>{{cite book |editor=Palmer, D.|year=1999 |title= The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals|publisher= Marshall Editions|___location=London|pages= 30–31|isbn= 1-84028-152-9}}</ref> Acanthodians share qualities of both bony fish (osteichthyes) and cartilaginous fish (chondrichthyes), and it has been suggested that they may have been stem chondrichthyans and stem gnathostomes.<ref>Article on Acanthodes as ancestor of Man, http://www.sci-news.com/paleontology/article00396.html, accessed 15 June 2012</ref><ref>Journal article on Acanthodes, http://www.nature.com/nature/journal/v486/n7402/full/nature11080.html, accessed 15 June 2012</ref>
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| colspan="3" style="line-height:16px; background:#dddddd;"| <small>The Permian ended with the most extensive [[extinction event]] recorded in [[paleontology]]: the [[Permian-Triassic extinction event]]. 90% to 95% of marine species became [[Extinction|extinct]], as well as 70% of all land organisms. It is also the only known mass extinction of insects.<ref>http://geology.about.com/od/extinction/a/aa_permotrias.htm</ref><ref>http://www.kgs.ku.edu/Extension/fossils/massExtinct.html</ref> Recovery from the Permian-Triassic extinction event was protracted; land ecosystems took 30M years to recover,<ref name="SahneyBenton2008RecoveryFromProfoundExtinction">{{cite journal | url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2596898/?tool | author=Sahney, S. and Benton, M.J. | year=2008 | title=Recovery from the most profound mass extinction of all time | journal=Proceedings of the Royal Society: Biological | doi=10.1098/rspb.2007.1370 | volume = 275 | pages = 759–65|format=PDF | pmid=18198148 | issue=1636 | pmc=2596898}}</ref> and marine ecosystems took even longer.{{r|Baez2006}}</small>
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| [[File:Perleidus.jpg|140px]]
Riga 611 ⟶ 586:
| ''[[Pholidophorus]]'' was an [[extinct]] genus of [[teleost]], around {{convert|40|cm|in}} long, from about 240–140 Ma. Although not closely related to the modern [[herring]], it was somewhat like them. It had a single [[dorsal fin]], a symmetrical tail, and an [[anal fin]] placed towards the rear of the body. It had large eyes and was probably a fast swimming predator, hunting [[plankton]]ic [[crustacean]]s and smaller fish.{{sfn|The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals|1999|p=38–39}} A very early [[teleost]], ''Pholidophoris'' had many primitive characteristics such as [[ganoid scale]]s and a [[Vertebral column|spine]] that was partially composed of [[cartilage]], rather than [[bone]].{{sfn|The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals|1999|p=38–39}}
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| colspan="3" style="line-height:16px; background:#dddddd;"| <small>The Triassic ended with the [[Triassic–Jurassic extinction event]]. About 23% of all families, 48% of all genera (20% of marine families and 55% of marine genera) and 70% to 75% of all species went extinct.<ref name="ucr">{{cite web|url=http://math.ucr.edu/home/baez/extinction |title=extinction |publisher=Math.ucr.edu |date= |accessdate=2008-11-09}}</ref> Non-dinosaurian archosaurs continued to dominate aquatic environments, while [[Diapsid#Taxonomy|non-archosaurian diapsids]] continued to dominate marine environments.<ref name="ucr" /></small>
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| colspan="3" style="text-align:center; background:#ddf8f8;"| [[
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| [[File:Leedsichthys
| ''[[Leedsichthys]]''
| During the [[Jurassic period]], the primary vertebrates living in the seas were [[fish]] and marine [[reptile]]s. The latter include [[ichthyosaur]]s who were at the peak of their diversity, [[plesiosauria|plesiosaurs]], [[pliosaur]]s, and marine [[crocodilia|crocodiles]] of the families [[Teleosauridae]] and [[Metriorhynchidae]].<ref>Motani, R. (2000), Rulers of the Jurassic Seas, Scientific American vol.283, no. 6</ref> Numerous [[turtle]]s could be found in lakes and rivers.<ref name=nws>{{citation
Riga 641 ⟶ 616:
The family [[Ichthyodectidae]] (literally "fish-biters") was a family of marine [[actinopterygii|actinopterygian]] fish. They first appeared 156 Ma during the [[Late Jurassic]] and disappeared during the K-Pg extinction event 65 Ma. They were most diverse throughout the Cretaceous period. Sometimes classified in the primitive [[bony fish]] [[order (biology)|order]] [[Pachycormiformes]], they are today generally regarded as members of the "bulldog fish" order Ichthyodectiformes in the far more advanced [[Osteoglossomorpha]]. Most ichthyodectids ranged between 1 and 5 meters (3–15 ft) in length. All known [[taxa]] were [[predator]]s, feeding on smaller fish; in several cases, larger Ichthyodectidae preyed on smaller members of the family. Some species had remarkably large teeth, though others, such as ''[[Gillicus arcuatus]]'', had small ones and sucked in their prey. The largest Xiphactinus was 20 feet long, and appeared in the Late Cretaceous (below).
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| [[File:
| ''[[
|
La loro lentissima evoluzione è dovuta ad alcuni fattori fondamentali: un lungo intervallo generazionale, un'ampia tolleranza alle diverse temperature e salinità delle acque, la mancanza di predatori a causa delle loro grosse dimensioni e l'abbondanza di prede nel loro ambiente.
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| [[File:
| ''[[Enchodus]]''
|
Riga 654 ⟶ 630:
| [[File:Xiphactinus audax fossil.jpg|140px]]
| ''[[Xiphactinus]]''
|
▲"One Cretaceous fish, ''[[Xiphactinus]]'', grew to more than 4.5 metres (15 feet) and is the largest known [[teleost]]."<ref>Rafferty, John P (2010) [http://books.google.co.nz/books?id=kFd-1DApcRYC&pg=PA219&dq=%22Cretaceous+fish%22+OR+%22Cretaceous+fishes%22&hl=en&sa=X&ei=HkrtUNPWHonKlAWshYGQBQ&ved=0CKEBEOgBMBM#v=onepage&q=%22Cretaceous%20fish%22%20OR%20%22Cretaceous%20fishes%22&f=false ''The Mesozoic Era: Age of Dinosaurs''] Page 219, Rosen Publishing Group. ISBN 9781615301935.</ref>
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| colspan="3" style="line-height:16px; background:#dddddd;"| <small>The end of the Cretaceous was marked by the [[Cretaceous–Paleogene extinction event]] (K-Pg extinction). There are substantial fossil records of [[Gnathostomata|jawed]] [[fish]]es across the K–T boundary, which provides good evidence of extinction patterns of these classes of marine vertebrates. Within [[Chondrichthyes|cartilaginous fish]], approximately 80% of the [[shark]]s, [[Rajiformes|rays]], and [[skate]]s families survived the extinction event,<ref name="MacLeod">{{cite journal|author=MacLeod, N, Rawson, PF, Forey, PL, Banner, FT, Boudagher-Fadel, MK, Bown, PR, Burnett, JA, Chambers, P, Culver, S, Evans, SE, Jeffery, C, Kaminski, MA, Lord, AR, Milner, AC, Milner, AR, Morris, N, Owen, E, Rosen, BR, Smith, AB, Taylor, PD, Urquhart, E & Young, JR|title=The Cretaceous–Tertiary biotic transition|year=1997|journal=Journal of the Geological Society|volume=154|issue=2|pages=265–292|url=http://findarticles.com/p/articles/mi_qa3721/is_199703/ai_n8738406/print|doi=10.1144/gsjgs.154.2.0265}}</ref> and more than 90% of [[teleostei|teleost fish]] (bony fish) families survived.<ref>{{cite book |last=Patterson|first=C |year=1993 |title=Osteichthyes: Teleostei. In: The Fossil Record 2 (Benton, MJ, editor) |publisher=Springer |pages=621–656 |isbn=0-412-39380-8}}</ref> There is evidence of a mass kill of bony fishes at a fossil site immediately above the K–T boundary layer on [[Seymour Island]] near Antarctica, apparently precipitated by the K–Pg extinction event.<ref>{{cite journal |title=Discovery of fish mortality horizon at the K–T boundary on Seymour Island: Re-evaluation of events at the end of the Cretaceous |author=Zinsmeister WJ |date=1 May 1998|url=http://jpaleontol.geoscienceworld.org/cgi/content/abstract/72/3/556?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=1&author1=zinsmeister&andorexacttitle=and&field_name=fulltext&searchid=1&FIRSTINDEX=0&sortspec=relevance&fdate=7/1/1927&tdate=7/31/2007&resourcetype=HWCIT |accessdate=2007-08-27 |journal=Journal of Paleontology |volume=72 |issue=3 |pages=556–571 }}</ref> However, the marine and freshwater environments of fishes mitigated environmental effects of the extinction event.<ref name="Robertson">{{cite journal |title= Survival in the first hours of the Cenozoic |author=Robertson DS, McKenna MC, Toon OB, Hope S, Lillegraven JA |journal=GSA Bulletin |year=2004 |volume=116 |issue=5–6 |pages=760–768 |doi=10.1130/B25402.1 |url=http://www.ugcs.caltech.edu/~presto/cenozoic.pdf |format=PDF|accessdate=2007-08-31}}</ref></small>
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! rowspan=3 style="background:
| colspan="3" style="text-align:center; background:#ddf8f8;"| [[Cenozoic Era]] (65 Ma to present): The current era has seen great diversification of bony fishes. Over half of all living vertebrate species (about 32,000 species) are fishes (non-tetrapod craniates), a diverse set of lineages that inhabit all the world's aquatic ecosystems, from snow minnows (Cypriniformes) in Himalayan lakes at elevations over 4,600 metres (15,000 feet) to flatfishes (order Pleuronectiformes) in the Challenger Deep, the deepest ocean trench at about 11,000 metres (36,000 feet). Fishes of myriad varieties are the main predators in most of the world’s water bodies, both freshwater and marine.
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Riga 670 ⟶ 642:
| ''[[Amphistium]]'' is a 50-million-year-old fossil fish which has been identified as an early relative of the flatfish, and as a transitional fossil.<ref name="NaEvo">{{cite news | url=http://news.nationalgeographic.com/news/2008/07/080709-evolution-fish.html | title=Odd Fish Find Contradicts Intelligent-Design Argument | publisher=[[National Geographic Society|National Geographic]] |date= July 9, 2008 | first= | last= | accessdate =2008-07-17}}</ref> In a typical modern flatfish, the head is asymmetric with both eyes on one side of the head. In ''Amphistium'', the transition from the typical symmetric head of a vertebrate is incomplete, with one eye placed near the top of the head.<ref>{{cite journal|author=Matt Friedman|title=The evolutionary origin of flatfish asymmetry|journal=Nature|volume=454|number=7201|date=2008-07-10|pages=209–212|doi= 10.1038/nature07108|pmid=18615083|issue=7201}}</ref>
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| [[File:
| ''[[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]], but was much larger with fossil lengths reaching {{convert|20.3|m|ft}}.<ref name="GWB" /> Found in all oceans<ref name="AN">{{Cite journal|last=Pimiento|first=Catalina|coauthors=Dana J. Ehret, Bruce J. MacFadden, and Gordon Hubbell|title=Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama|journal=PLoS ONE|volume=5|issue=5|pages=e10552|publisher=PLoS.org|___location=Panama|date=May 10, 2010|pmid=20479893|url=http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0010552|pmc=2866656|doi=10.1371/journal.pone.0010552|accessdate=12 May 2010|editor1-last=Stepanova|editor1-first=Anna|bibcode = 2010PLoSO...510552P }}</ref> it was one of the largest and most powerful predators in vertebrate history,<ref name="GWB">{{cite journal|last=Wroe|first=S.|coauthors= Huber, D. R. ; Lowry, M. ; McHenry, C. ; Moreno, K. ; Clausen, P. ; Ferrara, T. L. ; Cunningham, E. ; Dean, M. N. ; Summers, A. P.|title=Three-dimensional computer analysis of white shark jaw mechanics: how hard can a great white bite?|url=http://www.bio-nica.info/Biblioteca/Wroe2008GreatWhiteSharkBiteForce.pdf|journal=Journal of Zoology|volume=276|issue=4|pages=336–342|year= 2008|doi=10.1111/j.1469-7998.2008.00494.x}}</ref> and probably had a profound impact on [[marine life]].<ref name="LV">{{Cite journal|doi=10.1038/nature09067|last=Lambert|first=Olivier|coauthors=Giovanni Bianucci, Klaas Post, Christian de Muizon, Rodolfo Salas-Gismondi, Mario Urbina and Jelle Reumer|title=The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru|journal=Nature|volume=466|issue=7302|pages=105–108|___location=Peru|date=1 July 2010|url=http://www.nature.com/nature/journal/v466/n7302/full/nature09067.html|pmid=20596020|bibcode = 2010Natur.466..105L }}</ref>
|}
==Pesci preistorici==
{{Vedi anche|Elenco dei pesci preistorici}}
I pesci preistorici sono pesci estinti conosciuti soltanto tramite ritrovamenti [[fossili]]. Considerati tra i [[vertebrati]] più antichi oggi conosciuti, comprendono il primo pesce estinto, vissuto tra il [[Cambriano]] e il [[Terziario]]. La branca della [[paleontologia]] che studia i pesci preistorici si chiama paleoittiologia. Alcune specie viventi di pesci sono classificati come pesci preistorici, come il [[celacanto]] che è anche un [[fossile vivente]], a causa della loro rarità attuale e somiglianza con forme preistoriche estinte.
{{clear}}
==
[[File:Pacific hagfish Myxine.jpg|thumb|right|The jawless [[hagfish]] is a living fossil which has not essentially changed for 300 million years.<ref>[http://www.ucmp.berkeley.edu/vertebrates/basalfish/myxini.html Myxini] - University of California Museum of Paleontology</ref>]]
Riga 727 ⟶ 688:
{{clear}}
==
[[File:Miguasha affleurement 2.jpg|thumb|right|[[Miguasha National Park]]: outcrop of Devonian beds rich in fossil fish]]
{{see also|List of fossil sites}}
Riga 767 ⟶ 728:
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==Collezioni di fossili==
Some notable fossil fish collections.
Riga 776 ⟶ 737:
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==Paleoittiologi==
La paleoittiologia è la scienza che studia i pesci preistorici. Nella lista sottostante sono elencati i paleoittiologi che con i loro studi hanno contribuito a svelare i segreti di queste antiche forme di vita.
{{div col|3}}
* [[Louis Agassiz]]
Riga 819 ⟶ 778:
{{div col end}}
==
* [[Comparative anatomy]]
* [[List of examples of convergent evolution#Fish|Convergent evolution in fish]]
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