Ichthyostega - uhlobo lwezilwane ezingasekho, ezihlobene kakhulu nama-tetrapods (ama-vertebrate asemilenzeni amane). Kutholakala njengedwala lezinto zasendulo empumalanga yeGreenland yesikhathi esedlule seDevonia cishe eminyakeni eyizigidi ezingama-370 edlule. Yize i-Ichthyostegus kuvame ukubizwa ngokuthi "ama-tetrapods" ngenxa yezitho neminwe yayo, kwakuyizinhlobo eziyisisekelo "zakudala" kune-tetrapods yangempela yomqhele, futhi ingabizwa ngokunembile ngokuthi yi-stegocephalic noma i-stem tetrapod.
Umsuka wezinhlobo nencazelo
Isithombe: Ichthyostega
Ichthyostega (kusuka ophahleni lwesiGrikhi "uphahla lwenhlanzi") luhlobo lwakuqala oluvela emgqonyeni wama-tetrapodomorphs abephila esikhathini esedlule saseDevonia. Kwakungenye yama-vertebrate ezinemilenze emine yokuqala etholakala ezinsaleleni. U-Ichthyostega wayenamaphaphu nezitho ezamsiza ekuhambiseni amanzi angajulile emaxhaphozini. Ngokwesakhiwo nemikhuba, akubhekwa njengelungu leqiniso leqembu, ngoba ama-amphibians okuqala anamuhla (amalungu eqembu leLissamphibia) avele esikhathini seTriassic.
Ividiyo: Ichthyostega
Iqiniso elithakazelisayo: Izinhlobo ezine zachazwa ekuqaleni kwachazwa nohlobo lwesibili, i-Ichthyostegopsis. Kepha ucwaningo oluqhubekayo lwembula ubukhona bezinhlobo ezintathu ezinokwethenjelwa ezincike ebungako bogebhezi futhi ezihambisana nezinhlaka ezintathu ezihlukene.
Kuze kutholakale amanye ama-stegocephal okuqala nezinhlanzi ezihlobene kakhulu ngasekupheleni kwekhulu lama-20, i-Ichthyostega yiyona kuphela eyatholakala njengemivubukulo yesikhashana phakathi kwezinhlanzi nama-tetrapods, ehlanganisa zombili izinhlanzi nama-tetrapods. Ucwaningo olusha lukhombise ukuthi ubene-anatomy engajwayelekile.
Ngokwesiko, i-Ichthyostega imelela isigaba se-paraphyletic se-trunk tetrapods zakudala kakhulu, ngakho-ke asihlukaniswa ngabaphenyi abaningi banamuhla njengokhokho wezinhlobo zesimanje. Ukuhlaziywa kwe-phylogenetic kukhombisile ukuthi ichthyosteg iyisixhumanisi esiphakathi phakathi kwamanye ama-tetrapods ama-stegocephalic akudala. Ngo-2012, uSchwartz wahlanganisa umuthi wokuziphendukela kwemvelo wama-stegocephals okuqala.
Ukubukeka nezici
Isithombe: Ibukeka kanjani ichthyostega
Ichthyostega yayicishe ibe imitha elilodwa nengxenye ubude futhi yayinomphetho omncane we-dorsal onqenqemeni lomsila. Umsila ngokwawo wawunochungechunge lwamathambo asekela okujwayelekile kwezinsizakalo zomsila ezitholakala ezinhlanzini. Ezinye izinto eziqhubekayo kuma-vertebrate angaphambilini asemanzini zifaka isifonyo esifushane, ukuba khona kwethambo langaphambi kwesifunda esifundeni esihlathini esisebenza njengengxenye yamagill, nezikali eziningi ezincane emzimbeni. Izici ezithuthukile ezijwayelekile kuma-tetrapods zifaka phakathi uchungechunge lwamathambo aqinile asekela izitho zenyama, ukungabi namaphaphu nezimbambo eziqinile.
Iqiniso elithakazelisayo: I-Ichthyostega nezihlobo zayo bamele amafomu asethuthuke kakhulu kune-Eusthenopteron yasemanzini, futhi abonakala eseduze nolayini wokuziphendukela kwemvelo oholela kumatetrapod okuqala emhlabeni.
Isici esiphawuleka kakhulu samathambo e-axial e-ichthyosteg izinga izimbambo ezihlangana ngalo. Ubambo olulodwa lwangemuva lungahlangana nezimbambo ezintathu noma ezine ezingemuva, lwenze i- "corset" emise umgqomo nxazonke zomzimba. Lokhu kusikisela ukuthi isilwane besingakwazi ukugoba umzimba waso ohlangothini ngenkathi sihamba noma sibhukuda. Ama-vertebrae ayengeyona inkinga, kepha imithambo yezinzwa yayine-zygapophyses evelele kakhulu.
Kungacatshangwa ukuthi isilwane sihambe kakhulu njengomphumela we-dorsoventral flexion kunangesikhathi sokuhamba okujwayelekile kwe-lateral. Izindonga ezingaphambili zazingase zisetshenziselwe ukudonsela isilwane phambili bese sigobisa indawo engaphambi kokuqina ukuze kuqiniswe ngemuva. Imilenze yangemuva yayiqukethe insikazi emfushane, ejiyile ene-flange enkulu ne-adductor deep intercondylar fossa.
I-tibia enkulu, ecishe ibe ngama-quadrangular kanye ne-fibula emfushane yacaba. I-intermediate enkulu ne-fibula yayihlanganisa iningi lamathambo amaqakala. Isifanekiso esilondolozwe kahle, esiqoqwe ngo-1987, sikhombisa isethi ephelele yeminwe eyisikhombisa, emithathu emincane onqenqemeni oluholayo nemine egcwele emuva.
Uhlala kuphi Ichthyostega?
Isithombe: Ichthyostega emanzini
Izinsalela ze-ichthyosteg zitholakale eGreenland. Yize uhla oluqondile lwezinhlobo lungaziwa, kungacatshangwa ukuthi ichthyostegs kwakuyizakhamuzi zasenyakatho yezwe. Futhi bahlala emanzini amanje e-Atlantic nase-Arctic Ocean. Isikhathi se-Devonia sibonakala ngesimo sezulu esifudumele futhi, mhlawumbe, ukungabikho kwezinguzunga zeqhwa. Ukwehluka kwamazinga okushisa ukusuka enkabazwe kuya ezigxotsheni kwakungekukhulu njengoba kunjalo nanamuhla. Isimo sezulu naso besomile kakhulu, ikakhulukazi ngasenkabazwe, lapho isimo sezulu esome kakhulu khona.
Iqiniso elithakazelisayo: Ukwakhiwa kabusha kwamazinga okushisa asolwandle asezindaweni ezishisayo kuthatha isilinganiso esingu-25 ° C kwi-Early Devonian. Izinga leCarbon dioxide lehle kakhulu ngesikhathi seDevonia, njengoba ukungcwatshwa kwamahlathi asanda kwakhiwa kwakhipha ikhabhoni emkhathini kuyiziduli. Lokhu kubonakala enkabeni yeDevonia ngokupholisa kwamazinga okushisa kuze kufike ku-5 ° C. I-Late Devonian ibonakala ngokunyuka kwezinga lokushisa liye ezingeni elilingana ne-Early Devonian.
Ngaleso sikhathi, kwakungekho ukwanda okuhambisanayo kokugxila kwe-CO², kepha isimo sezulu sezwekazi sanda (njengoba kukhombisa amazinga aphezulu okushisa). Ngaphezu kwalokho, ubufakazi obuningi, njengokusatshalaliswa kwezitshalo, kukhomba ekufudumaleni kweLate Devonia. Kukule nkathi lapho kutholwa khona izinsalela zeminyaka. Kungenzeka ukuthi ichthyostegs yaqhubeka enkathini elandelayo yeCarboniferous. Ukunyamalala kwabo okuqhubekayo kungenzeka kuhlotshaniswa nokwehla kwezinga lokushisa ezindaweni abahlala kuzo.
Ngalesi sikhathi, isimo sezulu sithinte izidalwa ezivelele ezixhotsheni zamakhorali, ama-microbes kwakuyizinto eziphilayo eziyinhloko ezakha amadwala ngezikhathi ezifudumele, kanti amakhorali nama-stromatoporoid adlala indima enkulu ngezikhathi ezinzima. Ukufudumala ngasekupheleni kweDevonia kungenzeka kube nomthelela ekunyamalaleni kwama-stromatoporoids.
Manje uyazi lapho ichthyosteg itholakale khona. Ake sibone ukuthi udleni.
Yini edliwe yi-Ichthyostega?
Isithombe: Ichthyostega
Iminwe ye-ichthyosteg yayingagobekile kahle, futhi uhlelo lwemisipha lwalubuthakathaka, kepha isilwane, ngaphezu kwemvelo yasemanzini, sesivele singahamba ezindaweni ezinamanzi ezinamanzi. Uma sibheka ukuzilibazisa kwe-ichthyostega ngamaphesenti, khona-ke ama-70-80% wesikhathi anqobe ngayo isici samanzi, futhi sonke isikhathi wazama ukuqonda umhlaba. Imithombo yawo yokudla eyinhloko kwakuyizinhlanzi, izinhlanzi zasolwandle, mhlawumbe nezitshalo zasolwandle. Izinga lolwandle eDevonia ngokuvamile laliphezulu.
Amafauna asolwandle abesabuswa yi:
- ama-bryozoans;
- ama-brachiopods ahlukahlukene futhi aningi;
- gederellids ongaqondakali;
- ama-microconchids;
- izilwane ezinjengezimbali ze-crinoids, naphezu kokufana kwazo nezimbali, zaziziningi;
- ama-trilobites ayesavamile kakhulu.
Kungenzeka ukuthi i-Ichthyostega idle ezinye zalezi zinhlobo. Phambilini ososayensi bebehlobanisa ichthyostega nokuvela kwama-tetrapods emhlabeni. Kodwa-ke, kungenzeka ukuthi, yahamba emhlabathini isikhathi esifushane kakhulu, yabuyela emanzini. Ubani wama-vertebrate asendulo owaba ngumvunduli wangempela womhlaba okusazobonakala.
Ngesikhathi samaDevoniya, impilo yayisigcwele amathafa ngenkathi kwenziwa ikoloni lomhlaba. Amahlathi ama-moss ama-silurian kanye namata wamagciwane ekuqaleni kwesikhathi afaka izitshalo zezimpande zakudala ezakha inhlabathi yokuqala engazweli kanye nama-arthropods njengezimbuzane, ofezela, ama-trigonotarbids nama-millipedes. Yize ama-arthropod avele emhlabeni ngaphambili kunakuqala kwe-Devonia, futhi ukuba khona kwezinsalela ezifana ne-Climactichnites kusikisela ukuthi i-arthropods yasemhlabeni kungenzeka ukuthi yavela kudala njenge-Cambrian.
Izinsalela zokuqala zezinambuzane ezingaba khona zavela ekuqaleni kwe-Devonia. Idatha yokuqala ye-tetrapod yethulwe njengemikhondo yezinsalela zamathambo emachwebeni angajulile e-offshore carbonate platform / eshalofini ngesikhathi seMiddle Devonian, yize lezi zinyathelo sezike zabuzwa futhi ososayensi bacubungule umkhondo wokondla izinhlanzi. Zonke lezi zimila nezilwane ezikhula ngokushesha bekungaba umthombo wokudla we-Ichthyosteg.
Izici zobuntu nendlela yokuphila
Isithombe: Extchct Ichthyostega
Ubudala besilwane babekwa eminyakeni eyizigidi ezingama-370 futhi babhalwa esikhathini seDevonia. Ichthyostega ingenye yama-tetrapods amadala kakhulu aziwayo. Ngenxa yezici zayo, ezibandakanya izici zombili izinhlanzi nezilwane eziphila emanzini, i-Ichthyostega isebenze njengobufakazi obubalulekile bokubamba nokuqina kombono wemfundiso yokuziphendukela kwemvelo.
Iqiniso elithakazelisayo: Elinye lamaqiniso apholile kakhulu mayelana ne-ichthyosteg akukhona ukuthi unezinyawo ezine-webbed, kepha ukuthi wakwazi ukuphefumula umoya - okungenani okwesikhashana. Kodwa-ke, ngaleli khono elimangalisayo, kungenzeka ukuthi akazange achithe isikhathi esiningi emhlabeni. Lokhu kungenxa yokuthi yayinzima impela futhi imilenze yakhe yayingaqinile ngokwanele ukuhambisa umzimba wakhe oqinile.
Izingalo zangaphambili ze-Ichthyostega zibonakala zisinda futhi ingalo yehlulekile ukunweba ngokugcwele. Ukulingana kophawu lwendlovu yisifaniso esiseduze kakhulu se-anatomical phakathi kwezilwane eziphilayo. Mhlawumbe u-Ichthyostega wakhuphuka emabhishi anamadwala, ehambisa izitho zangaphambili ngokufana futhi ehudula izitho zangemuva ngazo.
Isilwane besingakwazi ukujwayela ama-tetrapod gaits, ngoba izingalo zangaphambili bezingenalo uhla oludingekayo lokunyakaza kokujikeleza. Kodwa-ke, indlela yokuphila ngqo ye-Ichthyostega ayikacaci ngenxa yezici zayo ezingavamile.
Isakhiwo senhlalo nokuzala
Isithombe: Ichthyostegai
Kukholakala ukuthi ichthyostegs nezihlobo zakhe bachitha isikhathi bethamela ilanga ukukhuphula izinga lokushisa komzimba. Babuye babuyela emanzini ukuyophola, ukuzingela ukudla, nokuzala. Indlela yabo yokuphila ibidinga izandulela eziqinile zokudonsa okungenani umphambili emanzini, kanye nembambo nomgogodla oqinile ukuzisekela, ukushuka esiswini sabo njengezingwenya zesimanje.
Iqiniso elithakazelisayo: Ichthyostegs baba okhokho bamagatsha amabili amakhulu ama-amphibians, ahluke ngesakhiwo sogebhezi nezitho zomzimba. Esikhathini seLate Devonian, kwavela ama-labyrinthodonts. Ngaphandle, zazibukeka njengezingwenya noma ama-salamanders. Namuhla, amakhulu ezinhlobo zama-labyrinthodonts ayaziwa, ahlala emahlathini nasemifuleni.
Amanzi ayeyimfuneko ephoqelekile ye-ichthyostega, ngoba amaqanda ama-tetrapods okuqala omhlaba ayengakwazi ukuphila ngaphandle kwamanzi, ngakho-ke ukuzala kwakungeke kwenzeke ngaphandle kwemvelo yasemanzini. Amanzi ayedingeka futhi kwizibungu zawo kanye nokukhulelwa kwangaphandle. Kusukela lapho, amagciwane omgogodla amaningi asezindaweni ezimbili akha izindlela ezimbili zokukhulelwa kwangaphakathi. Kungaba okuqondile, njengoba kubonakala kuwo wonke ama-amniotes nakuma-amphibiya ambalwa, noma ngokungaqondile kwabaningi bama-salamanders, bebeka i-spermatophore phansi, bese iphakanyiswa ngabesifazane.
Izitha zemvelo ze-ichthyosteg
Isithombe: Kubukeka kanjani ichthyostega
Yize izingalo zangaphambili zingazange zakhiwe kabusha ngenxa yokuthi azitholakalanga kumathambo wesilwane aziwayo, kukholakala ukuthi lezi zithasiselo zazinkulu kunezingemuva zesilwane. Ososayensi bakholelwa ukuthi ngale ndlela ichthyostega ihambise umzimba wayo emanzini isiwa emhlabathini.
Kubukeka sengathi i-locomotion, ewumsebenzi wokunyakaza okungokwemvelo kohlelo lwezicubu zomzimba, ibikhombisa ukwehluka okuncane kakhulu kokuhamba ngaphansi kwamanzi kusetshenziswa inhlanganisela yokunyakaza komsila nomlenze. Kulokhu, imilenze yayisetshenziselwa ngokukhethekile ukudlula kwemisipha edabula ngaphansi kwezikhukhula zezitshalo zasemanzini.
Iqiniso elithakazelisayo: Yize ukunyakaza komhlaba kwakwenzeka, i-Ichthyostega yavela kakhulu ngokuphila emanzini, ikakhulukazi ngesikhathi sesigaba sabantu abadala sempilo yayo. Kwakungavamisile ukuhamba emhlabeni, futhi ubukhulu obuncane bezinsizwa, obabuzivumela ukuthi zihambe kalula phezu komhlaba, abuzange busetshenziselwe ukufuna ukudla ngaphandle kwendawo yamanzi, kepha njengendlela yokugwema ezinye izilwane ezinkulu ezidliwayo kuze kube yilapho zikhula ngokwanele ukuba zibe yisisulu sazo.
Ososayensi bathi intuthuko esezingeni lomhlaba inikeze izilwane ukuphepha okukhulu ezilwaneni ezidla ezinye, ukuncintisana okuncane kwezilwane, kanye nezinzuzo ezithile zezemvelo ezingatholakali emanzini, njengokuhlushwa komoya-mpilo nokulawulwa kwamazinga okushisa - okusho ukuthi izitho ezisakhulayo nazo ziyavumelana nokuziphatha ingxenye yesikhathi sabo ephuma emanzini.
Kodwa-ke, ucwaningo lukhombisile ukuthi ama-sarcopterygs athuthukise imilenze efana ne-tetrapod efanelekile ukuhamba kahle ngaphambi kokuya ezweni. Lokhu kusikisela ukuthi sebekwazile ukuhamba phezu komhlaba ngaphansi kwamanzi ngaphambi kokuwelela emhlabathini.
Inani labantu kanye nesimo sezinhlobo
Isithombe: Ichthyostega
Ichthyostega iyinhlobo engasekho isikhathi eside kakhulu. Ngakho-ke, namuhla kunzima ukwahlulela ukuthi abantu base-Ichthyostega babesabalele kangakanani eMhlabeni. Kodwa njengoba izinsalela zazitholakala kuphela eGreenland, inani labantu cishe lalingelutho. Lezi zilwane zaziphila esikhathini esinzima kakhulu. Ukuqothulwa okukhulu kwenzeke ekuqaleni kwesigaba sokugcina seDevoniya, izilo zamadiphozidi aDemennian kukhombisa ukuthi cishe eminyakeni eyizigidi ezingama-372.2 edlule, lapho zonke izinsalela zezinhlanzi zasendulo, ngaphandle kwama-heterostracic psammosteids, zanyamalala ngokuzumayo.
Ukuqothulwa kweLate Devonia kwaba ngesinye sezigameko ezinhlanu ezinkulu zokuqothulwa komhlaba emlandweni wempilo yoMhlaba, futhi kwakudlange kakhulu kunomcimbi ofanayo wokuqothulwa okuvale iCretaceous. I-Devonian Extinction Crisis ithinte kakhulu umphakathi wasolwandle futhi ithinte ngokukhethekile izinto eziphila emanzini angajulile emanzini afudumele. Iqembu elibaluleke kakhulu elihlushwe yilo mcimbi wokuqothulwa kwakungabakhi bezinhlelo ezinkulu zamatshe.
Phakathi kwamaqembu olwandle athinteka kakhulu bekukhona:
- ama-brachiopods;
- ama-amoni;
- ama-trilobites;
- ama-akritarchs;
- inhlanzi ngaphandle kwemihlathi;
- ama-conodonts;
- wonke ama-placoderms.
Izitshalo zomhlaba kanye nezinhlobo zamanzi ahlanzekile njengokhokho bethu be-tetrapod bezingathinteki ngomcimbi wokuqothulwa kweLate Devonia. Izizathu zokuqothulwa kwezinhlobo zeLate Devonian azikaziwa, futhi zonke izincazelo zihlala ziqagela. Kulezi zimo ichthyostega yasinda yanda. Imithelela ye-Asteroid yashintsha umhlaba futhi yathinta abahlali bayo.
Usuku lokushicilelwa: 08/11/2019
Idethi ebuyekeziwe: 09/29/2019 ngo-18: 11
