
alattokonchide

permian kaalaghattatthinte aadyakaalam muthal madhyakalam vare jeevichirunna charithraatheethakaalatthe vamshanasham sambhavicha oru kudumbamaanu alattokonchide. dorsoventral dishayil shakthamayi compress cheythirikkunna shell aanu alattokonchideyil ulppedunna janussinte savisheshatha. chila enangal athra neelamulla valia valippathil ethi. eee kudumbatthile chila jeevajaalangalkk keemosinthattik bakteeriyakalil ninnaan oorjjam labhichathennu anumaanikkappedunnu.
sambhavam.
alattokonchideyude phoosil rekhakal aadyakaala permian muthal madhya permian vare ariyappedunnu. croatia, tunisia, omaan, afgaanisthaan, iraan, thayland, maleshya, phillippines, jappan, alasca, thekkan chaina thudangiya vyaapakamaayi verthiricha pradeshangalil aazhamillaatha samudra kaarbanettukalil iva kaanapedunnu.
charithram.
1968-ll, paleantologist shikama tokiyoyude perilulla jappanil ninnulla "shikamaya acasacensis" vivarikkappedunnu, ennaal athinte savisheshamaaya aakruthiyum shakala phoosil samrakshanavum kaaranam, ithine yadhaarthathil animalia "inserta sedis" ennu tharamthirichirunnu. 1973ll roopeekaricha alattokonchide kudumbatthil "alattokoncha" januss ulppedunnu.
roopaghadana.
shikamaya perackensis" enna roopathil, shell dorsal ventral dishayil compress cheyyukayum munvashath-posteeriyar dishayil neelukayum cheiyunnu. shellinte pinn pakuthiyil valare compress cheytha cross sekshanulla chirakukal polulla paranna flanchukal maathrame adangiyittulloo. corculum cardisa" polulla aadhunika cardidinode aduthaanu ithinte shareeraghadana savisheshatha.
palio ekkolaji.
eee kudumbatthile oru janussaaya "shikamaya" aadhunika "corculum cardisa" pole, jeevanopadhikkaayi photosynthetic allengil keemosinthattik sookshumaanukkalumaayi sahajeevana bandhangal roopeekarichathaayi sidhaanthamundu. ithinu oru ardhasuthaarya shell paali undennum avayude opttimal aazham euphotic soninte thaazhathe bhaagathaanennum aadyam vishwasichirunnu; eee mekhala aalgakalkk anuyojyamaanu, athinaal photosynthetic sookshumaanukkalumaayulla bandham pinthunaykkunnu. ennirunnaalum, pilkkala padanangal kaanikkunnath "shikamaya" yude shell athaaryamaanennu, muun sidhaantham nirasikkunnu. ennamayamullathum manamukthavumaya karutha vaakkston, chunnaambu madstoon facies ennivayil ninnaan alattokanchidukal ariyappedunnathu. aadhunika lucinid bivalve pole aazhathilulla avashishta paalikalil ninnu hydrajan sulfide adangiyirikkunna samudrajalam mrugathinte mriduvaaya tissukkullil keemosinthattik bakteeriyakale poshippikkunnathinaayi "shikamaya" pump cheythirikkaamennu ithu soochippikkunnu.
shikamaya acasacensis" ennathinte valarchaa reethi ariyappedunnu avaa valarumbol, shareera arra vardhippikkunnathinu neelamulla pinbhaagathe shell vikasippikkunnu.
vamshanaashabheeshani.
gwadaloopian kaalaghattatthinte avasaanathil alattokanchidukal vamshanasham sambhavichu, orupakshe kaapittaaniyan kootta vamshanasha sambhavam kaaranam. eee sambhavam samudrajalathinte thapanilayil ganyamaaya ettakkurachilukal, pettennulla samudra acidification, samudra anoxia ennivaykku kaaranamaayi. avaykku prakaashasamsleshitha sookshumaanukkalumaayi sahavarthithvam undenna sidhaanthathinte adisthaanathil, samudrajalathinte thaalkkaalika thaapanila kurayunnathu (kamura sambhavathil) prakaashasamsleshitha sookshumaanukkale kollukayum ithu prakaashasamsleshitha samvidaanangale apaharikkukayum vamshanaashathin kaaranamaakukayum cheythu. ennirunnaalum, pilkkala patanam aaa sidhaanthathe chodyam cheythu, kaaranam kamura sambhavam yadhaarthathil sambhavichathaano ennu vyakthamalla, udaaharanathinu conodont appaattait ooksijan isotope recordukalumaayi poruthappedaattha kalavastha thanupp. appozhum ettavum puthiya gwadaloopian muthal aadyakaala loppingian vareyulla edavelayil kadaljalathinte thaapanilayile ganyamaaya ettakkurachilukal alattokanchidukale kollan paryapthamaayirunnu. samudrathile acidification carbonate saachureshan kurayunnathum samudrajalathile hypoxic avasthayum alattokonchidukalude vamshanaashathin kaaranamaayi kanakkaakkappedunnu.

