Dunkleosteus: Imodzi mwa shaki zazikulu komanso zowopsa zaka 380 miliyoni zapitazo

Dzina la Dunkleosteus ndi kuphatikiza kwa mawu awiri: 'osteon' ndi liwu lachi Greek lotanthauza fupa, ndipo Dunkle adatchedwa David Dunkle. Katswiri wina wodziwika bwino wa zinthu zakale wa ku America yemwe kafukufuku wake nthawi zambiri ankangoganizira za zokwiriridwa pansi za nsomba ndipo amadziwika kwambiri chifukwa cha ntchito yake ya vertebrate paleontology ku Cleveland Museum of Natural History.

dunkleosteus
Chigaza chomangidwanso, Vienna Natural History Museum. © Mawu Azithunzi: Wikimedia Commons

Placoderm iyi imadziwika kuti imadya chilichonse, kapena zinthu zambiri, ndipo imakhala yachangu komanso yamphamvu kwambiri. Dunkleosteus ndi imodzi mwa ma placoderms akuluakulu omwe adakhalapo ndipo amanenedwa kuti anali owopsya kwambiri pa nthawi ya Late Devonian, yomwe nthawi zambiri imadziwika kuti 'Age of Fishes.'

Dunkleosteus amadziwika kuti amalemera mpaka 8000 lb (3600 kg) ndipo amakhala ndi kutalika mpaka 346 mu (8.8 m). D. terrelli, D. Belgicus, D. denisoni, D. marsaisi, D. magnificus, D. missouriensis, D. newberryi, D. amblyodoratus, ndi D.raveri ndi mitundu 10 ya Dunkleosteus.

Dunkleosteus: Imodzi mwa shaki zazikulu komanso zowopsa zaka 380 miliyoni zapitazo.
Dunkleosteus kukula poyerekeza. © Image Mawu: Public Domain

Amadziwika chifukwa cha mphamvu zawo komanso amatha kusuntha nsagwada zawo mwachangu, zomwe zimawalola kusaka nyama mosavutikira. Zakale za Dunkleosteus zapezedwa ku North America, Morocco, Poland, ndi Belgium, pakati pa malo ena.

Dunkleosteus ikuwoneka ngati nyama yochititsa chidwi, komabe, pali zambiri zomwe zimadziwika za izo chifukwa cha kutha ndi zaka (zinalipo zaka 360-370 miliyoni zapitazo). Ngakhale palibe chomwe chimadziwika pamadera ambiri a thupi la Dunkleosteus, zambiri zasonkhanitsidwa kuchokera ku zotsalira za Dunkleosteus ndikumanganso.

Dunkleosteus idawululidwa kuti ili ndi mbali ziwiri za bony komanso kunja kwa zida. Ili ndi mapeyala awiri akuthwa a mafupa omwe amapanga mawonekedwe ngati milomo. Kukonzanso kwawonetsanso kuti mitundu ina ya Dunkleosteus inali ndi zipsepse zam'mimba, kutanthauza kuti mawonekedwe a ma placoderms amakhudzidwa kwambiri ndi zosowa za kuyenda.

Dunkleosteus terrelli imasiyanitsidwa ndi mawonekedwe ake ngati shaki komanso lobe yodziwika yakutsogolo pamchira wake. Dunkleosteus inali nsomba yamphamvu kwambiri yomwe inalipo mu nthawi ya Late Devonian. Akuti amafika kutalika kwa 346 mu (8.8 m) ndipo amalemera mpaka 8000 lb (3600 kg), zomwe zimapangitsa kukhala imodzi mwama placoderms akuluakulu omwe adakhalapo.

dunkleosteus
Dunkleosteus terrelli fossil. © Mawu Azithunzi: Wikimedia Commons

Dunkleosteus imadziwika chifukwa cha thupi lake lalikulu komanso lamphamvu, komanso mphamvu yake yoluma yomwe imatha kudulira shaki zakale mosavutikira. Dunkleosteus ndi imodzi mwa nsomba zazikulu kwambiri zomwe zimadziwika kuti zilipo. Atha kulemera mpaka 8000 lb (3600 kg), kuwapanga kukhala zolengedwa zazikulu.

Dunkleosteus sanali wosambira wabwino kwambiri, malinga ndi nthano. Chifukwa chakuti nthawi zambiri inkapezeka m’nyanja zosazama komanso m’nyanja zikuluzikulu, mafupa ake anali okwanira kuti azitha kudziteteza ku mitundu ina ya zamoyo, ndipo kuchuluka kwake sikunapangitse Dunkleosteus kuyenda mozama m’nyanja pofunafuna chakudya. Dunkleosteus anali wosambira waulesi chifukwa cha thupi lake lakuda ndi la mafupa komanso mawonekedwe a mafupa ngati zida.

Dunkleosteus inali ndi dongosolo lotchedwa four-bar linkage, lomwe linapangitsa kuti liwonjeze nsagwada zake mofulumira ndikupereka mphamvu yoluma yamphamvu pamene ikutseka pakamwa. Kupanikizika komwe kunapangidwa kunathandiza Dunkleosteus kudula mumtundu uliwonse, kumanga mano, kapena zida.

Chifukwa cha zimenezi, amalingaliridwa kuti, kuwonjezera pa ma ammonite ndi nsomba zina zotchedwa placoderm, shaki, ndi zamoyo zina zosambira mwaufulu, zimadziwikanso kuti zimadya nsomba zamtundu wawo zikakhala ndi njala. Izi zimalimbikitsidwa ndi kupezeka kwa mafupa a nsomba ndi zinthu zina zomwe zimagayidwa pang'onopang'ono kapena zosagayidwa muzinthu zakale.

Malo a Dunkleosteus sakudziwika bwino, ngakhale akuti Dunkleosteus wapezeka m'nyanja zosazama padziko lonse lapansi. Zimaganiziridwa kuti Dunkleosteus anali chimodzi mwa zolengedwa zoyamba kuberekana pogonana pogwiritsa ntchito njira yopangira dzira. Nthawi ya moyo wa Dunkleosteus sichidziwika, ngakhale idakhalapo nthawi ya Devonian zaka 360-370 miliyoni zapitazo.

Dunkleosteus amadziwika kuti ndi imodzi mwazodya zowopsa kwambiri zam'nyanja. Makhalidwe ambiri adalumikizidwa ndi chilombo chokhala ndi zida izi, ndikupangitsa kuti ikhale imodzi mwama placoderms owopsa kwambiri. Zomwe zimayambitsa kwambiri ndizo kudya nyama komanso kutha kupindika zitsulo.