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Dong vat luong cu co dai co ham rang lon

Vao thoi tien su co mot loai an thit trong giong loai ca sau cu tru o vung Nam Cuc vao khoang 240 trieu nam truoc, no co nhung chiec rang nanh lon khong chi moc theo ria mieng ma con ca o tren vom mieng nua.

Dong vat luong cu co dai co ham rang lon

Loai Kryostega collinsoni song o vung nuoc ngot moi duoc dat ten thuoc nhom temnospondyl (nhom dau giap) – nhom dong vat luong cu tung phat trien da dang vao ky Triat khi ma khung long moi xuat hien. Nhom temnospondyl la ho hang da tuyet chung cua loai ky giong va ech ngay nay.

No co chieu dai dat toi 15 fit voi hop so dai va rong tham chi con det hon ca hop so cua ca sau. Nhung chiec rang ham cua no cao hon 1inch (tren 2,5 cm). Chiec rang nanh dai nhat moc tren vom mieng cua no tham chi con dang so hon khi dat chieu dai 1,5 inch (gan 4cm).

Christian Sidor – pho giao su nganh sinh hoc thuoc dai hoc  Washington  kiem phu trach nganh co sinh vat hoc/dong vat co xuong song thuoc Bao tang lich su  tu nhien  va Van hoa Burke – cho biet: “Nhung chiec rang cua no, so voi cac loai luong cu khac, qua thuc la khung khiep. No khien chung ta tin rang Kryostega collinsoni la ke san moi ha guc ca nhung con moi lon”. 

Ham rang sac nhon cua hoa thach temnospondyl, va con xuat hien o khoang 1/3 vom mieng. (Anh: Christian Sidor)

Ong them rang: “Chung toi cho rang Kryostega la loai vat song duoi nuoc, co le no an chu yeu la ca va cac loai luong cu khac song cung no trong dong song. Tuy nhien, giong nhu ca sau hien dai, neu cac loai vat song tren can lang vang qua gan bo song, thi con Kryostega se loi chung xuong”. Sidor chi dao tien hanh mot nghien cuu  ve loai vat moi nay va cong bo nghien cuu  tren so ra thang 9  to Journal  of Vertebrate Paleontology. Cac cong su cua ong bao gom Ross Damiani thuoc Bao tang tu nhien  Stuttgart (Duc) va William  Hammer thuoc Truong Augustana (Dao Rock, Ill). Nghien cuu  duoc Quy khoa hoc  quoc gia va Quy Alexander  von Humboldt tai tro mot phan.

Kich co dang ngac nhien 

Ket qua nghien cuu  da lam sang to them ve cac loai dong vat song o lanh tho ma ngay nay tro thanh Nam Cuc. Sidor noi: “No nhac chung toi nho rang the gioi  co dai khong he giong nhu the gioi  ngay nay, luc thi thoi tiet am ap hon con co thoi gian  thi lai lanh leo hon”.

Nam Cuc vao giua ky Triat am ap hon so voi ngay nay, nhung lai khong phai la nhiet doi  hay co khi hau on hoa. Cac mo phong thoi tiet tren may tinh  cho thay thoi tiet vao thoi diem do khac nghiet theo mua, voi nhung khoang thoi gian  hoan toan chim trong bong toi.

Cac nha khoa hoc  trong nhom nghien cuu  phan mieng hoa thach cua con K. collinsoni da phan tich  cau truc o hop so hoan thien cua cac loai vat thuoc nhom temnospondyl khac co cung dac diem ve kich co.

Sidor noi: “Cau truc giai phau cua phan mieng cho chung ta biet hoa thach nay thuoc ve nhom luong cu lon nao”. 

Vung mau sam o phan mieng chinh la kich co hoa thach K. collinsoni phat hien duoc vao nam 1986, so sanh voi toan bo kich co uoc luong cua phan dau. (Anh: Christian Sidor)

Nhung chiec rang o ben ria mieng cung nhu ranh tren vom co the quan sat duoc de dang. Su hien dien cua cac cau truc cua con vat co dai tuong duong voi nhung cau truc cho phep ca va luong cu ngay nay cam nhan duoc cac bien doi trong ap luc nuoc da dua cac nha nghien cuu  di den ket luan rang con vat song duoi nuoc.

Phan mieng hoa thach cung co lo mui, dieu nay da ho tro cho cac nha nghien cuu  trong viec xem xet ty le cua phan dau khi so sanh no voi cac hoa thach khac. Ho uoc tinh hop so co chieu dai la 2,75 fut con chieu ngang toi da la 2 fut.

“Kryostega la loai vat lon nhat o Nam Cuc vao ky Triat”.

Tu “kryostega” dich ra nghia la “dong bang” va “vom”, cai ten nay am chi den phan dinh hop so. Cac nha khoa hoc  dat ten cho loai Kryostega collinson theo James Collinson – giao su danh du nganh khoa hoc  Trai Dat thuoc dai hoc  bang Ohio, nguoi da co dong gop lon trong nghien cuu  dia chat Nam Cuc.

Hammer da thu thap hoa thach vao nam 1986 tu lop dia chat Nam Cuc co ten la Fremouw Formation. Ong nghien cuu  rat nhieu cac hoa thach Nam Cuc khac, trong do co ca khung long, duoc thu thap vao cung mot thoi diem. Hoa thach temnospondyl chi moi duoc nghien cuu  ky cang may nam gan day.

Khac biet trong qua khu

Vao thoi diem ma K. collinsoni sinh song, tat ca dat lien tren the gioi  gan ket voi nhau thanh mot luc dia khong lo  co ten Pangea. Vung dat thuoc Nam Cuc noi tim thay hoa thach o gan vung dat ma ngay nay tro thanh long chao Karoo thuoc nam Phi  – mot trong nhung khu vuc  nhieu hoa thach nhat tren trai dat. 

Ban do the hien vung dat noi phat hien hoa thach Kryostega collinsoni tai Nam Cuc. (Anh: Christian Sidor)

Sidor nhan manh rang giai doan dau ki Triat, tu cach day 245 trieu nam cho den 251 trieu nam, truoc giai doan co hoa thach K. collinsoni, Nam Cuc va nam Phi  la dia diem  cu tru cua he dong thuc vat gan nhu giong nhau. Trong khi Nam Cuc van lanh hon rat nhieu vung tren the gioi, no van am hon dang ke so voi ngay nay va van phai trai qua nhung giai doan tam toi hoan toan.

Vao giua ky Triat, co le he dong thuc vat o Nam Cuc va nam Phi  chi con giong nhau co mot nua. Vao dau ky Jura, cach day khoang 190 trieu nam, nhung con khung long dau tien xuat hien o Nam Cuc.

Sidor noi: “Co the cac loai dong vat da thich nghi duoc voi moi truong  song cua chung. Chung ta hien nay dang nhin thay ket qua cua qua trinh hinh thanh loai o vi do cao. Tai day chung toi  da co duoc bang chung thuyet phuc chung minh rang Nam Cuc khong giong ngay nay hoan toan. Trong suot ki Triat, thoi tiet am hon nhieu so voi ngay nay. Va toan cau  cung am len chu khong phai rieng Nam Cuc”.

Tim bai viet khac
Theo Tra Mi (khoahoc.com.vn)
Updated: 15/09/2008 | Views: 529 | Comments: 0

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