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Fosil Katak Tertua Di Amerika Utara

Riset asisten profesor geosains Michelle Stocker dari Virginia Tech College of Science di ‎Blacksburg, Virginia, Amerika Serikat (AS) dan  asisten profesor geosains Sterling Nesbitt dari Department of Geosciences di Virginia Tech, Amerika Serikat (AS), mengidentifikasi satu fragmen fosil yang diduga merupakan katak tertua di Amerika Utara. Fragmen fosil itu ditemukan oleh Stocker dan koleganya 18 Mei tahun 2018 di zona Formasi Chinle Arizona (Virginia Tech, 27/2/2019).

Fragmen fosil katak itu terdiri dari beberapa potongan kecil tulang pinggul (ilium) katak Chinle—nama katak sesuai lokasi penemuannya—bukan leluhur langsung dari katak abad ini. Fragmen fosil ukuran lebih kecil dari kuku kelingking itu, terbalut dalam batu-karang. Jenis ini mewakili sisa-sisa kelompok katak paling awal khatulistiwa dari Late Triassic sekitar 216 juta tahun silam (Science Daily, 27/2/2019).

“This new find highlights just how much there is still to learn about the Late Triassic ecosystem, and how much we find when we just look a little closer. We're familiar with the charismatic archosaurs from the Chinle Formation, but we know that based on other ecosystems, they should make up a small percentage of the animals that lived together. With this new focus we're able to fill in a lot of those missing smaller components with new discoveries. The Chinle frog could fit on the end of your finger. These are the oldest frogs from near the equator. The oldest frogs overall are roughly 250 million years old from Madagascar and Poland, but those specimens are from higher latitudes and not equatorial,” papar Michelle Stocker (Virginia Tech, 27/2/2019).

Riset itu melibatkan juga peneliti asal Petrified Forest National Park di Arizona (Amerika Serikat) dan Museum of Natural History pada University of Florida. Ekspedisi ilmiah musim semi 2018 itu juga melibatkan Elizabeth Evans, mahasiswi pada School of Performing Arts; Rebecca Hawkins, mahasiswi pada Department of Fish and Wildlife Conservation dan Hector Lopez, mahasiswa sains biologi. Kajian lebih lanjut fosil itu menggunakan CT scan. Hasil riset itu dirilis oleh jurnal Biology Letters edisi elektronik 27/2/2019.

Usia fosil katak itu berkisar 215 juta tahun. “Now we know that tiny frogs were present approximately 215 million years ago from North America, we may be able to find other members of the modern vertebrate communities in the Triassic Period,” asisten profesor geosains Sterling Nesbitt (Virginia Tech, 27/2/2019).

Riset itu didanai oleh National Science Foundation, the National Geographic Society, David B. Jones Foundation, Petrified Forest Museum Association, dan Friends of Petrified Forest National Park di Amerika Serikat (AS). “Our development of methods that recover delicate bones from small-bodied vertebrates enabled this exciting discovery. Our aim is to use similar techniques in the Chinle Formation to uncover the early history of other small-bodied animals including lizards, salamanders, turtles, and mammals,” papar Ben Kligman, mahasiswa doktoral (Ph.D) Geosciences asal Philadelphia, Pennsylvania (AS) (Virginia Tech, 27/2/2019). 

Oleh: Servas Pandur