Grŵp o folysgiaid morol diflanedig yw amonitau, a ddiflannodd yn ystod Difodiant y Cyfnod Trydyddol Cretasig 65 miliwn o flynyddoedd yn ôl. Yr octopws, y fôr lawes a’r fôr-gyllell yw perthnasau agosaf amonitau sy’n dal yn fyw heddiw.Roedd amonitau’n dodwy eu hwyau mewn swp unigol ar ddiwedd eu hoes. Byddai’r rhain, ynghyd ag amonitau ifanc, yn arnofio ar wyneb y cefnfor pan gawsant eu lladd gan effeithiau’r ardrawiad meteorit.
Ammonites are an extinct group of marine molluscs, which died out during the Cretaceous-Tertiary Mass Extinction, 65 million years ago. Ammonites’ closest living relatives are octopus, squid and cuttlefish. Ammonites laid their eggs in a single batch at the end of their life. These, along with juvenile ammonites, would have been floating at the surface of the ocean when they were killed off by the effects of the meteorite impact. It is thought that their modern relatives survived the extinction because they lay eggs on the sea floor and in smaller batches many times during their life
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