At present, the latest archaeological research shows that about 80 million years ago, ancient ammonites the size of human bodies swam in the Atlantic Ocean. They had long arms and a spiral shell diameter of 1.8 meters. This species is the largest ammonites in the world so far. They are extinct marine invertebrates. Chrysanthemum stone exists from the Middle Ordovician to the Late Cretaceous, so it is named because its surface has similar chrysanthemum lines.
This latest research report was published in the journal PLoS ONE on November 10. Researchers examined 154 ammonite fossils, thus filling the evolutionary history of this ancient giant cephalopod, including some historical specimens, and more than 100 newly discovered fossils from Britain and Mexico.
Based on this analysis, they found that a kind of ammonite called Parapuzosia seppenradensis appeared in the Atlantic Ocean about 80 million years ago. It may be closely related to another relatively small species, Parapuzosia leptophylla, whose spiral shell diameter is up to 1 meter.
Why are they so huge? Experts pointed out that in ancient times, ammonites may face the pressure of growth and evolution, because there was a larger predator in the ocean during the Cretaceous period - Canglong, which was the ultimate hunter of the ancient ocean, with a body length of up to 17 meters and a weight of up to 20 tons.
Archaeological evidence shows that Canglong preys on ammonites, but at present, there is no evidence that Canglong preys on Parapuzosia seppenradensis. Although this new study fills in some gaps in the past of giant cephalopods, many mysteries remain unsolved.
