seppenradensis differentiated from its ancestor, developing into an animal that could grow much larger in size. leptophylla, after the latter had spread from a small and limited habitat off the coastlines of western Europe down to the western Gulf of Mexico. seppenradensis.īased on their study of these animals, the team concluded that P. In size, the 154 specimens ranged from 0.1 meters to 1.8 meters, allowing the most complete study yet of the full development cycle of P. seppenradensis, including historical fossils, and an abundance of new fossils from Mexico and England. In their new paper, Ifrim and her colleagues studied all available specimens of Parapuzosia leptophylla and P. It's been difficult to perform comparisons with other ammonites of the Parapuzosia genus, because the fossil record is sparse. And it can be tricky to work out which of these may have played a role in a species' evolution if information is scarce.įor the giant ammonite Parapuzosia seppenradensis, information has been pretty scarce. But there are others disease, for instance climate and food availability can also play significant roles. Predation is a major driver of evolutionary pressure. Microbes that have developed antibiotic resistance are one example of evolutionary pressure. Those individuals with traits best suited to surviving that stress are more likely to reproduce and pass those traits on to offspring. It occurs when stress is placed on a population in a way that could affect reproductive success. Now, after studying the fossilized remains of 154 ammonites across a range of sizes, an international team led by paleontologist Christina Ifrim of Heidelberg University in Germany think they might have a possible answer: to avoid being eaten by fearsome aquatic mosasaurs.Įvolutionary pressure is a fascinating phenomenon. No other ammonite ever reached such a prodigious size – and, as with all outliers, scientists have been keen to understand exactly why.
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