Giant 'Teenager' Shark from the Dinosaur Era Identified from Vertebrae Remains 23 April 2020
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Giant 'teenager' shark from the dinosaur era identified from vertebrae remains 23 April 2020 Ptychodontid sharks are mainly known from their flattened teeth, which allowed them to crush hard- shelled prey like bivalves or ammonites, similar to some of today's ray species. However, the find in Spain consists only of parts of the vertebral column and placoid scales (teeth-like scales), which are much rarer than teeth in the fossil record. In contrast to teeth, shark vertebrae bear important information about a species' life history such as size, growth and age, which are saved as growth rings inside the vertebra, like in the stem of trees. Statistical methods and the comparison with extant species allowed the scientists to decode these data Hypothetical outlines of †Ptychodus showing the minimum and maximum size estimations for the sub- and reconstruct the ecology of this enigmatic shark adult specimen from Spain. Credit: Patrick L. Jambura group. Ptychodontid sharks grew big and old Scientists of the University of Vienna have "Based on the model, we calculated a size of 4-7 examined parts of a vertebral column found in meters and an age of 30 years for the examined northern Spain in 1996, and assigned it to the shark. It's astonishing that this shark was not yet extinct shark group Ptychodontidae. In contrast to mature when it died despite its rather old age," says teeth, shark vertebrae bear biological information Patrick L. Jambura, lead author of the study. like body size, growth and age, which allowed the Sharks follow an asymptotic growth curve, meaning team of Patrick L. Jambura to gain new insights that they grow constantly until maturation, and after into the biology of this mysterious shark group. that, the growth curve flattens, resulting from a reduced growth rate. "However, this shark doesn't In 1996, palaeontologists found skeletal remains of show any signs of flattenings or inflections in the a giant shark on the northern coast of Spain, near growth profile, meaning that it was not mature—a the city Santander. Here, the coast comprises teenager, if you want. This suggests that these meter-high limestone walls that were deposited sharks even grew much larger and older." during the Cretaceous period around 85 million years ago, when dinosaurs still roamed the world. The study suggests that ptychodontid sharks grew Scientists from the University of Vienna examined very slow, matured late, but also showed high this material now and were able to assign the longevity and reached enormous body sizes. "This remains to the extinct shark family Ptychodontidae, might have been a main contributor to their a group that was specious and successful in the success, but also, eventually, demise." Cretaceous but vanished mysteriously before the infamous end-Cretaceous extinction event. Do modern sharks face a similar fate? Shark vertebrae are rare but precious in the Many living sharks, like the whale shark or the fossil record great white shark, show very similar life history traits, a combination of low recruitment and late 1 / 2 maturation, which makes them vulnerable to anthropogenic threats, like overfishing and pollution. "It might be the case that similar to today's sharks, ptychodontid sharks faced changes in their environment to which they could not adapt quickly enough, and ultimately led to their demise, even before dinosaurs went extinct. However, unlike in the Cretaceous period, it is up to us now to prevent this from happening to modern sharks again and to save the last survivors of this ancient and charismatic group of fishes." More information: Patrick L. Jambura et al. Articulated remains of the extinct shark Ptychodus (Elasmobranchii, Ptychodontidae) from the Upper Cretaceous of Spain provide insights into gigantism, growth rate and life history of ptychodontid sharks, PLOS ONE (2020). DOI: 10.1371/journal.pone.0231544 Provided by University of Vienna APA citation: Giant 'teenager' shark from the dinosaur era identified from vertebrae remains (2020, April 23) retrieved 26 September 2021 from https://phys.org/news/2020-04-giant-teenager-shark-dinosaur- era.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. 2 / 2 Powered by TCPDF (www.tcpdf.org).