Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama

Abstract

BackgroundAs we know from modern species, nursery areas are essential shark habitats for vulnerable young. Nurseries are typically highly productive, shallow-water habitats that are characterized by the presence of juveniles and neonates. It has been suggested that in these areas, sharks can find ample food resources and protection from predators. Based on the fossil record, we know that the extinct Carcharocles megalodon was the biggest shark that ever lived. Previous proposed paleo-nursery areas for this species were based on the anecdotal presence of juvenile fossil teeth accompanied by fossil marine mammals. We now present the first definitive evidence of ancient nurseries for C. megalodon from the late Miocene of Panama, about 10 million years ago.Methodology/Principal FindingsWe collected and measured fossil shark teeth of C. megalodon, within the highly productive, shallow marine Gatun Formation from the Miocene of Panama. Surprisingly, and in contrast to other fossil accumulations, the majority of the teeth from Gatun are very small. Here we compare the tooth sizes from the Gatun with specimens from different, but analogous localities. In addition we calculate the total length of the individuals found in Gatun. These comparisons and estimates suggest that the small size of Gatun's C. megalodon is neither related to a small population of this species nor the tooth position within the jaw. Thus, the individuals from Gatun were mostly juveniles and neonates, with estimated body lengths between 2 and 10.5 meters.Conclusions/SignificanceWe propose that the Miocene Gatun Formation represents the first documented paleo-nursery area for C. megalodon from the Neotropics, and one of the few recorded in the fossil record for an extinct selachian. We therefore show that sharks have used nursery areas at least for 10 millions of years as an adaptive strategy during their life histories.

A New Early Miocene (Aquitanian) Elasmobranchii Assemblage from the la Guajira Peninsula, Colombia

“…The sole exception to this approach is the extinct genus Carcharocles Jordan and Hannibal, 1923, whose assignment in this study has prolonged the discussion presented by Pimiento et al (2010 In this work, the term "Tropical America" (Neotropics) refers to the geographical area of the western hemisphere located between the Tropic of Cancer (23° 27' N) and the Tropic of Capricorn (23° 27′ S). "Southern South America" is a region composed of the southernmost areas of South Figure 2.…”

“…chubutensis, C. megalodon and the other species of the lineage has been debated over the years and hitherto there is no consensus among paleoichthyologists concerning the different taxonomical approaches that are still in use (e.g., Cappetta, 2012;Pimiento et al, 2010Pimiento et al, , 2013bReinecke et al, 2011;Bor et al, 2012). According to Pimiento et al (2013a), the teeth of sub-adult and adult specimens of C. megalodon during the late Miocene.…”

“…According to Pimiento et al (2013a), the teeth of sub-adult and adult specimens of C. megalodon during the late Miocene. This phenomenon is a heterochronic process by which the ontogenetic changes mimic the changes in the Carcharocles clade throughout geologic time (Applegate and Espinosa-Arrubarrena, 1996;Ward and Bonavia, 2001;Pimiento et al, 2010Pimiento et al, , 2013aPimiento and Balk, 2015). According to Pimiento et al (2013a) Carcharocles chubutensis can be distinguished from C. megalodon based on the age of the fossils, e.g., an early Miocene specimen would be C. chubutensis while a late Miocene specimen would be C. megalodon.…”

“…Additionally, the extinct Carcharocles and the carcharhiniform Hemipristis serra are commonly found in coastal assemblages (e.g., Pimiento et al, 2010Pimiento et al, , 2013bCappetta, 2012) but must have also been present in open oceanic depositional environments (Carrillo-Briceño et al, 2015). Their fossil record and cosmopolitan distribution (Cappetta, 2012) suggest that these large species were able to move along significant distances over oceanic basins.…”

“…We compiled information on the paleodistribution of all chondrichthyan taxa known from the Neogene of the Americas (Appendix 1) [e.g., Tropical America (Leriche,1938;Casier, 1958Casier, , 1966Santos and Travassos, 1960;Gillette, 1984;De Muizon and Devries, 1985;Kindlimann, 1990;Kruckow and Thies, 1990;Iturralde-Vinent et al, 1996;Laurito, 1999;Donovan and Gunter, 2001;Reis, 2005;Portell et al, 2008;Aguilera and Lundberg, 2010;Pimiento et al, 2010Pimiento et al, , 2013aAguilera et al, 2011;Carrillo-Briceño et al, 2014, 2015, Southern South America (Long, 1993a;Arratia and Cione, 1996;Suárez and Marquardt, 2003;Suárez et al, 2006;Cione et al, 2011;Carrillo-Briceño et al, 2013) and North America (Case, 1980;Kruckow and Thies, 1990;Long, 1993b;Müller, 1999;Gonzales-Barba and Thies, 2000;Purdy et al, 2001;Boessenecker, 2011)]. For conducting the paleoenvironmental interpretation, we used Compagno (1984a,b), Compagno and Last (1999), Compagno et al (2005), Musick et al (2004), Kiraly et al (2003), Cao et al (2011), Voigt and…”