Paper No. 20-9
Presentation Time: 1:30 PM-5:30 PM
PREDATION OR SCAVENGING? TOOTH-MARKED DELPHINID VERTEBRAE FROM THE MIOCENE OF THE CALVERT CLIFFS AND LEE CREEK MINE HINT AT POSSIBLE FEEDING HABITS OF CARCHAROCLES MEGALODON
Three caudal vertebrae with bite marks were collected from Miocene deposits located in the Calvert Cliffs of Maryland and the Lee Creek Mine of North Carolina and examined to draw conclusions on the possible feeding habits and preferred prey type of the extinct shark Carcharocles megalodon. Two of the vertebrae were collected from the Plum Point Formation in the Calvert Cliffs and the third vertebrae from the Pungo River Formation from the Lee Creek Mine area. Vertebrae bite marks are attributed to the predator C. megalodon, based on bite mark size, characteristic serrations, and known Miocene marine predators in these localities. The vertebrae belong to three small to medium sized Delphinid individuals from one or more possible species within the Eurhinodelphinidae, Platanistidae, or Squalodelphinidae families; based partially on comparison with specimens from the Smithsonian’s collections of extinct and extant marine mammals. Due to the unreliability of disarticulated vertebra as an identifier family was the lowest taxonomic level interpreted. The most common bite mark found was Type 1, comprising about 80% of the 43 total marks, with the remaining 20% consisting of Types 2 and 5. The vertebra from Lee Creek and one of Calvert vertebrae were found to have between 4-11 marks on the left and right lateral surfaces, while the second Calvert specimen had 11 marks on the right lateral surface only. The geometry of the marks relative to the base of the vertebrae suggests that two of these individuals were attacked from behind and slightly below, an attack pattern commonly seen in modern sharks like the great white (Carcharodon carcharias), while the third was attacked from the right. Previous studies have suggested that this pattern of attack was a behavioral adaptation brought about by the evolution of echolocation in smaller cetacean species, in which the shark makes use of blind spots in the prey’s sonar range. The evidence provided by these specimens appear to support the hypothesis of active predation rather than scavenging. Given that these three similarly scarred vertebrae were found in three separate locations, this may be evidence of a pattern showing that C. megalodon actively preyed upon small to medium sized cetaceans by striking from below or behind.