Paleontologists from Brazil and the United States announced the discovery of tapeworm eggs found in 270 million year old fossil shark feces (more formally known as coprolites) in the Jan. 30, 2013, issue of the open access peer reviewed journal Public Library of Science.
In total, 93 small oval-elliptical smooth-shelled structures were found in thin section of a shark coprolite. The structures were determined to be unbroken tapeworm eggs.
The eggs are approximately 145 to 155 mm in length and 88 to 100 mm in width and vary little in size within the cluster The deposition in shark feces is consistent with how modern tapeworm eggs are deposited in shark feces. The tapeworms are most probably an early relative of the order of cestodes (tapeworms) found in Elasmobranchs (cartilaginous fish like sharks).
This discovery indicates that tapeworms have been around eons longer than previously known. This is only the third instance in all paleontological history that an intestinal parasite has been recovered and identified.
The development of infectious parasitic diseases is indicated to have arisen much earlier than ever known before by this find and the development of specific evolutionary changes in DNA and body structures in sharks and other animals to cope with a new threat is inferred from this discovery.
Citation: Dentzien-Dias PC, Poinar G Jr, de Figueiredo AEQ, Pacheco ACL, Horn BLD, et al. (2013) Tapeworm Eggs in a 270 Million-Year-Old Shark Coprolite. PLoS ONE 8(1): e55007. doi:10.1371/journal.pone.0055007