Question

Read the news article below and answer questions Oldest fur seal identified, ending 5-million-year ghost lineage Date: February1, 2015 Eotaria crypta The oldest known fur seal has been discovered by a Geology PhD student at New Zealand's University of Otago, providing a missing link that helps to resolve a more than 5-million-year gap in fur seal and sea lion evolutionary history Otago's Robert Boessenecker and colleague Morgan Churchill from the University of Wyoming have named this new genus and species of fur seal Eotaria crypta. The genus name Eotan The discovery of the seal is newly published in UK Royal Society journal Biology Letters. The species was tiny, with adults being only slightly larger than a sea otter and around the size of a juvenile New Zealand fur seal, says Mr Boessenecker Its fossilized partial jaw, with several well-preserved teeth, was recovered from a 15-17 million-year-old rock formation in Southern California in the early 1980s, but until now had been misidentified as belonging to a walrus species. The fossil was deposited in what is now the John D. Cooper Archaeological and Paleontological Center, where Mr Boessenecker found it while searching through its collections. He says he instantly realized that it was not the small walrus Neotherium but a tiny early fur seal. This was very exciting as fur seals and sea lions--the family Otariidae-have a limited fossil record that, up until now, extended back to about 10-12 million years ago. Yet we know that their fossil record must go back to around 16-17 million years ago or so, because walruses--the closest modern relative of the otariids--have a record reaching back that far," he says. In palaeontology, a gap like this is known as a ghost lineage, and the new research has now eliminated it. "Until now we had no fossil evidence for the first five million years of fur seal and sea lion evolution. It's extremely satisfying to have remedied that," he says. a means 'dawn sea lion 5I Page

Answer 1

Missing link- which help to predict evolutionary history Missing link, hypothetical extinct creature halfway in the evolutionary line between modern human beings and their anthropoid progenitors. In the latter half of the 19th century, a common misinterpretation of Charles Darwin’s work was that humans were lineally descended from existing species of apes. To accept this theory and reconcile it with the hierarchical Great Chain of Being, some fossil ape-man or man-ape seemed necessary in order to complete the chain. Today it is recognized that the relationship of modern humans to the present anthropoid apes (e.g., chimpanzees) is through common ancestors rather than through direct descent. These ancestors have yet to be identified, but ape-hominid divergence may have occurred 6 to 10 million years ago. Equivalent case like human explained in article.

Transitional fissil- it is unlikely that any particular form represented in the fossil record is a direct ancestor of any other.

e.g. Apes and human - Ardipithecus ramidus and Australopithecus

fish and tetrapods

seal and walrus

Ghost lineages-

A ghost lineage is a phylogenetic lineage that is inferred to exist (inferred-existence) but has no fossilrecord. The process of determining a ghost lineage relies on fossilized evidence before and after the hypothetical existence of the lineage and extrapolating relationships between organisms based on phylogenetic analysis.

Ghost lineages are commonly confused with Lazarus taxa, but there is a difference. For example, coelacanths are a Lazarus taxon, and the gaps in its fossil record are referred to as ghost lineages.

e.g. - Chronopiratus , Protanguilla

5 - evidences

The poorly known fossil record of fur seals and sea lions (Otariidae) does not reflect their current diversity and widespread abundance. This limited fossil record contrasts with the more complete fossil records of other pinnipeds such as walruses (Odobenidae). The oldest known otariids appear 5–6 Ma after the earliest odobenids, and the remarkably derived craniodental morphology of otariids offers few clues to their early evolutionary history and phylogenetic affinities among pinnipeds. We report a new otariid, Eotaria crypta, from the lower middle Miocene ‘Topanga’ Formation (15–17.1 Ma) of southern California, represented by a partial mandible with well-preserved dentition. Eotaria crypta is geochronologically intermediate between ‘enaliarctine’ stem pinnipedimorphs (16.6–27 Ma) and previously described otariid fossils (7.3–12.5 Ma), as well as morphologically intermediate by retaining an M2 and a reduced M1 metaconid cusp and lacking P2–4metaconid cusps. Eotaria crypta eliminates the otariid ghost lineage and confirms that otariids evolved from an ‘enaliarctine’-like ancestor,.