Page 90 - Introduction to Paleobiology and The Fossil Record

TAPHONOMY AND THE QUALITY OF THE FOSSIL RECORD 77

Box 3.4 Lazarus taxa, Elvis taxa and dead clade walking

There is now a whole terminology for fossils that are absent, or seemingly in the wrong place at the
wrong time. David Jablonski of the University of Chicago began the story in 1983 when he invented
the term Lazarus taxa for species or genera that are present, then seemingly disappear, and then
reappear. The name is based on Lazarus in the Bible, who had died, but was brought back to life
by Jesus. Clearly species cannot reappear after they have become extinct, so Lazarus taxa identify
gaps in the record where fossil preservation is poorer than in the beds below and above.
Doug Erwin of the Smithsonian Institution and Mary Droser of the University of California at
Riverside then invented the term Elvis taxa in 1993 for species or genera that disappear, to be
replaced some time later by unrelated by strikingly similar impersonators (i.e. highly convergent
species). Elvis taxa can be mistaken for Lazarus taxa if the paleontologist does not study the anatomy
carefully.
Not to be outdone, David Jablonski then coined the term dead clade walking in 2002 to refer to
short-lived survivors of mass extinctions. He had found that many of the organisms that are found

after a mass extinction flourish for a while and then go – they had survived the extinction event,
but lacked the evolutionary staying power to be a serious part of the recovery.
As Claude Hopkins said in his book Scientifi c Advertising in 1923, “Often the right name is an
advertisement in itself”.

fossil finds that add to time ranges almost why: dinosaurs or frogs, mollusks or

always fill ghost ranges. In other words, new annelids, birds or bats, land snails or
finds, despite the hype in the press (“oldest clams?

human fossil rewrites the text books”), almost 3 When a tree dies, what might happen step
always fit into expected patterns in time and by step to its various parts – leaves, nuts,

space. branches, trunk and roots? How long
Perhaps the clade–stratigraphy compari- might each element survive, and where
sons (Box 3.3) are the closest to an assessment might they end up?
of the congruence between the fossil record 4 Why are Cambrian fossils likely to be less
and reality. To put it bluntly, if the fossils fi t abundant and less well preserved than
closely with a phylogenetic tree based on Miocene fossils?
analysis of the DNA of 100 modern species, 5 If you were determined to fi nd a new
then perhaps the fossil record (meaning 1) species of fossil, how would you plan your
correctly represents reality (meaning 3). expedition to ensure success?
This can never be an entirely decisive demon-
stration, but the more often congruence is
found between trees of living organisms and Further reading
their fossil record, the more confi dence Allison, P.A. & Briggs, D.E.G. 1991. Taphonomy:
perhaps paleontologists might have that the Releasing the Data Locked in the Fossil Record.
fossils tell the true story of the history of Plenum Press, New York.
life. Briggs, D.E.G. 2003. The role of decay and mineraliza-
tion in the preservation of soft-bodied fossils. Annual
Review of Earth and Planetary Sciences 31,
Review questions 275–301.
Briggs, D.E.G. & Crowther, P.R. 2001. Palaeobiology;
1 Summarize the key hard and soft tissues A Synthesis, 2nd edn. Blackwell Publishing,
in the human body. Which would decay Oxford.
first (the most labile tissues) and which Donovan, S.K. 1991. The Processes of Fossilization.

last (the most refractory tissues)? Belhaven Press, London.
2 Which of these groups of fossils are Hammer, O. & Harper, D.A.T. 2005. Paleontological
likely to be more completely known, and Data Analysis. Blackwell Publishing, Oxford.