Dead Clade Walking

Dead clade walking also known as “survival without recovery” refers to a clade (group) of organisms which survived a mass extinction but never recovered in numbers, becoming extinct a few million years after the mass extinction or failed to recover in numbers and diversity.

The phrase “dead clade walking” was coined by David Jablonski as early as 2001 as a reference to Dead Man Walking, a film whose title is based on American prison slang for a condemned prisoner’s last walk to the execution chamber. Jablonski recognized at least four patterns in the fossil record following mass extinctions:

1) Unbroken Continuity (large-scale patterns continuing with little disruption);

2) Continuity with Setbacks (patterns disturbed by extinction event but soon continue on previous trajectory);

3) Survival without recovery or “Dead clade walking” (a group dwindles to extinction or minor ecological niches); and

4) Unbridled Diversification (increase in diversity and species richness, such as the mammals following the end-Cretaceous extinction event).

Jablonski found that the extinction rate of marine invertebrates was significantly higher in the stage (major subdivision of an epoch – typically 2–10 million years’ duration) following a mass extinction than in the stages preceding the mass extinction. His analysis focused on marine molluscs since they constitute the most abundant group of fossils and are therefore the least likely to produce sampling errors. Jablonski suggested that two possible explanations deserved further study:

  • Post-extinction physical environments differed from pre-extinction environments in ways which were disadvantageous to the “dead clades walking”.
  • Ecosystems that developed after recoveries from mass extinctions may have been less favorable for the “dead clades walking”.

“Dead clade walking” has since appeared in other scientists’ writings about the aftermaths of mass extinctions. Via Wiki

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