the quality of the fossil record -...
TRANSCRIPT
Paleobiology!March 07, 2016
The Quality of the Fossil Record
A brief detour
Why does this gradient exist?
The core question in paleobiology n What is the history of biodiversity throughout the Phanerozoic?
The core question in paleobiology n What is the history of biodiversity throughout the Phanerozoic?
Population growth
Geometric growth
Logistic growth n Virtually all fossil data-sets
show a dramatic post-Paleozoic rise in biodiversity.
n Time-series of fossil biodiversity are strikingly similar to time-series of sedimentary rock volume.
n As the quantity of rock increases the quality of sampling likely increases leading to higher biodiversity.
Species area effect
Region 2 Region 1
Total Richness = 6 Total Richness = 4
Species area effect
Time 2 Time 1
Total Richness = 6 Total Richness = 4
The consensus that was not n David Raup and Jack Sepkoski (the
Chicago School) believed that there was no rise in biodiversity.
n James Valentine and Dick Bambach believed that there was a 10-fold rise.
n They put out a consensus paper in the mid-80s where they compromised and said that there was a 3-fold rise.
n Neither side really believed in the consensus and their intellectual descendants debate the issue to this day!
The consensus that was not n David Raup and Jack Sepkoski (the
Chicago School) believed that there was no rise in biodiversity.
n James Valentine and Dick Bambach believed that there was a 10-fold rise.
n They put out a consensus paper in the mid-80s where they compromised and said that there was a 3-fold rise.
n Neither side really believed in the consensus and their intellectual descendants debate the issue to this day!
The Paleobiology Database n Clear extinctions and
radiations
n A stable Paleozoic plateau and a rise starting in the Cenozoic
The Macrostrat Database n A map of stratigraphic units in
time and space.
n Allows us to distinguish between gaps in the fossil record that arise because of un-sampled marine sediments versus missing (eroded) marine sediments. Ti
me!
Sample standardization Region 2 Region 1
Total Richness = 4 Total Richness = 4
Sample standardization (resampling) Region 2 Region 1
Total Richness = 5 Total Richness = 4
Sample standardization (resampling) Region 2
Total Richness = 4
Total Richness = 5
Total Richness = 5
Total Richness = 4
Average Richness = 4.66
Region 1
The Paleobiology Database n Standardize diversity with
resampling methods.
n Essentially, we hold the amount of sedimentary rock roughly constant through time.
n We still see a dramatic post-Paleozoic rise in biodiveristy, but not as dramatic as Valentine predicted.
The Paleobiology Database n Randomly reassign PBDB
collections to Macrostrat Units
n Randomizes the spatiotemporal distribution of collections
n Diversity will thus be an expression of the preserved # of units over time
Null model based on Macrostrat n The randomized curve
is a biologically meaningless curve
n Many major extinctions and radiations are still visible
n The Cenozoic rise disappears
Null model based on Macrostrat
Quality not quantity n Because predictions of biodiversity based exclusively on
changes in the rock record do not predict a post-Paleozoic rise in the first place, Raup’s fears seem unfounded.!
n But never forget that just because the Valentinian rise cannot be attributed to changes in the quantity of rock, doesn’t mean that it is real!!
Lithification and Unlithification
Bed thickness
Lazarus, Elvis, and Zombie Taxon
Unit A
Unit C
Pull of the recent
Unit A
Unit C
Unit E
Unit B
Unit D