Effect of environmental variables on body size evolution
of crinoids between periods of mass extinction
Trisha Jani, Noel Heim, Jonathan Payne
I. Abstract

Earth’s history documents 5 major mass extinctions: Ordovician-Silurian, late Devonian,
Permian, Triassic-Jurassic, Cretaceous-Tertiary

There have been documented changes in CO2 concentration, O2 concentration, and sea
level

Environmental changes may affect body size: alter fitness and sustainability in local
area

Graphs provide visual correlation between these 3 variables and average crinoid area

CO2 concentration has greatest effect on size in periods between mass extinctions,

Figure 1 shows the relationship between CO2 and mean crinoid
area. There seems to be a negative correlation until the K-T
boundary and a positive correlation afterwards.
followed by sea level, and lastly O2
Phanerozoic Start to Ordovician-Silurian Extinction
Body size evolution trends follow unbiased random walk or stasis in between mass
Environmental Correlates
542-450 mya
extinctions

Correlation Values
CO2
Akaike.wt
Never follows driven trend
II. Background
GRW
0
URW
1
Stasis
0
O2
0
SL
0
CO2
0
r-value
(raw)
p-value
(raw)
r-value
(fd)
p-value
(fd)
0.955
0.045
0.999
0.027
Sea
Level
0.695 -0.202
 First appeared in the Ordovician; still present today, but in smaller numbers
Environmental Correlates
 2 forms: stalked (sea lilies) and unstalked (feather stars)
 Filter feed particles of food from sea water with feathery arms
GRW
0.003
 Pentaradial symmetry
URW
0.971
 Atmospheric CO2 concentration is a proxy for temperature
Stasis
0.017
O2
0.002
SL
0.003
CO2
0.003
 Sea level allows for an extension of environment: suggests territorial expansion
III. Materials & Methods
CO2
r-value
(raw)
p-value
(raw)
r-value
(fd)
p-value
(fd)
Environmental Correlates
0.078
URW
0.276
0.305 0.799
Stasis
0.291
0.502 0.174
O2
0.067
SL
0.193
CO2
0.095
0.665 0.889
O2
-0.222 0.258
0.720 0.675
Sea
Level
-0.710
0.186
0.727 -0.561 -0.565
0.273 0.439
0.435
Correlation Values
Akaike.wt
GRW
Correlation Values
Akaike.wt
Ordovician-Silurian to late Devonian Extinction
450-375 mya
O2
Permian to Triassic-Jurassic Extinction
251-199.6 mya
 Crinoids are an order of marine invertebrate from phylum Echinodermata
Figure 2 depicts that O2 and body size have a generally positive
correlation.
CO2
r-value
(raw)
p-value
(raw)
r-value
(fd)
p-value
(fd)
Environmental Correlates
Akaike.wt
GRW
0.082
0.330
GRW
0.018
URW
0.070
0.249
0.339 9.39e-5
Stasis
0.831
0.171 0.828
O2
0.018
SL
0.042
0.263
0.385
0.576 4.79e-4
URW
0.259
Stasis
0.406
O2
0.087
SL
0.085
CO2
0.080
Correlation Values
CO2
O2
0.562
0.006
 Measurements taken twice to ensure quality
0.1583 -0.039
0.493
Beaver, Harold. Echinodermata, Part T. N.p.: Geological Society of America, 1978. Print.
Alroy, John, ed. The Paleobiology Database. Web. 2 Aug. 2013. <http://paleodb.org>.
0.689
0.565 -0.173
-0.250
0.028 0.538
0.368
Cretaceous-Tertiary to Present
65.5-0 mya
Environmental Correlates
Akaike.wt
GRW
0.005
URW
0.020
Stasis
0.957
O2
0.006
SL
0.005
CO2
0.005
Correlation Values
CO2
O2
Sea
Level
r-value -0.715 -0.294 -0.694
(raw)
p-value 0.001 0.251 0.002
(raw)
r-value -0.324 0.245 -0.198
(fd)
p-value 0.220 0.360 0.463
(fd)
 Environmental factors play a very limited role in guiding body size evolution of
 CO2 has the highest correlations and lowest p-values in Phanerozoic Start to O.-S.
 For CO2, there was a negative correlation with body size until the K-T boundary and a
positive correlation afterwards.
 For sea level, correlation was positive from the start of the Phanerozoic to the Permian
extinction, negative until the Cretaceous-Tertiary boundary, then positive again
Triassic-Jurassic to Cretaceous-Tertiary times periods
References
0.004 0.408
 Visual analysis suggests a positive correlation with body size for O2
 Values are split between sea level and CO2 in both Permian to Triassic-Jurassic and
 Both raw data and first differences were considered
0.867
0.021
0.672 -0.222
Sea
Level
0.108
 When studied independently, environmental factors do not have definite effects
Devonian time period
 Environmental correlates determined with PaleoTS package on R
0.001
r-value
(raw)
p-value
(raw)
r-value
(fd)
p-value
(fd)
O2
crinoids in between periods of mass extinction
 Sea level has the highest correlation and lowest p-values in Ordovician-Silurian to late
 Graphs created with the statistical program R
CO2
CO2
V. Conclusion
Extinction , Late D. to P. Extinction, and K-T to Present
 Area measurements estimated with appropriate lengths
Sea
Level
0.645
Correlation Values
Akaike.wt
Sea
Level
0.276 0.856
r-value 0.042
(raw)
p-value 0.852
(raw)
r-value -0.175
(fd)
p-value 0.449
(fd)
Ordovician-Silurian extinction and Permian to Triassic-Jurassic extinction
 2 measurements taken: oral-aboral length and right-left diameter
Environmental Correlates
Triassic-Jurassic to Cretaceous-Tertiary Extinction
199.6-65.5 mya
 Evolution follows unbiased random walk in 2 time periods: starts of Phanerozoic to
 Measurements made with digital calibers
Late Devonian to Permian Extinction
375-251mya
O2
IV. Results
 Data was collected from The Treatise on Invertebrate Paleontology, Part T
Figure 3 suggests a positive correlation from the start of the
Phanerozoic to the Permian extinction, negative until the K-T
boundary, then positive until the present
 Environmental factors may have an effect of body size, but they may be the result of
several factors working interdependently
Acknowledgements
Thank you to the Stanford University School of Earth Sciences for providing the facilities that allowed me to conduct this research.
To Noel, thank you for always answering questions, making suggestions, and helping with R. To Jenny, thank you for organizing this
program and planning field trips that put showed me in real life what I learned in the classroom. To Jon, thank you for taking the
time to individually talk to us and provide feedback on our project. And lastly to the History of Life program, thank you for putting in
so much time to collect data!
Contact: Trisha Jani
[email protected]