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Dinosaur Diversity (Greater analysis possible 2000s (New statistical…
Dinosaur Diversity
Greater analysis possible 2000s
New dating techniques - radiometric dates dinos/crater/volcanism
New temp/sealevel proxies
New statistical methods
for studying dino diversity
Allow test diversity/evo change through time
Anatomical Msmt Diversity
Decreased anatomical diversity in plant-eaters
not meat-eaters / larger dinosaurs
Shows anatomical diversity (infer diet, behaviour etc)
some dinosaur groups declining slightly (plant eaters esp)
Agrees with diversity trends from 'number of species' studies
Trends in dinosaur diversity
(number of species)
Brusatte
et al 2015
Paleobiology database with all findings and new stat methods
No long term decline
globally or locally
Rules out sealevel / temp influencing dinosaurs
If anything
higher diversity
before mass extinction
Latest Cretaceous =Best Sampled
More sampling late Cretaceous than early
Complicates signal ?
Still no evidence long term decline
when sampling corrected for
Final few Myr Cretaceous Decline
Slight decline plant-eating dinosaurs
not meat-eaters
Not all dinosaur types
Classic
approach found
dinosaur diversity increasing up to 10Ma before impact
slow decline possibly toward boundary
doesn't account for sampling biases
Russell 1984 Subsampling
No decline late Cretaceous
if subsampling used
Fastovsky
2004 Subsampling
Confirmed no change dinosaur diversity during Late Cretaceous
Classic approach
count up dino fossil occurrence in time bins
dinosaurs seem to increase with time
up until 10 Ma before impact
simplistic
doesn't account for sampling biases
rock exposure etc
no analyses
making lists
Dinosaur
Extinction
~66 Ma
Dinosaur Extinction at time of asteroid
Other influences before impact?
climate shift / regression / Deccan Traps
Asteroid?
Dinosaur workers were biggest opponents to impact theory
Infer from diversity trends whether dinosaurs
Gradually decline before impact - other influences
Thriving up until boundary - probably asteroid
Diversity Msmts
Number of species corrected for sampling
Morphological disparity
Anatomical diversity
Statistical Analyses Progress
Subsampling (Russell 1984)
Predicts fossil occurrence if there were no sampling biases
Simulates even fossil sampling
Subsampling Analyses (Fastovsky 2004)
Confirmed no change dino diversity during Late Cretaceous
Subsampling with updated statistical techniques
How were dinosaurs changing through late Cretaceous?