GEL 12 Lecture Notes - Lecture 16: Brownian Motion, Species Complex, Linear Function
1. How many kinds of dinosaurs were there, and did dinosaurian diversity constantly
increase?
a. Based on equations for estimating diversity including cryptic species
i. 1844 estimated genera, including undiscovered ones
ii. At around year 2000, about 600 genera were known
1. 600 on record right now
iii. Increased drastically within the next few years
iv. We will never reach 100% known genera but we will approach it
v. By 2100, it is estimated we will discover 90% of known genera
b. Constant increase in diversity?
c. It appears as if the dinosaurian diversity increased with time when looking
at the raw data
d. Number of rock formations yielding dinosaurs may be correlated with
number of dinosaur genera discovered
e. However, the observation may be an artifact of fossil preservation and there
may not have been a constant increase in diversity
2. How do we estimate the body mass of dinosaurs?
a. Physical Model
i. Measured the volume in water
ii. Estimated the whole-body density of an alligator
1. Approximately 0.9g/cm^3
iii. Multiplied the volume by the density, and scaled it up to the actual
size
b. Regression
i. Linear growth correlation between circumference of thigh bone (
femur and humerus) and the body mass
1. Use the log of the measurements
c. 3d computer model
i. Fit a convex hull onto 3D scans of dinosaur skeletons
ii. Variations in body mass estimates may result from methodological
differences
iii. Early estimates of very heavy dinosaurs are unlikely to be true
3. What is Cope’s rule?
a. A hypothesis, not an absolute rule
b. Body size in a lineage tends to increase over evolutionary time
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