Wc. Parker et Aj. Arnold, SPECIES SURVIVORSHIP IN THE CENOZOIC PLANKTONIC-FORAMINIFERA - A TESTOF EXPONENTIAL AND WEIBULL MODELS, Palaios, 12(1), 1997, pp. 3-11
The species survivorship curve for Cenozoic planktonic foraminifera wa
s fitted to exponential (age-independent) and Weibull (age-dependent)
models. Model fits that account for censorship bias have substantially
lower slopes (extinction probabilities) than suggested by censored da
ta. The best-fit Weibull model has a shape parameter significantly gre
ater than one (beta = 1.19), which normally indicates an age-dependent
increasing probability of extinction. Deviation of Weibull beta from
1.0 (exponential case) seems closely related to temporal variation in
records of very short-lived taxa (less than or equal to 1 my). The sha
pe of the curves are not sensitive to Corrected Species Survivorship a
djustment of longevities, but may reflect taxonomic procedure or tempo
ral variability in. extinction probability.