Proposed biotic causes

A. Medical problems

(a) Slipped disks in the vertebral column causing dinosaur debilitation

(b) Hormone problems

(1) Overactive pituitary glands leading to bizarre and non-adaptive growths

(2) Hormonal problems leading to eggshells that were too thin, causing them to collapse in on themselves in a gooey mess

(c) Decrease in sexual activity

(d) Blindness due to cataracts

(e) A variety of diseases, including arthritis, infections, and bone fractures

(f) Biting insects carrying diseases that did dinosaurs in over hundreds of thousands to millions of years

(g) Epidemics leaving no trace but wholesale destruction

(h) Parasites leaving no trace but wholesale destruction

(i) Change in ratio of DNA to cell nucleus causing scrambled genetics (j) General stupidity

B. Racial senescence

This is the idea, no longer given much credence, that entire lineages grow old and become "senile," much as individuals do. Thus, in this way of thinking, late-appearing species would not be as robust and viable as species that appeared during the early and middle stages of a lineage. The idea behind this was that the dinosaurs as a lineage simply got old and the last-living members of the group were not competitive for this reason

C. Biotic interactions

(a) Competition with other animals, especially mammals, which may have outcompeted dinosaurs for niches, or perhaps ate their eggs

(b) Overpredation by carnosaurs (who presumably ate themselves out of existence)

(c) Floral changes

(1) Loss of marsh vegetation (presumably the single most important source of food)

(2) Increase in deforestation (leading to loss of dinosaur habitats)

(3) General decrease in the availability of plants for food with subsequent dinosaur starvation

(4) The evolution in plants of substances poisonous to dinosaurs

(5) The loss from plants of minerals essential to dinosaur growth

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