The real reason the dinosaurs became extinct

Not every published hypothesis has been serious. In 1964, for example, E. Baldwin suggested that the dinosaurs died of constipation. His reasoning went as follows. Toward the end ofthe Cretaceous, there was a restriction in the distribution of certain plants containing natural laxative oils necessary for dinosaur regularity. As the plants became geographically restricted, those unfortunate dinosaurs living in places where the necessary plants no longer existed acquired stopped plumbing and died hard deaths. The same year, humorist W. Cuppy noted that "the Age of Reptiles ended because it had gone on long enough and it was all a mistake in the first place," a view with which many characters in the Jurassic Park series would have probably agreed.

The November, 1981 issue ofthe National Lampoon offered its explanation, entitled "Sin in the Sediment." The Christian right was the target:

It's pretty obvious ifyou just examine the remains of the dinosaurs . . . Dig down into older sediments and you'll see that the dinosaurs were pretty well off until the end ofthe Mesozoic. They were decent, moral creatures, just going about their daily business. But look at the end ofthe Mesozoic and you begin to see evidence of stunning moral decline. Bones ofwives and children all alone, with the philandering husband's bones nowhere in sight. Heaps of fossilized, unhatched, aborted dinosaur eggs. Males and females of different species living together in unnatural defiance of biblical law. Researchers have even excavated entire orgies - hundreds of animals with their bones intertwined in lewd positions. Immorality was rampant.

In 1983, sedimentary geologist R. H. Dott Jr published a short note in which he vented his frustrations with the pollen season, suggesting that it was pollen in the atmosphere that killed the dinosaurs. He called his contribution "Itching Eyes and Dinosaur Demise."

The issues raised by the National Lampoon were compelling enough to again be raised in 1988 by the Journal of \rreproducible Results. There, L. J. Blincoe developed a new hypothesis about the "fighting dinosaurs" specimen (see Figure 9.22):

A thorough but cursory review of fossil specimens . . . has revealed a unique fossil found in the Cretaceous "beds" of Mongolia in 1971. The fossil featured two different species of dinosaur, one a saurischian carnivore (Velociraptor), the other an ornithischian herbivore [sic] (Protoceratops), in close association at the moment of their deaths. Prejudiced by their preconceived notions of dinosaur behavior, paleontologists have almost unanimously interpreted this find as evidence of a life and death struggle [see Chapter 11] . . . However, an alternative theory has now been developed which not only explains this unusual fossil, but also answers the riddle ofthe dinosaurs disappearance. Quite simply, when their lives were ended by sudden catastrophe, these two creatures were locked together . . . in a passionate embrace. They were, in fact, prehistoric lovers.

The mammals that evolved throughout the recovery at the K/T boundary were extremely small generalists. They speciated rapidly, taking about 5 million years (Figure 15.17) to evolve a range of sizes and develop specializations (such as herbivores and carnivores). Theirs is the pattern of a disaster fauna that came through a catastrophic event and inherited deserted ecospace.

Recent phylogenies based upon the rates of molecular evolution have suggested that modern mammals' roots are to be found within the Cretaceous, implying that the mammalian radiation that characterized the Tertiary was actually well underway during the latest Cretaceous. In fact, the far-distant ancestors of modern mammals were likely around during the Late Cretaceous, but the rapid species' turnovers of the earliest Tertiary disaster faunas shows the clear mark of a catastrophic event.

Does the asteroid impact hypothesis explain all the data? In fact, there does appear to be a correlation between extinction selectivity and the asteroid as a causal agent in the extinctions.


Reasons Dinosaurs Became Extinct
Figure B15.3.1. O' Donnell's tale on the cause of extinction of dinosaurs.

The implications of this startling interpretation are clear: dinosaurs engaged in trans-species sexual activity. In doing so they wasted their procreative energy on evolutionary pointless copulation that resulted in either no offspring or, perhaps on rare occasions, in bizarre, sterile mutations (the fossil record is replete with candidates for this later category.1

For the ultimate causes of the extinction, however, we think O'Donnell's perspective published in the New Yorker says it all.

1. Blincoe, L. J. 1988. Journal of Irreproducible Results, p. 24.

Those marine creatures that suffered the most extinctions were those that depended directly upon primary productivity for their food source. Such creatures included not only the planktonic foraminifera and other planktonic marine microorganisms, but also ammonites, other cephalopods, and a variety of mollusks. On the other hand, organisms that not only depended on primary productivity but could also survive on detritus, that is the scavenged remains of other organisms, fared consistently better. In marine deposits, detritus-feeders were apparently less affected by the extinction.

In the terrestrial realm, the strong selectivity between land-dwelling and aquatic tetra-pod survival (see Figure 15.13) correlates with feeding strategy: aquatic vertebrates tend to utilize detritus as a major source of nutrients, while land-dwelling veterbrates are far more dependent upon primary productivity. The tetrapods that survived the K/T boundary were primarily aquatic detritus-feeders. This is because river and lake systems can serve as a repository for detrital material, and organisms that live in such environments and can utilize this resource were protected against short-term drops in primary productivity. They may also have been protected from the strong infra-red radiation pulse, as well as the wildfires.

One group of terrestrial tetrapods for which there are virtually no data are avian dinosaurs (birds). We know that this group, like mammals, suffered very significant extinctions; yet obviously some birds survived. Their survival may have been tied into an ability to fly and seek refuge, it may have been dumb luck, or it may have been something that we have not yet recognized. The sparse fossil record of birds makes understanding the dynamics of the K/T boundary as it relates to birds very difficult.

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  • marco
    How dinosaurs became extinct orgy?
    9 years ago
  • semira
    What is the real reason that dinosaurs became extinct?
    2 years ago

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