Creatures That Time Forgot: Living Fossils
from the book, "Petrified Lightning"
Creatures That Time Forgot: Living Fossils
Rumors of dinosaurs, sea serpents, and other fantasies appearing in remote corners of the globe crop up frequently in newspapers, magazines, and especially tabloids. No one can squelch the hope that dinosaurs still cling to life on some unexplored island; the idea that ancient forms still exist appeals to almost everyone. This hope explains the popularity of Arthur Conan Doyle's 1912 classic Lost World and of movies such as King Kong in 1932. Just how, we wonder, would a prehistoric giant dinosaur react if it were turned loose in civilization?
Occasionally a scientist describes an animal or plant as a "living fossil." This label is an oxymoron, because a fossil is something long dead, and no living plant or animal would qualify as a fossil. A living fossil, however, is a living remnant of a long—gone era. This animal or plant is a species that has survived long past the era in which it flourished. In the distant geologic past, usually the family to which this plant or animal belongs was once quite abundant and widespread. Often the survivor has changed little in appearance from its remote ancestors, and the name "living fossil" describes it appropriately. These creatures interest scientists because they provide immense knowledge regarding the appearance of ancient extinct forms. The study of modern survivors has shed light on many an unsolved problem.
Happily this type of creature is not all that rare. Many species are known that have lived long beyond their time with few physical changes from the antediluvian types. The Sphenodon of New Zealand, known commonly as the tuatara, is an excellent example of a living fossil. Outwardly it looks like a lizard, but it is unique in many ways. Of many skeletal differences between the tuatara and modern lizards, the most unusual is a third eye, the pineal eye, on top of its head that is a sensory organ. The tuatara is the sole surviving species of a once great order of reptiles scientifically classified as rhynchocephalian (beak head). This reptilian group appeared on earth during the Triassic, the first period of the age of dinosaurs. Fossil records show that this period witnessed the greatest expansion and development of the order and the spread of rhynchocephalians throughout the world. They began to dwindle after the end of the Triassic Period, and their evolutionary line continued along a very limited sphere.
Very little physical change has taken place in the rhynchocephalian for over 150 million years. Except for the living species of tuatara found only in New Zealand, the entire group is now extinct. With the coming of Europeans to New Zealand, even this one species was threatened with the same fate as its ancestors. As civilization quickly spread over the land, the tuatara began to disappear at an alarming rate. It was on the verge of extinction when conservation authorities took the survivors under scrutiny, and they now are rigidly protected.
The modern king crab, Limulus, is another survivor from the past. Its earliest ancestors are found in rocks well over 500 million years old from the period geologists call the Ordovician. From that time until the Mesozoic (age of dinosaurs), this group branched out prolifically. Although its fossil history is not thoroughly known, its close resemblance to extinct primeval forms and its being the sole surviving genus of a once great order truly classifies Limulus as a living fossil.
What truly captures the attention of the public is the discovery of a living animal whose species has been thought to have been completely extinct for millions of years. Although once a great group of invertebrates, today only one genus, which includes four species, survives. Another living fossil was discovered by a fisherman in 1938. Retrieving his heavily laden fishnets at the mouth of the Chalumna River in South Africa, the man found a strange—looking fish flopping around among the ordinary fish in the net that measured over five feet in length and topped 110 pounds. The weird appearance of this creature caused him to turn it over to Marjorie Latimer, the curator of the museum at East London, South Africa. She also had never seen one like it before, nor was she familiar with any fish of its description. Fascinated, she wrote to James L. B. Smith, the leading fish expert in South Africa.
When Professor Smith finally arrived more than a week later, the now mounted fish was presented to him. His astonishment knew no bounds, for he recognized a creature that was supposed to have vanished completely from the face of the earth some 70 million years ago. This lobe—finned fish was a coelacanth, a type of Crossopterygii. The Crossopterygiian order had crawled out of the waters on its lobe fins about 400 million years ago to become the first land—dwelling vertebrate.
Smith had only the muscles, skin, and parts of the skeleton to compare with coelacanths from the fossil record, which are not uncommon. He considered the loss of internal organs catastrophic for his study but reasoned, correctly, that others would be found. Not until December 20, 1952, fourteen years later, did his prediction come true. By that time he was offering a reward of sterling