Notharctus tenebrosus 1870
A small 2.5 in (6 cm) fossil jaw was collected by Ferdinand V. Hayden (2) during his geological survey of southwestern Wyoming in 1870. Leidy first identified it as some kind of small carnivore. But Leidy later noted that the jaw was found in association with numerous pachyderm fossils and concluded that it too probably belonged to a small pachyderm (3).
Lower right jaw of Notharctus tenebrosus. The actual size is 2.5 in (6 cm). This image is a detail of a lithograph published in "Extinct Vertebrate Fauna of the Western Territories" (1873). Click here or on the image to view the full lithograph.
Leidy provided a detailed description of the Notharctus jaw in "Extinct Vertebrate Fauna of the Western Territories" (1873). At the end of his description he states —almost as an aside— that Notharctus looks a lot like a primate:
"In many respects, the lower jaw of Notharctus resembles that of the existing American monkeys quite as much as it does any living pachyderm."
Remarkably, he continues this discussion with the observation that minor evolutionary modifications would result in jaws that resembled those of modern monkeys, apes and humans:
"The resemblance is so close that but little change would be necessary to evolve from the jaw and teeth of Notharctus that of a modern monkey. The same condition which would lead to the suppression of a first premolar, in continuance would reduce the fangs of the other premolars to a single one. This change, with a concomitant shortening and increase of depth of the jaw, would give the characters of a living Cebus. A further reduction of a single premolar would give rise to the condition of the jaw in the Old World apes and man."
Unfortunately, Leidy largely abandoned paleontology shortly after these comments were published. So we don't know whether he was ultimately convinced that Northarctus was a primate. As it turns out, several other small fossils animals from the Fort Bridger area (Hipposyus, Limnotherium, Telemalestes, Telmatolestes, Thinolestes and Tomitherium) have been re-identified as Notharctus (4). The identity of Northactus as a primate was firmly established following Walter Granger's (5) discovery of a nearly complete skeleton in Wyoming.
Notharctus belonged to a group of extinct primates known as the adapids. These Eocene primates have been found in North America and Europe. Adapids were among the first primates to have a set of adaptations suited for life in the trees. These include grasping hands, flexible backs, and binocular vision. They most resemble the modern-day lemurs of Madagascar. Notharctus was about 16 in (40 cm) long, excluding the tail.
Websites:
- American Museum of Natural History's web page on Notharctus:
www.amnh.org/exhibitions/expeditions/treasure_fossil/
Fossils/Specimens/notharctus.html
Notes:
- Etymology:
Notharctus (no-THARKT-us) = false bear
tenebrosus (TEH-knee-BROE-sus) = dark, gloomy
[go back] - Ferdinand V. Hayden had been collecting fossils for Leidy for many years. Many
of these were provided during his geological survey for the United States government.
from the late 1860s and 1870s. For more information go to Leidy's
Fossil Collectors.
[go back] - Pachyderm
literally means "thick skin". It is generally used for naming large,
thick-skinned mammals such as elephants, rhinos and hippos. Leidy and other 19th
century scientists used it to name hoofed mammals that were probably related to
elephants, perissodactyls (odd-toed ungulates such as horses, tapirs and rhinos)
or artiodactyls (even-toed ungulates such as pigs, hippos, cows and deer).
[go back] - One
reason for the multitude of names given to Notharctus was the frantic naming
competition between O.C. Marsh and E.D. Cope. Another, however is the fragmentary
nature of the fossils themselves. They commonly consisted of isolated teeth or
small jaw fragments. Indeed, Leidy himself identified several other primate teeth
and bone fragments as belonging to insectivores (the group of primitive mammals
most closely to primates) or to "pachyderms".
[go back] - Walter
Granger was a paleontologist who worked at the American Museum of Natural History
in New York from 1894 to 1941. He was responsible for many of their important
paleontological discoveries in North America and was the first major American
paleontologist to explore China and Mongolia.
[go back]