March 25, 1999

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Photo caption This artistic reconstruction shows Jeholodens jenkinsi, a triconodont mammal that lived about 120 to 140 million years ago during the Mesozoic. The animal has three cusps on its teeth and fed on insects and aquatic arthropods. It lived near a shallow fresh water lake and co-existed with a very rich fauna of fish, amphibians, feathered dinosaurs, birds, and lizards, plus very abundant plants and insects. Its sprawling hind legs and pelvis had a reptilian posture, yet its forearms and shoulders were more flexible. The animal is a ground-living mammal, suggesting that mammals probably originated from ground (instead of tree) habitat. The reconstruction shows how the animal would look in life, in contrast to the fossil skeleton of the same specimen preserved in the sedimentary rock. Illustration Credit: Mark A. Klingler

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Photo caption Jeholodens jenkinsi is located on the base of the mammalian family tree. It is a triconodont mammal that is characterized by three cusps on its cheek teeth. Triconodonts, of which Jeholodens jenkinsi is the best representative, are considered to be more primitive than any living mammals by the latest study published in NATURE by an international team of scientists from the Carnegie Museum of Natural History of Pittsburgh and National Geological Museum of China. On the mammalian family tree (or cladogram), the new mammal Jeholodens is outside (and to the left field) of the egg-laying monotremes and live-birth therian mammals that include humans. Although Jeholodens jenkinsi lived between 120 to 140 million years ago, other triconodont-like mammals can be traced back to 220 million of years ago. Illustration Credit: Mark A. Klingler

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Photo caption The skeleton of Jeholodens jenkinsi is an unprecedented find. It is the earliest known complete skeleton of the triconodont mammals that were diverse in the Mesozoic times. The sharp and fragile teeth of Jeholodens show that it ate insects. Its sprawling hind legs had a primitive reptilian posture, yet its forearms and shoulders were more flexible, like living therian mammals (such as opossum). The animal was a ground-living mammal, suggesting that mammals probably originated from ground (instead of tree) habitat. Illustration Credit: Mark A. Klingler

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Photo caption The type specimen Jeholodens jenkinsi is represented by a nearly complete skeleton, preserved in 140-120 million-year-old lake sediments. It is the earliest known complete skeleton of the triconodont mammals that were diverse in Mesozoic times. Illustration Credit: Mark A. Klingler

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Photo Caption The nearly complete skeleton of Jeholodens jenkinsi, an extinct symmetrodont mammal that lived about 120 to 140 million years ago during the Mesozoic Era, was unearthed in 1994 near the village of Si-He-Tun, northeast of Chao-Yang in China's Liaoning Province. This is the second fossil mammal skeleton to be found in the fossil sites that produced the famous Chinese "feathered dinosaurs." Illustration Credit: Mark A. Klingler