Repenomamus
Life image of Repenomamus giganticus
- China (Liaoning ) Yixian Formation of the Jehol Group
- R. robustus Li, Wang, Wang, Li, 2000
- R. giganticus Hu, Meng, Wang, Li, 2005
Repenomamus is an extinct mammal genus from the lower Cretaceous. These animals were carnivores and the largest previously known mammals of the Mesozoic. Two species have been described, R. robustus and R. giganticus that differ in terms of size and details in skull structure.
Features
R. giganticus reached a body length of about 60 centimeters ( 16 inches long the skull was ). Its length including the tail should have amounted to over 1 meter, its weight is estimated at 12 to 14 kilograms. R. robustus was about half the size and was probably 4 to 6 kilograms. Thus, they were the largest known mammals of the Mesozoic. Only Kollikodon, an early representative of the monotremes could have reached similar proportions of this genus but are just jaw parts known to make an accurate estimate of the size impossible.
Repenomamus had an elongated torso, short, strong limbs were placed in comparison with modern mammals lateral to the body. The animals were plantigrade, the construction of the limbs indicates a ground-dwelling lifestyle.
The large head is likely to have houses a powerful jaw muscles. The construction of the teeth suggests a carnal diet. The incisors, canines and Vorbackenzähne were large and pointed, and suitable for holding and tearing prey. The molars, however, were rather small and dull, they were not very suitable for chewing, so that the animals might have swallowed their food rather as a whole. The dental formula was I 3/ 2 C 1/1 P 2 /2 M 4/5. Well-preserved remains of R. robustus even still left the stomach content see next mammal bones and the remains of a young Psittacosaurus have been found - this is an amazing evidence that Mesozoic mammals have eaten dinosaurs. It was discussed whether Repenomamus might have been a scavenger, but the approaches of the masticatory muscles and the formation of the teeth suggest a predatory lifestyle.
Discovery
Remains of Repenomamus were in the Yixian Formation of Liaoning Province - which is also known for their feathered dinosaur - and found in the lower Cretaceous period ( approximately 139-128 million years) dated. R. robustus was described by Jinling Li, Yuan Wang, Yuanqing Wang and Li Chuankui in 2000; R. giganticus of Yaoming Hu, Jin Meng, Yuanqing Wang and Li Chuankui in 2005.
System
The closest relatives of Repenomamus are representative of Gobiconodontidae, a well-known from the Lower Cretaceous of Asia and North America group of carnivorous mammals. In some classifications Repenomamus is classified in this family, out in other than their own family, Repenomamidae. The position as a separate family is justified by differences in construction and number of teeth, but it is well established that Repenomamus and Gobiconodontidae are closely related.
Together with some other Mesozoic mammals, which are characterized by a similar dreihöckrigen construction of the molars, they are classified in the group of Eutriconodonta. Whether it really is, however, closely related animals or just to convergent developments, is controversial. Their position in the scheme of mammals is unclear, it is likely to have, however, been a relatively early, specialized side branch. With today's mammals are not closely related.
Significance of the find
Until recently, it held almost all mammals of the Mesozoic for small, relatively unspecialized animals that were mostly nocturnal insectivores. The findings of Repenomamus show that the mammalian epoch were significantly larger than previously thought and may compete with smaller dinosaurs for food and hunting grounds. The findings fit into a series of discoveries of recent times (such as adapted to aquatic life species Castorocauda that ameisenbärähnliche genus Fruitafossor or provided with Gleitmembranen Volaticotherium ), demonstrating that the Mesozoic mammals were specialized and occupy even more diverse ecological niches than previously assumed.