| Repenomamus Temporal range: Early Cretaceous | |
|---|---|
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| A restoration of Repenomamus robustus eating a "psittacosaurus" hatchling. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | †Gobiconodonta |
| Family: | †Gobiconodontidae |
| Genus: | †Repenomamus Li et al., 2000 |
| Type species | |
| †Repenomamus robustus Li et al., 2000 | |
| Referred species | |
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Repenomamus ("reptilian mammal") is a genus of mammals from Cretaceous China. Repenomamus contains two species; one is cat-sized Repenomamus robustus and the other almost badger-sized Repenomamus giganticus. Both species fossils found in China that date to the early Cretaceous period, about 125-123.2 million years ago. Indicating quite significant advancement for mammalians in the age of dinosaurs. Despite how it is showed in media, they where still quite small compared to a human.
Classification and discovery[]
The fossils were recovered from the lagerstätte of the Yixian Formation in the Liaoning province of China, which is renowned for its extraordinarily well-preserved fossils of feathered dinosaurs. They have been specifically dated to 125–123.2 million years ago, during the Early Cretaceous period.
Repenomamus is a genus of triconodonts, a group of early mammals with no modern relatives. R. robustus was described by Li, Wang, Wang and Li in 2000, and R. giganticus was described by Hu, Meng, Wang and Li in 2005. The two known species are the sole members of the family Repenomamidae, which was also described in the same paper in 2000. It is sometimes alternatively listed as a member of the family Gobiconodontidae; although this assignment is controversial, a close relationship to this family is well-founded.
Description[]
Individuals of the known species in Repenomamus are the largest known Mesozoic mammals represented by reasonably complete fossils. However, other mammals such as Oxelestes and Kolikodon the monotreme both reached around the same or even the larger than Repenomamus. Adults of R. robustus were the size of a Virginia opossum with an estimated mass of 4–6 kg (8.8–13 lb) while the known adult of R. giganticus was about 50% larger with a total length of around 1 m (3 ft 3 in) and an estimated mass of 12–14 kg (26–31 lb). These finds extend considerably the known body size range of Mesozoic mammals. In fact, Repenomamus was larger than several small sympatric dromaeosaurid dinosaurs like the genus Graciliraptor. Features of its shoulder and legs bones indicate a sprawling posture as in most of small to medium sized living therian mammals, with plantigrade feet. Unlike therian mammals, Repenomamus had a proportionally longer body with shorter limbs.
The dental formula was originally interpreted as 3.1.2.42.1.2.5, though a more recent study indicates instead that it was 3.1.1.52.1.2.5.
Paleobiology[]
Despite its looks, features of the teeth and jaw suggest that Repenomamus species were carnivorous and a specimen of R. robustus discovered with the fragmentary skeleton of a juvenile Psittacosaurus preserved in its stomach represents the second direct evidence that at least some Mesozoic mammals were carnivorous and fed on other vertebrates, including dinosaurs; a recorded attack on an Archaeornithoides by a Deltatheridium predates its description. Speciations towards carnivory are known in eutriconodonts as a whole, and similarly large sized species like Gobiconodon, Jugulator and even Triconodon itself are thought to have tackled proportionally large prey as well; evidence of scavenging is even assigned to the former.
Like most other non-therian mammals, Repenomamus species had epipubic bones, meaning that it laid eggs that hatched into undeveloped young like all-non-therians.
In popular culture[]
- Repenomamus robustus appeared in the movie Dino King. They are depicted as mice, when in reality, they could eat small and young dinosaurs.
- Repenomamus robustus appeared in the documentary Mammals vs. Dinos.
- Repenomamus robustus was originally supposed to appear in a Yixian segment for Dinosaur Revolution but was ultimately cut. Its portrayal is based on the Honey Badger. It is shown attacking the protagonist Raptorex and a pack of Psittacosaurus.