Repenomamus

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Repenomamus
Temporal range:
Ma
Type of R. giganticus, Paleozoological Museum of China
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Eutriconodonta (?)
Family: Gobiconodontidae
Genus: Repenomamus
Li et al., 2000
Type species
Repenomamus robustus
Li et al., 2001[1]
Species

Repenomamus robustus Li et al., 2000
Repenomamus giganticus Hu et al., 2005

Repenomamus (Latin: "reptile" (reptilis), "mammal" (mammalis)[2]) is a genus of opossum- to badger-sized gobiconodontid[3] mammal containing two species, Repenomamus robustus and Repenomamus giganticus. Both species are known from fossils found in China that date to the early Cretaceous period, about 125-123.2 million years ago. R. robustus is one of several Mesozoic mammals[7] for which there is good evidence that it fed on vertebrates, including dinosaurs. Though it is not entirely clear whether or not these animals primarily hunted live dinosaurs or scavenged dead ones, evidence for the former is present in fossilized remains showcasing the results of what was most likely a predation attempt by R. robustus directed at a specimen of the dinosaur Psittacosaurus lujiatunensis.[8] R. giganticus is among the largest mammals known from the Mesozoic era, only surpassed by Patagomaia.

Classification and discovery

An R. robustus feeding on a Psittacosaurus hatchling.

The fossils were recovered from the

feathered dinosaurs. They have been specifically dated to 125–123.2 million years ago, during the Early Cretaceous
period.

Repenomamus is a

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

Fossil skull of R. giganticus

Individuals of the known species in Repenomamus are some of the largest known Mesozoic mammals[9][6][10][11][12][13] represented by reasonably complete fossils[10][11] (though Kollikodon and Patagomaia may be larger,[14][15] and Schowalteria, Oxlestes, Khuduklestes and Bubodens reached similar if not larger sizes[16][17]). Adults of R. robustus were the size of a Virginia opossum. It had body length without tail of 41.2 cm (16 in) for complete specimen with estimated skull length of 10.6 cm (4.2 in), although there is more partial specimen that had 11.2 cm (4.4 in) skull. Estimated mass of R. robustus is 4–6 kg (8.8–13 lb). The known adult of R. giganticus was about 50% larger than R. robustus, with a body length of 68.2 cm (27 in) and total length over 1 m (3 ft 3 in) (skull reaching 16 cm (6.3 in), trunk of 52.2 cm (21 in) and preserved tail 36.4 cm (14 in) in length) and an estimated mass of 12–14 kg (26–31 lb).[18] These finds extend considerably the known body size range of Mesozoic mammals. In fact, Repenomamus was larger than several small sympatric dromaeosaurid dinosaurs like Graciliraptor.[18][10] 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.[19]

Paleobiology

The R. robustus specimen with Psittacosaurus remains in its stomach, Paleozoological Museum of China

Features of the teeth and jaw suggest that Repenomamus were

Jugulator and even Triconodon itself[21] are thought to have tackled proportionally large prey as well; evidence of scavenging is even assigned to the former.[6]

Like most other non-

See also

References

  1. S2CID 129025369
    .
  2. ^ "Glossary. American Museum of Natural History". Archived from the original on 20 November 2021.
  3. S2CID 128782275
    .
  4. .
  5. .
  6. ^
    ISBN 978-0-231-11918-4.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  7. eutriconodonts and deltatheroidean metatherians have adaptations towards specialised carnivory[4][5][6]
  8. ^ .
  9. . Retrieved 2022-08-25.
  10. ^ . Retrieved 2022-08-25.
  11. ^ . Retrieved 2022-08-25.
  12. . Retrieved 2022-08-25.
  13. . Retrieved 2022-08-25.
  14. ^ Clemens et al., 2003
  15. .
  16. .
  17. ^ Wilson R. W. (1987). "Late Cretaceous (Fox Hills) multituberculates from the Red Owl local fauna of western South Dakota". Dakoterra. 3: 118–122.
  18. ^
    S2CID 2306428
    .[ Supplementary Information]
  19. ^ Alexey Lopatin, Alexander Averianov, Gobiconodon (Mammalia) from the Early Cretaceous of Mongolia and Revision of Gobiconodontidae, First online: 12 July 2014
  20. .
  21. ^ "Triconodon | fossil mammal genus".

External links