Organism · Therians
Thylacosmilus atrox
Source time context (not species duration) · ≈ 23–2.58 Ma
Inferred life reconstruction
Thylacosmilus atrox
Overview
Thylacosmilus atrox is a South American mammal with greatly elongated upper canines. It belongs to the sparassodonts, a group distinct from cats. Even similar-looking saber teeth tell different stories when the entire head and body are considered.[1][2]
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Key facts
The long upper canines are described as continuously growing teeth. Beneath them lie elongated projections of the lower jaw. This striking pair of teeth prompted research on the skull and even the placement of the eyes.[1]
Time and place
It is known from South America around the Late Miocene and Pliocene. Fossils from present-day Argentina are studied. Its unusual head and body can be explored within the mammalian world of roughly 10 million to several million years ago.[2][4]
The time range describes source context, not the complete duration of this species.
Size, form and skeleton
Long upper canines and projections of the lower jaw are characteristic. The eye sockets lie on the sides of the head, and the back is described as stiffer than in cats. A sole-walking posture and nonretractile claws also feature in functional comparisons.[1][2]
A body-mass estimate cited in a 2020 study is approximately 117 kg.[8]
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Habitat and reproduction
There are several interpretations of how the long saber teeth were used in feeding. Researchers have compared and discussed active predation, scavenging, and the role of the tongue. This explains why the jaws, neck, and whole head are examined alongside the teeth.[2][3]
Fossil discovery
Following studies of feeding function, a 2023 study analyzed the eyes and skull. It examined how huge canines and laterally positioned eyes coexisted in one head. Research expands from the familiar image of saber teeth to other anatomical questions.[1][2]
References
- Gaillard et al. (2023) — The eyes and skull of Thylacosmilus
- Functional study of Thylacosmilus and sabre-toothed mammals
- 2020 study — The saber teeth and feeding of Thylacosmilus
- International Commission on Stratigraphy (2024) — Geological time chart
- Janis et al. (2020) — Similar saber teeth and different cranial functions
- Florida Museum — Smilodon fatalis
- Gaillard et al. (2023) — The eyes and skull of Thylacosmilus
- Janis et al. (2020) — Diet and functional morphology of Thylacosmilus
Research questions
Where would the eyes sit in an animal with large canines? Researchers compare the orientation of the eye sockets with several skull regions. They can also explore how head and body function differ from those of outwardly similar saber-toothed cats.[1][2]
Observation
Move your gaze from the long upper canines to the lower-jaw projections and eyes on the sides of the head. Then compare the back and feet to reveal the body beyond the saber teeth.[1]
Related organisms
Smilodon fatalisPlacental mammalsSource time context (not species duration) · ≈ 2.58–0 MaDo similar long canines imply the same function?
Smilodon from Pleistocene America and Thylacosmilus from Late Miocene–Pliocene South America both have conspicuous elongated upper canines. However, research comparing head and jaw structure has suggested that the two animals may not have used their saber teeth in the same way. Expanding your gaze from similar teeth to the whole head helps explore different lifestyles behind similar appearances.