Organism · Placental mammals
Hypertragulus calcaratus
Source time context (not species duration) · ≈ 37–18 Ma
Inferred life reconstruction
Hypertragulus calcaratus
Overview
Hypertragulus calcaratus is a fossil mammal of Oligocene North America. Skulls, limbs, and vertebrae remain as research material. Comparing heads and legs among similar animals reveals an ancient body arrangement.[1][2]
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Key facts
Look for two hindlimb bones of similar length. A researcher in 2001 described the femur and tibia of this species as almost equal in length. Dividing a leg into its upper and lower bones rather than viewing it only as a whole offers a way to explore proportions.[2]
Time and place
Fossil material is known from present-day South Dakota, USA. Smithsonian records introduce Oligocene occurrences in the Brule Formation and White River Group. The Oligocene spanned approximately 34–23 million years ago.[1][3]
The time range describes source context, not the complete duration of this species.
Size, form and skeleton
The species is studied through comparative skull and limb material. Descriptions of hypertragulids include a narrowing snout and slender humerus and radius. Head outline and forelimb and hindlimb arrangements provide different clues for body comparison.[2]
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Habitat and reproduction
Leg bones connected across joints invite investigation of support and movement. Research comparing femur and tibia lengths provides a starting point for such questions. Placing the limbs of related groups side by side reveals different proportions.[2]
Fossil discovery
The Smithsonian records skull, limb, and vertebral material together with the fossil-bearing strata. A 2001 skeletal comparison includes specimens such as AMNH 53802 and AMNH 53082, showing different head regions. Institutional specimens become connected through comparative research.[1][2]
References
- Smithsonian — Skeletal material of Hypertragulus calcaratus
- Vislobokova (2001) — Evolution and skeletal comparison of Tragulina
- International Commission on Stratigraphy (2024) — Geological time chart
- 2021 study — The skull of Palaeolagus examined with CT
- Smithsonian — Fossil record of Palaeolagus haydeni
- Smithsonian — Skeletal material of Hypertragulus calcaratus
- International Commission on Stratigraphy (2024) — Geological time chart
- Vislobokova (2001) — Evolution and skeletal comparison of Tragulina
Research questions
How do the heads and legs of similar mammals differ? Snouts, bones around the ears, forelimbs, and hindlimbs can be compared separately. The research examines proportions within one body alongside differences among related groups.[2]
Observation
After examining the snout outline, move your gaze to the forelimbs and hindlimbs. In the hindlimb, picture where femur and tibia connect to make their length comparison easier to understand.[2]
Related organisms
Palaeolagus haydeniPlacental mammalsSource time context (not species duration) · ≈ 33.9–23 MaDifferent mammals of Oligocene North America
Palaeolagus and Hypertragulus are known from Oligocene material in present-day Wyoming, South Dakota, and elsewhere in the USA. Follow the names White River Group and Brule Formation to read studies of heads and limbs in a rabbit relative alongside those of another mammal.