Organism · Placental mammals
Pachyarmatherium leiseyi
Fossil record age bounds · ≈ 4.7–0.129 Ma
Inferred life reconstruction
Pachyarmatherium leiseyi
Overview
Pachyarmatherium leiseyi is a fossil mammal with thick armor made of bony plates. A narrow overlap separates the shoulder and pelvic portions of the armor. Even within a hard covering, distinct regions have different structures.[2]
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Key facts
The armor was not simply one continuous shell. A narrow, band-like overlap lay between the shoulder and pelvic sections, and plates from the margins and tail were also distinguished. Small pieces reveal different parts of the body covering.[2]
Time and place
The institution’s type-specimen catalogue records this species as early Pleistocene. The Pleistocene as a whole spans roughly 2.6 million to 12,000 years ago. The name established in 1995 and holotype UF 64347 anchor the record.[1][3]
The time range describes source context, not the complete duration of this species.
Size, form and skeleton
Descriptions include thick armor, shoulder and pelvic sections, and a narrow overlapping band between them. Marginal and tail plates are also treated as distinctive features. Separately assigned skeletal material includes claw-bearing terminal finger and toe bones and records of isolated back vertebrae.[2]
A 2005 study calculated a body mass of approximately 15.4 kg for Pachyarmatherium leiseyi. Estimated from a 15 cm long femur, the value helps convey the size of this heavily armored animal.[4]
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Habitat and reproduction
How did the structure vary across its hard armor? The shoulder section, pelvic section, and overlap between them can be examined separately. The connections between the body-covering plates are themselves a research question.[2]
Fossil discovery
Downing and White described this animal in 1995. The original description covers armor sections, marginal and tail plates, and assigned skeletal material. The institution’s type catalogue records UF 64347 as the name-bearing specimen.[1][2]
References
- Florida Museum of Natural History — Catalogue of Pachyarmatherium type specimens
- Downing·White (1995) — Armor and skeleton of Pachyarmatherium
- International Commission on Stratigraphy (2024) — Geological time chart
- McDonald(2005) — Body size and evolution of North American edentates
- McDonald(2005) — Body size and evolution of North American edentates
- Study of Eutatus species morphology and climate
- Limb reconstruction and palaeobiological study of Eutatus seguini
- Paleobiology Database — Age of fossil-bearing strata of Eutatus
- Vizcaíno·Milne·Bargo (2003) — Reconstruction of the limbs of Eutatus
Research questions
How can scattered plates be assigned to particular body regions? Comparing marginal and tail features provides clues to their positions. This is a case of exploring an entire suit of armor through small fossil fragments.[2]
Observation
Move your gaze from the shoulder armor across the narrow overlap to the pelvic region. Considering marginal and tail plates separately helps distinguish the different regions of the hard covering.[2]
Related organisms
Eutatus seguiniPlacental mammalsSource time context (not species duration) · ≈ 8–0.012 MaAncient mammal armor and the skeleton beneath
Explore different records of bodies and time in these two animals. Pachyarmatherium leiseyi: a fossil mammal with thick bony armor and a narrow overlap between the shoulder and pelvic sections. The institution’s type-specimen catalogue records it as early Pleistocene; the Pleistocene as a whole spans roughly 2.6 million to 12,000 years ago. Eutatus: Eutatus seguini is a fossil mammal studied through armor, internal skeletal material, and limbs. Studies have also compared its limbs with living armadillos. Recorded fossil-bearing strata are summarized as roughly 8 million to 12,000 years ago, spanning the Miocene to Pleistocene. Studies of the armor, internal skeleton, and limbs provide clues to this animal.