Organism · Reptiles including birds
Trinacromerum bentonianum
Source time context (not species duration) · ≈ 143–66 Ma
Inferred life reconstruction
Trinacromerum bentonianum
Overview
Trinacromerum bentonianum was a Late Cretaceous marine reptile. It is studied through fossils of the head, vertebrae, shoulder and pelvic girdles, and flipper-shaped limbs. Comparing body parts from several specimens helps reveal the construction of this underwater reptile.[1]
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Key facts
Even a single front flipper was a limb made of many connected bones. ESU5000 preserves the described form of an articulated right forepaddle. Within the broad flipper's outer outline, imagine the connected structure of the limb bones.[1]
Time and place
Several specimens were described in research on plesiosaur fossils from North America's Fort Benton Group. This species is studied from Late Cretaceous material. The Cretaceous as a whole spans roughly 140–66 million years ago.[1][2]
The time range describes source context, not the complete duration of this species.
Size, form and skeleton
USNM10945 records a partial snout and lower jaw, the junction between head and neck, vertebrae, and parts of the shoulder girdle, pelvis and limbs. ESU5000 provides evidence of the articulated structure of the right forepaddle. The connections from the head to the trunk and limbs can be examined part by part.[1]
The trunk length used in a comparative study is about 1.55 m. This is distinct from total body length, which also includes the head, neck and tail.[3]
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Habitat and reproduction
The front and rear limbs of marine reptiles are studied as paddle-shaped structures. Examining how the shoulder and pelvic girdles meet the limbs helps researchers explore the connections between the trunk and flippers. The articulated forepaddle provides concrete evidence for such comparisons.[1]
Fossil discovery
A 2005 study redescribed several plesiosaur specimens from the Fort Benton Group. The history of ESU5000 also records that most of the associated skeleton was stolen. Earlier descriptions and collection records, as well as surviving fossils, allow research to continue.[1]
References
- Schumacher & Everhart (2005) — Plesiosaur fossils of the Fort Benton Group
- International Commission on Stratigraphy (2024) — Geological time chart
- Pimiento et al. (2024) — Extinct large marine organisms of the Phanerozoic
- NHM — What is a plesiosaur?
- Sachs, Kear & Everhart (2013), Revised Vertebral Count in the Long-Necked Plesiosaurian Elasmosaurus platyurus, PLOS ONE 8(8):e70877.
Research questions
What features might the head, foreflipper, shoulder girdle and pelvis each reveal? Comparing the same body parts across specimens can provide clues for distinguishing similar marine reptiles. Such research examines both the body's overall outline and its smaller anatomical connections.[1]
Observation
Move your gaze from the head along the vertebral column to the trunk, then to the shoulder girdle and front flipper. Keeping the pelvis and rear flippers in mind as well helps you understand this underwater reptile part by part.[1]
Related organisms
Elasmosaurus platyurusReptiles including birdsSource time context (not species duration) · ≈ 84–72 MaDifferent body forms among marine reptiles
Explore the bodies and living contexts of Trinacromerum bentonianum and Elasmosaurus platyurus together. Trinacromerum bentonianum: Trinacromerum bentonianum was a Late Cretaceous marine reptile. It is studied through fossils of the head, vertebrae, shoulder and pelvic girdles, and flipper-shaped limbs. Elasmosaurus platyurus: This marine reptile is striking for its small head, long neck and four flippers arranged along the two sides of the body. Elasmosaurus platyurus is a representative plesiosaur of the seas of the dinosaur age.