Rapid City in Pennington County, South Dakota — The American Midwest (Upper Plains)

Dimetrodon

(Dimetrodon limbatus)

— Then and Now —

Dimetrodon Marker image. Click for full size.

Photographed by William Fischer, Jr., September 20, 2026

1. Dimetrodon Marker

Inscription.

SIZE: 10 feet long & 5 feet tall
WEIGHT: 60-550 lbs
DIET: Carnivore
NAME MEANING: Two Measures of Teeth
[DINOSAUR] ANIMAL CLASSIFICATION: Sphenacodontidae
TIME PERIOD: Early Permian (298-272 million years ago)
MOVEMENT: Quadrupedal

QUICK FACTS:
① Dimetrodon is not actually classified as a dinosaur. It belongs to a group called synapsids which includes mammals and their relatives.

② While it is reptile-like in appearance, it is more closely related to mammals than to modern reptiles, though it is not a direct ancestor of mammals.

③ The Dimetrodon became extinct 40 million years before the appearance of the first dinosaurs.

④ The iconic sail on its back is created by elongated vertebrae and is called a neural spine sail.

⑤ The ridge was a temperature regulating mechanism, allowing the animal to warm quickly in morning sun and cool in the shade.

⑥ Its tail included around 50 caudal vertebrae, the extra vertebrae that make up the tails of animals.

⑦ At least 20 species of Dimetrodon have been named since the genus was first described in 1878.

⑧ Dimetrodon was

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an apex predator in its time and fed on fish, reptiles, and amphibians.

THEN [2000s? photo of the sculpture]

NOW [Modern artist rendition of the dinosaur]
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DIMETRODON
A flesh-eating reptile which lived long before any of the true dinosaurs shown here
Most specimens found in Texas
Age: Early Permian - 260 million years ago

Erected by City of Rapid City.

Topics. This historical marker is listed in these topic lists: Paleontology • Parks & Recreational Areas.

Location. 44° 4.672′ N, 103° 14.656′ W. Marker is in Rapid City, South Dakota, in Pennington County. Markers and sculpture are near the Dinosaur Park Gift Shop. Touch for map. Marker is at or near this postal address: 940 Skyline Drive, Rapid City SD 57701, United States of America. Touch for directions.

Regionally, this marker is in West River

and in the Badlands.

It is also in the American Black Hills,

in the Lewis & Clark Corridor,

on the prairies,

and on the Northern Plains.

Globally, it is in North America,

the Western Hemisphere,

the Western World,

and the Anglosphere.

Photographed by William Fischer, Jr., September 20, 2026

2. Dimetrodon Marker

Earlier marker near the sculpture

Historically, it finds itself in what was once Rupert’s Land

and also the Louisiana Purchase.

Other nearby markers. At least 8 other markers are within walking distance of this marker: Protoceratops (a few steps from this marker); Dinosaur Park History & Creation (within shouting distance of this marker); Works Progress Administration (within shouting distance of this marker); Trachodon (within shouting distance of this marker); Stegosaurus (about 400 feet away, measured in a direct line); Apatosaurus (about 400 feet away); Tyrannosaurus Rex (about 400 feet away); Triceratops (about 400 feet away). Touch for a list and map of all markers in Rapid City.

Dimetrodon Marker and Sculpture image. Click for full size.

Photographed by William Fischer, Jr., September 20, 2026

3. Dimetrodon Marker and Sculpture

Dimetrodon Markers and Sculpture image. Click for full size.

Photographed by William Fischer, Jr., September 20, 2026

4. Dimetrodon Markers and Sculpture

Credits. This page was last revised on October 10, 2026. It was originally submitted on October 10, 2026, by William Fischer, Jr. of Reynoldsburg, Ohio. This page has been viewed 6 times since then. Photos: 1, 2, 3, 4. submitted on October 10, 2026, by William Fischer, Jr. of Reynoldsburg, Ohio.