Near Interior in Jackson County, South Dakota — The American Midwest (Upper Plains)

Under the Sea

Photographed By Ruth VanSteenwyk, August 10, 2017

1. Under the Sea Marker

Inscription.

Ammonite fossils found in the park are evidence that this area was under water 75 million years ago. Some ammonites could grow to more that three feet across and served as a food source for giant mosasaurs and other predators.

The Western Interior Seaway once split North America in half. In some places, this vast inland sea was 2,500 feet deep and 600 miles wide.

Ammonite
Placenticeras

As the sea receded, ammonites could no longer survive in this area. Ammonites are relatives of octopuses and squid but with coiled shell over their bodies. All ammonites went extinct 65.5 million years ago.

Erected by Badlands National Park, National Park Service, U.S. Department of the Interior.

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

Location. 43° 46.325′ N, 102° 0.212′ W. Marker is near Interior, South Dakota, in Jackson County. Marker is on State Highway 234. This marker is part of the Fossil Trail Exhibit. The Fossil Trail Exhibit is located 5 miles west of the Ben Reifel Visitor Center. Touch for map. Marker is in this post office area: Interior SD 57750, United States of America. Touch for directions.

Other nearby markers. At least 8 other markers are within walking distance of

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this marker. Titanic Discovery (a few steps from this marker); See Ya Later, Alligator (a few steps from this marker); Off to the Races (a few steps from this marker); What a Find! (within shouting distance of this marker); Bands of Time (within shouting distance of this marker); Fight for Survival (within shouting distance of this marker); Dying to Become a Fossil (within shouting distance of this marker); It's a Dog's Life (within shouting distance of this marker). Touch for a list and map of all markers in Interior.

Related markers. Click here for a list of markers that are related to this marker.

Also see . . . Badlands National Park. (Submitted on January 21, 2018, by Ruth VanSteenwyk of Aberdeen, South Dakota.)

Photographed By Ruth VanSteenwyk, August 10, 2017

2. Under the Sea Marker

Fossil Trail Marker image. Click for full size.

Photographed By Ruth VanSteenwyk, August 10, 2017

3. Fossil Trail Marker

Credits. This page was last revised on January 22, 2018. It was originally submitted on January 21, 2018, by Ruth VanSteenwyk of Aberdeen, South Dakota. This page has been viewed 218 times since then and 11 times this year. Photos: 1, 2, 3. submitted on January 21, 2018, by Ruth VanSteenwyk of Aberdeen, South Dakota. • Andrew Ruppenstein was the editor who published this page.