Fossils

The Paleontology of Camp Nelson

 

A diorama reconstruction of the Late Ordovician Period seafloor.

Flickr/ James St. John

Eons Before Emancipation

The history of Camp Nelson goes back way farther than the Civil War, over 435 million years in fact! Millions of years ago during the Late Ordovician Period, the land in and around what we know as Camp Nelson National Monument today was on the submerged continental shelf off the coast of the paleocontinent Laurentia. Essentially, this area was a shallow sub-tropical sea teeming with life! Remnants of this oceanic past can be found all throughout Camp Nelson and remind us of what life looked like for those who inhabited this region all those years ago.

Set in Stone

There is a wide variety of animals fossilized in the rocks of Camp Nelson National Monument, painting a picture of the shallow marine environment this area used to be. Brachiopods, bivalves, bryozoans, corals, crinoids, gastropods, nautiloids, and ostracods have all been documented within the national monument, and even more animals are known from the same rocks just outside of Camp Nelsons boundaries!

 

Left image
Modern brachiopod shell
Credit: Flickr/ James St. John

Right image
Fossilized brachiopods at Camp Nelson
Credit: NPS/ A. Goetz

Brachiopods, also known as “lamp shells”, are two shelled filter feeders that share similar appearances with bivalves. These animals were much more common than bivalves during the Ordovician however, and often out competed bivalves for living spaces on the seafloor or attached to rocks.

 

Left image
Modern bivalve shell
Credit: Flickr/ James St. John

Right image
Fossilized bivalve shells at Camp Nelson
Credit: NPS/ E. Jackson

Bivalves, a group of two-shelled animals that include many still living organisms such as clams, oysters, muscles, scallops, etc., were present during the Ordovician, though they were much less common than they are today.

 

Left image
Modern encrusting bryozoan
Credit: INaturalist/ Al Kordesch

Right image
Fossilized bryozoan at Camp Nelson
Credit: NPS/ E. Jackson

Bryozoans, also called “moss animals”, are tiny colonial filter feeders that build intricate, often lace-like structures in which they live. A colony of bryozoans can have anywhere from hundreds to thousands of individual animals called zooids in the space of only one square inch!

 

A fossilized tabulate coral (left) and a fossilized rugose "horn coral," (right) from Camp Nelson. Both types of coral went extinct at the end of the Permian period around 252 million years ago.

NPS/ Emily Jackson

Corals of the Ordovician looked pretty different from those we have today, in fact the two types identified from within the national monument have no living modern relatives. Corals are filter feeding organisms that during the Ordovician belonged to two main groups, solitary rugose (horn corals) or colonial tabulate corals. Horn corals get their name as they have shapes similar to a cow’s horn, while tabulates are called that due to the tabulae (flat walls) that separate individual corallites into box-like chambers.

 

Left image
Modern crinoid
Credit: NOAA

Right image
Fossilized crinoid column at Camp Nelson
Credit: NPS/ Emily Jackson

Crinoids, also known as sea lilies, are filter feeding organisms that, much like their name suggests, look much like flowers. These animals have long stalks that connect to several feather-like appendages giving the appearance of a stem and petals. During the Ordovician these animals were commonly found in both deep and shallow water and that holds true today, however sea lilies (crinoids that look most like they did in the past) live mainly in the deep ocean today.

Crinoids often separate into many pieces when they die, leaving behind lots of little ring-shaped fossils called “columnals” that used to be stacked, making up their “stems”.

 

Left image
Modern gastropod
Credit: NPS/ Crystal Lewis

Right image
Fossilized gastropods at Camp Nelson
Credit: NPS/ Emily Jackson

Gastropods, commonly known as snails, were some of the most common animals in this area during the Late Ordovician. These animals served a couple different functions in their environments, some eating algae or detritus (fine particles of organic matter), and others preying on brachiopods, bivalves, and even other snails.

 

Left image
Modern Chambered Nautilus
Credit: Monterey Bay Aquarium

Right image
Fossilized Nautiloid at Camp Nelson
Credit: NPS/ Emily Jackson

Nautiloids, or “shelled squids”, were some of the apex predators of this area 435 million years ago. These animals had many different shell shapes, though the most common one found within the national monument is the straight tapered cone (orthocone). Nautiloids could reach extreme sizes during the Ordovician, with the largest being Cameroceras which is believed to have reached lengths of 25 to 35 feet, that’s as long as a school bus!

 

Left image
Modern ostracods
Credit: Flickr/ Mr.Sansibar

Right image
Possible fossilized ostracods at Camp Nelson
Credit: NPS/ Emily Jackson

Ostracods, little two-shelled crustaceans, were detritus eaters that cruised along the seafloor during the Ordovician. While small compared to many of the other animals around at the time, ostracods were the largest they had ever been, about the size and shape of a bean.

Many other animals have been recorded from the same rocks that are in Camp Nelson National Monument though outside of the national monument’s boundaries. Algae, conodonts (jawless fish), sponges, trilobites (marine bug-like animals), and sea urchins are among the many other animals that were all present in this area during the Late Ordovician, painting the picture of a shallow sea teeming with life, much like our reefs look today!