Specimen of the Month
November 2012
Fairburn Agate
South Dakota State Gemstone
Fairburn Agates, named for their proximity to Fairburn, SD, are highly sought after fortification agates. They are most ientified by their colorful and sharp holly leaf banding. These fortification agates come in a variety of mixed colors such as red, blue, purple, brown, white, black, yellow, pink and orange. The layers are concentric and usually parallel to the walls of the rock cavity in which they are deposited. The composition of the Fairburn Agate is usually 98% Silica (SiO2), a combination of silica and oxygen. The balance being trace minerals which help provide the color.
The Journey of the Fairburn Agate began 300 million years ago in a shallow sea that one covered western South Dakota. Fairburns were formed in the Minnelusa Limestone layers at the bottom of a shallow sea where silica began to accumulate in the soft sediments. These agates lay buried until the Black Hills uplift 60-70 million years ago. When exposed to the surface these agates tumbled along in streams being rounded, chipped and shaped. Once these agates made their journey into what is now the eastern slope of the Black Hills they were once again buried in the Chadron Formation for another 30 million years. As erosion began to carve out the Badlands terrain, the Fairburns began to surface once again.
October 2012
Dunkleosteus (Skull)
SDSM C-85
Cleveland, Ohio
Devonian (365 Million years ago)
Dunkleosteus was a gigantic fish which lived in the latter part of the Devonian ("Age of Fishes"). This predator could grow up to 33 feet long and weigh 4 tons. It belonged to the Arthodira or "joint-necked" fish, so-called because the plates of bone which sheathe the head were connected by a hinged joint with the boney armor of the chest (thorax). Bot all arthodires were as large as this kind: some were only a few inches in total body length.
This specimen is a cast based on actual bones found in the marine Cleveland Shale of the late Devonian (365 million years ago). The original skull is on display at the Cleveland Museum of Natural History. Nearly half of North America was submerged by shallow salt water at one time or another in the later Devonian.
September 2012
Malachite
Bisbee, AZ #412
Malachite is a copper carbonate hydroxide mineral, with the formula Cu2CO3(OH)2. Malachite often results from hydrothermal alteration and is often found together with azurite, goethite, and calcite. Except for its vibrant green color, the properties of malachite are similar to those of azurite and aggregates of the two minerals occur frequently. Malachite is more common than azurite and is typically associated with copper deposits around limestones, the source of the carbonate. Large quantities of malachite have been mined in the Urals, Russia. It is found worldwide including Democratic Republic of Congo; Gabon; Zambia; Tsumeb, Namibia; Mexico; Broken Hill, New South Wales; Lyon, France; Timna Valley, Israel; and in the Southwestern United States notably in Arizona. Malachite mineral is used in ammunition, electrical circuits, electronic equipment, appliances, automobiles, coins, etc. The ore is also used to build copper pipes. Malachite was also used as a mineral pigment in green paints from antiquity until about 1800. It is commonly used for decorative purposes, such as in the Malachite Room in Hermitage, which features a huge malachite vase.
August 2012
Edmontosaurus saskatchewanensis
Hell Creek Formation near Watauga, SD
~ 70 million years old
SDSM 4917
Edmontosaurus lived in large herds and roamed along the coast of an ancient seaway that stretched from Texas to Canada between 80 and 65 million years ago. It is a member of the Ornithischians or "bird-hipped dinosaurs" due to the resemblance of their hips to those of modern birds. Like all Ornithischians, Edmontosaurus at only plants. They ground up their food with their thousands of teeth that were constantly being replaced as they wore out. Edmontosaurus is also called a "duck-billed dinosaur" because it would have had a sharp "bill" on the end of its mouth used for cutting vegetation. Duck-billed dinosaur nest sites found in Montana suggest edmontosaurs were good parents, building nests and caring for their young. This specimen is a composite mount; which means it contains both real fossils and reproduction casts of real fossils. Many restorations of fossil animals are done this way because it is very rare for paleontologists to find the whole animal. This mount is an example of the posture scientists once thought Edmontosaurus would have had. It is now known that they walked on all four limbs with their tail stretched out behind them.
July 2012
Stone American Flag
Blue: Azurite; White: White Quartz; Red: Rose Quartz; Stars: White Quartz
Weighs 400 lbs.
The 48 Star Flag: On July 4, 1912, the U.S. Flag grew to 48 stars with the addition of New Mexico (January 6th 1912) and Arizona (February 14, 1912). Executive Order of President Taft dated June 24, 1912 - established the proportions of the flag and provided for arrangement of the stars in six horizontal rows of eight each, a single point of each star to be upward. This flag was official for 47 years, though two World Wars and the emergence of the United States of America as the leading nation of the world. Eight Presidents served under this flag; William H. Taft (1909-1913), Woodrow Wilson (1913-1921), Warren Harding (1921-1923), Calvin Coolidge (1923-1929), Herbert Hoover (1929-1933), Franklin D. Roosevelt (1933-1945), Harry S. Truman (1945-1953), Dwight D. Eisenhower (1953-1961).
June 2012
Carcharocles megalodon
Approximately 5" Long
Found near York town, VA
~17 Million Years Old
SDSM 54348
Carcharocles megalodon is regarded as the largest shark ever to have lived (~28 to 1.5 million years ago) at an estimated 15 to 20 meters (52 to 67 feet) in length. After decades of research on this massive shark, controversy over the evolutionary relationships still persist. Some researchers insist C. megalodon is a close relative of the Great White Shark (Carcharodon carcharias), others insist it belongs in a different family, Otodontidae, as Carcharocles megalodon and cite convergent evolution as the reason for the dental similarity. Many researchers are now placing this mega-shark in the later group.
May 2012
Bison crassicornis
"Superbison" aka Kent
Fairbanks, Alaska
SDSM 5121
Kent was found in Fairbanks, Alaska on April 17, 1951 and came to our museum from the Frick Lab at the American Museum of Natural History in New York City. The average Superbison had a horn span between 30.1 inches (765mm) and 52.0 inches (1322mm). Kent's horn span is 43.3 inches (1100mm), making him average-sized. Kent still has his horn sheaths covering his horn cores. If you look closely at Kent's upper jaw on his right side, you will notice some abnormal bone growth that occurred while he was living. This pathology (a deviation from a healthy condition) is at a muscle attachment site and may have been caused by an abscess. The Superbison lived approximately 600,000 to 30,000 years ago during the Medial to Late Pleistocene Epoch. These bison migrated from Siberia to Alaska during the second wave of bison migration across the Beringia Land Bridge. They remained in what is now Canada for their entire existence. At this time, the land was going through a continuous cycle of glacial advancement and retreat.
April 2012
Paleolagus
~32 Million years ago
Brule Formation, Wyoming
This specimen is the skeleton of a fossilized rabbit. This genus is one of the most common fossils found in the Brule Formation. The specimens usually only consist of teeth, and this specimen is stunning for its beautiful and almost complete skeleton. Gift of the Boyce Family.
March 2012
Triceratops horridus
South Dakota’s State Fossil
Hell Creek Formation, Harding County, South Dakota SDSM 2760
The Ceratopsia or horned dinosaurs were one of the last major groups of dinosaurs to make their appearance on Earth. They were common in the Late Cretaceous (approximately 70 million years ago) of western North America, and Triceratops horridus was perhaps the most common species. Triceratops (three-horned face) was remarkable for its huge head, exceeding that of any other known land animal. This dinosaur lived on vegetation and may have used its horns for defense, probably against such formidable predators as Tyrannosaurus rex. Triceratops grew to 25 feet in length and weighed up to 8 tons.
February 2012
Fossil Ganoid Fish
Early Cretaceous (~144 million years ago), Lakota Sandstone, South Dakota
The fish seen in this slab have very specialized scales. These are ganoid scales, which have three structural layers. The top layer is ganoin, an enamel-like substance; the next later is dentin, the same material that is under tooth enamel. The bottom layer of the scale is bony material. These scales are found on prehistoric fish and also on some modern fish, including gar and sturgeon. This indicates that these fossil fish are closely related to those modern fish.
January 2012
L to R: Quercus traini, Canyon Live Oak, #109; Quercus simplex, Asiatic Oak, #112; Quercus consimilis, Asiatic Oak, #117.
Miocene Epoch (23.0-5.0 million years ago) – Oregon
In Finland, January is referred to as the "oak month." These leaves on display in the Museum of Geology were found in Miocene strata of Oregon, likely preserved between 5 and 15 million years ago. These oaks were restricted in their environment, living almost exclusively in present-day Oregon and California. Although these particular species are extinct, their closest descendents continue to inhabit forests in the United States and around the world. Using information about the ecosystem in which their descendents live, scientists can infer with some certainty the environment in the time and place in which these fossil plants lived.
December 2011
Pentacrinus asteristicus
Jurassic Period
Sundance Formation, South Daokta
Crinoids, commonly known as sea lilies, are echinoderms. Echinoderms include sea stars (starfish) and sea urchins, and most possess five-fold symmetry. Crinoids consist of a series of tentacles surrounding mouth parts, elevated above the sea floor by a rooted stalk. This specimen of Pentacrinus is a collection of cross-sectional pieces (called columnals) of the crinoid's stalk. The five-fold symmetry of echinoderms is obvious in the columnals of Pentacrinus, which look like a five-pointed star. Crinoids are very abundant in the Mississippian Period (359-318 million years ago). Many Mississippian limestones, abundant in the U.S. midcontinent, are composed mostly of crinoid skeletal pieces. Crinoids are the state fossil of Missouri.
November 2011
Hesperornis regalis
~Campanian Age – Cretaceous period – 70.6 to 83.5 million years ago
Sharon Springs Formation of the Pierre Shale Group – Harding County, SD.
Hesperornis was a sea-going bird whose behavior would not be unlike that of a penguin, as it possessed small wings, and would be incapable of flying. Despite being a swimming bird, it probably did not have webbed feet. It was an early occurring bird, and as such, still possessed teeth. There is also evidence that Hesperornis would have been a target of predation for mosasaurs.
