SEASHELLS USED AS MONEY

The Money Clam

“Wapum,” a name derived from eastern North American indigenous people, was used for certain seashells used as money. As mentioned by Rohler (1971), for thousands of years, from Virginia to Canada, indigenous people in that region put small carved discs and tubes (with added central holes) of the commonly occurring Northern Quahog bivalve (clam) into strings of beads.  This clam (a.k.a. the "money clam," which is found along the New England coast, has one of the hardest shells of any mollusk. These necklaces served as their money. The scientific name of this bivalve is Mercenaria mercenaria (Linné, 1758), and it belongs to family Veneridae. This bivalve lives in lagoons.

 

 

Top row: exterior views of the left and right valves of a specimen of the bivalve Mercenaria mercenaria (Linné, 1758); 60 mm (2.5 in.) wide, 50 mm (2 in.) high. Bottom row: interior views of the left and right valves of the same specimen. 

 A very similar looking bivalve is the Southern Quahog, Mercenaria campechiensis (Gmelin, 1791), which is common in inshore waters from Georgia, Florida, and northwestern Cuba. Additionally, a third very similar looking bivalve is Mercenaria mercenaria texana (Dall, 1902), which occurs commonly in shallow lagoons in the northern Gulf of Mexico. It seems very likely to me that these two additional bivalves could also have been used as “wampum.”

TWO EXAMPLES OF MONEY GASTROPODS (SNAILS)

1) Another shell used as wampum was the “channeled whelk” shell, Busycotypus canaliculatus (Linné, 1758), formerly known as Busycon canaliculatum (Linné, 1758). This large snail shell is made by the predatory neogastropod that belongs to family Buccinidae. Busycotypus canaliculatus lives along the New England coast, from Cape Cod, Massachusetts southward to Cocoa Beach, Brevard County, southeastern Florida. 

Ventral and dorsal views of Busycotypus canaliculatus (length 19 cm, width 11.5 cm). Based on pl. 14, figs. 3, 4 of Hollister (1958).

2) The so-called "money cowrie" shell is the gastropod Monetaria moneta (Linné, 1758), which secretes small (commonly 1 inch in length) shells, pale yellow in color). They are widespread in rocky intertidal depths in tropical waters of the Indo-Pacific area and can be associated with coral-reefs flats. They are also found in the eastern Pacific Ocean (Galapagos Islands and Cocos Island off Central America).

Three views (base = apertural, dorsal, and right lateral) of the "money cowrie" Monetaria moneta, Indo-Pacific area, exact locality unknown, length 28 mm, width 20 mm, height 12 mm. The morphology of this species is quite variable (see figure below).

A small population (length 14 to 30 mm, width 10 to 21 mm) of Monetaria moneta showing considerable variation in color and shape. 

The "money cowrie" was much more popular than the other “money shells” mentioned above because it is so widespread geographically. The use of "money-cowrie" shells dates back to antiquity (7^th century AD) in India. They were also used in China in the 1300’s. When the Europeans reached these areas, the "money cowrie" became widely used. The Europeans also collected modern-day species of cowries from Africa and brought them to the Far East, where they used them for money, as well. As with other money shells, the money cowrie shells were also used for ornamental purposes.

 

The Money Scaphopod 

Scaphopods (commonly known as “tusk shells”) are lenticular/hollow tubes secreted by mollusks belonging to an entirely different group of mollusks than either bivalves or gastropods. Scaphopods are found in shallow to moderately waters offshore where they partially burrow into soft sediment. Indigenous people of the Pacific Coast of North America used these shells as shell money, which was referred to as “haik-wa” or “hai-qua.” These shells were raked from the ocean floor. After being cleaned, the shells would be strung together into necklaces. Eventually, these kinds of shells were used by various tribes of the American West for ornamental purposes. In Alaska today, scaphopods are still used for ornamental purposes by remote tribes.

On the left: the "green" scaphopod: Dentalium elephantinum 11.5 cm long, 11 mm maximum diameter. On the right: a different species of Dentalium 12 cm long, 11.5 mm maximum diameter. Localities of both species unknown.

Side views of the same two specimens shown immediately above.

References Cited:

Hollister, S.C. 1958. Review of the genus Busycon and its allies. Part 1. Palaeontographica Americana v. 4, pp. 59~126. 

Rohler, C. 1971. Shell Money. Of Sea and Shore, v. 2, no. 1, pp. 27–30. 

[This journal is no longer being published by the editor Tom Rice (1939–2022), but the complete set is now online as a searchable archive containing all issues (1970–2004) and free downloadable pdfs. Go to: www.conchology.be

 

UNCONFORMITIES

An unconformity is a surface between a group of sedimentary beds (layers, strata) and the underlying rocks; it is an ancient land surface that represents an interval of time during which erosion occurred rather than deposition. In geologic cross-sections, unconformities are represented traditionally by a wavy line or a jagged line.

There are three kinds of unconformities: 1) disconformity, 2) angular unconformity, and 3) nonconformity.

In the sketched diagrams below, the different rock layers are in various colors or symbols. 

1) DISCONFORMITY: 

A disconformity forms when erosion removes certain layer(s) of sediment, and all the remaining layers are horizontal. The disconformity is depicted by a wavy line.

2) ANGULAR UNCONFORMITY:

An angular unconformity forms when a group of rocks have been tilted and removed (eroded) to some degree, and younger rocks have been deposited on top of them; (the eroded surface is an angular unconformity). In the box diagram below, the angular unconformity is depicted by a wavy line. 

3) NONCONFORMITY:

A nonconformity forms when an erosion event occurs on crystalline rocks (i.e., igneous and/or metamorphic rocks), and the overlying layers of sedimentary rock are horizontal (note: they can later be tilted). In the box diagram below, the nonconformity is represented by the jagged line below the colored layers of sedimentary rock; and the igneous and/or metamorphic rocks are depicted by the short, straight dashes.

Examples in the Grand Canyon of the Three Types of Unconformities: 

The Grand Canyon in northern Arizona has classic examples of all three types of unconformities, as depicted in my geologic cross section shown below. My commentary on the associated geologic history events accompanies this cross section.

Much of the information in this figure is derived from a geologic cross section published in 1971 by the Zion Natural History Association. Additional detail is derived from Wikipedia (2022).

The following two photographs were taken by the author in the late 1960s. 

 

A widespread angular unconformity occurs between tilted Precambrian sedimentary beds (in the foreground of the photo) and the overlying non-tilted younger Cambrian strata (in the middle of the photo). The view is toward the north side of the Grand Canyon. This  angular unconformity in the Grand Canyon is also generally known as “Powell’s Great Unconformity,” in reference to John Wesley Powell, an American geologist who explored the Colorado River and its canyons via two raft trips (1869 and 1871). John Newberry was the first to detect a similar erosion surface in Precambrian rocks in New Mexico during the Ives Expedition of 1857-1858, but disruption by the American Civil War kept Newberry’s work from becoming widely known.

This photo shows another type of unconformity in the Grand Canyon  and is actually the oldest unconformity (Precambrian in age) found there. It is a nonconformity that is only exposed locally by down-cutting of the Colorado River, in one of the deepest parts of the Grand Canyon, between the black underlying metamorphic Vishnu Schist,  so-called "basement rock," and the overlying brown sedimentary layers.

References:

Stanley, S.M. 1999. Earth System History, W.H. Freeman & Co., New York, pp. 10-11.

Wikipedia (website). 2022. The Great Unconformity. 

Zion Natural History Association, 1971. Geologic cross section of the Cedar Breaks-Zion-Grand Canyon region, Zion Natural History Association, Zion Natural Park, Springdale, Utah. 

SUMMARY OF THE MAMMAL GROUPS IN MY RECENT POSTS

 Over the past several months, I have reviewed the morphology (including dental characteristics) and geologic history of many of the major groups of fossil mammals. I did this because I know that many undergraduate geology students these days are seldom taught about the interesting up-to-date details concerning these very interesting groups. I hope that you found the information informative and useful.

In order to summarize where and when these fossil mammals originated, I plotted  the world-view summary shown below.  

To get an overview of the migratory routes used during the Cenozoic, it would be helpful if you examined at the first two posts again concerning overviews of Beringa 1, 2, and 3, as well as the GABI Event). These were routes available at different times for each of these mammal groups.

PAKICETUS: THE EARLIEST PRECURSOR OF WHALES

The fossil Pakicetus is of late early Eocene age from Pakistan. This mammal was 3 to 6 feet long (wolf size). It has a particular ankle bone that links it to articodactyls (a diverse group of even-toed hoofed mammals, including pigs, sheep, cows, deer, giraffes, antelopes, and hippos). Pakicetus had a squat, wolf-size body, with hoofed feet capable of running. Pakicetus also has, however, an ear bone with a feature unique to whales (cetaceans). Additionally it has a long skull with long jaws that resemble that found in whales. Like other artiodactyls its teeth consisted of insisors, canines, premolars (although rather widely spaced and very triangular), and molars. Some specialists claim that Pakicetus was semi-aquatic, but others claim that it lived entirely on land. 

Pakicetus (wolf size).

Body view (approximately 6 feet long) and head shot of the same specimen of Pakicetus attocki Gingerich and Russel, 1981, late early Eocene, Pakistan. Natural History Museum of Los Angeles County, Southern California, Age of Mammals Hall.

Since 1981, skeletons similar to, but different from, Pakicetus have been found in early and middle Eocene deposits in Pakistan, India, Egypt, and the southeastern United States. These skeletons have allowed paleontologists and evolutionary biologists to recognize new genera that collectively show a gradual evolutionary transition of Pakicetus-like animals becoming, over time, more like whales (e.g., a few even had their back legs become flippers used for swimming). All these genera, along with Pakicetus, are commonly referred to as archaeocetes [=close ancestors to whales], with Pakicetus the earliest one. In Egypt, by the late Eocene, at least one archaeocete, a Basilosaurus, had a very long, whale-like body (25 m long!). 

HIPPOPOTAMUSES

Hippos are artiodactyl ungulates that belong to family Hippopotamidae. There are two living genera/species:

1) Hippopotamus amphibious, which is amphibious and can swim and dive well. This species lives in herds of 5 to 30 individuals near ponds and rivers. This hippo can weigh up 4.5 tons, has stubby legs each with four toes, thick leathery skin that is hairless, and can very widely open its mouth. It has wide horny lips. This hippo lives in Africa south of the Sahara Desert. This species can remain just below the water surface because its nostrils are located on the top front of the skull. The nostrils open dorsally, thus the animal does not have to be much above the surface of the water in order to breathe. Hippos are slightly denser than water, thus allowing them to walk on the river bed.

Hippopotamus amphibious (two views) at Los Angeles, California County Zoo:

2) The other living genus/species of hippopotamus is Choeropsis liberiensis [=the pygmy hippo], which is less aquatic than H. amphibious and occurs singly or in pairs in moist forests of West Africa.

As shown in the figure below, the dental formula for hippopotamuses is typically 1/1, 1/1, 4/3, 3/3 = 36 teeth, but the number of premolars can be as many as 4, on both the upper and lower jaws. Hippos graze on grasses growing in and around lakes.

Oblique side view of a hippo skull with most of its teeth visible. 

A hippo’s incisors and canines grow continuously, but the cheek teeth do not. The lower pair of incisors are longer than the upper pair of incisors. Both the incisors and canines are large. Even though hippos are herbivores (plant eaters), their canines are tusk-like and can be very large (up to 1.5 feet long). They are also continuously sharpened. The canines are used for fighting other hippos. The cheek teeth are flat-ridged, like in most other land mammals. Hippo teeth contain enamel and is referred to as being ivory. Their ivory is harder than elephant-teeth ivory, but hippo-ivory is not as white. American colonists in the 1700s, used hippo ivory rather than elephant ivory for making false teeth. 

 

The fossil record of hippos is poor. Based on fragments of teeth found in Kenya, Africa, hippos probably originated during middle Miocene time in Africa. Their ancestors were most likely Miocene peccaries or the extinct anthractotheres (large pig-like mammals). Hippos are not ruminants but have two accessory stomach sacs (like peccaries). Their digestion is very slow and very efficient, therefore they do have to be grazing all day long. During the Pleistocene, there were hippos that had eye sockets elevated on stalks (allowing the animal to have periscopic eyes, which allowed the whole body to remain submerged (while the eyes were above water.)

References Used:

en.Wikipedia.org

Lawlor, T.E. 1979. Handbook to the orders and families of living mammals. Mad River Inc. Press. 327 pp. 

Savage, R.J. and M.R. Long, 1986. Mammal evolution an illustrated guide. British Museum of Natural History. 259 pp.