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The West Indian Locust (Hymenaea courbaril)
Modern-Day Relative Of New World Amber
This Noteworthy Plant Is Dedicated to Robert Ebert, A Very Special Friend,
Biologist Extraordinaire & Palomar College Life Sciences Colleague With
Whom I Spent Many Wonderful Day During Our Palomar Careers. [W.P.A.]

© W.P. Armstrong 31 March 2010

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     Large West Indian Locust On The Island Of St. John
     West Indian Locust Pods, Leaves & Seed Necklace
     Guapinol Seeds & West Indian Locust Seed Necklace  
     Large Seed Pod & Guapinol Seeds Of West Indian Locust  
     Chunks Of Copal Resin Carried By Ocean Currents  
     Dispersal Of West Indian Locust Seeds By Big Animals  

The generic name Hymenaea is derived from Hymen, the Greek God of marriage, referring to the beautiful green leaflets that always occur in matching pairs. In the evening during the spring flowering season, large, white blossoms appear high in the canopy branches. The large anthers put pollen on the chest and head fur of nectiferous bats that are attracted to the sweet blossoms. The trunk and roots of West Indian locust exude a sticky, yellowish terpene resin that forms hardened globs which become buried in the soil around massive trunks of dead trees. The raw resin is known as Central American copal, and it is used for varnish and as incense. Central and South American copal is also produced by the related genus Copaifera, which includes the highly aromatic balsam-producing trees C. reticulata and C. officinalis. [Another source of balsam resin is the Central American leguminous tree Prioria copaifera. The large, flattened, one-seeded pods of the latter species are commonly washed ashore along Caribbean beaches of Costa Rica.] The hardened subterranean resin known as East African copal, which is commonly used in bead jewelry, comes from Hymenaea verrucosum, a tree that is closely related to the West Indian locust. It was formerly classified in the genus Trachylobium. In Chiapas, Mexico, Dominican Republic, and parts of Colombia and Brazil, the subterranean resin globs of ancient Hymenaea trees have transformed into amber through a remarkable chemical process requiring millions of years. During the polymerization process the volatile mono and sesquiterpenes escape and the nonvolatile diterpenes bond together forming a hard plasticlike polymer that is resistant to natural decay processes and the ravages of time. Unlike copal resins, the amber is unaltered by organic solvents such as alcohol, acetone and ether. Although copals will take a high polish, they contain volatile terpenes that gradually evaporate, causing the surface to become deeply crazed like a dry lake bed. Dr. Jean Langenheim of the University of California at Santa Cruz, the noted authority on plant resins (Science Vol. 163, 1969), has studied amber samples from throughout the world using infrared spectroscopy (IR). When printed by a plotter, the IR's appear like a series of closely-spaced peaks and valleys, with each species of tree having its own characteristic "fingerprint" pattern. Samples of amber from Mexico, Dominican Republic, Colombia and Brazil have IR spectra remarkably similar to raw resin from present-day West Indian locust.

Large West Indian locust (Hymenaea courbaril) along the lush Reef Bay Trail on the Island of St. John, U.S. Virgin Islands.

These chunks of Dominican Republic amber are embedded in Miocene sandstone about 25 million years old. They originated from subterranean deposits of hardened resin from an ancestral species of Hymenaea, similar to present-day copal from West Indian locust. During countless thousands of years, the resin polymerized into amber.

The widespread distribution of West Indian locust throughout the Caribbean and the American tropics is probably due to the buoyant seed pods. The large, woody pods do not open and often get washed down rivers into the ocean where they drift ashore on distant beaches. Several plausible hypotheses have been proposed to explain the occurrence of two remarkably similar species of copal-bearing Hymenaea on the isolated continents of Africa and South America, including continental drift and dispersal of seed pods by ocean currents. Evidence from plate tectonics shows that large plates of the earth's crust are slowly moving. It has been estimated that during the Cretaceous and Jurassic Periods, South America and Africa were once connected in a great supercontinent called Gondwanaland. Although the time frame for Gondwanaland is probably too early for Hymenaea, there may have been an ancestral forest throughout this vast land mass that gave rise to today's isolated copal species. A more plausible explanation involves the ocean dispersal of woody Hymenea seed pods from Africa. Adding credibility to the idea of pods floating across the Atlantic Ocean from Africa via the Equatorial and Brazil Currents are the large brown seeds inside which may remain viable even after many months at sea. The hard seeds are sometimes polished and strung into necklaces by Caribbean islanders. In Costa Rica the seeds are known as "guapinol" and are made into polished hardwood pendants. The dark brown coat is sanded off on one side and the smooth ivorylike inner surface is painted with a colorful country scene.

Branch of the West Indian locust (Hymenaea courbaril) showing paired leaflets and large woody pods. One pod is cut lengthwise revealing four white seeds. The pods are dispersed by ocean currents throughout islands of the Caribbean, and the large, brown seeds are strung into attractive necklaces. Globs of yellowish resin exuded from the trunk of large trees is the source of copal varnish and incense, and the polymerized resin from an ancestral species (H. protera) is the source of Dominican Republic amber and lovely earrings.

The large "guapinol" seeds of West Indian locust (Hymenaea courbaril) are sanded and beautifully painted by artists. They are also strung into attractive hardwood necklaces.

The large fruit and "guapinol" seeds of West Indian locust (Hymenaea courbaril). The amber comes from an extinct species of Hymenaea that lived more than 30 million years ago.

A blob of sticky resin oozing from the trunk of a West Indian Locust (Hymenaea courbaril). After many decades, masses of the honey-colored resin often pool into the soil beneath large trees.

A chunk of hardened copal resin about five inches (12.7 cm) long.

Copal Resin Carried By Ocean Currents

Deposits (pools) of hardened resin called copal commonly collect in the soil beneath large, old trees of West Indian locust (Hymemaea courbaril). Chunks of copal in coastal forests of the Caribeean and Central America could easily get washed into the ocean during torrential rains of the hurricane season. In fact, the buoyant seed pods are often washed ashore on beaches of Caribbean Islands, the Gulf of Mexico and Florida. It is not surprising that chunks of Hymenaea copal could be carried by ocean currents to distant beaches. Massive deposits of Old World amber occur in the Baltic Sea region and pieces of amber commonly wash ashore along beaches.

The following image shows a huge 30 pound (14 kg) chunk of copal that was washed ashore on a Florida beach. Because of its size, the West Indian locust is the likely candidate for the source of this remarkable discovery.

A massive chunk of copal washed ashore on a Florida beach. Photo courtesy of B. Neyrinck (2010).

Dispersal Of West Indian Locust By Gomphotheres: New World Anachronisms

With the exception of introduced cattle, donkeys and horses, no native mammals of the New World tropics can crush the hard, thick-walled pods of many rain forest trees in their jaws. Livestock apparently like the sweet pulp inside the pods of West Indian locust (Hymenaea courbaril) and disperse the hard, viable seeds in their excrement. In areas without livestock, the rotting pods litter the ground beneath large trees. Agoutis, tapirs and peccaries chew open the rotting pods and eat the sweet pulp and seeds, but are not major agents of seed dispersal like the larger hoofed mammals. According to the authority on Central American rain forests, Daniel H. Janzen (Science Vol. 215, 1982), large grazing mammals, including extinct pleistocene elephants called gomphotheres, may have once eaten the pods and dispersed the seeds in lowland forests. In Africa, the large woody pods of related species are quickly devoured by large herbivores. There are other Central American rain forest trees that also appear to be missing their natural herbivorous dispersal agents. Their hard, woody, indehiscent fruits pile up beneath the branches and slowly rot away in the soggy, moldy layer of soil and debris.

Hard, woody fruits of some Central and South American rain forest trees were likely dispersed by large prehistoric herbivores thousands of years ago. A. Cassia grandis (Fabaceae); B. Crescentia alata (Bignoniaceae); C. Hymenaea courbaril (Fabaceae); and the palms (Arecaceae): D. Attalea speciosa (one fruit cut open to reveal thick, woody pericarp); E. Raphia taedigera; and F. Orbignya cohune. The hard, woody fruit wall of Attalea speciosa (D) was one fouth of an inch thick (6 mm). I used a fine tooth saw to cut the fruit in half.

References About The Genus Hymenaea & New World Amber

  1. Allen, J.D. 1976. "Amber and Its Substitutes--Pt. I Hisorical Aspects." The Bead Journal Winter 1976: 15-20.

  2. Allen, J.D. 1976. "Amber and Its Substitutes--Pt. II Mineral Analyses." The Bead Journal Spring 1976: 11-21.

  3. Allen, J.D. 1976. "Amber and Its Substitutes--Pt. III Is It Real? Testing Amber." The Bead Journal Summer 1976: 20-31.

  4. Cano, R.J. and G.O. Poinar, Jr. 1993. DNA From An Extinct Plant. Nature 363: 677.

  5. DeSalle, R., J. Gatesy, W. Wheeler and D. Grimaldi. 1993. DNA Sequences From a Fossil Termite in Oligo-Miocene Amber and Their Phylogenetic Implications. Science 257: 1933-1936.

  6. Grimaldi, D.A. 1996. Captured in Amber. Scientific American 274 (4): 84-91.

  7. Grimaldi, D.A. 1996. Amber: Window To The Past. American Museum of Natural History. H.N. Abrams, Inc., New York.

  8. Grimaldi, D.A. 1993. Forever in Amber. Natural History 6/93: 59-61.

  9. Janzen, D.H. 1983. Costa Rican Natural History. The University of Chicago Press, Chicago.

  10. Janzen, D.H., and P.S. Martin. 1982. "Neotropical Anachronisms: The Fruits the Gomphotheres Ate." Science 215: 19-27.

  11. Langenheim, J.H. 2003. Plant Resins (Chemistry, Evolution, Ecology & Ethnobotany). Timber Press, Portland Oregon.

  12. Langenheim, J.H. 1973. "Leguminous Resin-producing trees in Africa and South America." In Tropical Forest Ecosystems in Africa and South America: A Comparative Review, ed. B.J. Meggers, E.S.Ayensu, and W.D. Duckworth. Smithsonian Institution Press, Washington, D.C.

  13. Langenheim, J.H. 1969. Amber: A Botanical Inquiry. Science 163: 1157-1169.

  14. Poinar, G.O., Jr. and R. Poinar. 1994. The Quest For Life in Amber. Addison-Wesley Publishing Co., Reading, Mass.

  15. Poinar, G.O., Jr. 1992. Life in Amber. Stanford University Press, California.

  16. Poinar, G.O., Jr. and R. Hess. 1982. "Ultrastructure of 40-Milion-Year-Old Insect Tissue." Science 215: 1241-1242.

  17. Rice, P.C. 1987. Amber: The Golden Gem of the Ages. The Kosciuszko Foundation, Inc., New York.

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