Under Ultraviolet Light, Chalky White Fossil Seashells from Florida Reveal
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Under ultraviolet light, chalky white fossil ago in a world as yet without fish, amphi- commonly beautiful color patterns, when seashells from Florida reveal fluorescent bians, reptiles, birds, mammals, or land seen in the proper kind of light. colors that are remains of former color pat- plants. These little fossil seashells are That kind of light is ultraviolet light. It terns. without traces of any colors but exception- seems unnecessary to go here into the Nowhere is beauty more parsimonious ally rare specimens of a similar kind and physics of this phenomenon, and so I sim- with its kisses than in the fossil record. antiquity found elsewhere in the world have ply point out that this is the same kind of Once glorious seashells that might have dull patterns that prove seashells had col- light called "black" light used for advertis- made colorful showpieces for a collector's ors even this long ago. ing, parties, and elsewhere to make cabinet generally become uniformly pallid Major museums — among which ours is fluorescent objects glow. "Black" lights and and aesthetically drear, although not with- included — maintain large collections of strobe lights were necessary components out appeal as curiosities, within a few tens such fossil seashells and the myriad other of the light shows that until recently accom- of thousands of years or so after death and kinds of invertebrates for current and future panied rock concerts. burial. Fossil seashells usually excite only research and as voucher specimens from These fossil seashells are found in de- paleontologists who see them as clues in past studies. Some specimens are used posits at several places in southern Florida. their quest for the origin of life and of its for displays, museum classes, and popular The ones figured here came from spoil subsequent three and half billion year his- articles like this one. banks bordering a canal in Okeechobee tory on Earth. Studies of the color pigments in living County and are ten to fifteen million years For example, the most famous fossil seashells reveal that they are complex or- old, or somewhat younger than the Old To- seashells in Los Angeles County are found ganic substances built into the limey shell panga Canyon Road specimens, but much in the loose sand of raised beaches on the by the living animal. Melanins and tetrapyr- older than the ones from the Palos Verdes Palos Verdes Peninsula. These seashells roles are reportedly two common pigments. Peninsula raised beaches, which they are about a hundred thousand years old The former are said to be relatively insolu- nevertheless resemble in preservation. In and are chiefly chalky white, although a few ble, but the latter are soluble in many ordinary light, they are seen to be well- show pale color traces. Twelve hundred liquids. We have observed above that the preserved and mostly chalky white, al- Museum Alliance members may recall their color pigments in seashells are unstable though a few show very pale brown color 1969 Dimensions to Delight "dig" for these over long periods of time. It seems likely patterns. fossils. that the waters percolating through the sed- Their "secret" character is not pos- Another famous fossil seashell locality in iments burying the dead seashells dissolve sessed by the Los Angeles County fossils Los Angeles County is near the crest of the and disperse some of the color pigments. or, to the same degree as far as I know, by Santa Monica Mountains along Old To- Perhaps other agents as well are responsi- other fossil seashells from elsewhere. We panga Canyon Road. It is about twenty mil- ble for their disappearance. have tested all the ones in our museum lion years older than the Palos Verdes Until recently, only the rarest specimens collections, which is worldwide in scope, Peninsula one and has changed from once of fossil seashells were known to have even although obviously incomplete. What loose sand into hard sandstone enclosing traces of original color patterns, except for causes this geographic restriction is un- entirely drab fossil seashells. those from the very youngest fossil de- known at present. In the Marble Mountains of nearby San posits such as the Palos Verdes Peninsula When exposed to the short wave kind of Bernardino County, some of the oldest raised beaches. This article is about ultraviolet light in darkness, some of the known fossil seashells may be seen. They specimens very much older recently dis- fossil Florida seashells fluoresce brilliantly lived and died more than half a billion years covered to have beautifully common and with symmetrical orange patterns against a glowing violet background. These are the the most beautifully patterned. We also Orleans. Thomas Warren of Ultra-Violet original patterns occupied by the colors of have observed that the main one or two Products, Inc. in San Gabriel kindly loaned the shells while alive, although the colors muscle scars inside clams and an as- a short wave ultraviolet lamp and other themselves are no longer present. Since sociated feature called the pallial line may equipment used to select specimens far color patterns on living seashells are useful fluoresce well. This makes it possible to see this article and our exhibit. We thank them characters for biologists who classify them, these features and some small accessory and other unnamed friends for their gener- their preservation on fossil ones gives de- muscle scars that otherwise might not be ous assistance and look forward to the ap- lighted paleontologists another character easily visible on fossils. pearance of some serious research which with which to compare the fossil with the Although the color pattern fluorescence they may be encouraging or preparing living seashells and to distinguish among is more pronounced in specimens from about the origins of this mysterious fossil the various kinds of fossils. southern Florida than from any other fossil light show that bears the spectral kiss of Many of the Florida fossil seashells locality reported, the muscle scars and pal- beauty. fluoresce only on parts of the shell that were lial lines of fossil clams from many localities exposed to sunlight while they lay partly in our collections, including the Palos Ver- reburied on the canal spoil banks. Some des Peninsula raised beaches, may Perseverance brought TERRA this un- that fluoresce only slightly or not at all will fluoresce readily. This is a new research usual article by Edward C. Wilson, curator do so brilliantly after being soaked in ordi- tool and has assisted us already in locating of Invertebrate Paleontology at the Natural nary household bleach for one or more tiny accessory muscle scars on some fossil History Museum of Los Angeles County. days. Many will not fluoresce even after scallop shells that establish them as having The shells have never been published in exposure to sunlight or treatment with been swimmers. fluorescent color before and it took a year bleach. Living seashells will not fluoresce at Our museum is the first to have a perma- to bring them, special photographic all. The reasons for the fluorescence and its nent display of Florida fluorescent fossil equipment, and Photographer Reynolds differential distribution in Florida fossil seashells. They are in a special case in the together. seashells have not been reported. Invertebrate Fossil Exhibits. Many of these Color patterns appear only on the out- specimens are gifts or exchanges from sides of living seashells and the specimens Jean and Crawford Cate of Brentwood, figured for this article are snails from the Shirley and Bob Hoerle of West Palm Florida deposits chosen because they are Beach, and Emily and Harold Vokes of New This schematic is the key which identifies the shells on pages 12 and 13, which are a few of the fossil seashells ten to fifteen million years old from Okeechobee County, Florida in the collections of the Natural History Museum of Los Angeles County. All specimens are approximately natural size in the photographs. The specimens on page 13 were photographed under short wave ultraviolet light by Lawrence S. Reynolds with an 8 by 10 inch view camera, 360 mm f 5.6 Symnar lens, Kodak Wratten 2E ultraviolet and CC 30 red filters, Ektachrome professional daylight sheet film, against a background of black plexiglass. Exposure: 12 hours at f32. On page 12 the same specimens were photographed under ordinary light by Mr. Reynolds. 1. Architectonic a nobilis Roding, 1798 2. Fasciolaria rhomboidea (?) Rogers, 1839 3. Conus n. sp. 4. Conus n. sp. 5. Conus waccamawensis Smith, 1930 6. Conus n. sp. 7. Terebra unilineata (Conrad, 1841) 8. Aurinia obtusa (Emmons, 1858) 9-11 Scaphella trenholmii (Tuomey and Holmes, 1856) 12. Natica plicatella Conrad, 1863 13. Siphocypraea carolinensis (Conrad, 1841) 14-15 Cancellaria rotunda floridana Olsson and Petit, 1968 .