Central America and the Caribbean

Central America and the Caribbean - so-called nuclear America - is largely devoid of fossil insect deposits, with two very dramatic exceptions: rich deposits of Oligocene and Miocene amber from Chiapas, Mexico, and the Dominican Republic (Figure 2.67), respectively. The amber from both deposits was formed by extinct tree species in the genus

2.67. Hillside excavation of Miocene amber at the Palo Alto mine, northern Dominican Republic, ca. 1995. Preservation in Dominican amber is perhaps the finest of all ambers. Photo: R. Larimer.

Hymenaea, which today comprises canopy species found throughout lowland rain to deciduous dry forests of the neotropics (one species, H. verrucosa, occurs in eastern Africa). The living species exude copious resin, as the extinct ones did. Botanical source of the amber is confirmed by chemistry and abundant inclusions of sepals, flowers, and leaves (Langenheim, 1966; Hueber and Langenheim, 1986).

Fossils in Dominican amber are more renowned, even though Mexican amber has been studied scientifically longer (Hurd et al., 1962; various papers in University of California Publications in Entomology, Volume 31 [1963], volume 63 [1971]: see Engel, 2004a). This may be attributable to more effective commercial exploitation of Dominican amber, more productive deposits, or both. Inclusions in Mexican amber are usually slightly to obviously compressed; those in Dominican amber are often perfect. Indeed, the preservation of organisms in Dominican amber are preserved with a finer and more consistent fidelity - externally and internally - than is any other amber deposit in the world (e.g., Grimaldi et al., 1994). Arthropods in Dominican amber are arguably the most beautiful such fossils in the world and the most diverse Miocene fauna of insects known. Unfortunately, despite its significance, the age of Dominican amber was confused, with unsubstantiated but popularized claims of Eocene age. It is now known to be definitively younger (Grimaldi, 1994b); specifically mid-Miocene, approximately 17-20 myo

(Iturralde-Vinent and MacPhee, 1996). Age of Mexican amber appears to be Late Oligocene, based on foraminiferans. The most significant collection of Mexican amber is at the University of California Museum of Paleontology, Berkeley, assembled by Hurd and others in the 1950s.

The first serious work on Dominican amber inclusions began with Dieter Schlee at the Staatlichen Museum für Naturkunde in Stuttgart, Germany. He assembled an impressive collection (Schlee, 1980, 1984, 1986, 1990), much of it on permanent display. The Morone Collection in Turin, Italy, is the finest one, containing many superb specimens of rare and impressive organisms (e.g., Grimaldi, 1996) (e.g., Figures 3.16, 9.24, 10.43, 13.69). The American Museum of Natural History (New York), Smithsonian Institution (Washington, D.C.), and Natural History Museum (London) have collections amounting to approximately 20,000 pieces containing 30,000 inclusions, mostly smaller insects and arachnids. Published and unpublished work on these collections indicates that over 400 families and 1,500 species of insects exist in Dominican amber. Many of the same families and even genera of insects occur in Mexican and Dominican amber, with a great variety of other impressive inclusions found in the latter. Dominican amber contains, for example, diverse plants (especially flowers, some 30 families); solpugids, scorpions, and mature amblypygids (Figure 3.16); feathers; Anolis and Sphaerodactylus lizards; Eleutherodactylus frogs;

and even the partial remains of a mammal (Grimaldi, 1996; MacPhee and Grimaldi, 1996).

The paleobiota in both deposits is distinctly tropical. Most species are related to ones presently living in Central or South America, though there have been impressive extinctions. For example, Mastotermes termites (Figure 7.81) and a variety of other insects in Dominican and Mexican amber belong to groups now found only in Australia, Africa, or southeast Asia. Caribbean landmasses had a complex history of drift, submergence, and land bridges (Iturralde-Vinent and MacPhee, 1996), so understanding the evolution of its biota is challenging. Dominican and Mexican amber contributes unique insight on this subject, as well as on the origins of modern tropical ecosystems.

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