Abstract
Copepods are aquatic microcrustaceans and represent the most abundant metazoans on Earth, outnumbering insects and nematode worms. Their position of numerical world predominance can be attributed to three principal radiation events, i.e. their major habitat shift into the marine plankton, the colonization of freshwater and semiterrestrial environments, and the evolution of parasitism. Their variety of life strategies has generated an incredible morphological plasticity and disparity in body form and shape that are arguably unrivalled among the Crustacea. Although their chitinous exoskeleton is largely resistant to chemical degradation copepods are exceedingly scarce in the geological record with limited body fossil evidence being available for only three of the eight currently recognized orders. The preservation of aquatic arthropods in amber is unusual but offers a unique insight into ancient subtropical and tropical ecosystems. Here we report the first discovery of amber-preserved harpacticoid copepods, represented by ten putative species belonging to five families, based on Early Miocene (22.8 million years ago) samples from Chiapas, southeast Mexico. Their close resemblance to Recent mangrove-associated copepods highlights the antiquity of the specialized harpacticoid fauna living in this habitat. With the taxa reported herein, the Mexican amber holds the greatest diversity of fossil copepods worldwide.
Highlights
Fossil invertebrate hosts Eggs/spermatophores collections from the same formation resulted in numerous exceptionally preserved fossils, including adult and larval stages, of a new species of the extant genus Apocyclops Lindberg, 19426
The primarily benthic Harpacticoida currently includes about 4,675 valid species placed in 652 genera and 58 families and is arguably the order that has undergone the greatest diversification in copepod evolution
Fossilized specimens assignable to Cletocamptus (Canthocamptidae incertae sedis) have been found in sedimentary lake deposits associated with Boron minerals in the Barstow Formation in the Mojave Desert in Southern California, dating to the Early-Middle Miocene (13.4–19.3 million years (Ma))[4]
Summary
Fossil invertebrate hosts Eggs/spermatophores collections from the same formation resulted in numerous exceptionally preserved fossils, including adult and larval stages, of a new species of the extant genus Apocyclops Lindberg, 19426. Resins are produced by a wide range of flowering plants and by conifers, only two plant genera exudate it in a form that resists biological, chemical and physical degradation and are responsible for most of the fossiliferous amber deposits known today It occurs in many areas of the globe, representing approximately 170 amber deposits, some dating from as early as the Late Carboniferous Crustacean groups (ostracods, tanaidaceans, amphipods and isopods) not usually found as inclusions in amber are relatively common in this area and are found associated with both freshwater and terrestrial insects This mixture of ecologically diverse groups suggests an allochtonous assemblage deposited in small shallow tidal-flat ponds adjacent to a mangrove-like shore[37]. The botanical source of Chiapas amber has recently been determined as being the result of resinous exudates produced during the late Oligocene to early Miocene by two species of the leguminose tree genus Hymenaea L. (family Fabaceae), H. mexicana Poinar & Brown, 2002 and H. allendis Calvillo-Canadell, Cevallos-Ferriz &
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