Cretaceous Amber from East Africa sheds Light on Cretaceous Ecosystem

The discovery of a deposit of amber (fossilised tree resin) in Ethiopia is providing scientists with the opportunity to learn more about the evolution of flowering plants.  This exceptionally rare discovery, no other strata containing amber dating from the Cretaceous is known in the southern hemisphere, is allowing researchers to learn more about insects, fungi and even bacteria that shared the environment with dinosaurs.

Amber is fossilised sap that has been produced by certain types of trees.  The resin seeps out of cuts or other parts of the damaged tree and helps to prevent infection and disease.  Organisms such as insects, pollen grains and even small lizards and frogs can be caught in the sticky substance and preserved in exquisite detail.  The tree sap that hardens and is preserved is usually produced by conifers (gymnosperms), but certain types of angiosperms (flowering trees) can produce amber.  Most amber known is from deposits that are less than seventy million years old.  The Ethiopian amber has been dated to approximately 95 million years ago ( Cenomanian faunal stage).

In a paper published in the scientific journal “The Proceedings of the National Academy of Sciences”, a description is provided of the new types of insects, other arthropods, nematodes, fungi and bacteria that have been discovered entombed in the hardened tree sap.  The research team hopes that the analysis of these nodules will provide further information on the development and the diversification of flowering plants.

A Nodule of Ethiopian Amber dating from the Cretaceous

Picture Credit: PNAS/Matthias Svojtka

One of the authors of the paper, Paul Nascimbene of the Division of Invertebrate Zoology at the American Museum of Natural History (New York) commented:

Until now, we had discovered virtually no Cretaceous amber sites from the southern hemisphere’s Gondwanan supercontinent.  Significant Cretaceous amber deposits had been found primarily in North America and Eurasia.”

The date of the amber deposit could be very significant as it was during this part of the Cretaceous that flowering plants (angiosperms) began to diversify and become the dominant form of plant life.  Alexander Schmidt, of the University of Göttingen in Germany, another author of the report, stated:

“The first angiosperms, or flowering plants, appeared and diversified in the Cretaceous.  Their rise to dominance drastically changed terrestrial ecosystems, and the Ethiopian amber deposit sheds light on this time of change.”

Some of the research team worked on the geological setting and the fossils entombed within the amber, whilst Nascimbene, along with Kenneth Anderson from Southern Illinois University, studied the amber nodules.  They found that the resin that seeped from these Cretaceous Gondwanan trees is similar chemically to more recent ambers from flowering plants in Miocene deposits found in Mexico and the Dominican Republic.  The amber’s chemical designation is Class Ic, and it is the only Ic fossil resin discovered thus far from the Cretaceous.  All other documented Cretaceous ambers are definitively from non-flowering plants, (gymnosperms).

Paul Nascimbene went onto add:

“The tree that produced the sap is still unknown, but the amber’s chemistry is surprisingly very much like that of a group of more recent New World angiosperms called Hymenaea.”

The Hymenaea are a family of trees and shrubs native to the tropics of the Americas.  They are mostly evergreen and a number of genera are still living today.  The researchers state that the amber could be from an early angiosperm or a previously unknown conifer that was quite distinct from the other known Cretaceous amber producing gymnosperms.

Research team members have discovered to date thirty arthropods, trapped in the amber from at least thirteen families of insects and spiders.  These fossils represent some of the earliest African fossil records for a variety of arthropods, including wasps, barklice, moths, beetles, a primitive ant, a rare insect called a zorapteran, and a sheet-web weaving spider. Parasitic fungi that lived on the resin-bearing trees were also found, as well as filaments of bacteria and the remains of flowering plants and ferns.

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