Every year, digs are being conducted along the Jurassic Coast in the UK. For every dig, scientists were able to find hundreds of fossilized ammonites.

Ammonites are ancient sea creatures that had a ribbed spiral-form shell. This is cephalopods that lived between 240 to 65 million years ago. It has been said that ammonites have been wiped out along with dinosaurs. Squid, octopus, and cuttlefish are the nearest living relatives of the ancient creatures.

Ammonite shells follow a basic design with an expanding cone that spiral around a center point. They're generally a flattish spiral that gets thicker with every whorl. Ammonite shells usually have the following features:

  • Ribs that run across the whorls

  • Growth lines

  • Knobs or spherical structures extending from ribs 

  • Spines or protrusions that extend from the ribs tapered to a point

  • Tubercles or different protrusions extending from the ribs, which include spine bases

  • Keels or structures adorning the outer edge of whorls

  • Spines and lappets or protrusions that extend from the ammonite shell's opening

Ammonites are thought to have interlocking chamber shapes, giving the shell added strength, enabling the animal to dive at greater depths without water pressure damage. A complete ammonite fossil cut in half and polished would reveal the shell's chambers, divided into the body and the phragmocone or chambered part of the cephalopod's shell.

The body chamber is a long chamber, which is fossilized in various colors to the phragmocone chambers. After the animal died, the sediment had filled the body chamber and the soft parts rotted. The chambers of the phragmocone were sealed off and mineralized over a prolonged period because of the mineral-rich water percolation through the shell.

A recent dig far from the usual site has yielded an unexpected discovery. Scientists found a fossil of an ammonite trapped in amber during their search in northern Myanmar.

The sea creature was said to have lived around 99 million years ago. The scientists noted that finding an ammonite in amber is one of the rarest finds of fossil to date. The amber where the fossil is encapsulated is in fact hardened tree resin from extinct coniferous trees.

Normally forest dwelling creatures are those that are caught in amber and are eventually encased and immortalized as the material would render the creatures immobilized. The material would then harden over time, preserving the embedded creatures.

The chunk of amber is measured at 33mm long, 9.5mm wide, and 29mm high. It has encapsulated a wide range of different organisms that existed during the Cenomanian age.

This rare find was reported by Professor Wang Bo from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (NIGPAS).

The study states that there are at least 40 individual animals immortalized in the chunk of amber. Among the terrestrial fauna, the most abundant are mites.

In the study, the researchers have pointed out that amber is fossilized tree resin which usually has terrestrial and rarely aquatic organisms embedded in it. They have also pointed out that marine fossils are extremely rare in Cenozoic and Cretaceous ambers.

Other creatures found in the chunk of amber include millipedes, beetles, spiders, wasps, cockroaches, and flies. These are living organisms that would have lived on the floor of the forest.

However, as previously stated, there is also marine fauna, other than the ammonite, that is embedded in the crystallized resin. This includes sea slaters and sea snails. The sea slaters found in the amber are much like those that currently thrive on the seashore.

For the scientists to be able to obtain high-resolution three-dimensional images of the organisms, they used x-ray microcomputed tomography (micro-CT). The scientists found out that the ammonite is a young Puzosia (Bhimaites). The presence of such a sea creature in the chunk of amber supports the late Albian and early Cenomanian age for the amber deposit.

The discovery decided to represent a very rare example of dating using the inclusions in an amber chunk.
Further probing into the ammonite specimen have shown the researchers that the outer shell of the ammonite was broken away. They have also noted that the entrance of the shelf is full of sand.

The scientists pointed out that the marine gastropods and the ammonite were already dead and underwent abrasions on the seashore before those were caught in amber as suggested by the incomplete preservation and lack of soft bodies. Their findings have also suggested that the flying insects were trapped in the resin while it was still on the plant, while the sea creatures were picked up when the amber fell to the ground and rolled onto the beach.