Petrified wood.

There are two principal ways that trees become fossilized into petrified wood.  Volcanic activity can quickly kill and bury entire forests with silica ash. As well, trees that are killed by flooding or drowning and become submerged in the sediments can over millions of years and under the right conditions of pH and temperature transform into fossils. This happens through the processes of permineralization and petrifaction (mineral replacement).  Water, saturated in minerals such as silica and iron oxides, soaks and permeates into the porous tissues of wood and the minerals in solution precipitate using the cell walls as a template. Later after longer time periods, the minerals fill in the cells and connecting areas.  The striking array of colors of petrified wood are due to the kinds of minerals that are deposited from the surround mud and water. White colored petrified wood is due to a high level of silicon dioxide. Green and blue colors are created by copper and manganese. The bright red colors of the petrified forests of Arizona are due to high levels of iron. 

TRilobites.

Trilobites were a large group marine arthropods with more than 20,000 described species – related to other hard shelled creatures such as crabs, scorpions and insects. They all had jointed legs. The name trilobite refers to the 3 longitudinal divisions of a trilobites body - a central axial lobe with a pleural lobe on each side. Like modern insects, they also have 3 divisions of their body; a head or cephalon, a thorax, and a tail area or pygidium.
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These fascinating ancient creatures lived throughout most of the Paleozoic Era, for about 300 million years. The earliest species date back to the Cambrian Period, about 520 million years ago. Paleontologists have grouped trilobites into 10 distinct Orders, which are extremely varied. A bizarre array of shapes and sizes ranging in size from just over 1 mm to 720 mm. Some types were covered in huge curving spines, reminiscent of many visions of aliens in pop culture. Trilobites swam and crawled through ancient oceans from the Cambrian, Ordovician, Silurian, Devonian Carboniferous and Permian Periods. This planet’s greatest extinction at the Permian/Triassic border 250 million years ago wiped out all of the trilobites as well as 95 % of all marine organisms! Trilobites never had a chance to meet the dinosaurs. 

AMMonites.

Ammonites have intrigued and fascinated humans for thousands of years. Many cultures from aboriginal bushmen in Australia, to the ancient Egyptians collected and treasured these prehistoric and beautiful fossils. Does it have anything to do with that Fibonacci spiral pattern of ammonites that mirrors the galaxies?

Ammonites belong to the Mollusca Phylum in a separate Class known as Cephalopods – the head-footed creatures like the present day octopus and squid. They swam in ancient oceans from the Devonian (about 400 million years ago) to their extinction along with the dinosaurs in the Cretaceous, 65 million years ago.

These incredible invertebrates ranged in size from tiny creatures only a few centimeters in diameter to the monstrous Cretaceous ammonite Parapuzosia (Pachydiscus) seppenradensis which grew to about 3 meters in diameter and would probably of weighed in at close to 1500 kgs! 

Ammonites were free floating creatures (nekton) that were attacked by plesiosaurs and mosasaurs – two groups of giagantic marine reptiles who patrolled the oceans with powerful pairs of flippers. One way the ammonite could avoid attack was to quickly change buoyancy and zig zag and sink rapidly. Ammonites has a thin tube called the siphuncle located close to the edge of the shell which linked all the septa chambers through tiny holes. Ammonites could drain gases from some of the septa or chambers and fill them with water increasing their specific gravity. Hopefully this saved them from becoming mosasaur lunch!