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Exogyra Bivalve Fossil Cretaceous Texas USA Genuine Authentic Specimen with COA

Exogyra Bivalve Fossil Cretaceous Texas USA Genuine Authentic Specimen with COA

£10.20

All of our Fossils are 100% Genuine Specimens & come with a Certificate of Authenticity

**Please note: Some Fossils maybe propped up for photo purposes**

Specimen: Exogyra Bivalve

Age: Cretaceous

Location: Texas, USA

Size (picture scale cube=1cm):   23 x 15 x 14mm (0.91 x 0.59 x 0.55 inches)

ACTUAL AS SEEN: The image shows the EXACT specimen you will receive. The specimen has been carefully hand selected and photographed. Measurements are as accurate as possible, though be aware measuring precise dimensions can be difficult from irregular shaped items. Whilst we portray colours as close to life-like as we can, colours will vary if taken in sunlight, indoors, from monitor to monitor and device to device. Once this specimen is sold, we will update this listing with new similar selected item, with a new photo and dimensions.

What is a fossil?

The word Fossil used to be defined as ‘something dug up’. Now-a-days it generally means ‘The remains or trace evidence of prehistoric life’. The study of fossils is called palaeontology; someone who collects and studies them is called a palaeontologists. Fossils can be as tiny as a grain of pollen or a seed for e.g. or as huge as a limb bone from a giant dinosaur. For animal or plant remains to have become ‘fossilised ‘, they must go through a certain process that preserves them for up to millions of years after they have died. Usually it is only the hard parts of plants and animals that survive this long process.

How Fossils Formed

 

The most common method of how fossils formed is once an animal or plant dies, it falls to the ground, and is covered by sediment. This is often sediments brought from water. In the diagram above, the ammonite died in a river, and sediments over time covered the ammonite (shown in the second diagram). Finally after hundreds of thousands, or millions of years, the land is eroded and the fossil can be seen.

Of the vast amount of prehistoric life that died, it is only a tiny amount that has survived the fossilisation process. The conditions when the majority of life died were just not right at that time, to preserve them. Most fossils are found in sedimentary rocks which were formed from the sediments of rivers, lakes and seas. The majority of the animal and plant fossils we find today, had originally died near these areas, got broken up and deposited on the beds of the rivers, lakes and seas. The sediments covered them and over time some of the layers grew so thick that many of them got crushed. The sediments compacted and over time and turned to rock. The rocks shifted, moved and became exposed to the elements. This process can take up to several hundred million years. Now as the rocks erode or are quarried for example, the fossils become exposed and can be collected.

The Best conditions for Fossilisation

1. The quick burial of animal remains in moist sediments. This prevents scavengers from eating and bacteria from decaying them.

2. The quick burial in volcanic ash. Many dinosaur bones in the American west have been found buried in volcanic ash.

3. The presence of hard body or plant parts, teeth, bones, shell and wood for example.

4. Unchanging temperature conditions.

5. Ground water that is heavily mineralised.

6. Sediments that are very fine make a better burial than coarser gravels.

7. Calm conditions, so that remains are not broken up (by wave or currant action for example)

(Actual as seen)

Only 1 left in stock

SKU: FP9615 Category:

Description

Rare Exogyra Bivalve Fossil from Texas, USA

This listing presents an authentic Exogyra bivalve fossil from the Cretaceous period, discovered in Texas, USA. Exogyra belongs to an extinct group of oysters, notable for their thick, coiled shells and unique attachment features that made them one of the most recognisable bivalves of the Late Mesozoic seas. This specimen is a genuine piece of Earth’s natural history, dating back approximately 145 to 66 million years ago. Each photo shows the actual fossil you will receive, and a Certificate of Authenticity is included to verify its provenance. The scale cube in the photo equals 1 cm, providing accurate size reference.

Geological Context

  • Geological Period: Cretaceous (145–66 million years ago)

  • Location: Texas, USA

  • Depositional Environment: Shallow marine environments of the Western Interior Seaway

During the Cretaceous, much of North America was submerged beneath the Western Interior Seaway, a vast inland sea that stretched from the Arctic Ocean to the Gulf of Mexico. The warm, nutrient-rich waters provided an ideal habitat for bivalves like Exogyra, along with ammonites, marine reptiles, and early forms of fish. Sediments deposited in this environment were largely chalks, marls, and shales, which preserved marine life in remarkable detail.

Taxonomic Classification

  • Genus: Exogyra

  • Family: Gryphaeidae

  • Superfamily: Ostreoidea

  • Order: Ostreida

  • Class: Bivalvia

Morphological Features

This fossil shows the classic morphology of Exogyra:

  • A thick, strongly curved left valve that once cemented to hard surfaces such as shells, rocks, or seafloor debris.

  • Distinctive coiled or twisted growth lines, giving the shell a rugged and weathered appearance.

  • The right valve is flatter, often acting as a lid to protect the soft tissues within.

  • Growth ridges across the surface provide clear evidence of its life history and environmental conditions.

These unique features distinguish Exogyra from other bivalves and make it a key fossil for identifying Cretaceous-age strata in North America.

Scientific and Collecting Importance

Exogyra fossils are widely recognised as index fossils, helping geologists identify and date the layers of rock in which they occur. They are especially abundant in Cretaceous marine deposits, making them crucial for reconstructing ancient seaways and environments. Their coiled shell structures also provide insights into how these oysters adapted to crowded sea floors, attaching securely in shifting sedimentary conditions.

For collectors, this fossil represents a classic Cretaceous oyster, combining scientific importance with aesthetic appeal. Its robust, curved shell structure makes it an excellent display piece for fossil enthusiasts, natural history collectors, or educational purposes.

Key Details

  • Fossil Type: Exogyra Bivalve (Oyster)

  • Age: Cretaceous (145–66 million years ago)

  • Location: Texas, USA

  • Features: Twisted, coiled shell with strong growth ridges

  • Authenticity: 100% genuine fossil with Certificate of Authenticity

Authenticity and Presentation

All of our fossils are guaranteed 100% authentic specimens. This Exogyra fossil has been carefully selected for both quality and scientific relevance. The photos display the actual item you will receive, ensuring transparency and confidence in your purchase. A Certificate of Authenticity is included with every specimen, making this fossil both a secure investment and a fascinating piece of natural history.

This genuine Exogyra bivalve fossil from Texas is not just a relic of the Cretaceous seas but a captivating display piece that connects you directly with the age of dinosaurs. It is an excellent addition to any fossil collection, museum display, or educational setting.

Additional information

Weight 10 g
Era

Cretaceous
Origin

USA

Cretaceous Information

The Cretaceous Period (145–66 million years ago) was the final era of the Mesozoic, marked by the dominance of dinosaurs and the rise of flowering plants. It had a warm, greenhouse climate, with high sea levels that created vast shallow inland seas. Marine life flourished, including mosasaurs, ammonites, and rudist reefs, while the land was ruled by iconic dinosaurs like Tyrannosaurus rex, Triceratops, and Spinosaurus. Mammals and birds diversified, and insects thrived. The period ended with the mass extinction event, likely caused by an asteroid impact, wiping out the dinosaurs and paving the way for the rise of mammals in the Cenozoic.

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