Description
Metacalycoceras wintoni Ammonite Fossil – Lewisville Member, Woodbine Formation, Texas
This genuine Metacalycoceras wintoni ammonite fossil is a highly collectable Upper Cretaceous marine cephalopod specimen from the Lewisville Member of the Woodbine Formation, Tarrant County, Texas, USA. Dating from the Cenomanian Stage of the Upper Cretaceous, approximately 100 to 94 million years old, this fossil represents an ammonite from the ancient marine environments that once covered parts of North America during a time of high global sea levels.
This fossil is a genuine specimen and includes a Certificate of Authenticity lifetime guarantee generic card. It has been carefully chosen as an individual fossil specimen, with a photo that shows the actual piece you will receive. Full sizing please see photo.
Geology and Geological Age
Metacalycoceras wintoni comes from the Cenomanian Stage of the Upper Cretaceous Period, one of the earliest stages of the Late Cretaceous. During this time, much of central North America was influenced by rising seas and the development of shallow marine to coastal environments associated with the Western Interior Seaway and the Gulf Coastal Plain.
The Lewisville Member is part of the Woodbine Formation, a well-known Cretaceous geological unit in north-central Texas. The Woodbine Formation includes sediments deposited in coastal, deltaic, estuarine and shallow marine settings, reflecting changing sea levels and shifting shorelines during the Cenomanian. Fossils from this formation are important because they record the diverse life that inhabited the warm Cretaceous seas and nearshore environments of Texas.
Fossil Type and Species
This specimen belongs to the ammonite species Metacalycoceras wintoni, a recognised Cenomanian ammonite associated with the Woodbine Formation of Texas. Metacalycoceras is an ammonite genus within the order Ammonitida and is generally placed among the acanthoceratid ammonites, a group known for their strong ribbing, ornamented shells and important biostratigraphic value in Cretaceous marine rocks.
Ammonites were extinct marine cephalopods related to modern squid, octopus and cuttlefish, but unlike those living relatives, ammonites possessed a coiled external shell divided internally into chambers. The animal lived in the outer body chamber, while the older chambers helped control buoyancy. This made ammonites active and successful marine animals throughout much of the Mesozoic Era.
Morphology and Collectable Features
Metacalycoceras wintoni is especially valued for its classic Cretaceous ammonite form. Depending on preservation and growth stage, specimens may show strong ribbing, rounded to compressed whorls, tubercles or nodular ornament, and a defined coiled shell outline. These sculptural features are typical of many acanthoceratid ammonites and give the fossil a striking natural appearance.
The ribs and tubercles on ammonites were not simply decorative; they formed part of the shell’s structure and may have helped strengthen the shell or influenced hydrodynamics. In well-preserved ammonites, suture lines may also be visible, marking where the internal chamber walls joined the outer shell. These complex sutures are one of the key features used by palaeontologists when studying and identifying ammonites.
This fossil makes an excellent display piece for collectors interested in Cretaceous ammonites, Texas fossils, Woodbine Formation specimens, marine cephalopods and Upper Cretaceous palaeontology.
Lewisville Member and Woodbine Formation
The Lewisville Member of the Woodbine Formation is an important fossil-bearing unit in Texas. It is known for preserving evidence of changing coastal and marine environments during the Cenomanian. The sediments of the Woodbine Formation were laid down at a time when rivers, deltas, shorelines and shallow seas interacted across the region, creating a variety of habitats for marine and coastal life.
Fossils from the Lewisville Member can include ammonites, bivalves, gastropods, oysters, fish remains and other marine organisms. The presence of ammonites such as Metacalycoceras wintoni helps demonstrate the marine influence within these deposits and provides useful evidence for dating and correlating the rocks.
Depositional Environment
This Metacalycoceras wintoni ammonite was preserved in sediments laid down in a warm Cretaceous coastal to shallow marine setting. After the ammonite died, its shell settled into the sediment and was gradually buried by fine sand, silt, mud or carbonate-rich material. Over millions of years, mineral-rich groundwater moved through the surrounding sediment, allowing the shell to fossilise.
The resulting fossil is a natural record of marine life from Cenomanian Texas, when the landscape was very different from today. Instead of modern inland terrain, the region was influenced by ancient waterways, coastal plains and shallow seas connected to wider Cretaceous marine systems.
Authenticity and Display
This is a genuine Metacalycoceras wintoni ammonite fossil from the Lewisville Member, Woodbine Formation, Cenomanian, Upper Cretaceous of Tarrant County, Texas, USA. It includes a Certificate of Authenticity lifetime guarantee generic card, making it a desirable addition to a fossil collection, educational display, geology study set or natural history cabinet.
The fossil has been carefully selected, and the photo shows the actual specimen you will receive. Full sizing please see photo.
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