Description
Presented here is a rare Budaiceras mexicum ammonite fossil, an exceptional specimen from the Eagle Ford Formation, Texas, USA, dating to the Cenomanian stage of the Late Cretaceous (approximately 100–94 million years ago). Ammonites of this genus are highly sought after by collectors due to their distinctive morphology and their significance as index fossils for Cenomanian marine deposits.
The fossil offered is the exact specimen shown in the photographs, with a 1 cm scale cube included for accurate sizing. Every detail of this ammonite has been carefully preserved, cleaned, and prepared to highlight its natural features. As with all of our fossils, it comes with a Certificate of Authenticity to guarantee it as a 100% genuine specimen.
Geological Context
The Eagle Ford Formation is one of North America’s most fossil-rich Cenomanian deposits, known for its dark calcareous shales and marls deposited in the shallow waters of the Western Interior Seaway. This inland sea covered much of central North America during the Late Cretaceous, providing a rich marine ecosystem for ammonites, bivalves, crustaceans, fish, and marine reptiles.
During the Cenomanian, global sea levels rose significantly, creating warm, shallow seas across the continents. These conditions not only supported diverse marine life but also facilitated the preservation of fossils in fine-grained sediments, making the Eagle Ford a globally important fossil site.
Scientific Classification
- Phylum: Mollusca
- Class: Cephalopoda
- Order: Ammonitida
- Superfamily: Acanthoceratoidea
- Family: Acanthoceratidae
- Genus: Budaiceras
- Species: Budaiceras mexicum
As a member of the Acanthoceratidae, Budaiceras is part of a family well known for strongly ornamented shells and evolutionary importance in Cretaceous seas.
Morphology and Features
The Budaiceras mexicum ammonite is characterised by:
- Robust, moderately inflated whorls with clearly visible ornamentation.
- Prominent ribs and tubercles across the shell, a hallmark of acanthoceratid ammonites.
- Complex suture lines, typical of Cretaceous ammonites, which add both aesthetic and scientific value.
- A shell structure adapted for buoyancy control, allowing the ammonite to occupy mid-water ecological niches.
These features make Budaiceras instantly recognisable and highly prized among fossil enthusiasts.
Paleoenvironment
This ammonite lived in the shallow, warm waters of the Western Interior Seaway, which stretched from the Gulf of Mexico to the Arctic Ocean during the Late Cretaceous. The ecosystem was rich with marine life, and ammonites such as Budaiceras played an essential role as active predators feeding on smaller invertebrates and plankton.
The Cenomanian seas of Texas were a hub of evolutionary activity, and ammonites like this specimen provide an important biostratigraphic marker for understanding the age and sequence of these marine deposits.
Collector and Display Value
This specimen is a rare example of Budaiceras mexicum, combining visual appeal with historical and scientific significance. Its distinct ribbing and tuberculation make it a stunning display fossil, while its role as an index fossil gives it importance in paleontological study.
- Locality: Eagle Ford Formation, Texas, USA
- Age: Cenomanian, Cretaceous (~100–94 million years ago)
- Fossil Type: Ammonite (Budaiceras mexicum)
A truly exceptional fossil, perfect for collectors, educators, and enthusiasts of Earth’s deep history. This ammonite is not just a display piece—it is a genuine part of the evolutionary and geological record.
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