Rare Mazon Creek Split Fossil Fern Nodule Annularia Whirl Carboniferous Illinois USA COA

Description

Genuine Mazon Creek Fossil Fern – Annularia Whirl

This rare and beautifully preserved Mazon Creek fossil fern nodule contains the distinctive whorled leaf arrangement of Annularia, an ancient plant belonging to the Calamites group of horsetails. Dating to the Carboniferous Period, around 307–309 million years ago, this specimen comes from the world-famous Mazon Creek Lagerstätte in Illinois, USA. These deposits are renowned for preserving delicate plant and animal life in siderite nodules, creating natural time capsules that capture extraordinary detail. The fossil pictured is the exact specimen you will receive, and as always, it comes with a Certificate of Authenticity.

Geological Context

• Geological Period: Carboniferous (Pennsylvanian Subperiod)
• Age: ~307–309 million years
• Formation: Francis Creek Shale, Mazon Creek Lagerstätte
• Location: Mazon Creek, Illinois, USA

The Francis Creek Shale represents a deltaic, swampy environment where rivers and floodplains met coastal wetlands. Rapid burial in fine sediments and early mineralisation preserved not only robust plant structures but also delicate features like leaves and whorls, offering an unparalleled window into Carboniferous ecosystems.

Scientific Classification

• Kingdom: Plantae
• Division: Equisetophyta (Horsetails)
• Order: Calamitales
• Genus: Annularia

Annularia represents the leaf whorls of the Calamites, giant tree-like horsetails that could grow over 10 meters tall. Unlike modern horsetails (Equisetum), these ancient plants formed part of dense swamp forests that contributed significantly to the formation of Carboniferous coal beds.

Morphological Features

This specimen shows the classic whorl structure of Annularia, where leaves radiate outward in circular patterns from a central node. Key features include:

• Leaf Arrangement: Symmetrical whorls resembling a starburst or wheel.
• Leaf Shape: Linear leaves with tapered ends, evenly spaced around the stem node.
• Clarity of Preservation: Fine detail preserved within the siderite matrix, highlighting the characteristic pattern that makes Annularia fossils so recognisable.

This type of preservation is especially valuable because it allows the reconstruction of ancient swamp flora in remarkable detail.

Paleoenvironment and Significance

During the Carboniferous, Illinois was covered by vast equatorial wetlands dominated by lycopsids, seed ferns, giant horsetails like Calamites, and true ferns. These dense forests created thick peat layers that eventually formed much of the world’s coal deposits.

The Mazon Creek Lagerstätte is celebrated for its exceptional preservation of both flora and fauna, from insects and fish to plants such as Pecopteris and Annularia. Fossils like this illustrate the incredible biodiversity of these ancient coal swamp ecosystems and provide invaluable insights into early plant evolution.

Key Details

• Specimen: Annularia fossil fern whorl
• Type: Split siderite nodule from Mazon Creek
• Age: Carboniferous (~307–309 million years old)
• Location: Mazon Creek, Illinois, USA
• Authenticity: Guaranteed genuine, with Certificate of Authenticity included
• Sizing: Shown in photos with 1cm scale cube

Collectability and Display Value

Mazon Creek fossils are among the most sought-after plant fossils worldwide due to their rarity, exceptional preservation, and scientific importance. Annularia fossils are particularly prized for their striking, symmetrical whorled patterns, making them not only valuable for research but also highly aesthetic display pieces.

This fossil represents a tangible link to the lush, coal-forming forests of the Carboniferous – an era when giant horsetails, towering lycopsids, and early ferns dominated the landscape. For collectors, educators, and fossil enthusiasts, this specimen offers both scientific interest and natural beauty, making it an exceptional addition to any collection.