Rare Mazon Creek Split Fossil Palaeoxyris Prendeli Shark Egg Case Carboniferous Illinois USA with Certificate

Description Rare Mazon Creek Palaeoxyris Prendeli Shark Egg Case Fossil Offered here is a rare Mazon Creek split fossil of Palaeoxyris prendeli, a fossilised shark egg case from the Carboniferous Period. Found in the world-famous fossil beds of Mazon Creek, Illinois, USA, this specimen dates to around 307 million years ago. The specimen is preserved in a siderite nodule that naturally split open to reveal the fossil within, showcasing its distinctive spiral form. This is the exact piece you will receive, photographed with a 1 cm scale cube for accurate sizing. All of our fossils are 100% genuine and come with a Certificate of Authenticity for complete assurance. Geological Context Geological Period: Carboniferous (Pennsylvanian Subperiod) Age: Approximately 307 million years old Formation: Francis Creek Shale, Carbondale Formation Locality: Mazon Creek, Illinois, USA The Mazon Creek deposits are renowned for their exceptional preservation of both flora and fauna. Encased in siderite nodules, fossils from this site often preserve extraordinary detail, making them among the most scientifically and historically important fossil assemblages in the world. What is Palaeoxyris prendeli? Palaeoxyris is the name given to fossilised shark egg capsules, once mistaken for plant material due to their unusual spiral shape. Later research identified these as the egg cases of Hybodont sharks, an extinct group that flourished during the Paleozoic and Mesozoic. The specific species Palaeoxyris prendeli is distinguished by its elongated spiral form with well-defined whorls. These egg cases are especially significant because they provide direct evidence of shark reproductive biology during the Carboniferous, giving rare insight into the life history of ancient vertebrates. Morphological Features This specimen exhibits classic features of Palaeoxyris prendeli: Shape: Elongated capsule with distinct spiral ridges. Surface Texture: Fine helical grooves along the outer case. Preservation: Encased within a siderite nodule, providing excellent protection and definition. These morphological traits make Palaeoxyris fossils unmistakable and scientifically valuable, as they directly connect to ancient shark reproduction. Paleoenvironment and Depositional Setting During the Carboniferous, Illinois lay in equatorial regions dominated by extensive swamps and shallow deltaic environments. These environments created ideal conditions for both the flourishing of early sharks and the preservation of their reproductive material. The rapid burial of egg capsules within sediments led to their preservation in siderite nodules, protecting them for over 300 million years. The discovery of shark egg cases alongside plant fossils, insects, and other fauna paints a vivid picture of Carboniferous ecosystems, highlighting the biodiversity of these coal swamp habitats. Key Details Fossil Type: Shark egg case (Palaeoxyris prendeli) Age: Carboniferous (~307 million years old) Locality: Mazon Creek, Illinois, USA Preservation: Split siderite nodule with excellent detail Authenticity: 100% genuine specimen with Certificate of Authenticity Size: See photos with 1 cm scale cube for accurate dimensions Collectability and Scientific Value Fossils of Palaeoxyris are rare and highly sought after by both collectors and researchers. Unlike skeletal remains, these egg cases provide direct biological and ecological evidence, helping paleontologists understand the reproductive strategies of ancient sharks. This specimen from Mazon Creek is particularly prized because of the locality’s reputation for world-class preservation. It makes an outstanding addition to any fossil collection, a fascinating display specimen, and a scientifically significant piece of natural history. Owning this rare Mazon Creek Palaeoxyris prendeli shark egg case is an opportunity to hold in your hands a piece of prehistoric life that documents the early reproductive history of sharks in Carboniferous ecosystems.