Description
Myloceras ammonoides (Millstone Horn Ammonite) is an extinct marine cephalopod from Australia’s Cretaceous inland seas. This species is dated to approximately 100–113 million years ago (Cretaceous) and is known from the Allaru Formation, Currane Station, Ilfracombe, Central West Queensland. The specimen represents a nektonic mollusc that swam within the warm shallow waters of the Eromanga Sea system.
Originally described by Dr Frederick W Whitehouse in 1926, Myloceras ammonoides was based on fossil shells discovered near Port Douglas and Dalhousie Springs. It belongs to the heteromorph ammonites, an unusual group distinguished by shells that became partially uncoiled rather than retaining the tightly coiled form typical of most ammonites. In M. ammonoides, the shell commonly developed a straight shaft extending beyond the shell opening, terminating in a recurved spiral tip.
The genus name Myloceras combines the Greek mylos (millstone) and keras (horn), referring to the distinctive combination of coiled and extended shell forms. Myloceras is closely related to the heteromorph ammonite Labeceras, and fossils of both genera are often recovered from the same deposits. Some researchers have suggested the two may represent male and female forms of a single lineage, with Myloceras interpreted as the larger-shelled macroconch form. At present, both genera continue to be recognised separately.
Modern nautiluses are distant living relatives of ammonites and provide insight into the buoyant, jet-propelled lifestyle these animals likely employed. Unlike modern nautiluses, ammonites such as Myloceras possessed far more varied shell shapes, reflecting a wide range of ecological adaptations in ancient seas.
Each specimen is carefully prepared and represents a unique fossil with natural variation in preservation and completeness.
Key features
- Authentic fossil specimen
- Taxon: Myloceras ammonoides (ammonite, Mollusca, Cephalopoda)
- Age: 100–113 million years (Cretaceous)
- Origin: Allaru Formation, Eromanga Sea system, Queensland, Australia
- Museum-prepared specimen
- Natural variation in preservation
Note
As a natural fossil, variations in colour, texture and completeness are expected and add to the uniqueness of each specimen. All fossils sold by the Museum are common and widely represented and are not of scientific research value.
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