Rare Fossil Ammonite Dichotomoceras antecedens Jurassic Oxfordian Tulear Madagascar | Authentic Fossil

Description

This listing features a rare and striking fossil of Dichotomoceras antecedens, an unusual and scientifically important ammonite species from the Oxfordian stage of the Late Jurassic period. The specimen comes from the world-renowned fossil-rich beds near Tulear, Madagascar, celebrated for their excellent preservation of Jurassic marine fauna.

Geological Context:

• Fossil Type: Ammonite (Extinct marine mollusc, relative of squid and cuttlefish)
• Species: Dichotomoceras antecedens (identified by Collignon, 1958)
• Order: Ammonitida
• Superfamily: Perisphinctoidea
• Family: Aspidoceratidae
• Geological Stage: Oxfordian (c. 163.5 to 157.3 million years ago)
• Formation: Oxfordian marine limestones of southern Madagascar
• Depositional Environment: Shallow tropical marine shelf with fine carbonate sedimentation

Dichotomoceras is a genus known for its intricate ribbing and robust shell architecture, and D. antecedens is one of the earliest species in this lineage. These ammonites are highly desirable due to their rarity and role in evolutionary and biostratigraphic research.

Morphology & Notable Features:

• Planispiral and evolute shell with broad, open whorls
• Strong, dichotomously branching ribs crossing the flanks
• Rounded to subangular venter, often without keel
• Pronounced tuberculation along the flanks in later whorls
• Complex suture lines, typical of the Aspidoceratid family

Biozone Association: Dichotomoceras antecedens appears in the Lower Oxfordian zones, particularly linked to early Perisphinctoid assemblages in southern hemisphere Jurassic strata.

Specimen Details:

• Origin: Tulear Region, Madagascar
• Age: Oxfordian Stage, Late Jurassic (~160 million years old)
• Scale: Scale rule square/cube = 1cm. Please see photographs for accurate dimensions
• Condition: Carefully selected for completeness, clarity, and natural preservation
• Photo: The fossil shown is the exact specimen you will receive

Certification & Authenticity: All of our fossils are 100% genuine specimens and come with a Certificate of Authenticity. Each item is individually chosen for its educational, scientific, and visual value.

This rare Dichotomoceras antecedens ammonite represents a remarkable glimpse into Madagascar’s Jurassic seas. Ideal for serious fossil collectors, educators, or natural history lovers, this is a premium example of paleontological heritage from one of the world’s most significant fossil localities.