Description
Genuine Sinucites hispanicus Ammonite Fossil
This genuine ammonite fossil is identified as Sinucites hispanicus and originates from Arroyo del Acebrón, Peña Aguilera, in the province of Toledo, Spain. It dates from the Lower Pliensbachian subdivision of the Lower Jurassic and represents an extinct marine cephalopod that inhabited European seas approximately 190 million years ago.
This specimen combines an identifiable ammonite species with detailed locality and geological-age information, giving it strong palaeontological and collecting interest. The fossil has been carefully selected for its natural form, preservation and documented Spanish provenance.
The listing photographs show the exact specimen you will receive. Its individual shell shape, ornamentation, matrix, colour and state of preservation can therefore be examined before purchase. Full sizing and scale information are provided in the photographs.
Species Identification and Scientific Classification
Sinucites hispanicus belongs to the ammonites, an extinct group of externally shelled marine molluscs that flourished throughout much of the Mesozoic Era.
Its broad scientific classification includes:
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Ammonitida
Genus: Sinucites
Species: Sinucites hispanicus
Ammonites were related to living squid, cuttlefish, octopuses and nautiluses. Although the coiled shell resembles that of the modern chambered nautilus, ammonites formed a separate evolutionary lineage distinguished by their shell ornamentation and increasingly complex internal suture patterns.
The species name hispanicus reflects its association with Spain. Fossils from recorded Iberian localities are especially valuable because they contribute to the understanding of Early Jurassic marine faunas across the western Tethyan region.
Distinctive Ammonite Morphology
The shell of Sinucites hispanicus developed as a planispiral coil, with successive whorls growing around one another within approximately the same plane. Depending on the individual growth stage, the earlier whorls may remain partly visible around the central umbilicus.
The shell ornament may include radial ribs extending from the inner whorl towards the venter, or outer edge of the shell. Rib strength, curvature and spacing can change as the ammonite grows, producing subtle differences between juvenile and mature portions.
The precise morphology visible on this specimen depends upon its natural preservation. It may retain external shell detail, mineral-replaced shell material, a sediment-filled internal mould or a combination of these forms.
Any worn ribs, incomplete areas, matrix deposits or variations in surface texture are authentic features of the fossil and document the geological processes that affected the shell after burial.
Chambered Shell and Buoyancy
Internally, the ammonite shell was divided by curved partitions called septa. These formed a sequence of chambers connected by a narrow tube known as the siphuncle.
The living animal occupied the final and largest body chamber. As it grew, it moved forwards and added new shell material at the aperture, sealing the older part of the shell behind it with another septum.
The abandoned chambers helped control buoyancy. By regulating the balance of liquid and gas within them, the ammonite could maintain its position in the water column.
The lines formed where the septa met the outer shell wall are known as sutures. These patterns are important in ammonite classification and became highly intricate in many Jurassic ammonoid groups.
The soft-bodied animal would have extended its head, eyes and muscular arms from the shell opening. It probably fed on small marine organisms and organic material within the surrounding sea.
Lower Pliensbachian Geological Age
This fossil dates from the Lower Pliensbachian, the earlier portion of the Pliensbachian Stage of the Lower Jurassic. The Pliensbachian followed the Sinemurian and preceded the Toarcian.
During this interval, ammonites diversified extensively and became important components of marine ecosystems. Their changing shell forms and ornamentation provide geologists with a detailed record of biological evolution through Jurassic time.
Ammonites are especially valuable index fossils because many species existed for comparatively restricted intervals while being distributed across broad marine regions. Their occurrence allows palaeontologists to divide sedimentary sequences into biozones and compare similarly aged rocks from separate localities.
The recorded Lower Pliensbachian age therefore gives this fossil considerably more scientific context than a specimen described only as a general Jurassic ammonite.
Early Jurassic Marine Environment of Spain
During the Pliensbachian, parts of the Iberian Peninsula were covered by warm seas linked to the western Tethys Ocean. Marine basins and shallow shelf environments extended across regions that are now inland areas of central Spain.
These waters supported ammonites, belemnites, nautiloids, bivalves, gastropods, brachiopods, crustaceans, fish and marine reptiles. Microscopic plankton formed an important part of the food web and contributed organic and calcareous material to the seabed.
Fine mud, carbonate sediment and shell debris accumulated over time. Changes in water depth, current strength, sediment supply and oxygen conditions produced different layers of limestone, marl and clay.
Sinucites hispanicus formed part of this Early Jurassic marine ecosystem. Its chambered shell allowed the animal to live within the water column above the seabed, alongside numerous other cephalopods and marine invertebrates.
Arroyo del Acebrón and Peña Aguilera Provenance
Arroyo del Acebrón, near Peña Aguilera in Toledo, lies within a region containing sedimentary rocks that preserve evidence of ancient marine conditions. Fossils from precisely recorded localities such as this are particularly desirable because their geographical and geological context has been retained.
The Toledo provenance connects this specimen with the Jurassic history of the Iberian Peninsula and provides useful information for comparison with ammonite faunas from other parts of Spain and western Europe.
A specimen retaining its species name, stage and locality offers significantly greater scientific and educational value than an ammonite sold without provenance.
Fossilisation and Natural Preservation
After the ammonite died, its shell descended to the seabed. Currents, scavengers and sediment movement may have affected the shell before it was fully buried.
Fine sediment entered the empty chambers and accumulated around the exterior. As additional layers built up, pressure compacted the sediment and gradually transformed it into rock.
The original ammonite shell was composed mainly of aragonite, a form of calcium carbonate that can dissolve or alter during fossilisation. Mineral-rich groundwater may have replaced or recrystallised the shell, while sediment hardened inside the chambers to form a natural internal mould.
Natural fractures, incomplete edges, worn ornamentation, matrix, mineral markings and variations in colour are genuine consequences of burial and geological alteration. These individual characteristics form part of the specimen’s history and ensure that every fossil is unique.
Actual Specimen and Certificate of Authenticity
This is a genuine fossil specimen and not a cast, replica or artificial reproduction. The listing photographs show the exact Sinucites hispanicus ammonite that will be supplied, allowing you to inspect its natural shell profile, ornamentation, matrix, colour and preservation before purchasing.
Full sizing is shown in the listing photographs.
The fossil includes a generic Certificate of Authenticity card carrying a lifetime guarantee. Its identifiable species, Lower Pliensbachian age and documented Arroyo del Acebrón provenance make it an excellent addition to a Jurassic ammonite collection, Spanish fossil display, natural-history cabinet or educational geological collection.
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