Allocrioceras Cf annulatum
Phylum Mollusca, Class Cephalopoda, Order Ammonitida, Family Anisoceratidae
Geological Time: Middle Cretaceous, Cenomanian Stage (~95 million years ago)
Size (25.4 mm = 1 inch): 31 mm across with juveniles 10 mm- 12 mm across on a 100 mm by 130 mm matrix
Fossil Site: Lebanese Lagerstätte, Hajula, Lebanon
Fossil Code: RS137
Price: Sold
 Description:
Coming from the Cretaceous of Lebanon this is an ammonite known
as Allocrioceras. This is one of the heteromorphic ammonites.
While most ammonites have spiral shells that retain the same
shape throughout growth (homomorph), a major group of ammonites,
the Ancyloceratina, emerged during the Late Jurassic that had
uncoiled shells, and were called heteromorph ammonites (different-shaped).
While little is known of their mode of life, their uncoiled shells
would have precluded fast swimming. They may have wobbled their
way through the water column with out-splayed tentacles, sweeping
whatever came within their reach into their hungry mouths. As
all ammonites, these went extinct at the end of the Cretaceous.
Note the three juvenile examples preserved here. The upper one
has an aptychus, or jaw, preserved within the shell, an uncommon
occurrence. There is a partial fish coprolite and a faint brittlestar
also preserved, making for an exceptional association piece. |
