Edited by DPS Ammonite
Sub Period: None
International Age: Turonian
Eagle Ford Group
Arcadia Park Formation
Acquired by: Field Collection
Length: 66 mm
Width: 45 mm
Thickness: 18 mm
Post Oak Creek in Sherman
Here are interior and exterior views of both valves of the Cretaceous oyster, Cameleolopha bellaplicata, collected in Post Oak Creek in Sherman, Texas, The specimen is more oval and elongated that most of the members of its species. The calcite valves with a trace of interior aragonite, mother of pearl, are covered in yellowish calcite cemented sandstone. The larger valve has the remnants of an attached ramose bryozoan that grew on the shell since the muddy Arcadia Park Formation did not provide a great hard ground to grow on. An unidentified domed colonial stone coral species also grow on the oysters in the area.
The oysters are found in the upper part of the Arcadia Park Formation that contains a yellowish calcareous sandstone that is rich in small bivalves, shark teeth and other vertebrates. Similar mostly thin-bedded, yellowish and calcareous sandstones occur throughout north Texas and may be related to the thicker Bells Sandstone in eastern Grayson County.
See this best reference: Hook, S. C. & Cobban, W. A. 2011. The Late Cretaceous oyster Cameleolopha bellaplicata (Shumard1860), guide fossil to middle Turonian strata in New Mexico. New Mexico Geology. 33: 67-95.
Hook points out that Cameleolopha bellaplicata was "initially Ostrea, then Lopha, Alectryonia, and Nicaisolopha, and, now, Cameleolopha."
Hook describes the oyster as follows:
"Cameleolopha bellaplicata (Shumard 1860) is a medium-sized, plano-convex oyster with 8–27 generally simple plicae (ribs) that radiate from the beak. Secondary ornamentation consists of concentric lamellae that intersect the ribs. The general absence of attachment scars on preserved left valves indicates the species lived unattached as adults on the sea floor. Its left valve is larger and more convex than that of C. lugubris, giving it a more robust appearance and making it better suited to higher-energy, nearshore environments. The type specimens of C. bellaplicata came from the upper Eagle Ford Shale of Grayson County, Texas..."
For additional information on the oyster see:
Shumard, B. F., 1860. Descriptions of new Cretaceous fossils from Texas: Transactions of the Academy of Science of St. Louis, v. 1, pp. 590–610.
Vyalov, O. S., 1936. Sur la classification des huîtres: URSS Academy of Sciences, Comptes rendus (Doklady), new series, v. 4 (13), no. 1 (105), pp. 17–20 (after August 1).
Edited by DPS Ammonite