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Genus of molluscs (fossil)
Sphenodiscus
Sphenodiscus lenticularis
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Mollusca
Class:
Cephalopoda
Subclass:
†
Ammonoidea
Order:
†
Ammonitida
Family:
†
Sphenodiscidae
Genus:
†
Sphenodiscus
Meek , 1871
Species
S. lobatus (Tuomey, 1854 [originally
Ammonites lobatus ])
S. lenticularis (
Owen , 1852 [originally Ammonites lenticularis ])
S. pleurisepta (Conrad, 1857 [originally Ammonites pleurisepta ])
S. brasiliensis Maury, 1930
S. binkhorsti Böhm, 1898
S. intermedius Böse, 1927
S. aberrans Böse, 1927
S. parahybensis Maury, 1930
S. prepleurisepta Böse, 1927
S. ubaghsi de Groussouvre, 1894
S. siva Kennedy & Henderson, 1992
Sphenodiscus is an extinct
genus of
acanthoceratacean
ammonite . The genus has been found from many continents and is thought to have had a large global distribution during the
Maastrichtian stage of the
Late Cretaceous . It was one of the last ammonoids to have evolved before the entire
subclass became extinct during the
Paleocene , which was directly after the
Cretaceous–Paleogene extinction event .
Distribution
Nacreous specimen
Fossils have been found throughout
North America from localities in
South Carolina ,
[1]
North Carolina ,
[2]
South Dakota ,
[3]
Maryland ,
[4]
New Jersey
[5] and
Mexico .
[6] There is also evidence of the genus being present from the island of
Trinidad , although the material found from here cannot be classified at the species level.
[7] Common species found in North America include S. lobatus , S. lenticularis , and S. pleurisepta . New species have been found from localities outside of North America such as S. binkhorsti from the
Maastricht Formation in the
Netherlands , S. siva from the
Valudavur Formation in
India and S. brasiliensis from the beds along the banks of the
Rio Gramame in
Brazil .
[8]
[9]
[10] Many specimens of S. lobatus have also been found from the
Nkporo Shale in
Nigeria .
Description
Suture pattern of Sphenodiscus
The shell of Sphenodiscus was streamlined and lateromedially compressed with overlapping whorls and a small umbilicus. The ventral edge of the shell tends to be sharply angled. The outer surface is generally smooth in fossil specimens, although certain species at different stages of ontogenic development may possess many small tubercles along their surfaces.
[11] Sphenodiscus had a complex suture pattern with many small branching lobes and saddles.
References
^ Allmon, W. D.; Knight, J. L. (1993). "Paleoecological significance of a turritelline gastropod-dominated assemblage in the Cretaceous of South Carolina". Journal of Paleontology . 67 (3): 355–360.
Bibcode :
1993JPal...67..355A .
doi :
10.1017/S0022336000036830 .
S2CID
127799044 .
^
"Online Collections | North Carolina Museum of Natural Sciences" . collections.naturalsciences.org . Archived from
the original on 2016-03-16. Retrieved 2016-05-16 .
^ Turekian, K. K.; Armstrong, R. L. (1961). "Chemical and mineralogical composition of fossil molluscan shells from the Fox Hills Formation, South Dakota". GSA Bulletin . 72 (12): 1817–1828.
Bibcode :
1961GSAB...72.1817T .
doi :
10.1130/0016-7606(1961)72[1817:CAMCOF]2.0.CO;2 .
^ Landman, N. H.; Johnson, R. O.; Edwards, L. E. (2004).
"Cephalopods from the Cretaceous/Tertiary boundary interval on the Atlantic Coastal Plain, with a description of the highest ammonite zones in North America. Part 1, Maryland and North Carolina" . American Museum Novitates (3454): 1–64.
doi :
10.1206/0003-0082(2004)454<0001:CFTTBI>2.0.CO;2 .
hdl :
2246/2819 .
S2CID
54913756 .
^ Kennedy, W. J.; Cobban, W. A. (1996). "Maastrichtian Ammonites from the Hornerstown Formation in New Jersey". Journal of Paleontology . 70 (5): 798–804.
Bibcode :
1996JPal...70..798K .
doi :
10.1017/S0022336000023842 .
JSTOR
1306482 .
S2CID
128587701 .
^ Böse, E. (1927). "Cretaceous ammonites from Texas and northern Mexico". University of Texas Bulletin . 2748 (2): 143–357.
^ Rutsch, R. F. (1939). "Upper Cretaceous Fossils from Trinidad, B. W. I". Journal of Paleontology . 13 (5): 521–523.
^ Kennedy, W. J. (1986).
"The Campanian-Maastrichtian ammonite sequence in the environs of Maastricht (Limburg, the Netherlands), Limburg and Liège provinces (Belgium)" . Newsletters on Stratigraphy . 16 (3): 149–168.
doi :
10.1127/nos/16/1986/149 . Archived from
the original on 2012-03-12. Retrieved 2010-10-16 .
^ Hancock, J. M. (1967). "Some Cretaceous-Tertiary marine faunal changes". Geological Society, London, Special Publications . 2 (1): 91–104.
Bibcode :
1967GSLSP...2...91H .
doi :
10.1144/GSL.SP.1967.002.01.10 .
S2CID
140190427 .
^ Maury, C. J. (1930). "O Cretaceo da Parahyba do Norte". Serviço Geologico e Mineralogico do Brasil Monographia . 8 : 1–305.
^ Bandel, K.; Landman, N. H.; Waage, K. M. (1982). "Micro-Ornament on Early Whorls of Mesozoic Ammonites: Implications for Early Ontogeny". Journal of Paleontology . 56 (2): 386–391.
JSTOR
1304464 .
External links