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Cameroceras

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Cameroceras
Temporal range: Ordovician
Partial internal mold of C. inaequabile, Upper Ordovician of northern Kentucky
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Nautiloidea
Order: †Endocerida
Family: †Endoceratidae
Genus: †Cameroceras
Conrad, 1842
Type species
†Cameroceras trentonense
Conrad, 1842
Species

See text.

Cameroceras ("chambered horn") is an extinct genus of endocerid cephalopod which lived in equatorial oceans during the entire Ordovician period. Like other endocerids, it was an orthocone, meaning that its shell was fairly straight and pointed. It was particularly abundant and widespread in the Late Ordovician, inhabiting the shallow tropical seas in and around Laurentia, Baltica and Siberia (equivalent to modern North America, Europe, and Asia).[1]

Cameroceras exhibited a broad range of sizes, and some species were fairly large by extinct cephalopod standards. One species, C. turrisoides from the Boda Limestone of Sweden,[2] is estimated to have shell around 2 metres (6.6 ft) in length,[3] while that of C. rowenaense was about 70 centimetres (2.3 ft).[1] Some books and older scientific papers previously treated Cameroceras as the absolute largest nautiloid-grade cephalopod, with a shell length reaching 5.7 metres (19 ft)[4][5] or even 9.14 metres (30.0 ft).[6][4][1] More recent studies have indicated that the largest orthocone fossils do not belong to the genus Cameroceras, but rather Endoceras giganteum. Moreover, the maximum length estimate is based on a highly doubtful field observation.[5] Cameroceras and Endoceras are indistinguishable in most anatomical aspects, only differing in their shell texture.[7]

Description

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Cameroceras shown feeding on an Aphetoceras, while a quartet of Cyclostomiceras swim by.

Cameroceras is a cephalopod, the same group of molluscs that includes the octopuses, squids and cuttlefish. The only portion of the animal to fossilize is the shell (formally known as the conch). Like other orthoconic nautiloids, Cameroceras had a narrow conical shell with smooth, simple sutures dividing a series of septa (internal chambers). In cross-section, the shell may be perfectly circular or slightly depressed (elliptical, wider than tall).[7]

The position of the siphuncle varies, but in most species it runs close to the lower edge of the shell. In some species the siphuncle is voluminous, reaching a diameter equal to half of the shell diameter. The siphuncle is filled with stacked funnel-shaped concretions known as endocones, which have a simple conical form in Cameroceras.[7] A thin endosiphuncular tube passes through the apex of each endocone, in the lower part of the siphuncle. The surface of the siphuncle is supported by septal necks which are holochoanitic, meaning that they fully sheath the siphuncle and extend all the way between each septum. The main difference between Cameroceras and Endoceras is that Cameroceras lacks annulations (thin concentric rings) on the outer surface of the shell.[7]

From comparison with living cephalopods, particularly the shelled nautilus, some inferences about the biology of Cameroceras can be made. The head of the animal would have been soft muscular tissue situated at the opening of the shell, with the mantle (sheath-like body wall) lying within the shell for protection. Tentacles would have grown from the base of the head, and these tentacles would have been used to seize and manipulate prey. At the base of these tentacles within the buccal mass (analogous to the mouth) a hard keratinous beak would have bitten into the bodies of its prey, and is assumed to have been strong enough to breach the prey's exoskeleton or shell. Modern cephalopods beaks contain a radula, or 'toothed' tongue, which is used to rasp out soft tissue from within the prey's shell.

Classification

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Cameroceras has historically been utilized as a "wastebasket taxon" in which species of large orthoconic endocerids such as Endoceras, Vaginoceras, and Meniscoceras were originally placed. This poses difficulty for describing Cameroceras as a distinct genus. The type species Cameroceras trentonense was named by Conrad in 1842, based on fossils from the Trenton Limestone of western New York state.[8] The original specimen of C. trentonense is apparently lost, which complicates comparisons to other endocerids.[6]

Hall, who named and described Endoceras annulatum in 1847, recognized C. trentonense as a valid combination, but used Endoceras for other specimens of large endocerids from the Trenton Limestone. Sardeson (1925/1930) suggested that Cameroceras and Endoceras are potentially different growth stages of the same genus,[9][10] though other authors have doubted this perspective.[6]

For many historical studies, Cameroceras was considered to take precedence over Endoceras whenever the two refer to the same species, according to the principle of priority.[11][9][10][1] Cameroceras' vague early descriptions have led other authors to prefer Endoceras or other better-described genera when the nomenclature is in question.[6] Recent studies generally accept both Cameroceras and Endoceras as valid genera, even some species are in an unstable state between the two.[7][2][3][12]

Species

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Fossils assigned to Cameroceras have been found in North America, Asia, and Europe throughout the Ordovician, though most species occur in the Katian stage of the Late Ordovician. Reports of Cameroceras fossils from the Wenlock epoch of the Silurian are based on Rossicoceras hudsonicum,[13] an Ontarian endocerid species sometimes placed within Cameroceras.[7] Species which are currently referred to Cameroceras rather than to other endocerids include:

Species Author(s) Year Temporal range Notes & description
Cameroceras akpatokense[2] (Foerste & Cox) 1936 Upper Ordovician (late Katian) From Akpatok Island in Nunavut. Originally known as Endoceras akpatokense.[2]
Cameroceras alternatum[14] Flower 1968 Upper Ordovician ("Mohawkian") A very large species (diameter ~ 16.5 cm) based on a single fossil from the Black River Group of Quebec.[14]
Cameroceras coxi[2] (Foerste & Cox) 1936 Upper Ordovician (late Katian) From Akpatok Island in Nunavut. Originally known as Endoceras coxi.[2]
Cameroceras curvatum Ruedemann 1906 Lower Ordovician From Vermont.
Cameroceras hasta[2] (Eichwald) 1857 Upper Ordovician (late Katian) A widespread European species. Previously known as Endoceras hasta, Endoceras megastoma, or Rossicoceras pirguense.[2]
Cameroceras hennepini[11] Clarke 1897 Upper Ordovician ("Shermanian") A large species (diameter ~ 10 cm, length ~ 4 ft) from the Galena Limestone of Minnesota.[9]
Cameroceras huzzohense[15] Ulrich & Foerste 1930 Lower Ordovician A common small species (diameter ~ 2.7 cm) from the Gasconade Formation of Missouri.[15]
Cameroceras inaequabile[16] (Miller) 1882 Upper Ordovician ("Richmondian") A fairly uncommon but widespread American species found throughout "Richmondian" strata in Ohio,[17][18] Kentucky, Indiana,[17] and Illinois.[16] Originally known as Endoceras inaequabile.[16]
Cameroceras inopinatum[19] Stauffer 1937 Lower Ordovician A tiny species (diameter ~ 1 cm) from the Shakopee Dolomite of Minnesota.[19]
Cameroceras motsognir[12] Kröger & Aubrechtová 2019 Upper Ordovician (late Sandian – Katian?) A small species (diameter ~ 4.3 cm) with a slightly curved shell. From the Kullsberg Limestone Formation of Sweden.[12]
Cameroceras regulus[2] (Eichwald) 1860 Upper Ordovician (late Katian) A medium-sized European species (diameter ~ 7.2 cm) found in Estonia and Sweden.[2] Originally known as Endoceras regulus.
Cameroceras rowenaense[1] Frey 1995 Upper Ordovician ("Maysvillian") A medium-sized species (diameter ~ 8 cm, length > 70 cm) from the Leipers Limestone of Kentucky.[1]
Cameroceras stillwaterense[20] Stauffer 1937 Lower Ordovician A small species (diameter ~ 1.5 cm, length > 10 cm) from the Shakopee Dolomite of Minnesota.[20]
Cameroceras styliforme Grabau 1922 Lower Ordovician From Hubei, China.
Cameroceras trentonense (type species) Conrad 1842 Upper Ordovician (late Katian) The type species, from the Trenton Limestone of New York and possibly the Lexington Limestone of Kentucky.[1]
Cameroceras turrisoides[2] Kröger 2013 Upper Ordovician (mid-late Katian) A very large species (maximum diameter ~ 17 cm, total length ~ 2 m)[3] from the Boda Limestone of Sweden and the Bardahessaigh Formation of Ireland.[2]
Cameroceras vertebrale (Eichwald) 1860 Middle Ordovician
Cameroceras windriverense[2] (Miller) 1932 Upper Ordovician (late Katian) From the Lander Sandstone. Originally known as Endoceras windriverense.[2]

See also

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References

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  1. ^ a b c d e f g Frey, R.C. 1995. "Middle and Upper Ordovician nautiloid cephalopods of the Cincinnati Arch region of Kentucky, Indiana, and Ohio" (PDF). Archived (PDF) from the original on 2017-05-01. Retrieved 2023-10-25. U.S. Geological Survey, p.73
  2. ^ a b c d e f g h i j k l m n Kröger, Björn (2013-03-27). "The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden". European Journal of Taxonomy (41): 1–110. doi:10.5852/ejt.2013.41. ISSN 2118-9773. Archived from the original on 2022-10-02. Retrieved 2023-10-25.
  3. ^ a b c Kröger, Björn; Ebbestad, Jan Ove R. (2014). "Palaeoecology and palaeogeography of Late Ordovician (Katian–Hirnantian) cephalopods of the Boda Limestone, Siljan district, Sweden". Lethaia. 47 (1): 15–30. Bibcode:2014Letha..47...15K. doi:10.1111/let.12034. ISSN 0024-1164. Archived from the original on 2023-11-10. Retrieved 2023-10-13.
  4. ^ a b Teichert, Curt; Kummel, Bernhard (20 December 1960). "Size of Endocerid Cephalopods". Breviora. 128: 1–7. Archived from the original on 8 April 2017. Retrieved 25 October 2023.
  5. ^ a b Klug, C.; De Baets, K.; Kröger, B.; Bell, M.A.; Korn, D.; Payne, J.L. (2015). "Normal giants? Temporal and latitudinal shifts of Palaeozoic marine invertebrate gigantism and global change". Lethaia. 48 (2): 267–288. Bibcode:2015Letha..48..267K. doi:10.1111/let.12104.
  6. ^ a b c d Flower, Rousseau H. (1955). "Status of Endoceroid Classification". Journal of Paleontology. 29 (3): 329–371. ISSN 0022-3360. JSTOR 1300321.
  7. ^ a b c d e f Teichert, Curt (1964). "Endoceratoidea". In Moore, Raymond C. (ed.). Part K, Mollusca 3. Cephalopoda General Features, Endoceratoidea, Actinoceratoidea, Nautiloidea, & Bactritoidea. Treatise on Invertebrate Paleontology. Lawrence, Kansas: Geological Society of America; University of Kansas. pp. 160–189. Archived from the original on 2023-05-31. Retrieved 2023-10-26.
  8. ^ Jody, I. (2011). Cameroceras. Cred Press. ISBN 9786136780764.
  9. ^ a b c Sardesson, F. W. (1925). "Primitive cephalopods from Minnesota". The Pan-American Geologist. 43: 185–204. Archived from the original on 2023-11-10. Retrieved 2023-10-29.
  10. ^ a b Sardesson, F. W. (1930). "Cameroceras and its allies". The Pan-American Geologist. 53: 175–182.
  11. ^ a b Clarke, John M. (1897). "IX. The Lower Silurian Cephalopoda of Minnesota". In Ulrich, Edward O.; Clarke, John M.; Scofield, Wilbur H.; Winchell, Newton H. (eds.). Geology of Minnesota. Vol. III, Part II, of the Final Report. Paleontology. Minneapolis: Harrison & Smith. pp. 761–812. Archived from the original on 2023-11-10. Retrieved 2023-10-29.
  12. ^ a b c Kröger, Björn; Aubrechtová, Martina (2019). "The cephalopods of the Kullsberg Limestone Formation, Upper Ordovician, central Sweden and the effects of reef diversification on cephalopod diversity". Journal of Systematic Palaeontology. 17 (12): 961–995. Bibcode:2019JSPal..17..961K. doi:10.1080/14772019.2018.1491899. hdl:10138/308819. S2CID 92845570.
  13. ^ Evans, David H.; Holland, Charles Hepworth (1995). "The nautiloid cephalopod Order Endocerida in the Silurian". Paläontologische Zeitschrift. 69 (3–4): 343–352. Bibcode:1995PalZ...69..343E. doi:10.1007/BF02987799. ISSN 0031-0220. Archived from the original on 2023-11-10. Retrieved 2023-10-25.
  14. ^ a b Flower, Rousseau H. (1968). "An Endoceroid from the Mowhawkian of Quebec" (PDF). New Mexico Bureau of Mines and Mineral Resources Memoir. 21: 9. doi:10.58799/M-21. Archived (PDF) from the original on 2023-10-19. Retrieved 2023-10-25.
  15. ^ a b Ulrich, E.O.; Foerste, Aug F.; Bridge, J. "Chapter VI. Systematic Paleontology" (PDF). In Bridge, Josiah (ed.). Geology of the Eminence and Cardareva Quadrangles. Rolla: Missouri Bureau of Geology and Mines. pp. 186–222. Archived (PDF) from the original on 2023-10-25. Retrieved 2023-10-25.
  16. ^ a b c Miller, S. A. (1882). "Description of ten new species of fossils". Journal of the Cincinnati Society of Natural History. 5: 79–88. Archived from the original on 2018-02-20. Retrieved 2023-10-25.
  17. ^ a b Frey, Robert C. (1987). "The paleoecology of a Late Ordovician shale unit from southwest Ohio and southeastern Indiana". Journal of Paleontology. 61 (2): 242–267. Bibcode:1987JPal...61..242F. doi:10.1017/S0022336000028444. ISSN 0022-3360. Archived from the original on 2023-11-10. Retrieved 2023-10-25.
  18. ^ Frey, Robert C. (1989). "Paleoecology of a well-preserved nautiloid assemblage from a Late Ordovician shale unit, southwestern Ohio". Journal of Paleontology. 63 (5): 604–620. Bibcode:1989JPal...63..604F. doi:10.1017/S0022336000041238. ISSN 0022-3360. Archived from the original on 2023-11-10. Retrieved 2023-10-25.
  19. ^ a b Stauffer, Clinton R. (1937). "A Diminutive Fauna from the Shakopee Dolomite (Ordovician) at Cannon Falls, Minnesota". Journal of Paleontology. 11 (1): 55–60. ISSN 0022-3360. JSTOR 1298311.
  20. ^ a b Stauffer, Clinton R. (1937). "Mollusca from the Shakopee Dolomite (Ordovician) at Stillwater, Minnesota". Journal of Paleontology. 11 (1): 61–68. ISSN 0022-3360. JSTOR 1298312.

Further reading

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