Order

Orthocerida Kuhn, 1940

Taxon description

Kröger & Isakar, 2006

Emended diagnosis. Straight or curved with smooth orelaborately ornamented shells, with central or subcentral nar-row siphuncle siphuncle that may be slightly expanded be-tween the chambers. Siphuncular necks achoanitic, subortho-choanitic or orthochoanitic. Apex spherical, bowl-shaped orblunt, invariably without cicatrix

Selection of related publications

Kröger, B. 2025. The Lyckholm acme of cephalopods – Review of the late Katian (Vormsi–Pirgu regional stages) Ordovician cephalopods of Estonia. European Journal of Taxonomy 978, 1-168. DOI:10.5852/ejt.2025.978.2801

Kröger, B., Aubrechtová, M. 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. DOI:10.1080/14772019.2018.1491899

Pohle, A., Klug, C., Toom, U., Kröger, B. 2019. Conch structures, soft-tissue imprints and taphonomy of the Middle Ordovician cephalopod Tragoceras falcatum from Estonia. Fossil Imprint 75, 1, 70-78. DOI:10.2478/if-2019-0006

Kröger, B., Aubrechtová, M. 2018. Cephalopods from reef limestone of the Vasalemma Formation, northern Estonia (latest Sandbian, Upper Ordovician) and the establishment of a local warm-water fauna. Journal of Systematic Palaeontology 16, 10, 799-839. DOI:10.1080/14772019.2017.1347212

Kröger, B. 2013. The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden. European Journal of Taxonomy 41, 41, 1-110. DOI:10.5852/ejt.2013.41

Kröger, B., Ebbestad, J. O. R., Högström, A. E. S., Frisk, Ǻ. M. 2011. Mass concentration of Hirnantian cephalopods from the Siljan District, Sweden; taxonomy, palaeoecology and palaeobiogeographic relationships. Fossil Record 14, 1, 35-53. DOI:10.1002/mmng.201000014

Kröger, B. 2007. Concentrations of juvenile and small adult cephalopods in the Hirnantian cherts (Late Ordovician) of Porkuni, Estonia. Acta Palaeontologica Polonica 52, 3, 591–608.

Kröger, B., Isakar, M. 2006. Revision of annulated orthoceridan cephalopods of the Baltoscandic Ordovician. Fossil Record 9, 1, 137-163. DOI:10.1002/mmng.200600005

Kröger, B. 2004. Revision of Middle Ordovician orthoceratacean nautiloids from Baltoscandia. Acta Palaeontologica Polonica 49, 1, 57-74.

Mutvei, H. 2002. Connecting ring structure and its significance for classification of the orthoceratid cephalopods. Acta Palaeontologica Polonica 47, 1, 157-168.

King, A. H. 1999. A Review of Volkhovian and Kundan (Arenig-Llanvirn) Nautiloids from Sweden. Advancing Research on Living and Fossil Cephalopods, pp. 137-159. Springer. DOI:10.1007/978-1-4615-4837-9_11

Kiselev, G. N. 1991. Revizia pozdneordovikskikh i siluriskikh tsefalopod Pribaltiki iz kollektsii E. I. Eichwalda [Ревизия позднеордовикских и силурийских цефалопод прибалтики из коллекции Е. И. Эйхвальда]. Bulletin of the Moscow Society of Naturalists. Geological series 66, 4, 85-101.

Rõõmusoks, A. 1970. Stratigraphy of the Viruan Series (Middle Ordovician) in Northern Estonia, I. pp. 1-346. Valgus.

Saladžius, V. J. 1966. Mollusk fauna of the Silurian deposits of the south of the East Baltic territory. Palaeontology and stratigraphy of the Baltic and the Byelorussia. Number I (VI), pp. 31-73. Mintis.

Balashov, E. A. 1959. Nekotorye novye vidy nautiloidej ordovika, silura i devona SSSR. Materialy k "Osnovam paleontologii", Bypusk 3, pp. 37-46. Paleontologicheskii Institut Akademii Nauk SSSR.

Sweet, W. C. 1958. The Middle Ordovician of the Oslo Region, Norway: 10. Nautiloid Cephalopods. Norsk Geologisk Tidsskrift 38, 1, 1-178.

Balashov, Z. G. 1956. O sistematicheskom polozhenii i stratigraficheskom znachenii roda Orthoceras. Ežegodnik Vsesoûznogo Paleontologičeskogo Obŝestva XV, 223-247.

Stumbur, H. A. 1956. On the nautiloids of Kohila Subseries (Upper Ordovician of East Baltic). Tartu Riikliku Ülikooli Toimetised 42, 176-185.

Balashov, Z. G. 1955. Semejstvo Cochlioceratidae nom. nov.. Voprosy paleontologii II, 55-60.

Stumbur, H. 1955. Eesti NSV ülem-ordoviitsiumi nautiloiididest [Diplomitöö. Juhendaja: A. Rõõmusoks]. pp. 1-159.

Alichova, T. N., Balashova, E. A., Balashov, Z. G. 1954. Polevoj atlas harakternyh kompleksov fauny otloženij ordovika i gotlandiâ ûžnoj časti Litovskoj SSR. pp. 1-80. Nedra.

Strand, T. 1934. The Upper Ordovician Cephalopods of the Oslo Area. Norsk Geologisk Tidsskrift 14, 1-117.

Teichert, C. 1930. Die Cephalopoden-Fauna der Lyckholm-Stufe des Ostbaltikums. Paläontologische Zeitschrift 12, 3/4, 264-312. DOI:10.1007/BF03044452

Öpik, A. 1927. Die Inseln Odensholm und Rogö. Ein Beitrag zur Geologia von NW-Estland. Tartu Ülikooli Geoloogia Instituudi Toimetused 9, 1-69.

Foord, A. H. 1887. On “Orthoceras (Endoceras) duplex” Wahlenberg et auct., with descriptions of three new species of Endoceras from the Ordovician of Sweden and Russia contained in the British Museum (Natural History). Annals and Magazine of Natural History 5, 20, 393–403.

Eichwald, E. 1860. Lethaea Rossica ou Paléontologie de la Russie. Premier volume. Ancienne Période en deux sections. pp. XIX+1–1657. E. Schweizerbart. DOI:10.5962/bhl.title.52391

Eichwald, E. 1857. Beitrag zur geographischen Verbreitung der fossilen Thiere Russlands. Alte Periode. (Fortsetzung. S. Bulletin 1856. N 4. pag. 555.). Klasse der Cephalopoden. Bulletin of the Moscow Society of Naturalists. Geological series 30, I, 192-219.

Schlotheim, E. F. von 1820. Die Petrefactenkunde auf ihrem jetzingen Standpuncte durch die Beschreibung seiner Sammlung versteinerter und fossiler Überreste des Thier-und Pfanzenreichs der Vorwelt erläuteri. pp. Ixii+1-436. Becker'sche Buchhandlung.

List of species

1. Allumettoceras mjoesense Sweet, 1958 | Darriwilian

2. Archigeisonoceras elegatulum Chen, 1984

3. Archigeisonoceras folkeslundense Kröger, 2004 | Lasnamägi Stage

4. Archigeisonoceras picus Kröger, 2004 | Volkhov Stage

5. Archigeisonoceras repplingense Kröger, 2004 | Volkhov Stage

6. Arionoceras lotskirkense Kröger, 2004 | Aseri Stage→Lasnamägi Stage

7. Balticoceras discors (Eichwald, 1857) | Rakvere Stage

8. Choanoceras mutabile Lindström, 1890 | Wenlock

9. Clothoceras thornquisti Kröger et Aubrechtová, 2019 | Katian→Sandbian

10. Cochlioceras angustiseptatum Balashov, 1955 | Aseri Stage→Uhaku Stage

11. Cochlioceras avus Eichwald, 1860 | Kunda Stage

12. Coralloceras lithuanica Saladzhius, 1966 | Ludlow

13. Ctenoceras schmidti Noetling, 1884 | Aseri Stage→Lasnamägi Stage

14. Ctenoceras sweeti Kröger et Isakar, 2006 | Lasnamägi Stage

15. Dawsonoceras annulatum (Sowerby, 1816) | Wenlock

16. Dawsonoceras barrandei Horny, 1956 | Wenlock

17. Dawsonoceras fenestratum (Eichwald, 1860) | Porkuni Stage

18. Dawsonoceras funiforme (Angelin, 1880)

19. Dawsonoceras gregarium Kröger, Ebbestad, Högström et Frisk, 2011 | Hirnantian

20. Dawsonoceras obsoletum (Barrande, 1874) | Paadla Stage→Ohesaare Stage

Classification

Organism group	Biota
Kingdom	Animalia
Phylum	Mollusca
Class	Cephalopoda
Subclass	Orthoceratia
Order	Astroviida
	Bajkalocerida
	Dissidoceratida
	Endoceratida
	Orthocerida
Suborder	Orthoceratina
Family	Baltoceratidae
	Choanoceratidae
	Kionoceratidae
	Stereoplasmoceratidae
Genus	Tripteroceras
Order	Pseudorthocerida
	Rioceratida