Olcostephaninae

Olcostephanus densicostatus, from ammonites.net.

Belongs within: Olcostephanidae.

The Olcostephaninae are a Lower Cretaceous (Lower Valanginian to Lower Hauterivian) lineage of ammonites, with a questionable record from the Tithonian of the late Jurassic (Wright et al. 1996).

The age of Olcostephaninae
Published 21 December 2020

Ammonites are among the iconic fossils of the Mesozoic. These shelled cephalopods dominated the oceans during their heyday and diversified into a wide array of taxa. Many of these have become significant for recognising particular periods in the earth’s history; among these are members of the Olcostephaninae of the Early Cretaceous.

Olcostephanus astierianus, copyright Hectonichus.

The Olcostephaninae, as recognised by Wright et al. (1996), are known from the Valanginian and Hauterivian epochs of the Early Cretaceous, disappearing from the fossil record some time during the earlier part of the latter. The Valanginian ran from about 140 to 133 million years ago; the Hauterivian lasted for about three and a half million years after that. A brief reminder here: the Cretaceous lasted for a bloody long time, with more time separating the beginning and end of the Cretaceous than separates the end of the Cretaceous and today. One genus described from Pakistan, Provalanginites, has been supposed to come from the latest Jurassic but, as this is at least five million years earlier than any known olcostephanine anywhere else, its age is regarded as questionable. Olcostephanines can be very abundant in formations of the right age. A mass occurrence in the latest Valanginian of northwestern Europe has long been recognised as a geological marker, dubbed the ‘Astierien Schichten’ (Astieria being a synonym of Olcostephanus; Lukeneder 2004).

Saynoceras verrucosum, from here.

Olcostephanines are small to moderate-sized ammonites. Lukeneder (2004) refers to macroconches* of Olcostephanus guebhardi up to about ten centimetres in diameter. The olcostephanines pictured in Wright et al. (1996) seem to indicate an average size smaller than this and the group also includes a number of dwarf genera that look to only be a bit over one centimetre in diameter. The shell of olcostephanines is usually characterised by a pattern of transverse ribs coalescing in bundles to meet tubercles on the inner margin of the whorl. One dwarf genus, Saynoceras, has a stronger ornamentation of two rows of tubercles near the midline and outer margins of the whorls.

*A common pattern in ammonoids is the co-occurrence within a formation of distinct forms, termed ‘macroconches’ and ‘microconches’, that are broadly similar except in size and the configuration of the aperture (generally simple in macroconches but with protruding lappets in microconches). The most popular interpretation of this phenomenon is that the forms represent sexual dimorphism. Obviously which sex is which can’t be known at this time though comparison with living cephalopods suggests that the macroconches may be female.

Valanginites nucleus, from here.

Olcostephanines are very similar in external appearance to the earlier subfamily Spiticeratinae (known from the very earliest part of the Cretaceous) and are likely to be descended from among that group. Though the Olcostephaninae themselves as currently recognised disappeared during the Hauterivian epoch, this may not have been the actual end of the olcostephanine lineage. The slightly later Holcodiscidae are very similar to the olcostephanines and some have questioned whether they even warrant separation. There is also a strong similarity between early members of the superfamily Desmoceratoidea and species of Olcostephanus (Wright et al. 1996). If this similarity also indicates ancestry, then the family line of the olcostephanines would continue right until the final extinction of the ammonites at the end of the Cretaceous.

Systematics of Olcostephaninae

Characters (from Wright et al. 1996): Moderately involute to moderately evolute, compressed to globular or cadicone; generally primary ribs splitting on umbilical shoulder at spine or bulla into sheaf of secondary ribs that cross venter without interruption; strong constrictions normally present at some stage of growth. Typical forms include large macroconchs with simple apertures and smaller, lappeted microconchs. Subfamily also includes succession of dwarf genera with specialized ribbing and tuberculation on outer whorls.

Olcostephaninae [Capeloitinae, Garcitinae, Provalanginitinae, Saynoceratinae, Taraisitinae]WCH96
|--Capeloites Lissón 1937MBF15
| `--C. perelegans (Matheron 1878) [=Ammonites perelegans; incl. *C. larozai Lisson 1937]WCH96
|--+--Saynoceras Munier-Chalmas 1894MBF15
| | `--*S. verrucosum (d’Orbigny 1841)WCH96, MBF15 [=Ammonites verrucosusWCH96]
| `--Valanginites Kilian 1910MBF15 (see below for synonymy)
| |--*V. nucleus (Roemer 1841) [=Ammonites nucleus]WCH96
| |--V. argentinicus Leanza & Wiedmann 1980MBF15
| `--V. wilfridi (Karakasch 1902) (see below for synonymy)WCH96
`--Olcostephanus Neumayr 1875 [=Astieria Pavlow 1892, Holcostephanus Sayn 1889; incl. Maderia Imlay 1938]MBF15
| i. s.: *Maderia’ coronata Imlay 1938WCH96
| O. inverselobatusEK02
|--O. (Olcostephanus) (see below for synonymy)WCH96
| | i. s.: *O. (O.) asterianus (d’Orbigny 1840)MBF15 [=Ammonites asterianusMBF15, *Astieria astierianaWCH96]
| | *Taraisites’ boesi Cantu-Chapa 1966WCH96
| | O. (O.) detonii (Rodighiero 1919)MBF15
| | O. (O.) madagascariensis Lemoine 1906 [=*Lemurostephanus madagascariensis]WCH96
| | O. (O.) mingrammiMBF15
| | O. (O.) mittreanus (d’Orbigny 1850)MBF15
| | O. (O.) nicklesi Wiedmann & Dieni 1968MBF15
| | ‘Rogersites’ quinquestriatus Besairie 1936 [=*Jeanthieuloyites quinquestriatus]WCH96
| | O. (O.) sulcosus Pavlow 1892 [=O. (Astieria) sulcosus, *Subastieria sulcosa]WCH96
| | O. (O.) variegatusP93
| |--O. (O.) atherstoni (Sharpe 1856)MBF15 (see below for synonymy)
| `--+--O. (O.) densicostatus (Wegner 1909)MBF15
| `--O. (O.) sayni (Kilian 1895)MBF15
|--O. (Jeannoticeras Thieuloy 1965)WCH96
| `--O. (*J.) jeannotii (Orbigny 1841) [=Ammonites jeannotii]WCH96
`--O. (Viluceras Aguirre-Urreta & Rawson 1999)MBF15
`--O. (*V.) permolestus (Leanza 1957) (see below for synonymy)MBF15

Olcostephaninae incertae sedis:
Baronnites Bulot, Company & Thieuloy 1990WCH96
`--*B. hirsutus (Fallot & Termier 1923) [=Saynoceras hirsutum]WCH96
Parastieria Spath 1923WCH96
`--*P. peltoceroides (Pavlow 1892) [=Acantoceras peltoceroides]WCH96
Provalanginites Fatmi 1972WCH96
`--*P. rhodesi Fatmi 1972WCH96
Ceratotuberculus Imlay 1938WCH96
|--*C. casitensis Imlay 1938WCH96
`--C. linguituberculatusWCH96
Santafecites Etayo-Serna 1985MBF15
`--*S. santafecinus (d’Orbigny 1842) [=Ammonites santafecinus]MBF15
Garcites Cantú-Chapa 2001MBF15
*Peruvites broggianus (Lissón 1937) [=Sphaeroceras broggianus]MBF15
Mexicanoceras Imlay 1938MBF15 [incl. Maderia Imlay 1938WCH96]
`--*M. kanei Imlay 1938 [=Olcostephanus (*Mexicanoceras) kanei]WCH96

Nomen nudum: *Satoites oshimense Cantu-Chapa 1966WCH96

Olcostephanus Neumayr 1875 (Olcostephanus) [incl. Jeanthieuloyites Cooper 1981, Lemurostephanus Thieuloy 1977, Rogersites Spath 1924, Satoites Cantu-Chapa 1966 (n. n.), Subastieria Spath 1923, Taraisites Cantú-Chapa 1966]WCH96

Olcostephanus (Olcostephanus) atherstoni (Sharpe 1856)MBF15 [=Ammonites atherstoniMBF15, Astieria atherstoniMBF15, Holcostephanus atherstoniMBF15; incl. As. actinota Baumberger 1908MBF15, Rogersites baini var. ambikyi Besairie 1936MBF15, Holcostephanus auritus Leanza 1944MBF15, Ammonites baini Sharpe 1856MBF15, Olcostephanus bainiMBF15, Astieria catulloi Rodighiero 1919MBF15, O. catulloiMBF15, As. curacoensis Weaver 1931MBF15, O. curacoensisMBF15, Rogersites curvicostatus Besairie 1936MBF15, R. douvillei Besairie 1932MBF15, Holcostephanus douvilleiMBF15, H. (Astieria) guebhardi Kilian 1902MBF15, Olcostephanus guebhardiMBF15, O. guebhardi morphotype hollwedensisMBF15, Astieria imbricata Baumberger 1908MBF15, As. psilostoma var. lateumbilicata Roch 1930MBF15, Olcostephanus guebhardi lateumbilicatusMBF15, O. psilostomus lateumbilicatusMBF15, Holcostephanus modderensis Kitchin 1908WCH96, *Rogersites modderensisWCH96, Astieria leptoplana Baumberger 1908MBF15, Holcostephanus midas Leanza 1944MBF15, Rogersites otoitoides Spath 1930MBF15, Olcostephanus guebhardi morphotype querolensisMBF15, Holcostephanus rogersi Kitchin 1908MBF15, O. rogersiWCH96, Ammonites schenki Oppel 1863MBF15, Holcostephanus (Astieria) schenckiMBF15, Olcostephanus (Rogersites) schenckiMBF15, Rogersites sphaeroidalis Spath 1930MBF15, O. baini var. sphaeroidalisMBF15, Astieria sudandina Windhausen 1931 (n. n.)MBF15, Holcostephanus wilmanae Kitchin 1908MBF15]

Olcostephanus (*Viluceras) permolestus (Leanza 1957) [=Simbirskites permolestus, O. (Lemurostephanus) permolestus; incl. Holcostephanus copiapoensis Corvalán in Segerstrom et al. 1963 (n. n.)]MBF15

Valanginites Kilian 1910MBF15 [incl. Dobrodgeiceras Nikolov 1963WCH96, Dobrodgeites Nikolov 1962 non Kittl 1908WCH96, Rotundites Stolley 1937 (n. n.)WCH96]

Valanginites wilfridi (Karakasch 1902) [=Holcostephanus wilfridi; incl. *Dobrodgeites ventrotuberculatus Nikolov 1962, *Dobrodgeiceras ventrotuberculatum]WCH96

*Type species of generic name indicated

References

[EK02] Engeser, T., & H. Keupp. 2002. Phylogeny of the aptychi-possessing Neoammonoidea (Aptychophora nov., Cephalopoda). Lethaia 35: 79–96.

Lukeneder, A. 2004. The Olcostephanus level: an Upper Valanginian ammonoid mass-occurrence (Lower Cretaceous, Northern Calcareous Alps, Austria). Acta Geologica Polonica 54 (1): 23–33.

[MBF15] Mourgues, F. A., L. G. Bulot & C. Frau. 2015. The Valanginian Olcostephaninae Haug, 1910 (Ammonoidea) from the Andean Lower Cretaceous Chañarcillo Basin, northern Chile. Andean Geology 42 (2): 213–236.

[P93] Page, K. N. 1993. Mollusca: Cephalopoda (Ammonoidea: Phylloceratina, Lytoceratina, Ammonitina and Ancyloceratina). In: Benton, M. J. (ed.) The Fossil Record 2 pp. 213–227. Chapman & Hall: London.

[WCH96] Wright, C. W., J. H. Calloman & M. K. Howarth. 1996. Treatise on Invertebrate Paleontology pt L. Mollusca 4, revised vol. 4. Cretaceous Ammonoidea. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

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