Rhabdoceras suessi, copyright Jose Miguel Lorente.

Belongs within: Agoniatitina.
Contains: Tropitaceae, Paraceltitina, Sageceratina, Pinacoceratina, Arcestaceae, Ceratitaceae, Trachyceratidae, Clydonitaceae, Longobarditidae.

The Ceratitida are a lineage of ammonoids known from the Permian and Triassic, characterised by elaboration of the sutures and ornamentation compared to earlier taxa.

The age of the ceratites
Published 2 November 2019

The ammonites are unquestionably one of the most famous groups of fossil mollusks, indeed of fossil invertebrates in general. Even those who have little consciousness of the fossil world might be expected to have a vague mental picture of a coiled shell housing a squid-like beast. But ammonites are far from being the only group of shelled cephalopod known from the fossil record. And though ammonites may have dominated the marine environment during the Jurassic and Cretaceous periods, during the preceding Triassic period they were overshadowed by another such group, the ceratites.

Reconstruction of Ceratites spinosus, from Klug et al. (2007).

The ceratites of the order Ceratitida (or suborder Ceratitina, depending on how you’ve tuned your rank-o-meter today) were close relatives of the ammonites, each deriving separately from an earlier cephalopod group known as the prolecanitids. The earliest forms regarded as ceratites appeared during the mid-Permian, though the exact dividing line between prolecanitid and ceratite seems to be somewhat arbitrary (as, indeed, is only to be expected with a well-known historical lineage). During the remainder of the Permian their diversity remained fairly subdued. When marine life was hit with the cataclysmic upheaval that was the end-Permian extinction, two lineages of ceratites managed to squeak through, together with a single other prolecanitid lineage that would give rise to the ammonites during the ensuing Triassic. With most of their competitors thus eliminated, ceratite diversity expanded rapidly.

Externally, the shells of ceratites and ammonites were very similar, and without knowing their evolutionary context one would be hard-pressed to tell one from the other. Most ceratite shells formed the typical flat spiral one associates with ammonoids, with different species being variously evolute (with successive coils lying alongside the previous one) to involute (outer coils overlapping and concealing the inner ones), and cross-sections varying from narrow and lenticular to broad and low (Arkell et al. 1957). One later Triassic family, the Choristoceratidae, had shells that began as an evolute coil but became uncoiled or straightened in later stages. Another Upper Triassic group, the Cochloceratidae, had turreted shells that might externally be mistaken for those of a gastropod.

Ceratites dorsoplanus, showing ceratitic sutures, copyright Hectonichus.

Internally, ceratites and ammonites often differed in the structure sutures, the lines formed by the join between the outer shell and the septa dividing the internal chambers. In ammonoids as a whole, the sutures are variously curved back and forth on the inside of the shell, with those parts of the suture going forwards (towards the shell opening) forming what are called saddles and those going backwards (away from the opening) forming lobes. In most ceratites, the sutures more or less form a pattern that is known (appropriately enough) as ceratitic: the saddles are simple and not future divided, but the lobes have multiple smaller digitations. In some later taxa, the sutures became goniatitic (with both saddles and lobes simple, secondarily similar to those found in earlier ammonoids) or ammonitic (with both saddles and lobes subdivided, the pattern more commonly associated with ammonites).

Our knowledge of the soft anatomy of ceratites remains limited. We know that they possessed an anaptychus (a leathery plate at the front of the body that may have functioned as an operculum, as I described in an earlier post). Known radulae have fairly simple, slender, undifferentiated teeth (Kruta et al. 2015) so they were probably micro-predators or planktivores in the manner of most ammonites. A black, bituminous layer sometimes preserved against the inside of the shell in the body cavity may represent the remains of the dorsal mantle. Similarity between this layer and the dorsal mantle of nautilids lead Klug et al. (2007) to infer the presence of a non-mineralised hood in ceratites, though I wonder how the presence of a hood would relate to an anaptychus. Conversely, Doguzhaeva et al. (2007) interpreted the black layer as the remains of ink from a ruptured ink sac.

Assemblage of Arcestes leiostracus, copyright Lubomír Klátil.

Ceratites were to remain the ecological upper hand throughout the course of the Triassic. Though ammonites (represented by the phylloceratidans) were not uncommon during this period, their diversity remained consistently lower. However, the end of the Triassic was marked by a spike in global temperatures and ocean acidification, generally regarded as connected to the volcanic rifting activity that marked the beginning of formation of the Atlantic Ocean (Arkhipkin & Laptikhovsky 2012). Of the two ammonoid lineages, only the ammonites survived into the Jurassic; the ceratites were wiped out. Whether some aspect of ammonite biology made them better suited to survive the stresses of global climate change, or whether their survival was a question of simple dumb luck, seems to be an open question. Nevertheless, with the ceratites out of the picture, the way was open for the ammonites to become the lords of the Mesozoic ocean.

Systematics of Ceratitina
Ceratitina [Arcestina, Ceratitida, Sagecerae]KK12
| i. s.: KipsteiniaH84
| ProceltitesH84
| TropitaceaeHK93
|--Otoceratitaceae [Otoceratina]T81
| |--Anderssonoceratidae [Anderssonoceratinae, Planodiscoceratinae]HK93
| | |--Lenticoceltites Zhao et al. 1978T81
| | |--Anderssonoceras Grabau 1924 [incl. Fengchengoceras Zhao et al. 1978, Xiangulites Zhao et al. 1978]T81
| | | `--A. anfuense Grabau 1924HK93 [=Glyphioceras anfuenseG31]
| | `--Pericarinoceras Zhao & Liang 1966 (see below for synonymy)T81
| | `--P. robustum Zhao & Liang 1966HK93
| |--OtoceratidaeHK93
| | |--Anotoceras Hyatt 1900T81
| | | `--A. nala (Diener 1897)HK93
| | `--Otoceras Griesbach 1880 [incl. Metotoceras Spath 1930]T81
| | |--O. borealeK79
| | |--O. concavum Tozer 1967HK93
| | `--O. woodwardiK79
| `--Araxoceratidae [Araxoceratinae, Konglingitinae]HK93
| |--Araxoceras Ruzhencev 1959 (see below for synonymy)T81
| |--Protoceras complanatum Zhao et al. 1978HK93
| |--Anfuceras Zhao et al. 1978 [incl. Periptychoceras Zhao et al. 1978]T81
| |--Prototoceras Spath 1930 (see below for synonymy)T81
| |--Dzhulfoceras Ruzhencev 1962T81
| |--Pseudotoceras Ruzhencev 1962 [incl. Julfotoceras Bando 1973]T81
| |--Eoaraxoceras Spinosa et al. 1970T81
| | `--E. ruzhenceviRR79
| |--Sanyangites Zhao et al. 1978T81
| | `--S. tricarinatus Zhao et al. 1978HK93
| `--Kingoceras Miller 1944T81
| `--K. kingiRR79
|--Lobitidae [Lobitaceae]KK12
| |--Orestites Renz 1911T81
| |--Lobites Mojsisovics 1875 [incl. Indolobites Renz 1911, Psilolobites Renz 1911]T81
| | `--L. paceanus McLearn 1937HK93
| |--Coroceras Hyatt 1877T81
| | `--C. suessi (Mojsisovics 1875)HK93
| `--Paralobites Mojsisovics 1902T81
| `--P. nautilinusWK81
| |--Parapopanoceratidae [Prosphingitinae]T81
| | |--Parapopanoceras Haug 1894 [incl. Dienerites Mojsisovics 1902, Ptychopopanoceras Spath 1951]T81
| | |--Prosphingites Mojsisovics 1886HK93, T81
| | | `--P. czekanowski Mosisovics 1886HK93
| | |--Amphipopanoceras Voinova 1947 [incl. Beaumontites Browne 1952, Parasphingites Popov 1961]T81
| | | `--A. dzeginense (Voinova 1961)HK93
| | `--Stenopopanoceras Popov 1961T81
| | |--S. karangatiense (Popov 1968)HK93
| | `--S. mirabile Popov 1961HK93
| `--MegaphyllitidaeHK93
| |--Nitanoceras McLearn 1937T81
| |--Metasturia Spath 1951T81
| |--Dobrogeites Kittl 1908T81
| `--Megaphyllites Mojsisovics 1879T81
| |--M. boehmi Pompeckji 1895HK93
| |--M. chiosensis Fantini Sestini 1981HK93
| |--M. insectus Mojsisovics 1873HK93
| |--M. prometheusWK81
| |--M. robustus Wiedmann 1973HK93
| `--M. sandalinus Mojsisovics 1882HK93
| |--TrachyceratidaeKK12
| `--ClydonitaceaeKK12
`--Danubitidae [Danubitaceae]KK12
|--Danubites Mojsisovics 1893 [incl. Florianites Hyatt 1900, Rikuzenites Yabe 1949]T81
|--Pseudodanubites Hyatt 1900 [incl. Gosauites Shevyrev 1968]T81
|--Arctohungarites Diener 1916T81
|--Czekanowskites Diener 1915 [incl. Epiczekanowskites Popov 1961, Subarctoceras Popov 1961 (n. n.)]T81
|--Stannakhites Vavilov 1978T81
|--Judicarites Mojsisovics 1896T81
|--Paradanubites Shevyrev 1968T81
| `--P. depressus Fantini Sestini 1981HK93
|--Ticinites Rieber 1973T81
| `--T. polymorphus Rieber 1973HK93
`--Eodanubites Wang 1978T81
|--E. costulatus Wang 1978HK93
`--E. xingyuanensis Wang 1978HK93

Araxoceras Ruzhencev 1959 [incl. Avushoceras Ruzhencev 1962, Kiangsiceras Zhao & Liang 1965, Konglingites Zhao et al. 1978, Rotaraxoceras Ruzhencev 1959, Vedioceras Ruzhencev 1962]T81

Pericarinoceras Zhao & Liang 1966 [incl. Leptogyroceras Zhao & Liang 1966, Pachyrotoceras Zhao et al. 1978, Planodiscoceras Zhao & Liang 1966]T81

Prototoceras Spath 1930 [incl. Discotoceras Spath 1930, Jinjiangoceras Zhao et al. 1978, Urartoceras Ruzhencev 1959, Vescotoceras Ruzhencev 1962]T81

*Type species of generic name indicated


Arkell, W. J., B. Kummel & C. W. Wright. 1957. Mesozoic Ammonoidea. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt L. Mollusca 4. Cephalopoda: Ammonoidea pp. L80–L465. Geological Society of America, and University of Kansas Press.

Arkhipkin, A. I., & V. V. Laptikhovsky. 2012. Impact of ocean acidification on plankton larvae as a cause of mass extinctions in ammonites and belemnites. Neues Jahrbuch für Geologie und Paläontologie—Abhandlungen 266 (1): 39–50.

Doguzhaeva, L. A., R. H. Mapes, H. Summesberger & H. Mutvei. 2007. The preservation of body tissues, shell, and mandibles in the ceratitid ammonoid Austrotrachyceras (Late Triassic), Austria. In: Landman, N. H., R. A. Davis & R. H. Mapes (eds) Cephalopods Past and Present: New Insights and Fresh Perspectives pp. 221–238. Springer.

[G31] Grabau, A. W. 1931. The Permian of Mongolia: A report on the Permian fauna of the Jisu Honguer limestone of Mongolia and its relations to the Permian of other parts of the world. American Museum of Natural History: New York.

[HK93] Hewitt, R. A., J. Kullmann, M. R. House, B. F. Glenister & Wang Y.-G. 1993. Mollusca: Cephalopoda (pre-Jurassic Ammonoidea). In: Benton, M. J. (ed.) The Fossil Record 2 pp. 189–211. Chapman & Hall: London.

[H84] Hyatt, A. 1883–1884. Genera of fossil cephalopods. Boston Soc. Nat. History, Proc. 22: 253–338.

Klug, C., M. Montenari, H. Schulz & M. Urlichs. 2007. Soft-tissue attachment of Middle Triassic Ceratitida from Germany. In: Landman, N. H., R. A. Davis & R. H. Mapes (eds) Cephalopods Past and Present: New Insights and Fresh Perspectives pp. 205–220. Springer.

[KK12] Korn, D., & C. Klug. 2012. Palaeozoic ammonoids—diversity and development of conch morphology. In: Talent, J. A. (ed.) Earth and Life: Global biodiversity, extinction intervals and biogeographic perturbations through time pp. 491–534. Springer.

Kruta, I., N. H. Landman & K. Tanabe. 2015. Ammonoid radula. In: Klug, C., et al. (eds) Ammonoid Paleobiology: From Anatomy to Ecology pp. 485–505. Springer: Dordrecht.

[K79] Kummel, B. 1979. Triassic. In: Robison, R. A., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt A. Introduction. Fossilisation (Taphonomy), Biogeography and Biostratigraphy pp. A351–A389. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

[RR79] Ross, C. A., & J. R. P. Ross. 1979. Permian. In: Robison, R. A., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt A. Introduction. Fossilisation (Taphonomy), Biogeography and Biostratigraphy pp. A291–A350. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

[T81] Tozer, E. T. 1981. Triassic Ammonoidea: classification, evolution and relationship with Permian and Jurassic forms. In: House, M. R., & J. R. Senior (eds) The Ammonoidea: The evolution, classification, mode of life and geological usefulness of a major fossil group pp. 66–100. Academic Press.

[WK81] Wiedmann, J., & J. Kullmann. 1981. Ammonoid sutures in ontogeny and phylogeny. In: House, M. R., & J. R. Senior (eds) The Ammonoidea: The evolution, classification, mode of life and geological usefulness of a major fossil group pp. 215–255. Academic Press.

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