Nautilosiphonata

Reconstruction of the Middle Silurian Mandaloceras, from Palaeos.com.

Belongs within: Mollusca.
Contains: ‘Acaroceras’, Protocycloceras, Ellesmeroceratidae, Piloceratidae, Manchuroceratidae, Coreanoceratidae, Najaceratidae, Bathmoceratidae, Oncoceratida, Nautilida, Tarphyceratida, Ascoceratidae, Naedyceratidae, Brevicoceratidae, Westonoceratidae, Cyrtogomphoceratidae, Mandaloceratidae.

The Middle Ordovician to Middle Devonian Discosorida were an order of mostly breviconic or cyrtoconic cephalopods. The major distinguishing feature of the group was the development of thick, layered connecting rings around the siphuncle that overlapped the septal necks to form mineralised protrusions called bullettes.

Arranging nautiloids
Published 27 March 2022

For years, the higher taxonomy of cephalopods was expressed as a division between three subclasses: the Nautiloidea, the Ammonoidea and the Coleoidea. Coleoids were the clade of cephalopods that had lost the external shell, ammonoids were a Mesozoic lineage with complex septa dividing the chambers of the shell, and nautiloids were… the rest. From the tiny, possibly benthic, curved cones of the Cambrian where the class began, to gigantic straight-shelled monsters of the later Palaeozoic, to the modern chambered nautilus, all were lumped together as ‘nautiloids’. The nautiloid subclass was explicitly understood to include the ancestors of the others but recognition of more phylogenetically coherent subgroups has been hampered by poor understanding about how the various nautiloid lineages were interrelated. And part of the problem in this regard has been uncertainty about just what features of their fossils we should be paying attention to.

Diorama reconstruction of Beloitoceras oncocerids, from the Burpee Museum.

One factor that has drawn attention in recent years has been the arrangement of muscle scars on the shell. Large muscle attachment scars appear as raised annular elevations on the inside of the shell towards the rear end of the body chamber (in practice, they are more often observed in fossils as depressions on the internal mould). In the living nautilus, the muscles attached to these scars function in the retraction of the head (King & Evans 2019). Modern nautilus possess a pair of large lateral scars in an arrangement that has been labelled ‘pleuromyarian’. However, many of the earliest cephalopods possessed a ring of numerous small scars, an arrangement referred to as ‘oncomyarian’. Other cephalopods might have scars restricted to the dorsal (‘dorsomyarian’) or ventral (‘ventromyarian’) midline.

Primary types of muscle scar in nautiloids, from King & Evans (2019). ‘D’ and ‘V’ indicate dorsal and ventral, respectively, and arrows indicate direction of aperture.

Another feature that has been called out has been the structure of the connecting rings around the siphuncle. Shelled cephalopods, you will recall, have the shell divided into chambers separated by septa. Though the bulk of the animal is found in the final body chamber, a fleshy cord called the siphuncle runs back through the remaining chambers. In life, the siphuncle is used to control the levels of fluid in the chambers, which in turn controls the animal’s buoyancy. The boundary between the siphuncle and the surrounding chamber is marked a toughened sheath, referred to as the connecting ring. In the modern nautilus, the connecting ring is comprised of two layers, an outer calcareous layer and an inner chitinous layer. In comparable fossils, the latter chitinous layer has decomposed after death so only the outer layer is preserved. However, some extinct cephalopod groups preserve evidence of calcification in the inner as well as the outer layer. Based on the distinction between these two siphuncle types, Mutvei (2015) supported dividing most of the nautiloids between two major lineages, the Nautilosiphonata (with a nautilus-type siphuncle) and the Calciosiphonata (with the internally calcified connecting rings).

A couple of years earlier, the same author (Mutvei 2013) had proposed recognition of a superorder Multiceratoidea for nautiloids that combined multiple muscle scars with a nautilus-type siphuncle. Examples of nautiloid orders with such a combination included the Ellesmeroceratida (small nautiloids with densely placed septa), the Oncoceratida (often short, squat nautiloids) and the Discosorida (similarly squat forms with complex bulging connecting rings). All of these were found in the earlier part of the Palaeozoic with the oncoceratids dieing off in the early Carboniferous. Mutvei (2013) also included the coiled Tarphyceratida and the egg-shaped Ascoceratida in this group. Later, King & Evans (2019) redefined this grouping as the Multiceratia, excluding the Tarphyceratida and Ascoceratida on the grounds that they had ventromyarian rather than oncomyarian muscle scars. Mutvei (2013) suggested that, rather than representing retractor muscles, these smaller repeated scars were associated with an outgrowth of the mantle, either as tentacles or a muscular ‘skirt’, that was used to capture micro-plankton.

Phylogeny of ‘nautiloids’ supported by King & Evans (2019). Though not shown on this diagram, the majority of authors have suggested that ammonoids and coleoids are descended from Orthoceratida.

King & Evans (2019) proposed a reclassification of the subclass Nautiloidea between five subclasses defined primarily by muscle structure. Apart from the earliest oncomyarian Plectronoceratia, most ‘nautiloids’ could be divided between two lineages. On one side were the dorsomyarian Orthoceratia (usually thought to include the ancestors of the ammonoids and coleoids). On the other, the oncomyarian Multiceratia would eventually give rise to the ventromyarian Tarphyceratia which in turn included the ancestors of the pleuromyarian Nautilida. Note that many of the reocognised subclasses (and orders) remain paraphyletic but we are at least approaching a more informative picture of cephalopod evolution than the earlier unceremonious dumping into ‘Nautiloidea’ (I should probably also remind you that, for various reasons, most invertebrate palaeontologists still don’t regard strict monophyly as a taxonomic requirement in and of itself).

The usage of muscle scars and connecting rings as classificatory keys is handicapped by the difficulty of observing them. As internal structures, they each require careful preparation of a specimen to observe. And once you’ve gotten to a position where you can see them, it seems not to be particularly easy to tell just what you’re looking at. As a result, muscle scarring and siphon structure remains undescribed for the majority of nautiloid species. Judging the structure of connecting rings seems to be particularly challenging and some have gone so far as to suggest that purported different structures may be the result of post-mortem taphonomic processes (King & Evans 2019). Nevertheless, what we do know suggests that such features remain reasonably consistent within each of the well-recognised nautiloid orders. And Mutvei’s (2015) concept of Calciosiphonata vs Nautilosiphonata does largely line up with King & Evans’ (2019) dorsomyarian vs oncomyarian-ventromyarian lineages. There are, of course, some notable exceptions. Whether these will cause the developing structure to collapse, or whether they indicate mistakes in interpretation, only continued research will tell.

Systematics of Nautilosiphonata
<==Nautilosiphonata [Multiceratia, Multiceratoidea]M13
    |--Ellesmeroceratida [Ellesmeroceratina, Ellesmerocerida, Ellesmerocerina, Holochoanoida, Prochoanites]KE19
    |    |--PhthanoncoceratidaeM13
    |    |    |--PhthanoncocerasKE19
    |    |    |    |--P. ellipticumKE19
    |    |    |    `--P. oelandense Evans & King 1990K93
    |    |    `--Valhalloceras floweri Evans & King 1990K93
    |    |--Xiaoshanoceras Chen & Teichert 1983 [Xiaoshanoceratidae]CT83
    |    |    |--*X. jini Chen & Teichert 1983K93
    |    |    `--X. subcirculare Chen & Teichert 1983K93
    |    |--Shideleroceras Flower & Foerste in Flower 1946FG64a [ShideleroceratidaeK93]
    |    |    |--*S. sinuatum Foerste in Flower 1946FG64a
    |    |    |--S. gracile Flower 1946K93
    |    |    `--S. simplex Flower 1946K93
    |    |--AcaroceratidaeK93
    |    |    |--Weishanhuceras Chen & Qi 1979CT83
    |    |    |    `--W. rarum Chen & Qi 1979K93
    |    |    `--‘Acaroceras’CT83
    |    |--ApocrinoceratidaeK93
    |    |    |--Apocrinoceras Teichert & Glenister 1954FG64a
    |    |    |    `--*A. talboti Teichert & Glenister 1954FG64a
    |    |    `--Glenisteroceras Flower in Flower & Teichert 1957K93, S64a
    |    |         `--*G. obscurum Flower in Flower & Teichert 1957S64a
    |    |--CyclostomiceratidaeK93
    |    |    |--Pictetoceras Foerste 1926 (n. d.)M13, S64b
    |    |    |    |--*P. eichwaldi (de Verneuil 1845) [=Gomphoceras eichwaldi]S64b
    |    |    |    `--P. oliviaeKE19
    |    |    `--Cyclostomiceras Hyatt in Zittel 1900 [=Clostomiceras (l. c.); incl. Amphoroceras Ulrich & Foerste 1936]FG64a
    |    |         |--*C. cassinense (Whitfield 1886) [=Gomphoceras cassinense]FG64a
    |    |         |--C. depressum Ulrich, Foerste & Miller 1943P68
    |    |         `--C. minimum (Whitfield 1886)K93
    |    |--HuaiheceratidaeK93
    |    |    |--Huaihecerina Chen & Teichert 1983CT83
    |    |    |    `--*H. elegans Chen & Teichert 1983K93
    |    |    |--Zhuibianoceras Chen & Qi 1981CT83
    |    |    |    `--Z. conicum Chen & Qi 1981K93
    |    |    `--Huaiheceras Zou & Chen 1979CT83
    |    |         |--*H. hanjianense Zou & Chen in Chen et al. 1979CT83
    |    |         |--H. exogastrum Chen & Qi 1980CT83
    |    |         |--H. liaoningense Chen & Teichert 1983CT83
    |    |         |--H. longicollum Zou & Chen 1979K93
    |    |         |--H. qianshanense Zou & Chen 1979CT83
    |    |         `--H. xiaoshanense Chen & Teichert 1983CT83
    |    |--Protocycloceratidae [Endocycloceratidae, Rudolfoceratidae]STK64
    |    |    |--ProtocyclocerasFG64a
    |    |    |--Diastoloceras Teichert & Glenister 1954FG64a
    |    |    |    `--*D. perplexum Teichert & Glenister 1954FG64a
    |    |    |--Kyminoceras Teichert & Glenister 1954FG64a
    |    |    |    `--*K. forresti Teichert & Glenister 1954FG64a
    |    |    |--Notocycloceras Teichert & Glenister 1954FG64a
    |    |    |    `--*N. yurabiense Teichert & Glenister 1954FG64a
    |    |    |--Rudolfoceras Ulrich, Foerste et al. 1944 [incl. Orygoceras Ruedemann 1906 non Brusina 1882]FG64a
    |    |    |    `--*R. cornuoryx (Whitfield 1886) [=Orthoceras cornuoryx]FG64a
    |    |    |--Vassaroceras Ulrich, Foerste et al. 1944FG64a
    |    |    |    `--*V. henrietta (Dwight 1884) [=Orthoceras henrietta]FG64a
    |    |    |--Ectocycloceras Ulrich & Foerste 1936FG64a
    |    |    |    |--*E. cataline (Billings 1865) [=Orthoceras cataline]FG64a
    |    |    |    `--E. catoFG64a
    |    |    |--Walcottoceras Ulrich & Foerste 1936FG64a
    |    |    |    |--*W. monsense (Walcott 1924) [=Endoceras monsensis]FG64a
    |    |    |    `--W. obliquum Ulrich, Foerste et al. 1944P68
    |    |    |--Endocycloceras Ulrich, Foerste et al. 1944FG64a
    |    |    |    |--*E. wilsonae Ulrich, Foerste et al. 1944FG64a
    |    |    |    |--E. legorense Ulrich, Foerste et al. 1944P68
    |    |    |    |--E. perannulatum Ulrich, Foerste et al. 1944P68
    |    |    |    `--E. subcurvatum Ulrich, Foerste et al. 1944P68
    |    |    `--Catoraphiceras Ulrich & Foerste 1936FG64a
    |    |         |--*C. lobatum Ulrich & Foerste 1936FG64a
    |    |         |--C. colonFG64a
    |    |         |--C. cushingi Ulrich, Foerste et al. 1944P68
    |    |         |--C. foersteiP68
    |    |         |--C. osagense Ulrich, Foerste et al. 1944P68
    |    |         |--C. resseri Ulrich, Foerste et al. 1944P68
    |    |         `--C. vaginatumFG64a
    |    `--+--EllesmeroceratidaeFG64a
    |       `--Bisonoceratida [Hemipiloceratidae]KE19
    |            |  i. s.: Hemipiloceras Shimizu & Obata 1936EK12 [=Hemipoloceras (l. c.)T64a]
    |            |           `--*H. ellipticum Shimizu & Obata 1936T64a
    |            |         Kueichouceras Yu & Wang 1965EK12
    |            |         Nanno Clarke 1894EK12 [=Featherstonhaughoceras Clarke in Bather 1894T64a, Mannoceras (l. c.)T64a]
    |            |           |--*N. aulema Clarke 1894 [=*Featherstonhaughoceras aulema]T64a
    |            |           |--N. belemnitiformeEK12
    |            |           `--N. walcotti Foerste 1935P68
    |            |         Penhsioceras Endo 1932EK12 [=Penchsioceras (l. c.)T64a]
    |            |           `--*P. fusiforme Endo 1932T64a
    |            |         Ernosoceras Xu & Lai 1987EK12
    |            |         Fenxiangoceras Xu & Lai 1987EK12
    |            |         Subpenhsioceras Shimizu & Obata 1936EK12
    |            |           `--*S. spindleforme Shimizu & Obata 1936T64a
    |            |         Yehlioceras Shimizu & Obata 1937EK12
    |            |           `--*Y. yehliense (Grabau 1922) [=Suecoceras yehliense]T64a
    |            |--PiloceratidaeEK12
    |            |--ManchuroceratidaeEK12
    |            |--CoreanoceratidaeEK12
    |            |--Sinoendoceras Lai 1985 [Sinoendoceratidae]EK12
    |            |--NajaceratidaeEK12
    |            |--Chihlioceras Grabau 1922T64a [=Chilihoceras (l. c.)T64a, Chilioceras (l. c.)T64a; ChihlioceratidaeEK12]
    |            |    |--*C. nathani Grabau 1922T64a
    |            |    `--C. chingwangtaoense Grabau 1922K93
    |            |--Humeoceras Foerste 1925T64a [HumeoceratidaeEK12]
    |            |    |--*H. unguloideum Foerste in Hume 1925T64a, K93
    |            |    |--H. durdeni Flower 1968K93
    |            |    `--H. tardum Flower 1968K93
    |            |--EmmonsoceratidaeEK12
    |            |    |--Emmonsoceras Flower 1958 [=Hudsonoceras Flower 1956 non Moore 1946]T64a
    |            |    |    `--*E. aristos (Flower 1956) [=*Hudsonoceras aristos]T64a
    |            |    |--Tallinnoceras Balashov 1960T64a
    |            |    |    `--*T. lasnamense Balashov 1960T64a
    |            |    `--Juaboceras Flower 1968EK12
    |            |         `--J. braithwaiti Flower 1968K93
    |            |--ProterovaginoceratidaeEK12
    |            |    |--Perkinsoceras Flower 1976EK12
    |            |    |--Chazyoceras Flower 1958EK12
    |            |    |    `--*C. valcourense Flower 1958T64a
    |            |    `--Proterovaginoceras Ruedemann 1905T64a
    |            |         |--*P. belemnitiforme (Holm 1885) [=Endoceras belemnitiforme]T64a
    |            |         `--P. wahlenbergiT64a
    |            |--BisonoceratidaeEK12
    |            |    |  i. s.: ‘Piloceras’ tasmanienseEK12
    |            |    |--Bisonoceras Flower 1964EK12
    |            |    |    `--B. corniforme Flower 1964EK12
    |            |    |--Disphenoceras Flower 1964EK12
    |            |    |    `--D. conicum Flower 1964EK12
    |            |    `--Parapiloceras Obata 1939EK12
    |            |         `--*P. shimizui Obata 1939T64a
    |            `--AllotrioceratidaeEK12
    |                 |--Williamsoceras Flower 1964EK12
    |                 |--Allotrioceras Flower 1955T64a
    |                 |    `--*A. bifurcatum Flower 1955T64a
    |                 |--Mirabiloceras Flower 1955T64a
    |                 |    `--*M. multitubulatum Flower 1955T64a
    |                 `--Cacheoceras Flower 1968EK12
    |                      |--C. trifidum Flower 1968EK12
    |                      `--C. uninodum Flower 1976EK12
    |--Cyrtocerinida [Cyrtocerinina]KE19
    |    |--Cyrtocerina Billings 1865 [Cyrtocerinidae]FG64
    |    |    |--*C. typica Billings 1865FG64
    |    |    |--C. carinifera Flower 1946K93
    |    |    |--C. crenulata Flower 1952P68
    |    |    |--C. foerstei Flower 1952P68
    |    |    |--C. kimmswickense Flower 1952P68
    |    |    |--C. madisonensis (Miller 1894)K93
    |    |    |--C. modesta Flower 1943K93
    |    |    |--C. patella Flower 1943K93
    |    |    `--C. schoolcrafti Clarke 1897P68
    |    `--BathmoceratidaeK93
    `--+--OncoceratidaKE19
       |--+--NautilidaKE19
       |  `--TarphyceratiaKE19
       |       |--TarphyceratidaKE19
       |       `--Ascoceratida [Ascoceracea, Ascoceratina, Ascocerida, Ecdyceratida, Mixochoanites]KE19
       |            |--AscoceratidaeFG64b
       |            |--Choanoceras Lindström 1890 (see below for synonymy)FG64b
       |            |    |--*C. mutabile Lindström 1890FG64b
       |            |    `--C. immitansKE19
       |            `--HebetoceratidaeFG64b
       |                 |--Hebetoceras Flower 1941FG64b
       |                 |    |--*H. mirandum Flower 1941FG64b
       |                 |    `--H. cylindriformeKE19
       |                 |--Ecdyceras Flower 1941 [incl. Pachecdyceras Flower 1947]FG64b
       |                 |    |--*E. sinuiferum Flower 1941FG64b
       |                 |    `--E. foerstei Flower 1962K93
       |                 `--Montyoceras Flower 1941FG64b
       |                      |--*M. arcuatum Flower 1941FG64b
       |                      |--M. curviceptatum Flower 1941K93
       |                      |--M. titaniforme Flower 1941K93
       |                      `--M. tuba Flower 1963K93
       `--DiscosoridaKE19
            |  i. s.: EntimoceratidaeK93
            |           |  i. s.: ‘Gonatocyrtoceras’ inflatum Foerste 1930K93
            |           |--Selenoceras onerostum Zhuravleva 1972K93
            |           |--Pantoioceras mutum Zhuravleva 1972K93
            |           `--Lysagoroceras Schönenberg 1952K93, S64b
            |                |--*L. angustum Schönenberg 1952S64b
            |                `--L. separatum Zhuravleva 1972K93
            |         NaedyceratidaeK93
            |         UkhtoceratidaeK93
            |           |--Nipageroceras riphaeum Zhuravleva 1972K93
            |           |--Metrioceras desertum Zhuravleva 1972K93
            |           |--Turoceras Zhuravleva 1959K93, S64b
            |           |    `--*T. schnyrevae Zhuravleva 1959S64b
            |           `--RopalocerasK93
            |                |--R. illicitum Zhuravleva 1972K93
            |                `--R. implicatum Zhuravleva 1972K93
            |         BrevicoceratidaeK93
            |         TaxyceratidaeK93
            |           |--Brodekoceras dnestrovense Balashov in Balashov & Kiselev 1968K93
            |           `--Pachtoceras Foerste 1926K93, S64b
            |                |--*P. rotundum (Pacht 1858) [=Gomphoceras rotundum]S64b
            |                |--P. abreviatumKE19
            |                `--P. asiaticum Zhuravleva 1972K93
            |         MecynoceratidaeK93
            |           |--Paramecynoceras fixum Zhuravleva 1972K93
            |           |--Mecynoceras Foerste 1926S64b
            |           |    `--*M. rex (Pacht 1856)S64b, K93 [=Gomphoceras rexS64b]
            |           `--Laumontoceras Foerste 1926K93, S64b
            |                |--*L. laumonti (Barrande 1866) [=Orthoceras laumonti]S64b
            |                `--L. improvisum Zhuravleva 1972K93
            |         DevonochelidaeK93
            |           |--Platyconoceras kuzmini Zhuravleva 1972K93
            |           |--Devonocheilus Shimanskiy 1962S64b
            |           |    `--*D. timanicus (Holzapfel 1899) [=Phragmoceras timanicum]S64b
            |           `--PelagocerasK93
            |                |--P. lautum Zhuravleva 1972K93
            |                `--P. mendicum Zhuravleva 1972K93
            |--WestonoceratidaeT64b
            |--CyrtogomphoceratidaeT64b
            `--+--RuedemannoceratidaeT64b
               |    |--Elkanoceras pluto (Billings 1865)K93
               |    |--Taoqupoceras peculare Lai 1982K93
               |    |--Ruedemannoceras Flower 1940 [Ruedemannoceratidae]T64b
               |    |    `--*R. boycii (Whitfield 1886) [=Cyrtoceras boycii]T64b
               |    `--Franklinoceras Flower 1957T64b
               |         `--*F. elongatum Flower 1957T64b
               `--+--MandaloceratidaeT64b
                  `--GouldoceratidaeK93
                       |--Madiganella Teichert & Glenister 1952T64b
                       |    `--*M. magna Teichert & Glenister 1952T64b
                       `--GouldocerasK93
                            |--G. benjaminense Stait 1984K93
                            |--G. obliquum (Teichert & Glenister 1953)K93
                            `--G. synchonema Stait 1980K93

Choanoceras Lindström 1890 [=Choaniceras Lindström 1888 (n. n.), Choniceras (l. c.), Coanoceras (l. c.); Choanoceratidae]FG64b

*Type species of generic name indicated

References

[CT83] Chen J.-Y. & C. Teichert. 1983. Cambrian Cephalopoda of China. Palaeontographica Abteilung A: Paläozoologie—Stratigraphie 181 (1–3): 1–102.

[EK12] Evans, D. H. & A. H. King. 2012. Resolving polyphyly within the Endocerida: the Bisonocerida nov., a new order of early Palaeozoic nautiloids. Geobios 45 (1): 19–28.

[FG64a] Furnish, W. M., & B. F. Glenister. 1964a. Nautiloidea—Ellesmerocerida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt K. Mollusca 3. CephalopodaGeneral FeaturesEndoceratoideaActinoceratoideaNautiloideaBactritoidea pp. K129–K159. The Geological Society of America and the University of Kansas Press.

[FG64b] Furnish, W. M., & B. F. Glenister. 1964b. Nautiloidea—Ascocerida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt K. Mollusca 3. CephalopodaGeneral FeaturesEndoceratoideaActinoceratoideaNautiloideaBactritoidea pp. K261–K277. The Geological Society of America and the University of Kansas Press.

[K93] King, A. H. 1993. Mollusca: Cephalopoda (Nautiloidea). In: Benton, M. J. (ed.) The Fossil Record 2 pp. 169–188. Chapman & Hall: London.

[KE19] King, A. H., & D. H. Evans. 2019. High-level classification of the nautiloid cephalopods: a proposal for the revision of the Treatise Part K. Swiss Journal of Palaeontology 138: 65–85.

[M13] Mutvei, H. 2013. Characterization of nautiloid orders Ellesmerocerida, Oncocerida, Tarphycerida, Discosorida and Ascocerida: new superorder Multiceratoidea. GFF 135 (2): 171–183.

Mutvei, H. 2015. Characterization of two new superorders Nautilosiphonata and Calciosiphonata and a new order Cyrtocerinida of the subclass Nautiloidea; siphuncular structure in the Ordovician nautiloid Bathmoceras (Cephalopoda). GFF 137 (3): 164–174.

[P68] Purnell, L. R. 1968. Catalog of the type specimens of invertebrate fossils. Part I: Paleozoic Cephalopoda. United States National Museum Bulletin 262: 1–198.

[S64a] Sweet, W. C. 1964a. Nautiloidea—Orthocerida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt K. Mollusca 3. CephalopodaGeneral FeaturesEndoceratoideaActinoceratoideaNautiloideaBactritoidea pp. K216–K261. The Geological Society of America and the University of Kansas Press.

[S64b] Sweet, W. C. 1964. Nautiloidea—Oncocerida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt K. Mollusca 3. CephalopodaGeneral FeaturesEndoceratoideaActinoceratoideaNautiloideaBactritoidea pp. K277–K319. The Geological Society of America and the University of Kansas Press.

[STK64] Sweet, W. C., C. Teichert & B. Kummel. 1964. Phylogeny and evolution. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt K. Mollusca 3. CephalopodaGeneral FeaturesEndoceratoideaActinoceratoideaNautiloideaBactritoidea pp. K106–K114. The Geological Society of America and the University of Kansas Press.

[T64a] Teichert, C. 1964a. Endoceratoidea. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt K. Mollusca 3. CephalopodaGeneral FeaturesEndoceratoideaActinoceratoideaNautiloideaBactritoidea pp. K160–K189. The Geological Society of America and the University of Kansas Press.

[T64b] Teichert, C. 1964b. Nautiloidea—Discosorida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt K. Mollusca 3. CephalopodaGeneral FeaturesEndoceratoideaActinoceratoideaNautiloideaBactritoidea pp. K320–K342. The Geological Society of America and the University of Kansas Press.

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