Belongs within: Nautilida.
The Clydonautilaceae were a lineage of nautilid cephalopods known from the Carboniferous to the Triassic (the genus Potoceras may have appeared earlier in the Upper Devonian). Though early forms had fairly straight sutures, some later forms developed the most complexly folded sutures of any nautiloid (Kummel 1964).
Characteristics (from Kummel 1964): Generally smooth, involute, globular to occluded shells. Sutures nearly straight in early forms but becoming highly differentiated in one later lineage [Clydonautilidae + (Gonionautilus + Siberionautilus)].
<==Clydonautilaceae [Lirocerataceae, Liroceratina] |--Ephippioceratidae [Epphipphioceratidae]K64 | |--Megaglossoceras Miller, Dunbar & Condra 1933K64 | | |--*M. montgomeryense (Worthen 1884) [=Nautilus montgomeryensis]K64 | | `--M. pristinumK64 | `--Ephippioceras Hyatt 1884 [incl. Arthuroceras Shimanskiy 1962]K64 | |--*E. ferratum (Cox 1858) [=Nautilus ferratus]K64 | |--E. bilobatum (Sowerby 1840)K93 [=Nautilus bilobatusH84] | |--E. divisumP68 | |--E. hunanense Chao 1954K93 | |--E. inexpectans Miller & Youngquist 1949K93 | |--E. involutum Chao 1954K93 | `--E. spirale Ramsbottom & Moore 1961K93 |--+--+--Gonionautilus Mojsisovics 1902 [Gonionautilidae]K64 | | | `--G. securis (Von Dittmar 1866) [=Nautilus securis]K64 | | `--Siberionautilus Popov 1951 [Siberionautilidae]K64 | | `--*S. multilobatus Popov 1951K64 | `--ClydonautilidaeK64 | | i. s.: Callaionautilus Kieslinger 1924K64 | | `--*C. turgidus Kieslinger 1924K64 | | Cosmonautilus Hyatt & Smith 1905K64 | | `--*C. dilleri Hyatt & Smith 1905K64 | |--Styrionautilus Mojsisovics 1902K64 | | |--*S. styriacus (Mojsisovics 1873) [=Nautilus styriacus]K64 | | `--S. discoidolisK64 | `--+--Clydonautilus Mojsisovics 1882K64 | | |--*C. noricus (Mojsisovics 1873) [=Nautilus noricus]K64 | | |--C. biangularisK64 | | `--C. timorensisK64 | `--Proclydonautilus Mojsisovics 1902 [=Procladonautilus (l. c.)]K64 | |--*P. griesbachi (Mojsisovics 1896) [=Nautilus griesbachi]K64 | |--P. buddhaicusK64 | |--P. ermolliiK64 | `--P. spirolobusK64 `--Liroceratidae [Coloceratidae, Paranautilidae]K64 |--Alexandronautilus Shimanskiy 1962K64 | `--*A. abichi [=Coloceras abichi, Permonautilus (Alexandronautilus) abichi]K64 |--Condraoceras Miller, Lane & Unklesbay 1947K64 | `--*C. primum Miller, Lane & Unklesbay 1947K64 |--Hemiliroceras Ruzhentsev & Shimanskiy 1954K64 | `--*H. inflatum Ruzhentsev & Shimanskiy 1954K64 |--Indonautilus Mojsisovics 1902K64 | `--*I. kraffti (Mojsisovics 1902) [=Nautilus kraffti]K64 |--Peripetoceras Hyatt 1894 [=Periptoceras (l. c.); incl. Cyclonautilus Hind 1911, Nannoceras Hyatt 1894]K64 | `--*P. freieslebeni (Geinitz 1843) [=Nautilus freieslebeni, Temnocheilus freieslebeni]K64 |--Permonautilus Kruglov 1933K64 | `--*P. cornutus (Golovinsky 1868) [=Nautilus cornutus]K64 |--Potoceras Hyatt 1894K64 | `--*P. dubium Hyatt 1894K64 |--Paranautilus Mojsisovics 1902K64 | |--*P. simonyi (Hauer 1849) [=Nautilus simonyi]K64 | `--P. meridionusK64 |--Sibyllonautilus Diener 1915 [incl. Tumidonautilus Diener 1915]K64 | |--*S. sibyllae (Mojsisovics 1886) [=Nautilus sibyllae]K64 | `--S. fergusoniK64 |--Coelogasteroceras Hyatt 1893 [=Conradiceras Cossmann 1900, Solenoceras Hyatt 1884 non Conrad 1860]K64 | |--*C. coxi Gordon 1960K64 [=Nautilus canaliculatus Cox 1858 non Eichwald 1857K64, *Solenoceras canaliculatumH84] | |--C. mexicanumK64 | |--‘Nautilus’ nodosus [=Solenoceras nodosum]H84 | `--C. uralenseKE19 |--Bistrialites Turner 1954H99 | |--*B. bistrialis (Phillips 1836) (see below for synonymy)H99 | |--B. bimembris Shimansky 1967H99 | |--B. coyanus (Orbigny 1850) (see below for synonymy)H99 | `--B. crowdecotensis Turner 1954H99 `--Liroceras Teichert 1940 [incl. Coloceras Hyatt 1893 non Nitzsch 1882]K64 |--*L. liratum (Girty 1911) [=Coloceras liratum]K64 | |--L. l. liratumP68 | `--‘Coloceras’ l. obsoletum Girty 1911P68 |--L. fornicatum Shimanskiy 1967K93 |--L. globulareP68 |--L. hyatti Miller et al. 1933K93 |--‘Coloceras’ mexicanum Girty 1909P68 `--L. praetunense Shimanskiy 1967K93
*Bistrialites bistrialis (Phillips 1836) [=Nautilus bistrialis, Coelonautilus bistrialis, Coloceras bistriale, Coloceras bistrialis (l. c.), Liroceras bistrialis, Nautilus (Temnocheilus) bistrialis]H99
Bistrialites coyanus (Orbigny 1850) [=Nautilus coyanus, Coloceras coyanum, C. coyanus (l. c.), Vestinautilus coyanus; incl. Nautilus (Temnocheilus) pinguis M’Coy 1844 non de Koninck 1843]H99
*Type species of generic name indicated
References
[H99] Histon, K. 1999. A revision of A. H. Foord’s monograph of Irish Carboniferous nautiloid cephalopods (1897–1901). Part 2. Monograph of the Palaeontographical Society 153: 63–129.
[H84] Hyatt, A. 1883–1884. Genera of fossil cephalopods. Boston Soc. Nat. History, Proc. 22: 253–338.
[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.
[K64] Kummel, B. 1964. Nautiloidea—Nautilida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt K. Mollusca 3. Cephalopoda—General Features—Endoceratoidea—Actinoceratoidea—Nautiloidea—Bactritoidea pp. K383–K457. The Geological Society of America and the University of Kansas Press.
[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.