# Ptyctodontida > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Ptyctodontida > Markdown URL: https://mediated.wiki/source/Ptyctodontida.md > Source: https://en.wikipedia.org/wiki/Ptyctodontida > Source revision: 1354759171 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) Extinct order of fishes Ptyctodontida Temporal range: Devonian PreꞒ Ꞓ O S D C P T J K Pg N Reconstruction of Rhamphodopsis threiplandi Scientific classification Kingdom: Animalia Phylum: Chordata Class: †Placodermi Order: †Ptyctodontida Gross, 1932 Family: †Ptyctodontidae Woodward, 1891 Genera See text Synonyms[1] Order synonymy Rhynchodonta Jaekel 1907a Ptyctodontiformes Berg 1940b Aulacosteida Fowler 1965 Family synonymy Aulacosteidae Fowler 1947 The **ptyctodontids** ("folded-teeth") are [placoderms](/source/Placoderm) of the [order](/source/Order_(biology)) **Ptyctodontida**, containing the [family](/source/Family_(taxonomy)) **Ptyctodontidae**. With their big heads, big eyes, reduced armor and long bodies, the ptyctodontids bore a superficial resemblance to modern day chimaeras ([Holocephali](/source/Holocephali)). Their armor was reduced to a pattern of small plates around the head and neck. Like the extinct and related [acanthothoracids](/source/Acanthothoracids), and the living and unrelated [holocephalians](/source/Holocephali), most of the ptyctodontids are thought to have lived near the sea bottom and preyed on [shellfish](/source/Shellfish). On account of their radically reduced armor, some paleontologists have suggested that the Ptyctodontida were not actually placoderms, but actual holocephalians, some primitive group of [elasmobranch](/source/Elasmobranch) fish, or even were the ancestors of the holocephalians, including the chimaeras. Thorough anatomical examinations of whole fossil specimens reveal that the profound similarities between these two groups are actually very superficial. The major differences between them were that holocephalians have [shagreen](/source/Shagreen) on their skin and ptyctodontids did not, that the armored plates and scales of holocephalians are made of [dentine](/source/Dentine), and the armored plates and scales of ptyctodontids were made of bone, the anatomy of the craniums of holocephalians is more similar to sharks, and that of ptyctodontids were more similar to those of other placoderms, and, most importantly, the holocephalians have true teeth, while the ptyctodonts had beak-like tooth-plates. The Ptyctodontida were the only known group of placoderms that were recognizably [sexually dimorphic](/source/Sexual_dimorphism), in that the males had hook-like growths on their pelvic fins that were analogous to the clasping organs found in male sharks, and chimaeras. Paleontologists believe that the males of the ancestral placoderm had pelvic claspers, but the claspers were lost in the evolutionary development of each of the placoderm orders, save for the ptyctodontids (there are too few whole specimens of the primitive *[Stensioella heintzi](/source/Stensioella_heintzi)* to tell if the males of that species had claspers or not). Because they had reduced armor, the ptyctodontids were once thought to be the most primitive of the placoderms. Indeed, there has been the idea that the placoderms had a gradient, of sorts, from the least armored, and most primitive forms, to the heavily armored, most advanced forms. During the 1980s and '90's, ptyctodont skulls were compared with skulls from other orders. From these analyses, this idea of a gradient from least armored to most armored in placoderms was discarded. Now, the ptyctodonts are regarded as the sister group of the [Arthrodira](/source/Arthrodira) and [Phyllolepida](/source/Phyllolepida). ## Genera The following genera are recognized in the family Ptyctodontidae:[2][1][3] - Genus *[Austroptyctodus](/source/Austroptyctodus)* Long, 1997 - Genus *[Borysthenoplax](https://en.wikipedia.org/w/index.php?title=Borysthenoplax&action=edit&redlink=1)* Plax, 2019[4] - Genus *[Campbellodus](/source/Campbellodus)* Miles & Young, 1977 - Genus *[Chelyophorus](/source/Chelyophorus)* Agassiz, 1844b [=*Cheliophorus* Stensiö, 1969b][1] - Genus *[Ctenurella](/source/Ctenurella)* Ørvig, 1960 - Genus *[Denisonodus](https://en.wikipedia.org/w/index.php?title=Denisonodus&action=edit&redlink=1)* Johnson and Elliott, 1996 - Genus *[Desmoporella](https://en.wikipedia.org/w/index.php?title=Desmoporella&action=edit&redlink=1)* Ørvig, 1971 - Genus *[Eczematolepis](/source/Eczematolepis)* S. A. Miller, 1892a [=*Acantholepis* Newberry, 1875a; =*Phlyctaenacanthus* Eastman, 1898b][1] - Genus *[Goniosteus](/source/Goniosteus)* Gross, 1933d - Genus *[Kimbryanodus](/source/Kimbryanodus)* Trinajstic & Long, 2009[2] - Genus *[Materpiscis](/source/Materpiscis)* Long, Trinajstic, Young & Senden, 2008 - Genus *[Meeksiella](https://en.wikipedia.org/w/index.php?title=Meeksiella&action=edit&redlink=1)* Trinajstic, Long, Ivanov & Mark-Kurik, 2019[5] - Genus *[Palaeomylus](/source/Palaeomylus)* Woodward, 1891a - Genus *[Ptyctodopsis](https://en.wikipedia.org/w/index.php?title=Ptyctodopsis&action=edit&redlink=1)* Denison, 1985 - Genus *[Ptyctodus](/source/Ptyctodus)* Pander, 1858a [=*Aulacosteus* Eichwald, 1846c; =*Rinodus* Newberry & Worthen, 1866a; =*Paraptyctodus* Carter, 1942][1] - Genus *[Rhamphodopsis](/source/Rhamphodopsis)* Watson, 1934a - Genus *[Rhynchodus](/source/Rhynchodus)* Newberry, 1873 [=*Ramphodus* Jaekel, 1903g; =*Rhamphodus* Jaekel, 1906d; =*Rhamphodontus* Jaekel, 1906; =*Rhynchodontus* Jaekel, 1919a; =*Rhynchosteus* Jaekel, 1925d; =*Rhynchognathus* Jaekel, 1929b; =*Ringinia* Whitley, 1950][1] - Genus *[Tollodus](https://en.wikipedia.org/w/index.php?title=Tollodus&action=edit&redlink=1)* Mark-Kurik, 1977[6] ### Timeline of genera ## Gallery - Fin spine of the ptyctodont, *Gamphacanthus*, showing color patterns; from the Middle Devonian of Wisconsin. - Tooth plates from the ptyctodont *Ptyctodus ferox*, from the Middle Devonian of Wisconsin. Note the grinding surfaces. - Beak-like tooth plate of a ptyctodont from the Middle Devonian of Wisconsin. ## References 1. ^ [***a***](#cite_ref-Handbook_1-0) [***b***](#cite_ref-Handbook_1-1) [***c***](#cite_ref-Handbook_1-2) [***d***](#cite_ref-Handbook_1-3) [***e***](#cite_ref-Handbook_1-4) [***f***](#cite_ref-Handbook_1-5) Denison, Robert (1978). *Handbook of Paleoichthyology, Volume 2, Placodermi*. New York: Gustav Fischer Verlage. pp. 26–34. [ISBN](/source/ISBN_(identifier)) [9780895740274](https://en.wikipedia.org/wiki/Special:BookSources/9780895740274). 1. ^ [***a***](#cite_ref-Kimbryanodus2009_2-0) [***b***](#cite_ref-Kimbryanodus2009_2-1) Trinajstic, Kate; Long, John A. (September 2009). ["A new genus and species of Ptyctodont (Placodermi) from the Late Devonian Gneudna Formation, Western Australia, and an analysis of Ptyctodont phylogeny"](https://www.cambridge.org/core/journals/geological-magazine/article/abs/new-genus-and-species-of-ptyctodont-placodermi-from-the-late-devonian-gneudna-formation-western-australia-and-an-analysis-of-ptyctodont-phylogeny/F935B5502B3F8D5F2D919D5320DB0899). *Geological Magazine*. **146** (5): 743–760. [doi](/source/Doi_(identifier)):[10.1017/S001675680900644X](https://doi.org/10.1017%2FS001675680900644X). [ISSN](/source/ISSN_(identifier)) [1469-5081](https://search.worldcat.org/issn/1469-5081). 1. **[^](#cite_ref-SepkoskiJr2002_3-0)** Sepkoski Jr., J. J. (2002). ["A compendium of fossil marine animal genera"](https://www.biodiversitylibrary.org/item/40634#page/304/mode/1up). *Bulletins of American Paleontology*. **363**: 300 – via Biodiversity Heritage Library. 1. **[^](#cite_ref-Plax2019_4-0)** Plax, D. (2019). ["A NEW GENUS OF THE PLACODERM FISH (PLACODERMI, PTYCTODONTIDA) FROM THE UPPER EMSIAN DEPOSITS OF BELARUS"](https://elibrary.ru/item.asp?id=42490384). *Республиканское унитарное предприятие “Научно-производственный центр по геологии”*. **2** (51): 75–83. [ISSN](/source/ISSN_(identifier)) [1680-2373](https://search.worldcat.org/issn/1680-2373). 1. **[^](#cite_ref-Meeksiella2019_5-0)** Trinajstic, Kate; Long, John A.; Ivanov, Alexander O.; Mark-Kurik, Elga (2019). ["A new genus of ptyctodont (Placodermi) from the Late Devonian of Baltic area"](https://palaeo-electronica.org/content/2019/2490-a-new-baltic-ptyctodont). *Palaeontologia Electronica*. **22** (2). [doi](/source/Doi_(identifier)):[10.26879/890](https://doi.org/10.26879%2F890). [hdl](/source/Hdl_(identifier)):[1885/222039](https://hdl.handle.net/1885%2F222039). 1. **[^](#cite_ref-Dupret&2011_6-0)** Dupret, Vincent; Phuong, Ta Hoa; Thanh, Tong-Dzuy; Phong, Nguyen Duc; Janvier, Philippe; Clément, Gaël (May 2011). ["The skull of Hagiangella goujeti Janvier, 2005, a high-crested acanthothoracid (Vertebrata, Placodermi) from the Lower Devonian of northern Vietnam"](http://www.tandfonline.com/doi/abs/10.1080/02724634.2011.558148). *Journal of Vertebrate Paleontology*. **31** (3): 531–538. [doi](/source/Doi_(identifier)):[10.1080/02724634.2011.558148](https://doi.org/10.1080%2F02724634.2011.558148). [ISSN](/source/ISSN_(identifier)) [0272-4634](https://search.worldcat.org/issn/0272-4634). ## Further reading - Long, John A. (1996): *The Rise of Fishes: 500 Million Years of Evolution*. Johns Hopkins University Press, Baltimore. [ISBN](/source/ISBN_(identifier)) [0-8018-5438-5](https://en.wikipedia.org/wiki/Special:BookSources/0-8018-5438-5) v t e Gnathostomata Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata "Acanthothoraci" Arabosteus Dobrowlania Hagiangella Kimaspis Kolymaspis Kosoraspis Palaeacanthaspis Radotina Romundina Sudaspis Tlamaspis Weejasperaspididae Murrindalaspis Weejasperaspis Antiarchi see Antiarchi Arthrodira see Arthrodira Petalichthyida Diandongpetalichthys Neopetalichthys Quasipetalichthyidae Eurycaraspis Pauropetalichthys Quasipetalichthys Macropetalichthyidae Ellopetalichthys Epipetalichthys Lunaspis Macropetalichthys Notopetalichthys Shearsbyaspis Tongdzuylepis Wijdeaspis Pseudopetalichthyida Nessariostoma Paraplesiobatis Pseudopetalichthys Ptyctodontida Austroptyctodus Campbellodus Chelyophorus Ctenurella Denisonodus Destnoporella Eczematolepis Goniosteus Kimbryanodus Materpiscis Meeksiella Palaeomylus Ptyctodopsis Ptyctodus Rhamphodopsis Rhynchodus Rhenanida Asterosteus Bolivosteus Gemuendina Jagorina Nefudina Ohioaspis "maxillate placoderms" Bianchengichthys Entelognathus Qilinyu Silurolepis? Incertae sedis Brindabellaspis Holopetalichthys Janusiscus Minjinia Palaeospondylus? Ramirosuarezia Stensioella Xiushanosteus Crown-Gnathostomata Chondrichthyes see Chondrichthyes Osteichthyes see Osteichthyes Category Commons Taxon identifiers Ptyctodontida Wikidata: Q918188 Wikispecies: Ptyctodontidae EoL: 4655981 IRMNG: 10537 Paleobiology Database: 34262 Ptyctodontidae Wikidata: Q18618797 EoL: 4655982 GBIF: 3240818 IRMNG: 101485 Open Tree of Life: 4950031 Paleobiology Database: 307454 --- Adapted from the Wikipedia article [Ptyctodontida](https://en.wikipedia.org/wiki/Ptyctodontida) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Ptyctodontida?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.