Synechodus

{{Short description|Fossil genus of cartilaginous fish}}

{{automatic taxobox

| fossil_range = {{fossilrange|Late Triassic|Palaeocene|earliest=Cisuralian}}

| image = Synechodus.png

| image_caption = Skeleton of Synechodus ungeri (JME SOS 3152 B) from the Late Jurassic of Solnhofen, Germany

| image2 = Synechodus dubrisianus tooth.jpeg

| image2_caption = Tooth of Synechodus dubrisianus

| taxon = Synechodus

| authority = Woodward, 1888

| type_species = Hybodus dubrisiensis

| type_species_authority = Mackie, 1863

}}

Synechodus is an extinct genus of shark belonging to the family Palaeospinacidae and order Synechodontiformes. It is known from 16 species primarily spanning from the Late Triassic to Paleocene.{{Cite journal |last1=Villalobos-Segura |first1=Eduardo |last2=Stumpf |first2=Sebastian |last3=Türtscher |first3=Julia |last4=Jambura |first4=Patrick L. |last5=Begat |first5=Arnaud |last6=López-Romero |first6=Faviel A. |last7=Fischer |first7=Jan |last8=Kriwet |first8=Jürgen |date=March 2023 |title=A Synoptic Review of the Cartilaginous Fishes (Chondrichthyes: Holocephali, Elasmobranchii) from the Upper Jurassic Konservat-Lagerstätten of Southern Germany: Taxonomy, Diversity, and Faunal Relationships |journal=Diversity |language=en |volume=15 |issue=3 |pages=386 |doi=10.3390/d15030386 |issn=1424-2818 |doi-access=free|pmid=36950327 |pmc=7614348 }} The dentition is multicusped and was used for grasping. Several species are known from skeletal remains, including the species Synechodus ungeri from the Late Jurassic of Germany, which shows that it was relatively short with large pectoral fins and a proportionally large head with a round snout. This species is suggested to have reached a body length of {{Convert|30-40|cm|ft}}.{{Cite journal |last=Klug |first=Stefanie |date=2009-06-12 |title=A new palaeospinacid shark (Chondrichthyes, Neoselachii) from the Upper Jurassic of southern Germany |url=https://www.tandfonline.com/doi/full/10.1671/039.029.0203 |journal=Journal of Vertebrate Paleontology |language=en |volume=29 |issue=2 |pages=326–335 |doi=10.1671/039.029.0203 |bibcode=2009JVPal..29..326K |s2cid=130292129 |issn=0272-4634}} Skeletal remains are also known of the species Synechodus dubrisiensis from the Cretaceous of Europe.{{Cite journal |last1=Sokolskyi |first1=Tymofii |last2=Guinot |first2=Guillaume |date=January 2021 |title=Elasmobranch (Chondrichthyes) assemblages from the Albian (Lower Cretaceous) of Ukraine |url=https://linkinghub.elsevier.com/retrieve/pii/S0195667120302895 |journal=Cretaceous Research |language=en |volume=117 |pages=104603 |doi=10.1016/j.cretres.2020.104603|bibcode=2021CrRes.11704603S }} A skeleton of an indeterminate species is also known from the Early Cretaceous (Albian) of France, with a body length of around {{Convert|70|cm|ft}}.{{Cite journal |last1=Mollen |first1=Frederik H. |last2=Hovestadt |first2=Dirk C. |date=2018-12-20 |title=A new partial skeleton of a palaeospinacid shark (Neoselachii, Synechodontiformes) from the Albian of northern France, with a review of the taxonomic history of Early Cretaceous species of Synechodus Woodward, 1888 |url=https://bioone.org/journals/geodiversitas/volume-40/issue-4/geodiversitas2018v40a25/A-new-partial-skeleton-of-a-palaeospinacid-shark-Neoselachii-Synechodontiformes/10.5252/geodiversitas2018v40a25.full |journal=Geodiversitas |volume=40 |issue=4 |pages=557 |doi=10.5252/geodiversitas2018v40a25 |issn=1280-9659}} Synechodus is suggested to have had two dorsal fins that lacked fin spines,{{Cite journal |last1=Klug |first1=Stefanie |last2=Kriwet |first2=Jürgen |date=May 2008 |title=A new basal galeomorph shark (Synechodontiformes, Neoselachii) from the Early Jurassic of Europe |url=http://link.springer.com/10.1007/s00114-007-0341-0 |journal=Naturwissenschaften |language=en |volume=95 |issue=5 |pages=443–448 |doi=10.1007/s00114-007-0341-0 |pmid=18196213 |bibcode=2008NW.....95..443K |s2cid=8460659 |issn=0028-1042|url-access=subscription }} though the number of dorsal fins is unknown in Synechodus ungeri.

The remains of the oldest known Synecodontiformes from the Early Permian of Russia have been assigned to the genus as the species Synechodus antiquus,{{Cite journal |last=Ivanov |first=Alexander |date=2005-08-30 |title=Early Permian chondrichthyans of the Middle and South Urals |url=http://www.sbpbrasil.org/revista/edicoes/8_2/8(2)ivanov.pdf |journal=Revista Brasileira de Paleontologia |volume=8 |issue=2 |pages=127–138 |doi=10.4072/rbp.2005.2.05}} though other authors have considered its attribution to the genus doubtful,{{Cite journal |last1=Rees |first1=Jan |last2=Campbell |first2=Hamish J. |last3=Simes |first3=John E. |date=2023-05-21 |title=The first Triassic elasmobranch teeth from the Southern Hemisphere (Canterbury, New Zealand) |url=https://www.tandfonline.com/doi/full/10.1080/00288306.2023.2214369 |journal=New Zealand Journal of Geology and Geophysics |language=en |pages=1–8 |doi=10.1080/00288306.2023.2214369 |issn=0028-8306 |s2cid=258840273|url-access=subscription }} with other authors considering attribution of all other pre-Jurassic species to genus being questionable.{{Cite journal |last1=Klug |first1=Stefanie |last2=Kriwet |first2=Jürgen |date=September 2010 |title=A new Late Jurassic species of the rare synechodontiform shark, Welcommia (Chondrichthyes, Neoselachii) |url=http://link.springer.com/10.1007/s12542-010-0058-9 |journal=Paläontologische Zeitschrift |language=en |volume=84 |issue=3 |pages=413–419 |doi=10.1007/s12542-010-0058-9 |bibcode=2010PalZ...84..413K |s2cid=129213049 |issn=0031-0220|url-access=subscription }}