Synechodus was a genus of prehistoric saltwater shark which lived from the early Permian Period until the late Eocene Epoch of the Paleogene Period, 290 to 37 million years ago (Ivanov 2005, pages 127-138). Fossils of this animal reached around 13 inches (34 cm) in length (“Synechodus sp.”), but it is uncertain if this was the animal’s full size.
Fossils of this animal were first found during the 1840s in what’s now the Czech Republic. It was first classified in 1863 by the British geologist Samuel Joseph Mackie as a species of the well-known prehistoric shark Hybodus. However, it was re-named in 1888 by the British paleontologist Arthur S. Woodward as a new genus called Synechodus (Woodward 1888, page 496). The name Synechodus literally means “continuous tooth” in ancient Greek (synechós = “continuous”; odoús = “tooth”), so-named because each tooth had a continuous line of small projections from one end of the tooth to the other end, with a larger point in the center.
Synechodus was the namesake genus of a group of sharks called the “synechodontiforms”. This group first appeared during the early Permian Period approximately 290 million years ago, when creatures like Dimetrodon and Edaphosaurus were walking around on land. The group went extinct during the Eocene Epoch (Krug and Kriwet 2008, page 443).
So far, twenty-five different species have been ascribed to the genus Synechodus, although some of these might be invalid. Fossils of various species have been found within marine deposits in Canada, the United States, Algeria, throughout Europe, and Japan. The evidence suggests that this genus was widely spread throughout the entire Northern Hemisphere. There are also remains ascribed to two species which were found in New Zealand within the rock layers of the Conway Formation, which dates to the late Cretaceous Period 85-66 MYA (Fossilworks. “Synechodus Woodward 1888 (elasmobranch)”; Fossilworks. “Amuri Bluff”).
Synechodus might be the same animal as another prehistoric shark called Palaeospinax. If this is true, then Palaeospinax would be the correct name because it was named first (1872 versus 1888).
Synechodus and other synechodontiform sharks had a rounded head, short flap-like pectoral fins and a single dorsal fin positioned close to the tail. Their body shape indicates that these were likely benthic sharks which spent most of their time cruising close to the sea bottom. Outwardly, Synechodus and other synechodontiform sharks bore a resemblance to another group of sharks called the “hexanchiforms”. These include the modern-day frilled shark, six-gilled sharks, and seven-gilled sharks. These sharks are widely regarded as the most primitive sharks which are alive today. However, Synechodus‘ teeth are most similar to that of the modern-day Nurse Shark (Ginglymostoma cirratum), which is a bottom-dwelling shark that feeds primarily on fish, snails, and crustaceans. Nurse sharks are recognizable for their long barbels extending near their mouths (The Ultimate Guide: Sharks). It’s possible that Synechodus and others of its kind had these features as well.
In 1985, John G. Maisey, a paleontologist who specializes in prehistoric sharks, argued that the synechodontiform sharks were more closely related to “modern” sharks than the hybodont sharks which were around at the same time (Maisey 1985, pages 1-28).
Below is an illustration which I made of Synechodus. I chose to give it a speckled camouflage coloration due to its benthic lifestyle. The barbels are artistic conjecture. The drawing was made with No.2 pencil and Crayola colored pencils on printer paper, and some digital color modification.
Synechodus. © Jason R. Abdale (April 5, 2023).
Bibliography
Articles
Ivanov, Alexander (2005). “Early Permian Chondrichthyans of the Middle and South Urals”. Revista Brasileira de Paleontologia, volume 8, issue 2 (August 2005). Pages 125-138.
https://www.researchgate.net/publication/228487527_Early_Permian_chondrichthyans_of_the_Middle_and_South_Urals.
Krug, Stefanie; Kriwet, Jurgen (2008). “A new basal galeomorph shark (Synechodontiformes, Neoselachii) from the Early Jurassic of Europe”. Naturwissenschaften, volume 95, issue 5 (May 2008). Pages 443-448.
https://www.researchgate.net/publication/5655731_A_new_basal_galeomorph_shark_Synechodontiformes_Neoselachii_from_the_Early_Jurassic_of_Europe.
Maisey, John G. (1985). “Cranial morphology of the fossil elasmobranch Synechodus dubrisiensis“. American Museum Novitates, 2804 (January 30, 1985). Pages 1-28.
https://digitallibrary.amnh.org/bitstream/handle/2246/5280//v2/dspace/ingest/pdfSource/nov/N2804.pdf?sequence=1&isAllowed=y.
Woodward, Arthur S. (1888). “On the Cretaceous selachian genus Synechodus“. Geological Magazine, 3 (5). Pages 496-499.
https://www.biodiversitylibrary.org/page/30533996#page/536/mode/1up.
Websites
Fossilworks “Amuri Bluff”. http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&taxon_no=34673&max_interval=Cretaceous&country=New%20Zealand&is_real_user=1&basic=yes&type=view&match_subgenera=1. Accessed on April 2, 2023.
Fossilworks. “Fossilworks. “Synechodus Woodward 1888 (elasmobranch)”. http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=34673. Accessed on April 2, 2023.
Mindat. “Synechodus”. https://www.mindat.org/taxon-4824998.html. Accessed on April 2, 2023.
Treatment Bank. “Synechodus sp.”. http://treatment.plazi.org/id/03D1F82F353F3E7DFBE05385FB83FAEA. Accessed on April 4, 2023.
Videos
The Ultimate Guide: Sharks. The Discovery Channel, 1996.
Categories: Paleontology, Uncategorized
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