Petalodus12 Posted January 20, 2020 Share Posted January 20, 2020 Hi all, I have seen and heard from multiple different sources that the cephalic spines of Xenacanthid sharks are considered to have been venomous. This is usually supported by the serrated nature of these spines and a canal that runs down the middle of them. Has any research been done to prove or disprove this hypothesis. I know that we can never know for sure but I am curious if there is any scientific support to these claims. Thanks in advance, Zach Link to comment Share on other sites More sharing options...
Darktooth Posted January 20, 2020 Share Posted January 20, 2020 I am curious to find this out myself. I like Trilo-butts and I cannot lie. Link to comment Share on other sites More sharing options...
fossilsonwheels Posted January 20, 2020 Share Posted January 20, 2020 I researched this for our education programs and I could not find a study that could provider any proof. I am not saying there is not one out there but as far as I could find, it is just a theory. 3 Link to comment Share on other sites More sharing options...
connorp Posted January 20, 2020 Share Posted January 20, 2020 I have seen this claim before but haven't found a reference either. From the perspective of modern fish, it is certainly a possibility. Several fish today have spines on the body which are venomous and can be extended to make the body harder to swallow, both of which discourage predators. 2 Link to comment Share on other sites More sharing options...
fossilsonwheels Posted January 20, 2020 Share Posted January 20, 2020 To expand on what Connor said, there are some extant sharks with venomous dorsal spines. The Spiny Dogfish, possibly other too I don’t know, and two Heterodontus sharks, Port Jackson and Horn Shark, are venomous. So it’s possible this evolved in ancient sharks. 1 Link to comment Share on other sites More sharing options...
connorp Posted January 20, 2020 Share Posted January 20, 2020 Also, I don't think a venomous nature of the spines could ever truly be verified. I doubt any trace of a venom would be fossilized. Of course, we have to speculate a lot in paleontology, but my point is that I don't think there's a smoking "venomous" gun. For all we know, the canal in the middle could be a remnant from an ancient ancestor that served no purpose in xenacanths. 3 Link to comment Share on other sites More sharing options...
fossilsonwheels Posted January 20, 2020 Share Posted January 20, 2020 29 minutes ago, connorp said: Also, I don't think a venomous nature of the spines could ever truly be verified. I doubt any trace of a venom would be fossilized. Of course, we have to speculate a lot in paleontology, but my point is that I don't think there's a smoking "venomous" gun. For all we know, the canal in the middle could be a remnant from an ancient ancestor that served no purpose in xenacanths. I think that is an excellent point Link to comment Share on other sites More sharing options...
doushantuo Posted January 20, 2020 Share Posted January 20, 2020 someofyoumaylike Morphology and histology of dorsal spines of the xenacanthid shark Orthacanthus platypternus from the Lower Permian of Texas, USA: Palaeobiological and palaeoenvironmental implications KIMBERLY G. BECK, RODRIGO SOLER-GIJÓN, JESSE R. CARLUCCI, and RAY E. WILLIS Acta Palaeontologica Polonica, 61(1):97-117 (2016). 5 Link to comment Share on other sites More sharing options...
Petalodus12 Posted January 20, 2020 Author Share Posted January 20, 2020 @connorp @fossilsonwheels @doushantuo thank you for the replies. I figured that there would be no way to prove or disprove this, because, as you guys said, the chemicals that would be responsible would not be preserved. Thank you all again for the information, it was very helpful Link to comment Share on other sites More sharing options...
jdp Posted January 20, 2020 Share Posted January 20, 2020 Just a note about the figure-8 shaped cross sections: this is a structural feature of a lot of long and narrow structures that resist force in one primary axis. You see a similar figure-8/hourglass shape in the neural spines of Dimetrodon as well as a range of other things. There are mechanical reasons for this. The fact it creates the appearance of a channel is just a side effect of this. 2 Link to comment Share on other sites More sharing options...
Pemphix Posted January 20, 2020 Share Posted January 20, 2020 As said: this will be not solved, cause there's no scientific prove (and probably will never). Link to comment Share on other sites More sharing options...
Petalodus12 Posted January 20, 2020 Author Share Posted January 20, 2020 So I guess that the general consensus is that the claim of venomous spines on Xenacanthid sharks is erroneous and impossible to actually prove or disprove. My thought is that this belief stemmed from the superficial resemblance of these spines to those of extant sharks and rays, which are venomous. The belief seems pretty widespread though, so hopefully others who are curious find this thread and have their questions at least somewhat answered. Thank you all again for the informative replies. Link to comment Share on other sites More sharing options...
Uncle Siphuncle Posted January 20, 2020 Share Posted January 20, 2020 Are there any spines similar in structure on extant species known NOT to be venomous? Grüße, Daniel A. Wöhr aus Südtexas "To the motivated go the spoils." Link to comment Share on other sites More sharing options...
Coco Posted January 20, 2020 Share Posted January 20, 2020 Recent Centrophoros squalosus has a spine on the dorsal fin, but I don’t think it’s poisonous. Squalus acanthias also has them.They may not look like Xenacanthid’s. I can do a pic if you are interested in but actualy it is the night. Coco 1 ---------------------- OUTIL POUR MESURER VOS FOSSILES : ici Ma bibliothèque PDF 1 (Poissons et sélaciens récents & fossiles) : ici Ma bibliothèque PDF 2 (Animaux vivants - sans poissons ni sélaciens) : ici Mâchoires sélaciennes récentes : ici Hétérodontiques et sélaciens : ici Oeufs sélaciens récents : ici Otolithes de poissons récents ! ici Un Greg... Link to comment Share on other sites More sharing options...
fossilsonwheels Posted January 20, 2020 Share Posted January 20, 2020 4 minutes ago, Uncle Siphuncle said: Are there any spines similar in structure on extant species known NOT to be venomous? Yes. Squalidae have dorsal fin spines and most are not venomous as far as I know. The Spiny Dogfish is venomous and that is the only one I can say I know is venomous. There could be others as it is a large family 1 Link to comment Share on other sites More sharing options...
fossilsonwheels Posted January 20, 2020 Share Posted January 20, 2020 Though I should note I am not sure how similar in structure they are. I think there may also be members of Heterodontus whose spines are not venomous. I know Horn and Port Jackson sharks are but I don’t know about the rest of that order. Link to comment Share on other sites More sharing options...
Coco Posted January 21, 2020 Share Posted January 21, 2020 Hi, These spines are hollow. Coco 6 ---------------------- OUTIL POUR MESURER VOS FOSSILES : ici Ma bibliothèque PDF 1 (Poissons et sélaciens récents & fossiles) : ici Ma bibliothèque PDF 2 (Animaux vivants - sans poissons ni sélaciens) : ici Mâchoires sélaciennes récentes : ici Hétérodontiques et sélaciens : ici Oeufs sélaciens récents : ici Otolithes de poissons récents ! ici Un Greg... Link to comment Share on other sites More sharing options...
Archie Posted January 21, 2020 Share Posted January 21, 2020 In the specimens Ive found the canal runs down the length of the spine but does not seem to extend through the denticles/barbs. 3 Link to comment Share on other sites More sharing options...
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