Underwhelming fossil fish of the Month December 2016
By Mark Carnall, on 31 December 2016
2016 was the most overwhelmingly underwhelming year of the last twelve months.
But it wasn’t the only thing that disappointed in month by month instalments. Yes, of course I’m talking about the Grant Museum of Zoology’s underwhelming fossil fish of the month blog series. The monthly foray into the drawers and drawers of underwhelming fossil fishes at the Grant Museum brings you the finest worst selection of least best fossil fish. We ask the tough questions such as why are these fossils here? Which way around is this one supposed to go and what does this label say. This is the blunt edge of science right here.
Of course, I’ve got an especially unspecial fossil fish to round off the year. Vast expense was spared to bring you just another underwhelming fossil fish to mark one step closer to your inevitable end. First up though, it’s END OF YEAR ROUND-UP FILLER CONTENT.
January’s fish was lovingly labelled, February’s fossil was rather revealing. Nobody noticed that the March one went missing. April was a staple, albeit without a scale. May was almost sway and June’s fish came from far away*. We went arty in July darling avecs Placodermes De La Terre. In August, I bored us (stoppit!) with an odus to Gyrodus. September was just okay actually. After an enigmatic October, November rolled right into the end of the world and the fish with no name. Which brings us neatly onto this month’s fossil fish. Snack your eyes on these ever so slightly out of focus fossils:
Here they be, just
four three teeth confusingly identified as Diplodus sp. collected from the Permian of Texas by Underwhelming Fossil Fish of the Month Hall of Famer, D.M.S Watson. I say confusingly, not just because your mind wants to read Diplodus as Diplodocus but because Diplodus is a genus of living sea bream who: do not have teeth like this and whose fossil record only goes as far back as the Eocene (roughly 50-30 million years ago) which is 200-250 million years after the as-advertised-on-the-label Permian. Something fishy is going on and remarkably can you believe this is the first time I have used that joke in this 40-something-long series? Wow.
What we have here readers, is a classic case of FOSSIL FISH TAXONOMY TOM FOOLERY and like most FOSSIL FISH TAXONOMY TOM FOOLERY we can trace it back to legendary fish palaeontologist, Louis Agassiz. The name was used in 1843 by Agassiz to describe teeth found in Carboniferous and Permian rocks in association with spines from freshwater sharks called xenacanthidans. Unfortunately, the name was already in use for sea bream in 1810 by another author and ever since then both names seem to co-exist, which you may remember from lessons about taxonomy and classification at school, shouldn’t happen at all. Generic names, at least within animals should be unique. Here’s Diplodus with reference to Carboniferous sea bream fish on the Palaeobiology database and here it is with reference to living sea bream on the World Register of Marine Species. In other words, its a mess and these
four three teeth aren’t likely to be from Diplodus at all as we shall see.
Preservation Although we appear to have a selection of nice three dimensionally preserved shark teeth here, if I am interpreting these fossils correctly, each of the
four three teeth has a key bit missing to be very misleading. As the below image shows better, these teeth should have two cusps like these images show forming a pronged tooth which is distinctive for this group.
If I’m correct (78% certainty) then these are teeth from a xenacanthidan fish, freshwater sharks that lived from the Carboniferous to the Triassic which now makes more sense with the label for these specimens. These V shaped teeth were thought to have been used for eating hard scaled fish and crustaceans.
Research The Bat Computer is coming up with an almost total blank on any particular research direction for xenacanthidan sharks as a group beyond, “they were around, I guess”.
In Society Remarkably and presuming when they were really running out of animals to choose from, the 43rd episode of River Monsters, quality wildlife programming as you can tell from the name, featured Xenacanthus, a xenacanthidan shark. FULL DISCLOSURE: I’ve not seen the episode, it was this Wikipedia article that drew my attention to it. FULL FULL DISCLOSURE: I probably won’t see it either.
4 3 Xenacanthida Teeth
In Society 3
* Note to self before publishing- work out whether this section will rhyme or not. DO NOT LEAVE IT as kinda rhyming sometimes.
Mark Carnall is the Collections Manager (Life Collections) at the Oxford University Museum of Natural History, and former Curator of the Grant Museum