By Mark Carnall, on 1 March 2017
Pinch, punch first (and only) of the underwhelming fossil fish of the month! For those who have made good life choices, until now, underwhelming fossil fish of the month is a monthly rummage through the drawers of the Grant Museum of Zoology, taking a look at life through the lens of an underwhelming fossil fish. Most you’ll have never heard of. Even more of them you wish you hadn’t. But someone, somewhere, sometime thought it would be important to collect, label and archive these underwhelming fossils for perpetuity.
This series questions if that was a useful thing to do. It also answers that: it probably wasn’t.
This month, we’ve got a particularly deceptive underwhelming fossil fish of the month for in all images of it, it looks much like an A-Level art student’s still life painting. We’ve been photographing it from almost every angle and the result is always the same. But don’t just take my word for it, famine your eyes on this…
In this full view, with the scale bar almost in the same postcode as the fossil, the painterly quality cannot be recognised. Here it is every so slightly zoomed in.
Don’t be fooled by this fossil’s resemblance to a burned pastie, it is a fossil. According to the ever-reliable museum label, this is a tooth plate fossil of Sagenodus sp. from the ‘coal measures’. Here’s what another slightly better Sagenodus tooth plate looks like and yup you can see the family resemblance.
As the entirety of the one line Sagenodus Wikipedia article says: “Sagenodus is an extinct genus of prehistoric sarcopterygians or lobe-finned fish”. Use of the word prehistoric aside, I’d say that’s as succinct and comprehensive as a description you could get. All the interesting angles have been covered. I can’t really compete with that so I’ll wrap it up here.
In Society 1
Just kidding! There’s plenty more to say, although be advised, almost none of it is interesting.
Sarcopterygian fish are the group of bony fish which includes the living coelacanths, cats, northern hairy-nosed wombats, 1990s pop duo PJ & Duncan, chuckwullas, hamerkops and lungfish (from a strictly cladistic point of view). Although ‘coal measures’ can be interpreted to be a range of different coal bearing rock strata, this specimen is likely to be from around 300 million years ago and knowing the biases of the Grant Museum fossil collections, probably collected in the UK. If so, then it’s likely to be Sagenodus inaequalis, the only UK species in this genus.
Preservation What we have here is a single tooth plate, a unique structure found in lungfish and their relatives. As illustrated in a previous even-less whelming underwhelming fossil fish of the month, these tooth plates aren’t like other kinds of teeth in vertebrates, these ‘teeth’ are formed on the inside of the jaw and the palate, to form a crushing plate. This fossil looks like it is one of the lower plates that would be on the bottom jaw. Although a well preserved Sagenodus tooth plate doesn’t look much different, this one does show a bit of wear, the flattened ‘ridges’ on the right hand side of the pastie in the images above, and I’m not sure if this is wear from ‘life’ or a consequence of taphonomy (how this tooth was preserved as a fossil). FUN PARTY TRICK: To differentiate between Sagenodus and related genus, Ctenodus tooth plates, Sagenodus has radially arranged ridges on the tooth plates and Ctenodus has more parallel ridges. Amaze your friends and enemies at parties with this neat trick.
Scientific Research Many of the ‘greats’ of fossil fish palaeontology (many of which I first encountered by collecting stickers for the Palaeoichthyology Attax Panini sticker book) have contemplated Sagenodus. Everyone’s favourite first director of the Natural History Museum, Richard Owen first described Sagenodus. Agassiz, Woodward, Romer and even Edward Drinker Cope took a punt at the group, creating a few synonyms along the way. Trust me when I say, none of them had much of interest to say about Sagenodus, unless technical comparisons of ridge length and spacing, ridge width/height ratios and extent of denticulation on labial margins float your boat. Sagenodus was in the running for being one of the earliest lungfishes, but newer discoveries have heavens above is anyone still reading this?
In Society I did actually have the Panini sticker book- Dinosaurs Prehistoric Animals. The excellent Love in the Time of Chasmosaurus blog has scans of some of the pages including such wonders as ‘Dinosaurs of the Air’ and ‘Dinosaurs of the Sea’ which of course, every precocious dinosaur nerd knew to be incorrect. You’ll also spot that Richard Owen was actually featured as a sticker so I was only half lying above. Being interested in palaeontology from an early age, I clearly wasn’t happy with the dodgy content of Panini’s sticker book so using duplicate stickers I had from the book, I wrote a palaeontology book, with my own more accurate and professional interpretations:
Mark Carnall is the strangest Collections Manager (Life Collections) at the Oxford University Museum of Natural History, and former Curator of the Grant Museum that ever