Underwhelming Fossil Fish of the Month: November 2013
By Mark Carnall, on 22 November 2013
How are the cockles of your heart? In need of some warmth? Here’s the latest Underwhelming Fossil Fish of the Month (all the others are here). Eagle-ray eyed readers won’t be able to read this with both eyes because eagle-rays have monocular vision. Eagle eyed readers will have no doubt spotted a slight change. As this is the 13th month of uninspiring amorphous rocks resembling, organisms which were formerly fish, I’ve added a date after the blog title because Akheilos forbid you get confused between ‘seasons’ denying yourself the available UFFotM goodness.
To kick off season 2, I’ve prepared nothing special. Fossil fish don’t discriminate between or celebrate such arbitrary occasions, it is in their honour that we maintain that composure. Prepare to lose five minutes of your life. No returns or resales.
Look at this beautiful hunk of rock.
What you’re looking at here is the tooth of an extinct lungfish, identified as Ceratodus sp. Some of you trendy fashionable youthful types may know the more recent living relative, Neoceratodus forsteri, the Australian lungfish. This specimen proves once and for all that newer is not always better as it’s much bigger than the teeth of Australian lungfish and it’s an established scientific fact that bigger is always better*. Ceratodus and Neoceratodus are two genera of lungfish, fish adapted to breath air with lungs which are homologous with the lungs in tetrapods (which includes us), that is to say, that lungfish have lungs but they don’t have the same lungs as us. Lungs. What a weird word.
Ceratodus fossils are found in rocks deposited in the Triassic up until the Cretaceous, apparently vanishing about 70 million years ago. This specimen doesn’t have any locality information with it which means narrowing down the species might be quite tricky. Adult lungfish have crazy marginal teeth like this one which sit horizontally in the mouth with the ‘spiky bits’ pointing outwards not like the teeth of most vertebrates which sit vertically in the jaw. The below image of a Grant Museum specimen of the Australian lungfish shows the marginal teeth rather nicely. Developmental studies of the Australian lungfish record that newborn lungfish have ‘normal’ teeth which are lost when these big bony tooth plates erupt and when this happens they change their diet from feeding on small aquatic invertebrates to a wider omnivorous diet (Kemp 1995).
Preservation Hard parts like teeth have a much higher chance of preservation in the fossil record than other squishier bits and fossils like these are often the only trace of these organisms we have. Although not inherently sexy themselves a bit of soft lighting with tantalizing shadows can significantly do wonders.
Research Ceratodus has been extensively researched over the years, probably as a consequence of a small number of species representing a discrete group of animals. Plus, with these fish closely related to our little group of animals the human interest tends to lead to more research. One particularly exciting paper is titled ‘A mysterious king-sized Mesozoic lungfish from North America’ (Shimada and Kirkland 2011). Sadly, that paper is behind a paywall which means it will remain a mystery as will the definition of king-sized. Fossil fish fans who are also fans of shows like Jackass can get their niche crossover fix in yet another paper by Kemp in 2001, ‘Consequences of traumatic injury in fossil and recent dipnoan dentitions’, complete with gory images of lesions and skewed cusps. Ceratodus is also mentioned in passing by Chucky D in the On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. Although sadly back then Ceratodus was the name for the Australian Lungfish as well as fossil species.
In Society In a very round about way I discovered that Ceratodus was one of the words that James Murray, the primary editor of the Oxford English Dictionary, fought to keep in the dictionary especially as it was one of the genera that Darwin mentions in the Origin of Species (Mugglestone 2005). Useful information for those time travellers who like to take, Scrabble time travel edition with them. Lungfish in general are one of those groups of animals that many people will know about. They’re also one of the groups of animals that embody the idea of a ‘living fossil’ a misleading phrase but a compelling idea.
In Society 3
Kemp, A. 1995. Marginal Tooth-Bearing Bones in the Lower Jaw of the Recent Australian Lungfish, Neoceratodus forsteri (Osteichthyes, Dipnoi). Journal of Morphology 225:345-355.
Kemp, A. 2001. Consequences of Traumatic Injury in Fossil and Recent Dipnoan Dentitions. Journal of Vertebrate Paleontology , Vol. 21, No. 1 (Mar. 26, 2001), pp. 13-23
Mugglestone, L. 2005. Lost for Words: The Hidden History of the Oxford English Dictionary. Yale University Press.
Shimada, K and Kirkland, J.I. 2011. A mysterious king-sized Mesozoic lungfish from North America. Transactions of the Kansas Academy of Science. Vol. 114, No. 1/2 (Spring 2011), pp. 135-141
Mark Carnall is the Curator of the Grant Museum of Zoology
* Strictly in the who-would-beat-who in a fight context. And the chunky Kit-Kat context. Examples of things which aren’t normally better when they’re bigger: car crashes, pain, earthquakes, traffic jams, holes, debt, earth bound asteroids and episodes of Eastenders.