Underwhelming Fossil Fish of The Month: February
By Mark Carnall, on 12 February 2013
February, when the days of winter seem endless and no amount of wistful recollecting can bring back any air of summer. Author Shirley Jackson
Ahh February, the month of love. Valentine’s day, leap year proposals and an early pay day. However, there’s one group of animals who don’t care much for February and that’s fossil fish. They’re dead and fossilised. Even if they weren’t they lack a language processing centre in their brain and February wasn’t invented until 700BC. For a fossil fish things like February don’t matter. But what does matter is this month’s Underwhelming Fossil Fish of the Month and this month we’re selling out with some corporate sponsorship tie-in.
This month, to celebrate the opening of the Micrarium, the UFFoTM for February is this rather lovely looking slide, one of the 2323 microscope slides on display in the Grant Museum, showing the cosmoid scales of Megalichthys sp. .
As you can see it looks like this slide was transferred from UCL’s Geology Department and what it shows is cosmoid scales. “Cosmoid scales?” you say, but my favourite kinds of scales are ganoid and placoid, leptoid at a push. Sadly, true cosmoid scales (scales with a layer of cosmine) went extinct with the majority of lobe finned fish. Coelacanths, poster child for living fossils, have modified cosmoid scales.
Megalichthys quite simply means big fish from the Greek words mega and ichthys. From whole body fossils we know they could reach sizes of up to 2m long. In my book that makes it a large-ish fish but not big. Megalichthys was alive during the Carboniferous period, between 345 and 300 million years ago and was probably predatory on smaller fish. Megalichthys specimens (or specimens attributed to Megalichthys) are numerous and held in the collections of many many museums.
Preservation As this is a section of a fossil I tip my hat again to the technique and hand skills in preparing specimens like this from solid rock. If my reading of this slide is correct what we can see is a cross section through scales showing the different layers from left to right in the orientation pictured. That’s not a bad level of detail for a 300 million year old fish scale.
Research From a quick literature search it looks like if you’re in the business of fossil fish then name dropping Megalichhys will get you into the coolest and most exclusive palaeontological books, journals and conferences. Nearly everyone who is anyone in palaeontology has had a hand in Megalichthys. Megalichthys has a science celebrity father, a specimen spotted in Leeds Museum was the type specimen (the name bearing) for this new genus described by Palaeontologist Superstar Louis Agassiz and for a long time this genus was seen as an animal sharing both fish and reptilian characters. However, due to some rather vague descriptions and some typographical errors by William Buckland and Richard Owen what was and wasn’t Megalichthys became unclear. Fortunately, in 1966 UCL zoologist Keith Stewart Thomson, ended years of suffering by making a case for the stabilisation of the name Megalichthys to the International Commission on Zoological Nomenclature (Thomson 1966). Given that this particular specimen was found or prepped in 1958 here on campus could this have been the specimen to spur Thomson on to resolve the ongoing confusion?
Like other UFFoTM stablemates, Megalichthys features in evocatively titled publications such as On Some New and Little Known Paleozoic Vertebrates by Edward Drinker Cope (he of ‘Bone Wars’ fame) and the gripping read List of Palaeozoic Fishes. It seems to be a go-to fish featuring in the Alfred Romer textbooks about vertebrate anatomy and evolution. D.M.S Watson, Master of the Fossil Fishes also makes a cursory reference, in particular on the brain case of this genus (Watson 1926). Megalichthys is mentioned in this obituary of zoologist Edwin Stephen Goodrich and the genus even gets a mention in Vestiges of the natural history of creation, the anonymous publication that allegedly spurred Charles Darwin on to publish On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. However, at least one scholar doesn’t find Megalichthys underwhelming. In an 1849 paper on the microscopic structures of scales, W.C.Williamson describes Megalichthys scales as “….some of the most complicated and beautiful structures I have yet seen amongst the ganoid fish…” (Williamson 1849). Presumably a hotly contested title. Most recently, Megalichthys also carries the dubious distinction of being one of a handful of extinct lobe-finned fish to have otoliths preserved (Clack 1996). It seems that Megalichthys may be the Kevin Bacon of fossil fish if those obnoxious adverts are to be believed.
In Society I got through the first 14 pages of a popular web search engine’s search results and the only result for Megalichthys that wasn’t a scientific paper, museum database listing or those nonsense dictionary and rhyming sites that come up regardless of what you search for was this video of A LIVING MEGALICHTHYS.
In Society 0
Cope, E. D. On Some New and Little Known Paleozoic Vertebrates. Proceedings of the American Philosophical Society , Vol. 30, No. 138 (Apr., 1892), pp. 221-229