Dinosaurs are awesome, the very nature of the name Dinosauria is pretty badass, even for the realms of Linnaean classification, after all the name means “terrible lizards”. Though now we have finds of such unnerving cuteness as Microraptor gui (right), the name may be a little silly. That however is another blog-post altogether, so I’ll leave it for another day.
My love of ancient life and palaeonotology was sparked off by dinosaurs, and like a true geek I still have all the old VHS tapes (yes… I remember VHS) that set me off on my way to where I am today, including one entitled “Dinosaurs: Fun Fact and Fantasy” which I was amazed to find the whole programme floating about on YouTube, so here you go… a little dinosaur quiz for you with the show’s puppet-crocodilian host; Dill…
Anywho, childhood memories aside, I now live in Lyme Regis. This small Dorset town is famous for many things, John Fowles’ ‘French Lieutenant’s Woman’, and thanks to the film adaptation also the town’s iconic Cobb Harbour being just two of them.
The town is far more famous however for its fossil material, indeed I’ve mentioned it before on this blog. Mary Anning and her contemporaries supplied many of the first scientifically recorded and described examples of marine reptiles like Ichthyosaurs and Plesiosaurs. The town even boasts a Dinosaur, Scelidosaurus harrisonii, which was first discovered by a local quarryman – James Harrison of Charmouth – in the cliffs of Black Ven in 1858 and was named and described by Professor Richard Owen of the British Museum (Natural History Dept.) in 1863.
What’s really interesting about the animal is that since that time only nine specimens had ever been discovered eroding out of the cliffs near Lyme Regis, and they tell us an awful lot about the area.
These nine fossil animals are all found within one particular horizon within the Black Ven marls, this being a layer of “topstones” or hard limestone blocks within the marl sequence, though as they’re found already eroded from the cliff (usually on the beach in their own blocks) no one’s particularly sure which of the two topstone bands the dinosaurs come from. Equally the Scelidosaurs are all found within a very short stretch of the beach, always at Black Ven, never anywhere else, even though the same rocks crop out in Yorkshire, some 280 miles away in Northern England.
This does tell us some interesting things though, firstly it tells us exactly when these dinosaurs lived (something I’ll come back to later), but secondly it tells us that land was very close by at this time in the distant past. Why does it tell us this? Well these dinosaurs are land animals, they did not venture into the sea, and certainly would not have done so as a group, so they had to have died before they came to be out at sea. The suggestion being that a herd of S. Harrisonii were crossing a river on land and were swept away. Possibly by a flash flood, or possibly in the same manner as many wildebeest die when their huge herds cross African rivers, by being crushed, jostled under the waterline, and drowning.
OK, so we know that the dinosaurs came from a nearby land-mass, and we know (from the fact that they are all from the same horizon, and closely spaced) that they were probably from the same herd, but how close is that land-mass? Well again we can assume it was very close, maybe as little as a couple of miles. Why? If we assume the postulated herd-drowning hypothesis is correct, then the unfortunate creatures are swept out to sea. If they had “bloated and floated” as the local fossil collectors call it, then the tides and currents would have swept them far and wide. Instead these animals sank to the sea floor rapidly and were not scattered so we know that the land-mass from which they came is very close to the spot where they are found today.
What other evidence is there to support this? Well for a start in the rocks of black ven and in the ‘stonebarrow topstones’ we also find a lot of fossil insects, by no means as many as we do ammonites, but enough to demonstrate the proximity of land. Insects aren’t something you find in the middle of the ocean, even today, even blown out to sea by storms they don’t get far from land, so finding dead and fossilised beetles and dragonflies in the stonebarrow topstones helps add weight to our land proximity hypothesis.
Supporting the herd hypothesis is not so hard either, of the nine specimens found, many of them are near complete specimens, and of the nine, one has small horns above the eyes, while the other eight do not. There are two possible explanations for this. Firstly the one with the horns could be better preserved than the eight without, but a second possibility is that the one with the horns is exhibiting sexual dimorphism, and that the horns are some form of display or ‘rutting’ characteristic, suggesting this individual is a male of the species. Perhaps even an alpha male leading his herd to an unfortunate doom? What a nice image, if slightly sad and morbid…
Now I’ve got to admit to something here… I’ve not been wholly truthful with you. There are actually 10 specimens of Scelidosaurus harrisonii from the area around Lyme Regis… Why didn’t I mention the tenth specimen? Well basically because this individual isn’t found with the other nine. In fact this individual may be far more important that just finding another member of the herd; the reason being that this one isn’t found in either of the topstone bands, oh no. This one is found in the Stellare Bed (bed number 88f according to Lang), about one metre above the topstone beds, and therefore many many years after our unfortunate herd found its way into the ocean.
This is important because up until this tenth specimen started eroding out last year, S. harrisonii was known only from the first nine specimens at an age of 195 million years, so this one disarticulated, poorly preserved and pretty beat up dinosaur extends the range of the scelidosaur lineage.
Why do I mention it here… because while I only found this out a few days ago, I also found out that my first dinosaur bone (a partial scelidosaur vertebra I found last year) came from this animal… which considering I was pretty psyched to have found a dinosaur bone in the first place, then even more psyched to know it was from a S. Harrisonii… you can probably guess as to how freakin’ amazing I found this new information!
Sadly (from a personal perspective) I donated the bone to Lyme Regis Musuem’s geologist Paddy Howe because it was “scientifically important”… now I understand why!
Addendum: There are rumours that one of the original nine scelidosaurs may also have come from a layer other than the Stonebarrow Topstones… this I shall investigate…
There are also rumours that scelidosaurus scutes have been found in Arizona (hardened plates that lie beneath the skin)… though this is still disputed.
Website of Dr Ian M. West: http://www.soton.ac.uk/~imw/Lyme-Regis-to-Charmouth.htm
Bed numbers originally found in: Lang, W.D. and Spath, L.F. 1926. The Black Marl of Black Ven and Stonebarrow, in the Lias of the Dorset Coast. Quarterly Journal of the Geological Society, London, 82, 144-187, pls. 8-11
Thanks to Mssrs. Paddy Howe and Chris Andrew for some facts and photographs respectively