Dicynodonts Part Three
Willem is a wildlife artist based in South Africa. He says "My aim is simply to express the beauty and wonder that is in Nature, and to heighten people's appreciation of plants, animals and the wilderness. Not everything I paint is African! Though I've never been there, I'm also fascinated by Asia and I've done paintings of Asian rhinos and birds as well. I may in future do some of European, Australian and American species too. I'm fascinated by wild things from all over the world! I mainly paint in watercolours. . . but actually many media including 'digital' paintings with the computer!"
Let's wrap up the dicynodonts. If you read the previous two articles (here and here) you should have a good idea of what a dicynodont is. If you don't want to bother reading those: dicynodonts are a group of proto-mammals, that is to say the group from which mammals evolved, but before they were proper mammals. Dicynodonts themselves were not ancestral to mammals, but were a very diverse and numerous group in their day, yielding a huge number of fossils especially in South Africa. Many studies are currently being done on dicynodonts, teaching us much about the early evolution of proto-mammals. Most of them lived in the Permian (from about 270 to about 252 million years ago) but a substantial number also made it into the Triassic, and they lived until the end of that period, about 201 million years ago. All dicynodonts as far as we figure were herbivores, but some small species might also have eaten insects. They went extinct probably as a result of predation by and competition with the first of the big dinosaurs. Dinosaurs came to dominate the ensuing periods, the Jurassic and the Cretaceous. There have been very fragmentary fossils from the Cretaceous claimed to be from dicynodonts; if so this will be a remarkable case of late survival. I'm not making any bets myself but it would be extremely cool if true.
In shape, the dicynodonts were rather similar, all having large barrel-bodies with sturdy limbs. Here's a reconstruction of the pig-sized Tanzanian species Tetragonias njalilus just to remind you. This species has a rather long tail compared to most other dicynodonts. It lived in the Triassic. The original mount I reconstructed this from is really confusing for having a tiny head – most dicynodonts had quite large heads for their bodies. What happened is that the museum paired the skull of a juvenile with the body of an adult! I consider that very poor form. People going to museums should be seeing things represented as close to 'real' as possible. They are supposed to be educational institutions and need to care about truthfulness and accuracy. I hope I fixed the problem well enough here, giving it a head more appropriate to its body.
Now we'll finish off with a bunch of dicynodont faces. They're not to scale in the pictures, instead all reproduced similar in size to properly show the details. Also, seeing as how I've been mentioning the possibility of dicynodonts being furry, I've reconstructed some of them with fur (mostly the smaller species) and others smooth-skinned. In our first picture, we see four dicynodonts in which the canine 'tusks' were absent but replaced by sharp-edged ridges of the horny beak. The Scottish species Geikia elginensis ('Geikie's critter from Elgin') is at the top left. Sir Archibald Geikie was the Director-General of the Geologic Survey in the late nineteenth Century, and Elgin is the town in Scotland near which its fossils were found. This one lived in the Permian and is one of a very few Scottish proto-mammal species known. It was small, about the size of a cat or small dog. It is remarkable for its short face and the ridges protruding above its almost vertically-oriented snout. It's possible that this skull belonged to a juvenile and that the adult would have had different proportions. It has also been suggested that, with its large eyes, it was partially or fully nocturnal. A close relative was found in Tanzania.
Top right is Ischigualastia jenseni ('Jensen's critter from the Ischigualasto Formation'), one of the largest species, reaching over 3.5 m in length. This one lived in South America, its fossils being found in Argentina. It lived in the late Triassic, about 230 million years ago.
Bottom left is Placerias hesternus, 'Broad Body of the West'. This one was related to Ischigualastia, but found in North America still in the Late Triassic but slightly later, 221-210 million years ago. It was also quite large, reaching 3.5 m in length. Placerias had remarkably long extensions to the edges of its horny beak. In the place of the tusks of other species, these formed a cutting edge which, along with the edge of the lower jaw, was used to snip off bits of vegetation. This one is known from many fossil skeletons from Arizona and North Carolina.
Shown at the bottom right, another large species, Jachaleria candelariensis ('Jachaler's critter from Candelària City') was found around the same time in Argentina and Brazil.
Our next picture shows a few large dicynodonts that still had their tusks. Top left is Daptocephalus leoniceps (I don't know what 'dapto' means but 'cephalus' is head and 'leoniceps' means lion-head). This was a large species from the South African Late Permian, with huge flanges at the rear of its skull for the attachment of strong jaw muscles. It must have been able to feed on quite tough plant food in the dry climate it lived in. The species lent its name to a specific assemblage of fossils including many more proto-mammal species in the Karoo region of South Africa.
Top right is Moghreberia nmachouensis. Its name refers to places in Morocco, where it was found, and I can't get additional details. It lived in the Triassic, and had a high crest on its skull, for the attachment of jaw muscles.
Bottom left is Sinokannemeyeria pearsoni ('Pearson's Kannemeyeria from China'). Kannemeyeria proper ('Kannemeyer's critter') is a similar, well-known species from South Africa. Sinokannemeyeria was also large, but had weaker jaw-closing muscles than other species, shown by its not having such prominent bone crests and flanges in its skull. It had huge bulbous protuberances at the front of its snout from where its canines emerged. It might have been semi-aquatic, wading and tearing up soft aquatic plants with its jaws. It lived in the Triassic, between 247 and 242 million years ago.
Bottom right is Rabidosaurus cristatus (sorry, I can't find out what its genus names means, but its species name means 'crested'). This one lived in Russia in the Triassic, about the same time as Sinokannemeyeria. The high bony crest it had on its skull likely also served to attach jaw muscles.
Our final picture shows species both with and without canine teeth. Top left is Pelanomodon moschops, 'calf-faced mud-Anomodon' (remember that dicynodonts are all Anomodonts). It was a small to medium-sized species. It was characterized by big knobby bone protrusions above its nostrils and eyes. It was related to Geikia (see above) and Aulacephalodon (see previous article). Its skull was low and very wide. It lived in South Africa in the Late Permian, 259-252 million years ago.
Top right is Rastodon procurvidens, 'forward-pointing tooth from (the Rio de) Rasto (formation)'. It was a small species, about cat-sized. It is known from a skull with a small and forward-curving canine tooth, unique in the family. It lived in South America during the Late Permian.
Bottom left is Dicynodontoides recurvidens (recurved-tooth like Dicynodon). This one is sometimes named in the genus Kingoria. It was a small species with a low skull and a short face. It seems to have fed on soft plant food. Its skeleton shows that it was a faster runner than other dicynodonts, with its hind legs oriented almost vertically. It lived in the Late Permian, 259-252 million years ago, in South Africa.
Bottom right is Rhachiocephalus behemoth (behemoth column-head), which lacked canine teeth but had forward-pointing, sharp projections from its beak instead. It was one of the largest of Permian dicynodonts, reaching 2.5 m/8' in length with a skull over 60 cm/2' long. It lived in South Africa.
That wraps up the dicynodonts, for now. There are many genera and species I haven't discussed or mentioned, and as I say, they are targeted for study at the moment, so new information is coming in all the time. I hope something positive about their furriness and possible warm-bloodedness turns up soon. Until then, I hope I have given you a good idea of the diversity and variability of the group. Next, we look at the fearsome gorgon-faces, the last side-branch group we'll have a look at until we tackle the main-branch of mammalian evolution, the cynodonts.