These represent slightly different reconstructions of the same animal. It is challenging to try to provide realistic yet thought provoking reconstructions, especially regarding skin color, texture, and soft tissue. The coloration and patterning of most animals fall into a few broad catagories including camouflage, disruptive patterning, and/or sexual display. The animal featured here is most likely a carnivore and thus was provided with more of a disruptive pattern that would allow the animal a mechanism to distract prey by making the body outline hard to see, and thus distance and speed difficult to judge. The upper reconstruction adds hypothesized soft parts including a 'dewlap' and other features which may or may not have been present, and thus are speculative yet feasible for display.
As long as Jeff is willing, I hope to provide more of these new reconstructions in the future.
REFERENCES
Martz, J.W. 2002. The morphology and ontogeny of Typothorax coccinarum (Archosauria, Stagonolepididae) from the upper triassic of the American Southwest. Unpublished M.S. thesis. Texas Tech University, Lubbock.
Parker, W.G. 2008. Description of new material of the aetosaur Desmatosuchus spurensis (Archosauria: Suchia) from the Chinle Formation of Arizona and a revision of the genus Desmatosuchus. PaleoBios , 28:1-40.
Looks like my favorite Triassic archosaur: Effigia! If it is, I like the bottom reconstruction better. You don't see too many crocodilians with dewlaps.
ReplyDeleteWell, we don't see too many bipedal crocs with beaks either :) I figured if the osteology (and probably the lifestyle) of these critters was that different from extant crocodilians, there was room to play with the soft tissue.
ReplyDeleteI also need to throw in a disclaimer about the Argentavis reconstruction; the actual bird drawing was taken from a Scientific American(?) article. I was instructed just to clean it up, but I decided to play with the colors and add the background, so technically that one is only partly my work.
Bill - any reason why you consider shuvosaurids to be "probably carnivorous"?
ReplyDeleteThey appear very fleet with a sharp beak, probably taking small prey and possibly even carrion. They could have been omnivorous or exclusively herbivorous; however, one of its closest relatives, Arizonasaurus, is carnivorous so it is more parsimonious to consider other poposaurs to be carnivorous as well, or at least omnivorous. Of course, Lotosaurus may mess this up this hypothesis...
ReplyDeleteThe tranformation from carnivory to omnivory/herbivory has to occur at some point. And it has happened several times within Archosauria. I don't know what you mean by a "sharp beak" - what animals have a dull beak? There are plenty of herbivorous turtles with sharp beaks.
ReplyDeleteWhen appealing to parsimony for reconstructing ecology, you can't simply make outgroup comparisons. You have to take into consideration what the anatomy is telling you as well.
I don't have a strong opinion about whether shuvosaurids are carnivorous, omnivorous, or herbivorous, but I think the evidence is pretty ambiguous for carnivory.
What is the evidence for strict herbivory? I guess you can use ornithomimids as a comparison, which are believed to be herbivorous and even possible filter feeders! Maybe shuvosaurids had gastroliths as well. Other diet possiblities are eggs, invertebrates....
ReplyDeleteAetosaurs are just as problematic. Different tooth morphologies and dental formulas. Loss of premaxillary teeth in some taxa. Often three distinct taxa (from different clades)in the same quarries suggesting some type of partitioning (beyond sexual dimorphism). What were they doing?
I've always found it interesting how every major Late Triassic quarry in the SW US contains the usual suspects...some type of non-dinosaurian ornithodiran, a coelophysoid, aetosaurs, phytosaurs, a crocodylomorph, Postosuchus, Vancleavea, and a shuvosaurid. Attritional assemblage or some serious niche partitioning?
I'm not necessarily advocating strict herbivory. But full herbivory evolved at least twice in non-avian archosaurs - sauropods and ornithischians. Other taxa that were probably either herbivorous or omnivorous are ornithomimids, therizinosaurs, Silesaurus, and Revueltosaurus. And thats not even mentioning notosuchian crocodyliforms - some of which were probably pretty serious herbivores.
ReplyDeleteIncidentally, I think Barrett (2005) makes a convincing argument that ornithomimids weren't filter feeders.
Barrett, P.M. 2005. The diet of ostrich dinosaurs (Theropoda: Ornithomimosauria). Palaeontology 48(2):347-358. DOI: 10.1111/j.1475-4983.2005.00448.x
Unambiguously determining diet in extinct animals is difficult, and especially so for many Triassic animals. If there are strict herbivores what are they eating? There are no flowering plants, grasses, fruit, etc.. Groundstory is ferns, treeferns, cycads and horsetails. Trees are all conifers but the foliage is unknown.
ReplyDeleteVery few extant animal use any of these as a foodsource. Moose and Grouse are some of the few animals that include conifer needles as a significant part of their diet. Deer will eat conifer needles, but only when they are starving. Conifer needles have been found in the stomachs of mammoths but as I've told my students, last meal remains may not be indicative of true diet. The animal may have resorted to eating such things during the final stages of starvation (like conifer needles and deer) or maybe the last meal was the cause of the creature's demise.
I'm not aware of any extant tetrapod animal that eats ferns and/or cycads, instead they are strongly avoided due to their toxicity, yet supposedly dinosaurs partook. Horsetails are edible, but how sustaining are they? Plus they were limited to certain environments and thus rare. Maybe Triassic conifer foliage was more palatable, but this is ambiguous as well.
Given this, I am amazed that full herbivory evolved several times. Either the groundstory was less toxic or many of these extinct taxa were better able to handle it.
I'm still leaning more towards omnivory than pure herbivory in the critters listed above, which would include some carnivory. Obviously, there would be a range with some taxa closer to each end.
With regard to the idea that extant animals don't feed upon conifers, this is from a forthcoming paper (Butler et al., in press):
ReplyDelete"Recent work on the nutritive value of cycad foliage has indicated that it is a poor source of energy, and it has been suggested that it might have represented a less important food source for Mesozoic dinosaurs (and, in particular, sauropodomorphs) than other contemporary vegetation, such as horsetails, araucarian conifers and angiosperms (Hummel et al., 2008). Mustoe (2007: p. 6) stated that “the only [extant] creatures known to consume cycad foliage with no discernable ill effects are a few types of insects, including Lepidoptera larvae that utilize cycasin absorbed during feeding as a defence against predators”. However, Schneider et al. (2002: p. 291) noted that “native herbivorous mammals (for instance kangaroos in Australia) feed in their natural habitat also on the leaves of local cycads but seem not to suffer”. Goode (1989) noted that African porcupines feed upon stems of several species of Encephalartos, while Schneider et al. (2002) further noted that the pulp of cycad stems is consumed by African birds and hyraxes, despite the fact that these stems are rich in toxins....evidence indicates that a wide range of mammals and birds act as cycad seed dispersers in modern ecosystems, including mockingbirds, hornbills, louries, emus, parrots, corvids, cassowaries, kangaroos, baboons, monkeys, hyraxes, squirrels, flying foxes, elephants, deer, bears and peccaries. These organisms span a broad range of body sizes, and some (e.g. elephants, emus, cassowaries, hornbills, flying foxes, kangaroos, deer, etc.) are potentially able to disperse seeds over large distances."
A large number of mammals and birds do therefore incorporate at least some parts of cycads into their diets, although information on this is hard to get in the literature. I haven't gone into the literature on ferns and conifers in the same depth, but I wouldn't be that surprised to find more examples of animals that feed upon them.
Hummel et al. (2008) demonstrated that many gymnosperms (e.g. Gingko, Araucariaceae & other conifers) and ferns have energy values that are only a little lower than angiosperms, and that these are plausible possibilities for sauropod diets. Maybe the reason that we see relatively few animals eating non-angiosperm plants today is that angiosperms dominate modern floras so dramatically.
Forgot to mention. Bill asks how sustaining are horsetails? Hummel et al. said this:
ReplyDelete"From a nutritional point of view, the data predict that herbivorous dinosaurs in a pre-angiosperm world would have preferred Equisetum above all other food sources"
Richard,
ReplyDeleteThanks for you great comments. I am looking forward to your paper. As you know it is a subject that it is hard to find good information on.
Bill
The case could be made for carnivory but I personally feel the animal was probably strictly herbivorous based on the mandible structure.
ReplyDelete