Its Mesozoic siblings get a lot more attention, but the Triassic is here to put its place on the map. Get your Triassic map featuring 18 notable creatures as a framed print or poster.
Are the dinosaurs from the Jurassic and Cretaceous too mainstream for you? Your heart may belong to the weirdo reptiles from the Triassic. Show your love with this mug featuring Triassic oddity Longisquama.
Dicynodonts were members of a diverse clade of non-mammalian therapsids. They survived the Great Dying and ranged from rat to elephant-sized. This is Ischigualastia, from Argentina.
Time and Place: Sometime between 215 and 203 million years ago, from the Norian to the Rhaetian ages of the Late Triassic
Found in the Laguna Colorada Formation of Santa Cruz, Argentina
Physical Description:Mussauruswas a fairly late “prosauropod” dinosaur, a group of dinosaurs that would one day evolve into sauropods (and, thus, the term “prosauropod” is only a useful convention, rather than a proper animal group name). As a prosauropod closely related to Sauropods proper, it also had bulky body size, a long neck, and well muscled limbs to support its bulk. However, it was primarily bipedal; showing a lack of musculature in the back associated with quadrupedalism. It was possibly able to walk on all fours if the situation demanded it. As a baby, however, Mussauruswas an obligate quadruped; and it transitioned to a primarily bipedal stance as it aged. In addition, Mussaurusin general shows a decent mosaic of traits associated with Sauropods and those associated with their ancestors; a transitional form on the evolution of this iconic group of dinosaurs. Mussaurusshowed arched finger bones and robust hands bones, as well as stronger lower arm bones, which showcased the development of traits that would allow quadrupedal walking. They also had shorter hands, like in Sauropods, indicating they weren’t being used as much for grabbing food as in earlier “prosauropods” and thus were available to be used for walking. Finally, Mussauruswas able to passively pronate its hands (meaning, it was able to turn in its wrists somewhat), another trait that was necessary in the evolution of quadrupedal walking in the sauropod group.
In addition to these typical traits for its group, Mussaurusdiffered from other prosauropods in having a thin plate along the middle of the vertebrae of the trunk - a trait usually only seen in more early prosauropods, rather than a later one like Mussaurus- having a differently shaped shoulder, and having oddly curved foot bones. This probably indicates some sort of difference in the need of Mussaurusto utilize its back, as well as holding up its weight with its feet; though its difficult to say much more than that. In general, Mussauruswas about three meters in length, though it probably didn’t get much taller than a person when standing on two legs.
The integument of Mussaurusis unknown, though given its generally smaller size, it probably was covered in some form of protofeathers.
By I. J. Reid, CC BY-SA 3.0
Diet: As a medium sized herbivore, Mussaurusprobably mainly browsed on low to medium levels of vegetation. Its hands, however, were probably not used in grabbing food; instead it mainly utilized its head in gathering food from branches and the undergrowth.
Behavior:Mussaurusmainly fed using its head and long neck, using the length of its neck to reach into foliage and gather food where it otherwise would not be able to reach. Unlike earlier prosauropods, it would not have used its hands as much to gather food, though it still could probably use them in the pursuit of plant material from time to time. As a biped, it would have walked on two limbs when needing to go faster, and potentially used a quadrupedal posture to aid in standing upright while feeding and in other more leisurely pursuits.
By Wandering Nork
Mussaurusis primarily famous for being originally named after infant individuals; these babies were only about 37 centimeters in length, about the size of a small lizard. They had taller heads than the adults, with short snouts, and larger eyes. It is probable, given that dinosaurs in general take care of their young, that this rendered the babies cuter to the adults, helping to trigger parental instincts. As such, Mussaurusprobably lived in groups at least during the early stages of life, with the adults taking care of the babies until they were old enough to take care of themselves. It is uncertain whether or not Mussauruslived in groups as adults.
Ecosystem: The Laguna Colorada Formation was a warm, wet environment; filled with ferns, Ginkgos, and other plant species. These smaller plants were also surrounded by conifer trees, indicating that Mussaurusmainly lived in a forest ecosystem. At least one other dinosaur is known from the area - a Heterodontosaurid herbivore, though little more is known about it. As such, though something must have preyed upon Mussaurus, we have no fossil evidence as to what.
Other:Mussauruswas originally named for its small size, given the first fossils of the animal were babies. However, Mussaurusclearly did not stay the size of a mouse; and now, the name is a misnomer. Still, Mussaurusprovides extensive information on the growth sequence of prosauropod dinosaurs in the Triassic period.
Time: 201.3 million years ago, in the Rhaetian age of the Late Triassic of the Mesozoic of the Phanerozoic
Analogy: Did you ever play on a team in High School? Even like an academic one? I was on my school’s Science Olympiad team (always won a medal in fossils, thank you very much. I also was in charge of organizing bio events, no big deal). Anyway do you remember when, like, the upperclassmen graduated, and suddenly you had a lot of responsibility and you were an important member of whatever club or team you were on? Like, they disappeared, and you got to take their place and be the big guys? Yeah that’s this, but for dinosaurs.
Causes: Where did we leave off? Oh right nearly everything died. My favorite! Well life eventually did recover after the Permian Extinction - obviously, as we’re all here today. Archosauromorphs were really taking over the scene, and there we many different kinds everywhere - dinosaurs were a relative minority compared to all the other different types of reptiles, and pterosaurs were extremelyrare as well. Nothosaurs, Pachypleurosaurs, Placodonts, and the first Plesiosaurs evolved; there were Thalattosaurs, and Ichthyosaurs were verysuccessful in the Triassic. There were many amphibians, Rhynchosaurs, Phytosaurs, Aetosaurs, Rauisuchians, the first Crocodylians, Prolacertiformes, the earliest turtles, and the cynodonts all evolved and diversified, with cynodonts getting closer to being mammals. In fact, looking at the assemblage of the Triassic, one could hardly guess that it would be dinosaurs that would become the dominant megafauna of the Mesozoic period - various Pseudosuchians (crocodile-line Archosaurs) seemed to be taking that role.
So what happened then? After all, this is pretty quick after the last death machine - only about fifty million years. Well, the causes of this extinction are actually… not very clear. Once again people have tried to pin it on an asteroid - which would make somesense, since it was the large non-dinosaurian archosaurs that were hit the hardest - but no such crater has been found, and all possible candidates have been ruled out. There was some climate change and sea level fluctuations, but they weren’t sudden enough to explain the extinctions in the ocean - this was a very sudden pulse of death, more so than what you would expect from just gradual environmental fluctuations.
Theremayhave been some massive volcanic eruptions again - yay! more lava! - which seems to be the best bet. The flood basalts of the Central Atlantic Magmatic Province would have released carbon dioxide, sulfur dioxide, and aerosols, causing - once again - pretty terrible global warming and cooling. There seems to be evidence for a major CO2 greenhouse crisis in ocean extinction deposits, and evidence that both the marine and terrestrial extinctions happened at once, which may indicate that a sudden influx of carbon dioxide and accompanying warming caused the extinction. However, there’s a chance that the eruption of the CAMP was too old to have caused the extinction.
If it was the volcanic activity, perhaps exacerbated by already occurring climate change, then the increase in global temperatures would have had another terrible effect on life on the planet - which had just recovered, and thus would be fairly vulnerable.
Extinction Rate: This was not as bad of an extinction pulse as the last one, so if it was volcanic activity, it was the kind notin the worst possible place ever. Hooray! 23% of all families, 48% of all genera, and 70 to 75% of all species went extinct.
Effects: This was actually more acutely felt in the terrestrial environments than in the marine ones, though they were also affected. A large portion of the non-dinosaurian Archosauromorph groups went extinct, which emptied ecological niches on the land extensively. In the ocean, there seemed to just be less diversification - a decrease in speciation events rather than an extinction of already existing taxa. Phytosaurs and Aetosaurs were completely wiped out, as well as others.
If we can call any time periods much of anything, then, the Triassic was truly the age of reptiles, with a wide variety of forms and diversity across different major clades. One could argue, then that this age ended after the Triassic extinction - though many reptiles remained very common, it was really more specifically the Age of Dinosaurs after this point. Dinosaurs evolved to fill the vacant niches and finally started growing to the sizes to which we are accustomed with them - sauropods started evolving (at last, from stinking prosauropods), large theropods began to grow more and more common, and Ornithischians also finally had a chance to diverge.
In fact, the rapid pulse of diversification of dinosaurs after the end-Triassic extinction lead to a large morphological diversity of dinosaurs, and at some point between the middle and late Jurassic epochs, the earliest members of Avialae evolved - the group that would eventually lead to birds.
Mammals also evolved in the Early Jurassic, probably due to pressures following this extinction event. They remained small predators, living in regions where there was still many places to hide, though they did diversify somewhat, and more so than previous paleontologists believed.
So, though a relatively minor extinction, it once again directly lead to the world we know and love today - mammals became a thing, dinosaurs grew into what we really know and love about them (widely diverse and weird, because birds are weird you guys,) and other reptiles began to dominate the sea and air (hellooooo pterosaurs, pterosaurs everywhere). In fact, dinosaurs were so versatile and widely morphologically diverse following the Triassic extinction, thanks to all those sweet, sweet available niches, that they were very well adapted to their world.
