In the Late Jurassic (around 150 Mya) of the USA, famous dinosaurs such as Allosaurus, Stegosaurus, Apatosaurus (= Brontosaurus), and Brachiosaurus were roaming the American west. Running around their feet, and doing their best not to get trampled, was a tiny dinosaur named Fruitadens haagarorum, named by Butler and colleagues in 2010). Fruitadens was a tiny, plant-eating dinosaur from the group known as heterdontosaurids.
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| Artist’s reconstruction of Fruitadens ( by Smokeybjb, and licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.) |
Heterodontosaurids were a group of plant-eating ornithiscians related to iguanodontids (like Iguanodon) and hadrosaurids (like Parasaurolophus and Edmontosaurus), among others. These dinosaurs were commonly fairly small, and had "fangs" towards the front of their mouths.You should be able to see the fangs if you look close enough at the reconstruction. They actually get their name from their strong heterodont dentition. Even so, their morphology is relatively generalized, suggesting more of an omnivorous lifestyle, with plants, insects, and some other small organisms making up the majority of their diets.
Fruitadens was named based on a few individuals (4), but the holotype consists of incomplete jaws, several vertebrae, and partial hind limbs of a nearly full grown individual. This was sufficient, however, to determine that it was, indeed, something unique and new.
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| Reconstructed skull of Fruitadens (Butler et al., 2012) |
Fruitadens was estimated by Butler et al. (2010) to have only been about 28 cm long (less than a meter) and weighed less than 1 kg (less than 2 lbs)! That size estimate is quite incredible, especially for a dinosaur that is thought to be nearly full-grown. Overall size would have probably not changed at all, or at least very little, once it became fully mature!
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| Full-size Fruitadens haagarorum model with co-author Luis Chiappe (from AP). |
But why bring this up now if this dinosaur was named in 2010? In the original publication, Butler et al. (2010) were unable to go into much detail regarding the description and morphology of this new taxon. But a new, thorough study just published by Butler et al. (2012) has given this small dinosaur its descriptive due. The new study seeks to document this dinosaur in great detail, giving new information not only on Fruitadens, but also on the whole heterdontosaurid family of dinosaurs. This study helps us understand a group of dinosaurs that were not very well known before, and helps clarify a picture that can seem somewhat blurry at times (or all the time...).
This seems to be an excellent example of a taxon that was named in a relatively short paper, but then had a follow-up study to give us a much clearer picture of exactly what it was/is. Too often taxa (not just dinosaurs) are named in short papers or with short blurbs. Little detail is given, and sometimes proper diagnoses are not even provided. I can't tell you how many times I have come across taxa and, when going to the original publications, I find little information other than the name itself. And, going a step further, often times little work has been done on the taxa after the initial publication. This was far worse decades ago and has gotten better since, but various examples can be found still today (e.g. Atrociraptor) with little work done on the taxa themselves and more work done regarding their inclusion in cladograms.
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| Depiction of some of the largest known hadrosaurs and, therefore, some of the largest known ornithischians, with a adult male for scale |
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| Depiction of Fruitadens haagarorum, with a portion of an adult male for scale |
References:
Butler RJ, Galton PM, Porro LB, Chiappe LM, Henderson DM, Erickson GM (2010) Lower limits of ornithischian dinosaur body size inferred from a diminutive new Upper Jurassic heterodontosaurid from North America. Proceedings of the Royal Society B 277: 375–381.
Butler RJ, Porro LB, Galton PM, Chiappe LM (2012) Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS ONE 7(4): e31556. doi:10.1371/journal.pone.0031556
Hey Steve this is Jeremy How do we know these little guys aren't just babies? Have actual nesting sites been found that have contained actual eggs or fossilized off spring from them? If so how big are the eggs? Do you think that the Fruitadens were nest scavengers? What I mean is do you think that while hanging out with the bigger dinosaurs that they didn't feed on their eggs?
ReplyDeleteIs it correct for my understanding of this to be that most dinosaurs or what has been referred to as taxa do not have a complete dialog of research behind each of them, and that they have only been classified together as just hederodonts with the exception of the frutadens haagarorums? How does this work?
DeleteHello Steve. this is Amanda Milstead. What other types of small dinosaurs were around during this time? Is the Fruitadens the smallest dinosaur ever discovered? You mention the fact that the Fruitadens is a heterodont and ate mainly plants with some insects and other small organisms thrown in. What do you think the fangs were used for? I noticed the eye socket on the skull reconstruction was fairly large. Why would the Fruitadens need superior eyesight?
ReplyDeleteJeremy-They are known to be less than full grown (but not juveniles or hatchlings) due to the amount of fusion in the elements recovered. This is a relatively common practice with fossils. With enough work, one gets an idea of the amount of fusion different elements undertake throughout ontogeny (aka from hatchlings till full adulthood). This fusion is commonly present in the cranial elements, but can also be found in post-crania. As an example, many mammals have their epiphyses unfused to the ends of their long-bones when young, but these become fully fused later on in life. Its also known that few animals survive until they become fully adult, and the majority of those die when young. Combining that with the incompleteness of the fossil record means that few fully adult fossils may be found, but there are ways to tell roughly how old an animal was when it died (at least sometimes). Fossil eggs and nests have not been found from these guys, but that doesn't mean they are not adults. In fact, while a good number of fossil eggs (or egg shells) and nests have been found, its very hard to tell what animal those came from. As an example, you can search online for Oviraptor. This animal was first found on a nest of eggs, and its name means "Egg theif", although it was later found that it was actually on its own eggs and was probably a loving parent. Fruitadens could have possibly scavenged on eggs if it had to though. Little is known of its actual biology (as is the case with most dinosaurs) and many animals will not hesitate to do whatever they must to survive, there is just no direct evidence for that. Being small, it may have been able to scoot around and steal the eggs of others, although it may have just as easily (if not more so) been able to scurry around the feet of larger herbivores and eaten the food they dropped or helped to fall.
ReplyDeleteJeremy (Part 2)-I don't think I completely follow what you are saying or asking here. Many dinosaurs have not been fully reviewed or studied though. Often times dinosaurs have been named, with the concentration just being getting the name out, with little further study on the rest of the material. This could mean that a dinosaur was named based on a really interesting skull, but any post-crania that was part of the specimen was never fully examined or discussed. Almost all dinosaurs would not be considered homodont, at least in the way that a fish or many amphibians would be. Although size will normally be the major differences in the teeth of each species or type. Some, like Oviraptor and its relatives (most oviraptorosaurs) did not have teeth and instead had a beak. Heterodontosaurids have even more variation in their teeth, which is why the family got its name.
If you have any further questions or follow-up questions, feel free to ask.
Thanks you explained a lot. To follow up just a little...is the Oviraptor possibly related to the Fruitadens? Also you say that there have been no confirmed nesting sites..not to say that they don't exist..is it possible to say that they shared the nests with the other dinosaurs. Would be a very good defense position should any predators come around. They wouldn't have to do much but hide under the big guys. You said that there is an extensive fossil egg shell archive...did you mean that there is no record of the type of egg the Fruitadens lay or did you mean that there is no way to determine which egg shell fossils marry with which dinosaur?
DeleteOviraptor ends up being a theropod within the Saurischia that is closely fairly closely related to birds, while Fruitadens was a heterodontosaurid within the Ornithischia. A small dinosaur like this may have shared a nest with larger dinosaurs or others in general. While much larger dinosaurs probably would no have sat on their nests, they certainly may have watched over them, in which case a small plant-eater may have sought refuge within or around the nests of larger dinosaurs. Commonly it is very hard to tell exactly which egg came from which dinosaur. Sometimes it can be determined that an egg cam from a certain type of dinosaur, say from a sauropod, but further ID gets difficult. Sometimes eggs have been found with embryos still inside and this is one of the only ways to be certain that the egg belonged to an exact type of dinosaur. There is also evidence of nesting sites (e.g. Oviraptor, Protoceratops, Maiasaura), and this helps show that some dinosaurs had sites full of many nests for a group or herd. I don't know of any direct evidence of other dinosaur species nesting within these sites, but it is a very interesting hypothesis that could potentially be tested.
DeleteAmanda-By this it may depend on what you consider small. While various large dinosaurs were around then, like Brachiosaurus, Apatosaurus, Diplodocus, Supersaurus, Camarasaurus, Allosaurus, Torvosaurus, Stegosaurus and Camptosaurus, there were various small dinosaurs around then too. Archaeopteryx was around then, and grew to less than 2 feet in length, although this may depend on whether one considers it one of the earliest birds, or one of the most bird-like dinosaurs. Compsognathus was a very small theropod, growing to 1 m or less, during the Late Jurassic. Moving into the Early Cretaceous, Microraptor also grew to less than 1 m, and was a feathered raptor from China. Essentially, after going through this, the idea is that Fruitadens is the smallest known ornithischian (most herbivorous dinosaurs), but there are quite a few just as small and smaller saurischians (theropods or the meat-eating dinosaurs and the sauropods, or long-necked dinosaurs). As a simple suggestion, I would suggest that the fangs were probably for display rather than for acquiring food. I don't believe, however, that this has ever been tasted in any way. The orbits are quite large as well, and it implies that eyesight was quite important for this dinosaur. As a note, the dinosaur Leaellynasaura, from the Early Cretaceous of Australia, has very large orbits, and it has been interpreted as a way to allow this small plant-eating dinosaur to be nocturnal and active at night. Its large eyes would help it pick up moonlight and presumably avoid various large predators that would be active during the day. This is also just a suggestion, but intriguing nonetheless.
ReplyDeleteIf you have any further questions or follow-up questions, feel free to ask.
I think that it is amazing that these little guys were even able to live during this time period with dinosaurs like the Brachiosaurus, Apatosaurus and Diplodocus. I would imagine that they had fear of getting stepped on by other larger dinosaurs. So, I am also assuming that this is probably the smallest dinosaur ever known to be recorded? If so, I am very surprised that this discovery was just made. Like you said at the beginning of your post that some people believe that dinosaurs could have been quite small compared to what we are guessing. How can we be sure of the size other than bone? How can we be sure it was not a baby or fetus even if that and the mother's bones just were not preserved?
ReplyDeleteInteresting stuff!
-Rachel Curcio
Geology 1051-003 Life Through Time Lab
Rachel - while it seems like there would always be a danger of getting stepped on, there were undoubtedly quite a few small animals that were around then. Think about an ecosystem today, with a few very large animals, but many medium and small animals. It would have been similar then, with relatively few of the larger ones, but probably quite a few of the smaller animals. Even so, I'm sure accidentally getting stepped on was always on their minds when they were around the larger dinosaurs. Dinosaurs are separated into two main groups (Saurischia and Ornithischia). There are a number of as small, and perhaps even smaller, saurischians. This is, however, considered the smallest ornithischian, a group containing the plant eating duck-billed dinosaurs (hadrosaurs), the frilled Triceratops and its relatives (ceratopsids), and Stegosaurus and its relatives, among various others. While the discovery of new dinosaurs has slowed down to a point, there are many regions and time periods left to dig up and this means that many new types of dinosaurs (and other animals) will eventually be discovered. With most fossils, paleontologists can only use the bones and various aspects of them to decide on size and age. The amount of fusion of the bones can help tell you how old something is. Hatchlings commonly have very little fusion, and more places and more bones fuse, along with more locations on those bones, throughout life. With that being said, the researchers can tell that Fruitadens was a sub-adult (something like a teenager would be). It was either full-grown or very nearly full-grown.
ReplyDeleteHi Steve, this is Autumn Huffman. This is really interesting because I've never really thought about small dinosaurs. Reading this has made me wonder why there wern't lots of them even smaller than these. I mean look at how many small mamals we have today, I would think that it would have been more similar to the animal world today. Also what would their habitat have been like to survive all the pressures from the big dinosaurs if there wern't many other small ones like these? Where they significantly smaller at "birth" and if so how did they survive?
ReplyDeleteAutumn - you are right in your idea that there would be plenty of small, and smaller, dinosaurs around. As one looks more in depth at the fossil record, one finds that the smaller an animal is, the less likely one is of being preserved. If less of them are preserved, then chances are exponentially smaller of finding and digging one of them up. This can also deal with the young or hatchlings, whose bones are even more fragile and less likely to be preserved. I am certain that their would have been plenty of very small dinosaurs, and I am sure that their were smaller ones around then what has been found. Similar to habitats and ecosystems of today, their are normally less large animals, but lots of very small animals. Size certainly matters in that aspect. Their habitat has commonly been considered very scrubby, with numerous shrubs and trees. Grasslands hadn't really evolved yet. Even so, they may have used a lot of underbrush and shorted bushes and such for cover. They undoubtedly would have been much smaller at birth. Based on evidence I have found from other dinosaurs, I'm sure hatchlings would have been quite small, probably smaller than a sparrow
DeleteThats so weird. Imagine if those things were around today. I want to know what do you think about the lizards of today. Are they just small dinosaurs that have to walk on four legs? I still really don't understand the difference between an animal like this and a lizard or something. It seems like the only difference is the walking on two feet.
ReplyDeleteClint Riddle
I saw your comment, Clint, and figured I’d chime in. It’s a good question: What makes a dinosaur different from a lizard?
DeleteKeep in mind that not all dinosaurs walk on two feet (Triceratops, Stegosaurus, etc.) and there are some lizards that can run on two feet for a short while (like the Australian Frilled Lizard). But there IS a difference in the way they walk. Dinosaurs walk with their legs directly beneath them, like most mammals, whereas lizards have a sprawled posture, with their legs bent out to the side. The upright posture of dinosaurs is probably part of what allowed them to grow to such great sizes – legs directly beneath the body can support greater weight. Dinosaurs, birds, and the early relatives of crocodiles all share this trait, while lizards have always been “sprawlers.”
There are other differences between dinosaurs and lizards. Lizards (and snakes) have specialized scales, different from the scutes that dinos and crocs have, and they also have special joints in their skulls which allow them to bend their jaws in complex ways – the extreme version of this is, of course, the snakes, who can expand their skull to swallow large prey. Dinosaurs (also crocodiles and pterosaurs) have less jointed skulls, but have extra openings in the skull, and also have teeth that fit into sockets (like mammals), which lizards and snakes do not have.
David
Clint, indeed David has covered this quite well. Dinosaur, in fact, means "thunder lizard" as when they were first found they were thought to be very large lizards.
DeleteThis is Danny Downs, I was just wondering what environmental factors allowed for the differention of size during the time of the dinosaurs. While I know the availability of food allowed for larger organisms, I was more wondering why the difference in size of reptiles during this period was so vast compared to the difference in size of reptiles and mammals currently?
ReplyDeleteDanny - This is actually a great question that has been discussed without a definite answer. It is known that it would have been warmer during the time of the dinosaurs, and this could have factored into their ability to grow larger. Warmer temperatures could mean better resources and more food. More food (i.e. plants) for herbivores could let them get larger and, in turn, allowed or forced carnivores to grow larger. Often times it can end up being an "arms race", with both herbivores and carnivores trying to grow large enough to not get eaten or to be able to eat anything and everything.
DeleteAnother key point is probably that competition plays a key role. Today, mammals have taken on more of the "larger vertebrates" role in most ecosystems. Reptiles have become mostly smaller and taken on different roles as well. In the Mesozoic, however, dinosaurs fulfilled that "large vertebrates" role. Mammals at that time played more of the "small vertebrates" role. The difference in dinosaurs versus large mammals today deals more with temperature and resources. Why they got so extreme though is still being debated.
So what was the Fruitaden's diet? I imagine animals that small would travel in large packs, due to the fact that they are probably very easy prey to some other animals living at that time. No matter the size, I feel like a pack of those guys could still take down a larger animal, because they look like the would be very quick and vicious.
ReplyDeleteCooper - I believe you are undoubtedly correct in that these animals would have traveled in packs. Animals that small may have peen in herds and had lookouts to watch for wary predators. And while they are heterdontosaurids and would have eaten a wide variety of things, there teeth were not set-up to eat large amounts of meat or be even mainly carnivorous. They may have eaten very small things, little mammals or lizards and insects, along with a diet of mainly plants. So I don't see these little guys pack-hunting any other large or larger animals. Things like Velociraptor, who was also quite small, probably no taller then your waste, would have been pack-hunters and probably hunted things far larger than themselves.
DeleteI have learned there was a bigger amount of oxygen which allowed dinosaurs to be bigger
ReplyDelete