An ongoing dinosaur encyclopedia. I also run A Pterosaur A Day.

A Dinosaur A Day

A Field Guide To Dinosaurs




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Moving is a bitch

It’s especially hard when you do it four times in one year

Pisanosaurus mertii



NamePisanosaurus mertii 

Name Meaning: Merti & Mr. Pisano’s lizard

First Described: 1967

Described By: Casamiquela

ClassificationDinosauria, Ornithischia, Pisanosauridae 

My Twelfth Favorite Dinosaur! 

Oh look another basal dinosaur what a surprise. Pisanosaurus is considered to be the basalmost ornithischian, or at least the basalmost one known to date. It lived between 228 and 216.5 million years ago in the Norian age of the Late Triassic period. It was found in the Ischigualasto Formation in Argentina and it was a small, lightweight, bipedal herbivore about 1 meter long. Its classification has been under a lot of debate but the current consensus is that it is the oldest known ornithischian. It is only known from a single skeleton that is known from a partial skull and some teeth, some vertebrae, and other bones including part of the pubis, allowing for its classification. Given the synapomorphic character of protofeather/feather like integuments it probably was covered with them in at least some parts of its body. It lived in a volcanically active floodplain that was covered with forests and was warm and humid, but subject to seasonal rainfalls. It probably ate the vegetation of the area which consisted of ferns, horsetails, and conifers. Its major predator was probably Herrerasaurus, which was the most common predator in the area. Pisanosaurus lived right alongside therapsids, rhynchosaurus, dicynodonts, traversodontids, rauisuchians, archosaurus, Saurosuchus, and Eoraptor as well as Herrerasaurus. Herbivorous dinosaurs such as Pisanosaurus were definitely in the minority. 




Shout out goes to anonbinarywolf!

I have a Confession to Make

My tenth favorite dinosaur is Allosaurus 

which I have already done 

And my eleventh favorite dinosaur is Megapnosaurus 

which I have already done 

I’ve been sitting here at my desk debating and mulling and wondering what to do

What I will do 

Is my 12th favorite dinosaur 


Leptoceratops gracilis


NameLeptoceratops gracilis 

Name Meaning: Slender Little Horned Face

First Described: 1914

Described By: Brown

ClassificationDinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Marginocephalia, Ceratopsia, Neoceratopsia, Leptoceratopsidae

My Ninth Favorite Dinosaur!

Leptoceratops was a tiny little dinosaur, about 2 meters long, and it came from Red Deer Valley in Alberta, Canada, as well as locations in Wyoming, USA. It lived in the Maastrichtian age of the Late Cretaceous, about 66.8 to 66 million years ago, showing how even though it appears to be a more basal ceratopsian, it really was not. It probably ran and stood on its hind legs, and even though they couldn’t pronate their forelimbs, they could walk on four legs as well. It is known from several specimens, some of them complete. It was probably a herbivore, given the wear of its teeth and the depth and shortness of its jaw, which would have allowed it to have a powerful bite and chew very powerfully on tough plant matter. Since it was so short, it would have been a low feeder, eating flowering plants as well as ferns and confers. Its classification is pretty uncertain given both its shape and its late position in the time scale. 



Shout out goes to devinhoo!

While refusing to talk about Russel's dinosauroid is perfectly understandable, did you ever see Nemo Ramjet's dinosauroid? Not only it seems more plausible, it's also far more pleasant to look at. Sincerely, Anonymous

I hadn’t seen it, but now I have! It looks awesome!


Troodon formosus, T. inequalis, T. asiamericanus



NameTroodon formosus, T. inequalis, T. asiamericanus 

Name Meaning: Wounding tooth

First Described: 1856

Described By: Leidy

ClassificationDinosauria, Saurischia, Eusaurischia, Theropoda, Neotheropoda, Averostra, Tetanurae, Orionides, Avetheropoda, Coelurosauria, Tyrannoraptora, Maniraptoriformes, Maniraptora, Pennaraptora, Paraves, Eumaniraptora, Troodontidae

My Eight Favorite Dinosaur 

Troodon is famous for being one of the smartest dinosaurs based on their cerebrum to brain volume ratio, and as such its brain was comparable in part to that of modern birds. It had bony tympanic membranes in its inner ear. It also lived pretty late in the Mesozoic, from 77.5 to 69 million years ago in the Campanian to the Maastrichtian age of the Late Cretaceous. It also possibly lived later, as shown in the documentary Dinosaur Revolution. I’m not crying over the poor Troodon in that documentary. I just have a twig in my eye, or a log. It had teeth with prominent, wounding serrations, which was unique at the time of its discovery and very similar to those of herbivores, suggesting that Troodon was at least partially omnivorous. It was fairly small, only 2.4 meters long, and about 2/3 the height of an average man. It had very thin legs, implying that it could run fairly fast, raising its retractable claws up off the ground when doing so. 



The animaly Stenonychosaurus is actually another species of Troodon, and trust me, if Troodon had been able to continue to evolve and evolved sentience, it would not have evolved to look anthropormophic (like a human) as Dale Russell said.I mean seriously can you imagine a more egotistical thing to think? That the way we look is obviously the only way a sentient being can look? Jesus Mary Joseph and all the freaking saints. Yes, I grew up Catholic. Yes, I still sometimes swear like a Catholic. Please move on. Troodon is one of the most derived members of its family and pretty much with 100% certainty had feathers, given its close relationship to birds and the general feathered state of clades much more basal than Troodontidae. It was found in many different places such as the Two Medicine Formation of Montana, the Dinosaur Park Formation and Horseshoe Canyon Formation of Alberta, the Prince Creek Formation of Alaska, the Hell Creek Formation, Lance Formation, and Scollard Formation. It probably favored cooler climates given its distribution and abundance in the north and even Arctic areas. It also has possibly found more further south in the Javelina Formation in Texas and the Kirtland Formation in New Mexico. 



It probably was a predator in some form given that it had a sickle claw on its foot and good binocular vision, however it was also probably an omnivore given its teeth and the shape of its jaw, which was similar to that of an iguana (and iguanas are herbivores.) The large serrations that indicated it could eat plants are called denticles, and its grasping hands and large brain are actually characteristics shared with herbivorous omnivorous mammals like primates and the raccoon. In northern sites Troodon actually has much larger teeth than ones in southern sites, indicating that it was larger in the north and able to hunt larger animals for prey given that there were fewer tyrannosaurids up there. Furthermore, the lack of wear in the north indicates mainly soft food - so it probably just ate meat in these climates and not tough plant matter. It reached adult size in 3-5 years. 



Troodon nests and eggs have been discovered. The nests were built from sediments and were disc shapes, and had between 16 and 24 eggs. The eggs were shaped like elongated teardrops, with the tapered ends pointed downward and imbedded in the sediment. The reproductive biology of Troodon is somewhere intermediate between crocodiles and birds- the eggs were grouped in pairs which would suggest that it had two oviducts like crocodiles, unlike birds which have one; Troodon also laid eggs of medium size and medium number, unlike crocodiles who lay many small eggs, and birds who lay few large eggs. It also potentially laid eggs iteratively, laying a pair of eggs every one or two days, and delaying brooding until all eggs were laid to ensure that all of them hatched at once. The embryos had advanced skeletal development, implying that they were precocial (or, relatively mature and mobile young), and probably didn’t remain in the nest after hatching. Given the body ratio to egg volume, it actually was very likely that the males in a pair brood the eggs and the females did not, a characteristic that maniraptoran dinosaurs and basal birds probably shared. 



Again, I refuse to talk about “the dinosauroid” more than it’s a dumb, dumb concept. 


Shout out goes to free-my-wonderland!

Scutellosaurus lawleri


NameScutellosaurus lawleri 

Name Meaning: Lawler’s Little-shielded lizard 

First Described: 1981

Described By: Colbert 

Classification: Dinosauria, Ornithischia, Genasauria, Thyreophora

My Seventh Favorite Dinosaur!

I love me some more basal dinosaurs! Scutellosaurus is an early threophoran (the group that includes ankylosaurs and stegosaurs) that lived in the Sinemurian to Pliensbachian ages of the Early Jurassic, about 196 million years ago. It was bipedal, a rare trait for thyreophorans; it was closely related to Scelidosaurus, which was quadrupedal. It is in fact the basalmost thyreophoran. It was about 1.175 meters long. It was lightly built, with a very long tail that would allow counterbalance against the weight of its armored body, and it had long arms that would have allowed it to walk on all fours. Its scutes running down its body formed parallel rows. It was found in the Kayenta Formation in Arizona, USA, and is known from two individuals. It lived alongside Megapnosaurus and Dilophosaurus, which probably preyed on this little guy. 



Shout out goes to margotetsonchatphilippot!

Parasaurolophus walkeri, P. tubicen, P. cyrtocristatus


NameParasaurolophus walkeri, P. tubicen, P. cyrtocristatus

Name Meaning: Near Crested Lizard 

First Described: 1922 

Described By: Parks 

ClassificationDinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Ornithopoda, Iguanodontia, Dryomorpha, Ankylopollexia, Styracosterna, Hadrosauriformes, Hadrosauroidea, Hadrosauridae, Euhadrosauria, Lambeosaurinae, Parasaurolophini 

My Sixth Favorite Dinosaur 

There is no real need to explain why Parasaurolophus is cool. It’s one of those dinosaurs that we actually know how it sounded. It had a badass crest and complex social groups. Holy crap. It lived about 76.5 to 73 million years ago, in the Campanian stage of the Late Cretaceous. It lived in many different places - Dinosaur Park Formation in Alberta, Canada; the Kirtland Formation in New Mexico, USA, and the Fruitland Formation in Utah, USA. This is a completely iconic hadrosaur species and it was about 9.5 meters long in the largest individuals. The crest was probably used to distinguish between members of different species and of different sexes, for audible communication, and even thermoregulation. Despite its fame, it’s actually a relatively rare hadrosaur, known from a few specimens. It was a facultative quadruped, and it had high neural spines that increased the height of its back. Skin impressions are known for P. walkeri, showing uniform scales but no other structures. Its crest is connected to its nose, and may or may not have had a skin flap connecting it to the neck, though this is not confirmed. The hollowness of the crest is notable in that it would have permitted sound to pass through it.  


The type species is known from only one fossil, but the other two species have at least three specimens to their names, with P. tubicen being the largest, and having the most complex air passages in its crest. P. cyrtocristatus was the smallest, with a short rounded crest. P. walkeri had the characteristic long, unrounded crest, and longer upper arms. Charonosaurus has begun to be considered instead of a very closely related genus, another species of ParasaurolophusP. jiayensis, which would make it the first non-North American species. Parasaurolophus was present in many different habitats. In Alberta, it lived along side Centrosaurus, Chasmosaurus, Gryposaurus, Corythosaurus, Gorgosaurus, Edmontonia, Euoplocephalus, and Dyoplosaurus, and was a rare part of the fauna. 


In New Mexico, P. crytocristatus lived with Utahceratops, Kosmoceratops, Pentaceratops, Ornithomimus, and teratophoneus. The larger species P. tubicen lived with Alamosaurus, Krotsaurus, Pentaceratops, Nodocephalosaurus, Sauronitholestes, and Bistahieversor. The Kirtland Formation in particular would have been a large floodplain with many conifers. In Utah, it lived in a plateau area near the Western Interior Seaway, a large floodplain with channels and peat swamps, ponds, lakes, and highlands. it was a wet and humid climate and a very diverse environment. Parasaurolophus lived alongside dromaeosaurids, talos, Ornithomimus, Albertosaurus, Teratophoneus, ankylosaurids, Gryposaurus, Utahceratops, Nasutoceratops, Kosmoceratops, and Hagryphus.

Source: Me. This is Max (my boyfriend) playing with the Parasaurolophus model in the Field Museum. One of my favorite photos. 

Parasaurolophus would have eaten plants while chewing, with constantly replaced teeth that were packed together into batteries with hundreds of teeth. It could crop plant life with its beak, and had a narrow beak for selective feeding. It crest was definitely for multiple purposes, and it’s not sure which purpose was the most important in its evolution. Its crest changed with age and was sexually dimorphic, however the major divergences in crest shape and length have been determined as differences in species. A small tubular crest was present in juveniles, with most of the supporting bones also smaller indicating that it had not yet reached maturity. However, Parasaurolophus crests started developing at a younger crest than its relatives such as Corythosaurus, showing how its crest could get so big in its lifespan. 

Source: Me again; Field Museum fossil of P. crytocristatus 

The crest was definitively not used for an aquatic lifestyle or any sort of amphibious lifestyle, and it was not used for moving or supporting the head. It also wasn’t a foliage deflector, a weapon, for housing specialized organs or salt glands, or expanded areas of olfactory tissue, or throwing jets of chemical fire at enemies. Yes. These were all hypotheses proposed over trumpet. I’m as baffled as you are. It was for auditory and visual communication and, given its size, gave a clear visual signal. Given that the animal had large eye sockets and sclerotic rings that means it would have had acute vision and diurnal habits, sight was very important for Parasaurolophus. Based on scans of their inner ears, it was found that they had a very well developed inner ear, and could hear high frequencies, allowing them to hear the chirps of their young as well as the calls made by other members of the species with their crests. Finally, the intense vascularization of the crest would have allowed the brain to be kept cool. 


I had to. 


Shout out goes to riddikulus-darren!

<A Dinosaur A Day 


A Pterosaur A Day

will officially return

TOMORROW, August 18th>


Sue’s discovery day was yesterday… here is me and Max from a little over a year ago with her 

My favorite T. rex specimen and my favorite person 

What more could you want :)

Taking the MCAT again on Friday

Life’s kind of nuts

I’ll update when I can

I’ll go up to my 10th favorite dinosaur and then after that return to our regularly scheduled theropods

Love you all


Saltasaurus loricatus


NameSaltasaurus loricatus 

Name Meaning: Lizard from Salta 

First Described: 1980 

Described By: Bonaparte & Powell 

Classification: Saurischia, Eusarischia, Sauropodomorpha, Plateosauria, Massopoda, Anchisauria, Sauropoda, Gravisauria, Eusauropoda, Neosauropoda, Macronaria, Titanosauriformes, Somphospondyll, Titanosauria, Titanosauridae, Eutitanosauria, Lithostrotia, Saltasauridae, Saltasaurinae

My Fifth Favorite Dinosaur 

You know, I have this trend of picking favorite dinosaurs simply because they are groundbreaking or change the way we think about things - Maiasaura changed how we perceived parenting behavior, Utahraptor dromaeosaur size, Mamenchisaurus dinosaur length, Kulindadromaeus feathers. Well the same is certainly true with Saltasaurus, which brought into the foreground Cretaceous era sauropods. Prior to, it was thought sauropods were all but extinct in the Cretaceous, no longer the dominant herbivores, having lost out to hadrosaurs. However, in South America and Africa, sauropods were still the dominant herbivores. Saltasaurus was also the first sauropod found with armor (osteoderms, which lead to child me thinking that it was named Saltasaurus because it had salt on its back,) challenging the assumption that size alone protected sauropods from predators. Furthermore, it’s likely that other titanosaurs had armor too. 


Saltasaurus was found in the Lecho Formation in Salta Province, Argentina, and lived in the Campanian to Maastrichtian ages of the Late Cretaceous, about 70 million years ago. It was pretty small for a sauropod but still huge, about 12 meters long and less than 4 meters high. It had a diplodocid like head with blunt teeth in the front of the mouth, and a crest of scutes along its back. Its nesting ground have also been found fossilized, and it laid its eggs in clutches about 25 eggs each, burying the nests under dirt and plants. The eggs were very round, like a football, and were 11 to 12 centimeters in diameter. The ones found also had fossilized embryos with skin impressions, showing that they had small bead like scales in a mosaic armor pattern. Saltasaurus also appeared in the show Dinosaur Planet, which makes two of my favorite dinosaurs in that show now… huh. 


Shout out goes to keep-calm-and-kjarri-on!

Hey there! The artist of that feather evolution pic is actually Emily Willoughby, who has also posted it on her own Tumblr

Thanks for clearing that up! Go check them out too!

Kulindadromeus zabaikalicus


NameKulindadromeus zabaikalicus 

Name Meaning: Zabaikal Kulinda Runner 

First Described: 2014 

Described By: Godefroit et al. 

ClassificationDinosauria, Ornithischa, Genasauria, Neornithischia

My Fourth Favorite Dinosaur 

When this dinosaur was discovered, it rapidly rose to the fourth position in my favorite list - and it’s obvious why. This dinosaur proves pretty clearly that feathers were synapomorphic for both Ornithischia and Saurischia (something I have been suggesting for years due to quills being found on another basal ornithischian, Tianyulong, as well as protofeathers found on Psittacosaurus, and the presence of feather protein genes in the crocodile genome, suggesting that protofeather-esque filaments are a trait of all of archosauria, based on cladistics. Genomes, man. Genomes.) It was found in teh ukureyskaya formation in Russia, which dates back to the middle to late Jurassic, about 169 to 144 million years ago in the Bajocian to Tithonian ages. It is known from a partial skeleton in rock that lead to amazing preservation of both feathers and scales. Now, this fossil was stolen and described as another species, Kulindapteryx, but this is not valid and should be ignored (curse you, BANDits.) 


Kulindadromeus was a bipedal runner, about 1.5 meters long, with a short head, short forelimbs, and long hindlimbs and tail. It had scales on the top of its tale and scales branching into feather like structures on the main part of the body. This fuzz all over the body are hair like filaments like stage 1 dino fuzz on Sinosauropteryx, and then another type is longer filaments on the upper arms and thighs like type three feathers, and then unique bundles of ribbon like structures on the upper lower legs that are made from parallel filaments. 

Source: Prehistoric-Birds (Give them a follow!) 

Kulindadromeus also had three types of scales: overlapping hexagonal scales on the lower shins, non-overlapping scales on the hands ankles and feet, and arched rectangular scales on the tail, forming rows. 

According to the science of evolutionary cladistics, the closer two clades are related to one another, the more likely any features shared by those clades was only evolved once, in their last common ancestor. More deviated groups - such as birds and bats - that share a feature evolved them separately. As such, the fact that crocodiles have a dormant feather gene (same protein) implies that the last common ancestor of both crocodiles and birds had feathers - and that’s just from genomics. Now, while this feature may have been lost in many archosaurian species - as fur is lost in many species of mammals - it is important that we now, as paleontologists, switch our line of thought from “scaled until proven otherwise,” to “feathered until proven otherwise.” The discovery of so many feathered or quilled theropods - as well as quite a few quilled and feathered ornithischians, now - only bolsters that claim. This is by far one of the most exciting discoveries of modern paleontology, and I can’t wait to see what more we find out about the connection between dinosaurs, birds, and feathers in the coming years. 


Shout out goes to prehistoric-birds, since I used their art!

Also, the moral of today’s story is NEVER TRUST A BANDIT