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What were the smallest dinosaurs?

Updated: Jan 25, 2023

Having previously discussed which dinosaurs were the largest of each group, howabout this time we look at the smallest dinosaurs? I'll follow the same sort of format as before, as well as let you know when we get to the smallest dinosaur of all time. Within each group, here are the teeny tiniest dinosaurs known to paleontologists!




Dromaeosaurs

Our first tiny dino is a dromaeosaur, the group that people more commonly refer to as 'raptors'. These guys aren't famous for being the big stompy kind anyway, but rather swift and agile hunters.

Artist's reconstruction of Zhongjianosaurus compared to a human hand
Art belongs to Tom Parker

The title of smallest 'raptor' that was ever seen during the Mesozoic belongs to Zhongjianosaurus yangi, a raptor belong to the group Microraptoria (and, no, a microraptor is not a pet dinosaur you can keep in your Gucci handbag). Zhongjianosaurus had some fairly hallmark traits of a microraptorid, having the trademark four wings! Quick digression in facts, but, whilst we don't know what colour Zhongjianosaurus was, we certainly know the colour of its close relative, second smallest dromaeosaur and namesake of the group, Microraptor zhaoianus, since fossilised melanosomes were found on a specimen, showing it was an iridescent black.


Zhongjianosaurus measured in at just 80cm (34.5 inches) in length and just ~0.3kg (~0.7lbs). However, despite the teeny stature, Zhongjianosaurus had remarkably long limbs for its size.




Ornithopods

Now we have a group that are most certainly known for their size, with the biggest members growing up to 15 metres (49 feet) long. This makes our next entry all the more intriguing. Enter Albertadromeus syntarsus, an ornithopod from the Late Cretaceous Oldman formation in, you guessed it, Alberta, Canada.

Diagram comparing Albertadromeus to a human
Image credit: https://dinosaurpictures.org/Albertadromeus-pictures


Being a bipedal ornithopod, Albertadromeus would have shared its environment with familiar faces such as Parasaurolophus, Daspletosaurus, Troodon, Dromaeosaurus and Chasmosaurus, but certainly would have had to have kept its little head down, measuring in at just 1.6 metres (5 feet) long and 16 kilograms (30 pounds) in weight.




Ceratopsians

Another bipedal dinosaur belonging to a group that are traditionally large and quadrapedal is Microceratus gobiensis (there are a lot of 'micro's on this list). However, it looked very much like a traditional ceratopsian in the head with its head frill and beaked mouth.

Diagram comparing Microceratus to a human
Image credit: http://www.prehistoric-wildlife.com/species/m/microceratus.html

Hailing from Asia during the Late Cretaceous, this tiny dinosaur was is often referred to as 'Microceratops', mostly because it was originally named this when it was discovered in 1953, however, much of the material was re-assigned to other genera and the type specimen was renamed as Microceratus in 2008, though 'Microceratops' is often used as an informal term. Microceratus measured in at around 60 cm (2 feet) long and anywhere between 3-10 kg (6.6-22 lbs) in weight.



Ankylosaurs

When it comes to the smallest dinosaurs, we can't leave out the most adorable ankylosaur! Liaoningosaurus paradoxus (a name that always sparks some curiosity, with 'paradox' in its name) is an ankylosaur from the Yixian formation, Late Cretaceous, China. The name of the species refers to the confusing mix of characteristics from both nodosaurid and ankylosaurid groups.


Thanks to certain physical adaptations, as well as as piscivorous stomach contents, it actually seems likely that this ankylosaur was actually a semi-aquatic dinosaur! On top of, of course, having an adorable face, Liaoningosaurus measured in at around 34 cm (1.1 feet) in length and the weight? Well... it's not actually known or even estimated!

Artist reconstruction of Liaoningosaurus
Art by PaleoEquii


Pachycephalosaurs

With regards to the pachycephalosaurs, the size range isn't actually that great. As I'm sure you saw in the post on the biggest dinosaurs, the boggest pachycephalosaur was Pachycephalosaurus itself, but the smallest the pachycephalosaur wasn't as comparitively smaller than the others on this list.

Artist's reconstruction of Wannanosaurus.
Art by Cesar Diaz

Believe it or not, Micropachycephalosaurus isn't actually a member of this group (though it does officially have the longest dinosaur genus name). As far as we know, the smallest pachycephalosaur was a little fella named Wannanosaurus yansiensis, a basal member of the group from the Xiaoyan formation, Late Cretaceous, China, who measured in at 60 cm (2 feet) long, though this is based on very few remains.




Stegosaurs

Another 'small' dinosaur only by relative standards, the smallest stegosaur is a subject of ongoing debate as to what is actually deserving of the title. Chungkingosaurus jiangbeiensis is a weeny little stegosaur from the Late Jurassic Shaximiao formation in China who has been compared heavily to another dinosaur known from the same formation, known as Tuojiangosaurus multispinus, with many suspecting Chungkingosaurus may be a juvenile of that species and, to be fair, you can somewhat see the resemblance...

Size comparison of a human and Chungkingosaurus
Image credit: https://commons.wikimedia.org/wiki/File:Chungkingosaurus_Scale.svg

Nonetheless, as of the time of writing this, Chungkingosaurus jiangbeiensis is an official species and therefore, at just approximately 5 metres (16.4 feet) long, was the smallest stegosaur!




Sauropods

Our penultimate group is the sauropods! Now, considering this is the one group out of, not just dinosauria, but the entire terrestrial animal kingdom known for being the biggest, it seems strange to discuss what would be considered quite miniscule, but nonetheless, here it is:

A display of a Europasaurus skeleton
Image credit: https://commons.wikimedia.org/wiki/File:Europasaurus_holgeri.jpg

Europasaurus holgeri is a sauropod belonging to the macronaria, named as such because of the relatively massive nasal opening of their skull. Europasaurus is actually a textbook example of what is known as island dwarfism (something I may touch on in later posts), where animals that are normally extremely large will live on a relatively small area, normally an island, in which resources are limited and so evolve to grow much smaller. Europasaurus, in paricular, grew to be only 6.2 metres (20 feet) long and 750 kg (1,650 lb) in weight, which is tiiiiiiny for a sauropod!

Someone holding a skull of a Europasaurus
Image credit: https://commons.wikimedia.org/wiki/File:Europasaurus_skull.JPG



Theropods

As with the 'biggest dinosaurs' post, I have elected to keep dromaeosaurs separate from the rest of theropoda. Not only that, but I've left the tiniest dinosaur until last! Not to get my usual level of pedantic, but the smallest dinosaur really does depend on what you think of as a dinosaur. What I mean is, do you mean avian or non-avian dinosaur (ugh, here he goes again)?


As any reader of this blog will known, dinosaurs are not extinct, but non-avian dinosaurs (the ones people always think of i.e. any dinosaur that isn't a bird) certainly are. Why not answer both?


Drum roll please...


The smallest non-avian dinosaur to have ever existed is none other than Parvicursor remotus.

A size comparison of a human and various alvarezsaurids
Image credit: https://commons.wikimedia.org/wiki/File:Alvarezsaurid_scale_martyniuk.png

Aaaaahhh he's soooo smaaaaalllll!


Measuring in at just 39 centimetres (15 inches) long and around 162 g (5.7 oz) in weight, Parvicursor is a theropod belonging to the group known as Alvarezsaurids, with its most famous member being the one-digit-armed Mononykus, a dinosaur I routinely have to remind myslef not to call 'Nipplesaurus'...just look why.

Artist's reconstruction of Parvicursor
Image credit: https://commons.wikimedia.org/wiki/File:Parvicursor.jpg



What was the actual smallest?

However, when we are talking about the smallest dinosaur...as in the smallest dinosaur to ever exist... we need only look at a time that can be seen on our clocks.


Yes folks, the smallest dinosaur to ever exist (that we know of as of the time of writing this) is not only an avian dinosaur, but is very much alive today!


Please may I introduce, measuring in at only 6.1 cm (2.38 in) and 2.6 g (0.092 oz) for females (which are larger than males), Mellisuga helenae AKA the Bee Hummingbird!

A Bee Hummingbird
https://commons.wikimedia.org/wiki/File:Bee_hummingbird_(Mellisuga_helenae)_adult_male_in_flight-cropped.jpg

Native only to Cuba, these little fellows are, as far as we know, the smallest dinosaurs to exist, still very much alive today!


Until next time!


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