the final box in our count down is Massospondylus…
Massospondylus: the “Longer Vertebrae”
Massospondylus is among the first dinosaurs to be discovered and described. In the year 1854, paleontologist Sir Richard Owen was given a pile of 56 bones from South Africa to study, which was a disjointed mix of vertebrae, arms, hands, legs, and feet. At first he did not believe them to be dinosaur fossils, but said they looked like those of a “large, extinct, carnivorous reptile.” He named it Massospondylus, and it was a number of years before the creature was officially recognized for the dinosaur it was.
But don’t judge Sir Owen too harshly. Understand that paleontology as a science was still brand new. Just for reference, the very first dinosaur ever described was Megalosaurus in 1824, Iguanodon was named in 1825, and Hylaeosaurus was named in 1832. These three were then compared and the name Dinosaur was coined in 1842.
Massospondylus was an early sauropodomorph that lived in early Jurassic South Africa, and grew to about 13 feet long. Its teeth are very much like those of certain iguanas, and so it has been proposed that they would have been mostly plant-eaters, but supplemented their diet with the leftovers from local predators or occasional meaty snack. Since the area in which they lived is described as desert, it is likely that they could scavenge during seasons when greenery was scarce.
The long neck shows its relationship with the giant sauropods that would roam the land and, like them, Massospondylus has “air pockets” in its bones. In a nutshell, sauropod bones are very much like bird bones on a huge scale. Relatively hollow compared to mammal bones, with all sorts of little struts and supports like the steel structure that supports a skyscraper. This reduces as much weight as possible while keeping as much strength as possible. Unlike its much larger cousins, Massospondylus stood on its hind legs.
Articulated fossils (portions of a fossil that are complete and in life position) show that the arms had a rather limited range of movement. The palms face each other, as if they could clap, and the shoulders are not strong enough to bear any weight. Animals that walk on all fours must be able to walk with the palms of their front paws, or at least the pads of their toes, on the ground. It was once proposed that early sauropods were knuckle-walkers, but this takes very special adaptations that animals like Massospondylus do not have. At least not as adults.
Fossil nesting sites have preserved the oldest dinosaur embryos ever found. The eggs discovered were close to hatching, and were arranged in tight rows of up to 34 eggs in a grouping. The eggshells were very thin, and though there does not seem to be a true nest, they appear to have been at least partially buried near a lake. There also appears to be evidence of colonial nesting, with large groups of Massospondylus returning to the area every year for the breeding season. What’s more, the hatchlings were toothless, and tracks show that they had a cumbersome, four-legged gait. Add to this that they had overlarge heads and huge, watery eyes…baby Massospondylus were adorable.
Being adorable babies does not guarantee parental care, but it certainly seems to help, because these hatchlings tended to hang around the nest site until they were doubled in size.
Pete's Paleo Petshop 
What a great way to conclude the season! A basal sauropodomorph, moreover one that happens to be one of the first dinosaurs known to science from Africa. I was wanting you to cover a basal sauropodomorph, and this one is just that good. I’m glad you demonstrated its importance to the understanding of related organisms as well as the genus itself.
For my final pick, I will cover a Jurassic critter you did not: Siderops, and early Jurassic amphibian from Australia. Named in 1983, it is solely known from a near-complete skull mandible and postcrania found in the state of Queensland. It was large, with a total length of 2.7 m (8 ft 10 in) and had a skull width of a skull width 70 cm (28 in) wide.
For me personally, I learned about this amphibian thanks to a toy of it made from the Cadbury Yowies line from around the early 2000s.
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Oh, and one more thing: Here are the names I’d give your advent calendar creature if I could decide:
1. Anchiornis: Yanse (Chinese for color)
2. Europasaurus: Holger/Zwerg (Former references the dinosaur’s discoverer, latter is the masculine form of the German word for dawrf)
3. Coroniceras (one of the more unlikely ones, but I will still cover it): Cora
4. Heterodontosaurus: Herschel (an alternative name for the South African district it was first found in)
5. Anurognathus: Anne
6. Gnathosaurus: Rod (derived from the word “broad”, of which the Greek word for it is where the genus for spoonbills (the type of bird you compared it to) is derived from)
7. Ischyodus: Amala (derived from the word “amalgamation” which ties into why chimaeras, the type if fish Ischyodus is, are called chimaeras)
8. Guanlong: Bofeng (Chinese for crest)
9. Volaticotherium: Kite (may sound straightforward, but the name also incorporates the word kit, which refers to the young of certain mammals. I’d also try out Kit and Kitson as alternatives)
10. Dakosaurus: Chomper
11. Lobolytoceras: Lola
12. Dysalotosaurus: Posey/Posy/Posie (Considering now Dryosaurus is essentially this creature’s closest relative and yours is named Rosie, I nominate any of these named to make it fit the term “rosy posy”)
13. Rhomaleosaurus: Alexander (derived from the “ale” part of the genus name and references one of the people who originally named it, specifically as a species of Plesiosaurus (the genus Rhomaleosaurus would be coined later on)
14. Yinlong: Wilbert (derived from Will Downs, whose surname makes up the origin of the animal’s species name. The name I selected sounds like “will burst”, which references how Yinlong would lead to an explosion of variations in frills and horns in its clade (Ceratopsia)
15. Asteracanthus: Aster
16. Mamenchisaurus: Menchi (this is the name of the vivosaur from the Fossil Fighters video game series that happens to be a Mamenchisaurus)
17. Ostafrikasaurus: Easton (name derived from “east”, which is what the “Ost” part of the genus name means)
18. Scelidosaurus: Harrison (a nod to its species name)
19. Castorocauda (the one’s almost certainly impossible since this is already in the roster, but you stated that the Castorocauda here is what you’d like to think of as “Cassie’s older brother”, so that’s what I will designate this to be): Caster
20. Attenborosaurus: Adam (derived from the first two syllables of its name and Dr. Adam S. Smith, a plesiosaur expert and the creator of the Dino Toy Blog and Dino Toy Forum)
21. Holophagus: Horatio
22. Kentrosaurus: Kali (this was a given, as you’ve already decided on this one years ago)
23. Stenopterygius: Delphine (a nod to it being the “quintessential” ichthyosaur, with a typical dolphin-like body)
24. Razanandrongobe: Bibidia/Androngo (I’m struggling to look for a good name, but here are a few; they’re the Malagasy words for “wild” and “lizard” respectively)
25. Massospondylus: Massimo/Mason (I can’t decide between the two)
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All great ideas. 🙂 I like to keep the names simple, as if a kid named it. Sometimes I’ll have a plan for a name, but it’s never official until the critter is added to the shop for “adoption”. I really need to look at the finished character to see what name fits best.
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Thank you! Sauropods have so much diversity, and Massospondylus is one of those with a great history to explore.
It’s awesome when a toy company can introduce us to a new creature. 🙂
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Merry Christmas!! It’s been so cool to discover such a huge variety of dinosaurs I never even knew existed. One of the best parts is to see all the diversity in each dino/prehistoric critter!
So often, it seems like no one can deviate from the standard dark brown/green, not matter what kind of dino it is. But especially while seeing the completed calendar, it’s really interesting to see all the patterns and think of how each one fit into its environment! Also prevents the “dinosaurs lived on a blank sheet of paper” thought tendency, haha.
I like how you always relate our knowledge of modern animal anatomy to what we know from dinosaurs. It’s easy to assume something based on what’s right in front of us, but it’s so important to keep in mind the big picture (bone, soft tissue, cartilage…)! Also a very important reminder for other kinds of research.
It’s also been fascinating to read the story of each critter–they all have such unique backstories! And some of the lesser well-known dinosaurs can have some of the earliest backstories, like massospondylus. 😀
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Merry Christmas Brownie! Thank you so much for your thoughtful comment, I’m glad you enjoyed the count down. I’ve had a blast with the variety of critters, their stories, and possible scenarios for future drawings or stories. 😀 I might have to add a few of these to the shop properly, but there are so many awesome critters it’s hard to choose! At least they get a small spotlight this way until the day I can give them more time.
One of the advantages of scheduling all these in advance is being able to step back and make sure I don’t have too much of any one color. I like browsing pictures of different animals that could’ve had similar niches in their environments, and I get inspiration from them. There is so much variety in pattern even in animals that we might think of as brown or green, so it’s fun to experiment with that.
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The adults were probably fairly cute as well, not as cute as the babies, but still pretty cute.
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I think they would have been lovely creatures to witness in real life. 🙂
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