Miragaia: Beast of the Week

This week we will be checking out a unique plated dinosaur.  Enter Miragaia longicollum.  Miragaia was a plant-eating dinosaur that lived in what is now Portugal during the Late Jurassic Period, about 150 million years ago.  From beak to tail it measured roughly twenty feet (6m) long.  The genus name is in honor of the village of Miragaia, near where its bones were first uncovered in eastern Portugal.  However, "Miragaia" also translates to "wonderful Gaia".  Gaia, in Greek mythology, was the titan of the earth, and mother to many of the gods.   The species name, longicollum, translates to "long neck" for reasons that don't need explaining once you see what this dinosaur looks like.

Watercolor life reconstruction of Miragaia by Christopher DiPiazza.

Long necks are nothing new or unusual for dinosaurs.  Sauropods, being the most famous for having them, as well as many theropods, including lots of living birds!  Miragaia, however, was none of those things.  Miragaia was a stegosaurid, a close relative to the more famous, Stegosaurus.  Among stegosaurids, Miragaia had a noticeably long neck, which consisted of seventeen vertebrae.  Stegosaurids in general tended to have relatively long-ish necks, consisting of between nine and thirteen vertebrae (depending on the species) possibly to help them access as much low-growing vegetation as possible without having to move their bodies while feeding.  The specific reason why Miragaia's neck was as long as it was is still somewhat of a mystery.  What's even more interesting is the fact that since it lived during the late Jurassic, Miragaia was coexisting with sauropods, which also had extremely long necks.  Perhaps it was evolving to compete with its sauropod neighbors?  Keep in mind, despite a quadruped, Miragaia was probably able to rear up on its hind legs for short periods of time, perhaps to reach higher vegetation while feeding.  This is because its center of gravity would have been in its hips, making its front end much lighter.  Maybe its neck allowed it to feed in a space just below the larger sauropods, but beyond other stegosaurids?  We may never know for certain. 

Miragaia is an interesting find because it was not discovered by paleontologists looking for fossils.  Its remains were found on accident by construction workers, while building a road.  Because of this, only the front half of Miragaia's skeleton was initially found, the back part unknowingly may have been destroyed during the construction. Years later a stegosaur, currently called Alcovasaurus but possibly a different species of Miragaia, was published on, which included elements of the back half of the body, including long spikes that would have been on the tail.  

There are a number of interesting things to note about this Miragaia other than the neck.  Part of Miragaia's skull was preserved, including the beak.  Miragaia's beak was relatively small, but flared out slightly on either side, making an almost upside-down heart shape.  This beak was likely ideal for clipping vegetation to be processed by the small teeth farther back in the mouth.

Photograph of most of Miragaia's bones that are on the fossil record.  Photo credit: Dr. Mateus.

Miragaia had bony plates on its back, just like all known stegosaurids.  These plates (at least the ones that were found) were relatively small, and were arranged in pairs.  The plates may have been for display between members of the species.  They also might have had a role in temperature regulation or even could have helped with camouflage by obscuring the animal's profile, depending on what kind of environment it was in.  Many living reptiles have similar adaptations today, like spines and sails for those purposes.  Stegosaurids are also known for having spikes, usually, but not limited to the tail.  Two spikes were unearthed in association with a possible Miragaia specimen, suggesting it may have had an arrangement similar to that of its relative, Kentrosaurus, with the front half of its back adorned with plates that turn into long spikes around the hips and continue to the tip of the tail.  These spikes were extremely long and would have been potentially deadly defensive weapons against potential predators, like Allosaurus or Torvosaurus.

That is all for this week!  As always feel free to comment below or on our facebook page!

References

Costa, Francisco; Mateus, Octávio (13 November 2019). "Dacentrurine stegosaurs (Dinosauria): A new specimen of Miragaia longicollum from the Late Jurassic of Portugal resolves taxonomical validity and shows the occurrence of the clade in North America". PLOS ONE. 14 (11): e0224263.

Mateus, O.; Maidment, S. C.R.; Christiansen, N. A. (2009). "A new long-necked 'sauropod-mimic' stegosaur and the evolution of the plated dinosaurs". Proceedings of the Royal Society B: Biological Sciences. 276 (1663): 1815–21.

Waskow, Katja; Mateus, Octavio (2017). "Dorsal rib histology of dinosaurs and a crocodylomorph from western Portugal: Skeletochronological implications on age determination and life history traits". Comptes Rendus Palevol.

Ornithomimus: Beast of the Week

 This week we will be looking at a fast-running dinosaur that looked like modern birds. (but wasn't directly related to them) Make way for Ornithomimus!

Ornithomimus was a theropod dinosaur that lived in what is now mostly western North America, although some fragmentary fossils that appear to be from it have also been found on the east coast of the United States, including New Jersey.  It lived during the late Cretaceous period, between 76.5 and 66 million years ago, and therefore was one of the dinosaurs wiped out by the meteorite that ended the Mesozoic.  From beak to tail it would have measured about 12 feet (3.6 meters) long and was either an herbivore, or possibly an omnivore when alive.  Its genus name translates to "Bird Mimic" because of its birdlike (specifically ostrich) appearance.  

Ornithomimus edmontonicus life reconstruction in watercolors by Christopher DiPiazza.

Ornithomimus was a member of the ornithomimosaur family of theropods, characterized by their long, slender necks, long legs, long arms, and beaked faces.  Like Ornithomimus, many were toothless, but a few earlier members had small teeth.  Struthiomimus, Gallimimus, Harpymimus, and even the gigantic Deinocheirus, are all also members of this group.  Like many of its relatives, Ornithomimus had proportionally long arms with three fingers on each hand and long powerful legs, suggesting it was a fast runner.  A large number of Ornithomimus foot bones on the fossil record were found by paleontologists to be devoid of stress fractures, further supporting the idea they were adapted to running in life. Ornithomimus also had a slender beak with proportionally large eye sockets, suggesting it had strong eyesight in life.  

Ornithomimus edmontonicus skeleton on display at the Royal Tyrell Museum in Alberta, Canada.

Ornithomimus is currently known from two species.  The earliest of the two, called Ornithomimus edmontonicus, lived between 75.5 to 72 million years ago, in what is now Alberta, Canada.  It would have coexisted with other dinosaurs, like Albertosaurus, Anodontosaurus, Pachyrhinosaurus, Sphaerotholus, Hypacrosaurus, and its close relative, Struthiomimus.  The later species, Ornithomimus velox, was the slightly smaller species based on known material, and lived more in what is now the United States, from the very end of the late Cretaceous.  This species would have crossed paths with Tyrannosaurus, Triceratops, Pachycephalosaurus, Anzu, and Ankylosaurus to name a few, and like them, would have gone extinct when the asteroid that ended the Mesozoic hit the earth, 66 million years ago.  In the past Ornithomimus actually included a whopping seventeen more species that have since mostly been lumped into one of the two previously mentioned, or found to be different genera.

Fossilized remains of Ornithomimus feathers circled in yellow.  Specimen at the Royal Tyrell Museum.

For decades most experts suspected Ornithomimosaurs, like Ornithomimus, sported feathers in life based on its resemblance to modern birds and the presence of fossilized feathers in other kinds of dinosaurs.  More recently, however, this hypothesis was confirmed thanks to not one, but several separate specimens of Ornithomimus edmontonicus that sport fossilized remains of feathers.  Thanks to these exquisite fossils, we now know that young Ornithomimus had shaggy down-like feathers on their bodies, much like many modern birds.  We also know that adult Ornithomimus sported long feathers on its lower arms, like the wings of modern ostriches. It is worth noting that the Ornithomimosaurs were NOT direct ancestors of modern ostriches or any other birds (modern types of birds already existed during the time ornithomimosaurs were alive), but a beautiful example of convergent evolution, when two different kinds of animals independently evolve similar features and end up looking more closely related than they really are.

References

Makovicky, P.J., Kobayashi, Y., and Currie, P.J. (2004). "Ornithomimosauria." In Weishampel, D.B., Dodson, P., & Osmólska, H. (eds.), The Dinosauria (second edition). University of California Press, Berkeley: 137-150.

Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331-336.

Zelenitsky, D. K.; Therrien, F.; Erickson, G. M.; Debuhr, C. L.; Kobayashi, Y.; Eberth, D. A.; Hadfield, F. (2012). "Feathered Non-Avian Dinosaurs from North America Provide Insight into Wing Origins". Science. 338 (6106): 510–514.