Macrocollum: Prehistoric Beast of the Week

This week we will be checking out a newly discovered dinosaur that is currently the oldest known member of its family. Check out Macrocollum itaquii!

Macrocollum was a plant-eating dinosaur that lived in what is now Brazil, during the late Triassic period, about 225 million years ago.  When alive, it would have measured about sixteen feet long from snout to tail.  The genus name translates from Greek to "long neck".

Macrocollum life reconstruction in watercolors by Christopher DiPiazza.

Macrocollum is an important find because it is the oldest known member of the group of dinosaurs known as the basal sauropodomorphs, or "prosaurpopods" as they have also been called.  These dinosaurs were common during the late Triassic and early Jurassic and are characterized by having long necks and tails, and proportionally small heads.  Many of them walked on their hind legs primarily, but others could also have dropped down to all fours, as well.  Plateosaurus, Massospondylus, Mussaurus, and Ingentia, are also members of this group.  There is evidence to suggest that this group of dinosaurs would later give rise to the gigantic sauropods, like Brontosaurus and Apatosaurus.

Close up photograph of a Macrocollum skull.  Note the down-turned tip of the snout and the small, leaf-shaped teeth.

The fact that Macrocollum is from as old a time as it is, combined with its anatomy, is what makes it extremely interesting, and tells us a lot about sauropodomorph evolution.  Macrocollum had a very long neck, and proportionally small head, just like later members of its family.  This tells us that, since it is so far the oldest-known member, that the sauropodomorph body type must have happened even earlier, from an ancestor that didn't have a long neck and proportionally small head.  Many paleontologists agree that the common ancestor to dinosaurs was a meat-eater.  Macrocollum's proportionally small head, small, leaf-shaped teeth, and long neck are all adaptations for eating plants, which proves that being a plant-eater must have evolved much earlier in the dinosaur family tree, too.

Multiple skeletons of Macrocollum were discovered very close to each other.  Each individual animal's remains are highlighted in a different color.  Image from Federal University of Santa Maria.

Macrocollum is also interesting in that multiple individual skeletons were discovered nearby each other.  This suggest that this dinosaur may have been social, perhaps living in groups, or sticking with family members as an adult, which is exciting to think about and rarely supported by fossil evidence.  That being said, keep in mind it is also possible that these dinosaurs may have just congregated at a riverbed in search of a resource, like water, during a time of drought, and all died at about the same time from lack of that resource.

References

Rodrigo Temp Müller; Max Cardoso Langer; Sérgio Dias-da-Silva (2018). "An exceptionally preserved association of complete dinosaur skeletons reveals the oldest long-necked sauropodomorphs". Biology Letters. 14 (11)