saurischia – Nix Illustration

Mamenchisaurus

Although sauropod dinosaurs are famous for their long necks, one group known as mamenchisaurids took that particular feature to the extreme, with elongated necks that made up around half of their total body length.

And ‘Mamenchisaurus’ sinocanadorum* was one of the largest and longest. Living in what is now northwestern China during the Late Jurassic, about 160 million years ago, it had a 15m-long neck (~49′) and an estimated total length of 25-30m (~82-98′).

(*The whole Mamenchisaurus genus is a bit of a wastebasket and needs revision. Recent phylogenetic analyses suggest M. sinocanadorum was closer related to Xinjiangtitan than to other Mamenchisaurus species, but whether it actually belongs in that genus instead or merits its own new name has yet to be determined.)

Its enormous neck was ultralightly-built and highly pneumatic, with the vertebrae containing around 70% air sacs by volume. Extremely long cervical ribs served to stabilize the neck, but would also have limited flexibility along most of its length — it may have operated like a crane arm, sweeping around to feed on vegetation across a wide arc without having to move its body at all.

Eoraptor

It’s Moon Day, so let’s look at a dinosaur from the moon!

…Well, not literally. But Eoraptor lunensis‘ name means “dawn thief from the moon”, in reference to it being discovered in the Valle de la Luna (Valley of the Moon) of Ischigualasto Provincial Park, Argentina.

Living during the Late Triassic, around 231-229 million years ago, Eoraptor was one of the earliest known of all dinosaurs. Originally classified as an early theropod, it’s now thought to actually be a very early offshoot of the sauropodomorph lineage, closely related to other South American forms like Buriolestes and Pampadromeus.

It measured around 1.2m long (~4′), with leg proportions that indicate it was a fast runner. Its jaws contained both leaf-shaped and serrated pointed teeth, suggesting it may have been an opportunistic omnivore, feeding mainly on plant matter but occasionally supplementing its diet with smaller prey.

Unlike later dinosaurs it also still had vestigial palatal teeth on the roof of its mouth.

Eoraptor would have lived in a warm humid climate alongside several other early dinosaur species such as Herrerasaurus and Eodromaeus — but this was at a time before the dinosaurs had become the dominant terrestrial vertebrates, so other animals like rhynchosaurs, aetosaurs, rauisuchians, cynodonts and dicynodonts were also very abundant in the Ischigualasto ecosystem.

Ptychotherates

Ptychotherates bucculentus was a herrerasaurian dinosaur that lived during the Late Triassic, about 205 million years ago, in what is now New Mexico, USA.

Probably around 2m long (~6’6″), it had a short deep skull and massive cheekbones – unusual features for an early saurischian, and convergently similar to those of some later theropods.

Along with its close relatives Tawa, Chindesaurus, and Daemonosaurus (a grouping collectively known as “morphoraptorans”) it represents one of the latest-surviving known herrerasaurians, suggesting that these early-diverging carnivorous dinosaurs persisted in low-latitude regions until much closer to the end of the Triassic than previously thought.