#archovember2024

Jakapil kaniukura was a basal thyreophoran, the group that led to stegosaurs in the Late Jurassic and ankylosaurs in the Cretaceous. In the Early Jurassic, thyreophorans like Scutellosaurus were small and bipedal, eventually becoming the armoured tanks of later eras.

However, Jakapil lived in the Late Cretaceous of Argentina, at the same time as ankylosaurs on other continents, and its discovery represents a previously unknown lineage of thyreophoran in South America. Though fragmentary, its proportions seem to suggest it was bipedal like the early thyreophorans, and it also had distinct teeth that allowed it to chew, rather than shear leaves. Hopefully we can uncover more information about this strange little armored dinosaur in the future.

Jakapil lived in the Candeleros Formation which, in the Late Cretaceous, was an ancient desert called the Kokorkom Desert. This environment was covered in windblown sand, broken up by oases. Here, the tiny Jakapil would have lived in the shadow of sauropods like Limaysaurus and Rayososaurus, and the giant theropod Giganotosaurus. It would have also lived alongside small theropods like Bicentenaria, Buitreraptor, and the alvarezsaurid Alnashetri, as well as pseudosuchians like Araripesuchus, rhynchocephalians like Priosphenodon and Tika, mammals like Cronopio, turtles like Prochelidella, and frogs like Avitabatrachus.

Archovember day eight! Euparkeria Capensis

little guys in a cave, i really hate this one its probably the worst one ive made. shouldnt have drawn in orange but im not redoing it

This ceratopsian lived in the Late Cretaceous (as most species of ceratopsian did - they radiated out to their most diverse not too long before the extinction event). This species was rather short-lived, with some scientists estimating it only existed as a species for less than 1 million years! It was only recently named as a species as well - the holotype had just been given a name in 2023!

It was a smaller ceratopsian only reaching about 4 meters (12 feet) from snout to tail. The holotype hails from Montanta, USA, from the Judith River Formation (not far from the famous Hell Creek Formation).

Before it was confirmed that birds were dinosaurs, Compsognathus longipes was regarded as the smallest dinosaur for decades. About the size of a chicken, its name means “elegant/refined/dainty jaw”. It lived in Late Jurassic Europe, found thus far in both Germany and France, with possible teeth also found in Portugal. It was carnivorous, and the remains of small lizards were found preserved in both fossil specimens. They were likely fast, scurrying animals, using their long tails for balance.

In the Late Jurassic, Europe was a dry, tropical archipelago at the edge of the prehistoric Tethys Sea. Both Compsognathus specimens were preserved within lagoons, possibly having died chasing lizards on the beach and then being swept out to sea in a flash flood. The German specimen is known from the Painten Formation, a part of the Solnhofen Limestone. The French specimen was found in limestone on the plateau of Canjuers. One of Compsognathus’ most famous contemporaries is the avialan Archaeopteryx, and the two may have competed over prey. It would have also lived alongside early pterosaurs like Propterodactylus, Rhamphorhynchus, and Anurognathus (as seen above). There were also a diverse variety of turtles, rhynchocephalians, and lizards living here as well, many of which served as prey for this tiny, catlike predator.

After the K-T extinction, the last remaining dinosaurs began to diverge, trying on many different shapes and sizes. While most birds stayed in the small forms that had kept them alive for so long, some achieved massive sizes. Some even reached these sizes while still retaining their ability to fly. One such genus was Pelagornis, a group of “pseudotooth birds.” While the gene for teeth was lost in birds, the Pelagornithids found a work-around, evolving tooth-like edges to their beaks. These were seabirds, using their saw-edged beaks to grip onto slippery fish and squid. The largest species of Pelagornis was Pelagornis sandersi. P. sandersi was not only the largest Pelagornis, but also had the widest wingspan of any known bird, estimated at 6.06 to 7.38 m (19.9 to 24.2 ft) long. P. sandersi had short, stumpy legs, and likely spent most of its time on the wing. It would have had to take off by dropping from cliffs, utilizing air currents to glide into the air. It would have been able to travel long distances like this, without landing, similar to modern day albatrosses.

Fossils of Pelagornis have been found worldwide, including in the Aridal Formation of Morocco, the Chandler Bridge Formation of South Carolina, the Bahía Inglesa Formation of Chile, the Black Rock Sandstone of Australia, the Molasse Coquilliere Formation of France, the Calvert Formation in Virginia, the Pisco Formation of Peru, the Castillo Formation and Capadare Formation of Venezuela, the Greta Formation of New Zealand, and the Purisima Formation of California. This worldwide distribution means they would have been living alongside a large variety of Eocene to Early Pleistocene animals, and eating a large variety of fish species. It is unknown why these giant seabirds went extinct, but they may have been encountered by archaic humans in the Early Pleistocene.

Living in Late Jurassic Wyoming, USA, Gargoyleosaurus parkpinorum is one of the earliest ankylosaurs known from mostly complete fossil remains. It was a nodosaur, part of a family of ankylosaurs that lacked club-tails. Gargoyleosaurus would have instead relied on its body armour and sharp shoulder spikes for defense. It was relatively small, reaching 3–3.5 m (9.8–11.5 ft) long and weighing an estimated 300–754 kg (661–1,662 lb). Like other nodosaurs, it was likely a herbivore, swallowing ferns, cycads, and angiosperms, and relying on symbiotic bacteria and gut flora to digest its food.

With a name meaning “giant thunderclap at dawn” in Sesotho, Ledumahadi mafube is one of the first sauropodomorphs known to become a quadrupedal giant. Living in Early Jurassic South Africa, it is known from fragmentary remains, but we can infer its appearance based on its relatives, though it was significantly larger than them. Ledumahadi is estimated to have weighed around 12 tonnes (13 short tons), similar in body mass to Diplodocus, though its neck and tail were likely shorter. At a time when most dinosaurs were small, scampering things, Ledumahadi would have been the largest animal around, and it hinted at what would someday be in store for this clade of giants.

Ledumahadi lived in the Elliot Formation, which would have been a semi-arid landscape with meandering rivers. The most common dinosaur here was the smaller, bipedal sauropodomorph Massospondylus. Other sauropodomorphs Ledumahadi would have lived alongside include Blikanasaurus, Aardonyx, Antetonitrus, and Pulanesaura. It would have also come across the basal ornithischians Heterodontosaurus, Abrictosaurus, Lycorhinus, and Lesothosaurus. Small pseudosuchians like Sphenosuchus, Litargosuchus, and Orthosuchus would have prowled through the underbrush or swam through the rivers. Ledumahadi, or at least its young, could have been preyed on by the neotheropod Dracovenator.