Description and Classification

Zby was a large, four-legged, plant-eating dinosaur, characteristic of sauropods, with a long neck and a long tail. Although a complete skeleton has not yet been discovered, the known bones, especially its very sturdy humerus (upper arm bone) measuring 136 centimeters (about 4.5 feet), indicate that Zby was a massive animal. Early estimates suggested it might have weighed around 48 metric tons, but such figures are considered preliminary until more fossils are found. Its body plan would have resembled that of other giant sauropods, designed to support its great weight and allow it to reach high into trees for food.

Zby is classified as a member of Turiasauria, a group of early eusauropod dinosaurs primarily known from Europe, though some possible members have been found in North America and Africa. Turiasaurs, such as Turiasaurus from Spain (one of Europe’s largest known dinosaurs) and Losillasaurus, were significant herbivores in the Late Jurassic ecosystems of the Iberian Peninsula. The inclusion of Zby within this group helps scientists better understand the diversity and geographic spread of these enormous dinosaurs.

Distinguishing Features

Zby can be identified by several characteristics that set it apart from other sauropods, including other turiasaurs. These include:

• A prominent, sharp ridge on the back side of its humerus (upper arm bone), positioned at the level of the deltopectoral crest, an area where strong arm muscles attached.
• The forelimb bones are exceptionally robust, even for a sauropod, suggesting very strong front legs.
• Specific details in the shape and structure of the few vertebral parts found also contribute to its unique diagnosis, though more skeletal material would clarify these distinctions further.

Paleoenvironment and Diet

Zby lived in the region of modern-day Portugal during the Late Jurassic. Its fossils were unearthed from the Lourinhã Formation, which represents a coastal environment rich with river deltas, extensive floodplains, and plentiful plant life. The climate during this time was likely warm and humid, supporting a diverse ecosystem. As a large herbivore, Zby would have consumed considerable amounts of vegetation, using its long neck to browse on high-growing conifers, cycads, and ferns that flourished in the area. It shared its habitat with a wide array of other dinosaurs. These included large predatory theropods such as Allosaurus, Torvosaurus, and Lourinhanosaurus; other sauropods like Dinheirosaurus and Lusotitan; and ornithischian dinosaurs including the stegosaur Miragaia and the ornithopod Draconyx. This variety of dinosaurs indicates a productive and complex food web.

Significance and Ongoing Research

The discovery of Zby has provided valuable new information about sauropod diversity in Europe during the Late Jurassic period, particularly concerning the turiasaurian dinosaurs. It underscores the Iberian Peninsula as an important center for the evolution and radiation of these colossal plant-eaters. Fossils from the Lourinhã Formation, including those of Zby, offer critical insights into the types of animals that inhabited this region and how they interacted within their ancient environment. Current and future research on Zby and its relatives focuses on better understanding their evolutionary relationships, their unique anatomical features, and their ecological roles. The discovery of more complete Zby skeletons would be extremely beneficial for refining size estimates, learning more about its anatomy, and confirming its precise position within the sauropod family tree. Such findings would also allow for more detailed comparisons with other European sauropods like Turiasaurus, further illuminating the ancient history of these magnificent creatures.