About This Project

The worlds oldest known tortoise Hadrianus majusculus was collected from the Eocene San Jose Formation in the vicinity of Almagre Arroyo. It is approximately 53 million years old. The original specimen was a near complete shell filled with matrix. This was damaged along the mid-line obscuring the morphology of the neural bones and all internal structures. I intend to survey this area for additional specimens to fill in the gaps in our knowledge of these turtles morphology.

Ask the Scientists

What is the context of this research?

The oldest tortoise ever found Hadrianus majusculus was found in the vicinity of Almagre Arroyo in the late 1800's. This was written up by Hay (1904) and elaborated on in Hay (1908) based on the one complete shell. This specimen remains the only relatively complete specimen of this species ever found. This has limited our knowledge of this species and hindered research on its anatomy and relationships (Shockey and Vlachos, 2018).

What is the significance of this project?

Hadrianus majusculus is the oldest testudinid (tortoise) known and thus provides an important link to the origins of the Testudinidae from more basal turtles. Knowing precisely where it fits in the family tree of turtles and what traits associated with testudinids Hadrianus majusculus did and didn't have will help place it in context and provide clues to the geographic and temporal origin of their lineage. In particular the morphology of the neural bones has been controversial being described differently in different publications. Furthermore the internal surface of the plastron, limbs, vertebrae and skull are completely unknown. The skull in particular is highly used in turtle phylogeny. The limbs would provide a greater insight into the ecology of these early tortoises.

What are the goals of the project?

The goal of this project is to find additional specimens of Hadrianus majusculus that will fill in the gaps in our knowledge of its morphology. Furthermore, this will provide an additional test of if the original specimens morphological oddities were one off random events or true traits of this part of the testudinid lineage. We will start the expeditions in May 2019 as soon as the weather warms sufficiently to clear the roads. Once the specimens are collected they will be brought back to the New Mexico Museum of Natural History and Science for cleaning and study leading to a peer reviewed publication. The morphology of the neural bones, the internal surface of the plastron, limbs, vertebrae and skull are completely unknown and contain important characters.