Anatomy and phylogenetic relationships of a possible lessemsaurid with associated plant fossils from the lower part of the Elliot Formation
Date
2023
Journal Title
Journal ISSN
Volume Title
Publisher
Evolutionary Studies Institute
Abstract
The Elliot Formation forms the middle layer of the Stormberg Group of South Africa and ranges in age from the Upper Triassic to the Lower Jurassic. This stratigraphic unit bears a rich and varied faunal assemblage, including a wide variety of vertebrate fossils, the most abundant of which are sauropodomorph dinosaurs. While Early Jurassic sauropodomorphs are increasingly well-known, our knowledge of Late Triassic sauropodomorphs from the lower Elliot Formation is still at a deficit. Specimens from this section of the Stormberg Group can provide key information on the early evolution of Sauropodomorpha. Here we report on a new specimen of a Late Triassic sauropodomorph from a locality a short distance above the Molteno – Elliot boundary making it among the stratigraphically lowest sauropodomorphs from South Africa. Phylogenetic analyses and body mass estimations indicate the specimen represents a medium-to-large-bodied possible lessemsaurid with a combination of plesiomorphic and derived characters. This specimen adds to the diversity of the lower Elliot Formation and provides stronger support for a biogeographical link between the Elliot Formation and the Los Colorados Formation of Argentina. This skeletally immature possible lessemsaurid also provides insight into body size evolution during the Norian, a critical time for the evolution of sauropodomorph gigantism. The fossil plant genera Taeniopteris and Cladophlebis were recovered from sediments containing the sauropodomorph specimen, documenting one of the first co-occurrences of dinosaurs and plant material in the Elliot Formation, as well as preserving direct evidence of plant-insect interactions.
Description
Keywords
Late Triassic, plant fossils, Taeniopteris, Cladophlebis, Norian, stormberg group, Main Karoo Basin