Abstract
In this study, we report a partial skeleton of a small (ca. 7 m) sauropod dinosaur from the ?upper Lower Jurassic (Pliensbachian) to Bajocian strata of the Kaladongar Formation (Khadir Uplift), Kachchh Basin, India. The partial skeleton is described and established as the holotype of a new taxon, Ceratocaudia antiqua gen. et sp. nov., diagnosed by a notch on the cervical postzygapophysis, a horn-like crest on the anterior caudal neural spine, progressive shift from platycoelous to procoelous articular facets in the posterior caudal vertebrae, anterior chevron with split articular facets (local autapomorphy), a deeply concave (notched) anterior surface of the distal tibia, and a well-developed anteromedial crest and subtriangular distal epiphyses in the fibula (local autapomorphies). Additional fragmentary remains from the same strata at a nearby locality are referred to the new taxon. Phylogenetic analyses best support the recovery of the new taxon as an early-branching, non-titanosauriform macronarian. The long bone histology and non-traumatic, non-contagious pathology indicate senescence in the holotype. The possibility of dwarfism in C. antiqua, based on size and ontogenetic stage of the holotype, is discussed. A hypothetical caudal musculoskeletal reconstruction of C. antiqua, generated using retrodeformed and reconstructed elements of the holotype, is used to determine tentative functional morphological implications, including the use of the tail as a mild deterrent to predators. Time-calibrated phylogeny of macronarian taxa suggests a pre-Bajocian global distribution, supporting recent hypotheses on neosauropod paleobiogeography. Ceratocaudia antiqua is the earliest diagnosable macronarian neosauropod from India and represents one of its earliest global occurrences.
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