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Dinodontosaurus isiyavamanda
George, Escobar, Moody, Saanane, Day & Larkin, 2026
Life reconstruction by Gabriel Ugueto |
ABSTRACT
Fossils from the Manda Beds of Tanzania have greatly informed on the diversity and evolution of Triassic tetrapods, including on what might be the oldest dinosaurs. Here, a new dicynodont taxon from the Manda Beds is described. It lacks key anatomical traits of known dicynodonts from the Manda Beds, as well as the Sino-African genus Shansiodon to which some of this material was previously referred. The new taxon is referred to the otherwise South American Dinodontosaurus based on the diagnostic presence of frontals with “tab-like” anterior processes and a combination of other traits seen in the genus. This Tanzanian material possesses a predominantly bulbous posterior/median palatal ridge of the premaxilla and a midline groove along the temporal bar, among other traits that are absent in the South American Dinodontosaurus material, indicating it represents a distinct species, here named Dinodontosaurus isiyavamanda sp. nov. Phylogenetic analyses conducted with Bayesian estimation and parsimony support the inclusion of this species in Dinodontosaurus. The unique palate of D. isiyavamanda is hypothesized to be related to resource partitioning, representing different adaptations for food processing than coeval dicynodonts. The presence of Dinodontosaurus suggests the mid-to-upper Lifua Member of the Manda Beds is equivalent to the Dinodontosaurus Assemblage Zone of Brazil and the Chañares Formation of Argentina. Consequently, the mid-to-upper Lifua Member, which includes what are possibly the oldest records of dinosaurs globally, can be confidently interpreted as late Ladinian to Carnian in age, supporting recent research questioning its equivalency with the Cynognathus Assemblage Zone of South Africa.
SYSTEMATIC PALEONTOLOGY
SYNAPSIDA Osborn, 1903
THERAPSIDA Broom, 1905
ANOMODONTIA Owen, 1860
DICYNODONTIA Owen, 1859
DICYNODONTOIDEA Olson, 1944
KANNEMEYERIIFORMES Maisch, 2001
DINODONTOSAURUS Romer, 1943
Diodontosaurus Tupí-Caldas, 1936 [nomen suppressum].
Chanaria Cox, 1968.
Type Species––Dinodontosaurus oliveirai Romer, 1943 (=Dicynodon tener Huene, 1935).
Diagnosis––Medium- to large-sized kannemeyeriiform (maximum skull length ca. 40 cm) with the following unique combination of character states: frontals with a “tab-like” median anterior process; postorbital bone with elongate, curved suborbital process; elongate caniniform process sharply offset from zygomatic arch; and hypertrophied tusks present in large individuals (taken from Kammerer & Ordoñez, 2021).
DINODONTOSAURUS ISIYAVAMANDA sp. nov.
Ruhuhuungualasaurus croucheri Larkin, 1994, p. 2.
Shansiodon sp. Surkov and Benton, 2004, p. 627.
Shansiodon sp. Surkov and Benton, 2008, p. 1126.
Diagnosis––Can be distinguished from both Dinodontosaurus brevirostris and Dinodontosaurus tener by a premaxillary posterior/median palatal ridge that expands anteriorly into a wide, bulbous morphology (does not retain the ridge-like morphology throughout its length), and extends further anteriorly than the point of eruption of the tusks; a midline groove extending along the temporal bar from immediately posterior to the pineal foramen to the posterior end of the postparietal; and mandibular rami that diverge more laterally. Can be further distinguished from Dinodontosaurus brevirostris by the lack of a ridge along the anterior surface of the mandibular symphysis. Can be further distinguished from Dinodontosaurus tener by a wider interorbital region and snout, and a pineal foramen that is not completely anterior to the intertemporal bar (i.e., pineal foramen is at the same anteroposterior level as the anterior portion of the bar).
Etymology––From the Manda words ‘isi ya vamanda’ that translate to ‘country of the Wamanda.’ In reference to the Wamanda people, many of whom were crucial to the discovery of the holotype, but whose individual names were not documented and never credited.
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two bulky Dinodontosaurus isiyavamanda walking through dense vegetation
Life reconstruction by Gabriel Ugueto |
Hady George, Juan A. Escobar, Edmund R.R. Moody, Charles B. Saanane, Michael O. Day and Nigel R. Larkin. 2026. Craniomandibular osteology of
Dinodontosaurus isiyavamanda sp. nov. (Therapsida: Anomodontia) from the Manda Beds of Tanzania and new support for a younger age for the alleged oldest dinosaurs.
Journal of Vertebrate Paleontology. e2692542. DOI:
doi.org/10.1080/02724634.2026.2692542 [15 Sep 2026]
