''Gondwanax'' (meaning "lord of

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus of

silesaurid Silesauridae is an extinct family of Triassic dinosauriforms. It is most commonly considered to be a clade of non-dinosaur dinosauriforms, and the sister group of dinosaurs. Some studies have instead suggested that most or all silesaurids compr ...

dinosauriform Dinosauromorpha is a clade of avemetatarsalians (archosaurs closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lagerpetids, ...

from the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

Pinheiros-Chiniquá Sequence of Brazil. The genus contains a single species, ''G. paraisensis'', known from a partial skeleton. ''Gondwanax'' represents one of the oldest known dinosauromorphs, and, alongside the roughly coeval ''

Gamatavus ''Gamatavus'' (meaning "Picada do Gama great-grandfather") is a genus of silesaurid dinosauriform from the Middle Triassic Santa Maria Formation of Dilermando de Aguiar Municipality, Brazil. The genus contains a single species, ''G. antiquus'' ...

'', one of the oldest South American silesaurs. While the possession of two sacral vertebrae characterizes more basal "silesaurid" taxa, ''Gondwanax'' has three—the oldest occurrence of this trait in the fossil record.

Discovery and naming

The ''Gondwanax'' fossil material was discovered in 2014 by physician and paleontology enthusiast Pedro L. P. Aurelio at the "Linha Várzea 2" ("Becker") site, belonging to the Pinheiros-Chiniquá Sequence of the Santa Maria Supersequence (Formation) in Paraíso do Sul municipality of

Rio Grande do Sul Rio Grande do Sul (, ; ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative units of Brazil#List, fifth-most populous state and the List of Brazilian s ...

, Brazil. These layers are representative of the ''

Dinodontosaurus ''Dinodontosaurus'' (meaning "terrible-toothed lizard") is a genus of dicynodont therapsid. It was medium to large dicynodont of the Triassic (with skull up to long) and had a beak corneum. It lived in the Middle Triassic but disappeared in the ...

Assemblage Zone In biostratigraphy, biostratigraphic units or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa, as opposed to a lithostratigraphic unit which is defined by the lithological properties ...

. He subsequently donated it to a university for study in 2021. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen, CAPPA/

UFSM The Federal University of Santa Maria (, UFSM) is a Brazilian public university located in Santa Maria, in the state of Rio Grande do Sul, funded by the federal government of Brazil. It was founded in 1960, by Professor José Mariano da Rocha ...

0417, is a single right femur. Several other partially disarticulated bones were found in association with this specimen. While no overlapping bones suggest the presence of multiple individuals, this possibility has not been ruled out as the bones were not found in perfect articulation. The additional material comprises two cervical, several

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

, three sacral, and at least three

caudal vertebrae Caudal vertebrae are the vertebrae of the tail in many vertebrates. In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx. In many reptiles, some of the caud ...

, and a partial

pelvic girdle The hip bone (os coxae, innominate bone, pelvic bone or coxal bone) is a large flat bone, constricted in the center and expanded above and below. In some vertebrates (including humans before puberty) it is composed of three parts: the Ilium (bone) ...

. In 2024, Rodrigo Temp Müller announced ''Gondwanax paraisensis'' as a new genus and species of silesaurids based on these fossil remains. The generic name, ''Gondwanax'', combines

—the name of an ancient 'supercontinent' containing South America—with the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

'' ἄναξ'', meaning "lord" or "king", in reference to the preeminence of dinosauromorphs throughout the Mesozoic Era. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, ''paraisensis'', references the municipality of Paraíso do Sul, where the specimens were found. The final version of the publication describing ''Gondwanax paraisensis'' was published the following year. Having been found in rocks belonging to the

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...

–

Carnian The Carnian (less commonly, Karnian) is the lowermost stage (stratigraphy), stage of the Upper Triassic series (stratigraphy), Series (or earliest age (geology), age of the Late Triassic Epoch (reference date), Epoch). It lasted from 237 to 227.3 ...

, ''Gondwanax'' is notable as it is one of the oldest known dinosauromorphs. ''Gamatavus'', another 'silesaurid' from the same locality, and ''Gondwanax'' together represent the oldest South American 'silesaurs'.

Description

The fossil material of ''Gondwanax'' indicates a body length of about . The basalmost 'silesaurids' are characterized by only two sacral vertebrae. However, ''Gondwanax'' is the oldest fossil dinosauromorph that has three sacral vertebrae.

Classification

In his

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

, Müller (2025) recovered ''Gondwanax'' as a basal member of the Sulcimentisauria. Similar to a number of recent studies, these taxa, along with other "traditional"

silesaurids Silesauridae is an extinct family of Triassic dinosauriforms. It is most commonly considered to be a clade of non-dinosaur dinosauriforms, and the sister group of dinosaurs. Some studies have instead suggested that most or all silesaurids compr ...

, are treated as a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

grade of ornithischians. These results are displayed in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below:

Paleoenvironment

''Gondwanax'' was found in the "Linha Várzea 2" site of the ''Dinodontosaurus'' Assemblage Zone (AZ) of the Santa Maria Formation. The

gracilisuchid Gracilisuchidae is an extinct family of suchian archosaurs known from the early Middle Triassic to the early Late Triassic (Anisian – early Carnian) of China, Argentina, and Brazil. Distribution Currently, the oldest known gracilisuchid is '' ...

'' Parvosuchus'' was also found in this site. The roughly coeval "Picada do Gama" site has yielded a closely related "silesaurid", ''

''. Other localities indicate that these animals likely shared an ecosystem with

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivores that typically bore a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, t ...

cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...

pseudosuchia Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...

ns, aphanosaurs,

rhynchosaur Rhynchosaurs are a group of extinct herbivorous Triassic archosauromorph reptiles, belonging to the order Rhynchosauria. Members of the group are distinguished by their triangular skulls and elongated, beak like premaxillary bones. Rhynchosaurs ...

s, and procolophonoids. The Brazilian ''Dinodontosaurus'' Assemblage Zone shares many faunal similarities with the Argentinian ''

Tarjadia ''Tarjadia'' is an extinct genus of erpetosuchid pseudosuchian, distantly related to modern crocodilians. It is known from a single species, ''T. ruthae'', first described in 1998 from the Middle Triassic Chañares Formation in Argentina. Parti ...

'' Assemblage Zone, the dinosauromorph-bearing units of the Tanzanian Lifua Member, and the Zambian

Ntawere Formation The Ntawere Formation is a Middle Triassic (Anisian) geological formation in Zambia, preserving fossils of synapsids, archosaurs, and temnospondyls. Geology Several different facies are present in the Ntawere Formation, reconstructing a floodpl ...

, potentially indicating that these units belong to similar temporal ranges.

References

{{Taxonbar, from1=Q130388948, from2=Q130388952 Silesauridae Ladinian genera Carnian genera Triassic reptiles of South America Triassic Brazil Fossils of Brazil Taxa named by Rodrigo T. Müller Fossil taxa described in 2025 Monotypic prehistoric reptile genera