![\"An](\"https:\/\/cdn.sci.news\/images\/enlarge13\/image_14719e-Isodapedon-varzealis.jpg\")
<\/a><\/p>\nAn artistic representation of a Late Triassic landscape of southern Brazil depicting individuals of Isodapedon varzealis in the foreground and a proterochampsid in the background. Image credit: Caio Fantini.<\/p>\n
Rhynchosaurs were among the most abundant plant-eaters of their time, spreading across much of the supercontinent Pangea and in some places making up the vast majority of fossilized vertebrates.<\/p>\n
Their specialized feeding apparatus \u2014 including a toothless beak and rows of grinding teeth \u2014 allowed them to process tough vegetation and dominate terrestrial ecosystems.<\/p>\n
\u201cRhynchosauria, an early diverging clade within Archosauromorpha, is represented by several species distributed mainly during the Middle and Late Triassic, though their origin dates back to the Early Triassic,\u201d said Universidade Federal de Santa Maria paleontologist Jeung Hee Schiefelbein and colleagues.<\/p>\n
\u201cRhynchosaurs spanned nearly the entirety of Pangea, and their fossil record extends across several present-day regions, including Brazil, Argentina, Canada, the United States, Zimbabwe, Tanzania, South Africa, Madagascar, India, England and Scotland.\u201d<\/p>\n
\u201cBy the Late Triassic, rhynchosaurs achieved a nearly global distribution, playing a significant role as primary consumers in terrestrial ecosystems.\u201d<\/p>\n
\u201cOwing to their abundance, especially in Late Triassic units, rhynchosaurs are also vital biostratigraphic markers, with rhynchosaurs making up to 90% of the vertebrate fossils in some outcrops.\u201d<\/p>\n
The holotype specimen of Isodapedon varzealis was unearthed at the V\u00e1rzea do Agudo site in the Brazilian state of Rio Grande do Sul.<\/p>\n
The fossil dates back around 230 million years to the Carnian age of the Triassic period.<\/p>\n
The upper jaw of Isodapedon varzealis features symmetrical tooth-bearing areas \u2014 an unusual trait among its relatives \u2014 along with a unique configuration of the lower jaw that suggests it fed differently from other known rhynchosaurs.<\/p>\n
A phylogenetic analysis indicates that the species lies outside previously recognized South American members of its subgroup, known as hyperodapedontines.<\/p>\n
The findings challenge the traditional classification of these reptiles and supports a narrower definition of the well-known genus Hyperodapedon, limiting it to its original type species.<\/p>\n
The results also point to a broader and more complex evolutionary radiation of rhynchosaurs than previously appreciated.<\/p>\n
Closely related forms appear to have spread widely across southwestern Gondwana \u2014 the southern portion of Pangea \u2014 while maintaining relatively conservative body plans.<\/p>\n
\u201cIsodapedon varzealis\u2019 unique combination of craniomandibular characters, including symmetrical maxillary tooth-bearing areas and autapomorphic dentary features, distinguishes it from contemporaneous species such as Macrocephalosaurus mariensis and Hyperodapedon sp.,\u201d the researchers said.<\/p>\n
\u201cThese differences probably reflect divergent ecological strategies within a diverse herbivorous guild, which could indicate niche partitioning during a time of dynamic environmental and floral changes associated with the Carnian Pluvial Episode.\u201d<\/p>\n
\u201cMoreover, its affinities with early diverging hyperodapedontines from Argentina and possibly Zimbabwe point to a broad, morphologically conservative radiation across southwestern Gondwana, highlighting ecological stability before the emergence of more derived and geographically restricted lineages.\u201d<\/p>\n