Rhabdodontomorpha is a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

of basal

iguanodont Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivore, herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and rel ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s. This group was named in 2016 in the context of the description, based on Spanish findings of an early member of the

Rhabdodontidae Rhabdodontidae is a family of herbivorous iguanodontian ornithopod dinosaurs whose earliest stem members appeared in the middle of the Lower Cretaceous. The oldest dated fossils of these stem members were found in the Barremian Castrillo de l ...

. A

cladistic analysis Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...

was conducted in which it was found that ''

Muttaburrasaurus ''Muttaburrasaurus'' was a genus of herbivorous iguanodontian ornithopod dinosaur that lived in what is now northeastern Australia sometime between 112 and 103 million years agoHoltz, Thomas R. Jr. (2012) ''Dinosaurs: The Most Complete, Up-to ...

'' was the sister species of the Rhabdodontidae ''sensu'' Weishampel. Therefore, Paul-Emile Dieudonné, Thierry Tortosa, Fidel Torcida Fernández-Baldor, José Ignacio Canudo and Ignacio Díaz-Martínez defined Rhabdodontomorpha as a nodal clade: the group consisting of the last common ancestor of ''

Rhabdodon priscus ''Rhabdodon'' (meaning "fluted tooth") is a genus of ornithopod dinosaur that lived in Europe approximately 70-66 million years ago in the Late Cretaceous. The genus contains a single species, ''R. priscus''. It is similar in build to a very rob ...

'' Matheron, 1869 and ''Muttaburrasaurus langdoni'' Bartholomai and Molnar, 1981; and all its descendants. Within the clade ''

Zalmoxes ''Zalmoxes'' is a genus of rhabdodontid ornithopod dinosaur from the Maastrichtian age of the Late Cretaceous in what is now Romania. The genus is known from specimens first named as the species '' Mochlodon robustum'' in 1899 by Franz Nopcsa ...

'' and ''

Mochlodon ''Mochlodon'' is a genus of rhabdodontid dinosaurs from the Late Cretaceous of Austria and Hungary. It lived during the Late Cretaceous (85-80 Ma) and two species are known: ''M. suessi'' and ''M. vorosi''. Discovery and species In 1859 coal ...

'' are also included. In 2021, Daniel Madzia redefined Rhabdodontomorpha in the ''

PhyloCode The ''International Code of Phylogenetic Nomenclature'', known as the ''PhyloCode'' for short, is a formal set of rules governing phylogenetic nomenclature. Its current version is specifically designed to regulate the naming of clades, leaving the ...

'' as "the largest clade containing ''

'', but not ''

Iguanodon bernissartensis ''Iguanodon'' ( ; meaning 'iguana-tooth'), named in 1825, is a genus of iguanodontian dinosaur. While many species found worldwide have been classified in the genus ''Iguanodon'', dating from the Late Jurassic to Early Cretaceous, Taxonomy (bi ...

'' and ''

Hypsilophodon foxii ''Hypsilophodon'' (; meaning "high-crested tooth") is a neornithischian dinosaur genus from the Early Cretaceous Period (geology), period of England. It has traditionally been considered an early member of the group Ornithopoda, but recent resear ...

''". The clade is characterized by the following synapomorphies: * the outline of the dorsal iliac margin is sigmoidal in dorsal view, with the postacetabular process deflected medialward and the pre-acetabular process deflected laterally * the dorsal iliac margin is mediolaterally broader and swollen from above the ischiac peduncle anteriorly (present in ''Muttaburrasaurus'') or above the postacetabular process all along (present in ''Zalmoxes'' spp.) * the presence of a weak, dorsally convex ridge on the ventromedial side of their postacetabular process * the ischiac peduncle of the ilium is lenticular and uniquely anteroposteriorly long * the acetabulum is noticeably low The group consists of small to large plant eaters from Europe and

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 ...

. It must have split from other iguanodont groups during the Middle Jurassic. In 2020, the Australian iguanodont '' Fostoria'' was also found to belong to this clade. The slightly less inclusive Rhabdodontoidea was named by Karen Poole in 2022 and defined by Fonseca and colleagues in 2024 in the ''

'' as "the largest clade containing ''

'', but not ''

'', ''

'', and '' Tenontosaurus tilletti''".Poole K. 2022. "Phylogeny of iguanodontian dinosaurs and the evolution of quadrupedality". ''Palaeontologia Electronica''. 25(3):1–65 This clade includes the family

and all rhabdodontomorphs closer to them than to the tenontosaurids. ''Tenontosaurus'' and its close relatives belong to the family Tenontosauridae, defined in the ''

'' as "the largest clade containing '' Tenontosaurus tilletti'', but not ''

'', ''

'', and ''

''". They have been tentatively recovered as basal members of Rhabdodontomorpha, representing a North American radiation of this group. '' Iani'', described in 2023, is interpreted as a

transitional taxon A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. This is especially important where the descendant group is sharply differentiated by gross ...

between '' Tenontosaurus'' and

References

{{Taxonbar, from=Q24765920 Dinosaur clades Cretaceous dinosaurs