Rhabdodontomorpha

Rhabdodontomorpha Temporal range: Cretaceous, 140–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Muttaburrasaurus mount at the Queensland Museum
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Neornithischia
Clade:	†Ornithopoda
Clade:	†Iguanodontia
Clade:	†Rhabdodontomorpha Dieudonné et al., 2016
Subgroups
†Ampelognathus? †Emiliasaura †Fostoria? †Muttaburrasaurus? †Tenontosauridae? Fonseca et al., 2024[1] †Convolosaurus? †Iani †Tenontosaurus †Rhabdodontoidea Poole, 2022[2] †Mochlodon? †Transylvanosaurus? †Rhabdodontidae

Rhabdodontomorpha is a clade of basal iguanodont dinosaurs. This group was named in 2016 in the context of the description, based on Spanish findings of an early member of the Rhabdodontidae. A cladistic analysis was conducted in which it was found that Muttaburrasaurus 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 Matheron, 1869 and Muttaburrasaurus langdoni Bartholomai and Molnar, 1981; and all its descendants. Within the clade Zalmoxes and Mochlodon are also included.^[3] In 2021, Daniel Madzia redefined Rhabdodontomorpha in the PhyloCode as "the largest clade containing Rhabdodon priscus, but not Iguanodon bernissartensis and Hypsilophodon foxii".^[4] The clade is characterized by the following synapomorphies:^[5]

• 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. It must have split from other iguanodont groups during the Middle Jurassic.^[3] In 2020, the Australian iguanodont Fostoria was also found to belong to this clade.^[5] The slightly less inclusive Rhabdodontoidea was named by Karen Poole in 2022 and defined by Fonseca and colleagues in 2024 in the PhyloCode as "the largest clade containing Rhabdodon priscus, but not Hypsilophodon foxii, Iguanodon bernissartensis, and Tenontosaurus tilletti".^{[6] [7]} This clade includes the family Rhabdodontidae and all rhabdodontomorphs closer to them than to the tenontosaurids.^[7] Tenontosaurus and its close relatives belong to the family Tenontosauridae, defined in the PhyloCode as "the largest clade containing Tenontosaurus tilletti, but not Hypsilophodon foxii, Iguanodon bernissartensis, and Rhabdodon priscus". They have been tentatively recovered as basal members of Rhabdodontomorpha, representing a North American radiation of this group.^[7][8] Iani, described in 2023, is interpreted as a transitional taxon between Tenontosaurus and Rhabdodontidae.^[8]

References

1. Fonseca, André O.; Reid, Iain J.; Venner, Alexander; Duncan, Ruairidh J.; Garcia, Mauricio S.; Müller, Rodrigo T. (2024-12-31). "A comprehensive phylogenetic analysis on early ornithischian evolution". Journal of Systematic Palaeontology. 22 (1). doi:10.1080/14772019.2024.2346577. ISSN 1477-2019.
2. Poole, Karen (2022). "Phylogeny of iguanodontian dinosaurs and the evolution of quadrupedality". Palaeontologia Electronica. doi:10.26879/702. ISSN 1935-3952.
3. Dieudonné, Paul-Emile; Tortosa, Thierry; Fernández-Baldor, Fidel Torcida; Canudo, José Ignacio; Díaz-Martínez, Ignacio (2016). "An Unexpected Early Rhabdodontid from Europe (Lower Cretaceous of Salas de los Infantes, Burgos Province, Spain) and a Re-Examination of Basal Iguanodontian Relationships". PLOS ONE. 11 (6): e0156251. Bibcode:2016PLoSO..1156251D. doi:10.1371/journal.pone.0156251. PMC 4917257. PMID 27333279.
4. Madzia, D.; Arbour, V.M.; Boyd, C.A.; Farke, A.A.; Cruzado-Caballero, P.; Evans, D.C. (2021). "The phylogenetic nomenclature of ornithischian dinosaurs". PeerJ. 9: e12362. doi:10.7717/peerj.12362. PMC 8667728. PMID 34966571.
5. Dieudonné, P.-E.; Cruzado-Caballero, P.; Godefroit, P.; Tortosa, T. (2020-07-20). "A new phylogeny of cerapodan dinosaurs" (PDF). Historical Biology. 33 (10): 2335–2355. doi:10.1080/08912963.2020.1793979. ISSN 0891-2963. S2CID 221854017.
6. Poole K. 2022. "Phylogeny of iguanodontian dinosaurs and the evolution of quadrupedality". Palaeontologia Electronica. 25(3):1–65
7. Fonseca, A.O.; Reid, I.J.; Venner, A.; Duncan, R.J.; Garcia, M.S.; Müller, R.T. (2024). "A comprehensive phylogenetic analysis on early ornithischian evolution". Journal of Systematic Palaeontology. 22 (1): 2346577. doi:10.1080/14772019.2024.2346577.
8. Zanno, Lindsay E.; Gates, Terry A.; Ayrahami, Haviv M.; Tucker, Ryan T.; Makovicky, Peter J. (2023). "An early-diverging iguanodontian (Dinosauria: Rhabdodontomorpha) from the Late Cretaceous of North America". PLOS ONE. 18 (6). e0286042. doi:10.1371/journal.pone.0286042. PMC 10246810. PMID 37285376.