An unexpected early-diverging iguanodontian dinosaur (Ornithischia, Ornithopoda) from the Upper Jurassic of Portugal

ABSTRACT

Iguanodontia is a diverse clade of herbivorous ornithischian dinosaurs that were speciose and abundant during the Jurassic and Cretaceous. Although the monophyly of Iguanodontia is well supported, their internal relationships have sparked heated debate due to several phylogenetic paradigm shifts. Late Jurassic basally branching iguanodontians in particular are not well understood in terms of their systematic affinities and evolutionary relevance. Their fossil record in Europe is meager compared with North America, with only a few species currently recognized. Two taxa are currently known from the Upper Jurassic of England, the basally branching styracosternan Cumnoria prestwichii and the putative dryosaurid Callovosaurus leedsi. In the Upper Jurassic of Portugal, the styracosternan Draconyx loureiroi and the dryosaurid Eousdryosaurus nanohallucis are presently the only described basally branching iguanodontians. Here we report a new species of early diverging iguanodontian from the Upper Jurassic Lourinhã Formation of western-central Portugal. The new species is clearly distinguished from all other coeval taxa by an exclusive combination of characters that include a tibia with a cnemial crest that is directed craniolaterally and a fibular condyle that is angled at 90° with respect to the proximal epiphysis, a fibula with symmetrical proximal margins, and a reduced metatarsal I. The phylogenetic relationships of the Lourinhã iguanodontian were explored using maximum parsimony and Bayesian inference. The two analyses recover the Lourinhã iguanodontian as an indeterminate dryomorphan, with more precise affinities precluded due to the current available material. Body size is estimated between 3 and 4 meters for the holotype specimen, adding to the diversity of small ornithopods already recognized in the paleoichnological record of the Lourinhã Formation.

http://zoobank.org/urn:lsid:zoobank.org:pub:5F4D52D0-0F0B-4809-8561-BE58C7C97D45

ACKNOWLEDGMENTS

We deeply thank all the workers and volunteers of Museu da Lourinhã. We thank also S. Rozadilla, P. Godoy, the editor S. Salisbury and an anonymous reviewer who greatly improved the quality of this manuscript. This research is funded by the Fundação para Ciência e a Tecnologia, I. P. with National Funds from the Ministério da Ciência, Tecnologia e Ensino Superior. Grant numbers: UIDB/04035/2020, GeoBioTec; PTDC/CTA-PAL/2217/2021, BioGeoSauria; and SFRH/BD/146230/2019 PhD fellowship (FMR). MMA is supported by the MCIN/AEI/10.13039/501100011033 and co-financed by the NextGeneration EU/PRTR, Ramón y Cajal contract RYC2021-034473-I, and Ministerio de Ciencia e Innnovación with the grant PID2021-122612OB-100. FMR benefited from the Jurassic Foundation grant that funded collection visit for data collecting.

DATA AVAILABILITY STATEMENT

The data matrix and the files needed to replicate the analyses performed in this study are provided as supplementary files.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

AUTHOR CONTRIBUTIONS

FMR and MMA designed the project, FMR and LF gathered the paleontological data, OM and MMA led the field campaign, OM found the specimen, CS gathered the geological data, FMR, LF, and CS drafted the manuscript, FMR, BC, and MMA discussed the results. All authors edited the manuscript.

SUPPLEMENTARY FILES

Supplementary File 1.nex: nexus file to replicate the bayesian clock analysis. (file name: Bayes_Clock_analysis.nex)

Supplementary File 2.nex: nexus file to replicate the bayesian non-clock analysis. (file name: Bayes_NonClock_analysis.nex)

Supplementary File 3.tnt: tnt file excluding Portuguese taxa. (file name:ML2700_Ord_NOPT.tnt)

Supplementary File 4.tnt: tnt file including Portuguese taxa. (file name: ML2700_Ord_PT.tnt)

Supplementary File 5.run: script to replicate the parsimony analyses. (file name: parsimony.run)

Supplementary File 6.tre: trees from parsimony analysis using Equal Weighting excluding Portuguese taxa. (file name:NOPT_EW.tre)

Supplementary File 7.tre: trees from parsimony analysis using K15 implied weighting excluding Portuguese taxa. (file name:NOPT_k15.tre)

Supplementary File 8.tre: trees from parsimony analysis using Equal Weighting including Portuguese taxa. (file name: PT_EW.tre)

Supplementary File 9.tre: trees from parsimony analysis using using K15 implied weighting including Portuguese taxa. (file name: PT_k15.tre)

Supplementary File 10.nex: matrix in nexus format excluding portuguese taxa. (file name: NOPT_matrix.nex)

Supplementary File 11.nex: matrix in nexus format including portuguese taxa. (file name: PT_matrix.nex)