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Owenodon

Galton, 2009 o-wen-o-don

Named for Richard Owen, the British paleontologist who first described the specimen, combined with Greek 'odon' meaning 'tooth'.

143.1–137.1 million years ago Berriasian, Early Cretaceous
Early Cretaceous stages

Owenodon is a genus of iguanodontian dinosaur known from a partial lower jaw discovered in Early Cretaceous-aged rocks of Dorset, United Kingdom, and possibly also Romania and Spain. The first and only definitive specimen was found in the Durlston Formation of the Purbeck Limestone Group, dating to the middle Berriasian stage.

Under dispute

Owenodon hoggii is known from a single partial dentary, and its position among dryomorphs is unstable. Galton (2009) erected the genus for material more derived than Camptosaurus, judging that it represents an unnamed clade fitting between Camptosauridae and Styracosterna and could tentatively be referred to the latter; Galton also referred dentary teeth and several bones from Cornet, Romania, to Owenodon sp. Norman (2012) instead regards the holotype as a camptosaur-grade iguanodontian. Madzia, Jagt and Mulder (2019) recover it within Styracosterna in their majority-rule consensus but in an unresolved polytomy within Ankylopollexia in the strict consensus, and Madzia and colleagues (2021) list it in Styracosterna on that tree, while the implied-weighting analysis of Herne and colleagues (2019) recovers it as the sister of Camptosaurus and Iguanodon, outside Ankylopollexia. It is placed at Dryomorpha incertae sedis, the least inclusive clade common to these hypotheses. The adequacy of the genus's diagnosis is also contested. Galton (2009) separated the holotype from Camptosaurus on a dentary that is deeper relative to its length, an arched dental margin and tooth row, and a longer symphyseal ramus, together with details of the tooth crowns. Norman (2012) rejected the first two characters, holding that the severe postmortem crushing of the dentary cannot be ruled out as their cause, and held the symphysis unmeasurable because that part of the jaw is abraded, leaving fine details of the individual tooth crowns as the only distinguishing features. On that basis Norman judged the erection of a separate genus a matter of opinion resting more on the specimen's stratigraphic and geographic separation from Camptosaurus than on the weight of the anatomy, called its taxonomic status provisional, and urged the collection of more material. That reassessment nonetheless retained the binomial and published an emended diagnosis, and later work has continued to treat Owenodon as a distinct genus (Madzia and colleagues, 2021; Fonseca and colleagues, 2024). It is retained as a valid genus.

Diagnosis

  1. Lingual surface of the tooth crowns equally subdivided by a primary and a secondary ridge that are equal in prominence, well-defined, narrow, raised, and parallel (potential autapomorphy).
  2. Tertiary ridges, originating from the bases of the apical denticles and extending over the lingual crown surface, absent (potential autapomorphy).
  3. Marginal denticles simple and tongue-shaped, lacking mammillations.
  4. Denticulate margin at the distal corner of the crown not inrolled into an oblique cingulum bordering a vertical channel along the distal edge of the root.
  5. Fifteen alveoli, the most posterior curving laterally into the base of the coronoid process; coronoid process elevated but obliquely inclined posterodorsally and not anteroposteriorly expanded near its apex.
  6. No obvious diastema between the predentary-attachment area and the tooth-bearing margin of the dentary.

Species

Owenodon hoggii (Owen, 1874)

Type species

First named as Iguanodon hoggii

Named for naturalist A. J. Hogg, who originally collected the fossil mandible.

Holotype
NHMUK PV R 2998 , Natural History Museum
Material
Nearly complete right dentary with fifteen alveoli (several teeth missing), crushed transversely with the anterior tip broken.
Horizon
Lulworth Formation, Berriasian, Early Cretaceous , 143.1–137.1 million years ago
Locality
Durlston Bay, Dorset, United Kingdom Norman (2012) gives the dentary as "Collected from the 'Cherty freshwater beds'", the top of the Lulworth Formation below the Durlston Formation's basal Cinder Member (Clements, 1993), though he labels the horizon the Durlston Formation.

References

  1. Owen, R. (1874). Monograph on the fossil Reptilia of the Wealden and Purbeck Formations. Supplement No. V. Dinosauria (Iguanodon). Monographs of the Palaeontographical Society 27(124): 1-18. doi:10.1080/02693445.1874.12113258

    Names the species, conditionally, as Iguanodon Hoggii.

    owen1874b
  2. Galton, P. M. (2009). Notes on Neocomian (Lower Cretaceous) ornithopod dinosaurs from England - Hypsilophodon, Valdosaurus, "Camptosaurus", "Iguanodon" - and referred specimens from Romania and elsewhere. Revue de Paléobiologie, Genève 28(1): 211-273.

    Erects the genus for the NHMUK R2998 dentary and places it in an unnamed clade between Camptosauridae and Styracosterna.

    galton2009a
  3. Norman, D. B. (2012). Iguanodontian taxa (Dinosauria: Ornithischia) from the Lower Cretaceous of England and Belgium. Bernissart Dinosaurs and Early Cretaceous Terrestrial Ecosystems (Godefroit, P., ed.) 175-212. Indiana University Press, Bloomington.

    Emends the diagnosis; rejects the dentary-depth and tooth-row-arching characters because crushing cannot be ruled out as their cause, and regards the genus's status as provisional.

    norman2012a
  4. Clements, R. G. (1993). Type-section of the Purbeck Limestone Group, Durlston Bay, Swanage, Dorset. Proceedings of the Dorset Natural History and Archaeological Society 114: 181-206.

    Lists the Cherty Freshwater Member as the topmost member of the Lulworth Formation.

    clements1993a
  5. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the body length estimate.

    jones2026a
  6. 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

    Lists Owenodon hoggii in the composition of Styracosterna, under the majority-rule tree of Madzia, Jagt and Mulder (2019).

    madzia2021a
  7. Madzia, D.; Jagt, J. W. M.; Mulder, E. W. A. (2019). Osteology, phylogenetic affinities and taxonomic status of the enigmatic late Maastrichtian ornithopod taxon Orthomerus dolloi (Dinosauria, Ornithischia). Cretaceous Research 108: 104334. Elsevier BV. doi:10.1016/j.cretres.2019.104334

    Includes Owenodon hoggii; the strict consensus leaves it in an unresolved polytomy within Ankylopollexia, the majority-rule tree (Fig. 12) within Styracosterna.

    madzia2019a
  8. 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: 2346577. doi:10.1080/14772019.2024.2346577

    Reports, citing earlier analyses, that Owenodon falls near the root of Ankylopollexia or outside it; its own analyses do not include the genus.

    fonseca2024a
  9. Herne, M. C.; Nair, J. P.; Evans, A. R.; Tait, A. M. (2019). New small-bodied ornithopods (Dinosauria, Neornithischia) from the Early Cretaceous Wonthaggi Formation (Strzelecki Group) of the Australian-Antarctic rift system, with revision of Qantassaurus intrepidus Rich and Vickers-Rich, 1999. Journal of Paleontology 93(3): 543-584. Cambridge University Press (CUP). doi:10.1017/jpa.2018.95

    Includes Owenodon hoggii; the implied-weighting strict consensus recovers it as the sister of Camptosaurus and Iguanodon within Dryomorpha, and the equal-weighting tree leaves it unresolved there.

    herne2019a