Brighstoneus simmondsi, Lockwood & Martill & Maidment, 2021

Lockwood, Jeremy A. F., Martill, David M. & Maidment, Susannah C. R., 2021, A new hadrosauriform dinosaur from the Wessex Formation, Wealden Group (Early Cretaceous), of the Isle of Wight, southern England, Journal of Systematic Palaeontology 19 (12), pp. 847-888 : 851

Brighstoneus simmondsi gen. et sp. nov.

( Figs 3–22, 24)

Etymology. The specific name honours Mr Keith Simmonds who made the discovery of the specimen.

Holotype. MIWG 6344 , a partial skeleton composed of the following elements: dorsal process of right premaxilla; both maxillae; both jugals; left palpebral; left nasal; both dentaries; predentary; one transitional dorsal and seven dorsal vertebrae; sacrum; six caudal vertebrae; dorsal ribs, nine from the left side and five from the right side; both ilia; right ischium; possible prepubic process; and the right femur. Some parts of the same individual (including two dorsal vertebrae and other fragments) remain in private ownership and are not described herein.

Diagnosis. Differs from all other iguanodontians by possessing the following autapomorphies and unique combination of characters (autapomorphies indicated with an asterisk): maxillary crowns possessing both a primary ridge and mesially placed accessory ridges on the lingual surface‡; nasal expanded postnarially to produce a modest nasal bulla with convex lateral walls‡. A character combination of at least 28 dentary tooth positions in a dentary with one active crown and one replacement tooth for each position and non-parallel alveolar septa.

In addition, Brighstoneus can be distinguished from other Barremian–Aptian Wealden Group iguanodontians by possession of the following combination of features: ratio of precoronoid length of the dentary to minimum depth> 6.0; coronoid process projects at approximately 90 ǫ with respect to the dorsal margin of dentary; bilobed ‘heart-shaped’ ventral predentary process with prominent anterior denticles with concave mesial and distal edges; posteriorly positioned maxillary ascending process in lateral view with length of the anterior section approximately twice the length of the posterior section; prominent anterodorsal process present on maxilla; anterior (maxillary) process of jugal relatively long (60% of overall length) and tapers distally to form a triangular ending; ventral section of the posterior margin of the jugal (heel) projects posteriorly to form a spur-like feature; in dorsal view the jugal is straight; ventral border overlapped by maxillary process of premaxilla; anteroventral nasal process forms posteroventral margin of external narial opening; ventral surface of ischiadic peduncle of ilium parallel with the anteroventral margin of the postacetabular process; ischiadic peduncle of ilium has flat lateral wall with no pronounced posterolateral boss; ventral shelf at base of iliac preacetabular process weakly developed; dorsoventrally deep preacetabular process with little or no axial twist; deep and short iliac central plate with ratio of depth to length> 1.2.