Brighstoneus simmondsi Lockwood &amp; Martill &amp; Maidment 2021, gen. et sp. nov
Creators: name: Lockwood, Jeremy A. F.
name: Martill, David M.
name: Maidment, Susannah C. R.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Ornithischia
Brighstoneus
Brighstoneus simmondsi

description: <i>Brighstoneus simmondsi</i> gen. et sp. nov . (Figs 3–22, 24) <b>Etymology.</b> The specific name honours Mr Keith Simmonds who made the discovery of the specimen. <b>Holotype.</b> 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. <b>Diagnosis.</b> 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 <b>*</b>; nasal expanded postnarially to produce a modest nasal bulla with convex lateral walls <b>*</b>. Acharacter 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, <i>Brighstoneus</i> 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&gt; 6.0; coronoid process projects at approximately 90 <b> °</b> 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 spurlike 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&gt; 1.2. Description Overall, MIWG 6344 is excellently preserved with little distortion or crushing (measurements are available in the Supplementary material). Many of the bones exhibit unusual eroded areas, which have left smooth, ‘scooped out’ regions extending down to and including the internal trabecular bone. Some of these areas are partially covered by the original sediment, suggesting these features formed prior to, or soon after, burial. It is unlikely that this damage resulted from prolonged subaerial exposure as the cortical surface is generally well preserved (Behrensmeyer 1978). As many of these eroded features are associated with highly cartilaginous regions, it is possible that they are examples of invertebrate bioerosion, potentially by isopterans (Britt <i>et al</i>. 2008, and references therein; Huchet <i>et al.</i> 2011), which are known from the Wealden Group (Jarzembowski 1981). The term ‘eroded’ is used in the descriptive text to indicate these areas. There is also evidence, particularly on the ribs, of shallow circular pits varying between 2–4 mm in diameter, which might represent dermestid beetle activity (Britt <i>et al</i>. 2008). Premaxilla Only the dorsal (nasal) process of the right premaxilla is preserved, but without its posterior-most tip (Fig. 3). In lateral view, the fragment has a long mediolaterally thin process, which is gently curved, convex dorsally and gradually tapers as it extends posteriorly. The lateral surface is rounded and grooved in the posterior threefifths of its length for contact with the anterodorsal process of the nasal (Fig. 3A: this area is described as ‘bevelled’ in <i>Mantellisaurus atherfieldensis</i> rather than grooved: Norman 1986). Anteriorly the ventral margin curves ventrally forming a thin blade of bone, which is incomplete but would have contributed to the internarial septum. The medial surface of the dorsal process is flat for articulation with its antimere. Maxilla Both maxillae are present, with the left being the better preserved. The left maxilla (Fig. 4) is almost complete, although it has lost parts of the anterior ends of the anteroventral and anterodorsal processes. Between the anterior processes a fragment of bone has been glued into a position that is probably anatomically incorrect (Fig. 4A, C). The ascending process is almost complete, having a thin fractured margin, but preserving the groove for reception of the maxillary process of the premaxilla. The maxilla has been subjected to minor transverse lateral compression that has slightly relocated the incomplete jugal process medially. The maxilla is a robust bone but is relatively thinner in dorsal and ventral views than that of <i>Mantellisaurus atherfieldensis</i> (NHMUK PV R5764). Its general shape in lateral view is of an anteroposteriorly expanded triangle. The apex is directed dorsally as the ascending process but is situated in a markedly posterior position, and if complete the section anterior to this process would have been approximately twice the length of the posterior section. Aratio of <b>~</b> 2.0 or higher is also seen in <i>Altirhinus kurzanovi</i> (2.1: Norman 1998), <i>Zhanghenglong yangchengensis</i> (2.3: Xing <i>et al</i>. 2014), <i>Protohadros byrdi</i> (2.3: Head 1998), <i>Proa valdearinnoensis</i> (2.4: McDonald <i>et al</i>. 2012a) and <i>Ouranosaurus nigeriensis</i> (2.6: Taquet 1976). In contrast the ratio is 1.4 in <i>Mantellisaurus atherfieldensis</i> (NHMUK PV R5764). In lateral view the ventral edge of the maxilla is shallowly concave, the tooth row being almost straight for most of its length. There are 29 tooth positions: most of the alveoli are empty but two established and two emerging replacement crowns are present (see below). In ventral view the tooth row is straight for most of its length but posteriorly the last quarter curves laterally. The bone preservation of the lateral surface is better in the right maxilla, which has eight small nutrient foramina (1–3 mm in diameter) that open anterolaterally and form an anteroposteriorly orientated row in the ventral half of the maxilla. Anteriorly, the ventral surface of the maxilla forms an anteroventral process that, although incomplete, follows the curve of the tooth row and tapers anteriorly in lateral view. The first alveolus is situated at the base of this process, anterior to which the process is edentulous. Although the area dorsal to the anteroventral process has suffered some damage, a prominent anterodorsal process is present. Posteriorly the transverse cross-section of this process is triangular with a gently dorsoventrally concave lateral surface, a flat ventromedial surface and a dorsomedial surface that is roughened and has a longitudinal groove in its posterior section. Extending anteriorly, the process becomes increasingly compressed transversely to form a thin blade, whose end is missing. Possession of an anterodorsal process is considered ancestral for Archosauria (Wagner &amp; Lehman 2009) and has been employed as a character in iguanodontian phylogeny (e.g. Sues &amp; Averianov 2009; Xing <i>et al</i>. 2014; McDonald <i>et al</i>. 2017). Its presence has been used to distinguish Saurolophinae from Lambeosaurinae (Wagner &amp; Lehman 2009), but it is also present in non-hadrosaurids such as <i>Altirhinus kurzanovi</i> (Norman 1998), <i>Bactrosaurus johnsoni</i> (Godefroit <i>et al</i>. 1998), <i>Eolambia caroljonesa</i> (CEUM 35492: McDonald <i>et al</i>. 2012b) and <i>Gilmoreosaurus mongoliensis</i> (Prieto-Marquez &amp; Norell 2010), and is especially prominent in <i>Protohadros byrdi</i> (Head 1998). The anterior and posterior dorsal edges of the lateral wall of the maxilla meet to form the apex of the transversely compressed ascending process. The jugal process arises from the base of the posterior edge of the ascending process (Fig. 4A, D). The trough between the jugal process and lateral body of the maxilla expands posteriorly to form a mediolaterally broad ectopterygoid shelf. When viewed dorsally the posterior maxilla is more ovoid (long axis anteroposterior) and the medial wall more convex than in <i>Mantellisaurus atherfieldensis</i> (NHMUK PV R5764). Below the apex of the ascending process and situated posteriorly is a depressed area, which would presumably have contributed to the antorbital fenestra and might have formed a small antorbital fossa (Fig. 4A). This depressed area is also present in <i>Iguanodon bernissartensis</i> (Norman 1980), <i>Mantellisaurus atherfieldensis</i> (NHMUK PV R5764), <i>Ouranosaurus nigeriensis</i> (Taquet 1976), <i>Camptosaurus dispar</i> (Gilmore 1909) and <i>Bolong yixianensis</i> (Wu &amp; Godefroit 2012). There is no evidence of an antorbital fenestra in <i>Altirhinus kurzanovi</i> (Norman 1998) or <i>Jinzhousaurus yangi</i> (Wang &amp; Xu 2001; Barrett <i>et al</i>. 2009) and this feature is not described in <i>Equijubus normani</i> (McDonald <i>et al</i>. 2014). Anteriorly, the lateral part of the dorsal surface is furrowed to form the premaxillary groove for contact with the premaxilla (Fig. 4A, B). Medially the maxilla has a vertical surface that has an elongate rectangular outline with the ascending process rising above its dorsal edge. Above the tooth row is a concave arcade of circular special foramina (<i>sensu</i> Edmund 1957) or replacement foramina (<i>sensu</i> Jin <i>et al</i>. 2010), the curve of which is considerably deeper than the ventral edge (Fig. 4C). Between the special foramina and the tooth row the bone is thin with a textured surface and forms the alveolar parapet. Dorsally there is a medial shelf that is damaged anteriorly but appears to have a rounded edge. Nasal Only the left nasal is preserved (Fig. 5). It is undistorted but broken at both ends, so missing the posterior articulation for the frontal and prefrontal. The nasal is elongate anteroposteriorly, relatively broad and convexly curved mediolaterally so that with its antimere the external surface formed a vault over the nasal cavity. Anteriorly the nasal is divided into two processes. The anterodorsal process is dorsoventrally deeper in lateral view than the anteroventral process. The anterodorsal section, which articulated with the dorsal process of the premaxilla, is incomplete but the area that contributed to the posterior margin of the external naris is intact. The base of the anteroventral process is present showing that the nasal also made a contribution to the posteroventral margin of the external naris. There is no anteroventral process in <i>Iguanodon bernissartensis</i> (Norman 1980), <i>Mantellisaurus atherfieldensis</i> (Norman 1986), <i>Protohadros byrdi</i> (Head 1998), <i>Bactrosaurus johnsoni</i> (Godefroit <i>et al</i>. 1998), <i>Equijubus normani</i> (McDonald <i>et al</i>. 2014) or <i>Gobihadros mongoliensis</i> (Tsogtbaatar <i>et al</i>. 2019). In hadrosaurids an anteroventral process is usually present, for example in <i>Maiasaura peeblesorum</i> and <i>Gryposaurus notabilis</i> (Prieto-Marquez &amp; Norell 2010) and is particularly prominent in <i>Brachylophosaurus canadensis</i> (Prieto-Marquez 2001) and <i>Edmontosaurus annectens</i> (Campione &amp; Evans 2011). Among non-hadrosaurid hadrosauriforms, an abbreviated anteroventral process is present in <i>Altirhinus kurzanovi</i> (Norman 1998), with longer processes in <i>Ouranosaurus nigeriensis</i> (Taquet 1976), <i>Jinzhousaurus yangi</i> (Wang &amp; Xu 2001; Barrett <i>et al</i>. 2009) and <i>Bolong yixianensis</i> (Wu &amp; Godefroit 2012). The posterior margin of the external naris is almost straight and posteroventrally orientated. The ventral border of the lateral surface of the nasal has a shallowly bevelled surface (Fig. 5C, E) and presumably underlapped the maxillary process of the premaxilla as a scarf joint, although anteriorly there is also a slight groove along the dorsal edge of this surface. The nasals of <i>Gobihadros mongoliensis</i> and <i>Choyrodon barsboldi</i> have a grooved ventrolateral surface (Tsogtbaatar <i>et al.</i> 2019) and both appear to underlap the posterolateral process of the premaxilla; <i>Bactrosaurus johnsoni</i> (Godefroit <i>et al.</i> 1998) and <i>Altirhinus kurzanovi</i> (Norman 1998) are grooved along their ventral borders. The medial border of the dorsal surface is grooved anteriorly in <i>Brighstoneus simmondsi</i>, presumably where it articulated with the dorsal process of the premaxilla, but tapers to a thin blade posteriorly that most likely formed a simple butt joint with its antimere (see Weishampel 1984) as in <i>Altirhinus kurzanovi</i> (Norman 1998) and <i>Jinzhousaurus yangi</i> (Barrett <i>et al.</i> 2009), although in <i>Ouranosaurus nigeriensis</i> the nasals are asymmetrical with one having a blade and the other a groove along the dorsal edge (Taquet 1976). When viewed laterally in life position the dorsal border of the nasal is sinusoidal and forms a distinct anterior convexity with the most dorsal part of the curve situated posterior to the posterior border of the external naris. The section of the lateral wall of the nasal, posterior to the naris, is slightly convex in ventral view. Collectively these features would have produced a rounded bulge and formed a distinct step between the anterior and posterior sections of the nasal (Fig. 5E). This is less prominent but similar in shape and position to the nasal bulla of the iguanodontian <i>Muttaburrasaurus langdoni</i> (Bartholomai &amp; Molnar 1981), although in <i>Muttaburrasaurus</i> the lateral walls are slightly concave. Ahigh arched region, dorsal to the posterior narial, is also seen in <i>Altirhinus kurzanovi</i> (Norman 1998), <i>Choyrodon barsboldi</i> (Gates <i>et al</i>. 2018) and in some hadrosaurids, for example <i>Gryposaurus notabilis</i> (Lambe 1914) and <i>Kritosaurus navajovius</i> (Brown 1910). <i>Ouranosaurus nigeriensis</i> also has a rounded protuberance, but this is situated more posteriorly on both nasals, just anterior to the suture for the frontals (Taquet 1976), while <i>Jinzhousaurus yangi</i> has mediolaterally convex nasals with a sagittal depression between them (Barrett <i>et al</i>. 2009), a feature also seen in <i>Altirhinus kurzanovi</i> (Norman 1998) and <i>Choyrodon barsboldi</i> (Gates <i>et al</i>. 2018). There is no evidence of a sagittal trough in <i>Brighstoneus simmondsi</i>. Temporal and geographical separation, together with the pattern of phylogenetic relationships and variety of morphologies in these examples, suggests that nasal ornamentation evolved independently on several occasions in iguanodontids. This feature also appears to be unique among the Wealden Group iguanodontids. Jugal Both jugals are preserved and are almost complete (Fig. 6). The dorsal sections of the postorbital process and the process overlapping the quadratojugal are broken. It is a triradiate bone with an anteriorly directed maxillary process, a central dorsally projecting postorbital process and a posterior dorsally projecting quadratojugal process. Both jugals are very straight and narrow in dorsal view (Fig. 6E, F) compared to <i>Mantellisaurus atherfieldensis</i> (NHMUK PV R5764), which is laterally convex with a relatively wider orbital shelf. The maxillary process in lateral view occupies 60% of the total length of the jugal (ratio of length anterior to midpoint of postorbital process/maximum length <b>¼</b> 0.60). This ratio varies considerably in iguanodontians, from 0.29 in <i>Xuwulong yueluni</i> (You <i>et al</i>. 2011) and 0.33 in <i>Iguanodon bernissartensis</i> (Norman 1980) to 0.56 in <i>Mantellisaurus atherfieldensis</i> (NHMUK PV R 5764) and 0.62 in <i>Ouranosaurus nigeriensis</i> (Taquet 1976). However, in most hadrosauriforms including hadrosaurids this ratio ranges between 0.40 and 0.54. For example, <i>Altirhinus kurszanovi</i> (0.46: Norman 1998), RBINS R57 (0.52: Norman 1986), <i>Equijubus normani</i> (0.49: You <i>et al</i>. 2003), <i>Eolambia caroljonesa</i> (0.48: McDonald <i>et al</i>. 2012b), <i>Brachylophosaurus canadensis</i> (0.51: Prieto-Marquez 2001) and <i>Gryposaurus latidens</i> (0.48: Prieto-Marquez 2012). The maxillary process in lateral view is gently curved with a convex ventral margin and a concave dorsal margin. The process is quite gracile and lacks the dorsoventral expansion seen in many hadrosauriforms, such as those present in <i>Probactrosaurus gobiensis</i> (Norman 2002); <i>Eolambia caroljonesa</i> (McDonald <i>et al.</i> 2012b) and <i>Gobihadros mongoliensis</i> (Tsogtbaatar <i>et al</i>. 2019), instead the anterior dorsal margin slopes anteroventrally to join the ventral margin as a point. This slope forms a facet for articulation with the lacrimal. Amaxillary process with a pointed end, lacking dorsoventral expansion, is also seen in <i>Altirhinus kurzanovi</i> (Norman 1998), <i>Batyrosaurus rozhdestvenskyi</i> (Godefroit <i>et al</i>. 2012), <i>Dakotadon lakotaensis</i> (Weishampel &amp; Bjork 1989) and <i>Choyrodon barsboldi</i> (Gates <i>et al</i>. 2018). The maxillary process of the jugal in <i>Mantellisaurus atherfieldensis</i> (NHMUK PV R 5764) is not dorsoventrally expanded but has a much blunter, less tapered anterior end, albeit with some damage ventrally. Medially the maxillary process is deeply excavated to form an anteroposteriorly elongate facet with a roughened surface for reception of the finger-like jugal process of the maxilla. The jugal is expanded medially at the posterior end of the maxillary facet to form a buttress (Fig. 6E, F) for the distal end of the jugal process of the maxilla. Posterior to the maxillary facet is a posterodorsally orientated ridge that separates the facet from a shallow oval fossa for the ectopterygoid. Between the maxillary and postorbital processes, the dorsal surface is concave in lateral view and provided a shelf, forming the ventral margin of the orbit. The orbit is bounded posteriorly by the postorbital process, which is long, straight and ascends perpendicular to the main axis of the jugal body. Dorsally it develops an anterolaterally facing facet for suture with a reciprocal facet on the jugal process of the postorbital. Between the postorbital process and the quadratojugal process is a ‘U’-shaped embayment that forms the ventral border of the lateral temporal fenestra. On its medial surface, the posterior and ventral margins of the fenestra have a subtle, smooth and shallowly convex rolled edge (Fig. 6B, C), which is not readily apparent in other hadrosauriforms, including <i>Mantellisaurus atherfieldensis</i> (NHMUK PV R 5764), <i>Eolambia caroljonesa</i> (McDonald <i>et al</i>. 2012b) and <i>Sirindhorna khoratensis</i> (Shibata <i>et al.</i> 2015). The right jugal has a nutrient foramen <b>~</b> 1 mm in diameter, located medially below the ventral border of the fenestra and postorbital process, while on the left jugal two foramina are present (with d
description: Published as part of <i>Lockwood, Jeremy A. F., Martill, David M. &amp; Maidment, Susannah C. R., 2021, A new hadrosauriform dinosaur from the Wessex Formation, Wealden Group (Early Cretaceous), of the Isle of Wight, southern England, pp. 847-888 in Journal of Systematic Palaeontology 19 (12)</i> on pages 5-31, DOI: 10.1080/14772019.2021.1978005, http://zenodo.org/record/5696995
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