Fig 1.
Locality map and stratigraphic column for Sirindhorna.
(A) Map of Nakhon Ratchasima Province, Thailand, (B) localities of Sirindhorna (star mark), Ratchasimasuarus (R) and Siamodon (S), (C) stratigraphic column for the Khorat Group (after [19]).
Table 1.
Measurements of described materials from Ban Saphan Hin.
Fig 2.
Articulated skull (braincase) of Sirindhorna (NRRU3001-166).
In dorsal (A), ventral (B), rostarl (C), and caudal (D) views. Abbreviations: Bso, basioccipital; bpt.pr, basipterygoid process; Bsp, basisphenoid; b.t., basal tubera; Exo, exoccipital; F, frontal; i.c, groove for the inter carotid; Lsp, laterosphenoid; m.pr, median process; ol.t, olfactory tract; Op, opisthostic; Osp, orbitosphenoid; P, parietal; Pro, paroccipital; prcp.pr, precotyloid process; Po, postorbital; Pr, prootic; Prsp, presphenoid; Psp, parasphenoid; q.c, quadrate cotylus; Spo, spraoccipital; s.cr, sagittal crest; Sq, squamosal. Italic Roman number indicates cranial nerves. Left paroccipital process was lacked when taking photos. Scale bars equal 10 cm.
Fig 3.
Photo (A) and line drawing (B) of the left lateral side of the skull (NRRU3001-166).
Abbreviations: Bso, basioccipital; bpt.pr, basipterygoid process; Bsp, basisphenoid; b.t, basal tubera; Exo, exoccipital; F, frontal; i.c, groove for the inter carotid; Lsp, laterosphenoid; Op, opisthostic; Osp, orbitosphenoid; P, parietal; Pro, paroccipital; prcp.pr, precotyloid process; Po, postorbital; Pr, prootic; Prsp, presphenoid; Psp, parasphenoid; q.c, quadrate cotylus; s.cr, sagittal crest; Sq, squamosal; sw, swelling. Italic Roman number indicates cranial nerves. Scale bar equals 10 cm.
Fig 4.
The articulated braincase (NRRU-A2035) in dorsal (A) and ventral views (B), the caudal portion of braincase (NRRU3001-179) in rostral view (C), and the dorsal part of braincase (NRRU3001-65) in ventral view (D). Abbreviations; Bso, basioccipital; bpt.pr, basipterygoid process; Bsp, basisphenoid; b.t, basal tubera; clm, cavity for the cerebellum; Exo, exoccipital; F, frontal; i.c, groove for the inter carotid; Lsp, laterosphenoid; Op, opisthostic; Osp, orbitosphenoid; P, parietal; p.c, pituitary cavity; Pro, paroccipital; prc.pr, precotyloid process; Po, postorbital; Pr, prootic; Prsph, presphenoid; q.c, quadrate cotylus; q.c, quadrate cotylus; s.cr, sagittal crest; Sq, squamosal. Italic Roman number indicates cranial nerves. Scale bars equal 10 cm.
Fig 5.
Right premaxilla (NRRU-A3623) of Sirindhorna.
In lateral (A), medial (B), ventral (C) views. Abbreviations: dnt, denticulation; f, foramen; m.art, maxillary articulation; m.pr, maxillary process; n.pr, nasal process; pm.st, suture for the adjacent premaxilla; prj, projection. Scale bar equals 10 cm.
Fig 6.
The left maxilla (NRRU-A2048) of Sirindhorna.
In lateral (A), ventral (B), medial (C), occulusal (D) views. Abbreviations: ect.fc, ectpterigoid facet; j.pr, jugal process; l. pr, lacrymal process; m.gr, maxillary grooves; nv.f, neurovascular foramen; pm.gr, premaxillary groove; rd.pr, rostrodorsal process; rv.pr, rostroventral process. Scale bar equals 10 cm.
Fig 7.
Right jugal (NRRU3001-7) and quadrate (NRRU3001-175) of Sirindhorna.
The right jugal in lateral (A), medial (B) views. The right quadrate in lateral (C),caudal (D), and distal (E) views. Abbreviations: d.pr, dorsal process; ect.fc, ectpterigoidal facet; l.fc, lacrymal facet; m.fc, maxillary facet; po.st, postorbital suture; pt.w, pterygoid wing; q.f, quadrate foramen; r.pr, rostral process. Scale bar equals 10 cm.
Fig 8.
Predentary (NRRU3001-169) of Sirindhorna.
In rostroventral (A), right lateral (B), occulsal (C), caudoventral (D) views. Abbreviations: dnt, denticle of the predentary; dp, depression; gr, groove; m.dent, median denticle; nv.f, neulovascular foramen; v.pr, ventral process. Scale bar equals 10 cm.
Fig 9.
Caudal portion of left dentary (NRRU3001-14).
In labial (A), occulusal (B), lingual (C) views. Abbreviations: alv.p, alveolar parapet; c.pr, coronoid process; c.r, cheek recess; M.c, Meckelian canal; nv.f, neurovascular foramen; 1r.t, first replacement tooth; 2r.t, second replacement tooth. Scale bar equals 10 cm.
Fig 10.
Right dentary (NRRU3001-167) of Sirindhorna.
In labial (A), lingual (B), and occulusal (C) views. Abbreviations: alv.tr, alveolar trough; c.pr, coronoid process; gr, groove; nv.f, neulovascular foramen; sym, symphysis; v.pr, ventral process. Scale bar equals 10 cm.
Fig 11.
Right suranguar (NRRU3001-137) of Sirindhorna.
In lateral (A), medial (B), ventral (C), and dorsal (D) views. Abbreviations: a.fs, adductor fossa; a.fc, articular facet; an.fc, angular facet; gl, glenod; l.l, lateral lip; sr.f, surangular foramen. Scale bar equals 10 cm.
Fig 12.
Maxillary and dentary teeth of Sirindhorna.
Isolated left maxillary teeth in labial (A; NRRU-A1959) and mesial (B) views (NRRU-A3630). An isolated dentary tooth (NRRU3001-28) in lingual (C) and distal (D) views. Lingual side of 4—5th preserved teeth of the dentary (NRRU3001-14) (E) and mammilations on denticles (F) on the apical edge from white squared area in E. Abbreviations: acc, accesory ridges; dnt, denticle; ml, mammilation; pr, primary ridge; sc, secondary ridge; t.f, facet for an adjacent tooth. Scale bars equal 5 mm.
Fig 13.
Comparison of the skull roof in dorsal view.
(A) Holotype of Sirindhorna (NRRU3001-166), (B) referred material of Sirindhorna (NRRU-A2035), (C) Dakodadon (SDSM 8656), (D) Jinzhousaurus (IVPP-V12691), (E) Mantellisaurus (after [38]) and (F) Probactrosaurus (after [5]). Abbreviations; F, frontal; fp.st, frontoparietal suture; P. parietal; Po, Postorbital; Pro, prootic; s.cr, sagittal crest; Sq, squamousal. Scale bar equals 10 cm.
Fig 14.
One MPT showing the phylogenetic position of Sirindhorna khoratensis based upon the data matrix of [37].
Definitions of the clade follow [37]. Bremer support indices are indicated on the right side of relevant branches.
Fig 15.
Comparisons with other Thailand iguanodontians.
(A) Holotypic left maxilla of Siamodon (after [16]), (B) holotypic right dentary of Ratchasimasaurus (from [17]), (C) left maxilla of Sirindhorna (NRRU-A2048), (D) left dentary of Sirindhorna (NRRU3001-167). Scale bars equal 10 cm.
Fig 16.
Skull of Sirindhorna khoratensis.
(A) A composite skull reconstruction of Sirindhorna. Several elements are reversed. (B) Life restoration of the head of Sirindhorna by Yoko Ohnish. Scale bar equals 10 cm. Dashed line indicates missing elements.