Fig 1.
A, Outcrop and subcrop map of the onshore Upper Jurassic Kimmeridge Clay Formation, showing the locality of Kimmeridge on the English South Coast, and sea coverage over the United Kingdom during the Late Jurassic. Outcrop and sea coverage data after Martill et al. [21], and Foffa et al. [22].
Fig 2.
Map showing the Kimmeridge Clay Formation outcrop in Dorset, southern England.
The White Stone Band is exposed between Rope Lake Head and Freshwater Steps. Star indicates the locality of MJML K1885. Base map data from Lees et al. [23].
Fig 3.
A, Generalised sedimentary log of the exposure from Kimmeridge Bay to Chapmans Pool, with ammonite zonation. Stratigraphy and ammonite zonation after Cox & Gallois [26]. B, exposure of the White Stone Band at beach level. C, laminae on a fallen block with an organic rich layer. D, bioturbation on a bedding surface on a fallen block. Scale bar for B, C and D represents 50 mm.
Fig 4.
Anterior portion on the main block of Thalassodraco etchesi, MJML K 1885.
A, photograph showing area restored during preparation. B, interpretive drawing of anterior portion of the skeleton. Scale bar represents 300 mm. Photograph used by permission of the Etches Collection under the CC BY 40 license, original copyright 2016.
Fig 5.
Isolated slabs of Thalassodraco etchesi.
A, MJML K1885, B, MJML K1885, C, MJML K1896. Scale represents 100 mm.
Fig 6.
Skeletal reconstruction of Thalassodraco etchesi MJML K 1885.
Grey areas indicating bones present. Scale represents 1 m.
Fig 7.
Skull of Thalassodraco etchesi, MJML K 1885.
A, photograph of the holotype skull. B, interpretation of skull. Abbreviations: an, angular; ar, articular; d, dentary; exn, external naris; Fo, foramen; fr, frontals; G, groove;hy, hyoid; in, indeterminate; inf, internasal foramen; j, jugal; l, lachrymal; m, maxilla; n, nasal; op, opisthotic; pa, parietal; pal, palatine; pf, postfrontal; pnf, pineal foramen; pm, premaxillae; po, postorbital; pr, prefrontal; pt, pterygoid; q, quadrate; qj, quadratojugal; s, supratemporal; sa, surangular; scl, sclerotic ring; sq, squamosal; st, stapes; stf, supratemporal fenestra; v, vomer. Scale bar 100 mm. Photograph used by permission of the Etches Collection under the CC BY 40 license, original copyright 2016.
Fig 8.
The anterior portion of the skull of Thalassodraco etchesi MJML K 1885.
A, photograph of the anterior portion of the skull. B, annotated interpretation. See caption for Fig 7 for abbreviations. Scale bar 50 mm.
Fig 9.
Posteroventral portion of the skull of Thalassodraco etchesi MJML K 1885.
A, photograph of the posteroventral portion of the skull. B, annotated interpretation. See caption for Fig 7 for abbreviations. Scale bar 50 mm.
Fig 10.
Dorsal portion of the skull of Thalassodraco etchesi MJML K 1885.
A, photograph of the dorsal portion of the skull. B, annotated interpretation. See caption for Fig 7 for abbreviations. Scale bar 50 mm.
Fig 11.
Supratemporal bone of Thalassodraco etchesi, MJML K 1885.
A, posterodorsal portion of the skull, with red box indicating the protuberance of the supratemporal. B, rugose texture on the supratemporal protuberance. Scale bar A, 10 mm; B, 5 mm.
Fig 12.
Dentition of Thalassodraco etchesi MJML K 1885, showing smooth enamel.
Scale bar 10 mm. Photograph used by permission of the Etches Collection under the CC BY 40 license, original copyright 2016.
Fig 13.
Atlas axis of Thalassodraco etchesi, MJML K 1885.
A, photograph of the atlas axis. B, labelled interpretive drawing of the atlas axis. Scale bar 20 mm.
Fig 14.
Neural spines of Thalassodraco etchesi, MJML K 1885.
A, photograph of the neural spines. B, interpretive line drawing of the neural spines, highlighting the lateral protuberance on the neural arch. Scale bar 10 mm.
Fig 15.
Pectoral girdle of Thalassodraco etchesi, MJML K1885.
A, photograph of preserved pectoral girdle. B, line diagram of pectoral girdle. C, annotated line diagram of clavicle. D, annotated line diagram of interclavicle. E, annotated line diagram of right scapular. F, annotated line diagram of coracoids. For line diagrams, areas of restoration have been reconstructed from preserved portions of the pectoral girdle and personal observations. Abbreviations; amp, anteromedial process; an, anterior notch; ar, acromial ridge; ap, acromial process; c, clavicle; cc, coracoid contribution; co, coracoid; gc, glenoid contribution; h, humerus; icf, intercoracoid facet; in, interclavicle; mr, medial ridge; s, scapular; sf, scapular facet. Red dotted line indicates restored sections. Scale bar 100 mm.
Fig 16.
Forelimb of Thalassodraco etchesi, K1885.
A, photograph of right forelimb. B, interpretation of forelimb. C, reconstruction of forelimb based on dorsal views of ulna and radius. D, interpretation of the humerus. E, dorsal surface of Ulna. F, dorsal surface of radius Abbreviations: dp, dorsal process; e, preaxial accessory element; ef, facet for preaxial accessory element; H, humerus; I, intermedium; pt, pitted texture; R, radius; r, radiale; rf, radial facet; U, ulna; u; ulnare; uf, ulnar facet. Scale bar 20 mm.
Fig 17.
Ischiopubis of Thalassodraco etchesi, MJML K1885.
A, photograph of isolated ischiopubis. B, line diagram of ischiopubis. Scale bar 20 mm.
Fig 18.
Phylogenetic position of Thalassodraco etchesi.
A, a strict consensus tree recovered from the analysis. Bremer support values >1 are shown above the branches, bootstrap support values greater than 20 are shown below the branches. B, the clade that Thalassodraco falls into, showing synapomorphic characters. Abbreviations: N, Nannopterygius clade; O, Ophthalmosaurinae.
Fig 19.
Summary of the taphonomic history of Thalassodraco etchesi, MJML K 1885.
A, B, the carcass drifts in the water column, with the heavier head directed to the seafloor. C, the heavier skull arrives on the seafloor, with the skull penetrating the soft sediment, until it hits the harder, dewatered sediment below. D, the carcass starts to collapse laterally. If the gut and lungs are filled with gas, the posterior portion will remain buoyant, remaining out of the sediment. E, the carcass collapses and decomposes. The portion within the sediment remains articulated, whereas the posterior and right lateral portions are exposed to scavenging and scattering of bones through current action. Arrows indicate later compaction of the specimen as the sediment dewaters. Modified from Martill [65, 66].
Fig 20.
Ossified ligaments and decayed internal organs of Thalassodraco etchesi, MJML K 1885.
A, ossified ligaments across the neural spines. B, SEM image of the ossified ligament. C, black material, presumed decayed internal organs, in the upper body cavity. D, magnified view of the black material in the body cavity. Scale bar in A, D represents 10 mm, B represents 200 μm and C, 100 mm. Photographs A, C, D used by permission of the Etches Collection under the CC BY 40 license, original copyright 2016.
Fig 21.
Comparisons with other Late Jurassic and Early Cretaceous ichthyosaurs.
A, Thalassodraco etchesi, MJML K1885, B, Undorosaurus gorodischensis, PMO 214. 578, C, Acamptonectes densus, GLAHM 132588, D, Ophthalmosaurus icenicus, NHMUK PV R2137, E, Nannopterygius enthekiodon, NHMUK PV 46497, F, Sveltonectes insolitus, IRSNB R269, G, Grendelius alekseevi, YKM 56702, H, Arthropterygius chrisorm, jugal, clavicle and scapular from specimen CCMGE 17-44/13328, interclavicle from specimen SGM 1573, coracoids and scapula from specimen CCMGE 3-16/13328, lacrymal from A. lundi PMO 222.654. ‘*’ indicating elements that have been mirrored for comparative purposes. Not to scale.