A new species of large, long-snouted ichthyosaur from the English lower Lias

Abstract

A large ichthyosaur, with a total length in excess of 7 m, is described from the Lower Jurassic (Sinemurian) of Dorset, England. Like Leptopterygius tenuirostris the new species, named Leptopterygius solei, has a long slender snout armed with slender teeth that are remarkably small for the large size of the skull. There are also similarities in the forefin: the humerus is widely expanded distally, and the phalanges are rounded rather than polygonal and are probably well spaced distally. However, in contrast to L. tenuirostris, there is no notch on the leading edge of the radius. The snout is also relatively shorter and the orbit smaller. Thus in the holotype the estimated values for the snout and orbital ratios are 0.68 and 0.15 respectively, compared with observed ranges for L. tenuirostris of 0.71–0.76 (n = 7) and 0.18–0.24 (n = 7). Leptopterygius solei also has a somewhat higher prepelvic vertebral count, being at least 50 in the holotype compared with an observed range of 44–48 (n = 9) for L. tenuirostris. Furthermore, the ischium is considerably wider than the pubis, whereas these elements have approximately similar widths in L. tenuirostris. The possibility that the new material might merely represent the upper end of a growth series of L. tenuirostris is dismissed. Based on skull length, the holotype of L. solei is 66% larger than the largest specimen of L. tenuirostris.

First report of Leptonectes (Ichthyosauria: Leptonectidae) from the Lower Jurassic (Pliensbachian) of Asturias, northern Spain

“…The one located more anteriorly, interpreted as the radius, is roughly as long as wide (length = 47.3 mm; width = 55 mm) and, as in Leptonectes solei and L. moorei, is not notched. Contrary to the condition present in most of the specimens of L. tenuirostris (McGowan, 1993), the foramen between the occlusal edges of the radius and ulna is absent. The ulna is wider than long (antero-posterior width = 62 mm; proximo-distal length = 48 mm), and the proximal and distal articular facets are parallel and almost straight.…”

“…Within the genus Leptonectes, besides the type species L. tenuirostris Conybeare, 1822, there are two other valid species: L. solei McGowan, 1993and L. moorei McGowan and Milner, 1999(McGowan and Motani, 2003Lomax, 2016). Leptonectes tenuirostris is well known by several specimens (McGowan, 1989), and it has the longest stratigraphic range (probably from the Rhaetian up to the late Pliensbachian, Maisch and Reisdorf, 2006), and the widest geographic occurrence among leptonectids, including records from England (McGowan, 1996), Belgium (Godefroit, 1992), Germany (Maisch, 1999) and Switzerland (Maisch and Reisdorf, 2006).…”

“…Leptonectes tenuirostris is well known by several specimens (McGowan, 1989), and it has the longest stratigraphic range (probably from the Rhaetian up to the late Pliensbachian, Maisch and Reisdorf, 2006), and the widest geographic occurrence among leptonectids, including records from England (McGowan, 1996), Belgium (Godefroit, 1992), Germany (Maisch, 1999) and Switzerland (Maisch and Reisdorf, 2006). In contrast, L. solei and L. moorei are geographically restricted to Dorset (England), and stratigraphically to the Sinemurian (Obtusum Zone) (McGowan, 1993), and early Pliensbachian (McGowan and Milner, 1999), respectively.…”

A new leptonectid ichthyosaur from the Lower Jurassic (Hettangian) of Nottinghamshire, England, UK, and the taxonomic usefulness of the ichthyosaurian coracoid

“…Three other features may be autapomorphies: humerus deltopectoral crest prominent and 2.5 times greater than the dorsal process; dorsoventral width of the humerus is greater than the anteroposterior width, which results in a D-shape in proximal view; and slender, long, needle-like teeth with marginally recurved crowns and large, bulbous infolded roots. Wahlisaurus massarae is also characterized by the following combination of features shared with other taxa: very slender, delicate and relatively long snout (as in all leptonectids) with mandible shorter than snout, which produces an overbite (shared with Eurhinosaurus, Excalibosaurus and some specimens of Leptonectes tenuirostris; McGowan 1989aMcGowan , 1994aMcGowan , 1996McGowan , 2003 Maxwell et al 2012); extensive contact between the anterolateral border of coracoid (lateral scapular facet and medial scapular facet) and scapula forms a small, semi-circular scapularcoracoid foramen, similar contact has been reported in some specimens of Stenopterygius and Paraophthalmosaurus (Johnson 1979;Efimov 1999) and is here noted in some specimens of Leptonectes tenuirostris (e.g. McGowan 1974, fig.…”

“…The wealth of Lower Jurassic ichthyosaur specimens in the UK has significantly contributed to our understanding of ichthyosaurs from this time interval (e.g. McGowan 1974McGowan , 1989aMcGowan , 1993McGowan , 1996Benton & Taylor 1984;Delair 1969).…”