Fig. 76. Eurhinosaurus longirostris. A) complete skeleton. B) forefin. C) hindfin (SMF 4155). D) skull (MNHN 1946-20). Scales equal
1 m (A) and 200 mm, respectively.
Stratigraphic range: Upper Lias; Lower Jurassic (Toardan).
Remarks: Huene (1928) described a new and complete
skeleton of Eurhinosaurus that had just been purchased by
the Natural History Museum, London (BMNH R5465). At
that time only two other skeletons were known and Huene
noted that the new sperimen, which was smaller than the
other two, differed in certain features (McGowan, 1994B).
He concluded that it probably represented a new spedes,
but postponed formally naming it until more material
became available. Swinton (1930), impressed by the differences
that had been enumerated by Huene (1928), named
the new species E. huenei in his honor. Like Huene (1928),
he discussed the immaturity of the holotype (BMNH
R5465), but did not believe that its differences could be
attributed to ontogeny. Nor did he consider sexual dimorphism
to be a factor, although Huene (1928) had suggested
this may have been true for some of the features. Huene
(1931A, 1951A) revisited the situation after more specimens
of Eurhinosaurus had been found. Rejecting Swinton’s
species E. huenei, Huene concluded that Eurhinosaurus
was monotypic, and that the marked variability within
E. longirostris might be attributable to sexual dimorphism.
CM finds this a persuasive argument because there is a
dichotomy in some of the features that are not size-related,
and which cannot be attributed to ontogeny (McGowan,
1979B).
Reess (1986) argued that there was no tailbend in Eurhinosaurus,
and that the marked flexure seen in the vertebral
column of mounted skeletons was an artifact of preparation.
While conceding that the vertebrae in the caudal
Plate 4
Eurhinosaurus longirostris, skull of MNHP 1946-20. Scale measures 500 mm.
region did decrease in size, he claimed there was neither a
sudden decrease in size nor any wedge-shaped centra,
features that are indicative of a tailbend. However, wedge-
shaped centra do occur in Eurhinosaurus (McGowan,
1989A), and this has been confirmed by computed tomography
(McGowan, 1990A). However, the angle of the tailbend
was only about 40 degees to the horizon, not the
steeper angle of about 50 degrees as depicted by Hauff
(1953: pi. 21).*-,
Suprafamily Temnodontosauroidea nov.
Remarks: A superfamily comprising a single family named
solely for classificational convenience.
Family Temnodontosauridae M cG ow an ,
1974A
Genus Temnodontosaurus L yd ekker, 1889B
Temnodontosaurus L ydekker, 1889B: XI
Ichthyosaurus de la Beche & Conybeare; Owen 1881: 115
[partim]
Leptopterygius H uene 1922: 11 [partim]
Temnodontosaurus-, McGowan, 1974A: 9
Temnodontosaurus; McGowan, 1994A: 476
Temnodontosaurus; McGowan, 1996B: 1014
Type species: Temnodontosaurus platyodon (Conybeare,
1822).
Diagnosis: Forefin probably <5 digits; ulnare smaller than
intermedium; no digital bifurcation; at least some notching
in anterior-most elements of leading edge, sometimes involving
most elements; phalanges may be well spaced
distally; distal end of humerus markedly wider than proximal
end, probably with prominent preaxial facet. Pubis
and ischium separate, but may be partially fused. Preflexu-
ral vertebrae probably >80. Mandible not markedly shorter
than skull. Orbit relatively small, orbital ratio < 0.21, and
often <0.18; maxilla probably long, premaxillary ratio
< 0.43, but >0.32; external naris frequently large, prenarial
ratio >0.45; basioccipital with extensive extracondylar area
and probably a small basioccipital peg. Teeth of modest
size, largest ones at least 30 mm high and often >40 mm.
Large ichthyosaurs; skull, and jaw length >1 m in mature
individuals, and often >1.5 m; total length usually >6 m
and may reach 9 m.
Rema rks : Temnodontosaurus is one of the largest ichthyosaurs,
reaching a total length of about 9 m (McGowan,
1996B), although not as large as Shonisaurus and Himalaya-
saurus (McGowan & Motani, 1999; Motani e t al., 1999).
The anterior surface of the basioccipital is almost always
obscured in articulated skulls. On the evidence of a
large, free, basioccipital, it was concluded that a basioccipital
peg was absent in T. platyodon (McGowan, 1974A).
CM’s re-examination of this material (BMNH 2149), which
is associated with an atlas-axis (BMNH 2150*) and a string
of vertebrae (BMNH 481), shows that it does have an
incipient peg. Godefrou (1993A) has described two large,
fragmentary specimens of T. platyodon, from the Lower
Lias of southern Belgium, in which there is a small basioccipital
peg. There also appears to be a small peg in a
specimen of T. trigonodon (SMNS 50000). The implication
of this is that Temnodontosaurus does have a basioccipital