Fig. 93. Ophthalmosaurus icenicus. A ) complete skeleton, redrawn fro m A ndrew s (1910). B) skull, based largely on K ir to n (1983). Scales
equal 200 and 100 mm, respectively.
block in which the specimen appears to be preserved. It is,
therefore, possible that the posterior margin of the coracoid
is an erosional feature, but this cannot be determined
without examining the original material. The highly unusual
shape of the radius of the only preserved forefin
suggested a misidentification, and this was confirmed in a
later paper (Arkhangelsky, 1998A: 87). Arkhangelsky’s
(1998A: 87-88) emended diagnosis is entirely consistent
with that of Ophthalmosaurus, with the single exception of
the femur having three distal facets instead of two. Arkhangelsky’s
(1998A: fig. 2[1]) illustration appears to be a
femur, rather than a misidentified humerus, and this is
depicted as having three distal facets, which is atypical of
Ophthalmosaurus. However, whereas the humerus is well
known for Ophthalmosaurus because of the abundance of
material, femora are scarce. The range of individual variation
in the femur of Ophthalmosaurus icenicus is thus unknown,
and it is possible that some individuals might have
three distal facets instead of two - there are three digits in
the hindlimb. Given the close correspondence with Ophthalmosaurus
in all other regards, it is concluded that
Paraophthalmosaurus should be synonymized with that
genus, as suggested by Maisch & Matzke (2000B).
Efimov’s (1999A: 92, figs. 1-6) account of Yasykovia,
from the Upper Jurassic (Volgian) of the Ul’yanovsk and
Moscow regions of Russia, included brief comparisons
with Leptopterygius (now referred to Leptonectes), Eurhino~
saurus, Stenopterygius, Temnodontosaurus, Platypterygius,
and Plutoniosaurus, but not, surprisingly, with Ophthalmosaurus.
Four species were referred to the genus. The most
complete, Yasykovia yasykovi, comprises a partial skeleton
with an incomplete skull, partial and scattered forefins,
pectoral girdle, ribs and vertebrae from the upper Volgian
of the Ul’yanovsk Region. The figure of the holotype (Efimov,
1999A: fig. 1), like most of the other figures, lacks
detail, but there are also figures of the pelvic girdle (fig. 5)
and partial forefins (fig. 6) of some of the referred species,
which add to the picture. The humerus has three distal
facets, the anterior one, the smallest, being for articulation
with a semilunar element described as the “prepollex”. The
middle facet, for the radius, is the largest. The ulna facet is
set at an oblique angle to the radial facet such that its
posterior margin lies well proximal to its anterior one. In
all these features, Yasykovia corresponds with Ophthalmosaurus.
The humerus is wider proximally than distally,
which is the converse of the usual situation in Ophthalmosaurus,
but this is not unprecedented because the shape of
the humerus is markedly influenced by the extent and
direction of preservational compression. The fused pubis
and ischium are just like those in Ophthalmosaurus, as are
the large orbit and small, loosely attached teeth. Although
the teeth are depicted with slender crowns and greatly
inflated roots (Efimov, 1999A: fig. 2), they do not differ
significantly from Kirton’s (1983: 70-72) description for
Ophthalmosaurus. There can be little doubt that Yasykovia is
synonymous with Ophthalmosaurus.
Plate 16
Ophthalmosaurus icenicus, skull of mounted skeleton, BMNH R3702, partially restored. Scale measures 500 mm.
Maisch & Matzke (2000B: 91) synonymized Mollesau-
rus with Ophthalmosaurus, saying that the former was distinguished
from the latter “merely by the somewhat longer
postorbital segment.” However, FernAndez (1999) clearly
showed that the postorbital region of Mollesaurus was
much broader than in Ophthalmosaurus. Maisch & Matzke
(2000B: 91) went on to say that the “reduced extracondylar
area of the basioccipital [of Mollesaurus] is a character of all
ophthalmosaurids”. This is clearly incorrect because the
extracondylar area is quite extensive in Ophthalmosaurus.
Perhaps the most significant difference between the two
genera is the remarkably small scleral ring in Mollesaurus,
but Maisch & Matzke (2000B: 91) made no mention of this
feature. Maisch & Matzke (2000B) also synonymized Un-
dorosaurus Efimov, 1999B with Ophthalmosaurus, but, as
discussed later, there are grounds for maintaining their
separate generic identities.
Ophthalmosaurus icenicus Seeley, 1874
Fig. 93; Pis. 16-17
Ichthyosaurus megalodeirus Seeley, 1 869: 111 [nomen nu dum]
Ophthalmosaurus icenicus Seeley, 1874: 707
Ophthalmosaurus pleydelli Mansel-Pleydell, 1890: 15
Ophthalmosaurus monocharactus A ppleby, 1956: 444
Ophthalmosaurus undorensis Efimov, 1991: 112
Khudiakovia calloviensis A rkhangelsky, 1999: 89
Yasykovia yasykovi Efimov, 1999A: 93
Yasykovia mittai Efimov, 1999A: 96
Yasykovia sumini Efimov, 1999A: 96
Yasykovia kabanovi Efimov, 1999A: 97
Holotype: BMNH R2133, an incomplete, dislocated skeleton,
comprising pectoral girdle, cranial elements, posterior
segment of left mandibular ramus, much of the vertebral
column, rib fragments, and limb elements.
Diagnosis: As for genus.