Plate 17
Ophthalmosaurus icenicus, forefin of BMNH R3702 (not on mounted skeleton). Only the most proximal elements are
articulated, the positions of the remaining elements are hypothetical. Scale measures 100 mm.
Occurrence: Primarily from England: Peterborough, Northamptonshire;
Oxfordshire; Cambridgeshire; Dorsetshire;
Wiltshire. Also known from the Moscow and Ul’yanovsk
regions of Russia and from Le Havre, France.
Stratigraphic range: Oxford Clay; Middle-Upper Jurassic
(Callovian-Kimmeridgian).
Remarks: In listing the locations of various ichthyosaurs
from the Oxford Clay of Peterborough in the Woodward-
ian Museum, Seeley (1869: 111), mentioned that “the species,
which is new, may be named Ichthyosaurus megalodei-
rus.” Nothing more was said of the species. Given its locality
and horizon, the material is probably referable to Ophthalmosaurus.
Seeley (1874) made no reference to the name
in his subsequent work.
Appleby (1956) noted that the coracoid of the holotype
of Ophthalmosaurus icenicus had both an anterior and a
posterior notch. Almost all other material referable to Ophthalmosaurus
has only a single (anterior) notch. The only
other exception, beside the holotype, was a specimen in the
Leicester Museum (1 0 0 ’1 9 4 9 /2 0 ), comprising an isolated
pair of coracoids. As there were no intermediates between
the two conditions, he concluded that the two types represented
separate species. A ppleby erected the name Ophthalmosaurus
monocharactus io i the single-notched one. Cora-
coidal notching appears to be variable in some ichthyosau-
rian species (McGowan, 1979B: 104), and the same could
also be true for Ophthalmosaurus. The relatively minor differences
in the coracoid are thus considered insufficient to
warrant recognition of a separate species.
The humerus and associated elements described by
Arkhangelsky (1999) as a new genus and species (Khudi-
akovia calloviensis) from the Callovian of the Saratov Region
of Russia are entirely consistent with those of Ophthalmosaurus
icenicus, with which this species is synonymized
here. This also applies to the humerus and vertebrae described
by E fimov (1991: 112, figs. 1-2) as a new species,
Ophthalmosaurus undorensis.
Comparison between English and North American material:
Although plentiful, the English material is far less
complete than that from North America, making comparisons
difficult. Those differences that have been reported in
the literature, such as the purported narrower forefin in the
English material (Knight, 1 9 0 3 :7 7 ), probably all fall within
the normal range of variation for a single species. In the
absence of any significant differences, it is tempting to
refer all material to the type species. However, the more
conservative course, followed here, is to retain the oldest of
the North American species names, Ophthalmosaurus natans
(Marsh, 1879), for reception of the New World material.
The only differences reported here between D. nutans
and O. icenicus are geographic and stratigraphic.
Ophthalmosaurus natans (Marsh, 1879)
Sauranodon natans Marsh, 1879: 86
Sauranodon discus M arsh, 1880B: 171
Baptartodon marshi Knight, 1903: 81
Baptanodon natans; Gilmore, 1905: 120
Baptanodon discus; Gilmore, 1905: 121
Baptanodon marshi; Gilmore, 1905: 121
Baptanodon natans; Gilmore, 1906: 329
Baptanodon discus; Gilmore, 1906: 330, 335
Baptanodon robustus Gilmore, 1906: 332
Baptanodon reedi Gilmore, 1907:193
Mydbradypterygius mendozanus Rusconi, 1940: 2
Ancanamunid mendozanus; Rusconi, 1942: 2
Holotype: YPM 1952, a partial skeleton, mentioned by
Gilmore (1905: 120) as comprising part of a skull, several
vertebrae and ribs, and parts of one or more limb bones.
Diagnosis: As for genus.
Occurrence: The holotype was collected near Como Bluff,
Wyoming, USA. The inclusion of Rusconi’s (1940, 1942)
fragmentary material would extend the geographic range
to the Mendoza Province of Argentina.
Stratigraphic range: Sundance Formation; Upper Jurassic
(Oxfordian), The Argentine material is Middle Jurassic
(Callovian) in age.
Remarks: Ophthalmosaurus robustus (Gilmore, 1906) was
primarily defined on its large size, the vertebral centra
having diameters somewhat in excess of 10 cm. This is
quite large, but similar-sized specimens of Ophthalmosaurus
icenicus were reported by A ndrews (1910: 72).
Genus Brachypterygius Huene, 1922
Brachypterygius Huene, 1922: 97
Grendelius M cGowan, 1976: 671
Brachypterygius; McGowan, 1997: 429
Otschevia Efimov, 1998: 82
Otschevia; M aisch & M atzke, 2000B: 87
Type species: Brachypterygius extremus (Boulenger, 1904).
Diagnosis: Humerus with three distal facets of similar
size, the middle one for intermedium, the anterior and
posterior ones for radius and ulna. No fewer than five
digits, but likely not exceeding six; probably one preaxial
and one postaxial accessory digits, each arising from a
crescentic accessory element, neither one of which contacts
humerus; phalanges may be rectangular. Teeth numerous,
robust, unreduced, and well anchored in dental grooves.
Orbit small, orbital ratio < 0 .2 5 , and probably not exceeding
0.20; snout long, snout ratio >0.66; maxilla long and slender,
extending well forward of external nares, but premaxillary
ratio probably g®.42; nares set well back, prenarial
ratio > 0 .5 2 . Basioccipital with flat anterior surface that
lacks a basioccipital peg; extracondylar area less extensive