gantic ichthyosaur has been reported from the Lower Lias
of England (McGowan, 1996B), but the material, like The-
ODORl’s (1854), is too fragmentary for the erection of a new
taxon. If more material of the English and German giant
ichthyosaurs were found, and shown to be conspecific,
I. ingens would be an appropriate available name.
Ichthyosaurus integer Bronn, 1844
Bronn gave a brief description of a complete skeleton
which appears to have been lost or destroyed (McGowan,
1979B: 132). A more complete description was given by
Fraas (1891: 52, pi. 7) who figured a specimen (SMNS
4692) that Maisch (1998A) believed was conspecific with
Bronn’s (1844) lost holotype. (Maisch [1998A: 65] incorrectly
cited the specimen number as SMNS 4629.) Like
Suevoleviathan disinteger, the forefins of SMNS 4692 have
splayed digits, suggesting that Leptopterygius disinteger
Huene, 1926 is a subjective junior synonym for I. integer
Bronn, 1844. But there are some differences between the
two, and neither M cGowan (1979B) nor Maisch (1998A)
synonymized the two species.
Ichthyosaurus longimanus Owen, 1884
This species was erected upon a large isolated forefin,
presumably from the Lower Lias of Lyme Regis, England,
though no locality was mentioned. Owen (1884: 176-177
and pi. 3 0 , fig. 2) was impressed by the large digital count
(9) and by the large number of elements in each one (upward
of 39). Ichthyosaurus breviceps has a similar forefin, but
does not approach the large size of Owen’s (1884: pi. 30,
fig. 2) specimen. In the absence of more complete material,
its affinities remain in doubt.
Ichthyosaurus macrophthalamus Theodori, 1854
Theodori (1854: 64, pi. 4, fig. 2) erected this species on a
partial skull that was missing the snout, a series of articulated
vertebrae, parts of two humeri, several fin elements,
ribs and girdle elements, from the Upper Lias of Banz,
Germany. His diagnostic features included the large size of
the orbits, the small size of the temporal vacuities, and the
absence of notching in the forefin. H uene (1922) concluded
that the specimen was referable to Eurhinosaurus longiros-
tris, and included I. macrophthalamus in the synonymy of
that species. The diagnostic features enumerated by Theodori
(1854) are certainly consistent with E. longirostris, but
this cannot be confirmed with certainty because the snout
is missing. The holotype may have been lost. If it were
located and shown, beyond any doubt, to be a euxhinosaur,
I. macrophthalamus would be the first available species
name for Eurhinosaurus.
Ichthyosaurus microdon W agner, 1852A
W agner (1852A: 509-516) described three skeletons from
the Upper Lias of Holzmaden and Ohmden, Germany, and
tried to compare them with Owen’s (1840) I. acutirostris,
and with I. tenuirostris. He had some difficulties in distinguishing
between the latter species, noting that his correspondence
with Owen was of little avail in this regard. In
comparing the few characteristics of I. acutirostris supplied
by Owen, he concluded that his three specimens did not
correspond. Recognizing that more work was needed, he
concluded that he should name his material Ichthyosaurus
acutirostris var microdon, reserving the right to elevate it to
I. microdon when an “independent classification” should be
made. W agner (1852A) gave few distinguishing features,
but emphasized the small size of the teeth in two of the
specimens. The forefins were said to be wider distally than
in I tenuirostris, and at least three of the leading-edge
elements, including the radius, were notched. In the absence
of figures of his material, or the identification of the
material (which may have been lost during World War II),
it is impossible to establish its affinities. It is possible that
the three skeletons did not all belong to the same species.
The specimens with small teeth might have been referable
to Stenopterygius quadriscissus.
Isfjordosaurus minor (WlMAN, 1910)
This species based on a single humerus from the Lower
Saurian Niveau of the upper Sticky Keep Formation (Lower
Triassic: Olenekian) of Spitsbergen. The species can be
diagnosed based on the following features: Humerus wider
proximally than distally; humeral anterior flange thick
and confluent with humeral shaft, without inflection point
in cross-section; ulnar facet o f humerus as wide as radial facet;
humerus much longer than wide. WlMAN (1910: 143) erected
the species within the genus Pessopteryx, which clearly
belongs to a different grade of ichthyosaur. Motani (1999B),
with much hesitation, erected a new genus Isfjordsaurus for
its reception, solely to retain the erected species. The species
is considered valid, but tentatively listed as species
inquirenda because only the humerus is known.
Maisch & Matzke (2000B) argued that the holotypic
humerus may represent a hupehsuchian. However, it is
very unlikely for the following reasons. First, the suspected
presence of the anterior flange of the humerus in Hupeh-
suchus is very questionable. Based on a close observation of
the holotype of Hupehsuchus nanchangensis (IVPP 3232),
RM concluded that the element in question is more likely
a part of the scapulocoracoid complex: It is in the position
of the complex, shaped like the complex, and does not
resemble the right humerus, which has distinctive articular
facets for the ulna and radius. Second, hupehsuchians
are only known from the Middle Triassic of China, and
their occurrence in the Lower Triassic of Spitsbergen is
questionable. Maisch & Matzke (2000B) acknowledged
the limited value of their inference, and it is difficult to
understand why they explicitly removed Isfjordosaurus
from the Ichthyopterygia.
Leptopterygius nuertingensis H uene, 1931B
The holotype is a partied skull (SMNS 13488), some vertebrae,
ribs, and a coracoid, from the Lower Lias (Lower
Jurassic: lower Pliensbachian) of Nürtingen, Germany.
Huene (1931B) described the specimen in some detail, but
reported only minor differences from other species. Thus
the dentary was said to be a little longer and stronger than
in S. acutirostris, and stronger than in I. trigonodon. The
external naris was described as longer and more pointed,
and the teeth weaker. These minor differences, and the
incompleteness of the holotype, make its taxonomic position
uncertain. As discussed earlier, M aisch & Hunger-
BÜHLER (1997)’ referred this species to Temnodontosaurus.
Mikadocephalus gracilirostris Maisch et Matzke, 1997A
Mikadocephalus gracilirostris Maisch et Matzke, 1997A: 268
Holotype: GPIT 1793/1, a disarticulated skull.
Diagnosis: Quadrate with triangular projection mediov-
entrally; maxillary dental groove only present posteriorly.
Occurrence: Monte San Giorgio, Tessin, Switzerland.
Stratigraphic range: Grenzbitumen horizon; Middle Triassic
(Anisian-Ladinian boundary).
Remarks: Four new genera, all monotypic, have been described
during the past five years from the Grenzbitumen
horizon (Anisian-Ladinian boundary) on the border between
Italy and Switzerland. Two of them, Mikadocephalus
and Wimanius, are each known only from an incomplete
skull whereas the others, Besanosaürus and Sangiorgiosau-
rus [here considered a subjective junior synonym of Mixo-
saurus], are known from nearly complete skeletons. Cym-
bospondylus (Sander, 1989) and a Pessosaurus-like ichthyosaur
(see the section for Pessosaurus polaris) are also known
from the Grenzbitumen horizon, so the maximum of five
genera of medium-sized to large ichthyosaurs, each represented
by only a single species, may be recognized in this
horizon, if all of these genera are indeed valid. This species
genus ratio possibly reflects taxonomic bias. For the
interest of nomenclatural stability, it is best to preserve
older and widely recognized names when applicable.
Cymbospondylus Leidy, 1868 and Pessosaurus Wiman, 191(|
are preferred over the recently proposed names for this
reason. Judging from the literature, it is possible that the
names Mikadocephalus, and possibly Wimanius, may be
subjective junior synonyms of Pessosaurus. These names
are tentatively retained here because RM has not examined
the specimens. See also Pessopteryx.
Mixosaurus guanlingensis Cao in Yin et al., 2000
Mixosaurus guanlingensis Cao in Yin et al., 2000: 12
Holotype: GMR 006, a nearly complete skeleton with
damaged-skull and incomplete forefin.
Diagnosis: To be clarified.
Occurrence: Xiang Maoao, Xinpu, Guanling, Guizhou,
China
Stratigraphic range: Wayao Formation; Upper Triassic
(lower Camian).
Remarks: The generic assignment of M. guanlingensis to
Mixosaurus is not well established. Yin et al. (2000: 12)
stated that there were similarities between M. guanlingensis
and M. cornalianus plus M. maotaiensis, but the only feature
they named was the presence of biconcave vertebrae,
which is an ichthyopterygian plesiomorphy. The published
photograph (Yin et al., 2000: pi. 4, fig. 4) suggests
that there is no increase of the vertebral size toward the
mid-caudal region (characteristic of Mixosaurus). Also, the
published presacral count of about 45 (Yin et al., 2000:12)
seems to be too low for Mixosaurus, but is similar to Qian-
ichthyosaurus, which is reported from the same locality. It is
possible that M. guanlingensis is more closely related to
Q. zhoui than to M. cornalianus. However, these two do not
appear to be synonymous because M. guanlingensis is reportedly
pentadactyl whereas Q. zhoui is tetradactyl. These
ichthyosaurs seem to share some characters with Mixosaurus
and Toretocnemus, and probably belong to the stem
group leading to parvipelvians.
Ophthalmosaurus saveljeviensis Arkhangelsky, 1997
Paraophthalmosaurus saveljeviensis Arkhangelsky, 1997: 87
Paraophthalmosaurus saratoviensis Arkhangelsky, 1998A: 88
Holotype: SUU 104a-23, a partial, much broken up skull,
with most of the rostrum missing, some anterior vertebrae,
ribs, a partial pectoral girdle, a humerus and a few other
forefin elements.
Diagnosis: Humerus with three distal facets, the smallest
articulating with a preaxial accessory element; facet for
ulna smaller than radial facet. Coracoid with oblique posterior
margin. Orbit large; teeth weakly attached. Femur
with three distal facets.
Occurrence: Near Gomyi, Saratov Region, Russia.
Stratigraphic range: Upper Jurassic (lower Volgian [Ti-
thonian]).
Remarks: The features that distinguish Paraophthalmosaurus
saratoviensis from the holotype of P. saveljeviensis are
marginal and can be attributed to individual variation.
Further work on this species is needed to establish its
affinities. It might prove to be identical with Ophthalmosaurus
icenicus.