that the facet faced anteriorly in life: (1) it is difficult for the
fibula to articulate with this facet because it is parallel to
the shaft; (2) the other two facets seem to match the proximal
ends of the tibia and fibula well; (3) it is typical for
non-parvipelvian ichthyopterygian femora to have an anterior
facet next to tibial facet, although it is usually smaller.
Some parvipelvian humeri, especially those of Lepton-
ectes tenuirostris, are also known to have a similar paraxial
facet anteriorly. The femur of Besanosaurus leptorhynchus is
also distinctive in having an expanded proximal end seen
in lateral view (Dal Sasso & Pinna, 1996: fig. 17D). This
feature seems to be age-related in Spitsbergen forms: the
largest femur has a swollen proximal end as in B. leptorhynchus
(Wiman, 1910: pi. 9, fig. 1), but such a proximal expansion
is not remarkable in the two smaller femora (Wiman,
1910: pi. 1, figs. 2, 3). A femur figured by Wiman (1910: pi.
10, fig. 7) may appear slightly different from typical Besa-
nosaurus-type femora, but it probably represents an immature
Besanosaurus: it is smaller than the others, and has a
small third facet parallel to the shaft. Another femur
(Wiman, 1910: 9, fig. 4) is obviously eroded, and cannot be
identified with confidence.
Two humeri (Wiman, 1910: pi. 8, figs. 1, 2), resembling
those of shastasaurines, do not exactly match the type
humerus of Besanosaurus leptorhynchus. However, they
probably represent very mature humeri of this genus. They
differ from the only three-dimensionally prepared humerus
of Cymbospondylus (UCMP 9950), which lacks the dor-
sally inclined humeral head that is typical of Type 2 humeri
sensu Motani (1999A): such a head is clearly present in the
Spitsbergen form (Wiman, 1910: pi. 8, figs, la, 2a, 3a).
Isfjordosaurus, a non-ichthyosaurian ichthyopterygian,
is less abundant than Besanosaurus: only two femora (Wiman,
1910: pi. 10, figs. 4, 6) are probably referable to this
genus. The type humerus resembles that of Utatsusaurus
(Motani, 1999B), but is slightly more robust (L/W ratio of
1.3 versus 1.6 for Utatsusaurus). The referred femora are
comparable to, or slightly shorter than, the type humerus,
which accords with the humerus/femur ratio of non-ichthyosaurian
ichthyopterygians, such as Chaohusaurus and
Utatsusaurus. The femora are distally much wider than
proximally, and have very well defined articular facets for
the tibia and fibula, as in Utatsusaurus and Grippia, but
unlike in basal ichthyosaurians. However, the bones are
relatively more robust than those of the two genera. Neither
of the articular facets is perpendicular to the femoral
shaft, which is a feature lost in basal ichthyosaurians.
Apart from the above morphological differences, the elements
of Isfjordosaurus are much smaller than those of
Besanosaurus, at least by the factor of two in length.
See also Rotundopteryx hulkei in this section.
Pessopteryx pinguis W iman, 1910
W iman (1910) erected Pessopteryx pinguis upon a partial
bone identified by him as a humerus. This fragment, from
the upper Sticky Keep Formation (Lower Saurian Niveau;
Lower Triassic: Olenekian) of Spitsbergen, Svalbard, cannot
be identified as a humerus with confidence. Motani
(1999B) considered P. pinguis a nomen dubium, and this
designation is followed here.
Pessosaurus suevicus H uene, 1916
Huene (1916: 33) based Pessosaurus suevicus upon a vertebral
centrum, probably derived from the posterior dorsal
or anterior caudal region. The specimen occurred in the
lower Wellenkalk of the Black Forest, Württemberg, Germany
(lower Muschelkalk; Middle Triassic: Anisian). The
name is here considered a nomen dubium, following Callaway
& Massare (1989b) and Sander & Faber (1998).
Platypterygius bannovkensis Arkhangelsk^, 1998B
This species was erected upon a partial skull, comprising
little more than a rostrum, from the middle Cenomanian of
the Saratov Region of Russia. A number of features were
discussed, including the small foramen anterior to the
external naris, but this, like the others, is typical of the
genus.
Plutoniosaurus bedengensis E fimov, 1997
The material upon which this species was erected comprises
a partial skull, incomplete forefins, pectoral girdle, and
some ribs and vertebrae, from the Lower Cretaceous (upper
Hauterivian) of the Ul’yanovsk Region of Russia. Although
sufficiently determinate to be referred to the genus
Platypterygius, neither the material, nor its description, is
sufficient to permit specific identification.
Rotundopteryx hulkei Maisch et Matzke, 2000B
Rotundopteryx hulkei should be treated as an objective junior
synonym o f Pessopteryx nisseri for the reasons explained
below. As the latter is found non-diagnostic in the present
contribution, a lectotype to validate this view is not proposed
here. However, should the material be found diagnostic,
it is strongly recommended to consider what is
stated below and choose the lectotype from among the
postcranial elements in the syntype series of P. nisseri.
The ichthyosaurian genus Pessopteryx was named by
W iman (1910) for a collection of disarticulated bones from
the upper Sticky Keep Formation (Lower Saurian Niveau;
Lower Triassic: Olenekian) of Spitsbergen, Svalbard. W iman
(1910: 139) was aware that the material contained
jypically ichthyosaurian postcranial bones and somewhat
fishlike dental elements, containing bulbous tooth crowns
arranged in multiple rows, but the constant association of
the two led him to propose that they belonged together.
This mixed nature of the original material caused later
disputes regarding the taxonomic status of the genus.
Merriam (1911) first pointed out the possibility of two
entirely different reptiles being represented in the type
series, an ichthyosaur and an omphalosaur. Wiman (1916:
71), after seeing the description of additional dental material
of Omphalosaurus (Merrlam & Bryant, 1911), complied
with this by stating “I therefore consider the probability
larger that in addition to Pessopteryx nisseri also a representative
of the genus Omphalosaurus is before us.”
Subsequent authors almost unanimously ignored this
settlement: they accepted a priori that the entire material
represented a single species of ichthyosaur with a strange
dentition (e.g., Kuhn, 1934; Mazin, 1983C; Sander & Faber,
1998). Motani (1999B), following the consensus reached by
Merriam (1911) and Wiman (1916), suggested to limit the
name Pessopteryx nisseri to the ichthyosaurian material
contained in the type series while assigning the dental
material to an omphalosaur. Motani (2000B) provided further
evidence in support of this division by establishing
that Omphalosaurus was not an ichthyosaur, contrary to
general opinion. However, no explicit nomenclatural action
was taken.
Later the same year, Maisch & Matzke (2000B) suggested
a procedure opposite to the one given by Motani
(1999B). They accepted that the original type series contained
an ichthyosaur and an omphalosaur, but proposed
to limit the name P. nisseri to the omphalosaurian dentitions
therein, which would make Pessopteryx a subjective
junior synonym of Omphalosaurus. Furthermore, they proposed
a new name, Rotundopteryx hulkei, for the ichthyosaurian
half of the type series of P. nisseri. However, this
nomenclatural action is not in compliance with the ICZN.
Maisch & M atzke (2000B: 67) stated: “We regard ... the
jaw fragments specified and figured by Wiman (1910, p.
140, pi. 9, figs. 23-30) as the syntypic series of Pessopteryx
nisserf’, but it is not possible to limit the extent of a syntype
series unless the original author indicated his/her doubts
regarding the inclusion of certain specimens (ICZN Article
72.4). As demonstrated below, it is impossible to infer that
Wiman (1910) had any doubt regarding the postcranial;
material belonging to P. nisseri, although he possibly did
for the dental material. As a result of these recent developments,
now there are conflicting taxonomic designations
in the literature, neither of which is firmly established
according to the ICZN.
It is important to establish Wim an’s (1910) intention,
but his text does not clearly reveal whether the cranial or
postcranial elements were more important to him. However,
two facts remain. First, Pessopteryx was intended to be
an ichthyosaur from the beginning. Secondly, the animal
was named for its postcranial elements; the generic name
Pessopteryx referred to the fact that the round fin elements
looked like checker stones. It is thus clearly inappropriate
to limit the name Pessopteryx to the dental material representing
a non-ichthyosaur, when the name-deriving postcranial
material represents an ichthyosaur, as Wiman (1910)
obviously intended. Therefore, the lectotype of Pessopteryx
nisseri should be established for the postcranial material.
Statements by Wiman (1916), although made in a later
publication, further support this view and are worth mentioning.
The following quote strengthens the point that
postcranial elements of the type series were more important
to W iman (1910) than the dental material: “To Pessopteryx
nisseri I also referred, by way of proposal, and with
much hesitation, a large number of jaw fragments with
queer, button-like teeth in several rows” (Wiman, 1916:69).
Also, it is clear from the following quote that W iman considered
Pessopteryx an ichthyosaur: (after admitting that
the dental material belonged to an omphalosaur) “... I still
consider it probable that the majority belong to an ichthyosaurian
which I have called Pessopteryx nisseri” (Wiman,
1916: 69).
Maisch & Matzke (2000B: 67) rejected Motani’s (1999B)
proposal by stating “As, particularly since Mazin’s work,
it has been generally acknowledged that P. nisseri is an
omphalosaur, it appears to us of little use to refer to this
species, restricted to the postcranial material, as an ichthyosaur,
as done by Motani (1999b).” However, this argument
is invalid. The consensus among the workers represented
by Mazin (1982, 1983C) was that P. nisseri was an
ichthyosaur with a strange dentition, as originally intended
by W iman (1910) (Omphalosaurus and Grippia were both
considered omphalosaurids within ichthyosaurs). They
never suggested that P. nisseri was an omphalosaur (i.e.,
non-ichthyosaur; Maisch & Matzke, 2000B). Indeed, the
recognition that P. nisseri is an ichthyosaur has been the
only consensus reached among various authors since
Wiman (1910). Maisch & Matzke’s (2000B) proposal to
make P. nisseri non-ichthyosaurian is not plausible.
It is easy to propose the lectotype of Pessopteryx nisseri
herein to fix this point of view in the nomenclatural system.
Such an action is not taken here only because it is not
prudent to do so when the species is found to be based on
non-diagnostic material.
Shastasaurus careyi Merriam, 1902
This species was based on two fragmentary cervical or
anteriormost dorsal vertebrae from the Hosselkus Limestone
(Upper Triassic: upper Carnian) of Shasta Comity,
California. Motani (1999B) pointed out that the specimen
was more similar to Shonisaurus popularis than to Shastasaurus
pacificus, and designated it as Shonisaurus sp. The specimen
is too fragmentary to be of diagnostic value.
Shastasaurus carinthiacus Huene, 1925
H uene (1925) erected this species up o n v ertebrae and ribs,
which w ere considered non-diagnostic b y Motani (1999B).