Genus Blezingeria Huene, 1951B
Blezingeria was erected by Huene (1951B) upon postcranial
material, mainly vertebrae, which were assigned to Notho-
saurus ichthyospondylus Fraas, from the upper Muschelkalk
of Crailsheim, Württemberg, Germany. The species was
considered an ichthyosaur on the basis of its discoidal
vertebral centra, but this feature also occurs in diverse
aquatic amniotes (Motani, 2000A). Other features, such as
the presence of diapophyses on the neural spine, argue
against ichthyosaurian affinities. Callaway & Massare
(1989B), based on examination of the original material,
concluded that it was not ichthyosaurian, and this position
is supported here. Schoch & W ild (1999) considered Blezingeria
ichthyospondyla a thalattosaur.
Ichthyosaurus gaudensis H ulke, 1871B
Hulke (1871B: 29, fig. 1) based this species on an isolated
tooth from Gozo, an island next to Malta, supposedly from
the Miocene. The tooth is not ichthyosaurian and probably
crocodylian.
Ichthyosaurus inexpectatus Rusconi, 1948
This species was founded upon part of a mandible, apparently
from the Upper Jurassic near Malargüe, Mendoza,
Argentina, which is obviously plesiosaurian (Rusconi,
1948: 151, fig. 81).
Ichthyosaurus missouriensis H arlan, 1834
This species was erected upon the tip of the rostrum of a
mosasaur.
Myopterygius (?) ezoensis Shikama, 1963
This species, based on four vertebrae from the Cretaceous
of Japan, is probably plesiosaurian.
Rachitrema pellati Sauvage, 1883
Sauvage (1883: 5; pi. 6, fig. 4; pi. 7, figs 2 -5 ; pi. 9, figs 5-6)
reported a new reptile from the Rhaetian of France that
was clearly not ichthyosaurian and is probably dinosaurian.
Regardless of this, Kuhn (1934: 64) synonymized R.
pellati with Ichthyosaurus carinatus Sauvage, 1876, which is
inappropriate.
Saurocephalus lanciformis H arlan, 1824A
Harlan (1824A: 337, pi. 12, figs. 1-5) erected a new genus
and species for a fossil, from an unknown horizon, that
had been collected by L ewis and Clark during their explorations
up the Missouri River in 1804. H arlan (1824A)
compared it to “the new fossil genus ‘Ichthyosaurus’ ...
uniting in its structure both the fish and the lizard ... ”,
concluding “it approaches very nearly the Ichthyosaurus,
but is separated from this genus . . . ” The specimen, with its
deep jaw and lanceolate teeth, is clearly not ichthyosaurian,
and has since been identified as a teleost (e.g., Carroll,
1987: 604L). '
Sphaerodontes caroli Torre e t Cuervo, 1939
Included under the heading “ICHTHYOPTERYGIA” was
a new genus and species, which was figured in a rather
poor photograph (Torre & Cuervo, 1939: 5). The (unnumbered)
illustration depicts what appears to be an angular
nodule, with a large piece plucked out, giving the appearance
of an orbit. This Jurassic specimen from Cuba may be
a fossil, but it bears little resemblance to an ichthyosaur.
Tholodus minutus Schmid, 1861
According to P eyer (1939), Schmid (1861) based this new
species of Tholodus on dental material from the German
Muschelkalk, which later was reidentified as belonging to
the holostean fish Colobodus.
Xinpusaurus sunt Y in in Y in e t al., 2000
Xinpusaurus was founded upon specimens from the Upper
Triassic (lower Camian) of Guizhou Province, China (Yin
et al., 2000). Judging from the published photographs, it
seems unlikely that this genus belongs to the Ichthyoptery-
gia. It is most likely a thalattosaur, but further studies are
necessary to establish its affinities.
Phytogeny and higher taxonomy
Outgroup
One of the major questions in the ichthyopterygian sys-
tematics is their relationship with other amniotes. There is
a growing consensus that ichthyosaurs are nested within
Diapsida (Callaway, 1989; Massare & Callaway, 1990;
Caldwell, 1996; Motani et al., 1998; Motani, 2000A), but
even this view is not without opposition (e.g., M aisch,
1997) . Most of the recent studies place ichthyosaurs near
the basal node of Sauria sensu Gauthier, whether it is
inside (e.g., Caldwell, 1996) or outside this clade (e.g.,
Massare & Callaway, 1990; Motani et al., 1998). This area
of diapsid phylogeny is still controversial (e.g., Dilkes,
1998) , and extensive studies, not only of basal ichthyosaurs
but also of basal diapsids, are necessary before a general
consensus can be achieved regarding the position of ichthyosaurs
in the diapsid phylogeny.
Historically, almost all major groups of vertebrates
have been suggested as a possible sister group of ichthyosaurs.
Callaway (1989) and Massare & Callaway (1990)
gave brief summaries of these ideas, which are incorporated
in Table 4. This list is probably not exhaustive.
Ingroup Relationships
Phylogenetic studies of ichthyosaurs have been closely
tied to the history of fossil discovery. The first scientific
description of ichthyosaurs (Home, 1814) was based on
material from the Jurassic, which subsequently yielded a
wealth of well-preserved specimens. This early discovery
of high-quality materials initiated the “Jurassicocentric”
view of ichthyopterygian evolution, which persists until
today. In such a view, the evolution of ichthyosaurs is
traced from the reverse direction, i.e., from the Jurassic to
Triassic (“top-down”). A typical example of the Jurassicocentric
view is the latipinnate-longipinnate hypothesis, a
dogma that dominated the study of ichthyopterygian interrelationships
during the twentieth century. This hypothesis
originated from Kiprijanoff’s (1881) study, in which
he proposed a dichotomous division of Jurassic ichthyosaurs
into longipirinipedines, subsequently renamed lon-
gipinnates by L ydekker (1889A), and latipinnipedines (later
renamed latipinnates), based on the forefin structure.
Longipinnate ichthyosaurs are those with three or four
primary digits (i.e., digits that contact the distal carpals), as
in Stenopterygius, whereas those with more than four primary
digits were considered latipinnates, Ichthyosaurus
being the typical form. This dichotomy was extended to
include Triassic forms by Huene (1922), who became the
major promoter of the Jurassicocentric view from then on.
H uene (1922) considered Mixosaurus a latipinnate ichthyosaur
because it had a pentadactyl forefin, whereas the
other Triassic forms were mostly considered longipinnate,
despite the fact that there were no articulated forefins to
establish the number of primary digits. This dichotomous
classification prevailed until McGowan (1976) first questioned
its validity, and it still reappears occasionally in the
literature. M otani (1999A) recently showed that the typical
latipinnate forefin of Ichthyosaurus evolved from the tetra-
dactyl forefins of basal parvipelvians (i.e., longipinnate
fin), and was therefore not homologous with the “latipinnate”
forefin of Mixosaurus.
Not all paleontologists shared the Jurassicocentric
view. From time to time, discoveries of well-preserved
Triassic specimens led to reappraisals of the ichthyosaurian
evolution from Triassic to Jurassic forms. However,
such bottom-up views never became dominant because of
the rarity of Triassic specimens. The first articulated specimens
of Triassic ichthyosaurs were five skeletons of Mixosaurus
cornalianus reported by BASSAM (1886) from the
Italian Alps, and later figured by Repossi (1902), Baur
(1887A, 1887B) recognized Mixosaurus as being plesiomor-
phic, and thus interpreted the evolutionary sequence of
ichthyosaurian forefin structure in the correct evolutionary
sequence. Later discoveries of Triassic ichthyosaurs from
North America (e.g., Merriam, 1908) and from Spitsbergen
(e.g., Wiman, 1910) also stimulated appropriate recognition
of evolutionary sequences in ichthyosaurs. For example,
Merriam (1908) presented his view of ichthyosaurian
Table 4. List of animals that have been suggested as a possible
sister-group of ichthyosaurs.
“Fish” Home (1814,1816)
Salamander Home (1819B)
Embolomeres Huene (1937)
Synapsids
Ophiacodon Romer (1948)
Platypus Home (1818)
Delphinus Young (1821)
Sauropsids
Mesosaurus Huene (1922)
‘Eosuchians’ Tarshand (1983)
Turtles Appleby (1959)
Placodonts Mazin (1982)
Sphenodontiaris Baur (1887A,B)
Squamates Williston (1917), Tarsitano (1982)
Protorosauria Wiluston (1925)
Phytosaurs McGregor (1906)
Crocodylian Hawker (1807)
Aquatic birds Home (1818)