V
Grippia
“Phalarodon”
[Omphalosaurus]
Mixosaurus
Utatsusaurus
‘Svalbardosaurus ’
Cymbospondylus
Toretocnemus
Californosaurus
Shastasaurus
Pessosaurus
Shonisaurus
Ichthyosaurus
Ophthalmosaurus
Stenopterygius
Temnodontosaurus
Eurhinosaurus
Suevoleviathan
Brachypterygius
Platypterygius
Grippidae
Mixosauridae
Utatsusauridae
Shastasauridae
Ichthyosauridae
Ophthalmosauridae
Temnodontosauridae
Thaisaurus
Utatsusaurus
Grippia
Chaohusaurus
Parvinatator
“Wimanius”
Mixosaurus
“Phalarodon”
“Contectopalatus”
Toretocnemus
Qianichthyosaurus
Cymbospondylus
Phantomosaurus
Besanosaurus
Shastasaurus
Shoniaurus
“Mikadocephalus”
Californosaurus
“Callawayia”
Macgowania
Hudsonelpidia
Temnodontosaurus
Leptonectes
Eurhinosaurus
Suevoleviathan
Ichthyosaurus
Stenopterygius
Aegirosaurus
Brachypterygius
Platypterygius
Ophthalmosaurus
Caypullisaurüs
Other post-Triassic
ichthyosaurs
Ichthyosaurus
Stenopterygius
Ophthalmosaurus
Other ichthyosaurs
Utatsusaurus
Grippia
[Omphalosaurus]
Mixosaurus
“Phalarodon”
Fig. 100. Phylogenetic hypotheses of the interrelationships of ichthyosaurs. A, M a z in (1982); B, K erton (1983); C , Go d efro it
(1993B); D , M a is c h & M a t zk e (2000); E , N ic h o lls et al. (1999); F, Sa n d e r (2000); G , C a llaw a y (1989); H , D a l Sasso & Pin n a (1996);
I, M a is c h & M a t zk e (1997A); J, M a is c h (1998A).
evolution, considering both the geography and time sequence.
However, such bottom-up views of ichthyosauri-
an evolution soon disappeared from the literature, as Mer-
riam moved from being a faculty member at the University
of California at Berkeley to the presidency of the Carnegie
Institution in Washington. Meanwhile, H uene (e.g., 1951B,
1956) continued to publish on his top-down view of ich-
thyopterygian evolution. Wim an’s (1929) discovery of the
first Early Triassic ichthyosaur Grippia longirostris came too
late to stop this trend: H uene (1930) merely considered
G. longirostris closely related to Mixosaurus (top-down
framework again).
Grippia
Utatsusaurus
Mixosaurus
“Phalarodon”
Shonisaurus
Besanosaurus
Cymbospondylus
Temno.platyodon
Tern no. burgundiae
Suevoleviathan
Platypterygius
Eurhinosaurus
Ichthyosaurus
Leptonectes
Stenopterygius
Ophthalmosaurus
Grippia
Cymbospondylus
Shonisaurus
Himalayasaurus
Besanosaurus
Toretocnemus
Californosaurus
Shastasaurus
Pessosaurus
Mixosaurus
Cymbospondylus
Mikadocephalus
Temnodontosaurus
Ichthyosaurus
Stenopterygius
Ophthalmosaurus
“Baptanodon”
Grippia
Cymbospondylus
Shonisaurus
Himalayasaurus
Toretocnemus
Californosaurus
Shastasaurus
Pessosaurus
Temnodontosaurus
Platypterygius
Suevoleviathan
Ichthyosaurus
Leptonectes
Eurhinosaurus
Stenopterygius
Ophthalmosaurus
Fig. 100. (continued).
In the middle of the twentieth century, studies of the
dentition gave rise to another misleading dogma in ich-
thyopterygian phylogeny: the hypothesis of the plesio-
morphic durophagy in ichthyosaurs. The usage of the
words “mixosaur” and “mixosaurid” at the time differed
from the present one; they usually referred to Triassic
ichthyosaurs in general, not only to Mixosaurus (e.g., Mer-
RIAM, 1908). “Mixosaurs” were distinguished from the typical
ichthyosaurs (i.e., post-Triassic forms) by the progressively
less derived appendicular skeletons and the presence
of heterodont dentitions, with conical anterior and
rounded posterior teeth. The heterodont dentitions were
only present in earlier members of “mixosaurs”, viz., Mixosaurus
(including Phalarodon), Tholodus, Grippia, and the
erroneously included Omphalosaurus. With the absence of
a counter example, the assumption that ichthyosaurs primitively
had a heterodont dentition seemed reasonable at
the time. Later discoveries, however, revealed the coexistence
of homodont and heterodont dentition in basal ich-
thyopterygians, and it is presently thought that heterodonty
evolved in ichthyopterygians at least twice.
About half a century after its discovery, Grippia longirostris
resurfaced as a pivotal taxon in the debate of ichthy-
opterygian phylogeny, when Mazin (1981A) reported additional
specimens of this stratigraphically oldest known
ichthyopterygian. This discovery was made at the time
when cladistic systematics was becoming dominant. Mazin
(1982) published the first cladogram for ichthyosaurs
by incorporating his new data on G. longirostris (Fig. 100A).
This work confirmed McGowan’s (1976) suspicion that the
longipinnate-latipinnate dichotomy did not exist. The
dogma of plesiomorphic durophagy was incorporated in
this cladogram as an a priori assumption, and thus was
never tested. Mazin’s (1982) cladogram was based on selected
characters that he found were taxonomically useful.
Similar approaches were taken by Kirton (1983), Godefroit
(1993B), and Nicholls et al. (1999), who presented
cladograms with selected characters plotted on nodes (Fig.
100B-C and E).
As computer programs for parsimony analysis became