87. Ischium, styloid or plate-like - (0) plate-like (Fig. 5F-K); (1)
styloid (Fig. 5E, L-N). This character is independent of character
83.
88. Tibia and fibula - (0) in contact or closely placed with each
other; (1) widely separated from each other.
89. Pedal digit I - (0) present; (1) absent.
90. Tibia L/W ratio - (0) longer than wide; (1) wider than long.
91. Tibia contiguous ‘shaft’ - (0) complete or nearly complete; (1)
absent.
92. Tibia peripheral ‘shaft’ - (0) complete or nearly complete; (1)
notch or largely reduced; (2) absent.
93. Fibula posterior extent - (0) not fixed, fibula being mobile
relative to femur; (1) much posterior to femur; (2) about the
same level as femur.
94. Atlantal pleurocentrum - (0) separate from axis; (1) fused
with axis.
95. Presacral count - (0) 30 or less; (1) between 40 and 50; (2) 55
or more. Cymbospondylus buchseri was coded as 2 (see Systematic
Paleontology for explanation). [C a llaw a y , 1989: character
13]
96. Caudal peak - (0) absent; (1) present. The term caudal peak
refers to the curvature of the vertebral column in the middle
of the tail, forming a peak. This structure corresponds to the
tailbend in euichthyosaurs.
97. Posterior dorsal centra shape - (0) cylindrical; (1) discoidal.
[C allaw a y , 1989: charl9]
98. Mid-caudal centra height change - (0) gradual decrease; (1)
increase; (2) sudden decrease. The sudden decrease seems to
be correlated to the formation of hypocercal caudal fin.
99. Cervical bicipital rib facet - (0) absent; (1) present. [C a llaw a y ,
1989: character 14]
100. Posterior-dorsal bicipital rib facet - (0) absent; (1) present, at
least near pelvic girdle. [C allaw a y , 1989: character 14]
101. Anterodorsal rib facets - (0) confluent with anterior facet in
at least some centra; (1) not confluent in any of the centra.
102. Anterior dorsal neural spine - (0) normal; (1): narrow, high,
and straight. Anterior dorsal neural spines of most ichthyosaurs
are similarly shaped, although there are some variations.
Mixosaurus differs from others in having narrow, high
neural spine that are almost perpendicular to the vertebral
column. [C allaw a y , 1989: character 16]
103. Neural spine anticlination in tail - (0) absent; (1) present.
104. Sacral ribs - (0) two, distinguishable; (1) not distinguishable.
105. Posterior gastralia (triradiate or v-shaped) - (0) present; (1)
absent.
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