APPENDIX S3
Wherever, the character states differ from that of the earlier authors, or a new character has been
introduced, a brief explanation follows the character codes. Characters not applicable to certain
taxa were denoted as ‘–’ while missing/ unknown characters were denoted as ‘?’ in the data
matrix.
Cranial characters (31)
1. Maximum skull width (SW) relative to the skull length along midline (SL). SL ≥ SW (0),
SL < SW (1) [modified from Benton 1983; Dilkes 1998; Langer and Schultz 2000a;
Montefeltro et al. 2010]
In Fodonyx, SL (c.140 mm) < SW (170 mm, after Langer et al. 2010); hence, contra
Montefeltro et al. (2010), the character coding for Fodonyx is taken as 1, whereas for
Bentonyx, the character coding is 0 as SL = c.140 mm and SW = 130 mm (after Langer et
al. 2010). For I. genovefae the coding is taken as ‘1’ from Montefeltro et al. (2010).
2. Skull height (SH) relative to skull length (SL). SH/SL = c.0.4 (0), SH/SL ≥ 0.5 (1) (current
study)
Most of the Middle Triassic rhynchosaurs have SH/SL = c.0.4, whereas the Upper
Triassic forms such as H. gordoni and H. huxleyi have SH/SL = c.0.6
3. External nares. Separate (0); single median naris (1) [Benton 1985; Hone and Benton
2008]
4. Premaxilla ventral margin. Horizontal/straight (0); down-turned/curved (1) [Benton
1985; Hone and Benton 2008]
1
5. Orbit orientation. Mostly lateral (0); dorsal (1) [Hone and Benton 2008]
6. Premaxilla and prefrontal contact. Absent (0); present (1) [Dilkes 1998; Hone and
Benton 2008]
7. Maxilla ventral margin. Horizontal (0); convex (1) [Hone and Benton 2008]
8. Jugal area in lateral view. Smaller than maxilla (0); larger than maxilla (1) [Benton
1983, 1985, 1990; Hone and Benton 2008]
Although Hone and Benton (2008) kept this character unknown (‘?’) for H. sp.
(Zimbabwe), Raath et al. (1992, p. 8, fig. 4a) shows that jugal area is greater than the
maxilla, and the character is coded as ‘1’ in the current study.
9. Jugal-lacrimal contact. Minimal (0); extensive (1) [Montefeltro et al. 2010]
10. Lateral surface of the jugal. Lacking ornamentation (0); anguli oris crest short and does
not reach jugal anterior process (1); reaches jugal anterior process (2) [modified from
Hone and Benton 2008; Montefeltro et al. 2010]
In contrast to the other Middle Triassic forms, Fodonyx possessed well developed anguli
oris crest similar to that seen in the Upper Triassic forms (Chatterjee 1974; Benton 1983;
Langer and Schultz 2000a) and is coded here as ‘2’.
11. Jugal surface dorsal to anguli oris crest. Lacking secondary anguli oris (0); with
secondary anguli oris (1) [Montefeltro et al. 2010]
Since anguli oris crest is absent, this character is coded as not applicable (-) in
Proterosuchus, Trilophosaurus, Mesosuchus, Howesia, R. articeps, R. brodiei and
Stenaulorhynchus. Ornamentation on the lateral surface of the jugal of H. tikiensis is
markedly different from that of Teyumbaita sulcognathus. In contrast to Teyumbaita
sulcognathus, which bears secondary anguli oris crest dorsal and oblique to the primary
2
one (Montefeltro et al. 2010, p. 34, fig. 4b), H. tikiensis bears a deep depression dorsal to
the primary anguli oris crest and a radiating ridge-depression complex towards the
posterodorsal end.
12. Jugal height/length ratio. < 0.5 (0); 0.5–0.7 (1); >0.7 (2) (current study)
It is seen that the jugal height (JH)/jugal length (JL) is less than 0.5 for the Middle
Triassic forms. The height increases significantly with the Upper Triassic forms, where
JH/JL = 0.5–0.7 is shown by Fodonyx, Teyumbaita, H. heunei, H. gordoni and H.
tikiensis. On the other hand, high jugal (JH/JL > 0.7) is noted in Bentonyx sidensis and H.
sp. (GSI).
13. Width of postorbital bar with respect to maximum orbital diameter. < 0.4 (0); > 0.4 (1)
[Langer and Schultz 2000a; Hone and Benton 2008]
Character state for I. genovefae is after Montefeltro et al. (2010), whereas that for
Fodonyx is unknown (Langer et al. 2010). The ratio has been estimated for Bentonyx
from Langer et al. (2010), p. 1886, fig. 2A.
14. Frontal. Longer than broad (0); broader than long (1) [Benton 1983; Hone and Benton
2008]
15. Dorsal longitudinal groove on frontal. Absent (0); deeper posteriorly (1); same depth
throughout its length (2) [Dilkes 1995, 1998; Langer and Schultz 2000a; Hone and
Benton 2008; Montefeltro et al. 2010]
Longitudinal grove on the frontal is absent in Proterosuchus (Cruickshank 1972, p. 95,
fig. 2a), and Trilophosaurus (Heckert et al. 2006, p. 632, fig. 6F). However, the groove is
present in all rhynchosaurs but may be distinguished based on the extent of its depth. For
Fodonyx, the character coding (‘0’) is after Montefeltro et al. (2010).
3
16. Relative midline lengths of frontal and parietal. Frontal longer (0); parietal longer (1)
[Benton 1983, 1990; Hone and Benton 2008; Montefeltro et al. 2010]
17. Postfrontal. Excluded from upper temporal fenestra border (0); forming the upper
temporal fenestra border (1) [Benton 1983, 1990; Hone and Benton 2008; Montefeltro et
al. 2010]
18. Parietal. Not expanded laterally at midlength (0); expanded laterally at midlength (1)
[Montefeltro et al. 2010]
19. Parietal. Separate (0); fused (1) [Benton 1990; Hone and Benton 2008]
20. Parietal foramen. Present (0); absent (1) [Dilkes 1998; Hone and Benton 2008]
21. Anterior process of quadratojugal. Present (0); absent (1) [Dilkes 1998; Hone and
Benton 2008]
22. Supratemporal. Present (0); absent (1) [Benton 1985; Hone and Benton 2008;
Montefeltro et al. 2010]
23. Shape of supraoccipital in occipital view. Plate-like (0); inverted cup-like (1) [Dilkes
1995, 1998; Hone and Benton 2008]
24. Basioccipital and basiphenoid length. Basiphenoid longer (0); basioccipital longer (1)
[Langer and Schultz 2000a; Hone and Benton 2008; Montefeltro et al. 2010].
25. Basipterygoid process dimensions (dorsoventral length, anteroposterior width). Longer
than wide (0); wider than long (1) [Benton 1983; Langer and Schultz 2000a; Hone and
Benton 2008; Montefeltro et al. 2010]
For the Middle Triassic forms, the basipterygoid process is longer than broad (0) whereas
in most of the Upper Triassic forms, the basipterygoid process is blunt and broader than
4
long (1). Exceptions are I. genovefae (Langer et al. 2000a) and H. tikiensis. In the latter
form, the length:width ratio is 1.3:1 (current study).
26. Orientation of basipterygoid process. Anterolateral (0); ventral (1); posterolateral (2);
posteroventral (3)[modified from Hone and Benton 2008]
27. Occipital condyle position. Anterior to cranio-mandibular articulation (0); aligned to
cranio-mandibular articulation (1) [Montefeltro et al. 2010]
28. Occipital condyle proportions. OcL/OcH > 1.5 (0); OcL/OcH = 1.50–1.3 (1); OcL/OcH
= 1.2 (2); OcL/OcH = 1 (3) [current study]
The occipital condyle of Mesosuchus is distinctly elliptical in shape (Dilkes 1998), where
the estimated occipital length (OcL)/occipital height (OcH) = 2. In contrast, the
proportions of the occipital condyles of other forms such as R. articeps, Bentonyx, H. sp.
(GSI), H. gordoni and Teyumbaita differs markedly and OcL/OcH ranges between 1.4–
1.3. The shape of occipital condyle in these forms is mostly oval though in case of
Teyumbaita, it is reniform in shape. In the Indian Upper Triassic forms (H. huxleyi and H.
tikiensis) the OcL/OcH = 1.2, whereas that for H. huenei is 1.1 and the condyle is
completely rounded.
29. Mandible depth. < 25% of the total length (0); > 25% of the total length (1) [Hone and
Benton 2008; Montefeltro et al. 2010]
30. Dentary length relative to the total mandibular length. ≤ 0.5 (0); > 0.5 (1) [modified from
Benton 1990; Dilkes 1995; Langer and Schultz 2000a; Hone and Benton 2008;
Montefeltro et al. 2010 ]
31. Jaw symphysis. Formed largely by dentary (0); splenial only (1) [Dilkes 1998; Hone and
Benton 2008]
5
Characters based on dentition (18)
32. Premaxillary teeth. Present (0); absent (1)[after Hone and Benton 2008]
33. Proportion of maxillary tooth plate. Width at posterior end(DBW)/Length (DBL) ≤ 0.2
(0); c.0.3 (1); 0.4(2); ≥ 0.5 (3)[current study]
The ratio for Proterosuchus is estimated to be 0.1 (Welman 1998). For Mesosuchus and
Howesia, DBW/DBL is calculated to be 0.2 (coded as ‘0’). It increases to 0.3 in the
Middle Triassic forms (1). The Upper Triassic forms such as Teyumbaita and all the
species of Hyperodapedon show DBW/DBL = 0.4 (coded as ‘2’), except for H. stockleyi
and Wyoming Hyperodapedon (0.6) and is coded here as ‘3’.
34. Number of tooth rows on maxilla. Single row (0); multiple rows (1) [Hone and Benton
2008]
35. Maxillary grooves. Absent (0); present (1) [current study]
36. Combination of maxillary groove and dentary blade. two grooves-two blades (0); two
grooves-one blade (1); one groove-one blade (2) [current study]
A combination of two longitudinal maxillary grooves and two dentary blades is found in
Stenaulorhynchus, Rhynchosaurus (R. articeps and R. brodiei), T. sulcognathus whereas
H. huenei is represented by a combination of two grooves and one dentary blade (Langer
and Schultz 2000a; Montefeltro et al. 2010). In all other species of Hyperodapedon, there
is one primary groove corresponding to a dentary blade. Exception is seen in H. huxleyi
(Chatterjee 1974), H. gordoni (Benton 1983) and H. tikiensis where few large individuals
exhibit two grooves and one dentary blade, which is considered in the present study as a
late ontogenetic feature.
6
37. Maxillary tooth-bearing area lateral to the main longitudinal groove (LDS) relative to
the medial dentigerous space (MDS). LDS/MDS < 1 (0); LDS/MDS = 1 (1); 1 <
LDS/MDS < 1.5 (2); LDS/MDS > 1.5 (3) (current study)
The Middle Triassic forms such as Rhynchosaurus articeps, Fodonyx, Mesodapedon, and
others have LDS/MDS = 0.9, except for R. brodiei (0.76) and Stenaulorhynchus (0.5).
The Upper Triassic forms such as H. gordoni (c.1), I. genovefae (1) and H. sp.
(Wyoming) (1) have equal LDS and MDS (coded as ‘1’) whereas the other Upper
Triassic forms have wider LDS in comparison to MDS. However, this ratio generally
ranges between 1.2–1.4 (coded as ‘2’), except for H. sp. (GSI), which has a high
LDS/MDS value of 1.8 (coded as ‘3’).
38. Maxillary cross-section lateral to main groove. Crest-shaped (0); cushion-shaped (1)
[Langer et al 2000a; Montefeltro et al. 2010]
Langer et al. (2000b) suggested that the maxillary cross section lateral to the primary
groove may be considered as crest shaped when LDS < MDS and LDS contains two or
fewer tooth rows. On the other hand, cushion-shape refers to a wider LDS with more than
two tooth rows. Although H. huenei has LDS/MDS = 0.8, LDS contains three tooth rows
and is considered as cushion shaped (Langer et al. 2000b). In the current study, I.
genovefae and Wyoming Hyperodapedon are considered as cushion shaped as LDS =
MDS, even though LDS contains 2 or fewer tooth rows. On the other hand, morphotype 1
of H. tikiensis shows more similarity with crest-like cross-section although LDS > MDS
and contains more than two tooth rows.
39. Number of tooth rows on LDS. 1 (0); ≥ 2 (1) (current study)
7
40. Medial maxillary groove. Present and reaching the anterior half of the maxilla (0);
present but not reaching the anterior half of the maxilla (1); absent (2), [modified from
Benton 1990; Dilkes 1995, 1998; Montefeltro et al. 2010]
In rhynchosaurs, double maxillary grooves correspond to two dentary blades (character
36 in the present study), except for H. huenei. In such forms primary lingual teeth is
present medial to the medial blade of the dentary (Langer et al. 2000a). In these forms,
the medial maxillary groove is continuous throughout the maxillary tooth plate (coded as
‘0’). In few of the Middle Triassic forms such as Stenaulorhynchus, the medial maxillary
groove becomes restricted to the posterior half of the maxilla (coded as ‘1’). In later
forms, there is loss of the medial blade along with the loss of primary lingual teeth of the
dentary and medial maxillary groove (coded as ‘2’).
41. Number of tooth rows on MDS (area medial to the primary longitudinal groove). ≤ Two
rows (0); three or more tooth rows (1)[modified after Montefeltro et al. 2010]
42. Maxillary lingual teeth. Absent (0); single (1); few and scattered (2); multiple rows of
teeth (3) [modified after Benton 1983; Dilkes 1998; Hone and Benton 2008; Montefeltro
et al. 2010 ]
43. Jaw occlusion. Single-sided overlap (0), flat occlusion (1), blade and groove (2) [Dilkes
1998; Hone and Benton 2008]
44. Angle formed by posterior edges of maxillary tooth-bearing area: 0º (0); 180º (1), 180º–
121º (2); 120º–91º (3); c.90º (4) (current study)
45. Shape of dentary teeth. Only conical (0); conical and laterally compressed (1); only
laterally compressed (2) [modified from Montefeltro et al. 2010]
8
46. Lingual dentary teeth. Absent (0); primary lingual dentary teeth present (1);loss of
primary lingual teeth and presence of lingual teeth (2); loss of lingual teeth (3) [modified
from Langer and Schultz 2000a; Langer et al. 2000a; Hone and Benton 2008;
Montefeltro et al. 2010]
Primary lingual teeth and lingual teeth of the dentary follow the definition given by
Langer et al. (2000a).
47. Vomerine teeth. Present (0); absent (1) ) [Dilkes 1998; Langer and Schultz 2000a;
Langer et al. 2000a; Hone and Benton 2008]
48. Palatine teeth. Present (0); absent (1) [Dilkes 1998; Hone and Benton 2008]
49. Pterygoid teeth. Present (0); absent (1) [Benton 1983; Dilkes 1998; Hone and Benton
2008]
Postcranial characters (27)
50. Three bulbous processes or convexities on the anterior surface of the axial centrum.
Absent (0); present (1) [current study]
These three processes or convexities are absent in all hyperodapedontines including T.
sulcognathus (Montefeltro et al. 2013) but are present in H. tikiensis and H. gordoni
(Benton 1983, p. 653, figs 19e–f).
51. Axial ventral keel. Present (0); absent (1) [after Montefeltro et al. 2013]
52. Axial parapophysis. Present (0); absent (1) [after Montefeltro et al. 2013]
53. Postaxial intercentrum. Present (0); absent (1) [Langer and Schultz 2000a; Hone and
Benton 2008]
9
54. Neural arches of mid-dorsal vertebrae. Deeply excavated (0); shallowly excavated (1)
[Hone and Benton 2008]
In the case of H. tikiensis, the angle formed by the diapophyseal dorsal edge with the
horizontal plane is used as a parameter to assess the concavity of the excavation. It is
found that the angle varies between 8º–45º from the dorsal vertebrae 3–8, and is
considered here as deeply excavated (0).
55. Scapulocoracoid. Fused (0); discrete or separate (1) [current study].
56. Orientation of the scapula. Lateral (0); nearly vertical (1) [current study]
In Mesosuchus the scapula is laterally oriented where it makes an angle of about 45º with
the vertical axis. The orientation of the scapula of Mesosuchus is very similar to that of
Proterosuchus (Dilkes 1998). The available scapula of other rhynchosaurs attained near
vertical orientation (angle with vertical axis ≤ 30º)
57. Ratio between length and maximum width of the scapular blade. ScL/ScW-L > 2 (0);
ScL/ScW-L ≤ 2 (1) (current study)
In the Early Triassic form, Mesosuchus the scapula is slender and long (ScL/ScW-L =
2.2) which contrasts with that of the other taxa such as R. articeps (1.9), H. tikiensis (2)
and H. sp. (GSI, 2). H. huxleyi and F. spenceri has relatively robust scapula as suggested
by the low ScL/ScW-L (c.1.3)
58. Coracoid foramen. Absent (0); restricted to coracoid (1); shared between scapula and
coracoid (2) [modified from Langer and Schultz 2000a; Hone and Benton 2008]
Coracoid foramen is absent in Mesosuchus (Dilkes 1998) but is present in all other
rhynchosaurs.
10
59. Posterior process of interclavicle. Uniform expansion (0); distally expanded (1) [Dilkes
1998; Hone and Benton 2008]
60. Posterior process of the coracoid. Present (0); absent (1) [Benton 1985, 1990; Dilkes
1998; Langer and Schultz 2000a; Hone and Benton 2008; Montefeltro et al. 2010]
61. Length of deltopectoral crest (dpcL): dpcL < 20 per cent of humeral length (0); dpcL =
20–29 per cent of HL (1); dpcL ≥ 30 per cent of HL (2) (current study)
The extent of the deltopectoral crest, which was the site of insertion of the glenoid
rotating muscles such as M. pectoralis and M. deltoideus, varies in the rhynchosaurs. In
R. brodiei and F. spenceri, it comprises less than 20 per cent of HL (coded as 0).
Wherever humerus is not known, this character is coded as ‘?’. In all other forms, except
for H. huxleyi, H. tikiensis and H. sp. (GSI), the deltopectoral crest ranges from 20–30
per cent of HL. In H. huxleyi, H. tikiensis and H. sp. (GSI), the deltopectoral crest is
particularly robust and massive, and constitutes about 35–36 per cent of HL.
62. Angle of deltopectoral crest with respect to the humeral longitudinal axis: < 10º (0); 10º–
30º (1); > 30º (2) (current study)
In comparison to the Early Triassic rhynchosaurs, the later forms show a distinct flaring
of the deltopectoral crest. Hence the angle of the deltopectoral crest with respect to the
longitudinal axis of the humerus is less than 10º in R. articeps (coded as ‘0’), 10º–30º in
F. spenceri and H. huxleyi (coded as ‘1’) and > 30º in H. gordoni, H. tikiensis and H. sp.
(GSI). The latter character state is coded as ‘2’. It may be noted that the dpc of H. sp.
(GSI) is much more flaring when compared with the others and the angle is about 58º
with respect to the humeral longitudinal axis.
11
63. Supinator process of the humerus. Absent (0); hook-shaped (1); formed by a supinator
ridge and ectepicondyle groove (2) [modified from Montefeltro et al. 2013]
Hook-shaped supinator process is a characteristic feature of Middle Triassic
Stenaulorhynchus and Upper Triassic Otischalkia (Hunt and Lucas 1991). However, this
feature is absent in the humeri of all other rhynchosaurs. In the hyperodapedontines,
including H. tikiensis, the humerus is characterized by a distinct supinator ridge and an
ectepicondylar groove.
64. Ratio between humeral (HL) and radial length (RL):HL/RL < 1.5 (0); HL/RL ≥ 1.5 (1)
(current study)
65. Ratio between humeral (HL) and femoral (FL) lengths: HL/FL < 1 (0); HL/FL ≥ 1 (1)
[modified from Benton 1983; Langer and Schultz 2000a; Hone and Benton 2008]
66. Relative proportions of preacetabular (IA) and postacetabular iliac length (IP). IP > IA
(0); IP ≤ IA (1) [modified from Benton 1983; Langer and Schultz 2000a; Hone and
Benton 2008]
67. Ratio between iliac length (IL) and height (IH): IL/IH < 1 (0); IL/IH = 1 (1); IL/IH > 1
(2) [current study]
68. Relative proportions of femur: distal width/total length < 0.3 (0), ≥ 0.3 (1) [Benton 1983,
1990; Hone and Benton 2008]
69. Ratio between femoral length (FL) and midshaft width (FMWL): FL/FMWL ≥ 9 (0);
FL/FMWL = 9–7 (1); FL/ FMWL < 7 (2) (current study)
In Proterosuchus, the ratio is estimated to be 8.1 whereas that for Mesosuchus and
Otischalkia, it is found to be ≥ 9 (Cruickshank 1972; Hunt and Lucas 1991; Dilkes 1998).
12
For Howesia and Stenaulorhynchus, it ranges between 9 and 7 and in the Upper Triassic
forms, the ratio decreases and is < 7.
70. Internal trochanter. Continuous to the femoral head (0); separated from femoral head (1)
[Montefeltro et al. 2010]
71. Ridge along tibial midshaft. Absent (0); present (1) [current study]
72. Relative size of astragalar articular facets. Tibial facet greater than centrale facet (0);
centrale facet greater than tibial facet (1) [Langer and Schultz 2000a; Hone and Benton
2008; Montefeltro et al. 2010]
73. Size of fourth distal tarsal relative to other distal tarsals. Twice as long (0); same size (1)
[Langer and Schultz 2000a; Hone and Benton 2008]
74. Metatarsal I. Longer than broad (0); broader than long (1) [Montefeltro et al. 2010]
75. Ratio of lengths of metatarsals I and IV. 0.4–0.3 (0); < 0.3 (1) [modified from Dilkes
1998; Hone and Benton 2008]
13