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Journal of Paleontology 92(2):221–239
Table 1. Average and standard deviation of the measured dimensions of the Indian hybodonts examined. Taxa
N
Pristrisodus Morphotype I Morphotype II Morphotype III Morphotype IV Morphotype V P. tikiensis* L. duffini*
3 3 6
16 17 6 6
MDL
3.05±0.6 2.8±0.4 2.4±0.3 2.8±0.4 2.3±0.4 1.7±0.6 1.7±0.4
LLW
0.7±0.2 0.7±0.2
0.8±0.06 1.1±0.1 0.9±0.1 0.9±0.1 1±0.2
ABH
1.32±0.2 1.4±0.25 0.9±0.1 0.9±0.1 0.97±0.1 0.7±0.3 0.7±0.14
PCH
0.6±0.1 0.8±0.06 0.6±0.1 0.6±0.1 0.5±0.1 0.4±0.2 0.4±0.1
BL
1.9±0.8** 1.7±0.7
2.7±0.5 2.5±0.15 1.9±0.3 2.3±0.4 1.8±0.4
BW
0.5±0.1** 0.6±0.2
0.6±0.1 0.7±0.2 0.5±0.1 0.5±0.1 0.6±0.1
Index to measured parameters is given in Figure 2. Abbreviations: ABH, apicobasal height; BL, length in basal view; BW, maximum width in basal view; LLW, labiolingual width of hybodonts; MDL, mesiodistal length; N, number of specimens; PCH, height of principal cusp. Single (*) and double asterisks (**) indicate(s) after Prasad et al. (2008) and N = 3, respectively. All measurements are in mm.
Table 2. Characteristic features distinguishing the five morphotypes of Pristrisodus tikiensis (Prasad et al., 2008). Morphotypes
I N
MDL / ABH MDL / LLW BL / BW
Principal cusp Lateral cusplets Labial peg Lingual peg
Labial hor.r near crown-root junction Lingual hor.r high on the crown Other features
3
———high, pointed—— two
2.65 3.8 4.5
bifurcating cristae cristae present lingual foramen
triangular triangular straight straight
3
2.54 3.6
2.0
two/three triangular absent
II III 6
2.67 2.67 3.8
IV 22*
——————curved and crenulated——————— —curved and smooth—
three/four bilobed incipient
rounded small
curved and crenulated small cristae
———High, rounded——— four
2.67 2.55 4.6
V
23* 2.4 2.3 3.1
Low, rounded One
large, below crown-root junction absent absent
wide, crenulated triangular in shape
Index to the abbreviations is given in Table 1. Single (*) asterisk indicates that total number of specimens examined for the morphotypes IVandVincorporate specimens of Parvodus tikiensis and Lissodus duffini, respectively.
outline, concave towards the labial face and has multiple cir- cular pits or foramina (Fig. 3.4).
Morphotype II.—There are three isolated teeth which show overall similarity with morphotype I in terms of a pointed, robust principal cusp, but have three lateral cusplets on one side of the principal cusp and two on the other (Fig. 4.1). These teeth have crown proportions similar to morphotype I, where MDL/ LLW > MDL/ABH (Table 2). In most of the specimens, the height of the principal cusp is twice the height of the three lateral cusplets (e.g., IITKGPP11, Fig. 4.1, 4.2). A similar high prin- cipal cusp is also seen in IITKGPP20. Small vertical ridges (or cristae) extending along the crest are seen in the specimens (Fig. 4.1). The labial and lingual crests are sharp and prominent. The labial peg is large, triangular, and displaced towards the root, whereas on the lingual side, the peg is absent though the region has a prominent and large subcircular bulge (Fig. 4.1, 4.2). The ridge near the crown-root junction is curved and crenulated in labial view (Fig. 4.1), whereas it is smooth, curved, and situated midway on the crown in lingual view (Fig. 4.2). In occlusal view, the labial and lingual sides show a distinct difference in outline, especially at the labial and lingual pegs (Fig. 4.3). The root is partially preserved, showing an anaulacorhize vascularization pattern, and contains several large and irregular foramina. In basal view, the crown-base is dis- tinctly sub-triangular in outline (Fig. 4.4).
Morphotype III.—Morphotype III is based on six well- preserved teeth (Supplemental Data 1), where the crown pro- portions in longitudinal (MDL/ABH) and occlusal (MDL/LLW) views are equal, unlike that in the morphotypes I and II (Table 2). All the specimens of morphotype III (Supplemental
Data 1) are characterized by a bilobed labial peg, a slightly rounded principal cusp, and three or four pairs of lateral cusplets on either side of it (Fig. 5.1). Vertical ridges are present on the principal cusp and cusplets (Fig. 5.1). The curved ridges on the labial and lingual faces of the crown are similar to those seen in morphotype II. Although the lingual face is smooth, it contains an incipient lingual peg and a curved horizontal ridge. There is a foramen just below this lingual peg (Fig. 5.2). In occluso-lingual view, the crest is prominent (Fig. 5.3). The tooth has a centrally depressed base, which has a triangular outline that is slightly concave towards the lingual side (Fig. 5.4).
Morphotype IV.—Twenty-three isolated teeth were examined and comprise sixteen newly collected specimens (Supplemental Data 1) and the specimens originally assigned to Parvodus tikiensis (VPL/JU/TF/137–VPL/JU/TF/143, Supplemental Data 2). The labiolingual width (LLW) equals the apicobasal height (ABH) in morphotype IV (Table 1), whereas the crown proportions (MDL/ABH and MDL/LLW) are nearly equal to each other, as in morphotype III (Table 2). The principal cusp is broadly V-shaped with a rounded apex and has four pairs of cusplets on each side of the principal cusp (Fig. 6.1). The large triangular labial peg is positioned towards the base of the crown (Fig. 6.1), which contrasts with a small, subcircular lingual peg (Fig. 6.2). The latter is shifted towards the crown in comparison to the labial peg. The occlusal crest is sharp and slightly curved (Fig. 6.3). The ridges on the labial and lingual faces of the crown are curved and crenulated. There are small but distinct cristae along the lateral cusplets in labial and lingual views. The base of the crown is subtriangular but narrow and highly elongated (avg. BL/BW = 4.2 [N = 22]), centrally depressed and con- cave towards the lingual side (Fig. 6.4).
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