Table 1 Codes, symbols, and definitions of measurements used in the present study

Skull measurements

1

TSL

Total skull length: measured dorsally from the rostral end of the incisive bone to the caudal aspect of the occipital bone caudally

2

CBL

Condylobasal skull length: measured ventrally from an occipital condyle to the most rostral point of a premaxilla

3

BL

Basal skull length: measured ventrally from the point between the two occipital condyles to the most rostral point of the skull

13

ZW

Zygomatic width: measured between the extreme lateral points of the zygomatic arches. It represented the greatest width of the skull taken ventrally or dorsally

12

GWM

Greatest width across the mastoid processes: the maximum width from a mastoid process to the other one taken ventrally or dorsally

26

WAM

Width across acoustic meati: the distance between the two external acoustic meati measured dorsally

28

WS

The maximum width of the sagittal crest: at the posterior edge of the parietal bones taken dorsally

46

TFW

Temporal fossa width: obtained by subtraction of LWS from ZW

Cranial measurements

47

CL

Cranial length: measured dorsally from the midpoint between the two nasals to the caudal aspect of the occipital bone caudally

4

BCL

Basicranial length: measured ventrally from the midpoint of the two occipital condyles to the base of the presphenoid

25

WB

Width of braincase: the maximum distance between the extreme lateral points of the two parietal bones taken dorsally

20

SH

Skull height: measured laterally from the most dorsal point of the frontal bone to the lowest level of the jugular process ventrally

31

HOT

Height of the occipital triangle: measured from the top point of the occipital bone to the ventral limit of foramen magnum

22

NCL

Neurocranial length: Measured laterally from the foramen magnum to the middle point of frontal bone

14

LWS

Least width of skull: the minimum distance behind the two postorbital processes taken dorsally

Foramen magnum measurements

33

FMH

Foramen magnum height: mid-vertical height of the foramen magnum

34

FMW

Foramen magnum width: largest width of the foramen magnum

Orbital measurements

32

IHO

Greatest inner height of the orbit: measured obliquely from the postorbital processes caudally to the lacrimal bone rostrally

15

GIW

Greater interorbital width: the maximum distance between the two postorbital processes taken dorsally

16

ICD

Inter-canthi distance: the minimum distance between the medial canthi of the orbits taken dorsally between the upper edges of the orbits rostral to the two postorbital processes

Tympanic bulla measurements

11

TBL

Length of tympanic bulla: the distance from the rostral aspect to the caudal aspect of the tympanic bulla

27

TBW

Width of the tympanic bulla: measured as the distance from the lateral side to the medial side of the tympanic bulla

Facial measurements

7

FL

Facial length: measured dorsally from the postorbital process to the rostral extremity of the skull “Prosthion”

5

BFL

Basifacial length: measured ventrally from the base of the presphenoid to the rostral extremity of the skull

9

SL

Snout length: measured dorsally from anterior of the lacrimal bone to the rostral extremity of the skull

21

IF

Prosthion to infraorbital foramen: measured dorsally from the infraorbital foramen to the rostral extremity of the skull

24

DIF

Depth of skull at infraorbital foramen: measured laterally from the infraorbital foramen to the above point at the roof of the skull

35

IFMO

Distance between the caudal limit of the infraorbital foramen and the rostral limit of the orbit

36

IFC

Distance between the infraorbital foramen and the alveolus of the upper canine tooth

6

VCL

Viscerocranial length: measured dorsally from the midpoint between the two nasals to the rostral tip of the incisive bone

8

NL

Length of nasals: measured dorsally from the midpoint between the two nasals, at the suture with the frontal bone, to the rostral tip of the nasal bone

Palatal measurements

10

PL

Palatal length: The length of the hard palate measured along the midline from the caudal end of the palatine bone to the rostral end of the incisive bone

17

MxPW

Maximum palatal width: Maximum width of the hard palate measured at its widest portion (P4) internally

18

MnPW

Minimum palatal width: Minimum width of the hard palate measured at its narrowest portion (P2) internally

19

CAW

Width at canine alveoli: the width at the level of the two canine alveoli regardless they are found or not measured ventrally or dorsally

23

PDT

Palatal depth behind last tooth: measured laterally from behind the last upper cheek tooth to the corresponding point at the frontal bone

37

IL

Incisive foramen length

29

UCT

Alveolar length of upper cheek tooth row

30

MaT

Maxillary tooth row: length of the upper tooth row measured from canine tooth to the last molar tooth

Mandible measurements

38

ML

Mandible length: length of the mandible measured from the most rostral point of the mandible to the caudal limit of the condyloid process

39

AlM

Alveolar length of the mandible: measured from the tip point of the mandible to the last molar tooth even that teeth are found or lost

40

LTR

Alveolar length of tooth raw: length of the lower tooth row measured from canine tooth to the last molar tooth

41

LCT

Alveolar length of lower cheek tooth row: measured from the rostral limit of first premolar tooth to the caudal limit of the last molar tooth even that teeth are found or lost

42

MH

Mandible height: the distance between angular process and coronoid process

43

MFT

Distance between the mental foramen and the most rostral point of the mandible

44

MFMB

Length, along a vertical line, from the ventral limit of the mandibular foramen to the ventral border of the mandible

45

MFCB

Length along a horizontal line, from the mandibular foramen to the caudal border of the mandible

Skull indices

SI

Skull index: skull width (ZW)/ skull length (TSL)X100

WI

Length–width index: skull length (TSL)/ skull width (ZW)

CI

Cranial index: cranial width (WB)/ cranial length (CL) X100

FMI

Foramen magnum index: (FMH × 100)/FMW

FI

Facial index: skull width (ZW × 100)/viscerocranial length (VCL)

NI

Nasal index: (ZW × 100)/NL

PI

Palatal index: maximum palatal width × 100/palatal length

BR

Palato-basal index: the ratio of the palate to the basal length of the skull (palatal length × 100/ basal length)