Table 1. Measurements of holotype skull and mandibles (USNM 546125) of Isthminia panamensis, in mm (modified after Perrin, 1975 and Tanaka & Fordyce, 2014).

	Measurement (mm)
Skull
Total length from the most anterior point to the posterior most point	571+
Cranial length	185+
Length of rostrum—from tip to line across hindmost limits of antorbital notches	381
Width of rostrum at base—along line across hindmost limits of antorbital notches	124*
Width of rostrum at 60 mm anterior to line across hindmost limits of antorbital notches	90*
Width of rostrum at mid-length	36+
Width of premaxillae at mid-length of rostrum	31+
Width of rostrum at 3/4 length, measured from posterior end	50*
Greatest width of premaxillae	78*
Projection of premaxillae beyond maxillae measured from tip of rostrum to line across foremost tips of maxillae visible in dorsal view	85+
Width of premaxillae at a line across posterior limits of antorbital notches	48*
Maximum width of premaxillae at mid-orbit level	52*
Preorbital width at level of frontal-lacrimal suture	184*
Postorbital width across apices of postorbital processes	232*
Distance from tip of rostrum to external nares (to mesial end of anterior transverse margin of right naris)	419+
Distance from foremost end of junction between nasals to hindmost point of margin of supraoccipital crest	68
Greatest width of external nares	49
Median length of the nasals	58
Maximum length of the right nasal	58
Median length of frontals on the vertex	25
Vertical external height of the skull from ventral most braincase to dorsal extremity of vertex	150+
Bizygomatic width	262*
Length of upper left tooth row—from hindmost margin of hindmost alveolus to tip of rostrum	329
Number of teeth—upper left	18
Number of teeth—upper right	18
Mandible
Maximum preserved length of left mandible	478+
Maximum preserved height of left mandible	74+
Number of teeth—lower left	17
Number of teeth—lower right	18
Length of the lower tooth row from tip of mandible to posterior margin of posterior most alveolus	315

Notes.

Asterisk indicates doubling of measurement from one side. Positive sign indicates preserved distance.