Table 3. Optimized synontomorphies supporting the growth stages of Tylosaurus proriger.

Growth stage	Unambiguous	Ambiguous
1	n/a	n/a
2	QH between 50 and 99 mm, quadrate mandibular condyle ossified	TSL between 400 and 800 mm, quadrate ala rim distinct, coronoid posteroventral process present as bump
3	Quadrate tympanic ala thick**	None
4	Quadrate alar concavity shallow	None
5	Occipital condyle ossified	Quadrate suprastapedial process intermediate length**, quadrate suprastapedial process not curved medially*
6	Premaxillary rostrum foramina small	None
7	Premaxilla-maxilla suture m-shaped, quadrate mandibular condyle rounded	None
8	Quadrate infrastapedial process rounded	Premaxillary rostrum ≥5% TSL, parietal nuchal fossa present
9	QH ≥13% TSL, dentary deep	Jugal posteroventral process present*
10	Frontal posterolateral processes thick*, dorsal ridge of dentary predental process present	Pterygoid ectopterygoid process thick, coronoid anterolateral notch present and shallow
11	TSL between 1,000 and 1,499 mm, QH between 150 and 199 mm, dentary length ≤55% lower jaw length	None
12	Premaxillary rostrum distinctly knobbed	None
13	Distance between 1st and 6th dentary teeth ≤23% TSL	None
14	Quadrate suprastapedial process thick	Dentary slender
15	Distance between 1st and 6th dentary teeth ≤35% dentary length, dentary length between 60% and 56% lower jaw length, coronoid posteroventral process present and fan-like	None
16	None	Premaxilla-maxilla suture u-shaped, dentary deep
17	Quadrate alar concavity deep	None

Note:

Reversals are bold, phylogenetic characters are indicated by an asterisk, and characters that are purportedly diagnostic of T. proriger are indicated by two asterisks.