How's this?
Reptilian Form (Su): At 1st level, a greater segarran may assume the form of a humanoid/reptilian hybrid. While in this form, the segarran increases by one size category, gains a +2 natural armor bonus, and gains a bite and tail slap attack. The bite attack is a primary natural weapon that deals 3d6 + segarran's Str modifier points of damage, and a tail slap attack that deals 2d10 + 1-1/2 times the segarran's Str modifier points of damage.
In reptilian form, the segarran gains a swim speed of 30 feet. It gains a +8 racial bonus on any Swim check to perform a special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.
Tail Sweep (Ex): At 3rd-level, when assuming reptilian form, a greater segarran can sweep with its tail as a standard action. The sweep affects a half-circle with a radius of 5 feet, extending from an intersection on the edge of the segarran's space in any direction. Creatures within the swept area are affected if they are one or more size categories smaller than the segarran. A tail sweep automatically deals tail slap damage and affected creatures must make Reflex saves (DC 10 + 1/2 segarran's Hit Dice + segarran's Strength modifier) or be knocked prone.
Wings (Ex): At 5th level, when assuming reptilian form, a greater segarran grows two batlike wings. This grants it a fly speed of 50 feet (poor maneuverability). Additionally, the segarran gains two wing buffet attacks as secondary natural weapons that deal 1d4 + 1/2 Strength modifier points of damage.
Should the greater segarran gain the reptilian and shapechanger subtypes? Should we also add the reptilian subtype to the lesser segarran?