Big Upright Sabal sp for ID

[PalmatierMeg]

Among the very large Sabals inhabiting Sabal Row on the east side of the yard is one that outshines the rest. Even though it is several years younger than the original inhabitants but is just as tall and big around, with the largest leaves. It carries these leaves on massive, upright green petioles. Its stem has long papery ligules unlike any of the other Sabals. My husband is no Sabal afficionado but he really likes this palm. I grew it from seeds I obtained as "Sabal mauritiiformis" way back around 2009/10 but two visiting PTers whose opinions I highly value have told me it is not that species. But no one has been able  to confirm what species it is. Can someone here tell me?

I took the following photos this evening and I can take more tomorrow when lighting is better. It is hard to encompass the full scope of this Sabal

Photo #1) Trunk with my husband for scale

Photos #2) Ligules on trunk

Photo #3) Width of petiole with my hand for scale

Photos #4-6) Views of fronds

[Zeeth]

Looks like it's in the S. causiarum/S. domingensis species complex. Some say that presence of the papery ligules are enough to call it S. causiarum, but the Sabal monograph says seed size/shape is the best way. 

 

Fruit of S. causiarum are spherical and 7-10 mm in diameter with seeds being 6-8 mm in diameter and 4-6 mm high.  S. domingensis fruit are pyriform and larger (11-14 mm in diameter) with a larger seed (8-11 mm in diameter).

[sonoranfans]

Yep looks like my causiarum though a bit younger with less trunk.  the trunk will swell more and get fat if its causiarum.  Mine is currently 40" diameter without leaf bases.  As Keith said, the inflorescences of causiarum are branched to 3 orders with 7-10mm fruits.  Domingensis is 11-14mm with 4th order branching of inflorescences.  Mine turned out to be causiarum though I bought it as domingensis.  It has 3 orders branching, fruits 8+/- mm.  It showed ligules a bit late, when it got near trunking size, and it still does have lots of ligules.