Chynagurl8 hi,
Your mare can only be registered as a Miniature horse. She is 25% Shetland pony by pedigree and most probably more if known of the unknowns
I would love to see a picture of your little mare to see if she has that "Arenosa" look to her as even with 25%, she could still look just as good as a 100% Arenosa. Not saying that other lines are not as good or better. It's just that the ponies and minis who have any Arenosa lines have a certain "LOOK" to them and many are very different in their attitude and way of going.
The "Arenosa" name(means dry creek) was started by Mrs. Audrey Barrett and her husband, Clinton(doc) in Victoria, TX. Audrey really wasn't going for the Arenosa name as much as the "Kewpie" name, but the "Arenosa" name has stuck more than what she had originally wanted. Nevertheless the Arenosa ponies that she bred were American Shetland ponies and most were on the small side. She was very FIRM about the FACT that her ponies were indeed Shetland ponies and NOT Miniature horses when the Miniature horses first started in the early 1970's. The reason for that was because AMHR would not and still does not recognize the Shetland pedigree in the paperwork...
She did register some of them with AMHR and FWF's Charro Of Arenosa is a black pinto registered with ASPC/AMHR and AMHA at 32" tall, and a perfect example of a American Shetland pony who is also a Miniature horse and 100% Arenosa too. Her lines were based on the black pinto Shetland stallion, Kewpie Doll's Oracle and through 2 of his better sons, Kewpie's Topper Of Arenosa and Kewpie Doll's Diablo she created a true dynasty of this unusal line of ponies. So to answer your question: is it a pony thing or a mini thing? Originally it was a pony thing, then some became minis, and now I believe there are more double reg. ASPC/AMHR Arenosa's than just ASPC Arenosa's. Most breeders I believe who breed 100% Arenosa's would refer to their's as ponies even if they are 38" and under because of their precious American Shetland bloodlines. Yes it is a pony thing and a mini thing
Hillman's Special K was bred by Gerald and Joan Flaby. Gerry and Wilma Hillman owned Special K who was a 32" grullo born in 1989. He was sired by Kewpie's El Monterry Of Arenosa-a liver chestnut 35.25" by Kewpie's Topper Of Arenosa-a chestnut pinto 36" son of Kewpie Doll's Oracle. Monterry dam was the very well used and most famous mare, Winnie The Pooh Of Arenosa a tiny 34" black-bay mare sire by Richardson's Pete of Fable Stables- a 38" black son of the very famous black Congress Champion, Curtiss-Frisco Pete. Special K's dam was a grullo 31" mare, Flying W Farms Katrina(Flying W Farms Masterpiece-28" x Flying W Farms Lady Grey-33")--unknown after that...pony??? who knows!
Special K only sired 5 foals through AMHR, the last one in 1999. So if he is still breeding I don't know<?> He would be considered 50% Arenosa and so your little mare would be 25% Arenosa bred, a Miniature horse with a healthy dose of Arenosa pony lines added. Lonnie Sharping of SOS Miniature horses still uses a Special K son, Heez Razin Special Kane SOS. I am just guessing that your little mare is Hillman's Princess K..? Her filly would be also be 25% Arenosa because of the sire's line to Kewpie's Fairy Princess of Arenosa-a 33.5" black mare by Kewpie's Topper of Arenosa x Tessie-Bell. I think having some Arenosa in any Miniature horse right now is a positive PLUS!
Good Luck with her and I hope everyone has helped answer your questions?
Jenny