Mystery Endler “female”

[Shhmanning]

I’m wondering if anyone can help to identify what’s going on here. I added 2 male and 6 female Endlers to my community tank about 2 months ago. They were bought locally from a really reputable dealer where they were segregated in sexed tanks; however, over the past couple of weeks I’ve noticed one of the “females” developing coloured markings.
All the females looked virtually identical when I bought them and I’ve recently had my first brood of fry and have 2 others heavily gravid which is really exciting!!
But, this one female mentioned above has developed black spots and orange and blue tail markings. She’s significantly larger than the true males as you’ll see in the attached photos. Can anyone please provide some insight as to what might be going on here?
Thanks in advance.

 

[Innesfan]

Appears to be a late-maturing male. This happens in several livebearer species.

 

[Shhmanning]

Appears to be a late-maturing male. This happens in several livebearer species.

I did wonder about that, but it’s so much larger than the other males

 

[emeraldking]

It's a late male. Late males are always larger than normal males. But it's not an endler but another wild type guppy.
Late males look like females for a long time but lacking a gravid spot.

 

[Shhmanning]

It's a late male. Late males are always larger than normal males. But it's not an endler but another wild type guppy.
Late males look like females for a long time but lacking a gravid spot.

Hmmm…Okidokes.
Is it OK to keep him/her in the tank with the rest of them?

 

[Innesfan]

Hmmm…Okidokes.
Is it OK to keep him/her in the tank with the rest of them?

That depends on whether you want future matings between him and the Endler females. Given how well-formed the gonopodium is, there's a fair chance that has already happened.