I have 8 cells here - FlyWire - from the outer lobula plate rind that I was not able to complete or identify in my pass (as described here). I would love your assistance!
I think a few of these are probably a Y type, but there’s confusing things all around here. One is probably centrifugal.
Feel free to make live edits if you find something!
I’d say, 4 of them are Y.
The short green one (065) might be an LPi.
The longest could be a merger (didn’t found any merging spot, though). The outer part has a missing extension, that looks like a C cell (I didn’t trace it to the end).
The one ending with 326 is unfinished. It’s continuation goes into a merger, but I didn’t check, what part of that merger is correct and if it continues beyond that, so it’s hard to say, for now, what type it is.
I don’t know, what to think about 218, but it also looks, like its unfinished.
Thanks for the feedback! I’ve done some updates and narrowed things down a bit:
Updated link: FlyWire
https://ngl.flywire.ai/?json_url=https://globalv1.flywire-daf.com/nglstate/5203824817995776
I’ve checked (more or less) the whole -740 and didn’t find any mergers. I’m starting to think, maybe there isn’t a merger. Maybe it is a C cell, but malformed. Maybe it grew in the wrong place at the wrong time and was dragged away from its normal position. Not sure, if it’s possible though 
Thanks so much for the assistance and feedback, KK!
I’ve eliminated the T cell and Lpi now, which leaves us just with this stranger. I’ve merged together your additions, and made a few clean ups/additions myself where I could find them. I also combed through the 2D again, and I’ve marked two points that might be mergers. Though I will say even if they are mergers, we’re still drawing a blank on what this cell is!
https://ngl.flywire.ai/?json_url=https://globalv1.flywire-daf.com/nglstate/4988991979913216
I’ve tried looking at friend cells in different places, but not finding any clues. This bundle is mostly T5s, a few T4s, and one Tlp. I’m most inclined to think it’s an Lpi merged with something else, assuming it isn’t, as you suggested, a poorly grown ‘mistake’ neuron.
You’re welcome 
Unfortunately, I can’t find any mergers either.
Maybe it’s a new kind od cell, some sort of probe connecting lamina with lobula and lobula plate. There aren’t any other cells directly connecting these neuropils, so maybe there’s a C cell repurposed just for this.Who knows. After all, we’re doing researching, so might find unknown unknowns
Quick guide, how to differentiate between T cells:
T1: Lamina → Retina
T2: Medulla → Lobula (goes through the whole Medulla)
T3: Medulla → Lobula (arborizes in the proximal part of the Medulla only)
T4: Medula → Lobula Plate
T5: Lobula → Lobula Plate
ChaTnew1: Medulla → Lobula and Lobula Plate
The last one is also known as Tnew1 in some pictures.
Categorizing T cells definitely needs to have the optic lobe’s neuropils turned on, because they sometimes have their arborizations very close to the borders of the neuropils.
do you have a picture of the ChaTnew1 have not seen this before?
i am thinking on the differences more like this
T1= basket
T2= long arbour
T3= short arbour
T4 = turn 180 degree, goes into medulla
T5= turn 180 degree, goes into lobula
I was sure, that Tnew1 (ChaTnew1) cell has already been posted in the Visual Cell Type Illustrations thread. Turns out, it wasn’t, so I’ve added it.
Edit: The part below is wrong
as for T3 and T4 it’s not so easy, unfortunately.
For example:
T3:
T4:
There’s also a possibility, to mistake T4 with T5.
i am pretty sure both of the ones you have posted are T4 cells
T3 looks like this
https://ngl.flywire.ai/?json_url=https://globalv1.flywire-daf.com/nglstate/5230884538023936
i agree about T4 and some of the T5 that is close to medulla beeing difficult to make apart
I was thinking about it. My T3 have its proximal end in the lobula neuropil, but I’m starting to think, that the 3D models of the neuropils aren’t exactly matching the 2D slides.
Yesterday I was sure, that they are correct, but the more time passes, the more I think, I got it wrong and the more I agree, that T3 should look only like the ones you posted.
At least, I didn’t post my classifications yet.
Agree about the neuropils not completly matching, making it even more difficult with the T4 and T5, from what i have observed i think there are many T4 cells that are just under the medulla neurophil, because of this i tend to classify all of the ones i am unsure about as T4
I wish, I could make the models more accurate and even add all the layers. Unfortunately, I don’t know how to.
Thanks, for straightening my knowledge about the T3s
I hope this can help clear the T2, T3, T4, and T5 classifications a bit:
Or, for flowchart ease:
And then there are cells like these, where both arbors seems to be in the LP, lol.
I suppose, these are T4s.
Yes, despite the weirdness of the 3D model, those are T4s!
I haven’t been able to find a way to easily tell via 2D where Lp ends and Me begins, without utilizing other known neurons to judge by. But because these are “U-turn” types, and the arbor is close to the neuropil border, it’s safe to assume it’s a T4 type (Lpi do not have a U-turn structure).
I have trouble identifying T2 vs T2a cells. I know the difference in the number of arbors on the Medulla’s branch, but it isn’t always a clear difference. So I found this:
T2a lacks inputs from L cells unlike T2, despite its proximal medulla innervation
here: https://www.eneuro.org/content/9/2/ENEURO.0053-22.2022
Using the Connectivity app I was able to find at least one T2/T2a, which was connected with an (unfinished) L5 cell: FlyWire. The hidden cells are all the other upstream partners.
I will have to check it for more cells, but thought, it might be useful for other Flyers.
Using the Connectivity app seems to be also a good way to find unfinished cells.
KK - the connectivity app is a great idea!
I ran it on our mystery cell and came away with a few insights:
The upper (C-style) portion synapses with an L1;
The medulla bend synapses with Mi1 and a Tm cell (possibly Tm25);
The lobula portion interfaces with a cell type that goes through lobula, medulla, and into the CB.
You can see pathway mirroring very clearly with these cells:
New view here: FlyWire
Knowing these connections might help us ID this cell, or find which portion(s) might be mergers.
Agree, checking upstream and downstream partners might help. Actually, I have 15 of that kind of cells, that goes through medulla, lobula and projects into the CB. Don’t have a type for them, but checking their synaptic partners might help narrowing down, what that mysterious cell is or isn’t.
For something completely different: does anyone have a foolproof way to differentiate subtypes of T4 and T5? I was trying to find some barriers between LOP layers in 2D, but to no effect. I was also searching for upstream and downstream partners, but it seems, that all the subtypes connect with the same types of cells.
By the way, T4a, T4b, T5a and T5b can be further divided into T4ai and T4aii, T4bi and T5bii, etc. However, the distinction is based only on neurons response (directionality), so it’s impossible to say, which one is which from the anatomy only.
