Michael Locke wrote a paper (rather a brief note) on the structure of septate desmosomes of a caterpillar (Calpodes ethlius). LINK HERE. It shows a possible arrangement of such a structure, honeycombed in one tangential array and in other cuts showing a parallel periodicity. The maganification bars on micrographs are not specific, i have to determine that they represent about 80nm, as remeasured using the size of an insect ribosome as the gold standard. I redrew a diagram (I am not sure why an 16 pronged asterisk like symbol was chosen for his diagram but it is reproduced and edited and overlies a portion of his micrograph of a tangential section of a septate desmosome. Another image from the same micrograph (enlarged to the same degree) has one potential that he recommended for the parallel section of the septate desmosomal honeycomb cells. His bar marker and the ribosome size are added to the images below. A larger scale diagram (slightly modified (with different planes of section that he provided) is included (red asterisk-like structures on the right lower portion of the png. His dimensions of adjacent plasmalemma being 14nm apart dont fit the size in the same micrographs of a typical ribosome. septa are more like 25-30nm lucent area and 40nm dark to dark line. The diameter of one hexagonal structure he named at about 105nm.
Just googling what the cadherins might look like in insects and other “bilateral organisms” using the term in the introduction of Sasaki et al, 2017 (LINK HERE) looking at those protein structures, correlating the differences in the extracellular EC repeats, might easily explain the differences in dimensions and organizations of these sepatae (and other) desmosomes.
ONE NOTE: it is clear that there are restricted positions where desmosomes in the mammalian liver are found…. mainly at the junctions of hepatocytes at the point they form the bile canaliculus…. reading from a review by John Pettitt (LINK HERE) he mentions that the classical cadherins are responsible in part for cell polarity.
JUST a note: in the lineup of evolution, it looks like the transmembrane, and intracellular and the very close extracellular (right next to the transmembrane domain) dont change very much, compared to the pile of extracellular repeats and other kinks.
It is an awesome universe. Life is awesome and complicated. Learning about life is worth the effort required to maintain sanity.