PMC

A. Labral plica. Oblique axial FS-T1WI of an MRA. The labral plica shows a hypointense linear structure (arrow), interposed between the labrum (arrowhead) and the anteromedial joint capsule.
B. Neck plica. Oblique coronal FS-T1WI of MRA. The neck plica shows a hypointense linear structure (arrow), paralleling the medial margin of the femoral neck.
C. Pectinofoveal fold. Oblique coronal FS-T1WI of MRA shows the pectinofoveal fold, extending to the lesser trochanter (arrow).
D. Ligamental plica. Oblique coronal FS-T1WI of MRA shows the ligamental plica (arrow), paralleling the ligamentum teres (arrowhead).
FS = fat-suppressed, MRA = MR arthrogram, T1WI = T1-weighted image

Nomenclature of parietal (A, B, D) and palatal (C) plicae and lamellae. A shows a “Gudeodiscus-type” plication with two lamellae B shows a usual Endothyrella lamellation D shows a “Chersaecia-type” lamellation with long lower plica and middle plica not connected to the apertural fold (in most species however, they are connected forming a continuous plica). Small arrows under the letters show the direction of the aperture (A shows dextral, B and D sinistral specimen). Large arrow next to C shows the direction of counting of palatal plicae (first above, last below). Abbreviations: af: apertural fold; al: anterior lamella; am: apertural margin (peristome); ip: intermediate plica; l: lamella; lp: lower plica; mp: main plica; pl: posterior lamella; pd: posterior denticles; pl: posterior lamella; up: upper plica. Note that there are upper and lower plicae on both (palatal and parietal) walls.

The “plica” is a synovial fold interposed between radial head and capitulum humeri.

A PCA using 31 specimens labeled Plica plica. Scales around mid-body (28.20%), lamellae under fourth toe (13.74%), lamellae under fourth finger (11.09%), number of suboculars (7.14%), number of supraorbital plates (5.87%) accounted for 66.04% of the variation. Other traits used in the PCA included: dorsolateral fold, ventrolateral fold, scales between canthals, scales between nasals, loreals at canthal, scales between nasal and rostral, number of canthals, loreals keeled, upper labials, longest upper labial, lower labials, postmentals, ventral-post auditory tufts of spines, total tufts of spines, length of head, dorsal scale size, dorsal scale keels, dorsal pattern, and antegular fold.