(1) Submentum is vestigial, membranous, lacks muscles (Kluge 2004: Fig.53:E, 57:H, 60:C) (unlike other Ephemeroptera, which have muscles going from submentum to mentum ). In other respects labium is differently specialized in Arthroplea and Radulapalpata (see below).

(2) Larval fore protoptera are fused with scutellum up to apex of scutellum; thus, posterior margin of mesonotum between protoptera is straight or concave, and free portion of each protopteron narrows from its extreme base to apex (Kluge 2004: Fig.54:A, 55:A, 58:A). Non-unique apomorphy (see Index of characters [1.2.6]) unlike Pseudiron and many Tridentiseta.

(3) In imago and subimago on all legs 1^st tarsal segment is distinctly articulated with tibia – thus, all tarsi are 5-segmented (like in condition primitive for Amyocerata). This is a secondary restoration of tibia-tarsal articulation (see Morphology and ontogenesis); non-unique apomorphy (see Index of characters [2.2.84]).

(4) Larval claws are usually sharply curved and turned ventrally (posteriorly), perpendicular to the femur-tibia flatness; probably, primary for Pentamerotarsata is presence of one row of denticles on inner side of claw and several larger subapical denticles on anterior (dorsal) side of claw. The denticles on inner side of claw are retained in Arthroplea and Kageronia only (Kluge 2004: Fig.54:G), being lost in other Radulapalpata; the subapical denticles are present in Arthroplea and many Radulapalpata, being lost in selected species. 

Unlike mature larva, larvula has 2 equal rows of denticles on inner side of claw (Degrange 1960). 

Non-unique character: the same in some Ephemerella/fg1, Leptophlebia/fg1 and others taxa (see Index of characters [1.2.21-22]).

(5) Penis has peculiar composite structure: on apex of each penis lobe sclerotization of ventral wall terminates by a projection named ventral sclerite; on lateral side it is continued to a projection named outer sclerite; outer sclerite bears a latero-dorsal spine directed dorsally; on its median side each penis lobe bears a median titillator – sclerotized pointed appendage; from its base, titillator is directed toward apex of penis, curved in median plane, and its apex is directed ventrally (Spieth 1938:I: Fig.5-8; Bogoescu & Tabacaru 1962: Fig.2; Kluge 2004: Fig.59:B-C). In many Pentamerotarsata, which have penis lobes fused at a long distance, the median titillators being situated between penis lobes, are dipped by their bases into deep pouches, thus in rest position only apices of titillators are projected outside; in excited condition titillators are turned out from the pouches. In other representatives of Pentamerotarsata (many Rhithrogena/fg1) penis lobes are deeply separated and median titillators are situated on their median surfaces; probably such external position is secondary for Pentamerotarsata. These details of penis structure are present in Arthroplea and majority of Radulapalpata, but in selected representatives some of these details are lost.

(6) Larval caudalii are usually long, primary swimming setae [see Euephemeroptera (3)] are more or less reduced. If swimming setae are present, they are simple and non-specialized: unlike Pseudiron, many Eusetisura and Tridentiseta, they are not thickened at bases and not curved distally. In spite of their simple structure, these setae can be recognized as primary swimming setae, as they form rows on lateral sides of paracercus and median sides of cerci only, but not on lateral sides of cerci. Secondary swimming setae on lateral sides of cerci are usually absent, being present in some species of Stenonema/g1 only. In many Radulapalpata swimming setae are completely lost. Non-unique apomorphy (see Index of characters [1.3.66]).

Reduction of primary swimming setae is connected with adaptation of majority (but not all) of Pentamerotarsata to inhabitancy in swift current. At the same time, unlike some other rheophilous mayflies, in majority of Pentamerotarsata larval paracercus is not shortened, being as long as cerci; only in Epeorus/fg1, Acanthomola and Anepeorus/fg1 larval paracercus is reduced to 1 segment (see Index of characters [1.3.64]); intermediate stages of shortening of paracercus in Pentamerotarsata do not occur [in imago and subimago paracercus is always vestigial – see Heptagennota (6)].