Donax, LINNAEUS, 1758

Guerra, Juliano, Castro, Guerra de, Martinez, Pablo Ariel, Passos, Flávio Dias, Marques, Rodrigo Cesar, Siqueira, Ana Paula & Dornellas, Siqueira, 2025, Geometric morphometrics of donacids from Brazil reveals a new species, Donax trapesialis n. sp. from Northeastern coast, Zoosystema 47 (19), pp. 399-412 : 408

DICHOTOMOUS KEY TO BRAZILIAN DONAX LINNAEUS, 1758 , ADAPTED FROM LIMA & MARQUES (PERS. COMM.)

1. Nodular posterior surface ............................................................................ Donax hanleyanus Philippi, 1847

— Non-nodular posterior surface ..................................................................................................................... 2

2. Evenly rounded posterior ridge .................................................................................................................... 3

— Carinate posterior ridge with an angle ......................................................................................................... 4

3. Concave or flat ventral margin, trapezoid shape .......................................................... Donax trapesialis n. sp.

— Convex ventral margin, subglobose shape .................................................... Donax gemmula Morrison, 1971

4. Visible growth lines, punctuated .............................................................. Donax denticulatus Linnaeus, 1758

— Imperceptible growth lines .......................................................................................................................... 5

5. Strongly triangular, sharp posterior ridge ......................................................... Donax striatus Linnaeus, 1767

— Moderately triangular, wide, unevenly rounded posterior ridges, two posterior slope surfaces easily distinguishable ........................................................................................................... Donax vellicatus Reeve, 1855