PINNIXINAE ŠTEVČIĆ, 2005

Theil, Emma Palacios & Felder, Darryl L., 2020, Phylogeny of the genus Pinnixa White, 1846 (Crustacea, Brachyura, Pinnotheridae) and allies inferred from mitochondrial and nuclear molecular markers, with generic reassignment of twenty-one species, Zoosystema 42 (6), pp. 85-103 : 100

PROVISIONAL MORPHOLOGICAL KEY TO AMERICAN GENERA OF PINNIXINAE ŠTEVČIĆ, 2005

The present key must be regarded as provisional since many couplets require mature males, and these are not known or available for all species of each genus. Thus, it cannot be ruled out that exceptions to some of the applied characters may occur. It also includes one generic level taxon that remains to be named.

1. Carapace cardiac region posterior surface crossed from side to side by single sharp continuous ridge (most commonly associated with burrowing callianassid ghost shrimps, western Atlantic and eastern Pacific) (see Manning and Felder, 1989 for quality illustrations and examples) .......................... Austinixa Heard & Manning, 1997

— Carapace cardiac ridge, if present, not crossing the surface of carapace completely (most commonly associated with burrowing worms, mollusks, and upogebiid mud shrimps) ................................................................. 2

2. Maxilliped 3 dactylus large and heavy, as long as or longer than propodus, oriented in a wide angle, sometimes near perpendicular relative to it ( Fig. 2H ), or (for Glassella costaricana ) dactylus strongly reduced, inserted subdistally ( Fig. 2G ); carapace ovate, punctate, regions usually poorly marked; external surface of chela palm often bearing longitudinal ridges or lines of granules, sometimes setose ( Fig. 2E ); male pleon often with fused segments, telson broader than preceding segment ( Fig. 2I ) .......................................................................... 3

— Maxilliped 3 dactylus reaching to or slightly beyond the end of the propodus, dactylus and propodus elongated, oriented parallel or nearly parallel to each other ( Fig. 2C, L, P, T, X ); carapace varies; male pleon without fused segments, telson shape varied ...................................................................................................................... 5

3. Male pleon with telson short, broader than long, semiellipsoid ( Fig. 2I ); carapace punctate (western Atlantic, eastern Pacific) ...................................................................................... Glassella Campos & Wicksten, 1997

— Male pleon with telson semicircular, inflated, nearly as long as broad; carapace smooth, forming angle at lateral edges .......................................................................................... (“ Pinnixa sp.” ULLZ 13337, ULLZ 14141)

4. Mature cheliped fingers not strongly deflected from longitudinal axis of propodus, fixed finger not deflected ventrally from longitudinal axis ( Fig. 2B, S ); carapace convex, regions poorly marked ( Fig. 2A, R ) .............. 5

— Mature cheliped fixed finger deflected ventrally from longitudinal axis of propodus, often shortened ( Fig. 2K, O, W ); carapace varied ................................................................................................................................ 6

5. Cheliped fixed finger not conspicuously shortened relative to palm, chelae with little sexual dimorphism, ridge on fixed finger continuing partially on palm ( Fig. 2B ); carapace lateral angles setose ( Fig. 2A ); male pleon with telson semiellipsoid ( Fig. 2D ) (western Atlantic) ........................................................... Pinnixa White, 1846

— Cheliped fixed finger somewhat shortened relative to palm, male cheliped strong, female cheliped feeble, in some cases line of tubercles on chela palm, but no conspicuous ridge ( Fig. 2S ); carapace lateral angles rounded, with no patches of setae ( Fig. 2R ); male pleon with telson semicircular ( Fig. 2U ) (northeastern Pacific coasts, Alaska to Mexico) ................................................................................................... Scleroplax Rathbun, 1983

6. Male pleon with telson elongate, more than twice as wide as long ( Fig. 2Q ); mature cheliped fixed finger strongly reduced, replaced by a spiniform angle of propodus, sharp tooth at the base of dactylus ( Fig. 2O ); carapace anterolateral margins without tuberculate ridge, each with single lobiform tubercle just anterior to lateral extreme ( Fig. 2N ) (western Atlantic) ..................................................................................................... Sayixa n. gen.

— Male pleon with telson semicircular or semitriangular, not more than twice as wide as long ( Fig. 2M, Y ); mature cheliped fixed finger varied, if spiniform, with no additional sharp large tooth at the base of dactylus ( Fig. 2K, W ); carapace anterolateral margins often with tuberculate ridge, no conspicuous tubercle near lateral extreme ( Fig. 2J, V ) .................................................................................................................................................. 7

7. Ambulatory legs (P2–P4) subequal, slender, compressed, dactyli long and slender, nearly as long as propodi; carapace regions clearly defined, branchial region crossed by tuberculate ridge ( Fig. 2J ); male pleon with telson subtriangular ( Fig. 2M ) (western Atlantic, eastern Pacific) ................................................ Rathbunixa n. gen.

— First ambulatory legs (P2 and P3) slender, next two pairs (P4 and P5) swollen, dactyli strong, shorter than propodi; carapace regions clearly defined, branchial region with no conspicuous tuberculate ridge ( Fig. 2V ); male pleon with telson semicircular ( Fig. 2Y ) (western Atlantic) ................................................. Tubicolixa n. gen.

Figures

FIG. 2. — Morphological characters of the type species of Pinnixa White,1846 s.s., P.cylindrica (Say,1818), along with those for five molecularly segregated genera formerly treated in Pinnixa s.l.: A-D, Pinnixa cylindrica: A, male dorsal view;B, male cheliped;C, third maxilliped (adapted from Rathbun 1918:160 fig.99a);D, male pleon; E-G: Glassella costaricana (Wicksten, 1982): E, female holotype dorsal view; F, female cheliped; G, third maxilliped (adapted from Campos & Wicksten 1997: fig. 1, fig. 2c, a, with permission from Allen Press); H, I, Glassella faxoni (Rathbun,1918) n. comb.: H, third maxilliped; I, male pleon (adapted from Rathbun 1918:133 fig. 77b, a); J-M: Rathbunixa sayana (Stimpson, 1960) n. comb.: J, male dorsal view;K, male cheliped; L, third maxilliped; M, male pleon (L, M adapted from Rathbun 1918:158 fig. 98a, b); N-Q: Sayixa monodactyla (Say, 1818) n. comb., male (ULLZ 8713, Fort Pierce, FL, USA); N, dorsal view; O, cheliped; P, third maxilliped; Q, pleon; R, T, U, Scleroplax granulata Rathbun, 1893; R, female carapace and pereopods 2-5; T, third maxilliped; U, male pleon (R, T adapted from Campos 2006:fig. 1a-c, with permission from Magnolia Press; U, adapted from Rathbun 1918:171 fig. 109a); S, Scleroplax littoralis (Holmes, 1894) n. comb., female and male chelipeds (adapted from Rathbun 1918:146 fig. 89a, b); V-Y, Tubicolixa chaetopterana (Stimpson, 1860) n. comb.: V, male dorsal view; W, female and male chelipeds; X, third maxilliped; Y, male pleon (X, Y, adapted from Rathbun 1918:152 fig. 94a, b).