Protobranchia, Pelseneer, 1889

Gofas, Serge, Luque, Ángel A., Oliver, Joan Daniel, Templado, José & Serrano, Alberto, 2021, The Mollusca of Galicia Bank (NE Atlantic Ocean), European Journal of Taxonomy 785 (1), pp. 1-114 : 75

Key to genera and species of Protobranchia found on GB

See also Killeen & Turner (2009) for identification of many North Atlantic Yoldiella Verrill & Bush, 1897 and Ledella Verrill & Bush, 1897 species not found in the present material.

1. Hinge plate narrowing but not interrupted under the umbo, with teeth forming a continuous series ........................................................................................................................................................... 2

– Hinge plate interrupted beneath the umbo by a ligamental pit ......................................................... 3

2. Outline regularly oval, longer than high ................... Tindaria sericea (Jeffreys, 1876) ( Fig. 31G‒I )

– Outline rounded anteriorly and tapering posteriorly .......................................................................... .............................................................. Pseudoneilonella latior (Jeffreys, 1876) [not found on GB]

3. Outline triangular with rounded ends; inside of shell nacreous ....................................................... 4

– Outline rounded, oval, or with anterior end rounded and posterior end tapering; inside of shell not nacreous ........................................................................................................................................... 6

4. Ventral margin smooth ................................. Ennucula corbuloide s (Seguenza, 1877) ( Fig. 31E‒F )

‒ Ventral margin crenulated by the termination of internal rods ......................................................... 5

5. Shell plump, externally with fine radial microsculpture ..................................................................... ................................................................................ Nucula atacellana Schenck, 1939 ( Fig. 31C‒D )

– Shell rather compressed, sculpture mostly commarginal ................................................................... ..................................................................................... Nucula tumidula Malm, 1861 ( Fig. 31A‒B )

6. Posterior end acute or more or less angular ...................................................................................... 7

– Posterior end rounded, even if somewhat tapering ........................................................................... 8

7. Posterior end acute, umbo anterior to vertical midline ....................................................................... ........................................................................... Ledella messanensis (Jeffreys, 1870) ( Fig. 32A‒B )

– Posterior end bluntly angular, umbo posterior to vertical midline ..................................................... ...................................................................................... Ledella cf. orixa ( Dall, 1927) ( Fig. 32C‒D )

8. Shell less than 2 mm, white, rounded in outline ................................................................................. .......................................................................... Pristigloma minima (Seguenza, 1877) ( Fig. 31J‒K )

– Shell larger, definitely longer than high ............................................................................................ 9

9. Shell inflated, posteriorly tapering .................... Yoldiella semistriata (Jeffreys, 1879) ( Fig. 32G‒H )

– Shell very compressed, posterior part broadly rounded ..................................................................... .......................................................... Yoldiella valorousae Killeen & J. A. Turner, 2009 ( Fig. 32I‒J )

Figures

Fig. 31. Protobranchia 1. A–B. Nucula tumidula Malm, 1861, BANGAL 0711, V5, 1631 m, 5.5 and 5.4 mm.C–D. Nucula atacellana Schenck, 1939, BANGAL 0711, V10, 1720 m, 3.5 mm.E–F. Ennucula corbuloides (Seguenza, 1877), BANGAL 0711, V2, 1706 m, 3.2 mm. G–H. Tindaria sericea (Jeffreys, 1876), BANGAL 0711, V2, 4.7 mm.I. Tindaria sericea, BANGAL 0711, V5, 4.5 mm. J–K. Pristigloma minima (Seguenza, 1877), SEAMOUNT 1, DW111, 675–685 m, 1.7 mm. Scale bars = 1 mm.

Fig. 32. Protobranchia 2. A–B. Ledella messanensis (Jeffreys, 1870), BANGAL 0711, V10, 1720 m, 5.8 mm. C–D. Ledella cf. orixa (Dall, 1927), BANGAL 0711, V5, 1631 m, 2.0 mm. E–F. Syntype (USNM 108190) of Leda orixa Dall, 1927, off Georgia 30.975°N, 79.6417°W, 538 m, R/V Albatross, 3.6 mm (photograph by Ellen Strong, reproduced with the permission of the National Museum of Natural History, Smithsonian Institution, 10th and Constitution Ave. N.W., Washington, DC 20560-0193 http://www.nmnh.si.edu/). G–H. Yoldiella semistriata (Jeffreys, 1879), BANGAL 0711, V2, 1706 m, 3.2 mm. I–J. Yoldiella valorousae Killeen & J.A. Turner, 2009, BANGAL 0711, V2, 1706 m, 3.0 mm. Scale bars = 1 mm.