Aspidosiphonidae, Baird, 1868

Silva-Morales, Itzahí & Gómez-Vásquez, Julio D., 2021, First records and two new species of sipunculans (Sipuncula) from the Southern Mexican Pacific, European Journal of Taxonomy 740 (1), pp. 77-117 : 103-104

Family Aspidosiphonidae

1. Hooks, if present, not in rings ....................................... Aspidosiphon (Akrikos) albus Murina, 1967

– Hooks in rings on the distal region of the introvert.........................................................................2

2. Longitudinal muscle layer divided into separate (or anastomosing) bundles ...................................... ................................................................................................ Aspidosiphon (Paraspidosiphon) ........3

– Longitudinal muscles in continuous layer (except under anal shield) ............................................... ..................................................................................................... Aspidosiphon (Aspidosiphon) ........7

3. Anal shield with grooves...................................................................................................................4

– Anal shield without grooves..............................................................................................................5

4. Papillae of anterior trunk scattered ..... Aspidosiphon (Paraspidosiphon) laevis de Quatrefages, 1865

– Papillae of anterior trunk in lines .............................. Aspidosiphon (Paraspidosiphon) cutleri sp. nov.

5. Compressed hooks bidentate, followed by dark pyramidal hooks ..................................................... ............................................................ Aspidosiphon (Paraspidosiphon) steenstrupii Diesing, 1859

– Compressed hooks bidentate, followed by pale pyramidal hooks....................................................6

6. Hooks bidentate, with streak vertical on the superior region ............................................................. .............................................................. Aspidosiphon (Paraspidosiphon) fischeri ten Broeke, 1925

– Hooks bidentate, with streak oblique on the superior region ............................................................. ............................................................................. Aspidosiphon (Paraspidosiphon) pastori sp. nov.

7. Individual units form into longitudinal ridges over dorsal half of anal shield .................................. ...................................................................... Aspidosiphon (Aspidosiphon) muelleri Diesing, 1851

– Without individual units that form into longitudinal ridges over dorsal half of anal shield.........8

8. All hooks unidentate; ill-defined anal shield ....................................................................................... ................................................... Aspidosiphon (Aspidosiphon) gracilis schnehageni Fischer, 1912

– Distal hooks bidentate; anal shield well-defined.............................................................................9

9. All compressed hooks bidentate, followed by dark conical hooks ..................................................... ............................................ Aspidosiphon (Aspidosiphon) elegans ( Chamisso & Eysenhardt, 1821)

– Distal bidentate compressed hooks, followed by proximal unidentate ones..............................10

10. Gut helicoidal; lives in gastropod shells; anal shield units not tightly packed and of similar size ........................................................................ Aspidosiphon (Aspidosiphon) gosnoldi Cutler, 1981

– Gut coils loose or absent; does not occupy gastropod shells; anal shield more solid, with closeset, granular units of differing sizes ............. Aspidosiphon (Aspidosiphon) misakiensis Ikeda, 1904