Megalomma modestum ( de Quatrefages, 1866 )

Tovar-Hernández, María Ana & Carrera-Parra, Luis F., 2011, Megalomma Johansson, 1925 (Polychaeta: Sabellidae) from America and other world-wide localities, and phylogenetic relationships within the genus 2861, Zootaxa 2861 (1), pp. 1-71: 41-42

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Megalomma modestum ( de Quatrefages, 1866 )


Megalomma modestum ( de Quatrefages, 1866)  

Figures 17A–F View FIGURE 17 , 18A, D, G–H View FIGURE 18

Sabella modesta de Quatrefages, 1866: 451–452   , pl. 15, fig. 2, 22.

Potamilla anophthalma Hartmann-Schröder, 1960: 41–43   , Figs 89–91 fide Knight-Jones, 1997: 314.

Megalomma modestum   .— Knight-Jones, 1997: 314, Fig. 1F–L View FIGURE 1 .

Type material examined. [ MNHN] 163, three incomplete syntypes of Sabella modesta de Quatrefages, 1866   , Peru, Lima, South America. [ MCZ] 2171, holotype of Potamilla clara Chamberlin, 1919   (now synonym of M. coloratum   ) California, Laguna Beach, low tide, Coll. W. A. Hilton, complete but broken in anterior abdomen. [ ZMH] 15435, holotype complete and one incomplete paratype (only crown and anterior thorax) of Potamilla anophthalma Hartmann-Schröder, 1960   , Bei Ancas, Peru, September 13, 1950, Coll. Koepcke.

Additional material examined. [ ECOSUR] México, Oaxaca, La Ventosa , May 21, 2000, Colls SISV & JRBZ (3 specs)   . Panamá, Balboa, Club de Yates , Coll. SISV   , June 01, 2002 (3 specs); May 30, 2002 (1 spec.). [ USNM] 24484   , Ecuador, South side of Santa Elena # 7, Point   Ecuador, September 17, 1926 (1 spec.). [ USNM] 41513   , Perú, Mancora , June 14, 1960, Coll. Klawe (3 specs)   .

Diagnosis. Eyes only in dorsalmost radioles (spherical); dorsal margins of collar fused to faecal groove; thoracic chaetae Type A; abdominal chaetae narrowly hooded.

Description. Branchial crown as long as thorax with 11–21 pairs of radioles. One syntype (MNHN 163) with brown radiolar bands along entire crown. Outer surfaces of radioles quadrangular basally, rounded distally. Subdistal compound eyes spherical, present only in dorsalmost radioles ( Figs 17F View FIGURE 17 , 18H View FIGURE 18 ). All radiolar tips short. Dorsal collar margins square, fused to faecal groove, forming broad gap ( Figs 17A, D View FIGURE 17 , 18D View FIGURE 18 ). Dorsal lappets absent. Dorsal pockets well developed ( Figs 17A, D View FIGURE 17 , 18D View FIGURE 18 ). Ventral lappets rounded, not overlapped ( Figs 17B, E View FIGURE 17 , 18A View FIGURE 18 ). Anterior peristomial ring not exposed. Lateral collar margins covering bases of radioles ( Fig. 17C View FIGURE 17 ). Dorsal lips erect, triangular about one-quarter the length of branchial crown, with mid-rib. Three–4 short, dorsal pinnular appendages united by membrane. Ventral lips short, broadly rounded ( Fig. 18G View FIGURE 18 ). Caruncle and keel absent. Ventral sacs absent. Specimens fairly medium-size and plump. Total thorax-abdomen length 12–23 mm, maximum width 1.5– 4 mm throughout most of thorax. Seven thoracic chaetigers. Thoracic tori longest on chaetiger 2. Tori in chaetigers 2–3 occupy the entire distance between notopodia and ventral shield margins, contacting shields ( Fig. 17B, E View FIGURE 17 ). Length of thoracic torus in other thoracic segments slightly shorter than those in chaetigers 2–3, but also contacting shields. Inferior thoracic chaetae Type A. Thoracic uncini with crest surmounted by 8–10 rows of numerous minute teeth, handles 2x length of main fang. Companion chaetae with teardrop-shaped membranes. Abdomen with 42–54 chaetigers. Abdominal chaetae narrowly hooded; chaetae in posterior row longer than those in anterior row. Abdominal uncini with crest surmounted by 8–10 rows of numerous minute teeth. Pygidium rounded. Tubes covered with fine sand.

Remarks. de Quatrefages (1866) described M. modestum   (as Sabella   ) from Lima, Peru. Knight-Jones (1997) synonymized M. clara ( Chamberlin, 1919)   , a species described from Laguna Beach, California and M. anophthalma ( Hartmann-Schröder, 1960)   , a species described from Lima with M. modestum   . During this study, revision of types reveals that M. clara   ( Fig. 18C, E, I View FIGURE 18 ) is a synonym of M. coloratum   , not M. modestum   (see remarks section for M. coloratum   ). Thus, only M. anophthalma   ( Fig. 18B, F, J View FIGURE 18 ) is a synonym of M. modestum   . In Megalomma   , four species share the presence of eyes only in the dorsalmost radioles: M. bioculatum   , M. gesae   , M. kaikourense   , M. modestum   and M. pigmentum   . Among these, M. modestum   is unique in having the anterior peristomial ring not exposed beyond collar (exposed in some degree in the other four species).


Museum National d'Histoire Naturelle


Museum of Comparative Zoology


Zoologisches Museum Hamburg


El Colegio de la Frontera Sur (Mexico)


Smithsonian Institution, National Museum of Natural History














Megalomma modestum ( de Quatrefages, 1866 )

Tovar-Hernández, María Ana & Carrera-Parra, Luis F. 2011

Potamilla anophthalma Hartmann-Schröder, 1960: 41–43

Hartmann-Schroder, G. 1960: 43

Sabella modesta

de Quatrefages, A. 1866: 452