NEW GENUS AND TWO NEW SPECIES OF THARYBIDAE 

 (COPEPODA CALANOIDA) FROM THE GULF OF MEXICO WITH REMARKS 



ON THE STATUS OF THE FAMILY 



By Abraham Fteminger, Fishery Research Biologist 



Two heretofore undescribed species representing 

 a new genus of an obscure family of marine cala- 

 noids, the Tliarybidae, have been found during 

 studies on the copepod fauna of the Gulf of Mexico. 

 The plankton samples that contained these forms 

 are part of the extensive collections made by the 

 U. S. Fish and Wildlife Service M/V Alaska in the 

 Gulf of Mexico between 1951-1953. Apparently, 

 this is the first record of tharybids from the 

 western North Atlantic region. 



REMARKS ON THE THARYBIDAE 



Sars (1902) originally conceived of the family 

 name Tharybidae to place Tharybis macrophthalma 

 Sars, a northeastern Atlantic species of the mono- 

 typic genus Tharybis Sars. A second genus, 

 Psewlotharybis, was added by Scott (1909a) for 

 two species from waters off the British Isles. 

 Tanaka (1937) proposed a third genus (monotypic) 

 for a species from Suruga Bay, Japan, which 

 Brodski (1950) recently synonymized under Un- 

 dinella Sars. Brodski also removed Undinella, 

 together with its three species, from the Scolecith- 

 ricidae and placed it within the tharybid complex. 

 It is apparent from the available data tliat 

 Brodski's tharybid revision was justified. 



The position of the Tharybidae in relation to tlie 

 remaining families of the Calanoida has not been 

 established satisfactorily. Although the family 

 is usually included in Sars' section, the Isokeran- 

 dria, it is now widely recognized that this section 

 constitutes a heterogeneous complex unacceptable 

 to a natural system. At present, it seems best 

 to place the tharybids under Gurney's super- 

 family, Paracalanina, in a subgroup following the 

 Phacnnidac, the Scolecithricidae, and the Diaixi- 



NOTE.— Approved for publication November 9, 1956. Fishery Bulletin 116. 



dae. Although there is as yet little tangible 

 evidence to support this move, it is noteworthy 

 that these families are similar in the following 

 basic characteristics: (1) the occurrence of senso- 

 riform filaments and falcate spines on the second 

 maxillae, (2) organization of the fifth legs, (3) 

 segmentation of the swimming legs, and (4) form 

 of the rostrum. Moreover, in the above order 

 these families present an apparently natural and 

 progressive "line of development, to the extent of 

 secondary specialization of the appendages (e. g., 

 atrophy of the male cephalic appendages, com- 

 plexity of the sensoriform filaments, development 

 of the fifth legs, spinulation and flattening of the 

 swimming legs). Admittedly, these similarities 

 and their serial relations have been somevvhat 

 overgeneralized, but they strongly suggest a closer 

 relation between these families than that generally 

 held at present. 



The need for a formal description of the tharybid 

 complex is urgent but the lack of sufficient details 

 concerning most of the species prevents its presen- 

 tation at this time. For example, attempts at 

 precise separation of the tharybids and scole- 

 cithricids meet with difficulty. The usual struc- 

 tures of significance (such as body and appendage 

 segmentation, as well as arrangement and setal 

 ornamentation of appendages) are for the most 

 part similar, or at least tend to intergrade between 

 the two families. In this respect Scolecithricella 

 ctenopus (Giesbrecht) and the new genus described 

 present major obstacles to such a separation. 



Thus far a survey of the literature and study 

 of a limited quantity of reference material iias 

 revealed that only the swimming legs appear to 

 exhibit consistent difi'erences. As to the thary- 



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