Evseenko et al.: New data on the morphology of 7yphlachirus elongatus 
123 
sample indicate that the fin developed to varying degrees 
and development did not depend on the size of the fish. 
Therefore, the presence of the pectoral fin and the num- 
ber of rays in it cannot serve to identify species. On the 
basis of this result, we come to the same conclusion as 
Chabanaud (1948): there are no sufficient causes for sav- 
ing the independence of the 3 nominal Typhlachirus spe- 
cies. Chabanaud’s revision was based on a small number 
of specimens, and in this work, non-type specimens from 
only one of the type localities were examined. Therefore, to 
confirm our conclusion about the possible monotypy of the 
genus, it is necessary to study available type specimens 
and new specimens of T: lipophthalmus and T. caecus from 
the regions where the type material was captured (off the 
island of Borneo Island and in the Strait of Malacca). 
Acknowledgments 
The study was supported by the state assignment to the 
Shirshov Institute of Oceanology of the Russian Academy 
of Sciences (no. 0149-2019-0009) and work was done on 
the theme “Ecolan E-3.4—Ecosystem of the Mekong River 
in the context of global climatic changes and anthropo- 
genic impact.” The work was held within the state assign- 
ment of the Lomonosov Moscow State University (no 
121032500084-6). 
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