Laemolyta Cope, 1872

Mautari, Kelly Cristina & Menezes, Naércio Aquino, 2006, Revision of the South American freshwater fish genus Laemolyta Cope, 1872 (Ostariophysi: Characiformes: Anostomidae), Neotropical Ichthyology 4 (1), pp. 27-44: 28-31

publication ID

http://doi.org/ 10.1590/S1679-62252006000100002

publication LSID

lsid:zoobank.org:pub:22071950-40B5-4151-AB3C-D6AE6A2607E9

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http://treatment.plazi.org/id/038187AC-9960-FC43-FBEA-F89DFC8B85FA

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scientific name

Laemolyta Cope, 1872
status

 

Laemolyta Cope, 1872  

Laemolyta Cope, 1872: 258   . Type species: Schizodon taeniatus Kner, 1859   , by monotypy; Eschmeyer, 1998: 1986 [catalog]; Garavello & Britski, 2003: 72 [catalog].

Schizodontopsis Garman, 1890   subgenus of Anostomus   . Type species: Schizodon taeniatus Kner, 1859   , type by subsequent designation ( Eigenmann, 1910: 425); Eschmeyer, 1998: 2121 [catalog]; Garavello & Britski, 2003: 72 [catalog].

Diagnosis. Laemolyta   is distinguished from all other genera of the Anostomidae   in having the symphyseal tooth of the dentary approximately equal in size to the second tooth with both teeth spatulated, very compressed, and with the upper edge straight (vs. symphyseal tooth sometimes much larger than the second tooth or slightly larger than the second tooth and sometimes cusped as the remaining dentary teeth, thick or recurved) ( Fig. 1 View Fig ). Adult specimens have a supra-terminal mouth, a condition that is shared only with Anostomoides   among anostomids. In spite of Winterbottom’s interpretation of a supraterminal mouth in the Anostominae   , in our interpretation all members of this subfamily have a superior mouth. Species of Anostomoides   , however, have the symphyseal tooth longer than the second tooth on the dentary. Laemolyta   further differs from all other examined genera of the Anostomidae   in possessing a protuberance on the anteroventral region of the ectopterygoid ( Fig. 2 View Fig ), in the elongated mesopterygoid ( Fig. 2 View Fig ) with a small ventrally-directed process on its lateral surface and its ventral margin poorly developed, and in the relatively wide premaxilla with a fold on its median ventral margin that is prolonged as a rounded process medially, the upper premaxillary margin slightly recurved ( Fig. 3 View Fig ).

Popular name. Piaus and Aracus.

Distribution. Amazon, Essequibo, and Orinoco basins.

Cope (1872), described the genus Laemolyta   to include Schizodon taeniatus Kner, 1859   , that according to him differed from the remaining species of Schizodon   known at the time in which the branchiostegal membranes were entirely free from the isthmus, the dentary teeth truncate with their Remarks. Five species are recognized within Laemolyta   in this study: L. fernandezi Myers (1950)   , L. garmani ( Borodin, 1931)   , L. orinocensis ( Steindachner, 1879)   , L. proxima ( Garman, 1890)   , and L. taeniata ( Kner, 1859)   .

upper edge entire and premaxillary teeth crenate. The typespecies of the genus, Laemolyta taeniata   , had been first described in Schizodon   by Kner (1859) but was later included in Anostomus   by Günther (1864).

In his study of the genus Anostomus, Garman (1890)   recognized three groups or sub-genera based primarily on the snout shape, position of the mouth opening, and form of dentition: Anostomus   , Schizodontopsis   , and Schizodon   . Schizodontopsis   (= Laemolyta   ) was primarily characterized by having its mouth aligned obliquely forward and upturned and by the lower jaw bearing large truncate teeth with their upper edges straight. He described two species that he assigned to this group: Anostomus (Schizodontopsis) proximus   and Anostomus (Schizodontopsis) varius   and considered Anostomus (Schizodontopsis) nitens   to be a “variation” of Anostomus (Schizodontopsis) varius   .

Eigenmann & Eigenmann (1891) listed in Laemolyta   the species that Garman (1890) considered to belong in the subgenus Schizodontopsis   and others including L. taeniata   , L. proximus   , L. varius   , L. varius nitens   , and L. orinocensis   . Subsequently, however, Eigenmann (1910) included only the typespecies of the genus Schizodon taeniatus Kner, 1859   in Laemolyta   ; and allocated the other species previously included in this genus to Anostomus   . In the same paper Eigenmann considered the sub-genus Schizodontopsis Garman, 1890   to be synonymous with Laemolyta   .

Myers (1950) retained Schizodontopsis Garman (1890)   in the synonymy of Laemolyta   and based on Garman (1890), Borodin (1931), and Steindachner (1879) prepared a list of eight species of Laemolyta   : L. fasciata Pearson, 1924   , L. garmani ( Borodin, 1931)   , L. nitens ( Garman, 1890)   , L. proxima ( Garman, 1890)   , L. taeniata ( Kner, 1859)   , and L. varia ( Garman, 1890)   all from the Amazon basin, L. orinocensis ( Steindachner, 1879)   from the río Orinoco basin and L. laticeps (Eigenmann, 1912)   from Guiana. Additionally, he described Laemolyta fernandezi   , based on a 72.5 mm SL juvenile collected in the upper río Orinoco. Myers noted that in Laemolyta   the branchiostegal membranes are in actuality closely connected to the isthmus, contrary to what was reported by Cope (1872). Myers also distinguished Laemolyta   from Schizodon   , mainly by dentition, with Laemolyta   having the dentary teeth truncate with their upper edges straight whereas Schizodon   has cuspidate teeth on both jaws.

Fowler (1950) included in Laemolyta   all species recognized by Myers (1950), with the exception of L. laticeps   and L. orinocensis   , and added L. borellii (Boulenger, 1900)   of the rio Paraguay basin to the genus. The form of dentition described by Cope (1872) and Myers (1950) for Laemolyta   was observed in all of the species listed above, except for L. fasciata   , L. borellii   and L. laticeps   .

Laemolyta fasciata   was described by Pearson (1924) based on two immature specimens (20 mm SL) from Bolivia with the taxonomic position of the species becoming very confused when Ahl (1937) shifted the species to Anostomus   . Ahl reported that Laemolyta fasciata   possessed the characteristics of Anostomus (Schizodontopsis) Garman, 1890   as a con- sequence of the fact that he did not recognize Garman’s subgenera. Since Anostomus fasciatus   was already preoccupied in Anostomus (Spix & Agassiz, 1829)   , Ahl renamed the species described by Pearson as Anostomus pearsoni   . Myers (1950) did not recognize Ahl’s combination as valid, because according that author the name fasciatus   was not occupied in Laemolyta   .

The type material of Laemolyta fasciata   was not examined during this study but all measurements and counts on that specimen were taken by Anostomoides Mônica   Toledo- Piza (DZ-IBUSP) and the digitalized picture and radiograph of the specimen were provided by David Catania (CAS). This information was insufficient to permit a definitive identification because the specimen is a juvenile (15.7 mm SL) in very poor condition. According to H. A. Britski (MZUSP) (pers. commun.) the general characteristics of the specimen, in particular its color pattern suggest that this specimen might belong to a species of Leporinus   . Böhlke (1958) discussed this question and if this is true, the valid combination would become Leporinus pearsoni ( Ahl, 1937)   , which would be a homonym of Leporinus pearsoni Fowler, 1940   . The problem about the correct name for the species in question can only be resolved after a more detailed study.

Laemolyta borellii (Boulenger, 1900)   included by Fowler (1950) in that genus, has teeth with five or six cusps of about the same size on both jaws, a characteristic of the genus Schizodon   according to Garavello & Britski (1990) and Garavello (1994).

Laemolyta laticeps   cited by Borodin (1931) and Myers (1950) belongs to Anostomoides Pellegrin, 1908   , as suggested by Géry (1974: 149, in footnote). Géry examined the type and mentioned that it was very similar to Anostomoides atrianalis   . One of us (KCM) examined the holotype of Schizodontopsis laticeps Eigenmann, 1912   and confirmed that it is not a species of Laemolyta   . The lower jaw teeth of the specimen have rounded upper margins and the symphyseal tooth is considerably more developed than the second tooth, both of which are characteristic of Anostomoides   .

According to Géry (1977) the genus Anostomus   is composed of two groups that could be considered distinct genera or subgenera: Anostomus (Laemolyta)   and Anostomus (Anostomus)   . The Laemolyta   group is distinct in having the mouth opening slightly less upturned (not quite aligned with the dorsal surface of the snout), and in having multicuspidate teeth on the premaxilla and truncate teeth on the dentary. Géry also emphasized the great similarity between the dentition of young specimens of Laemolyta   and Anostomus   and the manner in which they orient in the water column with the head downturned.

In young specimens of Laemolyta   the premaxillary teeth are very similar to those of adult specimens of Anostomus   , and it was probably for this reason that Géry considered Laemolyta   to be a sub-genus of Anostomus   . The supra-terminal mouth is not useful to distinguish young specimens of Laemolyta   from some other anostomids. According to H. A. Britski (MZUSP) (pers. commun.) young specimens of some Leporinus species   have such a form of the mouth. According to Winterbottom’s (1980) phylogenetic analysis of the members of the subfamily Anostominae   the inclusion of Laemolyta   in Anostomus   is not justifiable since Anostomus   is a monophyletic group within the subfamily, with Laemolyta   proposed as the possible sister-group to the Anostominae   .

Specimens over 40 mm SL can be identified as members of Laemolyta   by the presence of crenate teeth on the upper jaw and the possession of compressed teeth with a straight apical margin. In specimens smaller than 40 mm SL the teeth both on the upper and lower jaws are cuspidate which makes identification to the generic level based on dentition very difficult.

Key to the species of Laemolyta  

1. Four or five longitudinal series of scales above lateral line; well defined midlateral dark stripe always present on body; transverse dark bars absent; dark spot on caudal peduncle absent ................................................................... 2

1’. Six to eight longitudinal series of scales above lateral line; midlateral dark stripe, conspicuous or not; transverse dark bars or blotches, well defined or inconspicuous; peduncular dark spot present or absent .......................... 3

2. Five longitudinal series of scales above lateral line and four or five below it; 42–46 lateral line scales ....................... ............................................................... Laemolyta taeniata  

2’. Four longitudinal series of scales above and below lateral line; 40–44 lateral line scales ............ Laemolyta garmani  

3. 43 to 47 lateral line scales; 16 scales around caudal peduncle .................................................. Laemolyta proxima  

3’. 47 to 58 lateral line scales; 16–20 scales around caudal peduncle ............................................................................... 4

4. Midlateral dark stripe usually conspicuous; transverse dark bars very inconspicuous; dark spot absent on caudal peduncle; 6 longitudinal series of scales below lateral line; 47 to 52 lateral line scales; body depth 0.21–0.25 of SL ....................................................... Laemolyta orinocensis  

4’. Midlateral dark stripe sometimes inconspicuous; four transverse dark bars or blotches present; dark spot usually present on caudal peduncle; 5–7 longitudinal series of scales below lateral line; 49 to 58 lateral line scales; body depth 0.23–0.32 of SL ....................... Laemolyta fernandezi  

Kingdom

Animalia

Phylum

Chordata

Class

Actinopterygii

Order

Characiformes

Family

Anostomidae

Loc

Laemolyta Cope, 1872

Mautari, Kelly Cristina & Menezes, Naércio Aquino 2006
2006
Loc

Schizodontopsis

Eschmeyer, W 1998: 2121
Eigenmann, C 1910: 425
1910
Loc

Laemolyta

Eschmeyer, W 1998: 1986
Cope, E 1872: 258
1872