Paramobula fragilis ( Cappetta, 1970 )
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publication ID |
https://doi.org/ 10.4202/app.2008.0077 |
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publication LSID |
lsid:zoobank.org:pub:3D85D369-7A74-44B6-9766-7C4B8B26705B |
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persistent identifier |
https://treatment.plazi.org/id/03A6C023-FF8B-4E10-1E7D-FD9CFCBAFD2F |
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treatment provided by |
Felipe |
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scientific name |
Paramobula fragilis ( Cappetta, 1970 ) |
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Paramobula fragilis ( Cappetta, 1970)
Fig. 6D View Fig .
Referred specimens.—BCGM 9111–9113, SC 2009.18.21.
Comments.—Teeth of Manta fragilis Cappetta, 1970 (based on six isolated teeth) from the French Miocene differ significantly from extant Manta in having: mesio−distally wide, labio−lingually thin, and apico−basally high crowns; smooth, flat, often slightly labially sloping occlusal surfaces; there are numerous very narrow and closely spaced labial vertical ridges and grooves; wider and fewer lingual ridges and grooves; and the root is polyaulacorhize ( Cappetta 1987). These Mobula −like characteristics led Pfeil (1981) to erect a new genus, Paramobula .
Although superficially similar to Plinthicus stenodon Cope, 1869 , Paramobula fragilis is much smaller in size (up to 5 mm in width) and labio−lingually thinner (some Chandler Bridge specimens are partially translucent). Additionally, the occlusal surface of Paramobula is flat and smooth, whereas it is distinctly concave in Plinthicus Cope, 1869 . We do not consider the Paramobula morphology to represent ontogenetic heterodonty in Plinthicus (i.e., juvenile individuals) because the smallest teeth in our Plinthicus sample possess the same characteristics as the largest teeth (see below).
Some of our Mobula teeth are mesio−distally wide like Paramobula , but the crowns are labio−lingually thicker. One characteristic we used to differentiate the two genera is crown height, with the labial face of Mobula teeth measuring 1 mm or less in height, whereas the vertical height of Paramobula teeth is 2 mm to 4.5 mm. These two genera occur together (see Cappetta 1970; Purdy et al. 2001), and admittedly we cannot acertain if they are conspecific. Notabartolo di Sciara (1987) noted that teeth of Mobula become wider as individuals mature, so the Paramobula morphology could represent ontogenetic heterodonty within Mobula . Cappetta and Stringer (2002) stated that Paramobula was synonymous with Mobula but provided no details for their reasoning. Controversies regarding the identification of isolated teeth may not be resolved without the benefit of at least one reasonably complete associated dentition, and for the purposes of this report we consider the morphologies distinct.
The degree of morphological variation in the dentition of Paramobula is inadequately known. Case (1980) assigned a suite of 13 teeth recovered from the Oligocene Trent Marl to a new species, Manta melanyae , based on comparison to the P. fragilis morphology. However, it is our opinion that the specimens illustrated by Case (1980: pl. 10), which were identified as belonging to lateral jaw positions, could be assignable to Mobula (pl. 10: 1) or Paramobula (pl. 10: 2). Müller (1999) but made no mention of Paramobula , and assigned all mobulid teeth from the Oligocene of North Carolina, Virginia, and South Carolina to Mobula sp. Although Case (1980) noted that P. fragilis occurs in Miocene deposits of North Carolina, Purdy et al. (2001) did not mention the taxon, even though one specimen they identified as Mobula sp. (fig. 14j–l) is morphologically similar to P. fragilis .
Stratigraphic and geographic range.—Oligocene (Chattian), USA (South Carolina); Miocene, France and USA (North Carolina).
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