Physogaleus undetermined
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publication ID |
https://doi.org/ 10.5070/P9361043964 |
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publication LSID |
lsid:zoobank.org:pub:3F95876E-933FF-48AF-9CF0-A840A333220B |
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persistent identifier |
https://treatment.plazi.org/id/03E787A6-FE23-FF8D-AA8C-FF2CFE71FE5D |
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treatment provided by |
Felipe |
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scientific name |
Physogaleus undetermined |
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PHYSOGALEUS SP. AFF. PH. LATUS (STORMS, 1894)
( FIG. 3A–D View Figure 3 )
Referred specimens —SC96.97.26, anterior tooth; SC96.97.27, lateral tooth; SC96.97.28, lateral tooth; SC96.97.29, 18 incomplete teeth; SC2001.1.51, anterior tooth; SC2001.1.52, lateral tooth; SC2001.1.53, posterior tooth; SC2001.1.54, five incomplete teeth; SC2013.38.56, lateral tooth; SC2013.38.57, anterior tooth; SC2013.38.58, lateral tooth; SC2013.38.59, tooth; SC2013.38.60, six incomplete teeth.
Remarks —Dignathic heterodonty is evident among the 39 Dry Branch specimens, with upper teeth having a broader central cusp and better developed serrations on the lateral shoulders ( Fig. 3A, B View Figure 3 ) compared to lower teeth. Lower teeth have a very narrow, sigmoidal cusp and significantly thickened root ( Fig. 3C, D View Figure 3 ). The Physogaleus teeth are similar in gross morphology to those of Galeocerdo , but they are smaller in overall size and development of serrations (especially on the mesial edge) is much reduced. For example, only the basal half of the mesial cutting edge of Physogaleus teeth is serrated, whereas the apical half is smooth. This phenomenon can be discerned even on teeth lacking enameloid, as the dentine core preserves small denticulation basally, but the edge is smooth apically.
Several of the species that White (1926) described from the Eocene of Nigeria, including Eugaleus falconeri , Sphyrna itoriensis, Sph. tortilis, and Carcharhinus nigeriensis , have been placed within Physogaleus ( Cappetta, 2006) , but it is as yet unclear if the morphologies represent multiple species or heterodonty within a single species (monognathic, dignathic, and gynandric heterodonty). The teeth we tentatively identify as Ph. latus compare favorably to teeth described by Storms (1894) from the lower Oligocene of Belgium, and several of the Dry Branch teeth (i.e., Fig. 3A, B View Figure 3 ) are practically identical to the specimen he illustrates in plate 6, figure 17c. These particular teeth differ from other Eocene and Oligocene species of Physogaleus in that the cusp is broad with biconvex cutting edges, and the cusp is well differentiated from the coarsely serrated distal heel and basal half of the mesial cutting edge (Winkler 1876, Reinecke and others 2005, Haye et al. 2008, Reinecke et al. 2008). Teeth that we identify as being from anterior files (i.e., Fig. 3C, D View Figure 3 ) are comparable to the specimen illustrated by Storms (1894; pl. 6, fig. 18).
Case (1981) named Galeorhinus huberensis (= Ph. huberensis ) from the Dry Branch Formation of Georgia, and we consider that taxon to be conspecific with Phy. secundus (Winkler, 1876) as reported by Parmley and Cicimurri (2003) from the Clinchfield Formation of central Georgia. The South Carolina Dry Branch taxon appears to differ from the Georgia material in that the teeth can attain larger size, the cusp is wider, distal serrations are smaller and more numerous, and the mesial serrations may be larger or more numerous.
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