North American material

As noted above, the Paragaleus record in North America is very poor and sometimes questionable. Having collected and studied both reported sediments, a few comments might be appropriate. These observations are based on the published determinations, not an examination of the original source material.

Castle Hayne Formation (Middle Eocene, NC)
Case & Borodin (2000) is perplexing in that the figured holotype (pl 6, fig 53) and paratypes (pl 4, fig 34 and pl 6, fig 52) for Paragaleus duplinensis appear to represent a tooth-design normally ascribed to Physogaleus. Similar tooth-designs are included herein (fig. , & ) to illustrate this observation. As a side note but very relevant: if the plate captions are to be believed, one of the Case & Borodin paratypes (fig. 34) is twice as large as the other teeth (fig 52 & 54); this is much larger than might be expected in Paragaleus.

With that said, their paper does include Paragaleus-like crown-designs (pl 6, fig 58-60) which are identified as Galeorhinus galeus. A similarly-designed tooth is included below (fig ); as can be seen, the labial crown base extends beyond the root and lacks folds. In addition, there are serrations on the mesial cutting-edge, a characteristic not associated with Galeorhinus. However, the strength of the mesial serrations is problematic giving these teeth a Galeocerdo-like tooth-design. Although large Galeocerdo (eaglesomei/latidens) are known from the fauna, there is a lack of ontogenetically transitional tooth-designs between these small teeth and the adult Galeocerdo specimens. The few available small "Paragaleus-like" teeth reflect no characteristics that cannot be attributed to a possible ontogenetic variability of Galeocerdo. Bill Heim (pers com Apr 2007) and I discussed this matter at length without arriving at a consensus -- a definite tooth-positional design is still required.

These specimens appear to display primitive hemigaleid characteristics and considering that Compagno (1988: 397) deemed Paragaleus as such, it would seem to be appropriate to consider the possibility of these teeth as Paragaleus based on lateral tooth-design; however additional tooth-positions are required to confidently determine if they represent Paragaleus, juvenile Galeocerdo or some other carcharhinid.

Pungo River Formation (Lower-Middle Miocene, NC)
The teeth as depicted by Purdy et al (2001: 141-42) appear to lack certain features normally associated with hemigaleids; most importantly, the root is rather thick, the distal cusplets look more like a serrate shoulder rather than running up the distal edge, the crown fails to crisply overhang the root and the tooth is rather large. Rather than Paragaleus, these tooth-designs are more reminiscent of the recent taxon, Carcharhinus sealei. In the extant species, the mesial edge is serrate over a greater distance then these Lower Miocene specimens; however general tooth-design favors a sealei-like lineage for these teeth.

With that said, the Smithsonian collection includes a specimen which is arguably more Paragaleus-like in design. USNM 475447 (fig. ) has a much more labio-lingually compressed root, displays a crisper labial overhang and is sized in the range that might be expected for Paragaleus. The overall crown shape fits into the sealei design-envelope, but root characteristics are more reminiscent of a hemigaleid. The elasmo.com perspective is that convergent crown-designs may be masking the presence of two taxa, Paragaleus (scarce) and an early C. sealei-like species (uncommon).

Acknowledgements

Multiple perspectives, expertises and scarce specimens were required for this short webpage. Richard Chandler, Joy Herrington, Eric Sadorf and David Sanderson were kind enough to open their collections to the project, while Pat Young assisted in the imaging of specimens. Mark Harris opened his dentition collection and assisted in the definition of recent Paragaleus dentition-design; Bill Heim and Fabrice Moreau lent their knowledge of fossil carcharhinids.

Selected References