The earliest discovery of a sawskate

Sclerorhynchus & Propristiphorus comparison

The “sawfish horn” figured by Guettard (1783) (top), compared with rostral denticles from Sclerorhynchus atavus (middle) and Propristiophorus tumidens (bottom) from Cappetta (1980a;b).

In 1783, French naturalist Jean-Étienne Guettard briefly described fossil fishes from Lebanon in the collection of the Duke of Orleans, Louis Philippe I (Guettard, 1783). Guettard stated that they were found on “Mont-Liban” (Mount Lebanon) between “Baruth” (Beyrouth/Beirut) and “Gibel” (Jbeil/Byblos). This narrows down the locality to Sahel Alma, which dates to the Santonian stage of the Late Cretaceous (Gayet et al., 2003/2012). The most intriguing of these specimens is one identified as the “corne” (horn) of a “poisson scie” (sawfish). Based on Guettard’s illustration, it is clearly the saw-like rostrum of a chondrichthyan. However, it is too old to be a sawfish, which did not appear until the Eocene (Cappetta, 2012). Additionally, the bases of the rostral denticles are attached to the edges of the rostrum, rather than being embedded in sockets as in sawfishes (Byler, 2017). 

There are only two candidates known from Sahel Alma: the sawshark Propristiophorus (or Pristiophorus) tumidens and the sawskate Sclerorhynchus atavus (Cappetta, 1980a;b). Both have the same type of rostral denticle attachment as Guettard’s specimen. The crenulated bases and more curved crown edges are characteristic of Sclerorhynchus, compared to the smooth bases and straighter crown edges of Propristiophorus. The crowns are roughly the same height as the bases like Sclerorhynchus, rather than the crowns being significantly taller than the bases like Propristiophorus. Based on these features, I think Guettard’s specimen was a Sclerorhynchus atavus rostrum, which would make it the earliest recorded discovery of a sawskate. The next oldest was a Sclerorhynchus (=”Ganopristis“) leptodon rostral denticle found in Maastricht, The Netherlands and documented in 1801 (Faujas de Saint-Fond, 1799-1803; Brignon, 2015). 

References

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