The misidentified “Cretalamna” on Wikimedia Commons

Serratolamna comparison

The reconstruction of Serratolamna by Dmitry Bogdanov from Ceballos-Izquierdo et al. (2021) and the “Cretalamna” fossil it was based on from Wikimedia Commons (Citron/CC BY-SA 3.0).

Ceballos-Izquierdo et al. (2021) described a tooth of the otodontid shark Serratolamna serrata from the Maastrichtian Cantabria Formation of Cuba. In the graphical abstract for the paper, they used a life reconstruction of Serratolamna drawn by Dmitry Bogdanov. Although not stated in the paper, it was clearly based on a photo of a shark body fossil uploaded to Wikimedia Commons by user Citron in 2012. This photo was formerly labelled as “Cretolamna [sic] sp.” and was presumably used by Bogdanov due to the close relationship between Cretalamna and Serratolamna. However, this specimen has been misidentified and is neither a Cretalamna nor an otodontid.

Pteroscyllium comparison 1

Body fossils of Pteroscyllium signeuxi from Cappetta (1980): MNHN 1946-18-1458A (top left), MNHN 1946-18-1458B (bottom left), and MNHN 1946-18-1453 (right).

Instead it is most likely a Pteroscyllium from one of the Late Cretaceous lagerstätten of Lebanon. It matches well with the three body fossils of P. signeuxi from Sahel Alma figured by Cappetta (1980). The head shape and preservation is almost identical to MNHN 1946-18-1458A, while the relative sizes and placements of the pectoral and pelvic fins are similar to MNHN 1946-18-1458B and MNHN 1946-18-1453. It also resembles undescribed specimens of P. sp. from Hakel and Hjoula. I have seen one on display at the Black Hills Institute and another one at the Staatliches Museum für Naturkunde Karlsruhe is figured in Frickhinger (1995). Unfortunately, no photos of the teeth of the Wikimedia specimen are available to confirm its identity, so I tentatively refer it to Pteroscyllium sp.  [see addendum]

Pteroscyllium comparison 2

Body fossils of Pteroscyllium sp. ?odontaspidids [see addendum] at the Black Hills Institute (left) and Staatliches Museum für Naturkunde Karlsruhe (right), from the author and Frickhinger (1995) respectively.

The affinities of Pteroscyllium are currently uncertain and it is debated whether it is a carcharhiniform or a lamniform. Cappetta (1980) originally classified it as a scyliorhinid related to extant catsharks. However, Maisey (1984) suggested that it might be a basal lamniform based on its tooth morphology. It is best placed in its own family, Pteroscylliidae Cappetta, 1992, and considered Galeomorphii incertae sedis for the time being. Whatever the case, Pteroscyllium is definitely not an otodontid and should not be used to reconstruct Cretalamna or Serratolamna. [see addendum]

Special thanks go to Dr. Charlie Underwood who kindly provided me with a copy of Cappetta (1980).

Addendum (11/22/2022)

Hjoula odontaspidids

Body fossils of Odontaspis aculeatus (top, middle) and Odontaspididae indet. (bottom), from Pfeil (2021).

I got ahold of a copy of Pfeil (2021), which has the most recent and comprehensive overview of the Late Cretaceous Lebanese shark fauna. Based on the figures and updated information within, I no longer think the Wikimedia Commons, BHI, or SMNK specimens are Pteroscyllium sp. Instead, I think they are more likely to belong to the family Odontaspididae, the sand tiger sharks. One definite odontaspidid is known from Hjoula, Odontaspis aculeatus, as well as uncertain specimens referred to Odontaspis sp. or Odontaspididae indet. The three specimens in this post are most similar to the odontaspidids in that both dorsal fins are relatively small and roughly the same size, the first dorsal is positioned behind the pectorals (although this is ambiguous in the BHI and SMNK specimens, probably due to distortion), and the pelvic and anal fins are relatively large. This contrasts with actual Cretalamna specimens now known from the same locality, which have an enlarged first dorsal fin positioned above the pectorals and very small second dorsal, pelvic, and anal fins.

References

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