Shark Tooth

[MikaelS]

Interesting discussion.

Squalicorax falcatus is in my opinion an extremely poorly defined species. The species is based on a tooth, presumably of Turonian age, from Lewes, UK. Very few people have ever examined the lectotype first hand (probably only me, David Ward and Charlie Underwood over the last 20-odd years) but many have nonetheless a firm view on the species concept, which is quite remarkable.

The original outline of the root is not preserved intact in the lectotype. It is, however, closer in morphology to species of S. lindstromi-type than it is to species of S. hartwellii-type. Quoting various authors view on S. falcatus as support is meaningless if these individuals have never examined the type specimen first hand.

When a lectotype is selected from a group of syntypes (this was done by Glikman for S. falcatus), it takes over the role as the sole name-bearing type. The other former syntypes become paralectotypes and as such they are no longer name-bearing. In other words, their morphology is no longer relevant to the species concept. All that matters is the morphology of the lectotype.

Squalicorax volgensis is also rather poorly defined (but not anywhere near as badly as S. falcatus). I illustrated two teeth of the former in the 2007 paper. Both specimens came from the type stratum near Saratov. I have a large collection of topotypic material of this species sitting on my desk. The main problem with Cenomanian material from the Russion platform is the generally poor state of preservation. This makes it difficult to diagnose Palaeoanacorax as this nominal genus is based on 'P'. volgensis.

Edited May 3, 2013 by MSiversson

[missingdigits]

Thanks for the discussion everyone. Since this thread has been revived here's another find from last week that I cannot i.d. found in the same formation.