Squalicorax Help

[AlexMcCarthyWX]

North Myrtle Beach has been generous to me over the last decade with all the crow shark teeth it has given me. I am working on organizing my teeth in a case and would like help identifying what specific type of squalicorax teeth each of these are (pristodontus, kaupi, etc.). All of these teeth are from North Myrtle Beach (about 2 miles south of the Cherry Grove Pier for anyone familiar with the area).

[sixgill pete]

1 and 3 pristodontus. 2,4,6,and 7 lindstromi ( was kaupi) and 5 could be either in my opinion, but would go with lindstromi.

Edited July 10, 2016 by sixgill pete

[MikaelS]

1 and 3 are indeed S. pristodontus. The other teeth belong to an undescribed species largely restricted to North America that I hope to have described in the not too distant future. Its younger than topotypic S. lindstromi and much smaller (other differences as well but these are not obvious unless the material is rather pristine). The early Campanian S. lindstromi did most likely give rise to S. pristodontus as the lineage can be traced via intermediate forms in Europe and northern Africa. The nominal S. kaupi could be anything depending on which of the mostly poorly preserved syntypes you base your species concept on.

[Al Dente]

I had assumed some of the smaller teeth were juvenile S. pristodontus. What do juvenile S. pristodontus look like? Are they miniature versions of the adult teeth? If so, I've never seen a juvenile tooth in the Peedee Formation, only the large adult teeth and this undescribed species.

[MikaelS]

Juveniles of the lindstromi-pristodontus lineage are quite similar to those of the undescribed taxon in lingual view and that is about as much information as I can give you without compromising unpublished results. Teeth of superficially similar anacoracids are generally very easy to separate if they have an uncorroded root (which is rarely the case), are properly cleaned (which is likewise rarely the case) and photographed after having been coated with ammonium chloride (which again is rarely the case) (see my 2007 paper on anacoracids from the Albian of Texas).

Size segregation is not uncommon at all in selachians.

Edited July 16, 2016 by MikaelS

[Al Dente]

Juveniles of the lindstromi-pristodontus lineage are quite similar to those of the undescribed taxon in lingual view and that is about as much information as I can give you without compromising unpublished results. Teeth of superficially similar anacoracids are generally very easy to separate if they have an uncorroded root (which is rarely the case), are properly cleaned (which is likewise rarely the case) and photographed after having been coated with ammonium chloride (which again is rarely the case) (see my 2007 paper on anacoracids from the Albian of Texas).Size segregation is not uncommon at all in selachians.

Thank you. I look forward to reading your paper when it comes out.

[siteseer]

I have always gone under the general assumption that juvenile teeth would be very rare where adults are common even extending distantly in the past. Just based on what friends traded to me from NJ or NC, it appeared that there were two species of Squalicorax because they both seemed to be roughly as common (considered pristodontus and kaupi in the old days of the late 80's-early 90's).

I had assumed some of the smaller teeth were juvenile S. pristodontus. What do juvenile S. pristodontus look like? Are they miniature versions of the adult teeth? If so, I've never seen a juvenile tooth in the Peedee Formation, only the large adult teeth and this undescribed species.

Edited July 16, 2016 by siteseer

[MikaelS]

In the lower Smoky Hill Chalk Squalicorax hartwellii (invariably but incorrectly referred to S. falcatus) is represented by most age classes whereas an undescribed smaller-toothed taxon (with poorly serrated cutting edges)is represented by teeth from larger individuals only. In the type area of S. lindstromi (Kristianstad Basin, Sweden) teeth of adults are considerably more common than are those of small juveniles. In the same area juvenile teeth of Cretalamna sarcoportheta are completely absent (teeth of large individuals are common) whereas eg Archaeolamna kopingensis is represented by teeth, ranging from extremely small to very large for a given tooth-position. Highly variable age-distribution within a given palaeoenvironment in other words.

Edited July 17, 2016 by MikaelS