I. paucus could be a junior synonym of C. hastalis?

[Macrophyseter]

I've recently was lucky to have found an online copy of Purdy et al. (2001)'s paper on Lee Creek sharks, and I've found a passage that caught my interest-

 

"In morphology, the teeth lsurus hastalis (Figure 27) are almost identical to those from large individuals (TL=3.7-4.3 m) I. paucus. The tips of the upper anterior teeth of the latter species, however (TL=2.3^1.2 m, n=9), usually lack the labial recurvature that is so well developed in I. hastalis (Figure 28a). In the small number of I. paucus dentitions available to us (n=9), only one dentition (Hubbell collection, JF91980, 2.6 m TL, female) had upper anterior teeth with tips that exhibited a strong labial recurvature. At present, we do not know how common this recurvature is in the extant species. The upper anterior teeth of Leriche's (1910:275-280, figs. 78-86, pi. 16: figs. 16-31) sample of teeth from the Oligocène of Belgium, which he identified as Oxyrhina desori and O. desori flandrica, are identical to those of the extant Isurus paucus. They lack a labial recurvature. This suggests that I. paucus may be a junior synonym of I. hastalis, but because of the small number of dentitions available of I. paucus, we hesitate in synonymizing the two species. "

 

Traditionally, I think people believed that I. paucus evolved from Isurus retroflexus. Capetta (2012) now describes retroflexus in the genus Anotodus as an alopiid with later authors following suit, making it unlikely to have any relation with the longfin mako and making the lineage of paucus unclear. Of the few papers and articles I've read that mention Purdy et al. (2001)'s observation and its possibilities, none give an actual opinion or response to it and simply mention it without anything else, which sort of makes me feel like this observation could be a legitimate possibility.

 

So I really want to know the opinion any of you shark experts and enthusiasts out there on this topic. What do you guys think?

 

 

[FossilsAnonymous]

It would be a lot more interesting if it was.

[Al Dente]

6 hours ago, Macrophyseter said:

I've recently was lucky to have found an online copy of Purdy et al. (2001)'s paper on Lee Creek sharks, and I've found a passage that caught my interest-

 

"In morphology, the teeth lsurus hastalis (Figure 27) are almost identical to those from large individuals (TL=3.7-4.3 m) I. paucus. The tips of the upper anterior teeth of the latter species, however (TL=2.3^1.2 m, n=9), usually lack the labial recurvature that is so well developed in I. hastalis (Figure 28a). In the small number of I. paucus dentitions available to us (n=9), only one dentition (Hubbell collection, JF91980, 2.6 m TL, female) had upper anterior teeth with tips that exhibited a strong labial recurvature. At present, we do not know how common this recurvature is in the extant species. The upper anterior teeth of Leriche's (1910:275-280, figs. 78-86, pi. 16: figs. 16-31) sample of teeth from the Oligocène of Belgium, which he identified as Oxyrhina desori and O. desori flandrica, are identical to those of the extant Isurus paucus. They lack a labial recurvature. This suggests that I. paucus may be a junior synonym of I. hastalis, but because of the small number of dentitions available of I. paucus, we hesitate in synonymizing the two species. "

 

Traditionally, I think people believed that I. paucus evolved from Isurus retroflexus. Capetta (2012) now describes retroflexus in the genus Anotodus as an alopiid with later authors following suit, making it unlikely to have any relation with the longfin mako and making the lineage of paucus unclear. Of the few papers and articles I've read that mention Purdy et al. (2001)'s observation and its possibilities, none give an actual opinion or response to it and simply mention it without anything else, which sort of makes me feel like this observation could be a legitimate possibility.

 

So I really want to know the opinion any of you shark experts and enthusiasts out there on this topic. What do you guys think?

 

 

I don’t follow the logic in the quoted paragraph. In the first sentence he points out that hastalis teeth are curved labially and paucus aren’t. Then he points out that Belgian Oxyrhina are identical to paucus teeth. From this he concludes that paucus is a junior synonym of hastalis. There is something missing here.

 

In this publication he is trying to explain why the modern great white is a descendant of the megalodon. It helps his argument if he can convince his audience that hastalis is a mako and not related to the modern great white.

[siteseer]

On 1/17/2019 at 10:06 PM, Macrophyseter said:

I've recently was lucky to have found an online copy of Purdy et al. (2001)'s paper on Lee Creek sharks, and I've found a passage that caught my interest-

 

"In morphology, the teeth lsurus hastalis (Figure 27) are almost identical to those from large individuals (TL=3.7-4.3 m) I. paucus. The tips of the upper anterior teeth of the latter species, however (TL=2.3^1.2 m, n=9), usually lack the labial recurvature that is so well developed in I. hastalis (Figure 28a). In the small number of I. paucus dentitions available to us (n=9), only one dentition (Hubbell collection, JF91980, 2.6 m TL, female) had upper anterior teeth with tips that exhibited a strong labial recurvature. At present, we do not know how common this recurvature is in the extant species. The upper anterior teeth of Leriche's (1910:275-280, figs. 78-86, pi. 16: figs. 16-31) sample of teeth from the Oligocène of Belgium, which he identified as Oxyrhina desori and O. desori flandrica, are identical to those of the extant Isurus paucus. They lack a labial recurvature. This suggests that I. paucus may be a junior synonym of I. hastalis, but because of the small number of dentitions available of I. paucus, we hesitate in synonymizing the two species. "

 

Traditionally, I think people believed that I. paucus evolved from Isurus retroflexus. Capetta (2012) now describes retroflexus in the genus Anotodus as an alopiid with later authors following suit, making it unlikely to have any relation with the longfin mako and making the lineage of paucus unclear. Of the few papers and articles I've read that mention Purdy et al. (2001)'s observation and its possibilities, none give an actual opinion or response to it and simply mention it without anything else, which sort of makes me feel like this observation could be a legitimate possibility.

 

So I really want to know the opinion any of you shark experts and enthusiasts out there on this topic. What do you guys think?

 

 

 

Ward and Bonavia (2001) commented on various statements in Purdy et al. (2001) within their review of material from Malta.  Regarding I. retroflexus, all they did was list it in the fauna and agree that two of the figures could be referred to the species.

 

I've started reading the recently-published volume on the geology and paleontology of the Calvert Cliffs and invite you to read Dr. Bretton Kent's review of the cartilaginous fishes.  If you don't mind the spoiler, he supports the validity of I. retroflexus with further comments.  Every specimen I've seen identified as I. retroflexus has two distnct characters - a noticeably flattened (labiolingually compressed) crown and what Kent (1994) called an "elevated platform" on the labial face of the root which he referred to as a "pronounced lingual shelf" in the Calvert Cliffs publication.  It's a raised/inflated buffer area between the crown and the main part of the root.  The latter character may not be as pronounced in the anteriors but it isn't hard to see either.  In addition you just don't see a hastalis tooth with the same degree of flatness to the crown.

 

https://www.researchgate.net/publication/280316614_Additions_to_and_a_review_of_the_Miocene_Shark_and_Ray_fauna_of_Malta

 

https://opensi.si.edu/index.php/smithsonian/catalog/book/107

 

 

[verydeadthings]

In this case I think it would be a bad idea to consider I. paucus a junior synonym of C. hastalis. Isurus paucus is a modern species and the species description can be based on the whole shark, while C. hastalis is a form genus for isolated fossil teeth. The original description for C. hastalis by Agassiz (1843) would be totally inadequate as a description for a modern shark species, and my guess is that the original description would include fossil shark teeth from species other than I. paucus. I'm not aware of an english translation of the original description for C. hastalis, but the original description is available in French at (https://www.biodiversitylibrary.org/item/23762#page/293/mode/1up). I wouldn't be surprised if the description is somewhat insufficient by modern standards, and it probably should be emended, if only to clarify the description for English readers.

 

I like the way this kind of thing is handled with fossil pollen, which uses two taxonomic systems, the first using modern botanical names for the whole plant, and the second using fossil names for the isolated pollen. For example, fossil Ephedra pollen is not identifiable to individaul modern species, but fossil pollen species can be described for pollen morphologies representing species groups. So the pollen could either be referred to the modern botanical nomenclature and identified as Ephedra sp., or referred to the individual fossil species Ephedripites eocenipites.