Isurus (Cosmopolitodus) Hastalis, Xiphodon And Escheri

[sixgill pete]

OK, I remember seeing a thread on here in the not to distant past about a change in name of the I.(C.) hastalis. I have not been able to find it, it may have been part of the thread, not the subject of it. Seems like I remember them having been assigned to Carcharodon.

My question is several fold.

First, the escheri the serrated version of the extinct giant "mako" what would be the proper name for these teeth now. I have 3 that I received in trade with another member from the Netherlands, they are beautiful teeth, but I want to label them properly.

Second, is there a recognized difference in hastalis (or whatever it is called now) and xiphodon, or is this an unrecognized name. It is used by some people I know for the very broad form of the hastalis teeth. Most I have seen came out of the Lee Creek mine, I have a few in my collection.

Third, what is the most current proper name for these teeth and are they truly considered mako's.

My escheri's

[siteseer]

Sixgill,

I thnk you have been looking for this thread:

http://www.thefossil...from-megashark/

The new article is:

Ehret, D.J., B.J. MacFadden, D.S. Jones, T.J. DeVries, D.A. Foster, and R. Salas-Gismondi. 2012.

Origin of the White Shark Carcharodon (Lamniformes: Lamnidae) based on recalibration of the Upper Neogene Pisco Formation of Peru. Palaeontology. 55(6): 1139-1153.

For me the question for escheri is what is the age of the bed they come from. I have read that the teeth are found in the Middle to Late Miocene of western Europe but a formation is not provided nor a stage/age. However, escheri has been considered an early serrated offshoot of hastalis that dead-ended in the Miocene (never spread from the eastern Atlantic). With the reassessment of the age of the Pisco sediments in which the transitional great whites are found, I wonder if escheri is connected. I have seen few escheri in person and was even under the impression that they may have been an offshoot of Isurus oxyrinchus. Someone or some institution with a collection of a number of escheri and transitional great whites from California, Peru, and Chile would have more to say and I assume this may be addressed in the Ehret et al article.

The name xiphodon is a nomen dubium, an invalid name. Some researchers have used it but Ward and Bonavia (2001), citing Leriche (1926: 399) pointed out that the origin of type specimens for xiphodon is not known and cannot be deduced with any certainty. Furthermore, the types are lost. On top of that, the name had not been in usage for many decades. Any one of those conditions is grounds for being declared an invalid name leaving xiphodon a three-time loser.

I still have not obtained a copy of the Ehret article but might have it in a few days. Over the past few years, researchers have used Cosmopolitodus for hastalis. Carcharodon actually has priority over it but there seemed to be a consensus that hastalis was the direct ancestor of the great white yet deserved a separate genus. It's a defensible argument if you don't mind an extra genus here and there when a genus already in use could also include it.

If hastalis is the direct ancestor of the great white with the primary distinguishing character being the presence of serrations, then it would seem that both should be assigned to the same genus - the oldest published name that follows the rules of nomenclature as determined by the ICZN. That would have to be Carcharodon as I understand it. After all, serrations are seen in the teeth of at least one species of Sphyrna that does not always exhibit them and yet those teeth are not placed in a separate genus. Serrated teeth of Carcharoides are referred to a separate species - not a separate genus.

I'm not sure if hastalis and therefore C. carcharias are technically makos - highly derived forms if so. They would not be closely-related to Isurus oxyrinchus in that one did not diverge from the other as I understand it. Mako origins are murky. I think it is possible that hastalis and the Isurus lineage were connected in the Oligocene or earlier (branches from praecursor, or if americanus is a separate species, maybe hastalis came from one and makos from the other?).

Jess

Edit: I neglected to fill out the cited references. Here they are:

Leriche, M. 1926.

Les poissons neogene de la Belgique. Memoires du Musee Royal d'Histoire naturelle de Belgique. 32. 369-472.

Ward, D.J. and C.G. Bonavia. 2001.

Additions to, and a review of, the Miocene shark and ray fauna of Malta. The Central Mediterranean Naturalist. 3(3): 131-146. December 2001.

OK, I remember seeing a thread on here in the not to distant past about a change in name of the I.(C.) hastalis. I have not been able to find it, it may have been part of the thread, not the subject of it. Seems like I remember them having been assigned to Carcharodon.

My question is several fold.

First, the escheri the serrated version of the extinct giant "mako" what would be the proper name for these teeth now. I have 3 that I received in trade with another member from the Netherlands, they are beautiful teeth, but I want to label them properly.

Second, is there a recognized difference in hastalis (or whatever it is called now) and xiphodon, or is this an unrecognized name. It is used by some people I know for the very broad form of the hastalis teeth. Most I have seen came out of the Lee Creek mine, I have a few in my collection.

Third, what is the most current proper name for these teeth and are they truly considered mako's.

My escheri's

Edited January 10, 2013 by siteseer

[cfin1974]

Some want the genus renamed Cosmopolitodus and say that Isurus Hastalis became Escheri which then turned into Carcharodon Carcharias So, they would all be Cosmopolitodus... Then you throw in the C. Hubbelli which co-existed with Escheri but was more serrated and led to C.Carcharias..some say these 2 interbred or were just a regional variation. It would be awesome to go back and see a great white look-alike with 2 different teeth in it's mouth..also more interesting than the whole Megalodon question to me. Xiphodon supposedly co-existed with Hastalis but I believe disappered before Hastalis did. As for a true Mako what makes a Mako a Mako..I'm thinking Great White is Great White and narrow form is a true Mako.. One thing for certain, they'll both eat u.............. I think this is a hot topic.. Look at elasmo.com and I haver googled great white anscestry and otodus.. very interesting... Did Otodus lead to Megalodoon or to Mako line.

[cfin1974]

By the way those are awesome teeth with larger cusps than I usually see.. I'll be preoccupied for days thinking about those...lucky guy

[Paleoc]

Sixgill,

I thnk you have been looking for this thread:

http://www.thefossil...from-megashark/ make sure to continue through the slides with a drop down in the upper right corner.

The new article is:

Ehret, D.J., B.J. MacFadden, D.S. Jones, T.J. DeVries, D.A. Foster, and R. Salas-Gismondi. 2012.

Origin of the White Shark Carcharodon (Lamniformes: Lamnidae) based on recalibration of the Upper Neogene Pisco Formation of Peru. Palaeontology. 55(6): 1139-1153.

For me the question for escheri is what is the age of the bed they come from. I have read that the teeth are found in the Middle to Late Miocene of western Europe but a formation is not provided nor a stage/age. However, escheri has been considered an early serrated offshoot of hastalis that dead-ended in the Miocene (never spread from the eastern Atlantic). With the reassessment of the age of the Pisco sediments in which the transitional great whites are found, I wonder if escheri is connected. I have seen few escheri in person and was even under the impression that they may have been an offshoot of Isurus oxyrinchus. Someone or some institution with a collection of a number of escheri and transitional great whites from California, Peru, and Chile would have more to say and I assume this may be addressed in the Ehret et al article.

The name xiphodon is a nomen dubium, an invalid name. Some researchers have used it but Ward and Bonavia (2001), citing Leriche (1926) pointed out that the origin of type specimens for xiphodon is not known and cannot be deduced with any certainty. Furthermore, the types are lost. On top of the name had not been in usage for many decades. Any one of those conditions is grounds for being declared an invaid name leaving xiphodon a three-time loser.

I still have not obtained a copy of the Ehret article but might have it in a few days. Over the past few years, researchers have used Cosmopolitodus for hastalis. Carcharodon actually has priority over it but there seemed to be a consensus that hastalis was the direct ancestor of the great white yet deserved a separate genus. It's a defensible argument if you don't mind an extra genus here and there when a genus already in use could also include it.

If hastalis is the direct ancestor of the great white with the primary distinguishing character being the presence of serrations, then it would seem that both should be assigned to the same genus - the oldest published name that follows the rules of nomenclature as determined by the ICZN. That would have to be Carcharodon as I understand it. After all, serrations are seen in the teeth of at least one species of Sphyrna that does not always exhibit them and yet those teeth are not placed in a separate genus. Serrated teeth of Carcharoides are referred to a separate species - not a separate genus.

I'm not sure if hastalis and therefore C. carcharias are technically makos - highly derived forms if so. They would not be closely-related to Isurus oxyrinchus in that one did not diverge from the other as I understand it. Mako origins are murky. I think it is possible that hastalis and the Isurus lineage were connected in the Oligocene or earlier (branches from praecursor, or if americanus is a separate species, maybe hastalis came from one and makos from the other?).

Jess

See: http://www.elasmo.co...gw_evo.html?gwa

I. escheri has some characteristics of a narrow form hastalis and some of I. oxyrinchus and is therefore a separate species not involved in the Carcharodon lineage.

Having collected many specimens of mako in the middle Eocene of South Carolina, one can see the animal already begun branching into separate lineages.

See: http://www.elasmo.co...genera-alt.html

One lineage clearly has a hastalis like bent and another an oxyrinchus like bent. In addition, I came across 2 specimens (unfortunately incomplete) that indicated a paucus like bent.

Edited January 9, 2013 by Paleoc

[siteseer]

Paleoc,

Thanks for the insight into escheri and the Eocene mako. It's interesting that you found paucus-like Eocene specimens.

Jess

.

See: http://www.elasmo.co...gw_evo.html?gwa

I. escheri has some characteristics of a narrow form hastalis and some of I. oxyrinchus and is therefore a separate species not involved in the Carcharodon lineage.

Having collected many specimens of mako in the middle Eocene of South Carolina, one can see the animal already begun branching into separate lineages.

See: http://www.elasmo.co...genera-alt.html

One lineage clearly has a hastalis like bent and another an oxyrinchus like bent. In addition, I came across 2 specimens (unfortunately incomplete) that indicated a paucus like bent.

[Boesse]

According to Ehret et al., they regard Isurus escheri as closer to I. oxyrhinchus than to Carcharodon hastalis; it is an earlier offshoot, and they regard the serrations as too small to be homologous with those in the Carcharodon lineage.

Isurus xiphodon is a problematic taxon and was used by Purdy et al. 2001 as broad toothed makos; however, Ehret et al. and others consider this a case of oversplitting, and narrow and broad forms of C. hastalis simply representing morphological extremes within a species (it was also a bit of an underhanded straw man argument for Purdy et al., since they identified I. xiphodon as the form that others hypothesized evolved into C. carcharias, and subsequently reasoned for reasons that escape me that the two could not have shared an evolutionary relationship, thereby disproving the hypothesis).

Lastly... no, Carcharodon hubbelli and Isurus eschri do not co-occur. It goes Carcharodon hastalis-->C. hubbelli--->C. carcharias

Hey Siteseer... what's your email address?

[Al Dente]

I recently had the opportunity (briefly) to look at Cappetta's new Handbook of Paleoichthyology. I took a few notes and his comments on escheri were that it has features that separate it from Carcharodon and Cosmopolitodus. I don't believe he offers a genus for them. In his photos he uses quotes and gives the name "Carcharodon" escheri.

There are a lot of interesting changes in this book. He lowers the genera Carcharocles and Megaselachus to sub-genera under Otodus, so now megalodon is Otodus (Megaselachus) megalodon. Another interesting change is Isurus retroflexus is now considered a type of thresher shark and is placed in the genus Anotodus in the family Alopiidae.

[Gizmo]

There are Escheri teeth in Zones 23-24 of the St. Mary's formation /Chesapeake group in Maryland.

[cowsharks]

There are Escheri teeth in Zones 23-24 of the St. Mary's formation /Chesapeake group in Maryland.

Gizmo, I think I saw your Escheri at one of the club meetings - you got a pic to post?

Daryl.

[sixgill pete]

Thanks or all of the replies everyone. Jess, that was the thread I was looking for. This topic is very interesting to me, from my very amateur point of view. I like to keep my very best items, those in individual displays, labelled correctly and current. At this point, I would say it would be not incorrect to relabel I. hastalis as C. hastalis. Also to keep the escheri as I. escheri.

Al Dente, very interesting about the I. retroflexus.

[Paleoc]

According to Ehret et al., they regard Isurus escheri as closer to I. oxyrhinchus than to Carcharodon hastalis; it is an earlier offshoot, and they regard the serrations as too small to be homologous with those in the Carcharodon lineage.

Isurus xiphodon is a problematic taxon and was used by Purdy et al. 2001 as broad toothed makos; however, Ehret et al. and others consider this a case of oversplitting, and narrow and broad forms of C. hastalis simply representing morphological extremes within a species (it was also a bit of an underhanded straw man argument for Purdy et al., since they identified I. xiphodon as the form that others hypothesized evolved into C. carcharias, and subsequently reasoned for reasons that escape me that the two could not have shared an evolutionary relationship, thereby disproving the hypothesis).

Lastly... no, Carcharodon hubbelli and Isurus eschri do not co-occur. It goes Carcharodon hastalis-->C. hubbelli--->C. carcharias

Hey Siteseer... what's your email address?

I understand about I. xiphodon being nomen dubium and the weird reasoning behind it. However having collected extensively in both Miocene and Pliocene deposits, I find there is a definite shift in morphology in "hastalis". In the east coast Miocene you most commonly find the thick narrow form hastalis. The laterals having a distinct D-shaped cross section with the occasional broad, flattened form thrown in. In the west coast Miocene, the flattened wide-form predominates. In the Pliocene, all the D-shaped teeth are gone and only the flattened broad form are left. So to me there should be a species separation there. If not xiphodon, then something else perhaps.

Miocene thick form hastalis, note this tooth position still exists in Pliocene specimens but is greatly flattened.

[MikeDOTB]

Very informative thread. I only had one comment on your escheri you posted a picture of Sixgill, but I love the cusps on that tooth! Pretty uncommon for makos!

[Boesse]

And that's totally fine that people think that two forms exist. But many of us feel that it's too nitpicky to call without large sample sizes and rigorous statistical analyses. Whitenack and Gottfried did such an analysis, and supported distinction of C. xiphodon - however, I haven't read the paper in a long while and can't comment on the specifics, but such an analysis ought to separate such an analysis into time bins to test whether there is change through time as well.

Ehret et al. also pointed out that if two distinct groups of teeth were real, then it could also be explained by sexual dimorphism or ontogenetic changes. Either way, xiphodon doesn't have a holotype specimen and its taxonomic 'founding' is ill and should not be used.

Bobby

[cfin1974]

thanks guys this is very informative

[Paleoc]

And that's totally fine that people think that two forms exist. But many of us feel that it's too nitpicky to call without large sample sizes and rigorous statistical analyses. Whitenack and Gottfried did such an analysis, and supported distinction of C. xiphodon - however, I haven't read the paper in a long while and can't comment on the specifics, but such an analysis ought to separate such an analysis into time bins to test whether there is change through time as well.

Ehret et al. also pointed out that if two distinct groups of teeth were real, then it could also be explained by sexual dimorphism or ontogenetic changes. Either way, xiphodon doesn't have a holotype specimen and its taxonomic 'founding' is ill and should not be used.

Bobby

I agree with your comments as to xiphodon. Unfortunately, currently the only way to separate them is calling them thin type or thick type which is not much of an improvement. As to sexual dimorphism, Carcharodon shows no such dimorphism nor does thin west coast and/or Pliocene "xiphodon"/hastalis which I think pretty much rules that out. As to ontogenetic, as you can see in the images I provided, that is a 52mm specimen which is a full grown adult nor is it by far the largest I have collected, so that is ruled out as well. The same distinction (thin or thick) is found in the entire range of specimens from juvenile to adult.

[RichW9090]

Siteseer said "If hastalis is the direct ancestor of the great white with the primary distinguishing character being the presence of serrations, then it would seem that both should be assigned to the same genus"

if we have a compelte lineage with every ancestor-descendant species represented, then the transition of one genus to another will also be the transition from one ancestral species to its direct descendant species. The division between ancestor/descendant species in practical terms usually depends on gaps in the fossil record - without those gaps, one could not determine when a new genus begins without being completeldy arbitrary - how many apomorphies have to accululate before Genus A becomes Genus B? Gaps allow several apomorphies to accumulate, so that A and B are different enough that they are "obviously" different general.

One hesitates to consider the loss of serrations as an apomorphy, especially since the presence or absence of serrations, and their size, seems variable among the sharks, and serrations come and go without much pattern across many lineages. If Hastalis was unserrated, and the modern greta white serrated, I'd be more comfortable with it being an apomorphy.

But I'm not a shark guy, and really don't know much about them, so take it all with a grain of salt.

Rich

Edited January 11, 2013 by RichW9090

[siteseer]

Some notes:

On one hand it would seem that distinguishing a species from another because it is broader and/or thinner would be an oversplitting situation. On the other hand, it is a common observation that east coast Middle Miocene hastalis teeth are noticeably narrower in general than those of the west coast Middle MIocene.

It is my understanding that the hastalis teeth found in the Pungo River Formation come from beds ranging around 17-18 million years old and that the most productive hastalis-producing beds of the Calvert also range a few million years older than the STH Bonebed (approx. 15.5 million years old) but the Calvert also ranges younger. I don't know if hastalis teeth are found in them too or if they are just a lot less common.

One interesting observation about west coast hastalis is that it "suddenly" appears in the STH bonebed with no reported occurrences lower in the Round Mountain Silt (the formation that contains the STH Bonebed) nor in older formations in California. The planus species also appears in the STH Bonebed with no known earlier occurrences in California. It's not that there are no shark-tooth bearing beds. The Lower Round Mountain Silt, Olcese Sand, and Jewett Sand (formations exposed in Kern County) bear mako teeth but they are all of Isurus desori (or early oxyrinchus form).

An intriguing occurrence of teeth that appear to be narrow-form hastalis is in the Early Miocene of northern Mexico (see Espinosa-Arrubarrena, 1987) at a site given as Hemingfordian (16-19 million years ago). Even more intriguing is Espinosa-Arrubarrena's report of Late Oligocene teeth that appear to be a broader, flatter hastalis form - teeth from a fauna that had been studied preliminarily by Shelton Applegate. Perhaps hastalis evolved in the tropics and spread north along the west and east coasts of North America - earlier and farther north along the east coast for some reason(s) with the narrow form predominating for some reason(s). During the Miocene and into the Pliocene there was a seaway through what is now Central America allowing a free exchange of marine organisms between the Pacific and Atlantic Oceans.

Years ago, a friend expressed surprise when I told him of a recently-published article on the age of the STH Bonebed - how it had been pushed back a little further into the Middle Miocene. He thought it would have been reset younger because the hastalis teeth didn't fit the age. He had collected at Lee Creek and was used to seeing the broader teeth from the Early Pliocene Yorktown Formation.

Perhaps the narrow and broad-form hastalis could be distinguished at the subspecies level with both being considered regional variants. Clearly, some shark researchers have considered it to be a justified separation at the species level. Kent (1994: p.60) stated that he was studying the situation but I haven't heard if he has come to any conclusions.

Espinosa-Arrubarrena, L. 1987.

Neogene Species of the genus Isurus (Elasmobranchii, Lamnidae) in southern California, U.S.A and Baja California Sur, Mexico. M.S. thesis. California State University, Long Beach, CA.

Kent, B.W. 1994.

Fossil Sharks of the Chesapeake Bay Region. Egan Rees & Boyer, Inc.

I understand about I. xiphodon being nomen dubium and the weird reasoning behind it. However having collected extensively in both Miocene and Pliocene deposits, I find there is a definite shift in morphology in "hastalis". In the east coast Miocene you most commonly find the thick narrow form hastalis. The laterals having a distinct D-shaped cross section with the occasional broad, flattened form thrown in. In the west coast Miocene, the flattened wide-form predominates. In the Pliocene, all the D-shaped teeth are gone and only the flattened broad form are left. So to me there should be a species separation there. If not xiphodon, then something else perhaps.

Miocene thick form hastalis, note this tooth position still exists in Pliocene specimens but is greatly flattened.

[cfin1974]

thanks for the great info guys...love this topic