Squalicorax

[readinghiker]

Hey everyone,

 

  I don't have a lot of comparative material at hand, so I am asking for your help.  I am working on a large shark fauna

from the Cabezon area of New Mexico.  The teeth are very beat up, possibly due to wave action on offshore sand bars.

However, upon close inspection of the better teeth I have discovered that the serrations on the lingual side of the teeth

contain indentations (or possible enable folding...see the photo).  I have some squalicorax teeth from the Turonian,

about 25 miles from this site, that were described in the New Mexico Museum of Natural History and Science Bulletin

52 (Bourdon, et. al., I was the tail end author) that also have these features.  The closest we could identify these teeth

were to slap a cf. or an aff. on them.  Those of you who have identified to species squalicorax, could you check and see

if they also have these lingual indentations or folds?  Are these normal on all squalicorax species?

  Thank you!!!

  Randy Pence

[Macrophyseter]

I haven't really seen such indention of that detail before, but I think a rare variation could be a possible explanation considering how tiny it is.

 

 

[The Jersey Devil]

I can't see on the photo what you mean by lingual indentations, but I'd bet it is just a variation on the highly variable Squalicorax genus. Are they the shadow-like things in the pic?

[readinghiker]

4 hours ago, Macrophyseter said:

I haven't really seen such indention of that detail before, but I think a rare variation could be a possible explanation considering how tiny it is.

 

 

The indentations are standard on these teeth (I screened over 1000 teeth and pieces of teeth  from the anthills I collected).  When I went back to look at the Turonian sqalicorax teeth

(two million years difference...still within the parameters of one species) found about 25 miles away, these same indentations are evident.  I will be writing about the second occurrence of Scindocorax novimexicanus, which I also found at this site.  It appears that S. novimexicanus had not changed any from the Coniacian to the Turonian (the Rio Puerto site that was the area in which this genus novem was found), therefore I am wondering about the Squalicorax sp.  If no other squalicorax has this lingual folding, is this a new species?  I am getting ready to describe a new ptychotrygonid from this site.

[Anomotodon]

I doubt that those indentations are characteristical features, I have seen them on some early Squalicorax, such as Coniacian S. aff. falcatus and Turonian S. curvatus. And anyway one feature is not enough to validate assignment to a new species, you have to compare general morphology as well to differentiate from sexual/ontogenetic dimorphism. Can we see pictures of the entire teeth?

By the way, you can find this thread useful, I ended up calling them S. aff. falcatus although it might be a new species. You can find the list of Squalicorax species in Cappetta et al., 2014.

 

[readinghiker]

2 hours ago, The Jersey Devil said:

I can't see on the photo what you mean by lingual indentations, but I'd bet it is just a variation on the highly variable Squalicorax genus. Are they the shadow-like things in the pic?

 

2 hours ago, The Jersey Devil said:

I can't see on the photo what you mean by lingual indentations, but I'd bet it is just a variation on the highly variable Squalicorax genus. Are they the shadow-like things in the pic?

Yes, they are the shadowy indentations on the basal part of each serration.  I have collected over 1000 squalicorax teeth (and pieces of teeth) from this site, and these indentations are a standard feature.  When I looked at the squalicorax from a site about 25 miles away, but from the Turonian, they had the same indentations.  The Turonian squalicorax was not identified as to species, but given a cf. in the literature we published.  Two million years is within the parameters of a single species not having evolved.  So I am wondering if this folding is found in other squalicorax species, or if I am possibly looking at a new species.  I already have a ptychotrygon species that I am proposing as new from this site.  Thanks for your reply!

[The Jersey Devil]

3 hours ago, readinghiker said:

 

Yes, they are the shadowy indentations on the basal part of each serration.  I have collected over 1000 squalicorax teeth (and pieces of teeth) from this site, and these indentations are a standard feature.  When I looked at the squalicorax from a site about 25 miles away, but from the Turonian, they had the same indentations.  The Turonian squalicorax was not identified as to species, but given a cf. in the literature we published.  Two million years is within the parameters of a single species not having evolved.  So I am wondering if this folding is found in other squalicorax species, or if I am possibly looking at a new species.  I already have a ptychotrygon species that I am proposing as new from this site.  Thanks for your reply!

 

Interesting. The New Jersey Squalicorax that I've seen (S. kaupi and S. pristodontus) don't have these lingual serration indentations.

[readinghiker]

To Anomotodon...

 

Thanks for your reply.  I'm going to make this short, as I was finally able to get back to my computer

and it is getting late here in New Mexico.  I am uploading some pictures of near complete teeth.

The preservation, on the whole, is terrible in the faunal representation.  Take a look at them, and I will write

more tomorrow afternoon.  Thanks again!

Randy

[Anomotodon]

Looks like it is a match for my teeth above and S. aff. falcatus from Coniacian of France (P-X; Guinot et al., 2013). You can also see some 'indentations' on the pictures below

 

[readinghiker]

To Anomotodon,

 

  Thanks for your post!  It was helpful.  Cappetta lists 50 qualicorax species, some as novem nudem, some very iffy, while shark references.com list only 23

squalicorax species at being valid.  Going through each one I feel comfortable eliminating the ones that have only been reported from Europe, Africa, or Asia.

I am somewhat less comfortable eliminating those that are outside of the Coniacian time frame, since the upper or lower limits of the geological time of this animal

could very well be extended.  But I am narrowing it down to four possible species...S. curvatus,  S. falcatus, S. lindstromi, and S. yangaensis, all of which can be found in the

Western Interior Seaway (in which New Mexico lies), and within  the acceptable time frame in which my teeth were found.  It is simply a matter of doing more research, especially to see if all four have the lingual indentations.  It could be that the closest I can get is to put an aff. in front of the species, and move on to the next animal.  I've included a couple of more photos.

And you live in Kyiv?  I've thought a lot about the Ukraine lately with all of the political stuff going on there!

Thanks again!

Randy

[Anomotodon]

Honestly with Squalicorax I would use a different approach by considering difference in geographical distribution less important rather than temporary. Variation of Squalicorax species is very high, most species lived for only short periods of time corresponding to the stages of Late Cretaceous (check Glikman, 1980), while for instance S. pristodontus doesn't exhibit a significant variation Late Campanian through Maastrichtian all over the world - US East Coast, Northern Africa, Europe and Western Asia. 

 

Anyway, I think that this type of teeth is highly similar to S. falcatus but with a more gracile morphology (like teeth from my topic above), it might be just a juvenile S. falcatus. Obviously S. sp. would be more accurate, who knows what is going to happen to the attribution and validity of S. falcatus in the future. Often sp. or indet. is better in a scientific publication than an unconfident specie assignment.

[readinghiker]

To Anomotodon,

 

 

   I have finished going through all of the squalicorax teeth from the Cabezon site.  They are, for the most part very beat up and fragmented.

I have collected 928 teeth, and 62 have these indentations.  That is 7.6%, quite a high percentage if this is an anomaly (I am not saying that it isn't,

just that the number is high),  I have corresponded with Mike Everhart from Fort Hays' Sternberg Museum, who wrote and maintains

the Oceans of Kansas website (of which I'm sure you are familiar).  He agrees with you that these teeth are similar to or are S. falcatus, but he has never seen

the indentations on any that have come out of the Niabara formation of western Kansas.  Do you have photos of the S. falcatus and/or S. curvatus with these

indentations?  I would love to see them and compare them with mine.

  Again, thank you for all of your help.  Happy collecting!

Randy

 

 

[MikaelS]

What is your definition of S. falcatus? The lectotype is from the Turonian (Lewis, UK) and, unfortunately, rather poorly preserved. The root in particular is abraded/corroded so you can't really determine its original shape. Its always best if you compare your material with type specimens as opposed to someones gut feeling of a species concept. 

[readinghiker]

This is based on comparisons with material (albeit photographic) of material from research by Welton, Bourdon, Everhart and  others.  Falcatus is a very common shark from

this time period and from this area.  And I didn't define it as falcatus, but simply as cf. falcatus.  There are other Squalicorax species from New Mexico, but the blade morphology is a bit different.  Since I don't have any with complete roots, I am simply referring to the most common Squalicorax in the area that is the most similar.  It will be up to the peer reviewers when I get the other couple of dozen species from this fauna described to tear this apart or support it.

Thanks for your input!

 

Randy

[readinghiker]

Sorry, I didn't define it as falcatus in my most recent post to another member on this site.  I revised my thinking after reviewing the specimens a third time using a Zeiss

microscope instead of the DinoXscope that I had been using.  

[MikaelS]

7 hours ago, readinghiker said:

This is based on comparisons with material (albeit photographic) of material from research by Welton, Bourdon, Everhart and  others.  Falcatus is a very common shark from

this time period and from this area.  

The nominal S. falcatus stand and and fall by the quality of the type material. There is a high probability that none of the people you mentioned have ever examined the lectotype of S. falcatus first hand. It is also probable that they have never examined the lectotype of S. curvatus either. I know where the lectotype of the former is but as far as I know, the type specimen of the latter is currently lost. It was not in the Smithsonian collection according to R. Purdy.

 

Welton and Farish's 1993 work is getting a bit outdated in regards to the anacoracids, which I am sure they would confirm if you asked them.

[readinghiker]

I agree with most of what you have said.  However, very few people have the funds or means (or time) to track down all of the lectotypes of every species

they are working on, and must rely on information printed in the various journals.  Welton is an acquaintance of mine, and he would agree that a lot of his work is dated.

He is retired, and as I write, enjoying southern Mexico with his wife.

 

Randy

[MikaelS]

No one has suggested you need to examine the primary types of all species you work on. Some are so well illustrated/preserved so there is no need for it. However if you want to be taken seriously you need to put in an effort and/or at least treat poorly known nominal species as the nomina dubia they often are. In my first year as a PhD student at Lund University in Sweden I realised I needed to examine type specimens first hand in Brussels (meeting Jaques Herman) and Montpellier (Henri Cappetta). As a poor student I first had to save up money by working as a cleaner at a nuclear power plant. I then rented a car in southern Sweden, drove all the way to Brussels in Belgium and then down to Montpellier along the Meditteranean coast. Tracking down obscure type specimens is pretty standard activity in just about all disciplines of palaeontology, except for people working on Cretaceous/Cenozoic chondrichthyan teeth. I never quite understood why that is.

[readinghiker]

Good for you.  Paleontology is not a vocation for me, but an avocation.  I have recently retired from teaching mid school (history).  I have read Cappetta, et. al. and 

am doing the best I can do with the support of the people at the New Mexico Museum of Natural History and Science.  I hope you are doing well.

 

Randy