Shark Cousins.

[Auspex]

Ron,

are they ray "spine bases" or large dermal denticles?

Whatever these things are, they are not flattened on the "bottom", very unlike denticles.

[Guest bmorefossil]

Nice plates you got there ron. I've gotten a good deal of them from the Eocene and Paleocene as well but i have found it exceedingly hard to find plates from the Miocene in only having found 2-3 complete ones. Just curious if others have had the same experience.

yes i have had the same problem, even when i find them in the matrix still they are just partials haha, im not sure what happens.

[Pristiformes]

Here are some Eocene Guitar fish (Hypolophodon sylvestris) denticles, alongside one from a recent, Thornback Ray (Raja clavata) A lot smaller than yours though.

I always think of ray 'spines' as those from the likes of stingrays, though others might consider the 'thorns' or denticles, as spines. Here is a link to a good pic of a thornback, showing denticles around the tail and down the centre of its back. They are also dotted in various places all over the back, in various sizes.

Hypolophodon sylvestris is actually a whiptail ray (Dasyatidae), and not a guitarfish (Rhinobatidae). None of the modern guitarfishes have any dermal spines like that. They do have dermal denticles, but these are much smaller than are dermal spines (like maybe a mm in diameter). One difference between dermal spines and dermal denticles, besides the obvious difference in size, is that dermal denticles are regularly replaced (like the teeth in all elasmobranchs), but the dermal spines are not replaced.

[Bill]

Elasmo has, Dasyatidae.

With the note, Ward & Wiest (1990) list Hypolophodon sylvestris (WHITE 1931) in the Palaeocene & Lower Eocene of Europe, West Africa and the Chesapeake Region (Maryland & Virginia).

Ward wrote "Fossils of Abbey Wood", for the Tertiary Research Group website, in which he has H. sylvestris as Guitar fish. Here

[siteseer]

Nice plates you got there ron. I've gotten a good deal of them from the Eocene and Paleocene as well but i have found it exceedingly hard to find plates from the Miocene in only having found 2-3 complete ones. Just curious if others have had the same experience.

Yeah, it's tough to find a tooth plate with more than 2-3 medial teeth together - really tough to find one with a lateral tooth still attached. In twenty years of collecting, I found only two plates with more than three teeth together.

[Pristiformes]

Elasmo has, Dasyatidae.

With the note, Ward & Wiest (1990) list Hypolophodon sylvestris (WHITE 1931) in the Palaeocene & Lower Eocene of Europe, West Africa and the Chesapeake Region (Maryland & Virginia).

Ward wrote "Fossils of Abbey Wood", for the Tertiary Research Group website, in which he has H. sylvestris as Guitar fish. Here

Interesting. I didn't know that any authors had suggested that species might be a member of the guitarfish family. Thanks for the information. I wonder what prompted Ward to associate Hypolophodon with the guitarfishes? Whiptail rays and guitarfishes are not terribly similar, besides that they are both batoid groups, in my opinion.

[Bill]

Interesting. I didn't know that any authors had suggested that species might be a member of the guitarfish family. Thanks for the information. I wonder what prompted Ward to associate Hypolophodon with the guitarfishes? Whiptail rays and guitarfishes are not terribly similar, besides that they are both batoid groups, in my opinion.

I'll email David and see what he says.

[Bill]

Here is David's reply.

The ray Hypolophus was a sting ray. When the species sylvestris was transferred to Hypolophodon, it was retained in the Dasyatidae. However, sting rays generally have tail spines unless secondarily lost. No sting ray spines have been found at Abbey Wood, thus either it is not a sting ray, or the spines have been lost. There are no primitive Hypolophodon-like species with spines thus the likelihood is that it is not a Dasyatid. The tooth shape and lingual flange is similar to those of the guitarfish,, so the rhinobatidae would be my best bet.

[barefootgirl]

Thanks for the picts and the in depth discussion. I love learning about this kinda stuff.

[siteseer]

Here is David's reply.

The ray Hypolophus was a sting ray. When the species sylvestris was transferred to Hypolophodon, it was retained in the Dasyatidae. However, sting rays generally have tail spines unless secondarily lost. No sting ray spines have been found at Abbey Wood, thus either it is not a sting ray, or the spines have been lost. There are no primitive Hypolophodon-like species with spines thus the likelihood is that it is not a Dasyatid. The tooth shape and lingual flange is similar to those of the guitarfish,, so the rhinobatidae would be my best bet.

Obviously, I yield to David Ward's expertise, but he would also welcome an alternate opinion. I once showed him a tooth and asked his opinion and he asked me what I thought it was.

This could be one of those situations in nature where a common name or modern taxon doesn't apply. Think of amphicyonids, which are called "bear-dogs" (a general "ballpark" label at best) for lack of a common name as they died out at the end of the Miocene. They were neither bears nor dogs. They comprise a distinct family within the order Carnivora. The average person wants a convenient category for a given fossil but for most extinct organisms like an amphicyonid, "not applicable" is preferable to having to choose between "dog," bear," or "bear-dog."

Hypolophodon is known only from teeth which are vaguely dasyatid in shape but a distinct lingual flange (aka uvula) is more characteristic of guitarfishes (the earliest stingrays might not have born spines; that's just how we define the Late Cenozoic descendants we know best). However, this genus is known arguably from only the Late Paleocene to Early Eocene - old enough to belong to an archaic Cretaceous group that survived into the Cenozoic but didn't make it to the Oligocene. Some of the Cretaceous rays remain not so confidently classified like Myledaphus and Protoplatyrhina though they may also be a dasyatid and a rhinobatid respectively.

In any case it would be great if someone found a complete body fossil of Hypolophodon and a few other rays with names based only on teeth. Years ago, a friend told me that someone found a ray dentition of a genus known only from isolated teeth in Morocco and that it was being studied. While not a whole body fossil, its classification among the rays might change.

[Boesse]

Alright... while we are talking about batoids, here is one of the coolest batoid fossils I've ever found - a nearly complete calcified meckel's cartilage from Raja binoculata. I have a couple dozen of these - meckel's and palatoquadrate cartilages. For comparison i've attached a photo of a modern specimen. The fossil specimen is not the greatest, but one of the only ones I have that is edited properly.

Bobby

[Boesse]

This thread disappeared off the new posts lists right after I added (what I think is) a neat post, so i'm giving it a bump.

Bobby

[Northern Sharks]

Bobby: I, for one, am impressed. Is the white scale bar 1 cm, 1 inch or other?

[Boesse]

Hey Northern, the scale bar =1cm. The fossil specimen is the first I've found, and parts of the Purisima Formation, these are almost as common as cetacean ribs and vertebrae. Some of them display prismatic cartilage, but typically a more fibrous grainy cartilage.

Bobby