Some Bits and Bobs of the Taxonomic History of Weltonia ancistrodon

 In which I unravel a bit of the taxonomic foundation for this particular species of cow sharks and get sidetracked by some of the bits and bobs I came across in the process.  I'm easily diverted, particularly since it's the people featured in any taxonomic story that I usually find most interesting.

Among the strangest of shark teeth are those of cow sharks (members of the Hexanchidae family).  Here are a couple fossil teeth of the cow shark Notorynchus primigenius that I found along the Calvert Cliffs.  These likely date from mid-Miocene Epoch, or perhaps roughly 16 to 14 million years ago.

These are all from the lower jaw of the fish with the largest cusp at the anterior end of each tooth.  The larger of the two is 20 mm in length.

The extant species in this family of sharks are distinguished from other sharks principally by the number of pairs of gill slits its members have (either six or seven - other sharks have five pairs) and an array of other attributes often characterized as primitive.  It is assumed that the extinct species with such teeth shared those various morphological attributes.  Perhaps most important for the fossil collector, the species in this family sport distinctive teeth, easily distinguished from all others.  This observation applies principally to teeth from the bottom jaw which, as seen above, are rectangular in shape with a row of several curved cusps headed, for the most part, by a prominent initial one (there may be cusplets in front of it).  Complicating things somewhat is the fact that teeth of any one individual cow shark can vary by its sex and age, and by the precise location in the shark's jaw from which the tooth came.  As a result, precisely ascribing an isolated cow shark tooth to a particular species can be difficult.  (See Bretton W. Kent, Fossil Sharks of the Chesapeake Bay Region, 1994, p. 17.)

As unusual as I find these teeth, those of one species of cow shark - Weltonia ancistrodon (Arambourg, 1952) - are, I think, the most striking of the lot.  The tooth from this species shown below (which may be partially repaired) dates, according to the dealer from whom I purchased it, to the Eocene Epoch (56.0 to 33.9 million years ago) and was found at Khouribga, Morocco.  It is 13 mm in length.

Obviously, the most startling feature of this tooth is the exaggerated first cusp that extends high over the other cusps on the tooth and curves back at its tip.  Remove that and the rest of the tooth bears the typical features of other cow shark teeth.

How did it come to have this scientific name?

Camille Arambourg (1885-1969) was the first to describe this species based on teeth he collected at Khouribga, Morocco.  Arambourg's journey into paleontology was fortuitous.  He trained in agricultural engineering, but, as a young man, while helping his father dig an irrigation system on the family farm in Algeria, he uncovered a trove Miocene fish fossils.  That sparked a life-long interest in the fossils of Africa and a distinguished academic career in geology and paleontology, which culminated in his appointment as professor of paleontology at the Museum of Natural History in Paris (Muséum National d'Histoire Naturelle).  (See entry for Camille Louis Joseph Arambourg at Encyclopedia.com, and Djillali Hadjouis, Camille Arambourg (1885-1969), Historiographie de Préhistoriens et de Protohistoriens Français du XX° Siècle, 2018.)

In Les Vertebres Fossiles des Gisements de Phophates (Maroc-Algerie-Tunisie) (Notes Mem. Serv. Mines Cart Geol. Maroc., 1952), Arambourg described teeth from various cow shark species.  Among the cow shark teeth, one kind was distinctive.  He asserted, "no other fossil form . . . combines similar characteristics.  In order to distinguish it, I therefore propose to name this new fossil:  N. ancistrodon."  (p. 44)  He placed it in the genus Notidanus.  The new species name, he noted, is a combination of Greek roots for "hook" and "tooth."

He also observed that this particular taxon was particularly abundant in strata from the Thanetian and Ypresian Ages.  These straddle the divide between  the Paleocene and Eocene Epochs and are dated 59.2 to 56.0 million years ago and 56.0 to 48.1 million years ago, respectively.  

It's not surprising that Arambourg came to use this species name given that prominent first cusp.  In fact, the word Ancistrodon had already been used taxonomically over the years as the genus name for an array of poisonous snakes:  copperheads, moccasins, and vipers.  Very appropriate for animals with fangs.  (According to the Integrated Taxonomic Information System, this genus name for snakes is no longer valid.  I would note that the scientific name that I believe is now applied to the shark species to which the tooth shown above belongs does not appear at all in the ITIS.)

In 1979, paleontologist David John Ward reconsidered the taxonomy of this species, giving it a new genus name:  Weltonia.  (Addition to the Fish Fauna of the English Palaeogene.  3. A Review of the Hexanchid Sharks with a Description of Four New Species, Tertiary Research, Volume 2, Number 3, 1979.)  Ward selected as the lectotype for this new species, the tooth that Arambourg had shown as figure 65 on plate 1 in his 1952 publication.  (A lectotype is the representative or type specimen for a species when the holotype was not selected by the original author.)  Here is the image of the lectotype tooth from the 1952 publication.  (I believe I have not violated any copyright laws by reproducing a small portion of the original publication and am doing so for educational, noncommercial purposes.)

Ward's professional life has contained the same sort of career change that marked Arambourg's.  He trained and practiced for several years as a veterinary surgeon, but his interest in fossils apparently took over, and he retired as a surgeon to pursue paleontology.  As far as I can tell, he doesn't have an academic degree in the field, though he is the author of many paleontology papers, including the one cited here, and is, at present, a scientific associate at The Natural History Museum, London.

In his description of W. ancistrodon, Ward took Arambourg to task.  First, he stated that Arambourg asserted incorrectly that the teeth with the prominent first cusp were from the shark's upper jaw.  They are, in fact, from the lower.  Further, the teeth Arambourg identified as coming from the species' lower jaw were actually from another cow shark genus altogether.

I am puzzled a bit by Ward's notation about where the teeth Arambourg described were held.  He wrote, "Depository:  (presumably) the Arambourg Collection, Paris Museum."  Presumably suggests that these teeth were, at least then, missing.  Indeed, I could not find them listed in the database of the fish holdings of the Muséum National d'Histoire Naturelle where Arambourg was paleontology chair and whose fish fossil collection he was instrumental in building.  So, it would seem that the identification of this new species rests presently on images reproduced in a 1952 publication, not the actual teeth (wherever they might be).

I am amused by Ward's brief explanation of the origin of the genus name he newly applied to W. ancistrodon.  Actually it's how he explained the origins of several new names he applied in this article that I found most amusing.  For W. ancistrodon, Ward wrote that the genus is "named after the American palaeochondrichthyologist Dr. Bruce Welton."  Full stop.  Nothing more about Dr. Welton.  In contrast, he observed of using Mr. D. Kemp's name for Notorynchus kempi that it was "in recognition of [his] field assistance."  A tad bit more expansive here than he was with the explanation of Weltonia, but not much.

Things become more interesting with Ward's explanation of two other new names.  For Hexanchus collinsonae, a new species in the established genus Hexanchus, Ward said that it was "named after the English palaeobotanist Dr. M. Collison in recognition of field assistance and stimulating conversation."  Hmmm.  For Hexanchus hookeri, another new species in this genus, Wards noted it is "named after the English palaeomammalogist Mr. J. Hooker in recognition of field assistance and lively discussions."

So, apparently, Ward didn't find Welton to be much of a conversationalist, certainly not stimulating or lively, a failing also true, it would seem, for Mr. Kemp.  This looks like a slight to me, whether intended or not.  Though, of course, any sting of the apparent slight to Welton is minimized because his name was given to a genus, a level higher than species in the taxonomic order of things.  Poor Mr. Kemp.