Re: News: Dog finds sail-back synapsid fossil from Carboniferous in Nova Scotia

[Jocelyn Falconnet <j.falconnet@gmail.com>]

Very nice discovery ! For additional higher-quality pictures of the 
skeleton, see:

http://novascotia.ca/news/smr/2012-08-16-Fossil-Find/

The base of the neural spines can be seen on the left half of the 
skeleton (in the showcase).

As far as I can tell, "Superstar" is no synapsid because:

1/ The lateral view of the skull shows no obvious temporal fenestra 
where it should be.
2/ The jugal is not trifid but has a wide posterior process, as in many 
non-fenestrated tetrapods.
3/ The quadratojugal is very large compared to that of other early amniotes.
4/ The surface of these bones has been badly eroded but parts of the 
original ornamentation (made of pits and grooves) can be seen on the 
quadratojugal and squamosal.
5/ To check: the bone located in the orbit is probably part of a 
sclerotic ring (unknown in synapsids).

... and the most interesting feature:

6/ There is what I interprete as a temporal notch, in the dorsoposterior 
corner of the skull.

In fact, this skull is incredibly similar to that of *Dendrerpeton 
acadianum* (see Holmes et al., 1998: figs: 1, 3-4). I mean, look at the 
general shape and the relationships between the bones !

The postcranium, however, might belong to a synapsid but the vertebrae 
are too small on the picture (in the showcase) to figure out their 
structure. Please remember that such wide, flat ribs are known in 
*Ichthyostega* and in several temnospondyls such as *Eryops*. I see 
nothing on the pectoral girdle precluding its assignment to either 
temnospondyls or synapsids. A good picture of the clavicles and 
interclavicle, if they are present, would help a lot, as they show a 
deep ornamentation in temnospondyls. The neural spines, if they belong 
indeed to a synapsid, retained the elongated blade-like morphology seen 
in *Sphenacodon*, *Ctenospondylus*, or *Ctenorhachis*.

I read that the skull was found later that the skeleton, but the 
question is: were they associated or not ?

Cheers,
Jocelyn

Ref:

Holmes, R.B., Carroll, R.L. & Reisz, R.R. 1998. The first articulated 
skeleton of Dendrerpeton acadianum (Temnospondyli, Dendrerpetontidae) 
from the Lower Pennsylvanian locality of Joggins, Nova Scotia, and a 
review of its relationships. Journal of Vertebrate Paleontology 18(1), 
64–79.

Le 16/08/2012 21:25, Ben Creisler a écrit :
> From: Ben Creisler
> bcreisler@gmail.com
>
>
> At couple of versions of a news story about discovery of sail-back
> synapsid fossilin Nova Scotia, Canada, with different photos:
>
> http://www.cbc.ca/news/canada/nova-scotia/story/2012/08/16/ns-superstar-sail-back-fossil.html
>
> http://atlantic.ctvnews.ca/family-makes-nova-scotia-s-most-significant-fossil-find-1.916896
>
>
> (The skull looks more like an edaphosaurid to me, the Dimetrodon model
> notwithstanding. Also, dogs are known to have an acute sense of smell
> that can detect traces from days before--but 300 million years
> before?!)