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



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?!)