Re: Polacanthidae?

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

>Policanthidae?
>
>I thought that Policanthus was an invalid genus and that its material has
>since been refered to Hyleaosaurus.  Please correct me if I'm wrong on this.

Recent research has shown that a) Polacanthus is a distinct taxon from
Hylaeosaurus and that b) Hylaeosaurus is closer to the typical
"Nodosauridae" than is Polacanthus.

>If Policanthus is indeed invalid, would Hylaeosaurus be the type genus for
>the family Policanthidae?  If this is so, shouldn't it be renamed
>Hylaeosauridae (or Mymooropeltidae, or Sauropeltidae)?

Since Hylaeosaurus is not a member of the Polacanthus-Mymoorapelta group,
it would not be the Hylaeosauridae.

>P.S. I heard something about Jurassosaurus deserving its own family.  Do you
>know if this is true or not?  That would be something to have the "old Nodosau
>ridae" really constitute four seperate families (Nodosauridae, Policanthidae,
>Minmidae, and Jurassosauridae).

Jurassosaurus is not a nodosaurid, but a) has turned out to be an
ankylosaurid and b) is formally Tianchisaurus (or something like that).  I
personally do not like monotypic families, but we could wind up with an
Ankylosauria looking something like...

Ankylosauria
        Ankylosauridae (incl. Tianchisaurus)
        Minmi
        Polacanthidae
        Nodosauridae

Hope this answers your questions.

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.