Re: Krzyzanowskisaurus

[Tim Williams <twilliams_alpha@hotmail.com>]

Apologies if these references and abstracts have been posted previously...


Heckert, A.B. (2005). _Krzyzanowskisaurus_, a new name for a probable 
ornithischian dinosaur from the Upper Triassic Chinle Group, Arizona and New 
Mexico, USA.  p.77-83.  In: Heckert, A.B. and Lucas, S.G. (Eds.) Vertebrate 
Paleontology in Arizona, New Mexico Museum of Natural History and Science 
Bulletin No. 29.

Abstract: "Recent discoveries have demonstrated that _Revueltosaurus 
callenderi_ Hunt is not an ornithischian dinosaur, so it is probably not 
congeneric with the putative ornithischian _Revueltosaurus hunti_ Heckert.  
_Revueltosaurus_ Hunt, 1989 is the senior generic name, so I propose here 
the generic name _Krzyzanowskisaurus_ for ?_Revueltosaurus_? _hunti_.  
Because the teeth of _K. hunti_ appear more derived than _R. callenderi_, 
and are in fact more ?typically? ornithischian than those of _R. 
callenderi_, I tentatively suggest that it does in fact represent an 
ornithischian dinosaur.  Both _R. callenderi_ and _K. hunti_ have 
biostratigraphic significance. The former is an index taxon of the 
Revueltian land-vertebrate faunachron (lvf), and the latter is an index 
taxon of the Adamanian lvf. Indeed, the stratigraphic range of _R. 
callenderi_ discriminates a discrete interval of Revueltian time (Barrancan) 
and that of _K. hunt_ a subset of Adamanian time (St. Johnsian)."

The name honors Stan Krzyzanowski, "a lifelong devotee of Arizona?s fossil 
record".

Hunt, A.P., Lucas, S.G. and Spielmann, J.A. (2005).  The postcranial 
skeleton of _Revueltosaurus callenderi_ (Archosauria: Crurotarsi) from the 
Upper Triassic of Arizona and New Mexico, USA. p.67-75.  In: Heckert, A.B. 
and Lucas, S.G. (Eds.) Vertebrate Paleontology in Arizona, New Mexico Museum 
of Natural History and Science Bulletin No. 29.

Abstract: "_Revueltosaurus callenderi_ is an armored crurotarsan that is 
widely distributed in early Norian (Reveultian: Barrancan) vertebrate fossil 
assemblages in Arizona and New Mexico.  It is a highly distinctive taxon 
that has apomoprhic postcranial features including: (1) rectangular 
paramedian osteoderms with an irregular pattern of deep pits with an 
anterior bar that extends onto the lateral margin: and (2) wide tarsus 
(because of wide astragalus) that has a small astragalar medial process and 
corresponding medial calcaneal concavity. _R. callenderi_ is a crurotarsan 
that may be a sister taxon of Stagonolepididae."

The authors present some ideas on the lifestyle of _Revueltosaurus_: "The 
orientation of the large denticles and wear facets indicates that 
_Revueltosaurus callenderi_ was herbivorous (Hunt, 1989; Hunt and Lucas, 
1994; Heckert, 2002, 2004).  This is consistent with the heavy dorsal armor, 
which is rare in carnivores that are not semiaquatic. The articulated 
specimen represents an animal about 1.5 m long.  Other specimens indicate 
individuals about twice as large.  The taphonomy and faunal associations of 
_Revueltosaurus_ sites (e. g., NMMNH locality 1; Dinosaur Hill) indicate a 
terrestrial ecology."

Hunt et al. (2005) go on to say that some of the "ornithischiaform" taxa 
from the Late Triassic of North America may come from bona fide 
ornithischians (_Technosaurus_, _Krzyzanowskisaurus_), whereas the rest are 
probably revueltosaurus (_Galtonia_, _Tecovasaurus_, _Protecovasaurus_, 
_Pekinosaurus_, _Tecovasaurus_, _Lucianosaurus_).  In this context, the 
authors are using the term "ornithischiaform" to designate a particular 
dental morphology (convergent in ornithischians and revueltosaurs), not as a 
phylogenetic term (i.e., there is no "Ornithischiaformes").  There is no 
mention of _Eucoelophysis_ or _Azendohsaurus_, and any potential link 
between _Silesaurus_ and revueltosaurs is not discussed.

_Technosaurus_ is deemed "probably ornithischian" because of imbication of 
the tooth crowns; increase in the size of the teeth to the posterior center 
of tooth row; and because the tooth row is not marginal.

The affinities of _Galtonia_ are "equivocal": it could be the premaxillary 
teeth of either an ornithischian or a revueltosaur, say Hunt et al. (2005).

_Pekinosaurus_ is "possibly ornithischian" because the dentary/maxillary 
tooth crowns are more elongate than in _Revueltosaurus_, which may have 
required imbrication; but there is no cingulum.  However, the authors 
earlier appear to lean towards revueltosaur (non-rornithischian) affinities 
for _Pekinosaurus_ (see above).

_Tecovasaurus_, _Lucianosaurus_, _Protecovasaurus_, _Crosbysaurus_ are 
likewise "equivocal", but all are "probably not ornithischian" given that 
the dentary/maxillary crowns lack a cingulum.

_Krzyzanowskisaurus_, also based on dentary/maxillary teeth, is "probably an 
ornithischian" as some teeth bear a cingulum.

BTW, _Revueltosaurus hunti_ was described in:

Heckert, A. B. (2002). A revision of the Upper Triassic ornithischian 
dinosaur _Revueltosaurus_, with description of a new species.  New Mexico 
Museum of Natural History Bulletin 21: 253-268.

_Crosbysaurus harrisae_ and _Protecovasaurus lucasi_ were apparently 
described in:

Heckert, A. B. (2004).  Late Triassic microvertebrates from the lower Chinle 
Group (Otischalkian-Adamanian: Carnian), southwestern U.S.A.  New Mexico 
Museum of Natural History and Science, Bulletin 27, 170 p.

(I have not seen the above two references, and I wasn't aware until now that 
_Crosbysaurus_ and _Protecovasaurus_ were valid generic names.)

My thanks to Jaime Headden for bringing my attention to the 
_Krzyzanowskisaurus_ paper and the new _Revueltosaurus_ paper.

Finally, on a less positive note... this concerns a fellow named Stephan 
Pickering that some of you may have come across.  Stephan runs his own 
discussion forum that is based (very tenuously) on paleontology.  He has a 
habit of copying-and-pasting messages from the DML Archives (mostly 
references and abstracts) and posting them at his own forum.  The other 
thing that Stephan does at his own forum is to launch bizarre and vitriolic 
attacks against the DML (I guess he is still bitter over being kicked off 
the DML a few years ago).  So Stephan, should you come across this message 
during your frequent perusals of the DML Archives, I don't begrudge you your 
right to criticize the DML; but the next time you post the contents of a DML 
message at your own forum, maybe you could actually acknowledge the source.  
I know you are under no obligation to do so, but it might be the courteous 
thing for you to do.

Cheers

Tim