[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Krzyzanowskisaurus

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.