RE: Pegomastax, new heterodontosaurid from South Africa in new Sereno monograph (free pdf!)

[Mickey Mortimer <mickey_mortimer111@msn.com>]

And here I thought Butler was redescribing heterodontosaurids...

In general, this is an excellent paper with numerous useful photographs and 
illustrations (well, besides the bobble-headed Tianyulong- 
http://www.pensoft.net/J_FILES/1/articles/2840/export.php_files/ZooKeys-226-001-g030.jpg).
  But I can't wrap my head around Sereno's dismissal of Geranosaurus-

"Geranosaurus atavus, nonetheless, differs in several regards from 
Heterodontosaurus tucki, which also occurs in the Clarens Formation, and from 
heterodontosaurids from the underlying Upper Elliot Formation. The dentary 
tooth row in Geranosaurus atavus appears to be composed of eight subequal 
postcaniniform teeth arranged along a medially bowed tooth row (Fig. 2B). In 
Heterodontosaurus, in contrast, there are 11 or 12 dentary teeth that increase 
in size toward the center of a relatively straight tooth row. Abrictosaurus 
also has a higher tooth count and size differential along the dentary tooth 
row, as well as a relatively smaller caniniform tooth. Unlike Heterodontosaurus 
and Lycorhinus, a postcaniniform diastema is not present in Geranosaurus 
atavus, as the second tooth positioned adjacent to the caniniform tooth (Fig. 
2B). Crompton and Charig (1962) cited the absence of an arched 
premaxilla-maxillary diastema in Geranosaurus atavus to differentiate 
Geranosaurus atavus, although this portion of the upper jaw does not appear to 
have been preserved.

Recently Norman et al. (2011) concluded that Geranosaurus atavus cannot be 
distinguished by a “unique combination of characters”. Although not adequate to 
justify taxonomic recognition, the features exhibited by Geranosaurus atavus 
and discussed above clearly suggest there is a second heterodontosaurid taxon 
in the Clarens Formation in addition to Heterodontosaurus tucki."

So it's distinctive from other heterodontosaurids and already has a name, yet 
it is "not adequate to justify taxonomic recognition."  Er...

Mickey Mortimer

----------------------------------------
> Date: Wed, 3 Oct 2012 09:19:17 -0700
> From: bcreisler@gmail.com
> To: dinosaur@usc.edu
> Subject: Pegomastax, new heterodontosaurid from South Africa in new Sereno 
> monograph (free pdf!)
>
> From: Ben Creisler
> bcreisler@gmail.com
>
> A new taxon in a new monograph at ZooKeys site. The pdf is free!
>
> Paul Sereno (2012)
> Taxonomy, morphology, masticatory function and phylogeny of
> heterodontosaurid dinosaurs.
> ZooKeys 224: 1-225.
> doi: 10.3897/zookeys.224.2840
> http://www.pensoft.net/journals/zookeys/article/2840/taxonomy-morphology-masticatory-function-and-phylogeny-of-heterodontosaurid-dinosaurs
>
>
> Heterodontosaurids comprise an important early radiation of
> small-bodied herbivores that persisted for approximately 100 My from
> Late Triassic to Early Cretaceous time. Review of available fossils
> unequivocally establishes Echinodon as a very small-bodied,
> late-surviving northern heterodontosaurid similar to the other
> northern genera Fruitadens and Tianyulong. Tianyulong from northern
> China has unusual skeletal proportions, including a relatively large
> skull, short forelimb, and long manual digit II. The southern African
> heterodontosaurid genus Lycorhinus is established as valid, and a new
> taxon from the same formation is named Pegomastax africanus gen. n.,
> sp. n. Tooth replacement and tooth-to-tooth wear is more common than
> previously thought among heterodontosaurids, and in Heterodontosaurus
> the angle of tooth-to-tooth shear is shown to increase markedly during
> maturation. Long-axis rotation of the lower jaw during occlusion is
> identified here as the most likely functional mechanism underlying
> marked tooth wear in mature specimens of Heterodontosaurus. Extensive
> tooth wear and other evidence suggests that all heterodontosaurids
> were predominantly or exclusively herbivores. Basal genera such as
> Echinodon, Fruitadens and Tianyulong with primitive, subtriangular
> crowns currently are known only from northern landmasses. All other
> genera except the enigmatic Pisanosaurus have deeper crown proportions
> and currently are known only from southern landmasses.
>
> new release with video:
> http://phys.org/news/2012-10-fanged-dwarf-dinosaur-southern-africa.html
>
> (NOTE: One glitch in the name : mastax "jaw" is feminine in Greek so
> the name should be Pegomastax africana to follow the letter of the
> rules.)