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Re: Oviraptorid questions
Balanoff et al (2009) cited Senter et al (2004) as suggesting that
Protarchaeopteryx and Incisivosaurus may be synonymous.
>From Senter et al (2004), p. 3:
"Here, Incisivosaurus is considered a junior synonym of
Protarchaeopteryx. Data for Protarchaeopteryx were collected from the
holotype of P. robusta (NGMC 2125) and the published description of P.
gauthieri (Xu, Cheng, et al., 2002). P. gauthieri was originally
described as the type species of a new genus, Incisivosaurus (Xu,
Cheng, et al., 2002). However, the two species should be treated as
congeners, as their overlapping elements are identical except for
tooth count. These two species uniquely share a very bizarre
dentition, which has a number of unusual attributes: (1) a single pair
of enlarged, anteroposteriorly compressed teeth at the front of the
premaxilla, (2) diminutive, peglike teeth immediately posterior to the
enlarged pair of teeth, (3) diminutive, lanceolate posterior teeth,
and (4) absence of teeth at the tip of the dentary (NGMC 2125; Xu,
Cheng, et al. 2002) (Fig. 1). Also, despite the crushing of the skull
in NGMC 2125, which is so extensive that for most upper teeth one
cannot tell whether they are left or right teeth, it is clear that
NGMC 2125 shares with "Incisivosaurus" (1) a short, high skull, (2)
tall premaxilla, and (3) dentary with anterior margin strongly beveled
so that the dorsal margin terminates in a 50-60 point (NGMC 2125; Xu,
Cheng et al., 2002) (Fig 1). We consider these similarities,
especially the dental characters, sufficient to demonstrate generic
identity. A significant difference in tooth count (Ji et al., 1998;
Xu, Cheng, et al., 2002) justifies the maintenance of separation of
the two taxa at the species level. However, this difference does not
compromise the utility of the genus as an operational taxonomic unit
in the present analysis.
Published descriptions state that serrations are absent on the teeth
of "Incisivosaurus" (Xu, Cheng, et al. 2002) but present on those of
NGMC 2125 (Ji et al., 1998). However, examination of NGMC 2125 by
P.S., using a zoom lens as a makeshift microscope, revealed that the
apparent serrations on the one preserved enlarged premaxillary tooth
crown are places where the edges of the teeth are chipped. No
serrations could be seen by P.S. on the posterior teeth, nor are any
evident in the published photos of these teeth (Ji et al., 1998, fig.
Effectively, Senter is only arguing that Protarchaeopteryx robusta and
Incisivosaurus gauthieri are sister taxa. You could maintain generic
separation or not depending on how you want to calibrate your
genericometer, it doesn't really matter in this case, IMHO.
Balanoff, A. M., X. Xu, Y. Kobayashi, Y. Matsufune, and M. Norell.
2009. Cranial Osteology of the Theropod Dinosaur Incisivosaurus
gauthieri (Theropoda: Oviraptorosauria). American Museum Novitates,
3651: 35 p.
Free online: http://hdl.handle.net/2246/5970
Senter, P., R. Barsbold, B.B. Britt, and D.A. Burnham. 2004.
Systematics and evolution of Dromaeosauridae. Bulletin of Gunma
Natural History Museum 8: 1–20.