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Bainoceratops -- "Leptoceratopsid" or Sistergroup to the Ceratopsidae?
Hello all! I just finished adding all of the characters and codings from
Peter Makovicky's analysis of neoceratopsians (P. Makovicky, 2001) and then
I added Bainoceratops efremovi and Liaoceratops yanzigouensis into the
matrix. Bainoceratops is only known from a vertebral series and
Liaoceratops is only known from cranial material.
I performed the analysis in PAUP* 4.0b10, using the Heuristic Search. There
were 166 most parsimonious trees and 6462 steps per tree. Character
optimization was set to Delayed Transformation (DELTRAN).
The results were-
--+--Hypsilophodon
`--+--Stegoceras
`--+--Chaoyangsaurus
`--+--Psittacosaurus
`--+--Archaeoceratops
`--+--+--Asiaceratops
| `--+--Montanoceratops
| `--+--Udanoceratops
| `--Leptoceratops
`--+--Liaoceratops
`--+--Microceratops
`--+--+--Bagaceratops
| `--Protoceratops
`--+--Bainoceratops
`--+--Zuniceratops
`--+--Centrosaurus
`--Triceratops
Psittacosaurus is united with the Neoceratopsians to the exclusion of
Chaoyangsaurus on the basis of the following characters-
7(1). Relative height of the premaxilla (snout) to orbital region deep.
9(1). Nares positioned dorsal, away from the buccal margin.
14(1). Maxillae contact each other anterior to choanae.
22(1). Jugal horns present and laterally directed.
36(1). Pterygoid-maxilla contact at posterior end of tooth row.
46(1). Exoccipital with two exits for cranial nerves X-XII near occipital
condyle.
51(1). Supraoccipital wider than tall, trapezoidal.
59(1). Coronoid process set lateral to tooth row, and end of tooth row
covered by anterior part of coronoid process.
86(1). Scapula relatively flat in sagittal view.
87(1). Scapular blade almost perpendicular to glenoid.
Asiaceratops, Montanoceratops, Udanoceratops and Leptoceratops are united on
the basis of the following character-
54(1). Large pit at anterior end of dentary.
Montanoceratops, Udanoceratops, and Leptoceratops are united on the basis of
the following characters-
25(1). Postorbital with concave dorsal shelf bordering supratemporal
fenestra.
44(1). Basal tubera everted posterolaterally, forming lip beneath occipital
condyle.
50(1). Supraoccipital in same plane as posterior face of basioccipital.
51(0). Supraoccipital tall and triangular.
66(2). Teeth occlude at a vertical angle but dentary teeth have a horizontal
shelf on the labial face.
68(1). Base of primary ridge set back from cingulum, which forms a
continuous ridge at the crown base.
71(1). Dentary tooth crowns with bulbous expansion at root-crown transition
on labial side of tooth.
Udanoceratops and Leptoceratops are united on the basis of the following
characters-
15(1). Dentigerous margin of maxilla ventrally convex.
56(0). Ventral margin of dentary curved.
80(0). Dorsal vertebrae with flat articular zygapophyses.
Liaoceratops is united with the other neoceratopsians on the basis of the
following characters-
26(1). Postorbital excluded from margin of laterotemporal fenestra.
28(1). Squamosal T-shaped, with postquadratic process.
37(1). Parieto-frontal contact depressed.
39(1). Frill fenestrated near posterior margin.
60(1). Surangular with distinct lateral ridge or shelf overhanging angular.
Bagaceratops and Protoceratops are united on the basis of the following
characters-
8(1). Premaxillary-maxillary suture extends through convex buccal process
at front of upper jaw.
30(2). Quadratojugal triangular in coronal section, but with slender
anterior prong articulating with jugal.
32(1). Elongate parasagittal process of the palatine.
61(1). Surangular with long ventral process overlapping angular, and
dentary-surangular and angular-surangular sutures form acute angle on
lateral face of mandible.
62(1). Posterior end of spenial with bifid overlap of angular.
Bainoceratops is united with Zuniceratops and the Ceratopsidae on the basis
of the following characters-
80(0). Dorsal vertebrae with flat articular zygapophyses.
81(3). Eight or more sacrals.
83(0). Caudal neural spines short and inclined.
This analysis only included characters that were in Makovicky's original
analysis.
Tereschenko & Alifanov state on pg. 294 that Bainoceratops "differs
appreciably from Protoceratops andrewsi and other protoceratopids with known
postcranial morphology." I think we see now why that is. It is important to
note that the authors seem to believe in a monophyletic Protoceratopidae
that includes the following taxa- Protoceratops, Microceratops,
Bagaceratops, Breviceratops, Asiaceratops, Udanoceratops, Kulceratops,
Archaeoceratops, Graciliceratops and Bainoceratops. They do not offer
support for such a grouping in their paper. Leptoceratops and Bainoceratops
share the following characters- concave anterior and flat posterior
intervertebral articulations in the presacral vertebrae; dorsal vertebrae
with flat articular zygapophyses; less indented edge of the elongate
synapophyseal facet that has a median crest; and a small angle of
inclination of the prezygapophyseal facet to the horizontal in the
posteriormost dorsal vertebra (10-15 degrees in Bainoceratops); and eight
sacral vertebrae. Udanoceratops and Bainoceratops share the following
characters- dorsal vertebrae with flat articular zygapophyses; caudal
vertebrae 7 with weakly projecting prezygapophyses with transversely
elongated facets; slightly projecting synapophyses of the posteriormost
dorsal vertebra; widely spaced zygapophyses; inclination and transverse
expansion of the prezygapophyseal facet in the posteriormost dorsal
vertebra; dorsal curvature of the lateral edge of the prezygapophyseal
facets of dorsal vertebra 9; extension of the prespinal crest between the
spinoprezygapophyseal crests almost to the edge of the interzygapophyseal
incisure in caudal vertebra 1; wider disconnection of the inferior edges of
the postzygapophyseal facets in the anterior caudal vertebrae; and deep
concave articular surfaces for chevrons on the centra of caudal vertebrae
10-11 & 18-19.
It is likely that in future analyses that include these characters, as well
as others, that Bainoceratops will be found to be a "leptoceratopsid", and
furthermore as the sistergroup to Udanoceratops, probably with Leptoceratops
right outside of that clade.
--+--Leptoceratops
`--+--Udanoceratops
`--Bainoceratops
Also, deleting Liaoceratops from the analysis seems to permit Zuniceratops
and Bainoceratops to switch places so that B. is now the sistergroup to the
Ceratopsidae based on the following two characters-
80(0). Dorsal vertebrae with flat articular zygapophyses.
81(3). Eight or more sacrals.
Zuniceratops is coded as unknown for both characters making it impossible to
definitely state that these characters could support such a relationships
since their presence or absence in Z. cannot be determined.
Just my two cents,
Nick Gardner
References-
P.J. Makovicky, (2001). A Montanoceratops cerorhynchus (Dinosauria:
Ceratopsia) Braincase from the Horseshoe Canyon Formation of Alberta. In
D.H. Tanke & K. Carpenter, (2001), Mesozoic Vertebrate Life: New Research
Inspired by the Paleontology of Philip J. Currie, pgs. 243-262
V.S. Tereschenko & V.R. Alifanov, (2003). Bainoceratops efremovi, a New
Protoceratopid Dinosaur (Protoceratopidae, Neoceratopsia) from the Bain-Dzak
Locality (South Mongolia). Paleontological Journal 37(3):293-302
X. Xu, P.J. Makovicky, X.-L. Wang, M.A. Norell, & H.-L. You, (2002). A
ceratopsian dinosaur from China and the early evolution of Ceratopsia.
Nature 416:314-317
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