Forum Dinozaury.com

Technical Session III (Wednesday, October 30, 2013, 3:15 PM)
THE SMALLEST, ARTICULATED CERATOPSID (DINOSAURIA)

CURRIE, Philip, University of Alberta, Edmonton, AB, Canada, T6G 2E9;
HOLMES, Robert, University of Alberta, Edmonton, AB, Canada; RYAN,
Michael, Cleveland Museum of Natural History, Cleveland, OH, United
States; COY, Clive, University of
Alberta, Edmonton, AB, Canada; KOPPELHUS, Eva, University of Alberta,
Edmonton, AB, Canada




The smallest known articulated ceratopsid skeleton (lacking only the
forelimbs) is a juvenile chasmosaurine that was collected in 2010 from
the lowermost part of the Dinosaur Park Formation in Dinosaur
Provincial Park, Alberta. At 1.5 m in total length, it falls below the
size range of even adult basal neoceratopsians and large
psittacosaurids. Cranial bones have striated, porous bone texture;
many are coossified despite its small size. The frill is relatively
short and narrow. The back of the frill is rectangular, lacks a
posterior embayment, and is relatively narrower than those of either
equivalent-sized basal neoceratopsians or adult ceratopsids. There are
no cranial epiossifications, and the squamosal is capped at the
posterolateral corner by the parietal. The margins of the elongate
squamosals are thick and scalloped. Narrow and elongate openings may
represent the parietal fenestrae, and there is a pronounced midline
sagittal crest that extends almost to the back of the frill. The
preserved short, knoblike postorbital horn has a round base and there
is no development of sinuses from below. An incipient horncore is
present on the nasals over the posterior one-half of the external
nares. There are 18 maxillary tooth positions, which is at least four
more than in any similar-sized basal neoceratopsians, but is fewer
than what is found in more mature ceratopsids. All of the cranial
features are consistent with its identification as Chasmosaurus sp.
Postcranially, skin on the flank of the body comprised a basement of
pebbles with large feature scales. The syncervical is composed of
three fused vertebrae. There are 32 articulated caudals, of which the
fifth to twentieth appear to have short, robust, free caudal ribs. The
narrow pelvis suggests the body was tall and narrow. Ossified tendons
are present in the neck and trunk. The pedal unguals are broad but
taper acutely. Ontogenetic hind limb proportions scale isometrically,
and as in more mature ceratopsids, the tibia/fibula and metatarsals
are relatively short in contrast with those of more basal
ceratopsians. Recovery in the phylogenetic analysis of the specimen as
a basal chasmosaurine is a reflection of juvenile characters that have
a significant impact on character coding. For example, as in basal
ceratopsians the palpebral is not fully incorporated into the orbital
rim. Those characters used in phylogenetic analyses of ceratopsids
that are size or age-dependent can now be identified, redefined to be
more useful, or dropped.

Dino pisze:Torosaurus jednak różny od Triceratops.

Utahraptor pisze:Moją uwagę przykuł kształt nozdrzy i sąsiedniego okna oraz układ beleczek i blaszek w nich i między nimi.

Ag.Ent pisze:Tereschenko V.S., Singer T. 2013. Structural features of neural spines of the caudal vertebrae of protoceratopoids (Ornithischia: Neoceratopsia). Paleontological Journal 47: 618-630. http://dx.doi.org/10.1134/S0031030113060105.

Gratuluję! (choć muszę przyznać, że z wnioskami nie do końca się zgadzam).

Dino pisze:Wyrostek na głowie edmontozaura:
http://1.bp.blogspot.com/-AaHsjgayq1s/U ... uction.jpg

Phil R. Bell, Federico Fanti, Philip J. Currie & Victoria M. Arbour (2013)
A Mummified Duck-Billed Dinosaur with a Soft-Tissue Cock’s Comb.
Current Biology (advance online publication)
doi: 10.1016/j.cub.2013.11.008
http://www.cell.com/current-biology/abs ... 13)01394-8