[Paleontology • 2015]
Mosaiceratops azumai • A Psittacosaurid-like Basal Neoceratopsian from the Upper Cretaceous of central China and Its Implications for Basal Ceratopsian Evolution
Mosaiceratops azumai
Zheng, Jin & Xu, 2015
Abbreviations: a, astragalus; boc,
basioccipital; c, calcaneum; cav, caudal vertebra; ch, chevron; cv,
cervical vertebra; dr, dorsal rib; dv, dorsal vertebra; f, frontal; fem,
femur; fl, fibula; h, humerus; il, ilium; is, ischium; L, left; mt,
metatarsal; ph, phalanx/phalanges; po, postorbital; R, right; sk, skull;
sq, squamosal; t, tibia; td, tendon; ?, undiagnostic remains.
doi: 10.1038/srep14190
|
Abstract
Psittacosauridae (parrot-beaked dinosaurs) represents the first major
radiation of ceratopsians (horned dinosaurs). However, psittacosaurids
are divergent from the general morphology found in other ceratopsians,
and this has resulted in their uncertain systematic position among
ceratopsians. Here we describe a new basal neoceratopsian dinosaur, Mosaiceratops azumai gen. et sp. nov.
based on a partial semi-articulated skeleton recovered from the Upper
Cretaceous Xiaguan Formation of Neixiang County, Henan Province, China.
Although our phylogenetic analysis supports this taxon as the most basal
neoceratopsian, Mosaiceratops exhibits many features previously
considered unique to the Psittacosauridae among the basal Ceratopsia.
These include a relatively highly positioned external naris, a
proportionally large premaxilla, the nasal extending ventral to the
external naris, slender postorbital and temporal bars, a large notch
between the basal tubera, and the edentulous premaxilla. Thus, the
discovery of Mosaiceratops reduces the morphological disparity between
the Psittacosauridae and other basal ceratopsians. Character
optimization suggests that basal neoceratopsians have re-evolved
premaxillary teeth; a major reversal previously unknown in any dinosaur
clade. The new specimen also highlights the mosaic nature of evolution
among early ceratopsians and supports the phylogenetic hypothesis that
the Psittacosauridae is a relatively derived clade, rather than the most
basal group of the Ceratopsia.
Systematic palaeontology
Dinosauria Owen, 1842
Ornithischia Seeley, 1887
Ceratopsia Marsh, 1890
Neoceratopsia Sereno, 1986
Mosaiceratops azumai gen. et sp. nov.
Etymology: The generic name Mosaiceratops (“mosaic ceratopsian”) is a contraction of the Latin terms “mosaicus” and “ceratops”
in reference to the specimen’s unique (mosaic) combination of
characters that were previously considered diagnostic of basal
ceratopsians, psittacosaurids, or basal neoceratopsians. The specific
name honors Dr. Yoichi Azuma from Fukui Prefectural Dinosaur
Museum, who co-organized and participated in several dinosaur
expeditions in China. One of those expeditions led to the discovery of
the basal neoceratopsian Archaeoceratops.
Figure 3: Temporal calibration of the single most parsimonious tree produced by phylogenetic analysis.
doi: 10.1038/srep14190
|
Locality and horizon: Upper Cretaceous (lower-middle Turonian—middle Campanian), Xiaguan Formation, Neixiang County, Henan Province, China.
Wenjie Zheng, Xingsheng Jin and Xing Xu. 2015. A Psittacosaurid-like
Basal Neoceratopsian from the Upper Cretaceous of central China and Its
Implications for Basal Ceratopsian Eevolution. Scientific Reports. 5, 14190. doi: 10.1038/srep14190
Nenhum comentário:
Postar um comentário
Observação: somente um membro deste blog pode postar um comentário.