BACKGROUND The holotype and only specimen of the chasmosaurine ceratopsid dinosaur 'Nedoceratops hatcheri' has been the source of considerable taxonomic debate since its initial description. At times it has been referred to its own genus while at others it has been considered synonymous with the contemporaneous chasmosaurine Triceratops. Most recently, the debate has focused on whether the spec...

Frogs have one of the most extreme metamorphoses among vertebrates. How did this metamorphosis evolve? By combining the methods previously proposed by Mabee and Humphries (1993) and Velhagen (1997), I develop a phylogenetic method suited for rigorous analysis of this question. In a preliminary analysis using 12 transformation sequence characters and 36 associated event sequence characters, all ...

The orbits are paired structures, located on the anterior part of the face. Morphologically, each orbit is a four sided pyramid with a posterior apex and anterior base. In the orbit, all openings are arranged around the base, apex or between the orbital walls. An anatomical characteristic of the orbit is that structures are arranged in groups of seven: there are seven bones, seven intraorbital ...

Th e osteology of Gorgasia punctata is described, figured , and compared with that of other congrids . Gorgasia is clearly referable to the subfamily Heterocongrinae. The heterocongrin es agree with the Congridae in several important featu res, and do not differ in fund amental respects. Th erefore, the group is recognized as a subfamily of the Congridae. Gorgasia is the most primit ive heteroc...

BACKGROUND In the Early Cretaceous Jehol Biota, the toothless pterosaurs flourished with the chaoyangopterids and tapejarids playing a key role in understanding the early diversity and evolution of the Azhdarchoidea. Unlike the more diverse tapejarids, the rarer chaoyangopterids are characterized by a long and low rostrum, supporting a close relationship with the huge azhdarchids. Unfortunately...

study of the osteological development in fishes is important from fisheries, biology and aquaculture points of views. it can be used as an early bio-indicator of non-optimal rearing conditions. the caspian roach, rutilus caspicus is a native cyprinid fish of the caspian sea that its artificial propagation has fulfilled in hatcheries to recruit its natural stocks. hence, this study was conducted...