Abstract Rioraja agassizii belongs to the monotypic genus and differs from other Riorajini species of Atlantoraja by shape anterior nasal flap, squamation, clasper skeleton, body measurements color pattern. Although R. is a well-known species, commonly captured in inshore waters southwestern Atlantic, its external morphology internal anatomy have never been fully described little known on intra...

Adaptive radiations, bouts of morphological divergence coupled with taxonomic proliferation, underpin biodiversity. The most widespread model of radiations assumes a single round, or 'early burst', of elevated phenotypic divergence followed by a decline in rates of change or even stasis. A vertebrate-specific model proposes separate stages: initial divergence in postcranial traits related to ha...

Historically, studies of pachycephalosaurs have recognized plesiomorphically flat-headed taxa and apomorphically domed taxa. More recently, it has been suggested that the expression of the frontoparietal dome is ontogenetic and derived from a flat-headed juvenile morphology. However, strong evidence to support this hypothesis has been lacking. Here we test this hypothesis in a large, stratigrap...

Cranial kinesis in birds is induced by muscles located caudal on the cranium. These forces are transferred onto the moveable parts of the skull via the Pterygoid-Palatinum Complex (PPC). This bony structure therefore plays an essential role in cranial kinesis. In palaeognathous birds the morphology of the PPC is remarkably different from that of neognathous birds and is thought to be related to...

Internal cranial anatomy is a challenging area to study in fossilized skulls because of small sample sizes and varied post-mortem preservational alterations. This difficulty has led to the lack of correspondence between results obtained from direct osteological observation and from more indirect reconstruction methods. This paper presents corroborating evidence from direct osteological observat...

Based on comparative anatomical, morphological, and phylogenetic considerations the potential of pterosaurs for cranial kinesis is assessed. Our investigation shows that whereas skeletally mature derived pterodactyloids have completely fused, rigid and doubtlessly akinetic skulls, skeletally immature derived pterodactyloids and more basal pterosaurs possess key features in the morphology of the...

BACKGROUND The foramen magnum is an important anatomical opening in the base of the skull through which the posterior cranial fossa communicates with the vertebral canal. It is also related to a number of pathological conditions including Chiari malformations, various tumours, and occipital dysplasias. The aim of the study was to evaluate the morphology of the foramen magnum in adult individual...

The present study entails descriptions of several well-preserved skulls from the pampathere species Holmesina floridanus, recovered from Pliocene localities in central Florida and housed in the collections of the Florida Museum of Natural History. Bone by bone descriptions have allowed detailed reconstructions of cranial morphology. Cranial foramina are described and illustrated in detail, and ...

Bats are one of the most diverse groups of mammals and have radiated into a wide variety of trophic niches. Accordingly, the cranial structure in bats is unusually variable among mammals and thought to reflect specializations for feeding and echolocation. However, recent analyses of cranial structure, feeding behavior and bite force across a wide range of bats suggest that correlations between ...

BACKGROUND Cat breeders observed a frequent occurrence of internal hydrocephalus in Persian cats with extreme brachycephalic head morphology. OBJECTIVE To investigate a possible relationship among the grade of brachycephaly, ventricular dilatation, and skull dysmorphologies in Persian cats. ANIMALS 92 Persian-, 10 Domestic shorthair cats. METHODS The grade of brachycephaly was determined ...