page_title: Cynosaurus
section_title: Cranium
hierarchical_section_title: Cynosaurus / Description / Cranium
caption_attribution_description: Identifier: waterreptilesofp1914will Title: Water reptiles of the past and present Year: 1914 (1910s) Authors: Williston, Samuel Wendell, 1851-1918 Subjects: Aquatic reptiles Publisher: Chicago, Ill., The University of Chicago Press Contributing Library: Boston Public Library Digitizing Sponsor: Boston Public Library View Book Page: Book Viewer About This Book: Catalog Entry View All Images: All Images From Book Click here to view book online to see this illustration in context in a browseable online version of this book. Text Appearing Before Image: heir mates or with contiguousbones. The crocodile has at leasttwo pairs of bones which havedisappeared in turtles. On theother hand, the turtle has at leastone pair of free bones which havebeen fused with adjacent bones inthe crocodiles, and one pair thatis fused which is free in the latter.The lizard has one pair of bonesthat has been wholly wanting inother reptiles for millions of years,while on the other hand it has lostsome bones that are present in all other modern reptiles. Thefour parts of the occipital bone of mammals, basioccipital, exoccipi-tals, and supraoccipital, are almost invariably free and there is asingle occipital condyle, except in the Theriodontia. In this reduction or fusion of parts, or in addition thereto, therehas been a general lightening-up of the whole skull-structure inreptiles from the rather massive and protected form of the olderto the lighter, less protected, and more fragile type of thelater ones, since speed, greater agility, better sense organs, and Text Appearing After Image: Fig. 6.—Labidosaurus, a cotylosaur.Skull from above: pm, premaxilla; n,nasal; m, maxilla; /, lacrimal; p, pre-frontal; fr, frontal; pf, postfrontal;po, postorbital; j, jiigal; pa, parietal;sq, squamosal; ds, dermosupraoccipi-tal; pf, parietal foramen. THE SKELETON OF REPTILES 23 doubtless greater brain power have rendered unnecessary or uselesstrie older kinds, just as modern methods and modern arms haverendered useless the coat of mail of the Middle Ages. The old reptiles had a continuous covering or roof for the skull,pierced only by the openings for the nostrils in front—the nares—the orbits for the eyes near the middle, and a smaller median open-ing back of them for the so-called pineal eye. The temporalregion, that is, the region back of the orbits on each side, wascompletely roofed over by bone for the support and protection ofthe jaw muscles. In later reptiles this region has been lightened. Note About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.
context_page_description: Cynosaurus is an extinct genus of cynodonts. Remains have been found from the Dicynodon Assemblage Zone in South Africa. Cynosaurus was first described by Richard Owen in 1876 as Cynosuchus suppostus. Cynosaurus has been found in the late Permian period. Cyno- is derived from the Greek word kyon for dog and –sauros in Greek meaning lizard.
context_section_description: The septomaxilla is the flat bridge that divides the nasal into upper and lower (Van den Brandt et al., 2018). The nasal is broader posteriorly than anteriorly (Van den Brandt et al., 2018). On the surface of the maxilla there are many small nutritive foramina forming two horizontal parallel lines (Van den Brandt et al., 2018). For the premaxilla there is a gap along the midline between the premaxilla and the palatal processes (Van den Brandt et al., 2018). The vomer is unpaired and tapers and reaches a point sharp (Van den Brandt et al., 2018). The vomer also doesn't reach the pterygoid posteriorly (Van den Brandt et al., 2018). Micro-CT scans allows internal structures of fossil skulls to be observed (Benoit et al., 2017). From micro-CT scans, a pair of ossification orbitosphenoid were observed in four specimens of Cynosaurus (Benoit et al., 2017). In orbitosphenoid consisted of two thin plate-like structures appear to articulate ventromedially and in cross section, it appears to be in an U-shape (Benoit et al., 2017).
  The rapid evolution of the masseter insertion area is able to show early diversification of early Cynodonts (Botha et al., 2007). In Procynosuchus and Dvinia the location of masseteric fossa high on the coronoid process is seen as an initial stage of differentiation of masseter (Botha et al., 2007). In Cynosaurus and Nanictosaurus the extension of masseteric fossa is to the base of the dentary (Botha et al., 2007).
caption: Parietal foramen (labeled pf in image) of marine reptile
exif: {}