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The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. [1] In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. [2] The bone forms an ancestral component of the dermal roof and is typically thin compared to other skull bones. [3]
The skull proper was joined by the bones of the operculum. The skull itself was composed rather loosely, with a joint between the bones covering the brain and the snout. The skull roof in lungfish is composed of a number of bony plates that are not readily compared to those found in early amphibians. [4]
Triadobatrachus is an extinct genus of salientian frog-like amphibians, including only one known species, Triadobatrachus massinoti. It is the oldest member of the frog lineage known, and an excellent example of a transitional fossil. It lived during the Early Triassic about 250 million years ago, in what is now Madagascar.
Kermit the Frog meet Kermitops gratus, the most recent ancient amphibian to be identified after examination of a tiny fossilized skull that once sat unstudied in the Smithsonian fossil collection ...
The skull of Triadobatrachus is frog-like, being broad with large eye sockets, but the fossil has features diverging from modern frogs. These include a longer body with more vertebrae . The tail has separate vertebrae unlike the fused urostyle or coccyx in modern frogs.
From top to bottom (A) a skull of an Anapsid, (B) a Synapsid (stem-mammal) skull, and (C) a Diapsid skull. [a] Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles.
The skull of the dromaeosaurid dinosaur Dromaeosaurus, with the quadratojugal (light blue) labelled. Several Triassic reptiles reacquire the lower temporal bar, albeit with the jugal forming most of the bar's length. In these reptiles, the quadratojugal is a small L- or T-shaped bone at the rear edge of the skull.
Vieraella is an extinct genus of frogs from the Lower Jurassic (Early Pliensbachian to Toarcian) Roca Blanca Formation of Argentina, and one of the oldest true frogs known. . This genus is known by a single exceptionally well-preserved specimen, P.V.L. 2188, with at least eight presacrals vertebrae, free ribs, ulna and radius not fused, bony skull with some discoglossid charac