A fenestra (fenestration; pl.: fenestrae or fenestrations) is any small opening or pore, commonly used as a term in the biological sciences. [1] It is the Latin word for "window", and is used in various fields to describe a pore in an anatomical structure.
In morphology, fenestrae are found in cancellous bones, particularly in the skull. [2] In anatomy, the round window and oval window are also known as the fenestra rotunda and the fenestra ovalis. [3] In microanatomy, fenestrae are found in endothelium of fenestrated capillaries, enabling the rapid exchange of molecules between the blood and surrounding tissue. [4] The elastic layer of the tunica intima is a fenestrated membrane. In surgery, a fenestration is a new opening made in a part of the body to enable drainage or access.
In plant biology, the perforations in a perforate leaf are also described as fenestrae, and the leaf is called a fenestrate leaf. The leaf window is also known as a fenestra, [5] and is a translucent structure that transmits light, as in Fenestraria .
Examples of fenestrate structures in the fungal kingdom include the symmetrically arranged gaps in the indusium ("skirt") of the mushroom Phallus duplicatus , [6] and the thallus of the coral lichen Pulchrocladia retipora . [7]
In zoology, the trilobite Fenestraspis possessed extensive fenestrae in the posterior part of the body. [8] In the Paleognathae, there is an ilio–ischiatic fenestra.
Fenestrae are also used to distinguish the three types of amniote:
The ancestor of the amniotes is a primitive lizard, Hylonomus. From this reptile, three groups of amniotes would evolve: anapsids, diapsids, and synapsids. These broad groupings of amniotes are most easily differentiated by the presence and number of holes in the skull behind the eye socket. Those gaps, or holes, are called fenestrae, meaning "windows." The anapsids are the most primitive members of the group. They have a complete skull, with no gaps. ... The diapsids [including lizards, dinosaurs, and birds] have two fenestrae in their skulls, one directly behind the eye socket and one just slightly above. [160] The synapsids [including mammals] have just one fenestra, behind the eye socket. [9]
An anapsid is an amniote whose skull lacks one or more skull openings near the temples. Traditionally, the Anapsida are considered the most primitive subclass of amniotes, the ancestral stock from which Synapsida and Diapsida evolved, making anapsids paraphyletic. It is, however, doubtful that all anapsids lack temporal fenestra as a primitive trait, and that all the groups traditionally seen as anapsids truly lacked fenestra.
Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida. Unlike other amniotes, synapsids have a single temporal fenestra, an opening low in the skull roof behind each eye socket, leaving a bony arch beneath each; this accounts for the name "synapsid". The distinctive temporal fenestra developed about 318 million years ago during the Late Carboniferous period, when synapsids and sauropsids diverged, but was subsequently merged with the orbit in early mammals.
Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibious stem tetrapod ancestors during the Carboniferous period. Those of Amniota are defined as the smallest crown clade containing humans, the Greek tortoise, and the Nile crocodile.
Diapsids are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The earliest traditionally identified diapsids, the araeoscelidians, appeared about three hundred million years ago during the late Carboniferous period. All diapsids other than the most primitive ones in the clade Araeoscelidia are often placed into the clade Neodiapsida. The diapsids are extremely diverse, and include birds and all modern reptile groups, including turtles, which were historically thought to lie outside the group. All modern reptiles and birds are placed within the neodiapsid subclade Sauria. Although some diapsids have lost either one hole (lizards), or both holes, or have a heavily restructured skull, they are still classified as diapsids based on their ancestry. At least 17,084 species of diapsid animals are extant: 9,159 birds, and 7,925 snakes, lizards, tuatara, turtles, and crocodilians.
Sauropsida is a clade of amniotes, broadly equivalent to the class Reptilia, though typically used in a broader sense to also include extinct stem-group relatives of modern reptiles and birds. The most popular definition states that Sauropsida is the sibling taxon to Synapsida, the other clade of amniotes which includes mammals as its only modern representatives. Although early synapsids have historically been referred to as "mammal-like reptiles", all synapsids are more closely related to mammals than to any modern reptile. Sauropsids, on the other hand, include all amniotes more closely related to modern reptiles than to mammals. This includes Aves (birds), which are recognized as a subgroup of archosaurian reptiles despite originally being named as a separate class in Linnaean taxonomy.
The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians.
Mesosaurs were a group of small aquatic reptiles that lived during the early Permian period (Cisuralian), roughly 299 to 270 million years ago. Mesosaurs were the first known aquatic reptiles, having apparently returned to an aquatic lifestyle from more terrestrial ancestors. It is uncertain which and how many terrestrial traits these ancestors displayed; recent research cannot establish with confidence if the first amniotes were fully terrestrial, or only amphibious. Most authors consider mesosaurs to have been aquatic, although adult animals may have been amphibious, rather than completely aquatic, as indicated by their moderate skeletal adaptations to a semiaquatic lifestyle. Similarly, their affinities are uncertain; they may have been among the most basal sauropsids or among the most basal parareptiles.
Euryapsida is a polyphyletic group of sauropsids that are distinguished by a single temporal fenestra, an opening behind the orbit, under which the post-orbital and squamosal bones articulate. They are different from Synapsida, which also have a single opening behind the orbit, by the placement of the fenestra. In synapsids, this opening is below the articulation of the post-orbital and squamosal bones. It is now commonly believed that euryapsids are in fact diapsids that lost the lower temporal fenestra. Euryapsids are usually considered entirely extinct, although turtles might be part of the sauropterygian clade while other authors disagree. Euryapsida may also be a synonym of Sauropterygia sensu lato.
Parareptilia ("near-reptiles") is an extinct subclass or clade of basal sauropsids/reptiles, typically considered the sister taxon to Eureptilia. Parareptiles first arose near the end of the Carboniferous period and achieved their highest diversity during the Permian period. Several ecological innovations were first accomplished by parareptiles among reptiles. These include the first reptiles to return to marine ecosystems (mesosaurs), the first bipedal reptiles, the first reptiles with advanced hearing systems, and the first large herbivorous reptiles. The only parareptiles to survive into the Triassic period were the procolophonoids, a group of small generalists, omnivores, and herbivores. The largest family of procolophonoids, the procolophonids, rediversified in the Triassic, but subsequently declined and became extinct by the end of the period.
Fenestration or fenestrate may refer to:
Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit. These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly seen in the fossilized skulls of dinosaurs and other sauropsids. The major reptile group Diapsida, for example, is defined by the presence of two temporal fenestrae on each side of the skull. The infratemporal fenestra, also called the lateral temporal fenestra or lower temporal fenestra, is the lower of the two and is exposed primarily in lateral (side) view.
Eunotosaurus is an extinct genus of amniote, possibly a close relative of turtles. Eunotosaurus lived in the late Middle Permian and fossils can be found in the Karoo Supergroup of South Africa and Malawi. Eunotosaurus resided in the swamps of what is now southern Africa. Its ribs were wide and flat, forming broad plates similar to a primitive turtle shell, and the vertebrae were nearly identical to those of some turtles. Accordingly, it is often considered as a possible transitional fossil between turtles and their prehistoric ancestors. However, it is possible that these turtle-like features evolved independently of the same features in turtles, since other anatomical studies and phylogenetic analyses suggest that Eunotosaurus may instead have been a parareptile, an early-diverging neodiapsid unrelated to turtles, or a synapsid.
Heleosaurus scholtzi is an extinct species of basal synapsids, known as pelycosaurs, in the family of Varanopidae during the middle Permian. At first H. scholtzi was mistakenly classified as a diapsid. Members of this family were carnivorous and had dermal armor, and somewhat resembled monitor lizards. This family was the most geologically long lived, widespread, and diverse group of early amniotes. To date only two fossils have been found in the rocks of South Africa. One of these fossils is an aggregation of five individuals.
The skull roof or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium.
Australothyris is an extinct genus of basal procolophonomorph parareptile known from the Middle Permian of Tapinocephalus Assemblage Zone, South Africa. The type and only known species is Australothyris smithi. As the most basal member of Procolophonomorpha, Australothyris helped to contextualize the origin of this major parareptile subgroup. It has been used to support the hypotheses that procolophonomorphs originated in Gondwana and ancestrally possess temporal fenestrae, due to its large and fully enclosed temporal fenestra and South African heritage. It also possessed several unique features, including a high tooth number, long postfrontal, small interpterygoid vacuity, and a specialized interaction between the stapes and quadrate.
Reptiles arose about 320 million years ago during the Carboniferous period. Reptiles, in the traditional sense of the term, are defined as animals that have scales or scutes, lay land-based hard-shelled eggs, and possess ectothermic metabolisms. So defined, the group is paraphyletic, excluding endothermic animals like birds that are descended from early traditionally-defined reptiles. A definition in accordance with phylogenetic nomenclature, which rejects paraphyletic groups, includes birds while excluding mammals and their synapsid ancestors. So defined, Reptilia is identical to Sauropsida.
Pantestudines or Pan-Testudines is the proposed group of all reptiles more closely related to turtles than to any other living animal. It includes both modern turtles and all of their extinct relatives. Pantestudines with a complete shell are placed in the clade Testudinata.
Pappochelys is an extinct genus of diapsid reptile possibly related to turtles. The genus contains only one species, Pappochelys rosinae, from the Middle Triassic of Germany, which was named by paleontologists Rainer Schoch and Hans-Dieter Sues in 2015. The discovery of Pappochelys provides strong support for the placement of turtles within Diapsida, a hypothesis that has long been suggested by molecular data, but never previously by the fossil record. It is morphologically intermediate between the definite stem-turtle Odontochelys from the Late Triassic of China and Eunotosaurus, a reptile from the Middle Permian of South Africa.
Ascendonanus is an extinct genus of varanopid amniote from the Early Permian of Germany. It is one of the earliest specialized arboreal (tree-living) tetrapods currently known and outwardly resembled a small lizard. The animal was about 40 cm long, with strongly curved claws, short limbs, a slender, elongated trunk, and a long tail. It would have preyed on insects and other small arthropods.
Taytalura is an extinct genus of lepidosauromorph reptile from the Late Triassic of Argentina. It contains a single species, Taytalura alcoberi, which is based on a well-preserved skull from the fossiliferous Ischigualasto Formation. As a lepidosauromorph, Taytalura is a distant relative of modern lepidosaurs such as sphenodontians and squamates. Taytalura did not belong to any group of modern lepidosaurs, since it bears unique features, such as unfused bones in the skull roof and teeth which all sit loosely in a deep groove without sockets. Regardless, Micro-CT scanning reveals features of the skull previously only seen in rhynchocephalians. This suggests that the ancestral condition of the skull in lepidosaurs was more similar to sphenodonts than to squamates.
