Mammals, which are synapsids, possess no fenestral openings in the skull, as the trait has been modified. They do, though, still have the temporal orbit (which resembles an opening) and the temporal muscles. It is a hole in the head and is situated to the rear of the orbit behind the eye.
Does the temporal fenestra still exist?
EDIT: Two years after posting this, /u/mattfen93messaged me with a knowledgable answer, explaining that the temporal fenestra basically still exists in all extant mammals, including humans. His response is below:
Why do temporal fenestrae always occur between bones?
Along these lines, temporal fenestrae and other cranial fenestrae associated with the jaw adductor musculature always occur between bones and never within a single bone. Essentially, the sides of fenestrae, that in time usually approach a circular geometry, afford the tendons a low angle insertion and greater area for attachment.
What are the upper and lower temporal fenestrae called?
The upper temporal fenestrae are also known as the supratemporal fenestrae, and the lower temporal fenestrae are also known as the infratemporal fenestrae. The presence and morphology of the temporal fenestra is critical for taxonomic classification of the synapsids, of which mammals are part.
Where is the fenestra on the skull?
The location of the old fenestra is still visible between the zygomatic arch, the orbit, and the dorsal part of the skull, but it is no longer a hole in the skull. A few taxa not related to Synapsida have also acquired a lower temporal fenestra. These include lanthanosuchids (Ivakhnenko, 1980) and some millerettids (members of Anapsida).
Where is the temporal fenestra in humans?
(a) Morphology Temporal fenestrae are temporal openings that are completely surrounded by bone. They always form within the sutural contact of two or more temporal bones. An infratemporal fenestra forms in the 'cheek' region of the skull and is ventrally always bordered by a lower temporal bar (i.e. zygomatic arch).
Do humans have synapsid skulls?
Humans are synapsids, as well. Most mammals are viviparous and give birth to live young rather than laying eggs with the exception being the monotremes.
How many temporal fenestrae are there?
Three basic patterns of fenestration are recognized. The diapsid condition has two temporal fenestrae, one above the other on either side of the skull (Figure 1.9b). These are the supratemporal (upper or dorsal) fenestra and the infratemporal (lower or ventral) fenestra. This is the condition present in most reptiles.
What do temporal fenestra do?
The large post-temporal fenestrae (large holes in the back of the skull) of turtles allow the jaw musculature to expand beyond the confines of the adductor chamber.
What type of skull do humans have?
The skull is a bone structure that forms the head in vertebrates. It supports the structures of the face and provides a protective cavity for the brain. The skull is composed of two parts: the cranium and the mandible....SkullMeSHD012886TA98A02.1.00.001TA2406Anatomical terminology4 more rows
Are humans therapsids?
Therapsids were "mammal-like" reptiles and are ancestors to the mammals, including humans, found today. One group of therapsids is called dicynodonts.
Do mammals have temporal holes?
Mammals, which are synapsids, possess no fenestral openings in the skull, as the trait has been modified. They do, though, still have the temporal orbit (which resembles an opening) and the temporal muscles. It is a hole in the head and is situated to the rear of the orbit behind the eye.
Are mammals diapsids?
Most reptiles and all birds are diapsids whereas most mammals are synapsids.
Do amphibians have temporal fenestra?
As we saw earlier, the antorbital fenestra comes and goes in several reptiles. So does the lateral temporal fenestra. Amphibians (non-amniote tetrapods) typically do not have skull fenestrae.
What fenestrae did dinosaurs possess?
In theropod dinosaurs, the antorbital fenestra is the largest opening in the skull. Systematically, the presence of the antorbital fenestra is considered a synapomorphy that unites tetanuran theropods as a clade.
How many temporal fenestrae does a diapsid have?
two temporal fenestraeThe diapsid condition has two temporal fenestrae, one above the other on either side of the skull (Figure 1.9b). These are the supratemporal (upper or dorsal) fenestra and the infratemporal (lower or ventral) fenestra. This is the condition present in most reptiles.
How many temporal fenestrae do diapsids like non turtle reptiles have?
The diapsid condition of the skull is seen in "non-turtle" extant reptiles and in their extinct relatives. In these animals, two temporal fenestrae exist on either side of the skull.
How do temporal fenestrae form?
Formation of temporal fenestrae proceeds by the opening of sutures between bones or the embryological failure to close sutures. Along these lines, temporal fenestrae and other cranial fenestrae associated with the jaw adductor musculature always occur between bones and never within a single bone. Essentially, the sides of fenestrae, that in time usually approach a circular geometry, afford the tendons a low angle insertion and greater area for attachment. Through dissection, it is also seen that other fenestrae in the reptilian skull and jaw, such as the palatine and external mandibular fenestrae, are associated with musculus pterygoideus and m. intramandibularis, respectively. Temporal fenestrae formation has little to do with space needed for muscle bulging during contraction, but are rather correlated with the phylogenetic expansion of jaw adductor size and thus force production. Fenestral patterns can be used systematically because they represent muscle-bone complexes and thus complex character states.
What is the temporal region of a tetrapod?
The morphology of the temporal region in the tetrapod skull traditionally has been a widely discussed feature of vertebrate anatomy. The evolution of different temporal openings in Amniota (mammals, birds, and reptiles), Lissamphibia (frogs, salamanders, and caecilians), and several extinct tetrapod groups has sparked debates on the phylogenetic, developmental, and functional background of this region in the tetrapod skull . This led most famously to the erection of different amniote taxa based on the number and position of temporal fenestrae in their skulls. However, most of these taxa are no longer recognised to represent natural groupings and the morphology of the temporal region is not necessarily an adequate trait for use in the reconstruction of amniote phylogenies. Yet, new fossil finds, most notably of parareptiles and stem-turtles, as well as modern embryological and biomechanical studies continue to provide new insights into the morphological diversity of the temporal region. Here, we introduce a novel comprehensive classification scheme for the various temporal morphotypes in all Tetrapoda that is independent of phylogeny and previous terminology and may facilitate morphological comparisons in future studies. We then review the history of research on the temporal region in the tetrapod skull. We document how, from the early 19th century with the first recognition of differences in the temporal region to the first proposals of phylogenetic relationships and their assessment over the centuries, the phylogenetic perspective on the temporal region has developed, and we highlight the controversies that still remain. We also compare the different functional and developmental drivers proposed for the observed morphological diversity and how the effects of internal and external factors on the structure of the tetrapod skull have been interpreted.
What are the amniotes?
Amniotes include mammals, reptiles and birds , representing 75% of extant vertebrate species on land. They originated around 318 million years ago in the early Late Carboniferous and their early fossil record is central to understanding the expansion of vertebrates in terrestrial ecosystems. We present a phylogenetic hypothesis that challenges the widely accepted consensus about early amniote evolution, based on parsimony analysis and Bayesian inference of a new morphological dataset. We find a reduced membership of the mammalian stem lineage, which excludes varanopids. This implies that evolutionary turnover of the mammalian stem lineage during the Early–Middle Permian transition (273 million years ago) was more abrupt than has previously been recognized. We also find that Parareptilia are nested within Diapsida. This suggests that temporal fenestration, a key structural innovation with important functional implications, evolved fewer times than generally thought, but showed highly variable morphology among early reptiles after its initial origin. Our phylogeny also addresses controversies over the affinities of mesosaurids, the earliest known aquatic amniotes, which we recover as early diverging parareptiles. A new amniote phylogeny excludes varanopids as stem-line mammals, nests Parareptilia within Diapsida and suggests that temporal fenestration evolved fewer times than previously thought.
Where is the Procolophon found?
The specific composition of the genus Procolophon in Brazil, South Africa and Antarctica is discussed in the light of new data. It is found that P. pricei and P. brasiliensis, two species described from Brazil, fit within the pattern of ontogenetic variation of the type species P. trigoniceps, and they are here considered junior synonyms. The South African species P. laticeps, characterized by the presence of a temporal fenestra, is no longer considered valid. The peculiar temporal openings of this species are regarded here as an anomalous condition without taxonomic significance. The only complete skull known from Antarctica shows a unique feature consisting of an elliptical depression in the palate. The interpretation of this structure is ambiguous because it may also be attributable to individual variation, and this specimen is provisionally kept within P. trigoniceps. Therefore, only the type species, P. trigoniceps, is recognized in Gondwana. This species occupies a wide geographic range, from the Paraná Basin to the Transantarctic Mountains.
Is temporal opening a weak indication for higher taxon interrelationship?
Compared to historical classifications, there is a common consensus that temporal openings are only a weak indication for higher taxon interrelationship, although it can be informative on lower taxonomic level. Here, I present a rather morphofunctional categorization of temporal openings and provide an ontogenetic explanation on their evolutionary origins.
What is the antorbital fenestra?
An antorbital fenestra (plural: fenestrae) is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with archosauriforms, first appearing during the Triassic Period.
Which sinus is the largest opening in the antorbital fenestra?
Although crocodylians walled over their antorbital fenestra, they still retain an antorbital sinus. In theropod dinosaurs, the antorbital fenestra is the largest opening in the skull.
