An endocast is the internal cast of a hollow object, often referring to the cranial vault in the study of brain development in humans and other organisms. [1] Endocasts can be artificially made for examining the properties of a hollow, inaccessible space, or they may occur naturally through fossilization.
Endocasts of the inside of the neurocranium (braincase) are often made in paleoanthropology to study brain structures and hemispheric specialization in extinct human ancestors. While an endocast can not directly reveal brain structure, [1] it can allow scientists to gauge the size of areas of the brain situated close to the surface, notably Wernicke's and Broca's areas, responsible for interpreting and producing speech. [2]
Traditionally, the casting material is some form of rubber or rubber-like material. The openings to the brain cavity, except for the foramen magnum , are closed, and the liquid rubber is slushed around in the empty cranial vault and then left to set. The resulting hollow sphere can then be drained of air like a balloon and pulled out through the foramen magnum. [3] Rubber endocasts like these were the standard practice until the end of the 20th century and are still used in some fields. However, scientists are increasingly utilizing computerized tomography scanning technology to create digital endocasts in order to avoid risking damage to valuable specimens. [4]
Natural cranial endocasts are also known. The famous Taung Child, the first Australopithecus found, consists of a natural endocast connected to the facial portion of the skull. It was the shape of the brain that allowed Raymond Dart to conclude that the fossil was that of a human relative rather than an extinct ape. [5]
Mammal endocasts are particularly useful, as they resemble the fresh brain with the dura mater in place. Such "fossil brains" are known from several hundred different mammal species. [1] More than a hundred natural casts of the cranial vault of Bathygenys (a small merycodont) alone are known, some having identifiable features down to the major gyri. [6] Several hundred casts of various dinosaurs are known, among them a Tyrannosaurus brain vault, showing the animal had limited intelligence and a well-developed sense of smell. [7] The oldest known natural cranial endocast is a fossil fish brain from a Holocephalan, some 300 million years old. [8]
Endocast fossils from animals with shells that easily disintegrate or dissolve can often be encountered free from their mold fossil, like the aragonite shells of certain molluscs and the tests of sea urchins. A frequently occurring form is the internal mold of brachiopods and bivalves. In the quite symmetrical genus brachiopod Pentamerus , the endocast resembles a vulva, giving these fossils the name Schamstein or Mutterstein ("shame stone" or "mother stone") in German, while some bivalve endocasts are traditionally known as heart-of-stone or bull hearts in Britain. [9] The "Venus of Svinesund", an early Mesolithic Venus figurine from Norway, is a re-worked Ordovician bivalve endocast. [10] Endocasts are also known to develop from snail shells and sea urchins, and even from the stomach hollow of jellyfish, a group that rarely leaves fossil traces.
Artificial endocasts are sometimes made from blood vessels for medical or anatomical reasons. The blood vessel of an organ (e.g. brain or liver) is injected with a resin. When it is set, the organ itself is dissolved, leaving a three-dimensional image of the blood supply to the organ.
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, these two parts are the neurocranium and the viscerocranium that includes the mandible as its largest bone. The skull forms the anterior-most portion of the skeleton and is a product of cephalisation—housing the brain, and several sensory structures such as the eyes, ears, nose, and mouth. In humans these sensory structures are part of the facial skeleton.
The foramen magnum is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull. The spinal cord, an extension of the medulla oblongata, passes through the foramen magnum as it exits the cranial cavity. Apart from the transmission of the medulla oblongata and its membranes, the foramen magnum transmits the vertebral arteries, the anterior and posterior spinal arteries, the tectorial membranes and alar ligaments. It also transmits the accessory nerve into the skull.
Hadrosaurids, or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which includes genera such as Edmontosaurus and Parasaurolophus, was a common group of herbivores during the Late Cretaceous Period. Hadrosaurids are descendants of the Upper Jurassic/Lower Cretaceous iguanodontian dinosaurs and had a similar body layout. Hadrosaurs were among the most dominant herbivores during the Late Cretaceous in Asia and North America, and during the close of the Cretaceous several lineages dispersed into Europe, Africa, South America and Antarctica.
Encephalization quotient (EQ), encephalization level (EL), or just encephalization is a relative brain size measure that is defined as the ratio between observed and predicted brain mass for an animal of a given size, based on nonlinear regression on a range of reference species. It has been used as a proxy for intelligence and thus as a possible way of comparing the intelligence levels of different species. For this purpose, it is a more refined measurement than the raw brain-to-body mass ratio, as it takes into account allometric effects. Expressed as a formula, the relationship has been developed for mammals and may not yield relevant results when applied outside this group.
The Taung Child is the fossilised skull of a young Australopithecus africanus. It was discovered in 1924 by quarrymen working for the Northern Lime Company in Taung, South Africa. Raymond Dart described it as a new species in the journal Nature in 1925.
The posterior cranial fossa is the part of the cranial cavity located between the foramen magnum, and tentorium cerebelli. It is formed by the sphenoid bones, temporal bones, and occipital bone. It lodges the cerebellum, and parts of the brainstem.
The size of the brain is a frequent topic of study within the fields of anatomy, biological anthropology, animal science and evolution. Brain size is sometimes measured by weight and sometimes by volume. Neuroimaging intelligence testing can be used to study the volumetric measurements of the brain. Regarding "intelligence testing", a question that has been frequently investigated is the relation of brain size to intelligence. This question is controversial and will be addressed further in the section on intelligence. The measure of brain size and cranial capacity is not just important to humans, but to all mammals.
Dinilysia is an extinct genus of snake from the Late Cretaceous (Coniacian) of South America. Dinilysia was a relatively large ambush predator, measuring approximately 2 m (6.6 ft) long. The skull morphology of Dinilysia is similar to boids, suggesting that it was able to consume large prey. Living in a desert-like environment, Dinilysia is likely a terrestrial or a semi-fossorial animal.
This article describes the anatomy of the head and neck of the human body, including the brain, bones, muscles, blood vessels, nerves, glands, nose, mouth, teeth, tongue, and throat.
The phylogenetic classification of invertebrates remains a work-in-progress. The taxonomy of commonly fossilized invertebrates combines both traditional (old) and modern (21st-century) paleozoological terminology.
The endocranium in comparative anatomy is a part of the skull base in vertebrates and it represents the basal, inner part of the cranium. The term is also applied to the outer layer of the dura mater in human anatomy.
Brachiopods, phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major categories are traditionally recognized, articulate and inarticulate brachiopods. The word "articulate" is used to describe the tooth-and-groove structures of the valve-hinge which is present in the articulate group, and absent from the inarticulate group. This is the leading diagnostic skeletal feature, by which the two main groups can be readily distinguished as fossils. Articulate brachiopods have toothed hinges and simple, vertically-oriented opening and closing muscles. Conversely, inarticulate brachiopods have weak, untoothed hinges and a more complex system of vertical and oblique (diagonal) muscles used to keep the two valves aligned. In many brachiopods, a stalk-like pedicle projects from an opening near the hinge of one of the valves, known as the pedicle or ventral valve. The pedicle, when present, keeps the animal anchored to the seabed but clear of sediment which would obstruct the opening.
In brain anatomy, the lunate sulcus or simian sulcus, also known as the sulcus lunatus, is a fissure in the occipital lobe variably found in humans and more often larger when present in apes and monkeys. The lunate sulcus marks the transition between V1 and V2.
Paleoneurobiology is the study of brain evolution by analysis of brain endocasts to determine endocranial traits and volumes. Considered a subdivision of neuroscience, paleoneurobiology combines techniques from other fields of study including paleontology and archaeology. It reveals specific insight concerning human evolution. The cranium is unique in that it grows in response to the growth of brain tissue rather than genetic guidance, as is the case with bones that support movement. Fossil skulls and their endocasts can be compared to each other, to the skulls and fossils of recently deceased individuals, and even compared to those of other species to make inferences about functional anatomy, physiology and phylogeny. Paleoneurobiology is in large part influenced by developments in neuroscience as a whole; without substantial knowledge about current functionality, it would be impossible to make inferences about the functionality of ancient brains.
Ankylopollexia is an extinct clade of ornithischian dinosaurs that lived from the Late Jurassic to the Late Cretaceous. It is a derived clade of iguanodontian ornithopods and contains the subgroup Styracosterna. The name stems from the Greek word, “ankylos”, mistakenly taken to mean stiff, fused, and the Latin word, “pollex”, meaning thumb. Originally described in 1986 by Sereno, a most likely synapomorphic feature of a conical thumb spine defines the clade.
Yakovlevian torque is the tendency of the right side of the human brain to be warped slightly forward relative to the left and the left side of the human brain to be warped slightly backward relative to the right. This is responsible for certain asymmetries, such as how the lateral sulcus of the human brain is often longer and less curved on the left side of the brain relative to the right. Stated in another way, Yakovlevian torque can be defined by the existence of right-frontal and left-occipital petalias, which are protrusions of the surface of one hemisphere relative to the other. It is named for Paul Ivan Yakovlev (1894–1983), a Russian-American neuroanatomist from Harvard Medical School.
Johanna Gabrielle Ottilie "Tilly" Edinger was a German-American paleontologist and the founder of paleoneurology.
This glossary explains technical terms commonly employed in the description of dinosaur body fossils. Besides dinosaur-specific terms, it covers terms with wider usage, when these are of central importance in the study of dinosaurs or when their discussion in the context of dinosaurs is beneficial. The glossary does not cover ichnological and bone histological terms, nor does it cover measurements.
Cerebavis is an extinct genus of bird that lived during the middle Cenomanian of the Late Cretaceous period, and is known from a single partial skull found in the Melovatskaya Formation of Volgograd Region in Russia. The skull was initially described as the fossilised brain of an enantiornithean by Russian palaeornithologist Evgeny Kurochkin and colleagues in 2006. Kurochkin and colleagues described Cerebavis as having a notable mixture of ancestral traits, such as a well-developed olfactory system, with derived traits of modern birds like a large cerebrum. At the same time, they identified various unusual and unique features not seen in the brains of reptiles or birds. These include well-developed auditory tubercles on the midbrain, as well as a prominent parietal organ compared to living birds or Archaeopteryx between them.
Pilmatueia is a diplodocoid sauropod belonging to the family Dicraeosauridae that lived in Argentina during the Early Cretaceous. Its type and only species is Pilmatueia faundezi. Pilmatueia was probably closely related to other South American dicraeosaurids such as Amargasaurus. Pilmatueia had relatively pneumatic vertebrae compared to other dicraeosaurids, which were otherwise characterized by a reduction in pneumaticity relative to other sauropods. Pilmatueia dates to the Valanginian, an age of the Cretaceous period for which dinosaur faunas are poorly known.