|
Materpiscis Attenboroughi
''Materpiscis'' (Latin for ''mother fish'') is a genus of ptyctodontid placoderm from the Late Devonian located at the Gogo Formation of Western Australia. Known from only one specimen, it is unique in having an unborn embryo present inside the mother, with remarkable preservation of a mineralised placental feeding structure (umbilical cord). This makes ''Materpiscis'' the oldest known vertebrate to show viviparity, or giving birth to live young. Discovery and naming The holotype was found in the Kimberley area of northern Western Australia by Lindsay Hatcher during the 2005 expedition to the Gogo led by John Long of Museum Victoria. Fossils from the Gogo Formation are preserved in limestone nodules, so dilute acetic acid is used to dissolve the surrounding limestone and reveal the fossil, often preserved in three dimensions with minimal distortion. The species was named ''Materpiscis attenboroughi'' in honour of David Attenborough who first drew attention to the significance o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, where rocks from this period were first studied. The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. The arthropod groups of myriapods, arachnids and hexapods also became well-established early in this period, after starting their expansion to land at least from the Ordovician period. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The placoderms began dominating al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood and DNA remnants. The totality of fossils is known as the ''fossil record''. Paleontology is the study of fossils: their age, method of formation, and evolutionary significance. Specimens are usually considered to be fossils if they are over 10,000 years old. The oldest fossils are around 3.48 billion years old to 4.1 billion years old. Early edition, published online before print. The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils. The development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Incisoscutum
''Incisoscutum'' is an extinct genus of arthrodire placoderm from the Early Frasnian Gogo Reef, from Late Devonian Australia. The genus contains two species ''I. ritchiei'', named after Alex Ritchie, a palaeoichthyologist and senior fellow of the Australian Museum, and ''I. sarahae'', named after Sarah Long, daughter of its discoverer and describer, John A. Long. The genus is important in the study of early vertebrates as well-preserved fossilized embryos have been found in female specimens and ossified pelvic claspers found in males. This shows that viviparity and internal fertilization was common amongst these primitive jawed vertebrates, which are outside the crown group Gnathostomata. In a study of fossil remains, comparison of the ontogeny of fourteen dermal plates from '' Compagopiscis croucheri'' and the more derived species ''Incisoscutum ritchiei'' suggested that lengthwise growth occurs earlier in the ontogeny than growth in width, and that dissociated allometric het ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viviparous
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the mother. The term 'viviparity' and its adjective form 'viviparous' derive from the Latin ''vivus'' meaning "living" and ''pario'' meaning "give birth to". Reproductive mode Five modes of reproduction have been differentiated in animals based on relations between zygote and parents. The five include two nonviviparous modes: ovuliparity, with external fertilisation, and oviparity, with internal fertilisation. In the latter, the female lays zygotes as eggs with a large yolk; this occurs in all birds, most reptiles, and some fishes. These modes are distinguished from viviparity, which covers all the modes that result in live birth: *Histotrophic viviparity: the zygotes develop in the female's oviducts, but find their nutrients by oophagy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Austroptyctodus
''Austroptyctodus gardineri'' is a small ptyctodontid placoderm fish from the Upper Devonian Gogo Formation of Western Australia. First described by Miles & Young (1977) as a new species of the German genus '' Ctenurella''. Long (1997) redescribed the German material and found major differences in the skull roof pattern so assigned it to a new genus, ''Austroptyctodus''. This genus lacks spinal plates and has ''Ptyctodus''-like toothplates. The most significant discovery about ''Austroptyctodus'' is that one specimen depicts a female pregnant with 3 unborn embryos inside her, showing that like ''Materpiscis'', also from Gogo, this genus was a live bearer that reproduced through internal fertilization Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. For inter ....Long, J.A., Trinajstic, K., ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taxonomists
In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon) and these groups are given a taxonomic rank; groups of a given rank can be aggregated to form a more inclusive group of higher rank, thus creating a taxonomic hierarchy. The principal ranks in modern use are domain, kingdom, phylum (''division'' is sometimes used in botany in place of ''phylum''), class, order, family, genus, and species. The Swedish botanist Carl Linnaeus is regarded as the founder of the current system of taxonomy, as he developed a ranked system known as Linnaean taxonomy for categorizing organisms and binomial nomenclature for naming organisms. With advances in the theory, data and analytical technology of biological systematics, the Linnaean system has transformed into a system of modern biological classification intended to reflect the evolut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arizona State University
Arizona State University (Arizona State or ASU) is a public research university in the Phoenix metropolitan area. Founded in 1885 by the 13th Arizona Territorial Legislature, ASU is one of the largest public universities by enrollment in the U.S. One of three universities governed by the Arizona Board of Regents, ASU is a member of the Universities Research Association and classified among "R1: Doctoral Universities – Very High Research Activity". ASU has nearly 150,000 students attending classes, with more than 38,000 students attending online, and 90,000 undergraduates and nearly 20,000 postgraduates across its five campuses and four regional learning centers throughout Arizona. ASU offers 350 degree options from its 17 colleges and more than 170 cross-discipline centers and institutes for undergraduates students, as well as more than 400 graduate degree and certificate programs. The Arizona State Sun Devils compete in 26 varsity-level sports in the NCAA Division I Pac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Materpiscis02
''Materpiscis'' (Latin for ''mother fish'') is a genus of ptyctodontid placoderm from the Late Devonian located at the Gogo Formation of Western Australia. Known from only one specimen, it is unique in having an unborn embryo present inside the mother, with remarkable preservation of a mineralised placental feeding structure (umbilical cord). This makes ''Materpiscis'' the oldest known vertebrate to show viviparity, or giving birth to live young. Discovery and naming The holotype was found in the Kimberley area of northern Western Australia by Lindsay Hatcher during the 2005 expedition to the Gogo led by John Long of Museum Victoria. Fossils from the Gogo Formation are preserved in limestone nodules, so dilute acetic acid is used to dissolve the surrounding limestone and reveal the fossil, often preserved in three dimensions with minimal distortion. The species was named ''Materpiscis attenboroughi'' in honour of David Attenborough who first drew attention to the significa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internal Fertilisation
Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. For internal fertilization to happen there needs to be a method for the male to introduce the sperm into the female's reproductive tract. Most taxa that reproduce by internal fertilization are gonochoric. In mammals, reptiles, and certain other groups of animals, this is done by copulation, an intromittent organ being introduced into the vagina or cloaca. In most birds, the cloacal kiss is used, the two animals pressing their cloacas together while transferring sperm. Salamanders, spiders, some insects and some molluscs undertake internal fertilization by transferring a spermatophore, a bundle of sperm, from the male to the female. Following fertilization, the embryos are laid as eggs in oviparous organisms, or continue to develop inside th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Female
Female (Venus symbol, symbol: ♀) is the sex of an organism that produces the large non-motile ovum, ova (egg cells), the type of gamete (sex cell) that fuses with the Sperm, male gamete during sexual reproduction. A female has larger gametes than a male. Females and males are results of the anisogamous reproduction system, wherein gametes are of different sizes, unlike isogamy where they are the same size. The exact mechanism of female gamete evolution remains unknown. In species that have males and females, Sex-determination system, sex-determination may be based on either sex chromosomes, or environmental conditions. Most female mammals, including female humans, have two X chromosomes. Female characteristics vary between different species with some species having pronounced Secondary sex characteristic, secondary female sex characteristics, such as the presence of pronounced mammary glands in mammals. In humans, the word ''female'' can also be used to refer to gender i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Male
Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to at least one ovum from a female, but some organisms can reproduce both sexually and asexually. Most male mammals, including male humans, have a Y chromosome, which codes for the production of larger amounts of testosterone to develop male reproductive organs. Not all species share a common sex-determination system. In most animals, including humans, sex is determined genetically; however, species such as ''Cymothoa exigua'' change sex depending on the number of females present in the vicinity. In humans, the word ''male'' can also be used to refer to gender in the social sense of gender role or gender identity. Overview The existence of separate sexes has evolved independently at different times and in different lineages, an example ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual Dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most animals and some plants. Differences may include secondary sex characteristics, size, weight, colour, markings, or behavioural or cognitive traits. These differences may be subtle or exaggerated and may be subjected to sexual selection and natural selection. The opposite of dimorphism is ''monomorphism'', which is when both biological sexes are phenotypically indistinguishable from each other. Overview Ornamentation and coloration Common and easily identified types of dimorphism consist of ornamentation and coloration, though not always apparent. A difference in coloration of sexes within a given species is called sexual dichromatism, which is commonly seen in many species of birds and reptiles. Sexual selection leads to the exaggerated dim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
