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Ankylosphenodon
''Ankylosphenodon'' is an extinct genus of sphenodontian known from multiple specimens recovered from the Early Cretaceous deposits of the Tlayúa Formation, near Tepexi de Rodríguez, Tepexi de Rodriguez, Mexico. It is likely part of a sphenodontid lineage that also includes ''Eilenodon'' and ''Toxolophosaurus'', though has similarities to the sapheosaur clade. Its skeleton is Pachyostosis, pachyostotic (thickened) skeleton, believed to be an adaptation for a semi-aquatic lifestyle. Its teeth appear to have grown continuously, like in Rodent, rodents. Taxonomy Discovery and formal description ''Ankylosphenodon'' is known from multiple specimens recovered from the Tlayúa Formation, a vertebrate-rich Lagerstätte near Tepexi de Rodríguez, Tepexi de Rodriguez, in Central Mexico. The holotype (IGM 7441) is a partial skeleton, consisting of a skull, the left forelimb, and the front half of the presacral vertebral column. Another specimen, IGM 7443, preserves most of the right ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sphenodontian
Rhynchocephalia (; ) is an order (biology), order of lizard-like reptiles that includes only one living species, the tuatara (''Sphenodon punctatus'') of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a speciose group with high morphological and ecological diversity. The oldest record of the group is dated to the Middle Triassic around 238 to 240 million years ago, and they had achieved global distribution by the Early Jurassic. Most rhynchocephalians belong to the group Sphenodontia ('wedge-teeth'). Their closest living relatives are lizards and snakes in the order Squamata, with the two orders being grouped together in the superorder Lepidosauria. Rhynchocephalians are distinguished from squamates by a number of traits, including the retention of rib-like gastralia bones in the belly, as well as most rhynchocephalians having acrodont teeth that are fused to the crests of the jaws (the latter also found among a small number of mod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sapheosaur
Sapheosaurs are an Extinction, extinct group of rhynchocephalian reptiles from the Late Jurassic period. "Sapheosaurs" is an informal name for a group of rhynchocephalians closely related to the genus ''Sapheosaurus''. It was first recognized as a group containing multiple genera by Hoffstetter in 1955. The group has sometimes been given a formal taxonomic name as the Family (biology), family Sapheosauridae, although in some analyses this group belongs to the family Sphenodontidae (which also contains the tuatara, the only living rhynchocephalian) and thus cannot be assigned its own family. They were fairly advanced rhynchocephalians which may have had semiaquatic habits. Classification The most well-known members of the group are ''Sapheosaurus'' and ''Kallimodon'', and most Phylogenetics, phylogenetic analyses on rhynchocephalians only study these two Genus, genera as representatives of sapheosaurs. Although a few early phylogenies in the 1990s did not find that these two form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sapheosaurs
Sapheosaurs are an extinct group of rhynchocephalian reptiles from the Late Jurassic period. "Sapheosaurs" is an informal name for a group of rhynchocephalians closely related to the genus '' Sapheosaurus''. It was first recognized as a group containing multiple genera by Hoffstetter in 1955. The group has sometimes been given a formal taxonomic name as the family Sapheosauridae, although in some analyses this group belongs to the family Sphenodontidae (which also contains the tuatara, the only living rhynchocephalian) and thus cannot be assigned its own family. They were fairly advanced rhynchocephalians which may have had semiaquatic habits. Classification The most well-known members of the group are ''Sapheosaurus'' and '' Kallimodon'', and most phylogenetic analyses on rhynchocephalians only study these two genera as representatives of sapheosaurs. Although a few early phylogenies in the 1990s did not find that these two formed a natural clade, the relation between these tw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sphenodontidae
Sphenodontidae is a family within the reptile group Rhynchocephalia, comprising taxa most closely related to the living tuatara (''Sphenodon punctatus''). Historically the taxa included within Sphenodontidae have varied greatly between analyses, and the group has lacked a formal definition. '' Cynosphenodon'' from the Jurassic of Mexico has consistently been recovered as a close relative of the tuatara in most analyses, with the clade containing the two and other very close relatives of the tuatara often called Sphenodontinae. The herbivorous Eilenodontinae, otherwise considered part of Opisthodontia, is considered to be part of this family in many recent studies as the sister group to Sphenodontinae. The earliest sphenodontines are known from the Early Jurassic of North America, with other remains known from the Late Jurassic of Europe, the Late Cretaceous and possibly Paleocene of South America and the Miocene-recent of New Zealand. Sphenodontines are characterised by a comple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tlayúa Formation
The Tlayúa Formation is an Cretaceous Konservat-Lagerstätte near Tepexi de Rodríguez, Puebla, Central Mexico. It consists of three members (Lower, Middle and Upper), spanning the lower Albian of the Early Cretaceous to the lower Cenomanian of the Late Cretaceous. It consists of a series of limestone quarries that preserve lagoonal palaeoenvironments, such as a shelf lagoon, a shallow lagoon surrounded by a penneplain, and a tidal flat. It is notable for preserving high quantities of vertebrate and invertebrate fossils, and is thus considered a Lagerstätte. Description The Tlayúa Formation was first described by Jerjes Pantoja-Alor in 1992. It is located in the Tlayúa ravine, which itself lies in the southern portion of Puebla, Central Mexico, near Tepexi de Rodríguez, and consists of a series of limestone quarries that has seen commercial use for decades. Stratigraphy The Tlayúa Formation consists of two stratigraphic units (Tlayúa and Barranca Abuelo) and three ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Cretaceous
The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 Megaannum#SI prefix multipliers, Ma to 100.5 Ma. Geology Proposals for the exact age of the Barremian–Aptian boundary ranged from 126 to 117 Ma until recently (as of 2019), but based on drillholes in Svalbard the defining Anoxic event#Cretaceous, early Aptian Oceanic Anoxic Event 1a (OAE1a) was dated to 123.1±0.3 Ma, limiting the possible range for the boundary to c. 122–121 Ma. There is a possible link between this anoxic event and a series of Early Cretaceous large igneous provinces (LIP). The Ontong Java Plateau, Ontong Java-Manihiki Plateau, Manihiki-Hikurangi Plateau, Hikurangi large igneous province, emplaced in the South Pacific at c. 120 Ma, is by far the largest LIP in Earth's history. The Onto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratigraphic Unit
A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features ( facies) that characterize it. Units must be ''mappable'' and ''distinct'' from one another, but the contact need not be particularly distinct. For instance, a unit may be defined by terms such as "when the sandstone component exceeds 75%". Lithostratigraphic units Sequences of sedimentary and volcanic rocks are subdivided on the basis of their shared or associated lithology. Formally identified lithostratigraphic units are structured in a hierarchy of lithostratigraphic rank, higher rank units generally comprising two or more units of lower rank. Going from smaller to larger in rank, the main lithostratigraphic ranks are bed, member, formation, group and supergroup. Formal names of lithostratigraphic units are assigned by geological surveys. Units of form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
National Autonomous University Of Mexico
The National Autonomous University of Mexico (, UNAM) is a public university, public research university in Mexico. It has several campuses in Mexico City, and many others in various locations across Mexico, as well as a presence in nine countries. It also has 34 research institutes, 26 museums, and 18 historic sites. A portion of (University City), UNAM's main campus in Mexico City, is a UNESCO World Heritage site that was designed and decorated by some of Mexico's best-known architects and painters. The campus hosted the main events of the 1968 Summer Olympics, and was the birthplace of the Mexican Movement of 1968, student movement of 1968. All Mexican Nobel laureates have been alumni of UNAM. In 2009, the university was awarded the Princess of Asturias Awards, Prince of Asturias Award for Communication and Humanities. More than 25% of the total scientific papers published by Mexican academics come from researchers at UNAM. UNAM was founded in its modern form, on 22 Septemb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tuatara
The tuatara (''Sphenodon punctatus'') is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephalia. The name is derived from the Māori language and means "peaks on the back". The single extant species of tuatara is the only surviving member of its order, which was highly diverse during the Mesozoic era. Rhynchocephalians first appeared in the fossil record during the Triassic, around 240 million years ago, and reached worldwide distribution and peak diversity during the Jurassic, when they represented the world's dominant group of small reptiles. Rhynchocephalians declined during the Cretaceous, with their youngest records outside New Zealand dating to the Paleocene. Their closest living relatives are squamates (lizards and snakes). Tuatara are of interest for studying the evolution of reptiles. Tuatara are greenish brown an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convergent Evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last common ancestor of those groups. The cladistic term for the same phenomenon is Cladogram#Homoplasies, homoplasy. The recurrent evolution of flight is a classic example, as flying pterygota, insects, birds, pterosaurs, and bats have independently evolved the useful capacity of flight. Functionally similar features that have arisen through convergent evolution are ''analogous'', whereas ''homology (biology), homologous'' structures or traits have a common origin but can have dissimilar functions. Bird, bat, and pterosaur wings are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions. The opposite of convergence is divergent evolution, where related species evolve different trai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lagerstätte
A Fossil-Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that preserves an exceptionally high amount of palaeontological information. ''Konzentrat-Lagerstätten'' preserve a high concentration of fossils, while ''Konservat-Lagerstätten'' offer exceptional fossil preservation, sometimes including preserved soft tissues. ''Konservat-Lagerstätten'' may have resulted from carcass burial in an anoxic environment with minimal bacteria, thus delaying the decomposition of both gross and fine biological features until long after a durable impression was created in the surrounding matrix. ''Fossil-Lagerstätten'' spans geological time from the Neoproterozoic era to the present. Worldwide, some of the best examples of near-perfect fossilization are the Cambrian Maotianshan shales and Burgess Shale, the Ordovician Soom Shale, the Silurian Waukesha Biota, the Devonian Hunsrück Slates and Gogo Formation, the Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spinal Column
The spinal column, also known as the vertebral column, spine or backbone, is the core part of the axial skeleton in vertebrates. The vertebral column is the defining and eponymous characteristic of the vertebrate. The spinal column is a segmented column of vertebrae that surrounds and protects the spinal cord. The vertebrae are separated by intervertebral discs in a series of cartilaginous joints. The dorsal portion of the spinal column houses the spinal canal, an elongated cavity formed by the alignment of the vertebral neural arches that encloses and protects the spinal cord, with spinal nerves exiting via the intervertebral foramina to innervate each body segment. There are around 50,000 species of animals that have a vertebral column. The human spine is one of the most-studied examples, as the general structure of human vertebrae is fairly typical of that found in other mammals, reptiles, and birds. The shape of the vertebral body does, however, vary somewhat b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
