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83-552: Thrinaxodon is an extinct genus of cynodonts , including the species T. liorhinus which lived in what are now South Africa and Antarctica during the Early Triassic . Thrinaxodon lived just after the Permian–Triassic mass extinction event , its survival during the extinction may have been due to its burrowing habits. Similar to other therapsids , Thrinaxodon adopted a semi-sprawling posture, an intermediary form between

166-557: A species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in the nomenclature codes , which allow each species a single unique name that, for animals (including protists ), plants (also including algae and fungi ) and prokaryotes ( bacteria and archaea ), is Latin and binomial in form; this contrasts with common or vernacular names , which are non-standardized, can be non-unique, and typically also vary by country and language of usage. Except for viruses ,

249-494: A change so dramatic that it is most likely that the fossil record for this particular transition is incomplete. Thrinaxodon contains fewer bones in the skull than that of its pelycosaurian ancestors. Data on the dentition of Thrinaxodon liorhinus was compiled by use of a micro CT scanner on a large sample of Thrinaxodon skulls, ranging between 30 and 96 mm (1.2 and 3.8 in) in length. These dentition patterns are similar to that of Morganucodon , allowing one to make

332-643: A later homonym of a validly published name is a nomen illegitimum or nom. illeg. ; for a full list refer to the International Code of Nomenclature for algae, fungi, and plants and the work cited above by Hawksworth, 2010. In place of the "valid taxon" in zoology, the nearest equivalent in botany is " correct name " or "current name" which can, again, differ or change with alternative taxonomic treatments or new information that results in previously accepted genera being combined or split. Prokaryote and virus codes of nomenclature also exist which serve as

415-621: A long time and redescribed as new by a range of subsequent workers, or if a range of genera previously considered separate taxa have subsequently been consolidated into one. For example, the World Register of Marine Species presently lists 8 genus-level synonyms for the sperm whale genus Physeter Linnaeus, 1758, and 13 for the bivalve genus Pecten O.F. Müller, 1776. Within the same kingdom, one generic name can apply to one genus only. However, many names have been assigned (usually unintentionally) to two or more different genera. For example,

498-504: A multitude of branched canaliculi. Ontogenetically early bones - mostly consisting of fibro-lamellar tissue - possessed a large amount of vascular canals. These canals are oriented longitudinally within primary osteons that contain radial anastomoses. Regions consisting mostly of parallel-fibred bone tissue contain few simple vascular canals, in comparison to the nearby fibro-lamellar tissues. Parallel-fibred peripheral bone tissue are indicative that bone growth began to slow, and they bring about

581-631: A new species of Thrinaxodontidae, or if they had found another area which T. liorhinus called home. The first experiment was to evaluate the average number of pre-sacral vertebrae in the Antarctic vs African Thrinaxodon . The data actually showed a slight difference between the two, in that the African T. liorhinus contained 26 presacrals, while the Antarctic Thrinaxodon had 27 pre-sacrals. In comparison to other cynodonts, 27 pre-sacrals appeared to be

664-458: A posterior palatine foramen. The large palatal roof component of the vomer in Thrinaxodon is just dorsal to the choana, or interior nasal passages. The pterygoid bones extend in the upper jaw and enclose small interpterygoid vacuities that are present on each side of the cultriform processes of the parasphenoids. The parasphenoid and basisphenoid are fused, except for the most anterior/dorsal end of

747-409: A reference for designating currently accepted genus names as opposed to others which may be either reduced to synonymy, or, in the case of prokaryotes, relegated to a status of "names without standing in prokaryotic nomenclature". An available (zoological) or validly published (botanical) name that has been historically applied to a genus but is not regarded as the accepted (current/valid) name for

830-401: A replacement canine does exist, more often than not it is not erupted and the original functional canine remains. The bone tissue of Thrinaxodon consists of fibro-lamellar bone, to a varying degree across all the separate limbs, most of which develops into parallel-fibred bone tissue towards the periphery. Each of the bones contains a large abundance of globular osteocyte lacunae which radiate

913-406: A small note that in general, adult Thrinaxodon contained anywhere between 44 and 46 total teeth. Upper incisors in T. liorhinus assume a backwards directed cusp, being curved and pointed at their most distal point, and becoming broader and rounder as they reach their proximal insertion point into the premaxilla. The fourth upper incisor is roughly homologous with a small canine tooth in form, but

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996-427: A taxon; however, the names published in suppressed works are made unavailable via the relevant Opinion dealing with the work in question. In botany, similar concepts exist but with different labels. The botanical equivalent of zoology's "available name" is a validly published name . An invalidly published name is a nomen invalidum or nom. inval. ; a rejected name is a nomen rejiciendum or nom. rej. ;

1079-455: A total of c. 520,000 published names (including synonyms) as at end 2019, increasing at some 2,500 published generic names per year. "Official" registers of taxon names at all ranks, including genera, exist for a few groups only such as viruses and prokaryotes, while for others there are compendia with no "official" standing such as Index Fungorum for fungi, Index Nominum Algarum and AlgaeBase for algae, Index Nominum Genericorum and

1162-399: A unified sagittal crest had developed rather than having a single suture span the entire length of the skull. The bone histology of Thrinaxodon indicates that it most likely had very rapid bone growth during juvenile development, and much slower development throughout adulthood, giving rise to the idea that Thrinaxodon reached peak size very early in its life. The posture of Thrinaxodon

1245-490: Is a large difference in comparison to the distal femoral condyle of pelycosaurs, which permits the femur to be parallel with the ground, forcing them to assume a sprawling-like posture. More interesting is that there is an adaptation that has only been observed within Thrinaxodontidae, which allows them to assume upright posture, similar to that of early Mammalia, within their burrows. These changes in posture are supported by

1328-562: Is a pelycosaur side-branch, or clade, that did not leave any descendants. The pelycosaurs appear to have been a group of synapsids that have direct ancestral links with the mammals , having differentiated teeth and a developing hard palate. The pelycosaurs appeared during the Late Carboniferous and reached their apex in the early part of the Permian , remaining the dominant land animals for some 40 million years. A few continued into

1411-404: Is an interesting subject, because it represents a transition between the sprawling behavior of the more lizard-like pelycosaurs and the more upright behavior found in modern, and many extinct, Mammalia. In cynodonts such as Thrinaxodon , the distal femoral condyle articulates with the acetabulum in a way that permits the hindlimb to present itself at a 45-degree angle to the rest of the system. This

1494-596: Is discouraged by both the International Code of Zoological Nomenclature and the International Code of Nomenclature for algae, fungi, and plants , there are some five thousand such names in use in more than one kingdom. For instance, A list of generic homonyms (with their authorities), including both available (validly published) and selected unavailable names, has been compiled by the Interim Register of Marine and Nonmarine Genera (IRMNG). The type genus forms

1577-546: Is not used formally, since it does not constitute a group of all organisms descended from some common ancestor (a clade ), because the group specifically excludes the therapsids which are descended from pelycosaurs. Instead, it represents a paraphyletic "grade" of basal synapsids leading up to the clade Therapsida. In 1940, the group was reviewed in detail, and every species known at the time described, with many illustrated, in an important monograph by Alfred Sherwood Romer and Llewellyn Price . In traditional classification,

1660-416: Is positioned too far anteriorly to be a functional canine - thus ruling it out as an instance of convergent evolution. Lower incisors possess a very broad base, which is progressively reduced, heading distally towards the tip of the tooth. The lingual face of the lower incisors is most often concave while the labial face is often convex, and these lower incisors are oriented anteriorly, except in some cases for

1743-460: Is somewhat arbitrary. Although all species within a genus are supposed to be "similar", there are no objective criteria for grouping species into genera. There is much debate among zoologists about whether enormous, species-rich genera should be maintained, as it is extremely difficult to come up with identification keys or even character sets that distinguish all species. Hence, many taxonomists argue in favor of breaking down large genera. For instance,

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1826-474: Is the type species , and the generic name is permanently associated with the type specimen of its type species. Should the specimen turn out to be assignable to another genus, the generic name linked to it becomes a junior synonym and the remaining taxa in the former genus need to be reassessed. In zoological usage, taxonomic names, including those of genera, are classified as "available" or "unavailable". Available names are those published in accordance with

1909-423: Is unlikely that Thrinaxodon would have had whiskers. On the skull roof of Thrinaxodon , the fronto-nasal suture represents an arrow shape instead of the general transverse process seen in more primitive skull morphologies. The prefrontals, which are slightly anterior and ventral to the frontals exhibit a very small size and come in contact with the post-orbitals, frontals, nasals and lacrimals. More posteriorly on

1992-796: The Capitanian , but they experienced a sharp decline in diversity in the late Kungurian . They were succeeded by the therapsids . Some species were quite large, growing to a length of 3 metres (10 ft) or more, although most species were much smaller. Well-known pelycosaurs include the genera Dimetrodon , Sphenacodon , Edaphosaurus , and Ophiacodon . Pelycosaur fossils have been found mainly in Europe and North America , although some small, late-surviving forms are known from Russia and South Africa . Unlike lepidosaurian reptiles, pelycosaurs might have lacked reptilian epidermal scales . Fossil evidence from some varanopids shows that parts of

2075-621: The International Code of Zoological Nomenclature ; the earliest such name for any taxon (for example, a genus) should then be selected as the " valid " (i.e., current or accepted) name for the taxon in question. Consequently, there will be more available names than valid names at any point in time; which names are currently in use depending on the judgement of taxonomists in either combining taxa described under multiple names, or splitting taxa which may bring available names previously treated as synonyms back into use. "Unavailable" names in zoology comprise names that either were not published according to

2158-799: The International Plant Names Index for plants in general, and ferns through angiosperms, respectively, and Nomenclator Zoologicus and the Index to Organism Names for zoological names. Totals for both "all names" and estimates for "accepted names" as held in the Interim Register of Marine and Nonmarine Genera (IRMNG) are broken down further in the publication by Rees et al., 2020 cited above. The accepted names estimates are as follows, broken down by kingdom: The cited ranges of uncertainty arise because IRMNG lists "uncertain" names (not researched therein) in addition to known "accepted" names;

2241-407: The Thrinaxodon skull increased in size isometrically, except for four regions, one of which being the optic region. Much of the data assumes that the length of the sagittal crest increased at a greater rate in relation to the rest of the skull. The posterior sagittal crest to appear in an earlier ontogenetic stage than the more anterior crest had, and in conjunction with the dorsal deposition of bone,

2324-442: The opossums , and other marsupials , and as regular dermal armour with underlying bone in the armadillo . At least two pelycosaur clades independently evolved a tall sail , consisting of elongated vertebral spines: the edaphosaurids and the sphenacodontids . In life, this may have been covered by skin, and likely functioned as a thermoregulatory device or as a mating display . In phylogenetic nomenclature, "Pelycosauria"

2407-404: The platypus belongs to the genus Ornithorhynchus although George Shaw named it Platypus in 1799 (these two names are thus synonyms ) . However, the name Platypus had already been given to a group of ambrosia beetles by Johann Friedrich Wilhelm Herbst in 1793. A name that means two different things is a homonym . Since beetles and platypuses are both members of the kingdom Animalia,

2490-580: The 21st century, and is only used informally, if at all, in the modern scientific literature. The terms stem mammals , protomammals , and basal or primitive synapsids are instead used where needed. The modern word was created from Greek [[[wikt:πέλυξ|pélyx]]] Error: {{Lang}}: Non-latn text/Latn script subtag mismatch ( help ) meaning 'basin' and [[[wikt:σαῦρος|saûros]]] Error: {{Lang}}: Non-latn text/Latn script subtag mismatch ( help ) meaning 'lizard'. The term pelycosaur has been fairly well abandoned by paleontologists because it no longer matches

2573-469: The French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or the scientific epithet) of a genus is also called the generic name ; in modern style guides and science, it is always capitalised. It plays a fundamental role in binomial nomenclature , the system of naming organisms , where it is combined with the scientific name of

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2656-587: The adaptive advantage of burrowing during the extinction. The burrow of Thrinaxodon consists of two laterally sloping halves, a pattern that has only been observed in burrowing non-mammalian Cynodontia. The changes in vertebral/rib anatomy that arose in Thrinaxodon permit the animals to a greater range of flexibility, and the ability to place their snout underneath their hindlimbs, an adaptive response to small living quarters, in order to preserve warmth and/or for aestivation purposes. A Thrinaxodon burrow contained an injured temnospondyl, Broomistega . The burrow

2739-559: The anterior cusp will be the first to appear and will be the most pronounced cusp. In the upper postcanines, there should be no occurrence of any teeth possessing more than three cusps, and there is no occurrence of any labial cusps on the upper postcanines. The majority of upper postcanines in the juvenile Thrinaxodon are bicuspid, while only one of these upper teeth are tricuspid. The upper postcanines of an intermediate (between juvenile and adult) Thrinaxodon are all tricuspid with no labial or cingular cusps. The adult upper postcanines retain

2822-413: The appropriate space for a diaphragm, however, without proper soft tissue records, the presence of a diaphragm is purely speculative. Thrinaxodon has been identified as a burrowing cynodont by numerous discoveries in preserved burrow hollows. There is evidence that the burrows are in fact built by the Thrinaxodon to live in them, and they do not simply inhabit leftover burrows by other creatures. Due to

2905-442: The assumption that these dentition patterns arose within Thrinaxodontidae and extended into the records of early Mammalia. Adult T. liorhinus assumes the dental pattern of the four incisors, one canine and six postcanines on each side of the upper jaw. This pattern is reflected in the lower jaw by a dental formula of three incisors, one canine and seven or eight postcanines on each side of the lower jaw. With this formula, one can make

2988-403: The assumption that this change in growth was due to the age of the specimen in question. Combine this with the greater organization of osteocyte lacunae in the periphery of adult T. liorhinus , and we approach the assumption that this creature grew very quickly in order to reach adulthood at an accelerated rate. Before Thrinaxodon , ontogenical patterns such as this had not been seen, establishing

3071-442: The base for higher taxonomic ranks, such as the family name Canidae ("Canids") based on Canis . However, this does not typically ascend more than one or two levels: the order to which dogs and wolves belong is Carnivora ("Carnivores"). The numbers of either accepted, or all published genus names is not known precisely; Rees et al., 2020 estimate that approximately 310,000 accepted names (valid taxa) may exist, out of

3154-411: The canine) is most often smaller than the other postcanines and is most often bicuspid. Including the first postcanine, if any of the other postcanines are bicuspid, then it is safe to assume that the posterior accessary cusp is present and that that tooth will not have any cingular or labial cusps. If, however, the tooth is tricuspid, then there is a chance of cingular cusps developing, if this occurs then

3237-420: The distance between the canines of the Thrinaxodon in question, and no such relation was found. Therefore, we may assume that the temnospondyl found refuge in the burrow after a traumatic experience and the T. liorhinus allowed it to stay in its burrow until they both ultimately met their respective deaths. Interspecific shelter sharing is a rare anomaly within the fossil record; this T. liorhinus shows one of

3320-413: The evolution of a segmented vertebral column into thoracic, lumbar and sacral vertebrae, Thrinaxodon was able to achieve flexibilities that permitted it to comfortably rest within smaller burrows, which may have led to habits such as aestivation or torpor. This evolution of a segmented rib cage suggests that this may have been the first instance of a diaphragm in the synapsid fossil record; however, without

3403-476: The features that distinguish a clade. Pelycosauria is a paraphyletic taxon because it excludes the therapsids . For that reason, the term is sometimes avoided by proponents of a strict cladistic approach. Eupelycosauria is used to designate the clade that includes most pelycosaurs, along with the Therapsida and Mammalia. In contrast to "pelycosaurs", Eupelycosauria is a proper monophyletic group. Caseasauria

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3486-502: The first occurrences of this type of behavior in the fossil record, but it currently is unknown if the temnospondyl inhabited the burrow before or after the death of the nesting Thrinaxodon . [REDACTED] Genus (biology) The composition of a genus is determined by taxonomists . The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including

3569-446: The form "author, year" in zoology, and "standard abbreviated author name" in botany. Thus in the examples above, the genus Canis would be cited in full as " Canis Linnaeus, 1758" (zoological usage), while Hibiscus , also first established by Linnaeus but in 1753, is simply " Hibiscus L." (botanical usage). Each genus should have a designated type , although in practice there is a backlog of older names without one. In zoology, this

3652-412: The fused bones, in which there is a slight separation in the trabecular attachment of the basisphenoid. The otic region is defined by the regions surrounding the temporal fenestrae. Most notable is evidence of a deep recess that is just anterior to the fenestra ovalis, containing evidence of smooth muscle interactions with the skull. Such smooth muscle interactions have been interpreted to be indicative of

3735-727: The generic name (or its abbreviated form) still forms the leading portion of the scientific name, for example, Canis lupus lupus for the Eurasian wolf subspecies, or as a botanical example, Hibiscus arnottianus ssp. immaculatus . Also, as visible in the above examples, the Latinised portions of the scientific names of genera and their included species (and infraspecies, where applicable) are, by convention, written in italics . The scientific names of virus species are descriptive, not binomial in form, and may or may not incorporate an indication of their containing genus; for example,

3818-412: The idea of a connected land mass, and that during the early Triassic, Africa and Antarctica must have been linked in some way, shape or form. Thrinaxodon belongs to the clade Epicynodontia , a subdivision of the greater clade Cynodontia. Cynodontia eventually led to the evolution of Morganucodon and all other mammalia. Cynodontia belongs to the clade Therapsida , which was the first major clade along

3901-432: The idea that a newly defined genus should fulfill these three criteria to be descriptively useful: Moreover, genera should be composed of phylogenetic units of the same kind as other (analogous) genera. The term "genus" comes from Latin genus , a noun form cognate with gignere ('to bear; to give birth to'). The Swedish taxonomist Carl Linnaeus popularized its use in his 1753 Species Plantarum , but

3984-438: The idea that reaching peak size rapidly was an adaptively advantageous trait that had arisen with Thrinaxodon . Within the femur of Thrinaxodon , there is no major region of the bone that is made of parallel-fibred tissues; however, there is a small ring of parallel-fibred bone within the mid-cortex. The remainder of the femur is made of fibro-lamellar tissue; however, the globular osteocyte lacunae become much more organized and

4067-446: The intermediate physiologies and possess only tricuspid teeth; however, it is possible for cingular cusps to develop in these adult teeth. The ultimate (posterior-most) upper canine is often the smallest of all canines in the entire jaw system. Little data is known of the juvenile and intermediate forms of the lower postcanines in Thrinaxodon , but the adult lower postcanines all possess multiple (any value more than three) cusps as well as

4150-480: The jaw, posterior to the existing canine, neither of the replacement or functional canine teeth possess any serrated margins only the small facets. It is important to note that the lower canine is directed almost vertically (dorsoventrally) while the upper canine is directed slightly anteriorly. The upper and lower postcanines in T. liorhinus share some common features but also vary quite a fair amount in comparison to one another. The first postcanine (just posterior to

4233-458: The jugals or the orbitals. The maxilla of Thrinaxodon is also heavily pitted with foramina. The arrangement of foramina on the snout of Thrinaxodon resembles that of lizards, such as Tupinambis , and also bears a single large infraorbital foramen. As such, Thrinaxodon would have had non-muscular lips like those of lizards, not mobile, muscular ones like those of mammals. Without the infraorbital foramen and its associated facial flexibility, it

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4316-628: The largest component, with 23,236 ± 5,379 accepted genus names, of which 20,845 ± 4,494 are angiosperms (superclass Angiospermae). By comparison, the 2018 annual edition of the Catalogue of Life (estimated >90% complete, for extant species in the main) contains currently 175,363 "accepted" genus names for 1,744,204 living and 59,284 extinct species, also including genus names only (no species) for some groups. The number of species in genera varies considerably among taxonomic groups. For instance, among (non-avian) reptiles , which have about 1180 genera,

4399-682: The line of the Synapsida. Synapsida represents one of two major splitting points, under the clade Amniota, which also split into Sauropsida, the larger clade containing today's reptiles, birds and Crocodilia. Thrinaxodon represents a fossil transitional in morphology on the road to humans and other extant mammals. Procynosuchus Dvinia Cynosaurus Galesaurus Progalesaurus Thrinaxodon Platycraniellus Cynognathia Probainognathia There appear to be nine cranial features that successfully separate Thrinaxodon into four ontogenetic stages. The paper denotes that in general,

4482-404: The lizard genus Anolis has been suggested to be broken down into 8 or so different genera which would bring its ~400 species to smaller, more manageable subsets. Pelycosaur Pelycosaur ( / ˈ p ɛ l ɪ k ə ˌ s ɔːr / PEL -ih-kə-sor ) is an older term for basal or primitive Late Paleozoic synapsids , excluding the therapsids and their descendants. Previously,

4565-535: The medullary cavity of the metaphyses. Thrinaxodon was originally discovered in the Lystrosaurus Assemblage Zone of the Beaufort Group of South Africa. The genoholotype, BMNH R 511 , was in 1887 described by Richard Owen as the plesiotype of Galesaurus planiceps . In 1894 it was by Harry Govier Seeley made a separate genus with as type species Thrinaxodon liorhinus . Its generic name

4648-464: The midshaft of the humerus. While the vasculature is present, the humerus contains no secondary osteons. The radii and ulnae of Thrinaxodon represent roughly the same histological patterns. In contrast to the humerii and femora, the parallel-fibred region is far more distinct in the distal bones of the forelimb. The medullary cavities are surrounded by multiple layers of very poorly vascularized endosteal lamellar tissue, along with very large cavities near

4731-403: The most (>300) have only 1 species, ~360 have between 2 and 4 species, 260 have 5–10 species, ~200 have 11–50 species, and only 27 genera have more than 50 species. However, some insect genera such as the bee genera Lasioglossum and Andrena have over 1000 species each. The largest flowering plant genus, Astragalus , contains over 3,000 species. Which species are assigned to a genus

4814-424: The most important synapomorphy remained consistent between the two, and that was that the intercostal plates overlapped with one another. These evaluations led to the conclusion that they had not found a new species of Thrinaxodontidae, but yet they had found that Thrinaxodon occupied two different geographical regions, which today are separated by an immense expanse of ocean. This discovery was one of many to support

4897-428: The name could not be used for both. Johann Friedrich Blumenbach published the replacement name Ornithorhynchus in 1800. However, a genus in one kingdom is allowed to bear a scientific name that is in use as a generic name (or the name of a taxon in another rank) in a kingdom that is governed by a different nomenclature code. Names with the same form but applying to different taxa are called "homonyms". Although this

4980-403: The nasal passages from the rest of the mouth, allowing the Thrinaxodon to continue mastication without interrupting to breathe, an adaptation important for digestion. The nasals of Thrinaxodon are pitted with a large number of foramina. The nasals narrow anteriorly and expand anteriorly and articulate directly with the frontals, pre-frontals and lacrimals; however, there is no interaction with

5063-436: The nasal passages from the rest of the mouth, which would have given Thrinaxodon the ability to breathe uninterrupted, even if food had been kept in its mouth. This adaptation would have allowed the Thrinaxodon to mash its food to a greater extent, decreasing the amount of time necessary for digestion. The maxillae and palatines meet medially in the upper jaw developing a midline suture. The maxillopalatine suture also includes

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5146-420: The norm throughout this sub-section of the fossil record. The next step was to evaluate the size of the skull in the two different discovery groups, and in this study they found no difference between the two, the first indication that they may in fact be of the same species. The ribs were the final physiology to be cross-examined, and while they portrayed slight differences in the expanded ribs, against one another,

5229-403: The only appearance of labial cusps. Some older specimens have been found that possess no multiple-cups lower canines, possibly a response to old age or teeth replacement. Thrinaxodon shows one of the first occurrences of replacement teeth in cynodonts. This was discerned by the presence of replacement pits, which are situated lingual to the functional tooth in the incisors and postcanines. While

5312-485: The order Pelycosauria is paraphyletic in that the therapsids (the "higher" synapsids) have emerged from them. That means Pelycosauria is a grouping of animals that does not contain all descendants of its common ancestor, as is often required by phylogenetic nomenclature . In evolutionary taxonomy , Therapsida is a separated order from Pelycosauria, and mammals (having evolved from therapsids) are separated from both as their own class. This use has not been recommended by

5395-411: The physiological changes in the torso of Thrinaxodon . Such changes as the first appearance of a segmented rib compartment, in which Thrinaxodon expresses both thoracic and lumbar vertebrae. The thoracic segment of the vertebrae contain ribs with large intercostal plates that most likely assisted with either protection or supporting the main frame of the back. This newly developed arrangement allowed for

5478-408: The pre-Cenozoic, dominated by therapsids, early-Triassic cynodonts and some early Mammalia. Thrinaxodon was in fact the first burrowing cynodont that has been found, showing similar behavioral patterns to that of Trirachodon . The first burrowing vertebrate on record was the dicynodont synapsid Diictodon , and it is possible that these burrowing patterns had passed on to the future cynodonts due to

5561-431: The primary osteons assume less vasculature than many other bones as you begin to approach the subperiosteal surface. The femur contains very few bony trabeculae. The humerus differs from the femur in many regards, one of which being that there is a more extensive network of bony trabeculae in the humerus near the meduallary cavity of the bone. The globular osteocyte lacunae become more flattened as you get closer and closer to

5644-462: The proper soft tissue impressions this is nothing more than an assumption. The earliest discovery of a burrowing Thrinaxodon places the specimen found around 251 million years ago, a time frame surrounding the Permian–Triassic extinction event . Much of these fossils had been found in the flood plains of South Africa, in the Karoo Basin . This behavior had been seen at a relatively low occurrence in

5727-526: The provisions of the ICZN Code, e.g., incorrect original or subsequent spellings, names published only in a thesis, and generic names published after 1930 with no type species indicated. According to "Glossary" section of the zoological Code, suppressed names (per published "Opinions" of the International Commission of Zoological Nomenclature) remain available but cannot be used as the valid name for

5810-447: The skin were covered in rows of osteoderms , presumably overlain by horny scutes . The belly was covered in rectangular scutes, looking like those present in crocodiles . Parts of the skin not covered in scutes might have had naked, glandular skin like that found in some mammals. Dermal scutes are also found in a diverse number of extant mammals with conservative body types, such as in the tails of some rodents , sengis , moonrats ,

5893-422: The skull, the parietals lack a sagittal crest. The cranial roof is the narrowest just posterior to the parietal foramen, which is very nearly circular in shape. The temporal crests remain quite discrete throughout the length of the skull. The temporal fenestra have been found with ossified fasciae, giving evidence of some type of a temporal muscle attachment. The upper jaw contains a secondary palate which separates

5976-497: The specific name particular to the wolf. A botanical example would be Hibiscus arnottianus , a particular species of the genus Hibiscus native to Hawaii. The specific name is written in lower-case and may be followed by subspecies names in zoology or a variety of infraspecific names in botany . When the generic name is already known from context, it may be shortened to its initial letter, for example, C. lupus in place of Canis lupus . Where species are further subdivided,

6059-536: The sprawling position of basal tetrapods and the more upright posture present in current mammals. Thrinaxodon is prevalent in the fossil record in part because it was one of the few carnivores of its time, and was of a larger size than similar cynodont carnivores. Thrinaxodon was a small synapsid roughly the size of a fox and possibly covered in hair. The dentition suggests that it was a carnivore, focusing its diet mostly on insects, small herbivores and invertebrates. Their unique secondary palate successfully separated

6142-412: The standard format for a species name comprises the generic name, indicating the genus to which the species belongs, followed by the specific epithet, which (within that genus) is unique to the species. For example, the gray wolf 's scientific name is Canis lupus , with Canis ( Latin for 'dog') being the generic name shared by the wolf's close relatives and lupus (Latin for 'wolf') being

6225-485: The stapes was able to cover the fenestra ovalis. The remainder of this pit opens to an "un-ossified" region which comes somewhat close to the cochlear recess, giving one the assumption that inner ear articulation occurred directly within this region. The skull of Thrinaxodon is an important transitional fossil which supports the simplification of synapsid skulls over time. The most notable jump in bone number reduction had occurred between Thrinaxodon and Probainognathus ,

6308-403: The taxon is termed a synonym ; some authors also include unavailable names in lists of synonyms as well as available names, such as misspellings, names previously published without fulfilling all of the requirements of the relevant nomenclatural code, and rejected or suppressed names. A particular genus name may have zero to many synonyms, the latter case generally if the genus has been known for

6391-399: The term mammal-like reptile had been used, and pelycosaur was considered an order , but this is now thought to be incorrect and outdated. Because it excludes the advanced synapsid group Therapsida , the term is paraphyletic and contrary to modern formal naming practice. Thus the name pelycosaurs , similar to the term mammal-like reptiles , had fallen out of favor among scientists by

6474-429: The third lower incisor, which can assume a more dorsoventral orientation. The incisors are, for the most part, single functional teeth encompassing a broad, cone-like morphology. The canines of T. liorhinus possess small dorsoventrally-directed facets on their surfaces, which appear to be involved with occlusion (dentition alignment in upper- and lower jaw closure). Each canine possesses a replacement canine located within

6557-414: The tympanum and give the implications that this recess, in conjunction with the fenestra ovalis, outline the origin of the ear in Thrinaxodon . This is a new synapomorphy as this physiology had arisen in Thrinaxodon and had been conserved through late Cynodontia. The stapes contained a heavy cartilage plug, which was fit into the sides of the fenestra ovalis; however, only one half of the articular end of

6640-566: The values quoted are the mean of "accepted" names alone (all "uncertain" names treated as unaccepted) and "accepted + uncertain" names (all "uncertain" names treated as accepted), with the associated range of uncertainty indicating these two extremes. Within Animalia, the largest phylum is Arthropoda , with 151,697 ± 33,160 accepted genus names, of which 114,387 ± 27,654 are insects (class Insecta). Within Plantae, Tracheophyta (vascular plants) make up

6723-429: The virus species " Salmonid herpesvirus 1 ", " Salmonid herpesvirus 2 " and " Salmonid herpesvirus 3 " are all within the genus Salmonivirus ; however, the genus to which the species with the formal names " Everglades virus " and " Ross River virus " are assigned is Alphavirus . As with scientific names at other ranks, in all groups other than viruses, names of genera may be cited with their authorities, typically in

6806-415: Was scanned using a synchrotron , a tool used to observe the contents of the burrows in this experiment, and not damage the intact specimens. The synchrotron revealed an injured rhinesuchid , Broomistega putterilli , showing signs of broken or damaged limbs and two skull perforations, most likely inflicted by the canines of another carnivore. The distance between the perforations was measured in relation to

6889-751: Was taken from the Ancient Greek for "trident tooth", thrinax and odon . The specific name is Latinised Greek for "smooth-nosed". Thrinaxodon was initially believed to be isolated to that region. Other fossils in South Africa were recovered from the Normandien and Katberg Formations . It had not been until 1977 that additional fossils of Thrinaxodon had been discovered in the Fremouw Formation of Antarctica . Upon its discovery there, numerous experiments were done to confirm whether or not they had found

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