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50-855: Massetognathus ( / ˌ m æ s ɪ ˈ t ɒ ɡ n ə θ ə s / MASS -ə- TOG -nə-thəss ; Greek for "chewing muscle jaw") is an extinct genus of plant-eating traversodontid cynodonts . They lived during the Triassic Period about 235 million years ago, and are known from the Chañares Formation in Argentina and the Santa Maria Formation in Brazil. Massetognathus species measured to about 46 centimeters (1.51 feet) in length with an estimated weight between 1 and 1.5 kilograms (2.2 and 3.3 lb). Massetognathus

100-461: A trophic reconstruction of the environment, 55% of the specimens were herbivorous and 45% were faunivorous. All the herbivores are therapsids , and the most abundant by far is Massetognathus , representing 83.7% of all herbivorous specimens. One of the hallmarks of the Chañares assemblage is the numerical dominance of traversodontid cynodonts; with Massetognathus pascuali representing 62.3% of

150-407: 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 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

200-451: A high predation pressure on infant, juvenile and sub-adults is expected, and this, together with a high reproductive rate, may explain the overwhelming abundance of Massetognathus bones preserved. Massetognathus faunas from the middle to upper Triassic is best documented in the Santa Maria Formation in Brazil and the Chañares Formation in western Argentina. Chañares fauna was dominated by herbivorous small to medium-sized taxa . In

250-651: 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

300-401: A long dog-like tail. Like most cynodonts , there is some evidence that they laid eggs, were warm blooded, as indicated by the detailed structure of the bones, and had a body covered by hair. Massetognathus was a medium-sized cynodont, which documents different ontogenetic stages. It had the largest size of any cynodont in the Chañares assemblage with an approximate skull length ranging from

350-628: 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,

400-423: A progressively greater rotation more closely related to mammals, squamosal contact and medial expansion of the squamosal were crucial factors in the transforming the quadrate and the articulation of the cranium . The maxillae extend far out dorsally (with a downward slope) to a point about opposite the lower margins of the orbits , then curving downward and inward, present a broad ventral surface lateral to

450-409: 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

500-427: A rudimentary dental occlusion, feeding on ground level vegetation or on the lower branches of taller plants and shrubs. Medium-sized predators likely fed preferably on juvenile Massetognathus and dicynodonts . Additionally, the slightly larger Chanaresuchus and Pseudolagosuchus also preyed on individual Massetognathus that were not fully grown. Luperosuchus and an unnamed paracrocodylomorph represent

550-427: 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. ;

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600-455: 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

650-1162: Is classified as a cynodont in the superfamily Tritylodontoidea , the family Traversodontidae , and the subfamily Massetognathinae . Other members of Massetognathinae include the South African Dadadon and the Brazilian Santacruzodon . The cladogram is showing the phylogenetic position of Massetognathus and Massetognathinae within Traversodontidae. Cynognathus Diademodon Trirachodon Cricodon Langbergia Andescynodon Pascualgnathus Arctotraversodon Boreogomphodon Nanogomphodon Massetognathus Dadadon Santacruzodon Gomphodontosuchus Menadon Protuberum Exaeretodon Scalenodontoides There are four upper and three lower triangular incisors of modest size with canines that are relatively less developed. There are two rows of cheek teeth that are close together and diverge posteriorly. A short diastema separates

700-612: 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

750-491: Is formed along the western margin of South America during the breakup of Gondwana . Up to 4000 m of non-marine Triassic strata are preserved within the Ischigualasto -Villa Únion Basin. The Chañares Formation represented an extremely thick accumulation of volcanic tuffs that were deposited in wither eolian or lacustrine settings. The lack of stratification prompted Romer to further conclude that deposition in water

800-460: 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,

850-474: 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

900-621: 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

950-824: 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;

1000-487: The coronoid process , and less post canines compared to the other three species. M. major is known for having the largest skull out of the 4 species that can reach up to 204 mm. It had a distinctively narrow snout with the teeth being less curved compared to its sister taxa . There is a complete loss of the parietal foramen . Megagomphodon oligodens may have been derived from this species. In 1967, American paleontologist Alfred Romer named three new species under

1050-419: 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 ,

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1100-404: 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,

1150-442: 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

1200-515: The cheek teeth and canines. There is no significant contrast between the premolars and molars . There are generally 12 maxillary teeth . It has been established that Massetognathus with multi-cuspate post canines adapted to herbivory , moved the lower jaw posteriorly and dorsally during the power stroke of the occlusion . Massetognathus is the only cynodont from the Chañares Formation with clear adaptations for herbivory, with basined, labiolingually expanded upper and lower post-canines, ensuring

1250-437: The cynodont sample and 46.0% of all amniote remains recovered. Additionally, the number of sectorial-toothed cynodonts is approximately half as abundant as Massetognathus in the fauna. Massetognathus records suggest a gregarious habit and have been reported to live in burrows with other specimens. The Chañares Formation, where Romer first discovered Massetognathus crops out in the Ischigualasto -Villa Union Basin, which

1300-446: 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

1350-737: 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,

1400-428: The genus: Massetognathus pascuali , M. teruggi , and M. major during his expedition in western Argentina . In 1981, Brazilian paleontologist Mário Costa Barberena named the fourth species, Massetognathus ochagaviae on the basis of a specimen from the Santa Maria Formation in Brazil. After the discovery of M. pascuali and M. teruggi , Romer first believed that these skulls were representing growth stages due to

1450-406: The larger size of M. teruggi . However, after collecting multiple skull samples, they clearly sorted into two size groups, rather than showing growth stages of a single species. The size difference is also considerably greater between the two than that expected in sex differences which gave Romer another reason to believe that they were dealing with two species of a single genus . Massetognathus

1500-633: 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,

1550-511: The lower lithologic unit of the Chañares Formation, the matrix that encompasses the fossils were in a copious amount of volcanic ash indicating the possibility that lethal volcanic processes led to the demise of the fauna. Volcanic reactions could have also led to the landscape flooding and damming of local rivers also resulting in volcanism being the cause of mass mortality in the Chañares Formation. Genus The composition of

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1600-600: The lower lithologic unit of the Chañares Formation, where they are preserved almost exclusively within carbonate concretions. Fossilized bone preserved in concretion shows some of the best form of preservation, with dark brown bone surfaces exhibiting virtually no evidence of macroscopic weathering. The fossil accumulations of the Chañares assemblage are considered to be the product of two different taphonomic pathways: attritional accumulation associated with natural deaths of individuals by predation , disease and old age, and mass mortality of animals associated with volcanic events. In

1650-411: The mass mortality event, there is a clear bias towards preservation of individuals representing smaller-sized to mid-sized taxa such as Massetognathus . The mass mortality assemblage, with a large quantity of complete or partially articulated skeletons, shows some post-mortem sorting, followed by rapid burial that prevent the carcasses from being scavenged, crushed by species or exposed to weathering. In

1700-403: 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

1750-428: 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

1800-648: The only valid species for Chañares gomphodonts while the others are considered junior synonyms . Named by Alfred Romer , the specific name is in honor of Dr. Rosendo Pascual, Professor of Paleontology in the Universidad de la Plata, who accompanied his expedition during his stay in Western Argentina. M. teruggi is known to be the most common species of Chañares cynodonts. Named after the scientist and writer Dr. Mario Teruggi by Romer. M. teruggi skulls on average are approximately 45 percent larger than

1850-541: 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

1900-470: 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 the French botanist Joseph Pitton de Tournefort (1656–1708) is considered "the founder of the modern concept of genera". The scientific name (or

1950-408: 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 a species : see Botanical name and Specific name (zoology) . The rules for the scientific names of organisms are laid down in

2000-401: The skulls of M. pascuali and had a more defined sagittal crest . The dentary is less sharp and had 15 maxillaries compared to the 12 M. pascuali had. M. ochagaviae is known to be the most common species from the Santa Maria Formation , Rio Grande do Sul, Brazil. Named after Mário Costa Barberena . It had a higher skull and mandible, slightly dorsally pointed dentary ventral border under

2050-421: The smallest being 72 millimetres (2.8 in) to the largest 204 millimetres (8.0 in). The Middle Triassic Probainognathus and Massetognathus are the earliest non-mammalian cynodonts in the fossil record that show the initial steps of several phylogenetic transformations of the quadrate and can be characterized by several features: The rotation of the dorsal plate relative to the trochlea exhibits

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2100-497: 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,

2150-412: 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

2200-403: 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

2250-401: The tooth rows. The skull is low and the orbits face more dorsally than laterally with the nasals and frontals laying flat on top of the skull. In contrast to other cynodonts, the squamosal descends ventrally. At least 4 different species of Massetognathus has been discovered so far. The type species , M. pascuali , is the best-known species of the genus and is arguably considered to be

2300-404: The top predators in the Chañares Formation . They preyed on all the other members in the fauna, including fully grown dicynodonts and Massetognathus . Considering the abundance of the herbivorous cynodont Massetognathus , it is clear that this taxon represents the main food resource in the Chañares assemblage. Only a few forms were capable of preying on fully grown Massetognathus ; therefore,

2350-576: 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

2400-429: 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

2450-416: Was the smaller, plant-eating equivalent of the better-known Cynognathus with incisors, fang-like canines and flat-topped molars covered by low ridges, an adaptation for grinding tough plant stems, roots, and other plant materials. It had a low and flattened skull indicating that the specimen had a relatively shorter and broader snout than larger specimens. It was a fox sized animal with claws on its feet and

2500-470: Was unlikely. Instead, Romer envisioned the Chañares landscape “with tremendous quantities of volcanic ash in Pompeii -like fashion”. The formation included deposits of muddy streams transporting abundant volcanic detritus. Ash-flow sheets potentially were emplaced as mass flows on sub alluvial surfaces and in lakes that occupied the Ischigualasto -Villa Únion Basin. Tetrapod fossils have been found only in

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