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21-398: Borhyaenidae is an extinct metatherian family of low-slung, heavily built predatory mammals in the order Sparassodonta . Borhyaenids are not true marsupials , but members of a sister taxon , Sparassodonta. Like most metatherians, borhyaenids and other sparassodonts are thought to have had a pouch to carry their offspring around. Borhyaenids had strong and powerful jaws , like those of

42-510: A closer evolutionary relationship between marsupials and placental mammals than either has with the monotremes, as does most genetic and molecular evidence. The earliest possible known metatherian is Sinodelphys szalayi , which lived in China during the Early Cretaceous around 125 million years ago (mya). This makes it a contemporary to some early eutherian species that have been found in

63-509: A famous debate , which is said to exemplify the two major deviations in biological thinking at the time – whether animal structure was due to function or evolution. Most taxa differ morphologically from other taxa. Typically, closely related taxa differ much less than more distantly related ones, but there are exceptions to this. Cryptic species are species which look very similar, or perhaps even outwardly identical, but are reproductively isolated. Conversely, sometimes unrelated taxa acquire

84-525: A similar appearance as a result of convergent evolution or even mimicry . In addition, there can be morphological differences within a species, such as in Apoica flavissima where queens are significantly smaller than workers. A further problem with relying on morphological data is that what may appear morphologically to be two distinct species may in fact be shown by DNA analysis to be a single species. The significance of these differences can be examined through

105-417: Is one of two groups placed in the clade Theria alongside Eutheria , which contains the placentals. Remains of metatherians have been found on all of Earths continents. Distinctive characteristics ( synapomorphies ) of Metatheria include: a prehensile tail , the development of a capitular tail on the humerus, the loss of tooth replacement on the 2nd and 5th premolars and the retention of decidious teeth on

126-748: The Pliocene , as well as the Polydolopimorphia , which likely had a wide range of diets. Metatherians then declined in diversity in South America during the Late Eocene as well as the later Oligocene epoch. The oldest known Australian marsupials are from the early Eocene, and are thought to have arrived in the region after having dispersed via Antarctica from South America. During the Oligocene epoch, Australian metatherians radiated rapidly, which contributed most to

147-705: The Pliocene - Pleistocene as part of the Great American interchange ). Metatherians first arrived in Afro-Arabia during the Paleogene , probably from Europe, including the possible peradectoid Kasserinotherium from the Early Eocene of Tunisia and the herpetotheriid Peratherium africanum from the Early Oligocene of Egypt and Oman. The youngest African metatherian is the possible herpetotheriid Morotodon from

168-670: The Cenozoic. The two major groups of Cenozoic Laurasian metatherians, the opossum-like herpetotheriids and peradectids persisted into the Miocene before becoming extinct, with the North American herpetotheriid Herpetotherium , the European herpetotheriid Amphiperatherium and the peradectids Siamoperadectes and Sinoperadectes from Asia being the youngest Laurasian non-marsupial metatherians (with marsupials invading North America during

189-646: The Late Cretaceous, metatherians were more diverse than eutherians in North America. Metatherians underwent a severe decline during the Cretaceous–Paleogene extinction event , more severe than that suffered by contemporary eutherians and multituberculates , and were slower to recover diversity. Morphological and species diversity of metatherians in Laurasia remained low in comparison to eutherians throughout

210-627: The discovery that borhyaenids are more closely related to proborhyaenids and thylacosmilids than other sparassodonts, the family has been reduced to seven species in four genera. The most studied borhyaenids are the Early Miocene taxa , particularly from fossil sites in the southernmost part of Patagonia . One species, Australohyaena antiqua , is known from the Oligocene ( Deseadan ); although some Oligocene basal borhyaenoids were once considered to be borhyaenids, all other unambiguous members of

231-533: The end of the Early Miocene. [REDACTED] This prehistoric mammal -related article is a stub . You can help Misplaced Pages by expanding it . Metatheria Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals . First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as well as many extinct non-marsupial relatives. It

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252-1367: The global peak in metatherian diversity during the Early Miocene. The only known Antarctic metatherians are from the Early Eocene La Meseta Formation of the Antarctic Peninsula , where they are the most diverse group of mammals, and include marsupials as well as polydolopimorphians. Below is a metatherian cladogram from Wilson et al. (2016): Holoclemensia Pappotherium Sulestes Oklatheridium Tsagandelta Lotheridium Deltatheroides Deltatheridium Nanocuris Atokatheridium Gurlin Tsav skull Borhyaenidae Mayulestes Jaskhadelphys Andinodelphys Pucadelphys Asiatherium Iugomortiferum Kokopellia Aenigmadelphys Anchistodelphys Glasbius Pediomys Pariadens Eodelphis Didelphodon Turgidodon Alphadon Albertatherium Marsupialia Cladogram after : Deltatheriidae Kokopellia Asiatherium Peradectidae Stagodontidae Pucadelphyidae Sparassodonta Amphiperatherium Peratherium Herpetotherium Marsupialia Morphology (biology) This includes aspects of

273-502: The group are now considered to be restricted to the Miocene . The fossil record of this group after the Early Miocene is poor, and only fragmentary remains attest to their presence in the Late Miocene . However, the only confidently identified Late Miocene borhyaenid specimen, Stylocynus paranensis, comes from a site which is known to have Early Miocene fossils mixed in with Late Miocene ones, and so it may be that this group did not survive

294-528: The late Early Miocene of Uganda . Metatherians arrived in South America from North America during the latest Cretaceous or Paleocene and underwent a major diversificiation, with South American metatherians including both the ancestors of extant marsupials as well as the extinct Sparassodonta , which were major predators in South American ecosystems during most of the Cenozoic , up until their extinction in

315-413: The lower fifth premolars, the lower canines outwardly diverge from each other, the angular process on the dentary is equal to or less than half the length of the ramus , the dentary has a posterior masseteric shelf, and the lower 5th premolar has a "very trenchant" cristid obliqua/ectolophid. The permanent deciduous lower 5th premolars are molar like and were historically identified as 1st molars, with

336-465: The outward appearance (shape, structure, color, pattern, size), i.e. external morphology (or eidonomy ), as well as the form and structure of internal parts like bones and organs , i.e. internal morphology (or anatomy ). This is in contrast to physiology , which deals primarily with function. Morphology is a branch of life science dealing with the study of the gross structure of an organism or taxon and its component parts. The etymology of

357-450: The same area. However, Bi et al. (2018) reinterpreted Sinodelphys as an early member of Eutheria. The oldest uncontested metatherians are now 110 million year old fossils from western North America. Metatherians were widespread in Asia and North America during the Late Cretaceous, including both Deltatheroida and Marsupialiformes, with fossils also known from Europe during this time. During

378-437: The third premolar found in basal therians being lost, leaving 4 premolars in the halves of each jaw. The relationships between the three extant divisions of mammals ( monotremes , marsupials, and placentals ) was long a matter of debate among taxonomists . Most morphological evidence comparing traits, such as the number and arrangement of teeth and the structure of the reproductive and waste elimination systems , favors

399-484: The unrelated placentalians Hyaenodon and Andrewsarchus , for crushing bones . Borhyaenids grew up to an average of 5 to 6 feet (1.5 to 1.8 m) long. Originally, the borhyaenids were considered one of the most diverse groups of sparassodonts, including all species not originally included in the Thylacosmilidae . However, in recent years, with the elevation of most sparassodont subfamilies to family rank and

420-576: The use of allometric engineering in which one or both species are manipulated to phenocopy the other species. A step relevant to the evaluation of morphology between traits/features within species, includes an assessment of the terms: homology and homoplasy . Homology between features indicates that those features have been derived from a common ancestor. Alternatively, homoplasy between features describes those that can resemble each other, but derive independently via parallel or convergent evolution . The invention and development of microscopy enabled

441-763: The word "morphology" is from the Ancient Greek μορφή ( morphḗ ), meaning "form", and λόγος ( lógos ), meaning "word, study, research". While the concept of form in biology, opposed to function , dates back to Aristotle (see Aristotle's biology ), the field of morphology was developed by Johann Wolfgang von Goethe (1790) and independently by the German anatomist and physiologist Karl Friedrich Burdach (1800). Among other important theorists of morphology are Lorenz Oken , Georges Cuvier , Étienne Geoffroy Saint-Hilaire , Richard Owen , Carl Gegenbaur and Ernst Haeckel . In 1830, Cuvier and Saint-Hilaire engaged in

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