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Peradectes és un gènere de metateri extint de l'Eocè, que estava emparentat amb els opòssums d'avui en dia. Se n'han trobat restes fòssils al Canadà i els Estats Units.[1] Igual que els opòssums, es tractava d'un animal arborícola i de dieta omnívora.
Peradectes és un gènere de metateri extint de l'Eocè, que estava emparentat amb els opòssums d'avui en dia. Se n'han trobat restes fòssils al Canadà i els Estats Units. Igual que els opòssums, es tractava d'un animal arborícola i de dieta omnívora.
Peradectes is an extinct genus of small metatherian mammals known from the latest Cretaceous[1] to Eocene of North and South America and Europe.[2] The first discovered fossil of P. elegans, was one of 15 Peradectes specimens described in 1921 from the Mason pocket fossil beds in Colorado.[3] The monophyly of the genus has been questioned.[4]
The genus name is derived from the Greek for “pouch” (pera-) and “biter” (-dectes), indicating a marsupial thought to engage primarily in carnivory.[3]
The exact placement of Peradectes and its relationships have been uncertain. Some definitions of the group may be polyphyletic, and the extinct genus Thylacodon was thought by some to be synonymous with Peradectes; however, the two are now considered separate genera.[4]
It is known to be a metatherian and further a member of the crown clade Marsupialia along with other extinct and extant groups due to distinct marsupial dentition and jaw anatomy.[5] Once thought to be a member of Didelphidae along with modern opossums,[3][6] it is now classified within a separate family, Peradectidae, due in part to the predilambdodont, rather than true dilambdodont, upper molars.[4][7][8] Some classifications recognize a subfamily within Peradectidae, Peradectinae, which includes at least Peradectes, Thylacodon, and Nanodelphys.[1][9]
Though no longer believed to be didelphids, the opossum-like Peradectes and its relatives in Peradectidae may represent a primitive step in the evolution of opossums. A “peradectid or peradectid-like ancestor” may have given rise to didelphids in the Cretaceous.[10]
As with other mammals, due to the hardness of the enamel, teeth and jaws make up much of the fossil record of Peradectes. The jaw of the type specimen P. elegans is slender with a medially inflected angle as in other marsupials like opossums, and it possesses simple premolars and comparatively large canine teeth.[3] Peradectes upper molars are distinctive, noted to have a larger metacone than protocone, a buccally oriented stylar shelf with cusp B as the largest cusp, and a short postmetaconule crista.[11] Some specimens are also described as having a robust skull with a short snout and vertical directed lower incisors.[12]
Peradectes fossils tend to be small, with individual teeth for example measuring no larger than 1.5 mm.[9] One particular specimen assigned to Peradectes has postcranial anatomy common to modern arboreal marsupials, including reduced transverse processes of the lumbar vertebrae, a posterior anticlinal vertebra, somewhat short metatarsals, and a comparatively long tail (1.5-2 times the length of the head and body) thought to have been prehensile.[12]
Fossils of the group Peradectidae, of which Peradectes is a part, have been found primarily in the Northern Hemisphere.[8] It may be the only marsupial genus known from the Tiffanian North American land mammal age in the Paleocene, retaining its wide-ranging distribution from the preceding Torrejonian age.[1]
Specimens have been found at the Messel site of Germany[12] and other parts of that country and southern England.[2] Though peradectids were most common in the northern continents, specimens assigned to Peradectes are also known from South America.[1][10] The existence of Peradectes in South America is significant in terms of broader marsupial evolution, as there is evidence that ancestors of modern Australian marsupials diverged from the lineage leading to modern New World marsupials on that continent.[13]
The skeletal anatomy of Peradectes is consistent with at least a partially arboreal lifestyle.[12] Analyses have also suggested a partially scansorial life mode (climbing but not necessarily living in trees) for at least some Peradectes species, along with frugivorous or insectivorous feeding.[14]
Peradectes is an extinct genus of small metatherian mammals known from the latest Cretaceous to Eocene of North and South America and Europe. The first discovered fossil of P. elegans, was one of 15 Peradectes specimens described in 1921 from the Mason pocket fossil beds in Colorado. The monophyly of the genus has been questioned.
Il peradecte (gen. Peradectes) è un mammifero estinto, appartenente ai marsupiali. Visse tra il Paleocene inferiore e l'Eocene medio (circa 65 - 43 milioni di anni fa) e i suoi resti fossili sono stati ritrovati in Europa e in Nordamerica.
Questo animale doveva assomigliare molto a un piccolo opossum sudamericano (gen. Marmosa); La lunghezza del corpo non doveva superare i 10 centimetri, mentre quella della coda poteva sfiorare i 20 centimetri. Peradectes, come molte forme attuali, era dotato di una coda molto lunga e probabilmente prensile, come indicato dalla struttura delle vertebre caudali. Rispetto ad altre forme simili ma più antiche (come Alphadon e Albertatherium), Peradectes mostra una riduzione di tutte le cuspidi stilari dei molari.
Peradectes venne descritto per la prima volta nel 1921 da Matthew e Granger, sulla base di fossili ritrovati in Nordamerica in strati del Paleocene superiore. La specie tipo è Peradectes elegans, molto diffusa nel Paleocene superiore nordamericano (Alberta, Montana, Colorado, North Dakota, Wyoming). La specie Peradectes minor, risalente al Paleocene inferiore del Montana, è considerata uno dei più antichi membri dei marsupiali propriamente detti (Clemens, 2006). Altre specie nordamericane sono P. californicus, P. chesteri, P. coprexeches, P. gulottai, P. protinnominatus. In Europa sono noti fossili di Peradectes principalmente in Francia e in Germania, ma non sono stati attribuiti ad alcuna specie nota. In particolare, i fossili tedeschi provengono dal giacimento a conservazione eccezionale di Messel e sono pressoché completi, con tanto di impronta dei tessuti molli.
Peradectes è un membro dei Notometatheria, il gruppo di marsupiali americani attualmente rappresentati dagli opossum. Sembra che Peradectes e le forme affini (Peradectidae) si siano evoluti da antenati del Cretaceo come Alphadon.
Peradectes mostra caratteristiche dello scheletro compatibili con uno stile di vita arboricolo. La lunga coda prensile doveva essere molto utile per spostarsi fra i rami, e la sua dieta doveva essere onnivora o insettivora.
Il peradecte (gen. Peradectes) è un mammifero estinto, appartenente ai marsupiali. Visse tra il Paleocene inferiore e l'Eocene medio (circa 65 - 43 milioni di anni fa) e i suoi resti fossili sono stati ritrovati in Europa e in Nordamerica.
Peradectes is een geslacht van uitgestorven buideldier uit de Peradectidae. Deze opossumachtige dieren leefden van het Paleoceen en Eoceen, ongeveer 65 tot 43 miljoen jaar geleden, in Europa, Noord- en Zuid-Amerika.[1]
De typesoort Peradectes elegans werd in 1921 door William Diller Matthew en Walter Willis Granger beschreven en deze soort was in het Paleoceen wijdverspreid in Noord-Amerika. P. minor uit het Vroeg-Paleoceen van Montana wordt beschouwd als één van de oudste buideldieren.[2] In Zuid-Amerika leefde tijdens het Paleoceen P. austrinum met fossiele vondsten in de Santa Lucía-formatie in Bolivia en Laguna Umayo in Peru.[3] In Europa zijn fossielen van Peradectes gevonden in Frankrijk en Duitsland. In Grube Messel zijn vrijwel complete fossielen uit het Midden-Eoceen gevonden met afdrukken van de zachte weefsels.
Met een lichaamslengte van ongeveer tien centimeter en een staart van twintig centimeter had Peradectes het formaat van een dwergbuidelrat. Het skelet wijst op een boombewonende leefwijze. De bouw van de staartwervels wijst er op dat Peradectes een grijpstaart had. Het was een frugivoor of insectivoor.[4]
Bronnen, noten en/of referentiesPeradectes is een geslacht van uitgestorven buideldier uit de Peradectidae. Deze opossumachtige dieren leefden van het Paleoceen en Eoceen, ongeveer 65 tot 43 miljoen jaar geleden, in Europa, Noord- en Zuid-Amerika.
