''Peradectes'' is an extinct genus of small metatherian mammals known from the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

Korth, W. W. (2008). Marsupialia. In C. M. Janis, G. F. Gunnell, & M. D. Uhen (Eds.)
Evolution of Tertiary Mammals of North America: Volume 2, Small Mammals, Xenarthrans, and Marine Mammals
Cambridge: Cambridge University Press. and

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

of North and South America through the

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

of North America and parts of Europe.Czaplewski, J. J. (Ed.). (n.d.)
Paleobiology Database Navigator
Retrieved March 5, 2020. The first discovered fossil of ''P. elegans'', was one of 15 ''Peradectes'' specimens described in 1921 from the Mason pocket fossil beds in Colorado.Matthew, W., & Granger, W. (1921)
New genera of Paleocene mammals
(American Museum novitates ; no. 13). New York City: By order of the Trustees of The American Museum of Natural History.

Etymology

The genus name is derived from the Greek for “pouch” (''pera''-) and “biter” (-''dectes''), indicating a marsupial thought to engage primarily in

carnivory A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, adipose tissue, f ...

Taxonomy and relationships

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.Williamson, T.E., Brusatte, S.L., Carr, T.D., Weil, A. & Standhardt, B.R. (2012
The phylogeny and evolution of Cretaceous–Palaeogene metatherians: cladistic analysis and description of new early Palaeocene specimens from the Nacimiento Formation
New Mexico, Journal of Systematic Palaeontology, 10:4, 625-651. It is known to be a

metatherian 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 ...

and further a member of the crown clade

Marsupialia Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a pou ...

along with other extinct and extant groups due to distinct marsupial dentition and jaw anatomy. Once thought to be a member of Didelphidae along with modern opossums, it is now classified within a separate family, Peradectidae, due in part to the predilambdodont, rather than true dilambdodont, upper molars.Horovitz, I., Bloch, Martin, J., Ladevèze, S., Kurz, C. and Sánchez-Villagra M.R. (2009)
Cranial anatomy of the earliest marsupials and the origin of opossums
PLoS One 4(12):e8278. Some classifications recognize a subfamily within Peradectidae, Peradectinae, which includes at least ''Peradectes'', ''Thylacodon'', and ''Nanodelphys''.Korth, W. (1994)
Middle Tertiary Marsupials (Mammalia) from North America
Journal of Paleontology, 68(2), 376-397. 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 Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered North A ...

. A “peradectid or peradectid-like ancestor” may have given rise to didelphids in the Cretaceous.Marshall, L.G. & de Muizon, C. (1988)
The dawn of the Age of Mammals in South America
National Geographic Research, 4(1):23-55.

Description

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. ''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. Some specimens are also described as having a robust skull with a short snout and vertical directed lower incisors. ''Peradectes'' fossils tend to be small, with individual teeth for example measuring no larger than 1.5 mm. 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.

Distribution

Fossils of the group Peradectidae, of which ''Peradectes'' is a part, have been found primarily in the Northern Hemisphere. It may be the only marsupial genus known from the

Tiffanian The Tiffanian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 60,200,000 to 56,800,000 years BP lasting . It is usually co ...

North American land mammal age in the Paleocene, retaining its wide-ranging distribution from the preceding Torrejonian age. Specimens have been found at the Messel site of Germany and other parts of that country and southern England. Though peradectids were most common in the northern continents, specimens assigned to ''Peradectes'' are also known from South America. 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.

Palaeoecology

The skeletal anatomy of ''Peradectes'' is consistent with at least a partially arboreal lifestyle.Rose, K.D (2012). The importance of Messel for interpreting Eocene Holarctic mammalian faunas. Palaeobiodiversity and Palaeoenvironments 92, 631–647. 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 A frugivore is an animal that thrives mostly on raw fruits or succulent fruit-like produce of plants such as roots, shoots, nuts and seeds. Approximately 20% of mammalian herbivores eat fruit. Frugivores are highly dependent on the abundance and ...

insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores were ...

feeding.Kurz, C. (2005)
Ecomorphology of opossum-like marsupials from the Tertiary of Europe and a comparison with selected taxa
Kaupia, 14, 21-26.

References

{{Taxonbar, from=Q16912550 Prehistoric mammals