Thylophorops

Thylophorops
Temporal range: Pliocene
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Marsupialia
Order: Didelphimorphia
Family: Didelphidae
Subfamily: Didelphinae
Genus: Thylophorops
Ameghino 1908
Type species
Thylophorops chapadmalensis
Ameghino 1908
Species
  • Thylophorops chapadmalensis
  • Thylophorops lorenzinii
  • Thylophorops perplana/perplanus

Thylophorops is an extinct genus of didelphine opossums from the Pliocene of South America. Compared to their close didelphine cousins like the living Philander and Didelphis (and like the still living Lutreolina) opossums, Thylophorops displays specialization towards carnivory, and one species, T. lorenzinii, is the largest known opossum of all time,[1] which could imply a macropredatory role.[2][3]

Taxonomy

Thylophorops is rather consistently recovered as a didelphine opossum, most often compared to and usually falling within the Didelphis, Philander and Lutreolina group.[4] Within Thylophorops itself, there are three recognized species:

  • T. chapadmalensis: The type species, known from several Pliocene (Chapadmalalan-Uquian) formations in Argentina. It is known from a variety of skeletal remains, rendering it a fairly common species in the area. It is a large opossum species, comparable to the modern Virginia opossum in size.
  • T. lorenzinii: Currently known only from the holotype MLP 08-III-10-1, a lower jaw and skull fragment, coming from Late Pliocene deposits in Buenos Aires. It represents a juvenile individual, estimated to weight around 7 kilograms (15 lb), making it the largest known didelphid of all time.[5]
  • T. perplana/perplanus: The earliest known species, occurring in Early Pliocene Argentinian deposits.[6][7]

Biology

Thylophorops species (as well as several other contemporary opossum genera[8]) show a high degree of speciation towards carnivory compared to the still living didelphines. Their premolar and molar teeth were proportionally larger than those of living opossums and their grinding facets imply a more dedicated shearing action; these have been interpreted as "omnivory leading towards carnivory" in Goin et al. 2009[9] and as more specialized carnivory in posterior studies.[10][11]

There is evidence that T. chapadmalensis re-appropriated burrows from other digging mammals, as well as outright consuming them. Thylophorops species as a whole tended to be terrestrial rather than arboreal.[12]

Paleoecology

Thylophorops lived at a time when South America's older predatory guilds were dismantling. It co-existed with only a few sparassodont and phorusrhacid taxa like Thylacosmilus and Llallawavis,[13][14] and it, as well as similar opossum species, evolved to fill the ecological blanks. A similar case is observed with the carnivorous armadillo Macroeuphractus, a product of this same era of faunal turn-overs.[15]

As mentioned above, there is evidence of T. chapadmalensis predating on contemporary caviomorphs and appropriating burrows, from them or other mammals such as armadillos.[16]

References

  1. Goin, Francisco J.; Natalia Zimicz; Martin de los Reyes; Leopoldo Soibelzon (2009). "A new large didelphid of the genus Thylophorops (Mammalia: Didelphimorphia: Didelphidae), from the late Tertiary of the Pampean Region (Argentina)". Zootaxa. 2005: 35–46.
  2. Prevosti, Francisco J.; Analía Forasiepi; Natalia Zimicz (2013). "The Evolution of the Cenozoic Terrestrial Mammalian Predator Guild in South America: Competition or Replacement?". Journal of Mammalian Evolution. 20: 3–21. doi:10.1007/s10914-011-9175-9.
  3. Mammalian predator–prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): new ichnological and taphonomic evidence Article in Historical Biology · October 2015 DOI: 10.1080/08912963.2015.1089868
  4. M. C. McKenna and S. K. Bell. 1997. Classification of Mammals Above the Species Level 1-640
  5. Goin, Francisco J.; Natalia Zimicz; Martin de los Reyes; Leopoldo Soibelzon (2009). "A new large didelphid of the genus Thylophorops (Mammalia: Didelphimorphia: Didelphidae), from the late Tertiary of the Pampean Region (Argentina)". Zootaxa. 2005: 35–46.
  6. Goin, Francisco J.; Natalia Zimicz; Martin de los Reyes; Leopoldo Soibelzon (2009). "A new large didelphid of the genus Thylophorops (Mammalia: Didelphimorphia: Didelphidae), from the late Tertiary of the Pampean Region (Argentina)". Zootaxa. 2005: 35–46.
  7. Goin, Francisco J.; Ulyses F. J. Pardinas (1996). "Revision de las especies del genero Hyperdidelphys Ameghino, 1904 (Mammalia, Marsupialia, Didelphidae. Su significacion filogenetica, estratigrafica y adaptativa en el Neogeno del Cono Sur sudamericano". Estudios Geologicos. 52 (5–6): 327–359. doi:10.3989/egeol.96525-6275.
  8. Mammalian predator–prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): new ichnological and taphonomic evidence Article in Historical Biology · October 2015 DOI: 10.1080/08912963.2015.1089868
  9. Goin, Francisco J.; Natalia Zimicz; Martin de los Reyes; Leopoldo Soibelzon (2009). "A new large didelphid of the genus Thylophorops (Mammalia: Didelphimorphia: Didelphidae), from the late Tertiary of the Pampean Region (Argentina)". Zootaxa. 2005: 35–46.
  10. Prevosti, Francisco J.; Analía Forasiepi; Natalia Zimicz (2013). "The Evolution of the Cenozoic Terrestrial Mammalian Predator Guild in South America: Competition or Replacement?". Journal of Mammalian Evolution. 20: 3–21. doi:10.1007/s10914-011-9175-9.
  11. Mammalian predator–prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): new ichnological and taphonomic evidence Article in Historical Biology · October 2015 DOI: 10.1080/08912963.2015.1089868
  12. Mammalian predator–prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): new ichnological and taphonomic evidence Article in Historical Biology · October 2015 DOI: 10.1080/08912963.2015.1089868
  13. Prevosti, Francisco J.; Analía Forasiepi; Natalia Zimicz (2013). "The Evolution of the Cenozoic Terrestrial Mammalian Predator Guild in South America: Competition or Replacement?". Journal of Mammalian Evolution. 20: 3–21. doi:10.1007/s10914-011-9175-9.
  14. Mammalian predator–prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): new ichnological and taphonomic evidence Article in Historical Biology · October 2015 DOI: 10.1080/08912963.2015.1089868
  15. Prevosti, Francisco J.; Analía Forasiepi; Natalia Zimicz (2013). "The Evolution of the Cenozoic Terrestrial Mammalian Predator Guild in South America: Competition or Replacement?". Journal of Mammalian Evolution. 20: 3–21. doi:10.1007/s10914-011-9175-9.
  16. Mammalian predator–prey relationships and reoccupation of burrows in the Pliocene of the Pampean Region (Argentina): new ichnological and taphonomic evidence Article in Historical Biology · October 2015 DOI: 10.1080/08912963.2015.1089868
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