Bisonalveus

Bisonalveus
Temporal range: 60–56 Ma
↓
 Early to Middle Tiffanian
Mandibula of Bisonalveus browni
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: †Cimolesta
Family: †Pantolestidae
Subfamily: †Pentacodontinae
Genus: †Bisonalveus
Species
  • B. browni (Gazin, 1956)
  • B. holtzmani (Gingerich, 1983)

Bisonalveus is an extinct genus of shrew-like[1] mammals that were presumably ground-dwelling and fed on plants and insects.[2] Bisonalveus fossils have been discovered in the upper Great Plains region of North America,[3] including sites in modern-day Wyoming,[2][4] North Dakota,[2] Montana,[2] and Alberta.[5] The fossils have been dated to 60 million years ago, during the Tiffanian North American Stage of the Palaeocene epoch.[1][2][6] Bisonalveus is the last known genus of the Pentacodontinae sub-family to have arisen, replacing the genus Coriphagus in the early Tiffanian.[2][6] Bisonalveus itself appears to have gone extinct by the middle Tiffanian.[2]

Bisonalveus is represented by two known species: B. browni (Gazin, 1956) and B. holtzmani (Gingerich, 1983).[2][4][6]

Bisonalveus browni

Bisonalveus browni was discovered in 1956 from fossilized jaw fragments (including molars). Later discovered fossils included front teeth and a dagger-like canine tooth with an enameled groove.[1][5] The canines do not have a corresponding surface on the lower jaw, indicating that they were not used for chewing, but rather for stabbing. That would mean Bisonalveus was a predator, presumably hunting small insects. The grooves on the canines may have been used for delivering venomous saliva into the prey, which would thereby make Bisonalveus one of the few known venomous mammals. Perhaps, like the modern solenodon, Bisonalveus bit its victims to inject its toxic saliva and buried the immobilized prey in a cache for later consumption.[1] However, because several nonvenomous mammals (such as baboons and other primates) have similar grooves on their teeth, some scientists have questioned whether these grooves truly indicate venom delivery.[7][8] If Bisonalveus was a forager, the grooves might have served the purpose of introducing (nonvenomous) saliva for digestive reasons.[1] Alternatively, the grooves might have been useful as they increased the amount of enamel on the canines, thereby strengthening these slender teeth.[3]

Bisonalveus holtzmani

Bisonalveus holtzmani is named for Dr. Richard Holtzman, who, in 1978, described the first tooth that was later determined to belong to this species. B. holtzmani can be distinguished from B. browni in that it is about 30% larger.[2]

References

  1. ^ a b c d e Roach, John (22 June 2005). "Extinct Mammal Had Venomous Bite, Fossils Suggest". National Geographic News. The National Geographic Society. Archived from the original on June 25, 2005. Retrieved 25 July 2015.
  2. ^ a b c d e f g h i Gingerich, Phillip D. (31 December 1983). "New Adapisoricidae, Pentacodontidae, and Hyopsodontidae (Mammalia, Insectivora and Condylarthra) from the Late Paleocene of Wyoming and Colorado" (PDF). Contributions from the Museum of Paleontology. 26 (11): 227–255. Retrieved 4 August 2015.
  3. ^ a b Fulwood, Ethan (7 May 2015). "OBSCURE EUTHERIANS OF THE PALEOCENE: Pentacodontids". Of Omomys and Men. Retrieved 4 August 2015.
  4. ^ a b Gazin, Charles Lewis (28 February 1956). "Paleocene mammalian faunas of the Bison basin in south-central Wyoming" (PDF). Smithsonian Miscellaneous Collections. 131 (6): 1–57. Retrieved 4 August 2015.
  5. ^ a b Fox, Richard C.; Scott, Craig S. (23 June 2005). "First evidence of a venom delivery apparatus in extinct mammals". Nature. 435 (7045): 1091–1093. Bibcode:2005Natur.435.1091F. doi:10.1038/nature03646. PMID 15973406. S2CID 4322624.
  6. ^ a b c Gunnell, Gregg F.; Bown, Thomas; Bloch, Jonathan Ivan; Boyer, Doug M. "Proteutheria". Evolution of Tertiary Mammals of North America Volume 2: Small Mammals, Xenarthrans, and Marine Mammals (1 ed.). Cambridge University Press. pp. 63–81. Retrieved 4 August 2015.
  7. ^ Folinsbee K.; Muller J. & Reisz R.R. (2007). "Canine grooves: morphology, function, and relevance to venom". Journal of Vertebrate Paleontology. 27 (2): 547–551. doi:10.1671/0272-4634(2007)27[547:CGMFAR]2.0.CO;2.
  8. ^ Orr C.M.; et al. (2007). "The comparative method and the inference of venom delivery systems in fossil mammals". Journal of Vertebrate Paleontology. 27 (2): 541–546. doi:10.1671/0272-4634(2007)27[541:TCMATI]2.0.CO;2.

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