Skip to main content Accessibility help
×
Home

New specimens and neotype designation of Thisbemys brevicrista (Rodentia, Ischyromyidae) from the middle Eocene clarify the distinction between T. corrugatus and T. plicatus

  • Deborah K. Anderson (a1)

Abstract

Newly discovered mandibles and lower dentition of the middle Eocene rodent Thisbemys brevicrista from the Green River Basin, Wyoming, are the basis for a species re-diagnosis. Previously, only the upper dentition and a partial maxilla of T. brevicrista were known from Br3. New specimens from Br2 now include the lower molars, additional upper molars, and maxillary fragments including a partial zygomatic arch that preserves the relationship of the arch to the first upper molar. In addition, the presence of T. brevicrista at Br2 documents the co-existence of T. brevicrista with T. perditus, T. nini, T. plicatus, and T. corrugatus. Formerly, the latter two species were differentiated primarily using stratigraphy. Now, morphology and size can also be used. Thisbemys brevicrista is intermediate in size between T. plicatus and T. corrugatus, and can readily be distinguished from these species based on unique features of the upper and lower molars, which include an additional loph on the two anterior upper molars and a complete metalophid on m1-3. The original type specimen of T. brevicrista appears to be lost, thus a neotype is designated as part of the re-diagnosis. Discovery and description of the lower dentition and mandibles of T. brevicrista clarifies the alpha taxonomy of this species, and increases its utility for studies of phylogenetic relationships and for documenting Eocene mammalian diversity patterns.

Copyright

References

Hide All
Anderson, D.K., 2008, Ischyromyidae, in Janis, C.M., Gunnell, G.F., and Uhen, M.D., eds., Evolution of Tertiary Mammals of North America: New York, Cambridge University Press, v. 2, p. 311325.
Boyer, D.M., 2008, Relief index of second mandibular molars is a correlate of diet among prosimian primates and other euarchontan mammals: Journal of Human Evolution, v. 55, p. 11181137, doi:10.1016/j.jhevol.2008.08.002.
Boyer, D.M., Evans, A.R., and Jernvall, J., 2010, Evidence of dietary differentiation among Late Paleocene–Early Eocene plesiadapids (Mammalia, Primates): American Journal of Physical Anthropology, v. 142, p. 194210, doi: 10.1002/ajpa.21211.
Bowditch, T.E., 1821, An Analysis of the Natural Classifications of Mammalia for the Use of Students and Travelers: Paris, J. Smith, 115 p.
Butler, P.M., 1985, Homologies of molar cusps and crests, and their bearing on assessments of rodent phylogeny, in Luckett, W.P., and Hartenberger, J.-L., eds., Evolutionary Relationships among Rodents: A Multidisciplinary Analysis: New York, Plenum Press, p. 381401.
Cox, P.G., Rayfield, E.J., Fagan, M.J., Herrel, A., Pataky, T.C., and Jeffery, N., 2012, Functional evolution of the feeding system in rodents: PLoS ONE, v. 7, e36299, doi: 10.1371/journal.pone.0036299.
Eaton, J.G., 1982, Paleontology and correlation of Eocene volcanic rocks in the Carter Mountain area, Park County, southeastern Absaroka Range, Wyoming: University of Wyoming Contributions to Geology, v. 21, p. 153194.
Gazin, C.L., 1976, Mammalian faunal zones of the Bridger Middle Eocene: Smithsonian Contributions to Paleontology, v. no. 26, p. 125.
Gingerich, P.D., 1979, Paleontology, phylogeny and classification: an example from the mammalian fossil record: Systematic Zoology, v. 28, p. 451464, doi: 10.2307/sysbio/28.4.451.
Gould, S.J., 1975, On the scaling of tooth size in mammals: American Zoologist, v. 15, p. 351362, doi: 10.1093/icb/15.2.353.
Gould, S.J., and Garwood, R.A., 1969, Levels of integration in mammalian dentitions: an analysis of correlations in Nesophontes micrus (Insectivora) and Oryzomys couesi (Rodentia): Evolution, v. 23, p. 276300.
Gunnell, G.F., 1998, Mammalian fauna from the lower Bridger Formation (Bridger A, early Middle Eocene) of the southern Green River Basin, Wyoming: Contributions from the Museum of Paleontology, University of Michigan, v. 30, p. 83130.
Gunnell, G.F., and Bartels, W.S., 1994, Early Bridgerian (middle Eocene) vertebrate paleontology and paleoecology of the southern Green River Basin, Wyoming: University of Wyoming Contributions to Geology, v. 30, p. 5770.
Gunnell, G.F., Murphey, P.C., Stucky, R.K., Townsend, K.E.B., Robinson, P., Zonneveld, J.-P., and Bartels, W., 2009, Biostratigraphy and biochronology of the latest Wasatchian, Bridgerian, and Uintan North American Land Mammals “Ages”, in Papers on Geology, Vertebrate Paleontology, and Biostratigraphy in Honor of Michael O. Woodburne: Flagstaff, Arizona, Museum of Northern Arizona Bulletin 65, p. 279330.
Hunter, J.P., and Jernvall, J., 1995, The hypocone as a key innovation in mammalian evolution: Proceedings of the National Academy of Sciences, v. 92, p. 1071810722.
Kolbe, S.E., Lockwood, R., and Hunt, G., 2011, Does morphological variation buffer against extinction? A test using veneroid bivalves from the Plio-Pleistocene of Florida: Paleobiology, v. 37, p. 355368, doi: 10.1666/09073.1.
Koyabu, D.B., Oshida, T., Dang, N.X., Can, D.N., Kimura, J., Sasaki, M., Motokawa, M., Son, N.T., Hayashida, A., Shintaku, Y., and Endo, H., 2009, Craniodental mechanics and the feeding ecology of two sympatric callosciurine squirrels in Vietnam: Journal of Zoology, v. 279, p. 372380, doi: 10.1111/j.1469-7998.2009.00629.x.
Lazzari, V., Charles, C., Tafforeau, P., Vianey-Liaud, M., and Aguilar, J.-P., 2008, Mosaic convergence of rodent dentitions: PLoS ONE, v. 3, e3607, doi: 10.1371/journal.pone.0003607.
Lazzari, V., Aguilar, J.-P., and Michaux, J., 2010, Intraspecific variation and micro-macroevolution connection: illustration with the late Miocene genus Progonomys (Rodentia, Muridae): Paleobiology, v. 36, p. 641657, doi: 10.1666/09046.1.
Linnaeus, C., 1758, Systema naturae per regna tria naturae, secundum classes, ordines, genera, species cum characteribus, differentiis, synonymis, locis.
Mcgrew, P.O., Berman, J.E., Hecht, M.K., Hummel, J.M., Simpson, G.G., and Wood, A.E., 1959, The geology and paleontology of the Elk Mountain and Tabernacle Butte area, Wyoming: Bulletin American Museum of Natural History, v. 117, p. 117176.
Mcgrew, P.O., and Sullivan, R., 1970, The stratigraphy and paleontology of Bridger A: University of Wyoming Contributions to Geology, v. 9, p. 6685.
Miller, G.S., and Gidley, J.W., 1918, Synopsis of the supergeneric groups of rodents: Journal of the Washington Academy of Sciences 8, p. 431448.
Murphey, P.C., and Evanoff, E., 2007, Stratigraphy, fossil distribution and depositional environments of the upper Bridger Formation (middle Eocene), southwestern Wyoming: Wyoming State Geological Survey Report of Investigation, no. 57, p. 196.
Norconk, M.A., Grafton, B.W., and Conklin-Brittain, N.L., 1998, Seed dispersal by neotropical seed predators: American Journal of Primatology, v. 45, p. 103126.
Ostrander, G.E., 1986, A new species of the early Tertiary rodent Thisbemys: Transactions of the Kansas Academy of Science, v. 89, p. 4548.
Pfennig, D.W., and Pfennig, K.S., 2012, Evolution’s Wedge: Competition and the Origins of Diversity: Berkeley, University of California Press, 303 p.
Renaud, S., Benammi, M., and Jaeger, J.-P., 1999, Morphological evolution of the murine rodent Paraethomys in response to climatic variations (Mio-Pleistocene of North Africa): Paleobiology, v. 25, p. 369382, doi: 10.1666/0094-8373-25.3.369.
Renaud, S., Michaux, J., Schmidt, D.N., Aguilar, J.-P., Mein, P., and Auffray, J.-C., 2005, Morphological evolution, ecological diversification and climate change in rodents: Proceedings of the Royal Society of London B: Biological Sciences, v. 272, p. 609617, doi: 10.1098/rspb.2004.2992.
Reumer, J.W.F., 1995, The effect of paleoclimate on the evolution of the Soricidae (Mammalia, Insectivora), in Vrba, E., Denton, G., Partridge, T., and Burckle, L., eds., Paleoclimate and Evolution with Emphasis on Human Origins: New Haven, Yale University Press, p. 135137.
Rose, K., and Koenigswald, W.V., 2007, The marmot-sized paramyid rodent Notoparamys costilloi from the Early Eocene of Wyoming, with comments on dental variation and occlusion in paramyids: Bulletin of Carnegie Museum of Natural History, no. 39, p. 111125.
Rosenberger, A.L., and Kinzey, W.G., 1976, Functional patterns of molar occlusion in platyrrhine primates: American Journal of Physical Anthropology, v. 45, p. 281298.
West, R.M., and Atkins, E.G., 1970, Additional middle Eocene (Bridgerian) mammals from Tabernacle Butte, Sublette County, Wyoming: American Museum of Novitates, no. 2404, p. 126.
West, R.M., and Hutchison, J.H., 1981, Paleontology and geology of the Bridger Formation, southern Green River Basin, southwestern Wyoming. part 6, The fauna and correlation of Bridger E: Contributions in Biology and Geology, Milwaukee Public Museum, no. 46, p. 18.
Wood, A.E., and Wilson, R.W., 1936, A suggested nomenclature for the cusps of the cheek teeth of rodents: Journal of Paleontology, v. 10, p. 388391.
Wood, A.E., 1962, The Early Tertiary rodents of the family Paramyidae: Transactions of the American Philosophical Society, v. 52, p. 1261.
Woodburne, M.O., Gunnell, G.F., and Stucky, R.K., 2009a, Climate directly influences Eocene mammal faunal dynamics in North America: Proceedings of the National Academy of Sciences, v. 106, p. 1339913403, doi: 10.1073/pnas.0906802106.
Woodburne, M.O., Gunnell, G.F., and Stucky, R.K., 2009b, Land mammal faunas of North America: Rise and fall during the Early Eocene Climatic Optimum: Denver Museum of Nature and Science Annals, no. 1, p. 180.

Metrics

Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed