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Vol. 23, 2006
Pleistocene Microvertebrates from Santa Cruz Nuevo, Puebla, México
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Rosa E. Tovar and Marisol Montellano
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The Pleistocene was characterized by drastic climatic changes that influenced patterns of evolution and geographical distribution of the biota. At the end of this period occurred an important event, the extinction of megafauna; however, few genera of microvertebrates have been reported as extinct. Holman (1995) notes that no family or genus of herpetofauna became extinct and that only 12 of 129 taxa are in doubt. In Mexico, 776 Pleistocene-age localities bear mammal remains in which 286 species and 146 genera are identified; 30 percent of the species are not present today in Mexico (Arroyo-Cabrales et al. 2002). There are 29 registered localities with 98 genera and 118 species of birds, of which 17 species are reported as extinct (Corona 2002). Present in 27 localities are remains of herpetofauna, including 10 genera and 19 species of amphibians with no extinct species, and 27 genera and 39 species of reptiles with 4 extinct species. It is clear that the avian and herpetofauna fossil record in Mexico is poor. In the southeastern part of the state of Puebla, near the village of Santa Cruz Nuevo, a sequence of ca. 38 m of fluvial late-Cenozoic sands, silts, and gravels outcrops. During the last four years sediment from different sites was collected for screen washing, and Pleistocene remains of anurans, reptiles, birds and micromammals were recovered. The objective of the study was to evaluate change in the microfaunal assemblage from the late Pleistocene to the present. Until now, 22 families, 24 genera, and 11 species of vertebrates identified include Ambystoma sp., Bufo occidentalis, Bufo cf. valliceps, Bufo sp., Rana sp., Kinosternon sp., Rhinoclemys sp., Gopherus cf. berlandieri, Sceloporus cf. grammicus, Sceloporus cf. horridus, Conopsis sp., Lampropeltis sp., Leptodeira sp., Senticolis sp., Thamnophis sp., Trimorphodon sp., Crotalus sp., remains of plethodontids, spade-foot frogs, skinks, Neotoma mexicana, Peromyscus difficilis, Reithrodontomys sp., Sylvilagus floridanus, Sylvilagus sp., and Bassariscus cf. sumichrasti. Megafauna identified includes Odocoileus sp., Pampatherium mexicanum, Glyptotherium sp., Equus conversidens, Mammuthus sp., and unidentified genera of deer, bear, goat, and mastodont. The presence of Peromyscus difficilis, Neotoma mexicana, and Pampatherium mexicanum confirms a late-Pleistocene age for the deposit. Excellently preserved fossil remains suggest the identified taxa probably lived near the deposit area. Of the family-level taxa identified, 50 percent are present today in the study area (Bufonidae, Scaphiopodidae, Ranidae, Phrynosomatidae, Colubridae, Viperidae, Kinosternidae, Leporidae, Muridae, Procyonidae, and Cervidae); Rosa E. Tovar and Marisol Montellano, Depto. Paleontología, Instituto de Geología, Universidad Nacional Autónoma de México. Cd Universitaria, Deleg. Coyoacán, 04510 D.F. México; e-mails:
[email protected];
[email protected]
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18 percent are reported extinct in North America (Pampatheriidae, Glyptodontidae, Equidae and Elephantidae); and 32 percent have experienced a change in their geographic distribution (Ambystomatidae, Plethodontidae, Bataguridae, Testudinidae, Scincidae, Antilocapridae, and Ursidae). As expected, most of the megafauna taxa became extinct, and some of them (Antilocapridae and Ursidae) today are distributed differently. The presence of the gopher turtle Gopherus is noteworthy because it represents the southernmost record of the genus in North America. At present, four species range from southern Nevada in the United States to southeastern San Luis Potosí in Mexico. Recently Gopherus was reported in the state of Hidalgo (Nájera-Hernández and Castillo-Cerón 2004a, 2004b), filling the gap between northern Mexico and Puebla. This faunal association is a mixture of taxa with different ecological requirements. Although most of the fossil taxa inhabit a semiarid environment (Bufo occidentalis, Sceloporus cf. horridus, Gopherus cf. berlandieri, Peromyscus difficilis, and the family Scaphiopodidae), they are found together with taxa usually associated with more humid (tropical and subtropical) conditions, such as the frog B. valliceps and the turtle Rhinoclemmys (Ernst and Barbour 1989; Porter 1970). Giant armadillos (Pampatherium and Glyptotherium) are considered tropical or semitropical organisms (Gillete and Ray 1981). Salamanders of the genus Ambystoma live in rivers or lakes in temperate subtropical areas; on the other hand, salamanders of the family Plethodontidae are partially or completely arboreal species that inhabit cloud forest or wet montane forest (Wake and Lynch 1976). Bears inhabit the oak forest. The presence of different species with disparate ecological requirements suggests the existence of a disharmonious or ecologically incompatible association, as proposed by Fay (1988) and Graham and Lundelius (1984). Bufo occidentalis, Sceloporus cf. horridus, Sceloporus cf. grammicus, and the genera Rhinoclemmys and Senticolis are here reported for the first time in North America. The genera Conopsis and Leptodeira and the families Plethodontidae and Scincidae are new fossil records for Mexico. References Cited Arroyo-Cabrales, J., O. Polaco, and E. Johnson 2002 La Mastofauna del Cuaternario Tardío en México. In Avances en los Estudios Paleomastozoológicos, edited by M. Montellano and J. ArroyoCabrales, pp. 103–23. Instituto Nacional de Antropología e Historia, México. Corona, E. 2002 issue):293–306.
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The Pleistocene Bird Record of México. Acta Zoológica Cracoviensia 45 (special
Ernst, C. H., and R. W. Barbour ton, D.C.
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Turtles of the World. Smithsonian Institution Press, Washing-
Fay, L. P. 1988 Late Wisconsinan Appalachian Herpetofaunas: Relative Stability in the Midst of Change. Annals of Carnegie Museum 57(9):189–220. Gillete D. D., and C. E. Ray 1981 Glyptodonts of North America. Smithsonian Contributions to Paleobiology, Vol. 40. Smithsonian Institution Press, Washington, D.C. Graham R. W., and E. L. Lundelius, Jr. 1984 Coevolutionary Disequilibrium and Pleistocene Extinctions. In Quaternary Extinctions, edited by P. Martin and R. G. Klein, pp. 223–49. The University of Arizona Press, Tucson. 80
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Pleistocene Amphibians and Reptiles in North America. Oxford University Press,
Nájera-Hernández, L., and J. Castillo-Cerón 2004a Fósiles de Testudínidos del Estado de Hidalgo. IX Congreso Nacional de Paleontología, Book of Abstracts:81. Tuxtla Gutiérrez, Chiapas, México. ——— 2004b Gopherus en el Pleistoceno del Estado de Hidalgo. VIII Reunión Nacional de Herpetología, Book of Abstracts:151. Villahermosa, Tabasco, México. Porter, K. R. 1970 Bufo valliceps. Catalogue of American Amphibians and Reptiles 94:1–4. Society for the Study of Amphibians and Reptiles. Wake, D. B., and J. F. Lynch 1976 The Distribution, Ecology and Evolutionary History of Plethodontid Salamanders in Tropical America. Natural History Museum of Los Angeles County. Science Bulletin 25:1–65.
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