Joaquín Arroyo-Cabrales

Color origin and heat evidence of paleontological bones: Case study of blue and gray bones from San Josecito Cave, Mexico

Abstracts Results of the investigation of paleontological blue and gray bone fragments of small vertebrates coming from stratigraphic layer 770 at San Josecito Cave (Nuevo Leon, Mexico, dating between 28 000 and 19 000 years BP), are presented. Structural and elemental analyses combining X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and particle-induced X-ray and γ-ray emission (micro-PIXE/PIGE), as well as spectroscopic investigations [i.e., UV/visible/near-IR reflectance spectroscopy and X-ray absorption near-edge structure (XANES) spectroscopy] were performed to identify precisely the origin of the blue stain. Prior research has shown that Mn5+ in tetrahedral coordination could be responsible for the turquoise blue color in mastodon ivory some tens of million years old that was modified by a heat process. Manganese is present in the anionic form of (MnO4)3- and partially substitute for (PO4)3- in the hydroxyapatite matrix. The spectroscopic data of the present study have revealed a heat-induced modification, revealed traces of Mn among the typical bone constituents (Ca, P, Sr, Zn), and provided insights into the color origin of the blue paleontological bones from San Josecito Cave. Cations of Mn5+ in a tetrahedral environment of four O2- ions in the apatite structure are found in these bones, the same color origin as in the blue mastodon ivory. As indicated by XANES, Mn4+ ions in octahedral coordination as in pyrolusite are found in gray bones. The presence of submicroscopic Mn oxide inclusions might explain the color of the San Josecito gray bones. The formation of Mn5+ very likely is induced by heat treatment of the bones under oxidizing conditions. The heat-induced modification of both types of paleontological bones also is indicated by the direct observation of apatite crystals using TEM. The question remains, however, how the heat originated inside the cave.

Diet and habitat definitions for Mexican glyptodonts from Cedral (San Luis Potosí, México) based on stable isotope analysis

Values for δ 13 C and δ 18 O obtained from molar samples from three individuals pertaining to Glyptotherium sp. from Cedral (San Luis Potosi, Mexico) are provided and are utilized to infer general aspects of glyptodont diet and habitat. On average this animal showed a C 3 /C 4 mixed diet, with a high consumption of C 4 plants. Comparisons of the δ 13 C VPDB and δ 18 O VPDB values for glyptodonts with horses, mastodons, mammoths and tapirs from the same locality show that glyptodonts from Cedral lived in an open habitat.

Pleistocene Lizards (Reptilia: Squamata) from San Josecito Cave, Nuevo León, México@@@Pleistocene Lizards (Reptilia: Squamata) from San Josecito Cave, Nuevo Leon, Mexico

San Josecito Cave is located on a steep western flank of the Sierra Madre Oriental, Nuevo Le6n, Mexico, at 2250 m elevation. A total of 1115 skeletal remains of lizards are known from the deposit; only two specimens were from previous excavations. In greater than 100,000 vertebrate remains, only four species of lizards have been recovered: one anguid (Barisia cf. B. imbricata, n = 1088 fossils) and three phrynosomatids (Phrynosoma josecitensis, n = 1; P orbiculare, n = 1; P cf. P orbiculare, n = 12; and Sceloporus sp., n = 13). The cave has produced the type and only known specimen of the extinct species Phrynosoma josecitensis, described from an earlier excavation. The presence of, or the validity of, this extinct species cannot be verified on the basis of remains recovered from the current excavation, and the taxon may be a variant of the locally living P orbiculare. The first fossil record of Barisia imbricata is presented.

Diet and Habitat for Six American Pleistocene Proboscidean Species Using Carbon and Oxygen Stable Isotopes

Abstract. Diet and habitat were estimated, based on stable isotopes, for six species of proboscideans inhabiting the Americas during the Pleistocene. In North America, Mammuthus columbi (Elephantidae) was a mixed C3/C4 herbivore inhabiting open areas, while Mammut americanum (Mammutidae) fed exclusively on C3 plants and preferred closed areas. In contrast, members of the family Gomphotheriidae showed a wide range of food preference and habitats. This is the case of Cuvieronius tropicus, a mixed-diet herbivore living in open areas. In South America, another gomphothere — Cuvieronius hyodon — inhabited open areas and had a C3-plant diet similar to others from some Southern plains such as Stegomastodon platensis. On the other hand, S. waringi from tropical South America lived in open areas and had a C3/C4 mixed diet. The fact that gomphotheres had more flexible diet habits could explain why those animals were able to cross the Panamanian Isthmus, while mammoths and mastodons did not.

Quaternary Mammals, People, and Climate Change: A View from Southern North America

The Pleistocene and modern mammal faunas of southern North America strongly differ in taxonomic makeup, distribution, and physiognomy. The former faunal complexes are part of the ancient landscape in which early peoples may have interacted. Customarily, differences between the Pleistocene and modern faunas have been attributed to climate change or human-impact driven extinctions. Mexico’s Pleistocene mammal record is analyzed in time and space, emphasizing the study of the Rancholabrean Chronofauna, which is the most recent North American Land Mammal Age fauna. Palynological and paleosol records are reviewed as an independent check of the interpretation derived from mammals. The integration of the information provides the basis for a proposal regarding Late Pleistocene climate change trends across the country, and whether people were involved in the mammalian community response to climate change in terms of extinction or biogeographic shifting within and outside the country. This approach supports an explanation of the differences between southern North America’s Pleistocene and modern mammal faunas.

Rediscovery of the Mexican flat-headed bat Myotis planiceps (Vespertilionidae)

The insectivorous flat-headed bat Myotis planiceps (Vespertilionidae) is an endemic species apparently restricted to a very small area, known only from three specimens collected between 1952 and 1970 in Madrean pine-oak woodland in three adjacent states in north-central Mexico: Coahuila, Nuevo Leon, and Zacatecas (Matson, 1975). Myotis planiceps was once considered extinct by IUCN (Baillie and Groombridge, 1996), but more recently its status was changed to Critically Endangered (IUCN, 2004). The first objective of our study was to determine if we could find a living population or populations of this species. If extant populations were discovered, then further investigations were warranted, including detailed distribution, habitat requirements, dietary habits, and roosting behavior, to define the species’ current conservation status in accordance with standards proposed by IUCN (2004).

Diet and habitat of mesomammals and megamammals from Cedral, San Luis Potosí, México

Using carbon and oxygen isotopic relationships from dental enamel, diet and habitat were inferred for both mesomammals and megamammals that lived in Cedral (San Luis Potosi, north-central Mexico) during Late Pleistocene time. δ 13 C and δ 18 O values show that bison, some horses and mammoth were eating C 4 plants and lived in open areas, while tapir, camel and some llamas ate C 3 plants and inhabited closed areas. All other studied herbivores (pronghorn, glyptodont, mylodont ground sloth, javelina, mastodon, and other llamas, horses and mammoth) had a C 3 /C 4 mixed diet, living in areas with some percentage of tree coverage. On the other hand, American lion and dire wolf ate either C 4 or mixed-diet herbivores, and short-faced bear ate C 3 herbivores. At Cedral, more humid conditions existed than presently, allowing the presence of a forested area near the grassland.

Preliminary data on the diet and habitat preferences of Capromeryx mexicana (Mammalia: Antilocapridae) from the late Pleistocene of Cedral, San Luis Potosí, Mexico

Abstract We inferred the diet and habitat preferences of three individuals of the dwarf pronghorn Capromeryx mexicana from Cedral, Mexico, using stable isotope analysis and the mesowear method. Both approaches showed that the individuals were C3/C4 mixed feeders which inhabited open forest. These results differ from previous hypotheses that suggested this species only fed on grasses and lived in grasslands.

Placement of the rediscovered Myotis planiceps (Chiroptera: Vespertilionidae) within the Myotis phylogeny

Myotis planiceps (flat-headed myotis) was known from only 3 specimens collected from 3 different sites in the states of Coahuila, Nuevo Leon, and Zacatecas, Mexico, since its discovery in 1952. The last specimen was collected in 1970; in 1996, after efforts to recollect samples failed, the species was listed as extinct. However, an expedition in 2004 rediscovered a population of M. planiceps and the species was relisted as endangered. Members of this species have a conspicuously flattened cranium, speculated to be an adaptation for living in crevices; however, little is known about its biology and, to date, little work has been done to clarify its phylogenetic relationships with other members of the genus Myotis. In order to elucidate the placement of M. planiceps within the Myotis phylogeny, we sequenced 1,140 base pairs (bps) of the mitochondrial cytochrome-b gene (Cytb) and 1,148 bps of the nuclear Recombination Activating Gene 2 (rag2) from 7 samples collected from 4 different localities in north-central Mexico. We found 4 different haplotypes for Cytb that differed by 0.14% mean sequence divergence and 13 alleles for rag2 within samples of M. planiceps. We performed maximum parsimony, maximum likelihood, and Bayesian analyses to compare these samples with Myotis sequences available on GenBank. All reconstructions placed M. planiceps within a strongly supported clade including several Nearctic Myotis (M. volans, M. sodalis, M. lucifugus, M. thysanodes, and M. evotis). M. planiceps forms a paraphyletic relationship with M. volans, despite significant differences in skull morphology between the 2 species. Myotis planiceps (Myotis de cabeza plana) era conocido a partir de sólo 3 especímenes recolectados en 3 sitios diferentes en los estados de Coahuila, Nuevo León y Zacatecas, México, desde su descubrimiento en 1952. El último ejemplar se colectó en 1970 y la especie fue declarada extinta en 1996, después de que fallaron los esfuerzos para recolectar más muestras. Sin embargo, durante una expedición en 2004 se redescubrió una población de M. planiceps y la especie fue recategorizada bajo Peligro de Extinción. Los miembros de esta especie tienen un cráneo visiblemente aplanado, rasgo que se especula sería una adaptación para vivir en las grietas; sin embargo, se sabe poco sobre su biología y, hasta la fecha, poco se ha hecho para aclarar sus relaciones filogenéticas con otros miembros del género Myotis. Con el fin de dilucidar la posición de M. planiceps dentro de la filogenia de Myotis, secuenciamos 1140 pb del gen mitocondrial citocromo-b (Cytb) y 1148 pb del gen nuclear Activador de la Recombinación 2 (rag2) a partir de 7 muestras recolectadas de 4 localidades diferentes en la región nortecentral de México. Encontramos 4 haplotípos diferentes para Cytb que presentaron un promedio de divergencia de secuencia de 0.14%, y 13 alelos del gen rag2 en muestras de M. planiceps. Realizamos análisis de máxima parsimonia, máxima verosimilitud y Bayesiano para comparar estas muestras con otras secuencias de Myotis disponibles en GenBank. Todas las reconstrucciones ubican a M. planiceps dentro de un clado bien soportado que incluye también a varios Myotis del Neártico (M. volans, M. sodalis, M. lucifugus, M. thysanodes, y M. evotis). M. planiceps forma una relación parafilética con M. volans, a pesar de diferencias significativas en la morfología del cráneo entre estas especies.

Diet of rinchothere (Proboscidea, Gomphotheriidae, Rhynchotherium Species) of Taxco, Guerrero, México

Abstract The diet of a gomphothere (Proboscidea, Gomphotheriidae, Rhynchotherium species) from the Mexican Pliocene was determined using carbon and oxygen stable isotopes relationships in dental enamel. The analyses demonstrated that this individual exclusively fed on C3 plants, similar to some specimens found in Florida, United States.