11th North American Paleontological Conference Program with Abstracts (2025)

The alluvial sequence of Santa Cruz Nuevo, Mexico: Paleoecological interpretation of fossil vertebrates and pedosediments from marine isotope stage 3

The Pleistocene was climatically variable worldwide. In Mexico, climatic changes have been primarily studied in central and northern regions of the country, particularly in regard to marine isotope stage 2 (MIS 2). The paleoenvironments of the previous interglacial, MIS 3, remain less known, especially in the south. In the present work, the results for an alluvial pedosequence in Santa Cruz Nuevo, Puebla are presented; the large and small vertebrates recovered from this locality were used to reconstruct past paleoenvironments. However, it was found that the suite of fossil microvertebrates used here was more informative than that of the macrofossils because they are still extant, thus allowing insights into their ecology. Radiocarbon dating of the pedosequence indicates it was formed during MIS 3, around 30,000 radiocarbon years before present. Four pedological units were recognized: stagnogleyic, carbonate, gley and humus. With the exception of the carbonate unit, fossils were retrieved from all pedological units. Paleosols varied between Fluvisols and Gleysols, neither of which is diagnostic of any particular climate. Nevertheless, they are both hydromorphic, a condition that could result from intermittent flooding. At the base of the section, in the stagnogleyic unit, the presence of mammoth bones in conjunction with negative values of δ 13 C (-23.3 ‰) in paleosols suggest the existence of grassland with a dominance of C3 grasses. The isotopic values are similar in the succeeding units (-23 to-22 ‰); however, the fossil association found in Santa Cruz Nuevo indicates the incorporation of shrubland faunas. It can thus be inferred that the plant composition in Santa Cruz Nuevo comprised C3 grasses and CAM metabolic succulents such as cacti and magueys. Hydrated CAM plants use the ribulose 1,5-biphosphate (RBP) carboxilase enzyme, which produces negative values comparable to those of C3 plants. The uppermost unit, the humus, has a similar fossil association, but in spite of this, the paleosol-based isotopic values suggest a vegetation mix, indicated by the presence of C4 plants such as grasses. The comparison of our results with other records suggests that the end of MIS 3 was a dry phase which changed to humid, and in some places cool conditions, during MIS 2. No MIS 2 record is preserved in the Santa Cruz Nuevo pedosequence. The comparison of the modern soil and climate with our pedosequence shows more humid conditions during MIS 3. Finally, and although the microvertebrate associations are similar to extant ones, the macrovertebrates also encompass extinct taxa. RESUMEN El Pleistoceno fue un periodo de variados cambios climáticos. En México, los cambios climáticos han sido más estudiados en las porciones centro y norte del país, particularmente los de la etapa isotópica marina 2. Los paleoambientes del periodo glacial previo, la etapa isotópica marina 3, son menos conocidos, especialmente en la porción sur. En este trabajo presentamos los resultados para una pedosecuencia aluvial en Santa Cruz Nuevo, Puebla, donde se han encontrado fósiles de vertebrados, con una gran proporción de microvertebrados asociados a paleosuelos. Los fósiles fueron usados para reconstruir los paleoambientes, sin embargo, los microvertebrados fósiles fueron más útiles debido a que continúan presentes en el área y a través de sus análogos actuales podemos reconocer sus requerimientos ecológicos. La datación por radiocarbono de la pedosecuencia indica que se formó durante la etapa isotópica marina 3, alrededor de los 30,000 años de radiocarbono antes del Presente. Se reconocieron cuatro unidades pedológicas: estagnogleica, carbonatada, gleyca y húmica. En todas se encontraron fósiles con excepción de la unidad carbonatada. Los paleosuelos varían entre Fluvisoles y Gleysoles, los cuales no son diagnósticos para un clima en particular. Sin embargo, son indicativos de hidromorfismo que pudo ser resultado de inundaciones temporales. Se usaron datos de δ 13 C de paleosuelos y las asociaciones de microvertebrados como los registros más importantes para las reconstrucciones paleoambientales. En la base, en la unidad estagnogleyca, la presencia de huesos de mamut y los valores negativos de

Fossil freshwater gastropods from northern Mexico – A case of a “silent” local extirpation, with the description of a new species

Boletín de la Sociedad Geológica Mexicana,

Pleistocene Microvertebrates from Santa Cruz Nuevo, Puebla, México

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) 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.

Late Tertiary terrestrial mammals from Central Mexico and their relationship to South American immigrants

Revista Brasileira De Paleontologia, 2004

Nos últimos 25 anos ocorreram inúmeras descobertas de mamíferos neoterciários na região central do México, sendo que muitas vêm das bacias localizadas na Faixa Vulcânica Transmexicana. Em contraste com a maioria dos registros anteriores, estes achados têm sido cuidadosamente inseridos num contexto estratigráfico. Datações radiométricas em camadas de cinzas vulcânicas, juntamente com estudos paleomagnéticos, permitem o posicionamento do limite das Idades Mamíferos Terrestres da Ámerica do Norte Hemphillian -Blancan em 4,8 Ma. As pesquisas sobre os mamíferos neoterciários da região central do México também têm fornecido valiosas informações sobre novos táxons, ampliação da distribuição geográfica de muitos animais e mudanças ambientais na região. Vários mamíferos que imigraram da Ámerica do Sul durante o Neoterciário são também agora conhecidos na região central do México, adicionando novas e importantes informações concernentes à formação da ponte terrestre do Panamá e do Grande Intercâmbio Biótico Americano. Táxons como as preguiças Megalonyx e Glossotherium, os Cingulata Glyptotherium e Plaina e o roedor Neochoerus proveram dados relevantes a este evento. É geralmente aceito que a ponte terrestre do Panamá formou-se entre 2,5 e 3 milhões de anos atrás. Entretanto, as idades radiométricas e paleomagnéticas obtidas na região central do México associadas às informações aportadas pelos mamíferos imigrantes sul-americanos, indicam que esta ponte terrestre poderia ter-se originado mais de um milhão de anos antes. Por outro lado, o movimento tectônico, as mudanças de caráter insular e o vulcanismo na América Central durante o Neoterciário, com conseqüências eustáticas e na composição vegetal, tornam muito difícil a determinação cronológica precisa tanto da formação da ponte terrestre quanto do intercâmbio biótico resultante. Palavras-chave: Hemphillian, Blancan, Faixa Vulcânica Transmexicana, Grande Intercâmbio Biótico Americano.

Integrating Paleobiology, Archeology, and History to Inform Biological Conservation

The search for novel approaches to establishing ecological baselines (reference conditions) is constrained by the fact that most ecological studies span the past few decades, at most, and investigate ecosystems that have been substantially altered by human activities for decades, centuries, or more. Paleobiology, archeology, and history provide historical ecological context for biological conservation, remediation, and restoration. We argue that linking historical ecology explicitly with conservation can help unify related disciplines of conservation paleobiology, conservation archeobiology, and environmental history. Differences in the spatial and temporal resolution and extent (scale) of prehistoric, historic, and modern ecological data remain obstacles to integrating historical ecology and conservation biology, but the prolonged temporal extents of historical ecological data can help establish more complete baselines for restoration, document a historical range of ecological variability, and assist in determining desired future conditions. We used the eastern oyster ( Crassostrea virginica) fishery of the Chesapeake Bay (U.S.A.) to demonstrate the utility of historical ecological data for elucidating oyster conservation and the need for an approach to conservation that transcends disciplinary boundaries. Historical ecological studies from the Chesapeake have documented dramatic declines (as much as 99%) in oyster abundance since the early to mid-1800s, changes in oyster size in response to different nutrient levels from the sixteenth to nineteenth centuries, and substantial reductions in oyster accretion rates (from 10 mm/year to effectively 0 mm/year) from the Late Holocene to modern times. Better integration of different historical ecological data sets and increased collaboration between paleobiologists, geologists, archeologists, environmental historians, and ecologists to create standardized research designs and methodologies will help unify prehistoric, historic, and modern time perspectives on biological conservation. a la determinación de condiciones futuras deseadas. Utilizamos la pesquería del ostión oriental ( Crassostrea virginica) de la Bahía de Chesapeake (E.U.A.) para demostrar la utilidad de los datos ecológicos históricos para dilucidar la conservación del ostión y la necesidad de un método de conservación que trascienda límites disciplinares. Los estudios ecológicos históricos de Chesapeake han documentado declinaciones dramáticas (tanto como 99%) en la abundancia de ostiones de inicios a mediados de los 1800, cambios en el tamaño de ostiones en respuesta a diferentes niveles de nutrientes del siglo dieciséis al diecinueve y reducciones sustanciales en las tasas de acreción de ostiones (de 10 mm/año a 0 mm/año) desde el Holoceno Tardío a tiempos modernos. Una mejor integración de diferentes conjuntos de datos ecológicos históricos y una mayor colaboración entre paleobiólogos, geólogos, arqueólogos, historiadores ambientales y ecólogos para definir diseños de investigación estandarizados y metodologías ayudarán a unificar perspectivas de la biología de la conservación prehistóricas, históricas y modernas.

Geographical heterochrony: Comtemporaneous coexistence of neogene and recent molluscan faunas in the Americas

Palaeogeography Palaeoclimatology Palaeoecology - PALAEOGEOGR PALAEOCLIMATOL, 1982

Geographical heterochrony is a biogeographical pattern that, within a single faunal province, represents the contemporaneous coexistence of newly-evolved faunas and those which have persisted, unchanged, from earlier geological ages. This array of discrete, adjacent, and asynchronous faunules produces a mosaic pattern in both time and space. Based on the faunas of three anachronistic subregions within the Recent Caribbean Molluscan Province, one off the Yucatan Peninsula, one off Roatan Island, and one near the Gulf of Venezuela, this geographically heterochronous province is shown to contain two types of relict pockets. The term "primary relict pocket" is proposed for a faunule that contains the same genera and species as the older~ more extensive parent fauna, and differs only in being reduced spatially. The term "secondary relict pocket" is proposed for a faunule that contains relict genera that were once widespread but have persisted and speciated within the boundaries of the pocket. Based on the faunas of the Caribbean relict pockets, on patterns seen in the fossil record, and on the unusual ecological conditions of the Gulf of Venezuela area, a new reconstruction of Neogene Caribbean molluscan provinciality is proposed and two new Neogene molluscan provinces, the Caloosahatchian and the Gatunian, are described. To explain the existence of the Caribbean relict pockets and their affinities to the Recent Panamic and Neogene Floridian faunas, a new interpretation of Upper Pliocene biological catastrophism and extinction is proposed, incorporating aspects of the effects of the closing of the Isthmus of Panama and glacially-induced sea level fluctuations and temperature changes. A new scheme of Recent tropical American marine molluscan provinciality is presented, taking into account the two paleoprovinces and the distribution of the post-Pleistocene Caribbean fauna.

Freshwater mollusks of the Valley of Sobaco, Coahuila, Northeastern Mexico – a subfossil ecosystem similar to Cuatrociénegas

Boletin De La Sociedad Geologica Mexicana, 2014

In the Valley of Sobaco located in Coahuila, Mexico, were found the remains of an aquatic ecosystem with a Holocene malacofauna showing similarities to modern aquatic communities of the internationally famous site of Cuatrociénegas, located in the state of Coahuila and known as the "Mexican Galapagos", as it hosts a large number of endemic species. In addition of ostracods, algae, foraminifera, diatoms and remains of vascular plants, the Sobaco paleo-pools (pozas) also contain the gastropods Juturnia coahuilae, Pyrgulopsis manantiali, Coahuilix hubbsi, Coahuilix cf. landyei and Assiminea cienegensis, which are endemic species of Cuatrociénegas Valley. Additional discoveries include sub-recent lacustrine microbial tufas (microbialites, stromatolites), as well a pool that still contains water hosting bacterial communities similar to those from Cuatrociénegas.

MEGAHERBIVORE FOSSIL RECORD FROM THE NEOGENE OF JALISCO, MEXICO, AND ITS IMPLICATIONS FOR PALEOENVIRONMENTAL INTERPRETATION

New Mexico Museum of Natural History and Science Bulletin, 2022

INTRODUCTION Mammals that feed on plants and that typically reach an adult body mass greater than 1000 kilograms (Owen-Smith, 1998) or even 800 kg (Van Valkenburgh et al., 2016) are usually called megaherbivores. This kind of terrestrial mammal strictly complies with the concepts of Functional Megafauna and Apex Megafauna proposed by Moleón et al. (2020). They are very important in continental ecosystems as they are capable of producing significant alterations to those ecosystems (Keesing, 2000; Wilkie et al., 2011) widely influencing plant community composition, vegetation structure and openness, seed dispersal, nutrient cycling rates and patterns, and fire regimes (Gill, 2014; Brocherens, 2018). For all this, megaherbivores are considered key species in ecosystems, and their presence in the fossil record allows us to make inferences about the characteristics of the paleoenvironment of the places and time intervals in which they lived (see Gill, 2014). In America it becomes even more important to know their presence, distribution and impact because, despite the fact that this was one of the continents with a great richness of species of this type in the past (Van Valkenburgh et al., 2016), the extinction at the end of the Pleistocene eliminated most of them, with only the herbivores of medium or small size surviving, for the most part (Lambert and Holling, 1998). Even recognizing the importance of this type of animal in ecosystems, their role in the past is not yet clear (Calandra et al., 2008). This type of vertebrate is common in the fossil record of the Quaternary in Mexico, but there are few known localities in the country from earlier time intervals, such as the Neogene. Faunal assemblages are known from the Late Miocene and Pliocene (Late Hemphillian and Blancan) North American Land-Mammal "Ages" (NALMA) in the states of

Westgate Casa Blanca paleoecology 2012

Recent analysis of primate remains in the Casa Blanca local fauna from the late middle Eocene Laredo Formation at Laredo, Texas has shown that the fauna's primate species diversity was greater than previously reported. Recognition of Mahgarita cf. M. stevensi provided the first record of an Old World cercomoniine species in a Uintan community in North America. The presence of three omomyids indicates that primate species diversity in the paralic Casa Blanca community was similar to that in late Uintan age faunas in both Trans-Pecos, Texas and in the Uinta Basin of Utah. Palaeoecologic evidence from associated plant, invertebrate and vertebrate remains indicates that the regional community setting was a tropical mangrove swamp fringing a lowland coastal rain forest. This late middle Eocene climate was probably similar to the early middle Eocene climate which prevailed in Germany at the time the Messel community inhabited the region. A review of stratigraphic occurrences of Paleogene land mammal remains across the Gulf Coastal Plain indicates that the Casa Blanca fauna is one of only two Paleogene land mammal communities known from Gulf Coastal deposits. These coastal land mammal occurrences provide rare opportunities to correlate Paleogene land mammal communities known from the interior of North America with strata bearing marine species.

Inland dunes fauna and flora from Paleolake Irritila in the Comarca Lagunera, Coahuila, northern Mexico

For over a decade the Chihuahuan Desert has been considered as a hotspot of biodiversity. The diverse aquatic ecosystems, especially, are (and were) rich in mollusk species. The dunes of the Comarca Lagunera, Coahuila, Mexico, are of major importance due to the well-preserved remains of animals and plants in a paleolake that covered a vast area in the region. This paper is the first report of the paleolimnological investigations of the Paleolake Irritila ecosystems in northern Mexico. We determined more than 28 species of gastropods, bivalves, ostracods, algae and one aquatic plant. The dunes contain one of the richest and most diverse fauna of the late Quaternary of northern Mexico. The fossils indicate a permanent but shallow lake with moderate salinity and alkalinity (pH) higher than 8.5, most likely around 10. Most of the mollusks are distributed outside Mexico and restricted to northern latitudes (northern United States and Canada). Several of them are endemic to the southern United States (Florida, Nevada, and Texas). For the first time in North America, using the local fauna and flora preserved in dune sediments, we try to reconstruct the paleoenvironmental conditions in northern Mexico during the late Quaternary.