Canid Coprolites from the Late Pleistocene of Hidalgo, Central Mexico: Importance for the Carnivore Record of North America (original) (raw)
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New Canid Remains from Dolores Formation, late Pleistocene-early Holocene, Uruguay
The fossil record of carnivorous mammals in Uruguay is scarce and fragmentary, but informative. In the present contribution, two new records of canids allocated in sediments of the Dolores Formation (late Pleistocene-early Holocene) are described. These records, based on their anatomical-comparative study and multivariate analysis, correspond to two foxes: one of medium size, Cerdocyon thous, conforms to the first record of this taxon in the country, meanwhile the other one, of larger size, is referred to Dusicyon avus and is the first fossil record of this animal in the south of the territory and the second record in the whole country. Until now, the only carnivorous mammals registered in this formation were the hunters of large herbivores (Arctotherium sp. and Smilodon populator). In this way, these discoveries complement and expand the set of placental mammals with a car-nivorous diet for this unit, particularly with the capacity to predate over small-and medium-size mammals.
The fossil record of foxes in South America is very rich, with almost all extant South American species recorded. Currently, three fossil species are known in the Plio-Pleistocene of South America: “Dusicyon” cultridens, Dusicyon avus and “Canis” ensenadensis. In the present work we reviewed the systematics of “Canis” ensenadensis from the Pleistocene of Buenos Aires province using both qualitative and quantitative approaches. We also described a new fossil specimen (MCA 2082) from Buenos Aires Province (Argentina) that shares some similarities with “Canis” ensenadensis. We compared the fossil specimens with a large sample of specimens that includes the living species Lycalopex gymnocercus, L. culpaeus, Cerdocyon thous, L. fulvipes, L. vetulus, L. sechurae and Atelocynus microtis. We performed a Principal Component Analysis using mandibular and dental measurements, and then a geometric morphometric analysis using photographs of the lateral view of the mandible. Our results indicate that “Canis” ensenadensis is a valid species and it should be included in the genus Lycalopex. We also conclude that MCA 2082 is a member of the genus Lycalopex, probably belonging to the species L. ensenadensis. These results suggest that the biochron of L. ensenadensis reaches the Lujanian Age. Even if our assignation of MCA 2082 is incorrect, this specimen represents a different taxon from those already described for the Lujanian, thus the diversity of foxes during the Lujanian is greater than previously known.
Fossil specimens of American mastodons (Mammut americanum) that have been recovered from fluvial sedimentary deposits of the late Pleistocene of southeastern Hidalgo, central Mexico, are formally described. The sample includes cranial and postcranial remains of an adult male that represents one of the most complete mastodons that have been found in Mexico, as well as a molar belonging to an old individual. The material from Hidalgo shows the following diagnostic features of M. americanum: well-developed tusks that curved upward; upper and lower molars with a simple occlusal pattern; last molars with four to five lophs/ids; a medial sulcus between the lophs/ids; a scapula with a straight caudal border, a short and expanded neck, and a glenoid cavity that is oval in outline; a short and robust humerus with a prominent epicondylar crest; a radius with a wide distal end; and an ulna with a well-developed olecranon process and a deep trochlear notch. The dental size of the mastodon from Hidalgo is comparable to that of mastodons from the Gulf Coastal Plain and the Great Lakes region, whereas the limb dimensions are similar to those of the Watkins Glen Mastodon from the late Pleistocene of New York. In order to characterize the diet and habitat of the mastodons from Hidalgo, a stable carbon and oxygen isotope analysis in tooth enamel apatite was performed. The results indicate that studied specimens were mainly C3 browsers (mean δ13C isotope value of -10.06 ‰) that thrived in closed habitats covered by high vegetation, such as trees (mean δ18O isotope value of -4.31 ‰). This information suggests the presence of closed habitats in the southeastern region of Hidalgo, during the second half of the Pleistocene.
Bulletin of the New Mexico Museum of Natural History and Science, 2015
Recent field work and research call for a new look at the carnivorans from the middle Miocene of New Mexico. Here changes in carnivoran guilds through time within the Tesuque Formation as well as the carnivoran diversity in each member are described. The Tesuque Formation in New Mexico contains fossiliferous layers of strata that span the late Hemingfordian through the Clarendonian (and potentially into the earliest early Hemphillian). Borophagines were the dominant carnivorans, and presumably the dominant predators, during the middle Miocene in New Mexico. However, when borophagines become less abundant, canines become more abundant, showing an inverse relationship and perhaps leading to instances where members of these groups utilize similar niches. Hesperocyonines are only present in the early Barstovian, while the large amphicyonids are found only in the late Barstovian, potentially filling an open niche left by the hesperocyonines. While carnivoran diversity drops after the Barstovian, mustelids persist in the early Clarendonian. Felids tend to become less numerous through time, perhaps allowing mustelids to fill the role of the small predators in place of Pseudaelurus (among others), and these may have in turn been replaced by small canines. In addition, this study records the first occurrences of several carnivorans in distinct members, or in the Tesuque Formation as a whole, including the first occurrence of mustelids (non-mephitine mustelids) in the formation. While the carnivoran fauna from the middle Miocene of North America is more diverse, it is noted that the Tesuque carnivoran fauna has a higher percentage of canids, and a lower percentage of mustelids and procyonids. Statistical analyses show each carnivoran group is found in most of the members and so do not cluster differently with the exception of Hesperocyoninae. The Barstovian Skull Ridge and Pojoaque members are the most statistically similar in terms of their carnivoran diversity.
Quaternary International, 2009
The fossil record of large canids is reviewed in order to improve the current South American biostratigraphic chart. This analysis is based on the recent systematic revision of those taxa performed by one of the authors and new field and paleomagnetic works. The first occurrences of large canids are limited to the Early-Middle Pleistocene (Ensenadan stage/age). Theriodictis platensis, ''Canis'' gezi, and Protocyon scagliorum are restricted to the Ensenadan. Most T. platensis specimens came from late Ensenadan levels (0.78-z0.5 Ma), but the oldest one is between 0.78 Ma and 1 Ma old. The biochron of Protocyon troglodytes spans the Ensenadan-Lujanian interval, and its youngest remains are associated with 14 C dates of 25-27/20-10 ka BP. Most individuals of Protocyon tarijensis could be between 1 Ma and 10 ka, but one specimen comes from a level surely younger than 0.78 Ma, and probably younger than 28 ka. The oldest records of the living species Chrysocyon brachyurus are between ca. 0.3 Ma-9 ka BP. The first record of Canis dirus (and Canis by extension) in South America is limited to the latest Pleistocene (<25-27 ka).