This content will become publicly available on January 1, 2024
- Award ID(s):
- 1949742
- NSF-PAR ID:
- 10438574
- Date Published:
- Journal Name:
- Revista mexicana de ciencias geológicas
- Volume:
- 40
- Issue:
- 1
- ISSN:
- 1026-8774
- Page Range / eLocation ID:
- 214-226
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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A complete humerus referred to Agriotherium is described, collected from early-late Hemphillian deposits from Zacatecas. Agriotherium is widely represented by isolated molars, mandibles, and maxillae in early-late Hemphillian faunas of Eurasia and North America. In the literature, postcranial elements are scarce and briefly described with little detail. The greatest diversity is known from the Langebaanweg quarry in South Africa; however, the only complete specimen is from Mexico. The proximal end is described, and the humerus shares similarities with the description of the distal end from South Africa, in which the medial epicondyle and crest of the lateral epicondyle are reduced, which can be considered as a limitation in the hunting of larger prey for food. This implies that Agriotherium was not strictly carnivorous but was a predator-scavenger with an omnivorous diet that included plants and fruits.more » « less
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Abstract—In the San Miguel de Allende basin, Guanajuato State, Mexico, two mandibles of gomphotheriids were collected, and by their diagnostic characters have been assigned to Stegomastodon primitivus. The jaws correspond to different ontogenetic and stratigraphic ages. In the Rancho El Ocote fauna, in the upper part of the Hemphillian stratigraphic sequence, the mandible of a young individual and isolated upper and lower molars were collected together with the mandible from the Blanco layer, which has been assigned a latest Hemphillian (Hh4) age. The molars have characters considered more primitive than those described for Stegomastodon primitivus (= Stegomastodon rexroadensis), characteristic of an early Blancan age in North American faunas. The jaw from the Blanco layer has a very short anterior symphysis, straight and ending in a narrow structure that forms the lingual canal. It has no evidence of tusks. The isolated molars present the most primitive characters referred to a Stegomastodon individual: The trefoil and entotrefoil cusps are simple without folds (ptychodonty) or accessory enamel tubercles (choerodont). The isolated M3/m3 has with four lophs/lophids and two large cusps posterior to the fourth lophs/lophids. The m2 has three lophids and two small conids behind the tritolophid, that, in advanced states of wear, form a posterior half lophid more evident in molars with greater wear. There are no stratigraphic indexes of a late Hemphillian or early Blancan age in the Blanco Layer. Throughout the Blanco Layer only Dinohippus mexicanus is present. Zircons separated from ash in the same layer where the Stegomastodon primitivus mandible was collected yielded a 4.85+0.17 Ma U-Pb age, which corresponds to the latest Hemphillian (Hh4). This Rancho El Ocote record is the oldest known among North American faunas. This result assumed that the possible diversification of gomphotheriids in faunas of central Mexico happened before that expected by Savage (1955) in his probable phyletic dispersal pattern of the North American gomphotheriids. A mandible of an old adult gomphothere was collected in the Arroyo Earth Watch, in Los Galvanes area. The fossil was found in sediments assigned to the early Blancan. The jaw is complete without distortion, and it only retains the m3 in an advanced state of wear. This tooth only has five lophids that differentiate it from the m3s of Cuchillo Negro Creek and Elephant Butte Lake Stegomastodon of the early Blancan of New Mexico, that have 5+ to six lophids. The zircons analyzed by the U / Pb method gave an age of 2.9±0.07 Ma for the Stegomastodon jaw from Los Galvanes, consistent with the early Blancan. This record correlates with specimens from New Mexico’s Cuchillo Negro Creek and Elephant Butte Lake faunas, that have a radiometric age of 3.1±0.3 Ma, early Blancan. The similarity of these radiometric ages suggests that Stegomastodon primitivus had a wide geographic distribution in the early Blancan.more » « less
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Abstract Cistecephalids are among the most distinctive Permian dicynodonts because of their highly derived skulls and postcrania, which indicate a fossorial ecology. Four cistecephalid species have been described from India, South Africa, and Tanzania; a fifth putative species has been reported from the Luangwa Basin of Zambia but never formally described. Here we present a detailed description of the Luangwa Basin cistecephalid, which we name
Kembawacela kitchingi gen. et. sp. nov. The most obvious diagnostic character ofK. kitchingi is the presence of caniniform tusks in most specimens. Other important characters include a pineal foramen located at the posterior end of the skull roof; an interparietal that has a pair of anterior processes that extend onto the dorsal surface of the skull, flanking the pineal foramen (but otherwise is restricted to the occipital surface); an undivided nuchal crest; and a trough on the ventral surface of the mid‐ventral vomerine plate. Phylogenetic analysis reconstructsKembawacela as a basal cistecephalid and confirms that Cistecephalidae is a well‐supported clade. However, relationships within the clade received low branch support. Increased knowledge of cistecephalid diversity shows that they vary in functionally relevant characters, such as degree of inflation of the bony vestibule and the morphology of the scapula and humerus, indicating the need for a more nuanced approach to the relationship between form, function and ecology in the clade. The highly allopatric distribution of cistecephalid species suggests that they experienced strong interspecific competition for limited resources and had limited dispersal ability, similar to extant subterranean mammals. -
null (Ed.)The cranium of Adalatherium hui, as represented in the holotype and only specimen (UA 9030), is only the second known for any gondwanatherian mammal, the other being that of the sudamericid Vintana sertichi. Both Adalatherium and Vintana were recovered from the Upper Cretaceous (Maastrichtian) Maevarano Formation of northwestern Madagascar. UA 9030 is the most complete specimen of a gondwanatherian yet known and includes, in addition to the cranium, both lower jaws and a complete postcranial skeleton. Aside from Adalatherium and Vintana, gondwanatherians are otherwise represented only by isolated teeth and lower jaw fragments, belonging to eight monotypic genera from Late Cretaceous and Paleogene horizons of Madagascar, the Indian subcontinent, Africa, South America, and the Antarctic Peninsula. Although the anterior part of the cranium is very well preserved in UA 9030, the posterior part is not. Nonetheless, comparable parts of the crania of Adalatherium and Vintana indicate some level of common ancestry through possession of several synapomorphies, primarily related to the bony composition, articular relationships, and features of the snout region. Overprinted on this shared morphology are a host of autapomorphic features in each genus, some unique among mammaliaforms and some convergent upon therian mammals. The cranium of Adalatherium is compared with the crania of other mammaliamorphs, particularly those of allotherians or purported allotherians (i.e., haramiyidans, euharamiyidans, multituberculates, Cifelliodon, and Megaconus). Particular emphasis is placed on several recently described forms: the enigmatic Cifelliodon from the Early Cretaceous of Utah and several new taxa of euharamiyidans from the Late Jurassic of China.more » « less
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