7 results on '"Farke, Andrew A."'
Search Results
2. A lithornithid (Aves: Palaeognathae) from the Paleocene (Tiffanian) of southern California
- Author
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Stidham, Thomas A., Lofgren, Don, Farke, Andrew A., Paik, Michael, and Choi, Rachel
- Subjects
bird humerus ,fossil ,Lithornithidae ,Goler Formation ,Tiffanian ,California - Abstract
The proximal end of a bird humerus recovered from the Paleocene Goler Formation of southern California is the oldest Cenozoic record of this clade from the west coast of North America. The fossil is characterized by a relatively large, dorsally-positioned head of the humerus and a subcircular opening to the pneumotricipital fossa, consistent with the Lithornithidae among known North American Paleocene birds, and is similar in size to Lithornis celetius. This specimen from the Tiffanian NALMA extends the known geographic range of lithornithids outside of the Rocky Mountains region in the United States. The inferred coastal depositional environment of the Goler Formation is consistent with a broad ecological niche of lithornithids. The age and geographic distribution of lithornithids in North America and Europe suggests these birds dispersed from North America to Europe in the Paleocene or by the early Eocene. During the Paleogene the intercontinental dispersal of lithornithids likely occurred alongside other known bird and mammalian movements that were facilitated by climatic and sea level changes.
- Published
- 2014
3. Leidyosuchus (Crocodylia: Alligatoroidea) from the Upper Cretaceous Kaiparowits Formation (late Campanian) of Utah, USA
- Author
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Farke, Andrew A., Henn, Madison M., Woodward, Samuel J., and Xu, Heendong A.
- Subjects
Kaiparowits Formation ,Western Interior Basin ,Alligatoroidea ,Leidyosuchus ,Biogeography ,Paleontology - Abstract
Several crocodyliform lineages inhabited the Western Interior Basin of North America during the late Campanian (Late Cretaceous), with alligatoroids in the Kaiparowits Formation of southern Utah exhibiting exceptional diversity within this setting. A partial skeleton of a previously unknown alligatoroid taxon from the Kaiparowits Formation may represent the fifth alligatoroid and sixth crocodyliform lineage from this unit. The fossil includes the lower jaw, numerous osteoderms, vertebrae, ribs, and a humerus. The lower jaw is generally long and slender, and the dentary features 22 alveoli with conical, non-globidont teeth. The splenial contributes to the posterior quarter of the mandibular symphysis, which extends posteriorly to the level of alveolus 8, and the dorsal process of the surangular is forked around the terminal alveolus. Dorsal midline osteoderms are square. This combination of character states identifies the Kaiparowits taxon as the sister taxon of the early alligatoroid Leidyosuchus canadensis from the Late Cretaceous of Alberta, the first verified report of the Leidyosuchus (sensu stricto) lineage from the southern Western Interior Basin. This phylogenetic placement is consistent with at least occasional faunal exchanges between northern and southern parts of the Western Interior Basin during the late Campanian, as noted for other reptile clades.
- Published
- 2014
4. A small short-necked hupehsuchian from the lower Triassic of Hubei Province, China.
- Author
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Chen, Xiao-hong, Farke, Andrew A1, Chen, Xiao-hong, Motani, Ryosuke, Cheng, Long, Jiang, Da-yong, Rieppel, Olivier, Chen, Xiao-hong, Farke, Andrew A1, Chen, Xiao-hong, Motani, Ryosuke, Cheng, Long, Jiang, Da-yong, and Rieppel, Olivier
- Abstract
Hupehsuchia is a group of enigmatic Triassic marine reptiles that is known exclusively from two counties in Hubei Province, China. One of the common features of the group was a modestly long neck with nine to ten cervical vertebrae. We report a new species of Hupehsuchia, Eohupehsuchus brevicollis gen. et sp. nov., which for the first time shows a short neck in this group, with six cervicals. The configuration of the skull roof in Eohupehsuchus is also unique among Hupehsuchia, with narrow frontals and posteriorly shifted parietals, warranting recognition of a new species. The taxon superficially resembles Nanchangosaurus in retaining hupehsuchian plesiomorphies, such as low neural spines and small body size. However, its limbs are well-developed, unlike in Nanchangosaurus, although the latter genus is marginally larger in body length. Thus, the individual is unlikely to be immature. Also, Eohupehsuchus shares a suite of synapomorphies with Hupehsuchus, including the second and third layers of dermal ossicles above the dorsal neural spines. A phylogenetic analysis suggests that the new species is not the most basal hupehsuchian despite its short neck, and instead forms the sister taxon of Hupehsuchidae. Until recently, Hupehsuchia contained only two monotypic genera. Now there are at least four genera among Hupehsuchia, and the undescribed diversity is even higher. The left forelimb of the only specimen is incomplete, ending with broken phalanges distally. The breakage could only have occurred pre-burial. The individual may have been attacked by a predator and escaped, given that scavenging is unlikely.
- Published
- 2014
5. Radiographs reveal exceptional forelimb strength in the sabertooth cat, Smilodon fatalis.
- Author
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Meachen-Samuels, Julie A, Farke, Andrew Allen1, Meachen-Samuels, Julie A, Van Valkenburgh, Blaire, Meachen-Samuels, Julie A, Farke, Andrew Allen1, Meachen-Samuels, Julie A, and Van Valkenburgh, Blaire
- Abstract
BackgroundThe sabertooth cat, Smilodon fatalis, was an enigmatic predator without a true living analog. Their elongate canine teeth were more vulnerable to fracture than those of modern felids, making it imperative for them to immobilize prey with their forelimbs when making a kill. As a result, their need for heavily muscled forelimbs likely exceeded that of modern felids and thus should be reflected in their skeletons. Previous studies on forelimb bones of S. fatalis found them to be relatively robust but did not quantify their ability to withstand loading.Methodology/principal findingsUsing radiographs of the sabertooth cat, Smilodon fatalis, 28 extant felid species, and the larger, extinct American lion Panthera atrox, we measured cross-sectional properties of the humerus and femur to provide the first estimates of limb bone strength in bending and torsion. We found that the humeri of Smilodon were reinforced by cortical thickening to a greater degree than those observed in any living felid, or the much larger P. atrox. The femur of Smilodon also was thickened but not beyond the normal variation found in any other felid measured.Conclusions/significanceBased on the cross-sectional properties of its humerus, we interpret that Smilodon was a powerful predator that differed from extant felids in its greater ability to subdue prey using the forelimbs. This enhanced forelimb strength was part of an adaptive complex driven by the need to minimize the struggles of prey in order to protect the elongate canines from fracture and position the bite for a quick kill.
- Published
- 2010
6. Biomechanical consequences of rapid evolution in the polar bear lineage.
- Author
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Slater, Graham J, Farke, Andrew Allen1, Slater, Graham J, Figueirido, Borja, Louis, Leeann, Yang, Paul, Van Valkenburgh, Blaire, Slater, Graham J, Farke, Andrew Allen1, Slater, Graham J, Figueirido, Borja, Louis, Leeann, Yang, Paul, and Van Valkenburgh, Blaire
- Abstract
The polar bear is the only living ursid with a fully carnivorous diet. Despite a number of well-documented craniodental adaptations for a diet of seal flesh and blubber, molecular and paleontological data indicate that this morphologically distinct species evolved less than a million years ago from the omnivorous brown bear. To better understand the evolution of this dietary specialization, we used phylogenetic tests to estimate the rate of morphological specialization in polar bears. We then used finite element analysis (FEA) to compare the limits of feeding performance in the polar bear skull to that of the phylogenetically and geographically close brown bear. Results indicate that extremely rapid evolution of semi-aquatic adaptations and dietary specialization in the polar bear lineage produced a cranial morphology that is weaker than that of brown bears and less suited to processing tough omnivorous or herbivorous diets. Our results suggest that continuation of current climate trends could affect polar bears by not only eliminating their primary food source, but also through competition with northward advancing, generalized brown populations for resources that they are ill-equipped to utilize.
- Published
- 2010
7. Biomechanical consequences of rapid evolution in the polar bear lineage
- Author
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Paul Yang, Blaire Van Valkenburgh, Leeann Louis, Graham J. Slater, Borja Figueirido, and Farke, Andrew Allen
- Subjects
0106 biological sciences ,Ecology/Global Change Ecology ,Evolutionary Biology/Paleontology ,Male ,General Science & Technology ,media_common.quotation_subject ,Lineage (evolution) ,Carnivora ,Finite Element Analysis ,Zoology ,lcsh:Medicine ,Evolutionary Biology/Evolutionary Ecology ,Biology ,010603 evolutionary biology ,01 natural sciences ,Competition (biology) ,03 medical and health sciences ,Phylogenetics ,Ecology/Conservation and Restoration Ecology ,Blubber ,Specialization (functional) ,Animals ,lcsh:Science ,Muscle, Skeletal ,Phylogeny ,030304 developmental biology ,media_common ,Nutrition ,0303 health sciences ,Herbivore ,Multidisciplinary ,Phylogenetic tree ,Ecology ,lcsh:R ,Skull ,Skeletal ,15. Life on land ,Biological Evolution ,Biomechanical Phenomena ,Muscle ,lcsh:Q ,Omnivore ,Ursidae ,Research Article - Abstract
The polar bear is the only living ursid with a fully carnivorous diet. Despite a number of well-documented craniodental adaptations for a diet of seal flesh and blubber, molecular and paleontological data indicate that this morphologically distinct species evolved less than a million years ago from the omnivorous brown bear. To better understand the evolution of this dietary specialization, we used phylogenetic tests to estimate the rate of morphological specialization in polar bears. We then used finite element analysis (FEA) to compare the limits of feeding performance in the polar bear skull to that of the phylogenetically and geographically close brown bear. Results indicate that extremely rapid evolution of semi-aquatic adaptations and dietary specialization in the polar bear lineage produced a cranial morphology that is weaker than that of brown bears and less suited to processing tough omnivorous or herbivorous diets. Our results suggest that continuation of current climate trends could affect polar bears by not only eliminating their primary food source, but also through competition with northward advancing, generalized brown populations for resources that they are ill-equipped to utilize.
- Published
- 2010
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