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H H Covert

Publications and source records attributed to H H Covert.

8 recordsLinked to original sources
PubMed2000

New skeletal remains of Omomys (Primates, Omomyidae): functional morphology of the hindlimb and locomotor behavior of a Middle Eocene primate.

New associated craniodental and postcranial remains of Omomys carteri from Bridger C beds in Uinta County, Wyoming represent the largest and most nearly complete single taxon sample of omomyid postcranial fossils presently known. They allow, for the first time, a description and detailed analysis of the functional morphology of the hindlimb of this middle Eocene omomyine primate. Comparisons of pelvic, femoral, tibial, and pedal morphology and metrics with a large sample of prosimian primates of known locomotor behavior suggest that Omomys possessed a highly distinctive mosaic of functional adaptations related to active quadrupedalism and leaping. Traits suggestive of quadrupedalism include the lengths of the ischium and ilium, position of the femoral trochanters, and lengths and features of the tarsal bones. Morphological traits that suggest leaping include a semi-cylindrical femoral head with moderate posterior expansion of the articular surface, greater trochanter projecting anterior to the femoral shaft, deeper than wide femoral condyles, narrow and deep patellar groove with prominent lateral border, elongated calcaneus, and close aposition of distal tibia and fibula. While Omomys most closely resembles active quadrupedal cheirogaleids like Cheirogaleus and Mirza, leaping must have been an important component of its locomotor repertoire. In this respect, Omomys closely resembles other North American omomyines (notably Hemiacodon), and is significantly more generalized postcranially than European microchoerines (e.g., Microchoerus, Nannopithex, and Necrolemur).

Animals↗
PubMed2000

The petrosal of Omomys carteri and the evolution of the primate basicranium.

The first omomyine petrosals, those of Omomys carteri, are described. Omomys probably had a tympanic bulla and canals for the intratympanic carotid circulation derived from the petrosal bone. The stapedial and promontory canals were complete, large and subequal. The posterior carotid foramen entered the bulla posteromedially. The intratympanic portion of the facial nerve was fully enclosed in bone, the stapedius fossa is extrabullar and the parotic fissure is patent. The mastoid was pneumatized from the epitympanic recess and a supracochlear cavity may have been present. The Omomys petrosals exhibit a generic omomyiform morphology, exhibiting no features that can be interpreted as autapomorphies and only one feature shared with adapiforms. The monophyly of Omomyiformes is based on other cranial characters, dental and postcranial characters assessed elsewhere. The similarity of the Shanghuang petrosal to the petrosals of omomyiforms, as well as the ambiguous evidence of its association, suggest that an omomyiform affinity for that petrosal cannot be ruled out.

Animals↗
PubMed1999

New body mass estimates for Omomys carteri, a middle Eocene primate from North America.

We report new body mass estimates for the North American Eocene primate Omomys carteri. These estimates are based on postcranial measurements and a variety of analytical methods, including bivariate regression, multiple regression, and principal components analysis (PCA). All body mass estimation equations show high coefficients of determination (R2), and some equations exhibit low prediction errors in accuracy tests involving extant species of body size similar to O. carteri. Equations derived from PCA-summarized data and multiple regression generally perform better than those based on single variables. The consensus of estimates and their statistics suggests a body mass range of 170-290 g. This range is similar to previous estimates for this species based on first molar area (Gingerich, J Hum Evol 10:345-374, 1981; Conroy, Int J Primatol 8:115-137, 1987).

Animals↗
PubMed1994

New early eocene anaptomorphine primate (Omomyidae) from the Washakie Basin, Wyoming, with comments on the phylogeny and paleobiology of anaptomorphines.

Recent paleontological collecting in the Washakie Basin, southcentral Wyoming, has resulted in the recovery of over 100 specimens of omomyid primates from the lower Eocene Wasatch Formation. Much of what is known about anaptomorphine omomyids is based upon work in the Bighorn and Wind River Basins of Wyoming. This new sample documents greater taxonomic diversity of omomyids during the early Eocene and contributes to our understanding of the phylogeny and adaptations of some of these earliest North American primates. A new middle Wasatchian (Lysitean) anaptomorphine, Anemorhysis savagei, n. sp., is structurally intermediate between Teilhardina americana and other species of Anemorhysis and may be a sister group of other Anemorhysis and Trogolemur. Body size estimates for Anemorhysis, Tetonoides, Trogolemur, and Teilhardina americana indicate that these animals were extremely small, probably less than 50 grams. Analysis of relative shearing potential of lower molars of these taxa indicates that some were primarily insectivorous, some primarily frugivorous, and some may have been more mixed feeders. Anaptomorphines did not develop the extremes of molar specialization for frugivory or insectivory seen in extant prosimians. Incisor enlargement does not appear to be associated with specialization in either fruits or insects but may have been an adaptation for specialized grooming or food manipulation.

Adaptation, Physiological↗
PubMed1991

Biomechanical association of dental and temporomandibular pathology in a medieval Nubian population.

An analysis of the relationship between oral pathology and degenerative change at the temporomandibular joint (TMJ) was undertaken on an archaeological sample of 122 adult crania from the Medieval site of Kulubnarti in Sudanese Nubia. The crania were sorted into 2 groups: those demonstrating clearly visible bony changes at the joint (TMJ+) and those without visible change (TMJ-). These groups were compared according to 1) age; 2) sex; 3) active dental pathologies (abscesses, caries, partial socket resorption); 4) tooth loss with complete socket resorption; and 5) dental attrition. No statistically significant association was evident between degenerative change at the TMJ and age, active dental pathologies, or dental attrition; however, sex differences and posterior tooth loss with complete socket resorption revealed a significant correspondence to degenerative TMJ changes. Both of these factors agree with the clinical literature and with biomechanical models (most notably that of Hylander) based upon modern populations. Furthermore, the results support the contention that paleopathological conditions can be analyzed from a clinical and functional biomechanical perspective.

History, Medieval↗
PubMed1990

Phylogenetic relationships among the Notharctinae of North America.

Study of over 1,000 specimens representing all notharctine genera and species leads to the conclusion that current concepts about the relationships of genera within the Notharctinae are incorrect. The following describes the more probable relationships among these genera. 1) Smilodectes and Notharctus are more closely related to each other than either is to any known early Eocene notharctine. Synapomorphies linking these genera include relatively narrow upper and lower molars, a relatively low-crowned P4, and paraconid size reduction on M1-3. 2) Among known Wasatchian notharctines, a clade consisting of Copelemur tutus and Cop. praetutus shares several lower molar synapomorphies with the Notharctus-Smilodectes clade, and therefore appears to form the Wasatchian sister group of Bridgerian notharctines. Synapomorphies documenting this relationship include well-developed entoconid notches on P4-M2, an anteriorly placed paraconid on M2, and a long premetacristid on M2. 3) Copelemur and Pelycodus are independently derived from early North American Cantius. Recent suggestions that the European adapine taxa Leptadapis priscus and Microadapis sciureus share special phylogenetic relationships with Smilodectes are rejected. The reduced (or lack of a) paraconid and morphology of the paracristid and other features identified as synapomorphies linking these adapines with Smilodectes are also characteristic of most other adapines as well (e.g., other species of Leptadapis, Adapis, Europolemur, and Anchomomys). Such traits developed independently in Smilodectes, which is clearly a notharctine on the basis of many synapomorphies and thus are not evidence of a close phylogenetic relationship between Smilodectes and L. priscus or M. sciureus.

Animals↗
PubMed1983

True grit: a microwear experiment.

Recently we noted the effects of experimental diets on microscopic dental wear in the American opossum and concluded that it might prove difficult to distinguish the microwear produced by an insectivorous diet from that produced by some kinds of herbivorous ones. We also noted that wear caused by gritty diets and those containing plant opal, although they might be confused with one another, are easily distinguished from other sorts of dietary wear. Our conclusions have been challenged on the basis that possibly we did not allow sufficient time in the experiments for diagnostic wear patterns to emerge. Additional data reported here show that this is not so. Even in our "control" animals, fed a relatively soft unabrasive diet, enough time elapsed to produce significant dental wear. A new technique is described which for the first time allows the study of changing patterns of microscopic wear in a living animal over a period of time, thus allowing each animal to serve as its own control. A solution containing a broad-spectrum proteolytic enzyme when applied to the teeth of an anesthetized animal removes the proteinaceous coat (pellicle) which will otherwise obscure wear scratches. Precision dental impressions can then be made which reveal the details of the pattern of microwear on the teeth.

Animals↗