Biomedical subjects

Laura MacLatchy

Publications and source records attributed to Laura MacLatchy.

6 recordsLinked to original sources

PubMed2006

A fossil hominoid proximal femur from Kikorongo Crater, southwestern Uganda.

The external morphology of a fragmentary right proximal femur from southwestern Uganda is described here. Discovered in the Kikorongo Crater of Queen Elizabeth National Park in 1961, this specimen was informally assigned to Homo sapiens (although never described) and tentatively dated to the late Pleistocene. However, because aspects of the external morphology of the femur align the fossil with the African great apes, we suggest that the Kikorongo femur may be the first postcranial fossil of the genus Pan. Like the African apes, the Kikorongo specimen lacks both an obturator externus groove and an intertrochanteric line. It has a short femoral neck with a circular cross section, and a narrow and deep superior notch. Using resampling statistics and discriminant function analysis, the Kikorongo femur clustered with the genus Pan, as opposed to Gorilla or Homo. However, if the specimen is from Pan, it would be large for this taxon. Furthermore, features that clearly distinguish the external morphology of Plio-Pleistocene hominin proximal femora from African ape femora, such as the shape of the femoral neck in cross section and femoral neck length, have converged in Holocene humans and African apes. Unfortunately, the internal morphology of the femoral neck of the Kikorongo fossil was not discernable. Although we hypothesize that the Kikorongo femur is from the genus Pan, there is such variability in the proximal femora of modern humans that, although it would be an unusual human, it remains possible that this fossil represents H. sapiens.

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PubMed2006

A new pliopithecoid genus from the early Miocene of Uganda.

A partial face and mandible from the early Miocene site of Napak IX in Uganda are described here as a new genus and species of catarrhine primate, Lomorupithecus harrisoni gen. et sp. nov. The face is among the most complete specimens known for a Miocene small-bodied catarrhine. Several aspects of its anatomy indicate that the new species is a stem catarrhine, and as such, it may provide valuable information pertaining to the primitive catarrhine cranial morphotype. Lomorupithecus is most similar in its facial anatomy to members of the Pliopithecoidea, and these similarities could be interpreted in three ways. They could be symplesiomorphies, which would support the traditional view of the primitive catarrhine cranial morphotype; they could be synapomorphies reflecting a phylogenetic position of Lomorupithecus within Pliopithecoidea; or they could represent convergence. Phylogenetic analysis of Lomorupithecus along with 35 other primates indicates that it is a pliopithecoid. As such, it would be the oldest and only Afro-Arabian member of this otherwise Eurasian clade.

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PubMed2004

The phylogenetic position of Morotopithecus.

The phylogenetic relationship of the Ugandan Miocene hominoid Morotopithecus bishopi to fossil and living hominoids remains to be determined. In a cladistic approach to this question, we used three published Miocene character sets as the basis of a phylogenetic analysis: J. Hum. Evol. 29 (1995) 101; Function, Phylogeny, and Fossils: Miocene Hominoid Evolution and Adaptations, 1997, 389. Because these datasets often describe the same anatomy using different characters and states, three different datasets were created to reflect these alternatives. In addition, new postcranial characters describable in Morotopithecus were added to each of the above datasets and a fourth dataset was created using only postcranial characters. The most parsimonious tree(s) recovered in all analyses consistently placed Morotopithecus as a sister taxon to the extant great apes, with Hylobates sister to this clade. Morotopithecus was also consistently more derived than Proconsul, Afropithecus, and Kenyapithecus (as defined prior to the description of Equatorius), but less derived than Oreopithecus, Sivapithecus (only craniodentally) and Dryopithecus. These results imply that Morotopithecus is more derived than Hylobates. However, gibbons are believed to have branched off by at least 18 Ma while Morotopithecus is dated at >20.6 Ma. Possible explanations include: (1) the dating of the Morotopithecus material is too old; (2) the Hylobates divergence time has been underestimated; (3) the great ape condition, and not that of Hylobates, is primitive for hominoids; (4) the similarities of Morotopithecus and great apes are homoplasies. Given current evidence, the first possibility is unlikely, but it is not possible to choose definitively between the latter three possibilities. This conclusion is supported by the fact that despite the consistencies of the analyses, the addition of Morotopithecus and the use of different characters had a large effect on the placement of other Miocene taxa. This raises questions as to the robustness of the connections between Miocene taxa and extant hominoids since different results can be achieved by changing either a few characters, or by adding a single taxon. Many of the characters used to estimate phylogeny may need to be reassessed before a reliable assessment of the phylogenetic position of Morotopithecus can be achieved.

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PubMed2002

Taxonomic affinities of the Eppelsheim femur.

The taxonomic affinities of the Eppelsheim femur, known as Paidopithex, have been unclear for more than a century. Over the years, due to similarities with Pliopithecus, some authors have considered it a large pliopithecid, while others refer to it as Dryopithecus. The issue could not be resolved, because no definitive Dryopithecus femora were available. With the discovery of the Dryopithecus laietanus skeleton from Can Llobateres (CLl 18800), it has become possible to test the attribution of the Eppelsheim femur to Dryopithecus on the basis of direct morphological and metrical comparisons. By means of allometric techniques, we show that the Eppelsheim and D. laietanus femora fit different hindlimb morphologies with regard to relative length and relative head/neck size, with Paidopithex significantly differing from Dryopithecus, but more closely resembling Pliopithecus. Paidopithex also differs from Dryopithecus in other important aspects, such as its lower neck/shaft angle, lack of elevation of the femoral head above the greater trochanter, more posteriorly oriented lesser trochanter, and proximal shaft diameter thicker anteroposteriorly than mediolaterally. In these features, Paidopithex most closely resembles Pliopithecus in spite of differences in body mass (ca. 22 kg vs. ca. 10 kg, respectively). These features suggest that Paidopithex used a primitive locomotor pattern associated with arboreal quadrupedalism, instead of the more derived pattern displayed by Dryopithecus. Currently available evidence confirms that the attribution of Paidopithex to Dryopithecus can be rejected. Paidopithex could be a large and otherwise unknown pliopithecid, but the possibility cannot be ruled out that it represents a third kind of catarrhine.

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PubMed2002

New Sivapithecus postcranial specimens from the Siwaliks of Pakistan.

Several new postcranial elements of Sivapithecus from the Siwaliks of Pakistan are described. These include a distal femur from the U-level of the Dhok Pathan Formation, a navicular from the Chinji Formation, and seven manual and pedal phalanges from the Nagri Formation. The functional morphology of these elements adds new detail to the reconstruction of Sivapithecus positional behavior. Femoral cross-sectional geometry indicates that the shaft was adapted to support mediolaterally directed loading. Femoral condylar asymmetry and a broad but shallow trochlea are distinctly ape-like, revealing capabilities for both rotation and withstanding eccentric loading in the knee. The navicular is characterized by features relating to a broad mid-tarsus and broad distal articulations for the cuneiforms. It also lacks a navicular tubercle as in Pongo. These features suggest that the foot was capable of a powerful grip on large supports, with an inversion/supination capability that would permit foot placement in a variety of positions. The morphology of the new phalanges, including evidence for a relatively large pollex, similarly suggests powerful grasping, consistent with prior evidence from the hallux and tarsus. The functional features of the new specimens permit refinement of previous interpretations of Sivapithecus positional capabilities. They suggest a locomotor repertoire dominated by pronograde activities and also such antipronograde activities as vertical climbing and clambering, but not by antipronograde suspensory activities as practiced by extant apes.

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PubMed2002

A comparison of the femoral head and neck trabecular architecture of Galago and Perodicticus using micro-computed tomography (microCT).

Innovations in micro-computed tomography (microCT) in the medical field have resulted in the development of techniques that allow the precise quantification of bone density and fabric related parameters of trabecular bone. For the purpose of this study, the technique was applied to a small sample of Perodicticus potto and Galago senegalensis femora to see if differences in loading environment elicit the predicted effects on trabecular structure. While the overall bone volume was approximately three times larger in the potto, there was no significant difference in the apparent volume density in the two taxa. When regional differences in the proximal femur were examined, the cancellous bone of the femoral head of Perodicticus potto and Galago senegalensis, while not differing in volume density, showed differences in trabecular orientation, with the potto having more randomly oriented trabeculae than the bushbaby. This was as hypothesized, given that the bushbaby submits its femora to more stereotypical loading environments than the potto. In the femoral neck, the cancellous bone was not only more randomly oriented, it was also denser in the potto compared with the bushbaby. This suggests that trabecular morphology may be extremely sensitive to certain differences in the loading environment and that this information, combined with information on cortical bone structure and external geometry, will result in a more complete understanding of how bone shape and composition correspond to loading and locomotor patterns. Ultimately, a synthesis of these different lines of evidence may have considerable applications in paleontological studies that attempt to reconstruct bone use from morphology.

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