Mammal teeth bring important information regarding phylogeny and diet. However, postcranial elements, although poorly studied for small Paleogene mammals, can provide other significant data. The purpose of this study is to associate tarsal bones with dental specimens for a systematic identification. We thus chose the Belgian locality of Dormaal (Tienen Formation, Belgium) that has yielded the earliest Eocene mammals of Europe. This particularly rich fauna, dated between 55.5 and 55.8 Ma, occurred during the Paleocene-Eocene Thermal Maximum, a key period in the mammal evolution. It is composed by archaic mammals (“condylarths”, arctocyonids, plesiadapiforms, “insectivorans”…) and also by earliest modern taxa (primates, rodents, carnivoraforms, artiodactyls …), representing about 14,000 dental specimens. 488 tarsal bones are studied according to three methods: morphology, relative abundance and relative size. 12 morphotypes of astragali and 18 of calcanei are discriminated and most of them are identified at the level of species (e.g. the marsupial Peratherium constans), genus or family (e.g. ischyromyid rodents). New perspectives in phylogeny and paleoecology are proposed for further studies implying tarsal bones.
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RBINS Staff Publications
The phyletic link of living tarsiers to fossil primates has been a difficult bridge to cross. Although Tarsiidae has been linked to fossil tarsiiforms such as omomyids and microchoerids, as well as to anthropoids, no consensus of opinion has been reached. Here we add several new postcranial elements for one of the most primitive of all tarsiiforms, Teilhardina belgica from Dormaal, Belgium. We compare this new material to that of living and fossil tarsiers as well as to other Eocene fossil primates. Besides the previously known tarsals for Teilhardina, we have been able to add a distal humerus, a proximal ulna, a second metacarpal, a proximal and a distal femur, tibiae, additional tarsals, first metatarsals, and several proximal and middle phalanges. Although most of these postcranial elements compare best with other omomyids, and therefore do not resolve the phyletic relationship of omomyids relative to tarsiers, the fingers and toes of Teilhardina are quite elongated, a similarity to living tarsiers. Middle phalangeal lengths of the diminuitive Teilhardina are comparable in length to much larger species of Tarsius suggesting relatively even longer digits. The digit features of Teilhardina and Tarsius are unusual for primates in general and may in fact represent an ancestral state although hands and feet of other fossil tarsiiforms are needed to test this hypothesis.
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This study evaluates the utility of DNA barcoding to traditional morphology-based species identifications for the fish fauna of the north-eastern Congo basin. We compared DNA sequences (COI) of 821 samples from 206 morphologically identified species. Best match, best close match and all species barcoding analyses resulted in a rather low identification success of 87.5%, 84.5% and 64.1%, respectively. The ratio ‘nearest-neighbour distance/maximum intraspecific divergence’ was lower than 1 for 26.1% of the samples, indicating possible taxonomic problems. In ten genera, belonging to six families, the number of species inferred from mtDNA data exceeded the number of species identified using morphological features; and in four cases indications of possible synonymy were detected. Finally, the DNA barcodes confirmed previously known identification problems within certain genera of the Clariidae, Cyprinidae and Mormyridae. Our results underscore the large number of taxonomic problems lingering in the taxonomy of the fish fauna of the Congo basin and illustrate why DNA barcodes will contribute to future efforts to compile a reliable taxonomic inventory of the Congo basin fish fauna. Therefore, the obtained barcodes were deposited in the reference barcode library of the Barcode of Life Initiative.
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RBINS Staff Publications 2016
