News Article | April 17, 2017
Scientists have long wondered what the earliest dinosaur relatives looked like. Most assumed they would resemble miniature dinosaurs, about the size of chickens, and walk on two legs. The discovery of Teleocrater rhadinus, however, has forced scientists to reassess their ideas. Based on a fossil unearthed in southern Tanzania, these early relatives were carnivorous animals that measured approximately 7-10 feet long, with long necks and tails. Rather than walking on two legs, they walked on four crocodilian-like legs. The finding, published today in the journal Nature, fills a gap in the fossil record. "The research sheds light on the distribution and diversity of the ancestors of crocodiles, birds, and dinosaurs," said Judy Skog, a program director in the National Science Foundation's (NSF) Division of Earth Sciences, which funded the research. "It indicates that dinosaur origins should be re-examined now that we know more about the complex history and traits of these early ancestors." T. rhadinus predated dinosaurs, living more than 245 million years ago during the Triassic Period. It shows up in the fossil record right after a large group of reptiles known as archosaurs split into a bird branch (leading to dinosaurs and eventually birds) and a crocodile branch (leading to alligators and crocodiles). T. rhadinus and its kin are the earliest known members of the bird branch of the archosaurs. "The discovery of such an important new species is a once-in-a-lifetime experience," said Sterling Nesbitt, a paleobiologist at Virginia Tech and lead author of the Nature paper. The late paleontologist F. Rex Parrington first discovered T. rhadinus fossils in Tanzania in 1933. The late Alan J. Charig, then-curator of fossil reptiles, amphibians and birds at the Natural History Museum of London, was the first to study those original specimens in the 1950s. Charig could not determine whether the creature was more closely related to crocodilians or to dinosaurs, largely because the specimens lacked ankles and other bones. The new specimens, found in 2015, clear up those questions. The intact ankle bones and other parts of the skeleton helped scientists determine that the species is one of the oldest members of the archosaur tree and had a crocodilian look. Nesbitt and his co-authors chose to honor Charig's work by using the name he selected for the animal, Teleocrater rhadinus, which means "slender complete basin" and refers to the animal's lean build and closed hip socket. "The discovery of Teleocrater fundamentally changes our ideas about the earliest history of dinosaur relatives," said Nesbitt. The team's next steps are to return to southern Tanzania to find missing parts of the T. rhadinus skeleton. "It's so exciting to solve puzzles like Teleocrater, where we can finally tease apart tricky mixed assemblages of fossils and shed light on broader anatomical and biogeographic trends in an iconic group of animals," said Michelle Stocker, a paleobiologist at Virginia Tech and co-author of the paper. Other co-authors include: Richard Butler at the University of Birmingham; Martin Ezcurra at Museo Argentino de Ciencias Naturales; Paul Barrett at the Natural History Museum of London; Kenneth Angielczyk at the Field Museum of Natural History; Roger Smith at the University of the Witwatersrand and Iziko South African Museum; Christian Sidor at the University of Washington; Grzegorz Niedzwiedzki at Uppsala University; Andrey Sennikov at the Borissiak Paleontological Institute and Kazan Federal Univeristy; and Charig. The National Geographic Society Young Explorer program and other institutions also funded the research.
McLeish M.J.,Stellenbosch University |
Van Noort S.,Iziko South African Museum |
Van Noort S.,University of Cape Town
BMC Evolutionary Biology | Year: 2012
Background: The interaction between insects and plants takes myriad forms in the generation of spectacular diversity. In this association a species host range is fundamental and often measured using an estimate of phylogenetic concordance between species. Pollinating fig wasps display extreme host species specificity, but the intraspecific variation in empirical accounts of host affiliation has previously been underestimated. In this investigation, lineage delimitation and codiversification tests are used to generate and discuss hypotheses elucidating on pollinating fig wasp associations with Ficus. Results: Statistical parsimony and AMOVA revealed deep divergences at the COI locus within several pollinating fig wasp species that persist on the same host Ficus species. Changes in branching patterns estimated using the generalized mixed Yule coalescent test indicated lineage duplication on the same Ficus species. Conversely, Elisabethiella and Alfonsiella fig wasp species are able to reproduce on multiple, but closely related host fig species. Tree reconciliation tests indicate significant codiversification as well as significant incongruence between fig wasp and Ficus phylogenies. Conclusions: The findings demonstrate more relaxed pollinating fig wasp host specificity than previously appreciated. Evolutionarily conservative host associations have been tempered by horizontal transfer and lineage duplication among closely related Ficus species. Independent and asynchronistic diversification of pollinating fig wasps is best explained by a combination of both sympatric and allopatric models of speciation. Pollinator host preference constraints permit reproduction on closely related Ficus species, but uncertainty of the frequency and duration of these associations requires better resolution. © 2012 McLeish and van Noort; licensee BioMed Central Ltd.
McLeish M.J.,Stellenbosch University |
McLeish M.J.,South African National Biodiversity Institute |
Van Noort S.,Iziko South African Museum |
Tolley K.A.,South African National Biodiversity Institute
Molecular Ecology | Year: 2010
Ecological processes are manifest in the evolution and form of phenotype diversity. The great abundance of parasitoid species has led to speculation whether rates of speciation and extinction are dependent on parasitoid diversity. If these factors are mutually exclusive, species diversity should fluctuate instead of remaining relatively constant over time. It is not known whether radiations constrained by coevolutionary interactions conform to density-dependent diversification processes. Here we test the prediction that parasitoid fig wasp diversification responds to changes in ecological opportunity and density-independent processes. A phylogenetic approach is used to estimate relative divergence times and infer diversification rate changes using γ-statistics. Monte Carlo constant rates tests that accommodate incomplete sampling could not reject constant rates diversification. Parasitoid fig wasp diversification is consistent with a more complex explanation than density-dependent cladogenesis. The results suggest contemporary African parasitoid fig wasp diversity remains a legacy of an ancient ecological opportunity facilitated by fig tree diversification following the breakup of Pan-African forests and evolution of the savanna biome over the last 55 Ma and the more recent aridification of the African continent in the last 5 Ma. These results imply that amplified phenotypic differentiation of specialist insects coevolving with plants is coupled to evolutionarily infrequent changes in ecological opportunity. © 2010 Blackwell Publishing Ltd.
Mcleish M.,Stellenbosch University |
Guo D.,South African National Biodiversity Institute |
van Noort S.,Iziko South African Museum |
van Noort S.,University of Cape Town |
Midgley G.,South African National Biodiversity Institute
New Phytologist | Year: 2011
The fig tree-fig wasp obligate pollination mutualism has strong ancestral affinities with tropical communities, but is present in much drier contemporary biomes, especially at higher latitudes at the edge of their range. The extent to which adaptation to environmental variables is evolutionarily conserved and whether environmental differences function in ecological speciation of the mutualism are unknown. Here we use climate models and phylogenetic reconstructions to test whether the Ficus-fig wasp mutualism has adapted and radiated into drier climates and led to ecological speciation in both plant and insect. The results showed phylogenetic correspondence between closely related Ficus species with either savanna, forest, or riparian habitat categories, were most strongly explained by both climate and environmental variables. Rare episodes of adaptation to dry apotypic conditions have resulted in substantial radiations into savanna. Inferences were consistent with predictions of niche conservatism and support the postulate that ecological speciation of the mutualism occurs, but under contrasting and intertwined circumstances among plant-pollinator adaptation and tolerance to the environment. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.
McLeish M.J.,Chinese Academy of Sciences |
Beukman G.,Stellenbosch University |
Van Noort S.,Iziko South African Museum |
Van Noort S.,University of Cape Town |
Wossler T.C.,Stellenbosch University
PLoS ONE | Year: 2014
Parasitoid diversity in terrestrial ecosystems is enormous. However, ecological processes underpinning their evolutionary diversification in association with other trophic groups are still unclear. Specialisation and interdependencies among chalcid wasps that reproduce on Ficus presents an opportunity to investigate the ecology of a multi-trophic system that includes parasitoids. Here we estimate the host-plant species specificity of a parasitoid fig wasp genus that attacks the galls of nonpollinating pteromalid and pollinating agaonid fig wasps. We discuss the interactions between parasitoids and the Ficus species present in a forest patch of Uganda in context with populations in Southern Africa. Haplotype networks are inferred to examine intraspecific mitochondrial DNA divergences and phylogenetic approaches used to infer putative species relationships. Taxonomic appraisal and putative species delimitation by molecular and morphological techniques are compared. Results demonstrate that a parasitoid fig wasp population is able to reproduce on at least four Ficus species present in a patch. This suggests that parasitoid fig wasps have relatively broad host- Ficus species ranges compared to fig wasps that oviposit internally. Parasitoid fig wasps did not recruit on all available host plants present in the forest census area and suggests an important ecological consequence in mitigating fitness trade-offs between pollinator and Ficus reproduction. The extent to which parasitoid fig wasps exert influence on the pollination mutualism must consider the fitness consequences imposed by the ability to interact with phenotypes of multiple Ficus and fig wasps species, but not equally across space and time. ©2012 McLeish et al.
Matthews T.,Iziko South African Museum |
Stynder D.D.,University of Cape Town
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011
Subsequent to the initial description of two Aethomys species (Aethomys adamanticola and Aethomys modernis) at the Early Pliocene site of Langebaanweg (LBW), an increase in sample size led to the secure identification of a third, as yet, undescribed species. In addition to this new species, three morphs of existing species, or possibly three new species, were also recognized. Geometric morphometrics was used to explore the relationship of fossil species and morphs with extant Aethomys species, and to assess the intra and inter-specific variation in the size and shape of modern, as well as the LBW, Aethomys specimens. Geometric morphometrics indicates a marked similarity in the upper first molar (M1) shape between all the analyzed species, extant and extinct, and suggests the persistence, over a significant period of time, of a prototype Aethomys M1 shape. The relative warp analyses indicate some overlap in shape between the two modern species, Aethomys chrysophilus and Aethomys namaquensis, as well as some inter-specific variation. These two species differ significantly from one another in terms of size. Variability in terms of size and to a minor extent, shape, was also evident in the fossil Aethomys, and it was concluded that the various fossil morphs investigated did not represent new species, or intra-specific sexual dimorphism, but rather, intra-specific variability in size and shape. Interestingly, the newly-identified LBW Aethomys species, which is similar in appearance to the extant east African Aethomys kaiseri, also showed a similarity in shape and size to A. adamanticola. These results indicate that geometric morphometrics has limitations when differentiating between morphologically similar species. The presence of Aethomys in Namibia at around 10.5 to 9.5Ma, the degree of speciation of Aethomys at LBW, and the similarity of the LBW fossil species to the modern ones (including an East African species), provides good evidence for a southern African origin for modern Aethomys. © 2011 Elsevier B.V.
A new specimen of Promoschorhynchus (Therapsida: Therocephalia: Akidnognathidae) from the Lower Triassic of South Africa and its implications for theriodont survivorship across the Permo-Triassic boundary
Huttenlocker A.K.,University of Washington |
Sidor C.A.,University of Washington |
Smith R.M.H.,Iziko South African Museum
Journal of Vertebrate Paleontology | Year: 2011
The anatomy of a new subadult specimen of eutherocephalian therapsid, attributed to Promoschorhynchus cf. P. platyrhinus, is described from lowermost Triassic Lystrosaurus Assemblage Zone strata in the main Karoo Basin of South Africa. The specimen preserves information previously unknown in the genus, including details of the posterior region of the skull and intertemporal region, and a partial (though disarticulated) postcranial skeleton. A cladistic analysis of 32 therapsid taxa, including 24 Permo-Triassic therocephalian genera, and 121 craniodental and postcranial characters supports the specimen's placement within the Permian akidnognathid genus Promoschorhynchus (making it the youngest documented occurrence of this taxon) within a monophyletic Therocephalia. Inclusion of new postcranial characters strengthens support of the therocephalian clade. The new record of Promoschorhynchus offers insights into the diversity of eutheriodonts across the Permo-Triassic boundary (PTB) in the Karoo Basin. In contrast to cynodonts, therocephalians exhibited decreased rates of cladogenesis across the PTB, with several Triassic lineages having roots in the Late Permian rather than representing earliest Triassic radiations. © 2011 by the Society of Vertebrate Paleontology.
Kennedy W.J.,University of Oxford |
Klinger H.C.,Iziko South African Museum
African Natural History | Year: 2012
Three taxa of desmoceratoid ammonites are recognized in the Lower Albian of northern KwaZulu-Natal, all of them previously known only from Madagascar: Moretella sp., Beudanticeras komihevitraense Collignon, 1950, and Aioloceras besairiei (Collignon, 1949). Madagascan type and figured material, much of it difficult to interpret from the original figures is re-illustrated, and the intraspecific variation and dimorphism in Moretella and Aioloceras are documented.
Rousse P.,Iziko South African Museum |
Van Noort S.,Iziko South African Museum
Zootaxa | Year: 2013
We revise the Afrotropical Lycorininae and describe Lycorina yui Rousse & van Noort sp. nov. from South Africa. An illustrated key to Lycorininae species of the Afrotropical region is provided. Lycorina continentalis (Benoit, 1953) is considered a junior synonym of Lycorinafici Seyrig, 1932, and is newly reported from Uganda and South Africa. Online dichotomous and interactive Lucid keys are available at http://www.waspweb.org.
Asher R.J.,University of Cambridge |
Margaret Avery D.,Iziko South African Museum
Palaeontologia Electronica | Year: 2010
We describe new material of fossil golden moles (Chrysochloridae) from the early Pliocene site of Langebaanweg, South Africa. This site has produced hundreds of isolated craniodental and postcranial elements, all of which are easily identifiable as chrysochlorid. Based on size and morphology, at least three species are represented in this assemblage, two of which are represented by material of sufficient quality to name. Based on relative abundance, humeral and mandibular types can be associated with other material. Craniodentally, the most common Langebaanweg species closely resembles the extant Cape golden mole, Chrysochloris asiatica, but differs in showing a relatively narrow distal humerus, proportionally similar to that of the extant Eremitalpa granti. A second, rarer species is represented by two well-preserved mandibles that exhibit a stout, enlarged lower second incisor, a robust mandibular corpus, and is associated with a less common humeral type that resembles living Chrysochloris. At least one additional species is represented by a small number of relatively large humeri, femora, and scapular fragments. Because it lacks any craniodental representation, it is not named in this paper. We tentatively suggest that the relatively narrow distal margin of the humerus of the new, C. asiatica-like species may have been adapted to a habitat similar to that of the modern E. granti, a "sand-swimming" golden mole currently known from northwestern South Africa and southern Namibia. © Paleontological Association March 2010.