James Hansford

Taxonomy-testing and the ‘Goldilocks Hypothesis’: morphometric analysis of species diversity in living and extinct Hispaniolan hutias

Understanding the dynamics of the Late Quaternary Caribbean mammal extinction event is complicated by continuing uncertainty over the taxonomic status of many species. Hispaniola is one of the few Caribbean islands to retain native non-volant mammals; however, there has been little consensus over past or present levels of diversity in Hispaniolan hutias (Capromyidae: Plagiodontinae). Craniodental measurement data from modern hutia specimens, previously classified as both Plagiodontia aedium and P. hylaeum, display morphological differences between Hispaniolas northern and southern palaeo-islands using MANOVA and PCA. Although attempts to amplify mitochondrial DNA from the holotype of P. aedium were unsuccessful, this specimen is morphometrically associated with southern palaeo-island specimens. The mandibular size distribution of recent Plagiodontia specimens is unimodal, but the Late Quaternary mandibular size distribution is multimodal and displays much broader measurement spread, representing multiple extinct species. Finite Mixture Analysis was used to assess the best fit of different taxonomic hypotheses to the fossil mandibular size distribution. All retained FMA models include living hutias and P. spelaeum as distinct taxa; PCA further demonstrates that levels of morphological variation between modern hutia populations are lower than levels between living hutias and P. spelaeum, so that living hutias are interpreted as the single species P. aedium. Taxonomic differentiation for larger-bodied hutias is less well defined, but most retained models show only one larger species, for which the only available name is P. velozi. ‘Plagiodontia’ araeum is morphologically distinct from other species and is reassigned to Hyperplagiodontia. Hispaniolas plagiodontine fauna has lost its largest and smallest representatives; similar trends of body size selectivity in extinction risk are shown more widely across the Caribbean mammal fauna, possibly due to different regional anthropogenic threats (invasive mammals, hunting) affecting small-bodied and large-bodied mammals during the recent past. This apparent pattern of extinction selectivity is named the ‘Goldilocks Hypothesis’.

A new subspecies of hutia ( Plagiodontia , Capromyidae, Rodentia) from southern Hispaniola

Continued uncertainty persists over the taxonomic status of many threatened Caribbean mammal populations. Recent molecular analysis has identified three genetically isolated allopatric hutia populations on Hispaniola that diverged during the Middle Pleistocene, with observed levels of sequence divergence interpreted as representing subspecies-level differentiation through comparison with genetic data for other capromyids. Subsequent analysis of existing museum specimens has demonstrated biogeographically congruent morphometric differentiation for two of these three populations, Plagiodontia aedium aedium (southwestern population) and P. aedium hylaeum (northern population). We report the first craniodental material for the southeastern Hispaniolan hutia population, and demonstrate that this population can also be differentiated using quantitative morphometric analysis from other Hispaniolan hutia subspecies. The holotype skull of P. aedium aedium, of unknown geographic provenance within Hispaniola, clusters morphometrically with the southwestern population. The southeastern Hispaniolan subspecies is described as Plagiodontia aedium bondi subsp. nov., and is assessed as Endangered under Criterion B1a,biii,v on the IUCN Red List.

A new species of extinct Late Quaternary giant tortoise from Hispaniola

Insular giant tortoise diversity has been depleted by Late Quaternary extinctions, but the taxonomic status of many extinct populations remains poorly understood due to limited available fossil or subfossil material, hindering our ability to reconstruct Quaternary island biotas and environments. Giant tortoises are absent from current-day insular Caribbean ecosystems, but tortoise remains from Quaternary deposits indicate the former widespread occurrence of these animals across the northern Caribbean. We report new Quaternary giant tortoise material from several cave sites in Pedernales Province, southern Dominican Republic, Hispaniola, representing at least seven individuals, which we describe as Chelonoidis marcanoi sp. nov. Although giant tortoise material was first reported from the Quaternary record of Hispaniola almost 35 years ago, tortoises are absent from most Quaternary deposits on the island, which has been studied extensively over the past century. The surprising abundance of giant tortoise remains in both vertical and horizontal caves in Hispaniolas semi-arid ecoregion may indicate that this species was adapted to open dry habitats and became restricted to a habitat refugium in southeastern Hispaniola following climatic-driven environmental change at the Pleistocene-Holocene boundary. Hispaniolas dry forest ecosystem may therefore have been shaped by giant tortoises for much of its evolutionary history.

Early Holocene human presence in Madagascar evidenced by exploitation of avian megafauna

Radiocarbon dates of perimortem tool marks reveal human presence in Madagascar 6000 years earlier than previously thought. Previous research suggests that people first arrived on Madagascar by ~2500 years before present (years B.P.). This hypothesis is consistent with butchery marks on extinct lemur bones from ~2400 years B.P. and perhaps with archaeological evidence of human presence from ~4000 years B.P. We report >10,500-year-old human-modified bones for the extinct elephant birds Aepyornis and Mullerornis, which show perimortem chop marks, cut marks, and depression fractures consistent with immobilization and dismemberment. Our evidence for anthropogenic perimortem modification of directly dated bones represents the earliest indication of humans in Madagascar, predating all other archaeological and genetic evidence by >6000 years and changing our understanding of the history of human colonization of Madagascar. This revision of Madagascar’s prehistory suggests prolonged human-faunal coexistence with limited biodiversity loss.

New genus of extinct Holocene gibbon associated with humans in Imperial China

The noblewomans ape Human activities are causing extinctions across a wide array of taxa. Yet there has been no evidence of humans directly causing extinction among our relatives, the apes. Turvey et al. describe a species of gibbon found in a 2200- to 2300-year-old tomb ascribed to a Chinese noblewoman. This previously unknown species was likely widespread, may have persisted until the 18th century, and may be the first ape species to have perished as a direct result of human activities. This discovery may also indicate the existence of unrecognized primate diversity across Asia. Science, this issue p. 1346 A previously unknown gibbon species found in a Chinese tomb suggests that past Asian ape diversity has been lost. Although all extant apes are threatened with extinction, there is no evidence for human-caused extinctions of apes or other primates in postglacial continental ecosystems, despite intensive anthropogenic pressures associated with biodiversity loss for millennia in many regions. Here, we report a new, globally extinct genus and species of gibbon, Junzi imperialis, described from a partial cranium and mandible from a ~2200- to 2300-year-old tomb from Shaanxi, China. Junzi can be differentiated from extant hylobatid genera and the extinct Quaternary gibbon Bunopithecus by using univariate and multivariate analyses of craniodental morphometric data. Primates are poorly represented in the Chinese Quaternary fossil record, but historical accounts suggest that China may have contained an endemic ape radiation that has only recently disappeared.

Quaternary vertebrate faunas from Sumba, Indonesia: Implications for Wallacean biogeography and evolution

Historical patterns of diversity, biogeography and faunal turnover remain poorly understood for Wallacea, the biologically and geologically complex island region between the Asian and Australian continental shelves. A distinctive Quaternary vertebrate fauna containing the small-bodied hominin Homo floresiensis, pygmy Stegodon proboscideans, varanids and giant murids has been described from Flores, but Quaternary faunas are poorly known from most other Lesser Sunda Islands. We report the discovery of extensive new fossil vertebrate collections from Pleistocene and Holocene deposits on Sumba, a large Wallacean island situated less than 50 km south of Flores. A fossil assemblage recovered from a Pleistocene deposit at Lewapaku in the interior highlands of Sumba, which may be close to 1 million years old, contains a series of skeletal elements of a very small Stegodon referable to S. sumbaensis, a tooth attributable to Varanus komodoensis, and fragmentary remains of unidentified giant murids. Holocene cave deposits at Mahaniwa dated to approximately 2000–3500 BP yielded extensive material of two new genera of endemic large-bodied murids, as well as fossils of an extinct frugivorous varanid. This new baseline for reconstructing Wallacean faunal histories reveals that Sumbas Quaternary vertebrate fauna, although phylogenetically distinctive, was comparable in diversity and composition to the Quaternary fauna of Flores, suggesting that similar assemblages may have characterized Quaternary terrestrial ecosystems on many or all of the larger Lesser Sunda Islands.

Unexpected diversity within the extinct elephant birds (Aves: Aepyornithidae) and a new identity for the world's largest bird

Madagascars now-extinct radiation of large-bodied ratites, the elephant birds (Aepyornithidae), has been subject to little modern research compared to the islands mammalian megafauna and other Late Quaternary giant birds. The familys convoluted and conflicting taxonomic history has hindered accurate interpretation of morphological diversity and has restricted modern research into their evolutionary history, biogeography and ecology. We present a new quantitative analysis of patterns of morphological diversity of aepyornithid skeletal elements, including material from all major global collections of aepyornithid skeletal remains, and constituting the first taxonomic reassessment of the family for over 50 years. Linear morphometric data collected from appendicular limb elements, and including nearly all type specimens, were examined using multivariate cluster analysis and the Bayesian information criterion, and with estimation of missing data using multiple imputation and expectation maximization algorithms. These analyses recover three distinct skeletal morphotypes within the Aepyornithidae. Two of these morphotypes are associated with the type specimens of the existing genera Mullerornis and Aepyornis, and represent small-bodied and medium-bodied aepyornithids, respectively. Aepyornis contains two distinct morphometric subgroups, which are identified as the largely allopatric species A. hildebrandti and A. maximus. The third morphotype, which has not previously been recognized as a distinct genus, is described as the novel taxon Vorombe titan. Vorombe represents the largest-bodied aepyornithid and is the worlds largest bird, with a mean body mass of almost 650 kg. This new taxonomic framework for the Aepyornithidae provides an important new baseline for future studies of avian evolution and the Quaternary ecology of Madagascar.