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1. Testing Equid Body Mass Estimate Equations on Modern Zebras—With Implications to Understanding the Relationship of Body Size, Diet, and Habitats of Equus in the Pleistocene of Europe

   https://doi.org/doi:10.3389/fevo.2021.622412  

   Saarinen, J. (February 2021, Frontiers)

   null (Ed.)

   The monodactyl horses of the genus Equus originated in North America during the Pliocene, and from the beginning of the Pleistocene, they have been an essential part of the large ungulate communities of Europe, North America and Africa. Understanding how body size of Equus species evolved and varied in relation to changes in environments and diet thus forms an important part of understanding the dynamics of ungulate body size variation in relation to Pleistocene paleoenvironmental changes. Here we test previously published body mass estimation equations for the family Equidae by investigating how accurately different skeletal and dental measurements estimate the mean body mass (and body mass range) reported for extant Grevy’s zebra (Equus grevyi) and Burchell’s zebra (Equus quagga). Based on these tests and information on how frequently skeletal elements occur in the fossil record, we construct a hierarchy of best practices for the selection of body mass estimation equations in Equus. As a case study, we explore body size variation in Pleistocene European Equus paleopopulations in relation to diet and vegetation structure in their paleoenvironments. We show a relationship between diet and body size in Equus: very large-sized species tend to have more browse-dominated diets than small and medium-sized species, and paleovegetation proxies indicate on average more open and grass-rich paleoenvironments for small-sized, grazing species of Equus. When more than one species of Equus co-occur sympatrically, the larger species tend to be less abundant and have more browse-dominated diets than the smaller species. We suggest that body size variation in Pleistocene Equus was driven by a combined effect of resource quality and availability, partitioning of habitats and resources between species, and the effect of environmental openness and group size on the body size of individuals 

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2. Evolution of Old World Equus and origin of the zebra-ass clade

   https://doi.org/doi:org/10.1038/s41598-021-89440-9  

   Cirilli, O. (May 2021, Scientific reports)

   null (Ed.)

   Study of the evolution of the genus Equus utilizing fossil and extant species. Results show that Equus is a clade and that the genera Plesippus (North America) and Allohippus (Eurasia and Africa) are invalid. The study provides new insights into the relationships of extant zebras and asses to Plio-Pleistocene member of the Equus clade. 

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3. Equus cf. livenzovensis from Montopoli, Italy (early Pleistocene; MN16b; ca. 2.6 Ma)

   https://doi.org/10.4435/BSPI.2018.13  

   Bernor, R.L. (October 2018, Bollettino della Società paleontologica italiana)

   We report here the occurrence and metric characteristics of a large species of Equus from Montopoli (Tuscany, Italy) correlated with the middle Villafranchian, 2.6 Ma (early Pleistocene). This species co-occurs with a rare “Hipparion” sp. at Montopoli. We compare the Montopoli Equus cf. livenzovensis with a large suite of extant Equus including zebras, asses and a large suite of fossil Equus using bivariate and log10 ratio analyses of anterior and posterior 1st phalanges III. Our comparisons show that Montopoli anterior and posterior 1st phalanges III are larger than in living zebras and asses and comparable in size and proportions to the early Pleistocene large Chinese species Equus eisenmannae and late Pleistocene Rancho La Brean Equus occidentale. Equus livenzovensis was a larger species than Equus stenonis and Equus stehlini. Equus cf. livenzovensis is not represented as far as we know by skulls and dentitions in the Italian Villafranchian record. 

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4. Target Deformation of the Equus stenonis Holotype Skull: A Virtual Reconstruction

   https://doi.org/10.3389/feart.2020.00247  

   Cirilli, O. (June 2020, Frontiers)

   Pandolfi, L. (Ed.)

   Equus stenonis is one of the most prevalent European Pleistocene fossil horses. It is believed to be the possible ancestor of all Old World Early Pleistocene Equus, extant zebras and asses, and as such provides insights into Equus evolution and its biogeography and paleoecology. The Equus stenonis holotype skull (IGF560) was first described by Igino Cocchi in 1867, from the Early Pleistocene locality of Terranuova (Upper Valdarno basin, Italy). IGF560 is a nearly complete, although medio-laterally crushed and badly compressed skull. Here we provide the first application of a new virtual reconstruction protocol, termed Target Deformation, to the Equus stenonis holotype. The protocol extends beyond classic retrodeformation by using target specimens as a guide for the virtual reconstruction. The targets used as a reference are two fragmentary, yet well-preserved E. stenonis skulls, coming from Olivola (Italy; IGF11023) and Dmanisi (Georgia; Dm 5/154.3/4.A4.5), both Early Pleistocene in age. These two specimens do not display any major deformation, but preserve different, only slightly overlapping portions of the skull. The virtual reconstruction protocol we carried out has shown its feasibility, by producing two 3D models whose final morphology is perfectly congruent with the natural variability of a comparative sample of E. stenonis specimens. This study shows the potential of using even broken or otherwise fragmentary specimens to guide retrodeformation in badly distorted and damaged specimens. The application of Target Deformation will allow us to increase the availability of comparative specimens in studies of fossil species morphology and evolution, as well as to the study of taphonomic processes. 

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5. Taxonomic revision of the Malagasy Aphaenogaster swammerdami group (Hymenoptera: Formicidae)

   https://doi.org/10.7717/peerj.10900  

   Csősz, Sandor; Loss, Ana C.; Fisher, Brian L. (January 2021, PeerJ)

   null (Ed.)

   Background Madagascar is famous for its extremely rich biodiversity; the island harbors predominantly endemic and threatened communities meriting special attention from biodiversity scientists. Continuing ongoing efforts to inventory the Malagasy ant fauna, we revise the species currently placed in the myrmicine genus Aphaenogaster Mayr. One species described from Madagascar, Aphaenogaster friederichsi Forel, is synonymized with the Palearctic A. subterranea Latreille syn. nov. This species is considered neither native to Madagascar nor established in the region. This revision focuses on the balance of species in the A. swammerdami group which are all endemic to Madagascar. Methods The diversity of the Malagasy Aphaenogaster fauna was assessed via application of multiple lines of evidence involving quantitative morphometric, qualitative morphological, and DNA sequence data. (1) Morphometric investigation was based on hypothesis-free Nest Centroid clustering (NC-clustering) combined with PArtitioning based on Recursive Thresholding (PART) to estimate the number of morphological clusters and determine the most probable boundaries between them. This protocol provides a repeatable and testable approach to find patterns in continuous morphometric data. Species boundaries and the reliability of morphological clusters recognized by these exploratory analyses were tested via confirmatory Linear Discriminant Analysis (LDA). (2) Qualitative, external morphological characteristics (e.g., shape, coloration patterns, setae number) were subjectively evaluated in order to create a priori grouping hypotheses, and confirm and improve species delimitation. (3) Species delimitation analyses based on mitochondrial DNA sequences from cytochrome oxidase I (COI) gene fragments were carried out to test the putative species previously delimited by morphological and morphometric analyses. Results Five species can be inferred based on the integrated evaluation of multiple lines of evidence; of these, three are new to science: Aphaenogaster bressleri sp. n ., A. gonacantha (Emery, 1899), A. makay sp. n. , A. sahafina sp. n. , and A. swammerdami Forel, 1886. In addition, three new synonymies were found for A. swammerdami Forel, 1886 ( A. swammerdami clara Santschi, 1915 syn. n. , A. swammerdami curta Forel, 1891 syn. n. and A. swammerdami spinipes Santschi, 1911 syn. n. ). Descriptions and redefinitions for each taxon and an identification key for their worker castes using qualitative traits and morphometric data are given. Geographic maps depicting species distributions and biological information regarding nesting habits for the species are also provided. 

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