idw – Informationsdienst Wissenschaft

Nachrichten, Termine, Experten

Grafik: idw-Logo
Science Video Project
idw-Abo

idw-News App:

AppStore

Google Play Store



Instanz:
Teilen: 
24.03.2020 09:51

Small horses got smaller, big tapirs got bigger 47 million years ago

Dr. Karl Guido Rijkhoek Hochschulkommunikation
Eberhard Karls Universität Tübingen

    Researchers open a window onto ancient mammal evolution using fossils from Germany

    The former coalfield of Geiseltal in eastern Germany has yielded large numbers of exceptionally preserved fossil animals, giving palaeontologists a unique window into the evolution of mammals 47 million years ago. At that time – the middle Eocene – the Earth was much warmer and the area was a swampy subtropical forest whose inhabitants included ancestors of the horse, ancient tapirs, large terrestrial crocodiles, as well as giant tortoises, lizards and ground-dwelling birds. So rich are the Geiseltal finds that they give researchers an unprecedented high-resolution picture of evolutionary dynamics at the population level.

    A team led by Dr Márton Rabi from the University of Tübingen and the Martin Luther University Halle-Wittenberg (MLU) has shown that the body size of two species of mammals developed in opposite directions. The study, published in Scientific Reports, was carried out with Simon Ring and Professor Hervé Bocherens at the Senckenberg Centre for Human Evolution and Palaeoenvironment and the University of Tübingen in cooperation with Dr Oliver Wings from the MLU.

    “We were initially interested in the evolution of the ancient horses, which were about the size of a Labrador dog. These animals are particularly abundant in the Geiseltal fossil record,” Rabi says. Researchers initially believed they had several species of early horse. “However, we found that here, there was only one species, whose body size shrank significantly with time,” Rabi explains. The team wanted to test whether this body size shift was climate-induced, since past global warming caused body-size reduction in ancient mammals.

    Carbon and oxygen isotope studies on fossil teeth provided the scientists with information about the local middle Eocene climate. “They indicate a humid tropical climate. However, we didn’t find any evidence for climatic changes in Geiseltal over the period investigated,” says Bocherens. To further test the data, the team sought to discover whether the dwarfing process was unique to the horses. For comparison, they examined the evolution of the tapir ancestor called Lophiodon. “We had reason to question the Geiseltal’s constant-climate data; so we expected that other mammals would show the same body-size trends as the horses,” Simon Ring explains. In a surprising result, the tapirs – also a single species – revealed the opposite trend. They grew larger instead of shrinking. While the ancestors of the horse shrank from an average body weight of 39 kilograms to around 26 kilograms over about a million years, the tapirs increased from 124 kilograms to an average body weight of 223 kilograms.

    Differing survival strategies

    “All the data indicate that the body size of the horses and tapirs developed differently not because of the climate, but because of different life cycles,” explains Bocherens. Small animals reproduce faster and die younger: Relative to their size, they don’t have to eat as much to maintain their body mass and can devote more resources to having young. Larger animals live longer and have lower reproduction rates. They have to eat more and therefore have fewer resources for reproduction – but, being large, face fewer predators and can range further to get better food. That extends their lives and gives them more time to breed. The Geiseltal tapirs and the horses therefore likely maximized the different advantages of their respective life cycle strategies, which caused divergent body size evolution.

    Exceptional fossil deposits

    The Geiseltal fossil site is located in the eastern state of Saxony-Anhalt. In the course of open-cast brown coal mining between 1933 and 1993, tens of thousands of fossil specimens of more than one hundred species were discovered there. Many were the ancestors of modern vertebrates. “The Geiseltal is as important a fossil site as the Messel Pit near Darmstadt, which is a UNESCO World Heritage Site,” says Dr. Rabi. “But because the Geiseltal collection was hardly accessible during East German times, it kind of went off the radar.”


    Wissenschaftliche Ansprechpartner:

    Dr. Márton Rabi
    University of Tübingen, Department of Geoscience
    Martin-Luther University Halle-Wittenberg, Central Natural Science Collections
    iszkenderun[at]gmail.com

    Prof. Dr. Hervé Bocherens
    University of Tübingen
    Faculty of Science - Biogeology
    Senckenberg Centre for Human Evolution and Palaeoenvironment (HEP)
    Phone +49 7071 29-76988
    herve.bocherens[at]uni-tuebingen.de


    Originalpublikation:

    Simon J. Ring, Hervé Bocherens, Oliver Wings & Márton Rabi: Divergent mammalian body size in a stable Eocene greenhouse climate. Scientific Reports, (2020) 10:3987, https://doi.org/10.1038/s41598-020-60379-7


    Bilder

    Ecosystem of the Geiseltal fossil locality with the horse-ancestor Propalaeotherium (left), the ancient tapir Lophiodon (middle), and a young terrestrial crocodile Bergisuchus (background).
    Ecosystem of the Geiseltal fossil locality with the horse-ancestor Propalaeotherium (left), the anci ...
    Artwork by Márton Szabó
    None

    Exceptionally-well fossilized skeletons of the ancient tapir Lophiodon (top) and the ancestral horse Propalaeotherium (bottom) from the middle Eocene Geiseltal locality (Germany, Saxony-Anhalt).
    Exceptionally-well fossilized skeletons of the ancient tapir Lophiodon (top) and the ancestral horse ...
    Photo by Oliver Wings
    None


    Merkmale dieser Pressemitteilung:
    Journalisten, jedermann
    Biologie, Geowissenschaften
    überregional
    Forschungsergebnisse, Wissenschaftliche Publikationen
    Englisch


     

    Ecosystem of the Geiseltal fossil locality with the horse-ancestor Propalaeotherium (left), the ancient tapir Lophiodon (middle), and a young terrestrial crocodile Bergisuchus (background).


    Zum Download

    x

    Exceptionally-well fossilized skeletons of the ancient tapir Lophiodon (top) and the ancestral horse Propalaeotherium (bottom) from the middle Eocene Geiseltal locality (Germany, Saxony-Anhalt).


    Zum Download

    x

    Hilfe

    Die Suche / Erweiterte Suche im idw-Archiv
    Verknüpfungen

    Sie können Suchbegriffe mit und, oder und / oder nicht verknüpfen, z. B. Philo nicht logie.

    Klammern

    Verknüpfungen können Sie mit Klammern voneinander trennen, z. B. (Philo nicht logie) oder (Psycho und logie).

    Wortgruppen

    Zusammenhängende Worte werden als Wortgruppe gesucht, wenn Sie sie in Anführungsstriche setzen, z. B. „Bundesrepublik Deutschland“.

    Auswahlkriterien

    Die Erweiterte Suche können Sie auch nutzen, ohne Suchbegriffe einzugeben. Sie orientiert sich dann an den Kriterien, die Sie ausgewählt haben (z. B. nach dem Land oder dem Sachgebiet).

    Haben Sie in einer Kategorie kein Kriterium ausgewählt, wird die gesamte Kategorie durchsucht (z.B. alle Sachgebiete oder alle Länder).