Giants and dwarves: Reconstructing the evolution of size and life histories within Myriapoda

• Applicants: Professor Dr. Joachim Tobias Haug; Professor Dr. Roland Melzer
• Subject Area: Geology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 516824140

Representatives of the group Myriapoda, i.e. centipedes, millipedes, and their relatives, are generally known as rather small animals living in the soil and leaf litter. Even though the group Myriapoda comprises far less species than, for example, the group Insecta, centipedes and millipedes are important components of the modern fauna. They fulfil important ecological roles, for example, as decomposers or impressive predators to name just two examples. While the majority of modern representatives of Myriapoda has a body size within the millimetre range, much larger ones live in the tropics, with a maximum length of slightly more than 30 centimetres. Hence, it is even more astonishing that during the late Palaeozoic, especially in the Carboniferous (ca. 359–299 million years ago), fossil representatives of this group reached body sizes of up to two metres. Of special interest in the context of body size in Myriapoda is the comparison of the largest representatives, the exclusively fossil representatives of Arthropleuridea, and the smallest representatives, bristly millipedes (Polyxenida). The latter occur both in the modern fauna and as fossils preserved in ambers of different ages (from 130 to 15 million years ago). Despite their significant size difference, both groups have been suggested to be sister groups, hence apparently strong evolutionary changes in body size occurred. We explore two aspects: the support for a sistergroup relationship between Arthropleuridea and Polyxenida, and the size changes of bristly millipedes through time. A challenge in the comparison of size in fossils is that small representatives could simply be immatures. Therefore, we will include those stages into our comparisons which do not yet have the full segment number. Such immature stages can be recognised for modern and also for fossil representatives of certain lineages (e.g. Lithobiomorpha or Polyxenidae) and with this be identified to distinct stages. When these stages are compared, the ontogenetic variation, i.e. the variation during individual development, can be corrected. The investigations and analyses of these finds from 130 million years ago to today will provide for a better understanding of the changes in ecological functions through time.

• DFG Programme: Research Grants