International Journal of Molecular Evolution and Biodiversity 2024, Vol.14, No.4, 174-185 http://ecoevopublisher.com/index.php/ijmeb 177 4 Evolutionary Trends in Beetle Morphology 4.1 Early Beetle Morphology The earliest known beetle fossils date back to the late Carboniferous period, marking the origin of Coleoptera. These early beetles exhibited a range of primitive features that have since evolved significantly. For instance, the fossil record of the suborder Myxophaga, such as the mid-Cretaceous Lepiceratus ankylosaurus, reveals fine morphological structures that have remained relatively unchanged over millions of years, indicating a high degree of morphological stasis in some lineages (Jałoszyński et al., 2020). Early beetles like Leehermania prorova from the Triassic period, initially thought to be part of the Staphylinidae family, have been reclassified into the Myxophaga suborder, highlighting the complexity and diversity of early beetle forms (Fikáček et al., 2020). In comparison to modern beetles, these ancient specimens show both similarities and differences. Modern beetles have diversified into numerous families and exhibit a wide range of specialized adaptations. For example, the reduction of antennomeres from the ancestral 11 to fewer segments in some lineages, such as the Lepiceridae, demonstrates a trend towards morphological simplification over time. Additionally, the presence of robust and structured hind legs in some Mesozoic scarab beetles, like Antiqusolidus maculatus (Figure 2) (Lu et al., 2023), suggests early adaptations for specific behaviors such as springing and fighting, which are less common in contemporary beetles. Figure 2 Photographs and line drawings of Antiqusolidus maculatus (Adopted from Lu et al., 2023) Image caption: (a,c) General habitus, dorsal view; arrows indicate structured hind legs, scale 10 mm. (b,d) General habitus, ventral view, scale 10 mm. (e) Left foreleg, dorsal view, scale 1 mm. (f) Right hind leg, dorsal view, scale 2 mm. (g) Anterior part of head, dorsal view, scale 1 mm. (h) Pronotum, scale 2 mm. (i) Right mesotarsi, ventral view, rectangle indicate claws, scale 1 mm. (j) Left hind leg, dorsal view, scale 2 mm. (k) Claws of right mesotarsi, scale 1 mm (Adopted from Lu et al., 2023)
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