Boletín de la Sociedad Geológica Mexicana Volumen 74, núm. 2, A150322, 2022 http://dx.doi.org/10.18268/BSGM2022v74n2a150322

A small beetle larva preserved in 23-million-year-old Mexican amber: possible first fossil record of an immature variegated mud-loving beetle

Una pequeña larva de escarabajo conservada en ámbar mexicano de 23 millones de años: primer posible registro fósil de un ejemplar inmaduro de escarabajo abigarrado del lodo

Ana Zippel¹, Carolin Haug^1,2, Joshua Gauweiler^1,3, Marie K. Hörnig³, Gideon T. Haug¹, Joachim T. Haug^1,2,*

¹ Biocenter, Ludwig-Maximilians-Universität München (LMU Munich), Großhaderner Str. 2, 82152 Planegg-Martinsried, Germany.

² GeoBio-Center at Ludwig-Maximilians-Universität München (LMU Munich), Richard-Wagner-Str. 10, 80333 München, Germany.

³ Zoological Institute and Museum, Cytology and Evolutionary Biology, Soldmannstr, University of Greifswald, 23, 17489 Greifswald, Germany.

* Corresponding author: (J.T. Haug) This email address is being protected from spambots. You need JavaScript enabled to view it.

How to cite this article:

Zippel, A., Haug, C., Gauweiler, J., Hörnig, M.K., Haug, G.T., Haug, J.T., 2022, A small beetle larva preserved in 23-million-year-old Mexican amber: possible first fossil record of an immature variegated mud-loving beetle: Boletín de la Sociedad Geológica Mexicana, 74 (2), A150322. http://dx.doi.org/10.18268/BSGM2022v74n2a150322

Manuscript received: February 1, 2022; Corrected manuscript received: March 10, 2022; Manuscript accepted: March 15, 2022

ABSTRACT

Beetles occupy a vast amount of different ecological roles in both terrestrial and freshwater ecosystems. The often very specialised morphology of the adults can frequently be associated with their specific roles. Yet, the ecologically independent larvae of the same species are often unknown; this applies even more so to fossils. Here we report a new fossil beetle larva preserved in Mexican amber. The beetle larva was documented via digital microscopy and X-ray micro-computed tomography (X-ray µCT). The observed features, especially of the trunk, but also the maxillo-labial complex as well as the moulting suture of the head capsule are reminiscent to those of larvae of variegated mud-loving beetles, Heteroceridae. The trunk end is tube-like and protrudes ventro-terminally from abdomen segment 9. While present in other beetle lineages, this morphology is in these lineages, for example, not combined with a simple moulting suture. Some features potentially further supporting an interpretation as a larva of Heteroceridae are not accessible. The interpretation yet remains the most compatible one. Assuming a similar life style to modern larvae of Heteroceridae indicates an original lifestyle associated with running waters, but not within these. Heteroceridae is an ingroup of Byrrhoidea; the fossil record of byrrhoidean larvae is still very scarce. The new fossil hence adds a rare ecological function to the Miocene amber fauna, representing the first fossil record of a larva of Heteroceridae and expanding the fossil record of byrrhoidean larvae.

Keywords: Heteroceridae, Byrrhoidea, Chiapas amber, Miocene, running waters.