This is Mazon Monday post #337.  What’s your favorite Mazon Creek fossil?  Tell us at esconi.info@gmail.com.

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I had a chance to catch up with Jack Wittry at the Field Museum this weekend. He mentioned that he had tracked down the insect whose name we first encountered at Tom Testa Day at the Carbon Hill School Museum back in June. At the time, Jack wasn’t sure whether Carbohymen testai was actually a valid name. After doing some digging, he not only confirmed the species, but also located the actual fossil in the Field Museum’s collections!

Carbohymen testai was described by Martina Pecharová and Jakub Prokop, both of the Department of Zoology at Charles University in the Czech Republic, in their 2018 paper, “The morphology of mouthparts, wings and genitalia of Paleozoic insect families Protohymenidae and Scytohymenidae reveals new details and supposed function.”

C. testai is classified in the family Protohymenidae and belongs to the extinct insect order Megasecoptera. Megasecopterans were part of the larger group Palaeodictyopterida, an ancient lineage of insects that vanished from the fossil record at the end of the Permian Period.

Only a single specimen of C. testai is known. This tiny fossil, collected from Pit 11 by Tom Testa, became the holotype… the specimen upon which the species was formally described.

Abstract

Megasecoptera is an extinct group of insects with specialized rostrum-like mouthparts, which is a synapomorphy shared with all members of the Late Paleozoic Palaeodictyopterida, and markedly slender wings that are unable to flex backwards. Here we describe the close up morphology of Protohymenidae and Scytohymenidae and uncover new aspects of the endoskeleton (tentorium) of the head, structure of the mouthparts with discernible proximal part of stylets controlled by muscles, surface of compound eyes that consist of a hexagonal pattern of large facets, structure and microstructures on the wings and reconstruct male and female external genitalia using ESEM and light stereomicroscopy. Furthermore, we describe Protohymen novokshonovi sp. n. based on an exceptionally well preserved fossil from the early Permian at Tshekarda in Russia, which shows crucial details, and the earliest species of Protohymenidae, Carbohymen testai gen. et sp. n. from a late Carboniferous siderite nodule at Mazon Creek in Illinois, USA. Our comparative study confirmed a set of structural and microstructural details on their wings, such as the composite anterior wing margin, development of an apical cell and the previously unknown external genitalia. Based on the results and comparison of homologous structures known primarily for extant relatives, such as mayflies and dragonflies, we outline for the first time the function of the mouthparts, in particular, the stylets, structure of the tentorium, vision provided by large hexagonal ommatidia and male copulatory structures bearing curved claspers for holding a female during copulation and penial lobes with seminal grooves.

Photos