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I donated the below specimen to the Field Museum of Natural History. It is identified as an Esconichthys apopyris. Work is being done on redefining/solidifying the categorization of this species, and a professional helped facilitate my donation to the museum. There are details on this specimen such as a yolk sac and I look forward to hearing if there are internal details such as vascular structures. I feel like I can see them but I am excited to open it up to professional analysis through donation to a research institution.

The Mazon Creek Deposit is known for many enigmatic creatures. Esconichthys is one of them. The animal has a tadpole shaped body with a usually well preserved pair of eyes. Some specimens preserve 2 pairs of long external gills. Muscle segments called myomeres are sometimes present on laterally preserved specimens. What makes it unusual is that it does not have paired fins. It was originally suggested that Esconichthys may be a larval lungfish or possibly an amphibian. Later studies have stated this is unlikely without offering an alternative placement. Due to the presence of external gills, it is believed that these are likely a larval stage. The largest specimens known can reach almost 8 centimeters. Early collectors referred to these animals as blades or grasshoppers based on their general shape. They are the most common vertebrate found in the Mazon Creek Deposit. Specimens are only known from the marine (Essex) portion. Esconichthys was named to recognize the Earth Science Club Of Illinois (ESCONI).